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Sample records for dc plasma nitriding

  1. Surface modification of 17-4PH stainless steel by DC plasma nitriding and titanium nitride film duplex treatment

    NASA Astrophysics Data System (ADS)

    Qi, F.; Leng, Y. X.; Huang, N.; Bai, B.; Zhang, P. Ch.

    2007-04-01

    17-4PH stainless steel was modified by direct current (DC) plasma nitriding and titanium nitride film duplex treatment in this study. The microstructure, wear resistance and corrosion resistance were characterized by X-ray diffraction (XRD), pin-on-disk tribological test and polarization experiment. The results revealed that the DC plasma nitriding pretreatment was in favor of improving properties of titanium nitride film. The corrosion resistance and wear resistance of duplex treatment specimen was more superior to that of only coated titanium nitride film.

  2. Investigation of plasma parameters in an active screen cage-pulsed dc plasma used for plasma nitriding

    NASA Astrophysics Data System (ADS)

    Naeem, M.; Khattak, Z. I.; Zaka-ul-Islam, M.; Shabir, S.; Khan, A. W.; Zakaullah, M.

    2014-11-01

    Active screen cage-pulsed dc plasmas are widely used in the material processing applications such as plasma nitriding, carburizing and nitrocarburizing. Specifically for plasma nitriding applications, a H2-N2 mixture is used. In this article, a study of the electron number density (ne), atomic nitrogen density ([N]), electron temperature ? and the excitation temperature ? is reported in the presence of an active screen cage-pulsed dc plasma. The ne and ? are determined here by a triple Langmuir probe, while [N] and ? are estimated by optical emission spectroscopy (OES). The two temperatures and their ratio ? are compared for different input parameters (such as applied power, gas pressure and H2 percentage). This study is useful in active screen cage plasma nitriding applications where only few plasma diagnostic measurements have been reported.

  3. Low-Temperature Nitriding of Pure Titanium by using Hollow Cathode RF-DC Plasma

    NASA Astrophysics Data System (ADS)

    Windajanti, J. M.; S, D. J. Djoko H.; Abdurrouf

    2017-05-01

    Pure titanium is widely used for the structures and mechanical parts due to its high strength, low density, and high corrosion resistance. Unfortunately, titanium products suffer from low hardness and low wear resistance. Titanium’s surface can be modified by nitriding process to overcome such problems, which is commonly conducted at high temperature. Here, we report the low-temperature plasma nitriding process, where pure titanium was utilized by high-density RF-DC plasma combined with hollow cathode device. To this end, a pure titanium plate was set inside a hollow tube placed on the cathode plate. After heating to 450 °C, a pre-sputtering process was conducted for 1 hour to remove the oxide layer and activate the surface for nitriding. Plasma nitriding using N2/H2 gasses was performed in 4 and 8 hours with the RF voltage of 250 V, DC bias of -500 to -600 V, and gas pressure of 75 to 30 Pa. To study the nitriding mechanism as well as the role of hollow cathode, the nitrided specimen was characterized by SEM, EDX, XRD, and micro-hardness equipment. The TiN compound was obtained with the diffusion zone of nitrogen until 5 μm thickness for 4 hours nitriding process, and 8 μm for 8 hours process. The average hardness also increased from 300 HV in the untreated specimen to 624 HV and 792 HV for 4 and 8 hours nitriding, respectively.

  4. a Novel Method for Improving Plasma Nitriding Efficiency: Pre-Magnetization by DC Magnetic Field

    NASA Astrophysics Data System (ADS)

    Kovaci, Halim; Yetim, Ali Fatih; Bozkurt, Yusuf Burak; Çelik, Ayhan

    2017-06-01

    In this study, a novel pre-magnetization process, which enables easy diffusion of nitrogen, was used to enhance plasma nitriding efficiency. Firstly, magnetic fields with intensities of 1500G and 2500G were applied to the untreated samples before nitriding. After the pre-magnetization, the untreated and pre-magnetized samples were plasma nitrided for 4h in a gas mixture of 50% N2-50% H2 at 500∘C and 600∘C. The structural, mechanical and morphological properties of samples were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), microhardness tester and surface tension meter. It was observed that pre-magnetization increased the surface energy of the samples. Therefore, both compound and diffusion layer thicknesses increased with pre-magnetization process before nitriding treatment. As modified layer thickness increased, higher surface hardness values were obtained.

  5. Microstructure and dry-sliding wear properties of DC plasma nitrided 17-4 PH stainless steel

    NASA Astrophysics Data System (ADS)

    Li, Gui-jiang; Wang, Jun; Li, Cong; Peng, Qian; Gao, Jian; Shen, Bao-luo

    2008-05-01

    An attempt that the precipitation hardening steel 17-4PH was conducted by DC plasma nitriding (DCPN) is made to develop a kind of candidate material for nuclear reactor. Nitriding process performed at temperature ⩽ 400 °C takes effect on creation of the layers composed of S-phase (expanded austenite) and αN‧ (expanded martensite). Up to the temperature of 420 °C, the S-phase peaks disappear due to the transformation occurrence (S-phase → αN‧ + CrN). For the samples nitrided at temperature ⩾ 450 °C, no evidence of αN‧ is found owing to a precipitation (αN‧ → α +CrN) taking place. For the 480 °C/4 h treated sample, it is the surface microhardness that plays the lead role in the wear rate reduction but the surface roughness; while for the 400 °C/4 h treated sample, it is both of the surface roughness and the S-phase formation. Dry sliding wear of the untreated 17-4PH is mainly characterized by strong adhesion, abrasion and oxidation mechanism. Samples nitrided at 400 °C which is dominated by slight abrasion and plastic deformation exhibit the best dry sliding wear resistance compared to the samples nitrided at other temperatures.

  6. Titanium nitride plasma-chemical synthesis with titanium tetrachloride raw material in the DC plasma-arc reactor

    NASA Astrophysics Data System (ADS)

    Kirpichev, D. E.; Sinaiskiy, M. A.; Samokhin, A. V.; Alexeev, N. V.

    2017-04-01

    The possibility of plasmochemical synthesis of titanium nitride is demonstrated in the paper. Results of the thermodynamic analysis of TiCl4 - H2 - N2 system are presented; key parameters of TiN synthesis process are calculated. The influence of parameters of plasma-chemical titanium nitride synthesis process in the reactor with an arc plasmatron on characteristics on the produced powders is experimentally investigated. Structure, chemical composition and morphology dependencies on plasma jet enthalpy, stoichiometric excess of hydrogen and nitrogen in a plasma jet are determined.

  7. Improvement in nano-hardness and corrosion resistance of low carbon steel by plasma nitriding with negative DC bias voltage

    NASA Astrophysics Data System (ADS)

    Alim, Mohamed Mounes; Saoula, Nadia; Tadjine, Rabah; Hadj-Larbi, Fayçal; Keffous, Aissa; Kechouane, Mohamed

    2016-10-01

    In this work, we study the effect of plasma nitriding on nano-hardness and corrosion resistance of low carbon steel samples. The plasma was generated through a radio-frequency inductively coupled plasma source. The substrate temperature increased (by the self-induced heating mechanism) with the treatment time for increasing negative bias voltages. X-rays diffraction analysis revealed the formation of nitride phases (ɛ-Fe2-3N and γ'-Fe4N) in the compound layer of the treated samples. A phase transition occurred from 3.5 kV to 4.0 kV and was accompanied by an increase in the volume fraction of the γ'-Fe4N phase and a decrease in that of the ɛ-Fe2-3N phase. Auger electron spectroscopy revealed a deep diffusion of the implanted nitrogen beyond 320 nm. The nano-hardness increased by ~400% for the nitrogen-implanted samples compared to the untreated state, the nitride phases are believed to participate to the hardening. Potentiodynamic polarization measurements revealed that the plasma nitriding has improved the corrosion resistance behavior of the material. When compared to the untreated state, the sample processed at 4.0 kV exhibits a shift of +500 mV and a reduction to 3% in its corrosion current. These results were obtained for relatively low bias voltages and short treatment time (2 h).

  8. Analysis of plasma nitrided steels

    NASA Technical Reports Server (NTRS)

    Salik, J.; Ferrante, J.; Honecy, F.; Hoffman, R., Jr.

    1987-01-01

    The analysis of plasma nitrided steels can be divided to two main categories - structural and chemical. Structural analysis can provide information not only on the hardening mechanisms but also on the fundamental processes involved. Chemical analysis can be used to study the kinetics for the nitriding process and its mechanisms. In this paper preliminary results obtained by several techniques of both categories are presented and the applicability of those techniques to the analysis of plasma-nitrided steels is discussed.

  9. Validity of "sputtering and re-condensation" model in active screen cage plasma nitriding process

    NASA Astrophysics Data System (ADS)

    Saeed, A.; Khan, A. W.; Jan, F.; Abrar, M.; Khalid, M.; Zakaullah, M.

    2013-05-01

    The validity of "sputtering and re-condensation" model in active screen plasma nitriding for nitrogen mass transfer mechanism is investigated. The dominant species including NH, Fe-I, N2+, N-I and N2 along with Hα and Hβ lines are observed in the optical emission spectroscopy (OES) analysis. Active screen cage and dc plasma nitriding of AISI 316 stainless steel as function of treatment time is also investigated. The structure and phases composition of the nitrided layer is studied by X-ray diffraction (XRD). Surface morphology is studied by scanning electron microscopy (SEM) and hardness profile is obtained by Vicker's microhardness tester. Increasing trend in microhardness is observed in both cases but the increase in active screen plasma nitriding is about 3 times greater than that achieved by dc plasma nitriding. On the basis of metallurgical and OES observations the use of "sputtering and re-condensation" model in active screen plasma nitriding is tested.

  10. Analysis of plasma-nitrided steels

    NASA Technical Reports Server (NTRS)

    Salik, J.; Ferrante, J.; Honecy, F.; Hoffman, R., Jr.

    1986-01-01

    The analysis of plasma nitrided steels can be divided to two main categories - structural and chemical. Structural analysis can provide information not only on the hardening mechanisms but also on the fundamental processes involved. Chemical analysis can be used to study the kinetics for the nitriding process and its mechanisms. In this paper preliminary results obtained by several techniques of both categories are presented and the applicability of those techniques to the analysis of plasma-nitrided steels is discussed.

  11. Nitriding of titanium and its alloys by N2, NH3 or mixtures of N2 + H2 in a dc arc plasma at low pressures ( or = to torr)

    NASA Technical Reports Server (NTRS)

    Avni, R.

    1984-01-01

    The dc glow discharges in different gas mixtures of Ar + N2, Ar + NH3 or Ar + N2 + H2 result in the surface nitriding of Ti metal and its alloy (Ti6Al4V). Various gas mixtures were used in order to establish the main active species governing the nitriding process, i.e., N, N2, NH, or NH2 as excited or ionized particles. The dc discharge was sampled and analyzed by quadruple mass spectrometry (QPMS) and optical emission spectroscopy (OES), and the nitrided samples were analyzed by scanning electron microscopy (SEM) with an EDAX attachment, microhardness, and Fourier transform infrared reflectance spectrometry (FTIR). It was found that the excited and ionized nitrogen and hydrogen atoms are the main species responsible for the nitriding process in a dc glow discharge.

  12. Metal surface nitriding by laser induced plasma

    NASA Astrophysics Data System (ADS)

    Thomann, A. L.; Boulmer-Leborgne, C.; Andreazza-Vignolle, C.; Andreazza, P.; Hermann, J.; Blondiaux, G.

    1996-10-01

    We study a nitriding technique of metals by means of laser induced plasma. The synthesized layers are composed of a nitrogen concentration gradient over several μm depth, and are expected to be useful for tribological applications with no adhesion problem. The nitriding method is tested on the synthesis of titanium nitride which is a well-known compound, obtained at present by many deposition and diffusion techniques. In the method of interest, a laser beam is focused on a titanium target in a nitrogen atmosphere, leading to the creation of a plasma over the metal surface. In order to understand the layer formation, it is necessary to characterize the plasma as well as the surface that it has been in contact with. Progressive nitrogen incorporation in the titanium lattice and TiN synthesis are studied by characterizing samples prepared with increasing laser shot number (100-4000). The role of the laser wavelength is also inspected by comparing layers obtained with two kinds of pulsed lasers: a transversal-excited-atmospheric-pressure-CO2 laser (λ=10.6 μm) and a XeCl excimer laser (λ=308 nm). Simulations of the target temperature rise under laser irradiation are performed, which evidence differences in the initial laser/material interaction (material heated thickness, heating time duration, etc.) depending on the laser features (wavelength and pulse time duration). Results from plasma characterization also point out that the plasma composition and propagation mode depend on the laser wavelength. Correlation of these results with those obtained from layer analyses shows at first the important role played by the plasma in the nitrogen incorporation. Its presence is necessary and allows N2 dissociation and a better energy coupling with the target. Second, it appears that the nitrogen diffusion governs the nitriding process. The study of the metal nitriding efficiency, depending on the laser used, allows us to explain the differences observed in the layer features

  13. [The effect of plasma nitriding on tungsten burs].

    PubMed

    Cicciu, D; Russo, S; Grasso, C

    1989-01-01

    The authors have experimented the nitriding's effects on some cilindrical burs carbide utilized in dentistry after disamination on the applications methodics on plasma nitriding in neurosurgery, orthopedic surgery and in odontotherapy. This reacherys point out that nitriding plasma a durings increase and cutis greater capacity establish.

  14. Plasma nitriding of titanium alloy: Effect of roughness, hardness, biocompatibility, and bonding with bone cement.

    PubMed

    Khandaker, Morshed; Riahinezhad, Shahram; Li, Yanling; Vaughan, Melville B; Sultana, Fariha; Morris, Tracy L; Phinney, Lucas; Hossain, Khalid

    2016-11-25

    Titanium (Ti) alloys have been widely used in orthopedics and orthodontic surgeries as implants because of their beneficial chemical, mechanical, and biological properties. Improvement of these properties of a Ti alloy, Ti-6Al-4V Eli, is possible by the use of plasma nitriding treatment on the Ti alloy. The novelty of this study is the evaluation of a DC glow discharge nitrogen plasma treatment method on the surface, mechanical and biological properties of Ti alloy. Specifically, this study measured the chemical states, roughness, hardness, and biocompatibility of plasma nitride treated Ti-6Al-4V Eli as well as determined the effect of plasma treatment on the fracture strength between the Ti alloy and bone clement. This study hypothesized that DC glow discharge nitrogen plasma treatment may alter the surface chemical and mechanical states of the Ti alloy that may influence the fracture strength of implant/cement interfaces under static load. This study found that plasma nitride treatment on Ti alloy does not have effect on the roughness and biocompatibility (P value > 0.5), but significantly effect on the hardness and fracture strength of Ti-bone cement interfaces compared to those values of untreated Ti samples (P value < 0.5). Therefore, the DC glow discharge nitrogen plasma treated Ti alloy can potentially be used for orthopedic applications.

  15. Early stages during plasma nitriding of pure iron

    SciTech Connect

    Palacios, M.D.; Martinez, O.; Oseguera, J.

    1995-12-31

    The sequence of nitride formation during the early stages of plasma nitriding of pure iron was studied by optical microscopy, SEM, TEM and x-ray diffraction. Plasma nitriding at {approximately}490 C in a 25 vol.%H{sub 2} + 75 vol.%N{sub 2} mixture starts with the formation of {gamma}{prime}-Fe{sub 4}N after 40s. Once {gamma}{prime} nucleates, it mainly spreads laterally due to diffusion shortcuts in the discontinuous surface nitride layer. Before {gamma}{prime} is continuous on the surface, {epsilon} nucleates on top of it shortly after 40S. Epsilon is then observed to grow, both inwardly and laterally along with {gamma}{prime}. A compact {gamma}{prime}/{epsilon} bilayer forms on the surface at around 100s. The kinetics of nucleation, growth and compactation of the nitrides observed in the present work was significantly more rapid than in any of the nitriding process reported in the literature, including plasma nitriding. The acceleration of the nitriding kinetics in the early stages of plasma nitriding may be attributed to enhanced diffusion resulting from a high nitrogen flux from the plasma atmosphere. The results presented are consistent with the findings of a companion work on modeling the kinetics of nitride layer growth.

  16. The effect of Mo on the characteristics of a plasma nitrided layer of sintered iron

    NASA Astrophysics Data System (ADS)

    Bendo, T.; Maliska, A. M.; Acuña, J. J. S.; Binder, C.; Hammes, G.; Consoni, D. R.; Klein, A. N.

    2016-02-01

    Samples of PM (powder metallurgy) plain iron were superficially enriched with Mo during a sintering process using a DC discharge. The Mo atoms from the cathode produced an enriched layer of approximately 15-20 μm thick, and it was enriched with up to 2.0 at.% Mo. Subsequently, the samples were plasma nitrided in a gas mixture (N2/H2) at different temperatures and nitrogen concentrations. The effect of the molybdenum on the plasma nitrided layer of sintered iron was investigated. Abnormal nitride morphologies that developed in the surface layer were observed. The presence of Mo that was substitutionally dissolved in ferrite influences the nucleation and growth of the iron-nitride compound layer. The microstructure and (local) composition changes of the layers were investigated using scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) and glow discharge optical emission spectroscopy (GDOES) analyses. To evaluate the mechanical properties, Vickers microhardness tests were conducted along the sample cross-sections. According to the nitriding conditions, submicroscopic fcc Mo2N-type nitrides that are coherent with the α-Fe matrix develop, as confirmed by the TEM analysis and by the broadening of the diffraction lines in the X-ray diffractogram. Molybdenum nitrides, γ-Mo2N, with an fcc structure and sphere-like shapes were observed on the sample surface where the Mo concentrations were higher.

  17. First experimental results from DC/DC and AC/DC plasma-based power transformers

    NASA Astrophysics Data System (ADS)

    McEvoy, Aaron; Gibson, William; Nebel, Richard

    2016-10-01

    A plasma-based power transformer has been built and operated in both DC/DC and AC/DC mode. The proprietary Tibbar Plasma Technologies, Inc. transformer design consists of two cylindrically symmetric helical primary electrodes surrounding a low temperature plasma within which a secondary axial current is generated. Initial experimental results have compared well with simulations and moderate conversion efficiencies have been observed. A new proprietary device is currently being constructed that will utilize 3-phase 480 VAC input to achieve higher conversion efficiency and output power. A description of the apparatus and several potential applications will be presented along with preliminary experimental data demonstrating the DC/DC and AC/DC conversion processes. Work performed under ARPA-E contract DE-AR0000677.

  18. Microbial adherence to a nonprecious alloy after plasma nitriding process.

    PubMed

    Sonugelen, Mehmet; Destan, Uhmut Iyiyapici; Lambrecht, Fatma Yurt; Oztürk, Berran; Karadeniz, Süleyman

    2006-01-01

    To investigate the microbial adherence to the surfaces of a nonprecious metal alloy after plasma nitriding. The plasma-nitriding process was performed to the surfaces of metals prepared from a nickel-chromium alloy. The microorganisms were labeled with technetium-99m. After the labeling procedure, 60 metal disks were treated with a microorganism for each use. The results revealed that the amount of adherence of all microorganisms on surfaces was changed by plasma-nitriding process; adherence decreased substantially (P < .05) and the differences in plasma nitriding time were not significant (P> .05) With the plasma-nitriding process, the surface properties of nonprecious metal alloys can be changed, leading to decreased microbial adherence.

  19. Pulsed-DC DBD Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Duong, Alan; McGowan, Ryan; Disser, Katherine; Corke, Thomas; Matlis, Eric

    2016-11-01

    A new powering system for dielectric barrier discharge (DBD) plasma actuators that utilizes a pulsed-DC waveform is presented. The plasma actuator arrangement is identical to most typical AC-DBD designs with staggered electrodes that are separated by a dielectric insulator. However instead of an AC voltage input to drive the actuator, the pulsed-DC utilizes a DC voltage source. The DC source is supplied to both electrodes, and remains constant in time for the exposed electrode. The DC source for the covered electrode is periodically grounded for very short instants and then allowed to rise to the source DC level. This process results in a plasma actuator body force that is significantly larger than that with an AC-DBD at the same voltages. The important characteristics used in optimizing the pulsed-DC plasma actuators are presented. Time-resolved velocity measurements near the actuator are further used to understand the underlying physics of its operation compared to the AC-DBD. Supported by NASA Glenn RC.

  20. Plasma nitriding monitoring reactor: A model reactor for studying plasma nitriding processes using an active screen

    SciTech Connect

    Hamann, S. Röpcke, J.; Börner, K.; Burlacov, I.; Spies, H.-J.; Strämke, M.; Strämke, S.

    2015-12-15

    A laboratory scale plasma nitriding monitoring reactor (PLANIMOR) has been designed to study the basics of active screen plasma nitriding (ASPN) processes. PLANIMOR consists of a tube reactor vessel, made of borosilicate glass, enabling optical emission spectroscopy (OES) and infrared absorption spectroscopy. The linear setup of the electrode system of the reactor has the advantages to apply the diagnostic approaches on each part of the plasma process, separately. Furthermore, possible changes of the electrical field and of the heat generation, as they could appear in down-scaled cylindrical ASPN reactors, are avoided. PLANIMOR has been used for the nitriding of steel samples, achieving similar results as in an industrial scale ASPN reactor. A compact spectrometer using an external cavity quantum cascade laser combined with an optical multi-pass cell has been applied for the detection of molecular reaction products. This allowed the determination of the concentrations of four stable molecular species (CH{sub 4}, C{sub 2}H{sub 2}, HCN, and NH{sub 3}). With the help of OES, the rotational temperature of the screen plasma could be determined.

  1. Plasma nitriding monitoring reactor: A model reactor for studying plasma nitriding processes using an active screen.

    PubMed

    Hamann, S; Börner, K; Burlacov, I; Spies, H-J; Strämke, M; Strämke, S; Röpcke, J

    2015-12-01

    A laboratory scale plasma nitriding monitoring reactor (PLANIMOR) has been designed to study the basics of active screen plasma nitriding (ASPN) processes. PLANIMOR consists of a tube reactor vessel, made of borosilicate glass, enabling optical emission spectroscopy (OES) and infrared absorption spectroscopy. The linear setup of the electrode system of the reactor has the advantages to apply the diagnostic approaches on each part of the plasma process, separately. Furthermore, possible changes of the electrical field and of the heat generation, as they could appear in down-scaled cylindrical ASPN reactors, are avoided. PLANIMOR has been used for the nitriding of steel samples, achieving similar results as in an industrial scale ASPN reactor. A compact spectrometer using an external cavity quantum cascade laser combined with an optical multi-pass cell has been applied for the detection of molecular reaction products. This allowed the determination of the concentrations of four stable molecular species (CH4, C2H2, HCN, and NH3). With the help of OES, the rotational temperature of the screen plasma could be determined.

  2. Plasma nitriding monitoring reactor: A model reactor for studying plasma nitriding processes using an active screen

    NASA Astrophysics Data System (ADS)

    Hamann, S.; Börner, K.; Burlacov, I.; Spies, H.-J.; Strämke, M.; Strämke, S.; Röpcke, J.

    2015-12-01

    A laboratory scale plasma nitriding monitoring reactor (PLANIMOR) has been designed to study the basics of active screen plasma nitriding (ASPN) processes. PLANIMOR consists of a tube reactor vessel, made of borosilicate glass, enabling optical emission spectroscopy (OES) and infrared absorption spectroscopy. The linear setup of the electrode system of the reactor has the advantages to apply the diagnostic approaches on each part of the plasma process, separately. Furthermore, possible changes of the electrical field and of the heat generation, as they could appear in down-scaled cylindrical ASPN reactors, are avoided. PLANIMOR has been used for the nitriding of steel samples, achieving similar results as in an industrial scale ASPN reactor. A compact spectrometer using an external cavity quantum cascade laser combined with an optical multi-pass cell has been applied for the detection of molecular reaction products. This allowed the determination of the concentrations of four stable molecular species (CH4, C2H2, HCN, and NH3). With the help of OES, the rotational temperature of the screen plasma could be determined.

  3. Studies on optical emission spectroscopy of nitriding plasma and characterization of nitrided steel

    NASA Astrophysics Data System (ADS)

    Sharma, Manash Kumar

    Plasma in nature is abundant and appears quite beautiful in colour as can be seen in glow of sun and auroras. Plasma produced in laboratories is also quite interesting as a correspondence of the naturally occurring plasmas from a glow discharge to a tokamak. However, plasmas tuned to special conditions have been successfully utilized for material processing, of which, plasma nitriding is one and foremost. The work of the thesis focuses on the setting up of a plasma nitriding system with various diagnostics applied to plasma and plasma treated stainless steels. Emission spectroscopy and probe diagnostics are applied to study the optical and plasma properties whereas austenitic stainless steels are characterized by x-ray diffraction (XRD) and hardness test in order to demonstrate the application of the process. The optical and plasma properties during nitriding are motivating, as these properties will lead to conditions for the formation of surface layer. The formation of iron and chromium nitrides is another important asset of the plasma nitriding process, which is tested by XRD technique, while the surface hardness is tested by hardness test. Optical properties are found from optical emission spectroscopy (OES) in terms of emission intensities and wavelengths. Langmuir probe (LP) is used for finding variations of plasma parameters with respect to process parameters and to make a comparison of plasma parameters with those of optical and discharge parameters. A correlation between OES and material characterization properties is sought in order to make a clear understanding of the process. In Chapter 1, introduction to plasma, the possible applications with relevance to plasma nitriding and spectroscopy are described. Plasma nitriding (termed in the title as nitriding plasma for convenience) has emerged as a powerful tool in modifying surface properties of a material without affecting the bulk properties. The various advantages over a conventional gas nitriding

  4. Microstructure of Spark Plasma-Sintered Silicon Nitride Ceramics

    NASA Astrophysics Data System (ADS)

    Lukianova, O. A.; Novikov, V. Yu.; Parkhomenko, A. A.; Sirota, V. V.; Krasilnikov, V. V.

    2017-04-01

    The microstructure and phase composition of the high-content Al2O3-Y2O3-doped spark plasma-sintered silicon nitride were investigated. Fully dense silicon nitride ceramics with a typical α-Si3N4 equiaxed structure with average grain size from 200 to 530 nm, high elastic modulus of 288 GPa, and high hardness of 2038 HV were spark plasma sintered (SPSed) at 1550 °C. Silicon nitride with elongated β-Si3N4 grains, higher hardness of 1800 HV, density of 3.25 g/cm3, and Young's modulus 300 GPa SPSed at 1650 °C was also reviewed.

  5. Osteoblastlike cell adhesion on titanium surfaces modified by plasma nitriding.

    PubMed

    da Silva, Jose Sandro Pereira; Amico, Sandro Campos; Rodrigues, Almir Olegario Neves; Barboza, Carlos Augusto Galvao; Alves, Clodomiro; Croci, Alberto Tesconi

    2011-01-01

    The aim of this study was to evaluate the characteristics of various titanium surfaces modified by cold plasma nitriding in terms of adhesion and proliferation of rat osteoblastlike cells. Samples of grade 2 titanium were subjected to three different surface modification processes: polishing, nitriding by plasma direct current, and nitriding by cathodic cage discharge. To evaluate the effect of the surface treatment on the cellular response, the adhesion and proliferation of osteoblastlike cells (MC3T3) were quantified and the results were analyzed by Kruskal-Wallis and Friedman statistical tests. Cellular morphology was observed by scanning electron microscopy. There was more MC3T3 cell attachment on the rougher surfaces produced by cathodic cage discharge compared with polished samples (P < .05). Plasma nitriding improves titanium surface roughness and wettability, leading to osteoblastlike cell adhesion.

  6. Phase formation in selected surface-roughened plasma-nitrided 304 austenite stainless steel.

    PubMed

    Singh, Gajendra Prasad; Joseph, Alphonsa; Raole, Prakash Manohar; Barhai, Prema Kanta; Mukherjee, Subroto

    2008-04-01

    Direct current (DC) glow discharge plasma nitriding was carried out on three selected surface-roughened AISI 304 stainless steel samples at 833 K under 4 mbar pressures for 24 h in the presence of N2:H2 gas mixtures of 50 : 50 ratios. After plasma nitriding, the phase formation, case depth, surface roughness, and microhardness of a plasma-nitrided layer were evaluated by glancing angle x-ray diffractogram, optical microscope, stylus profilometer, and Vickers microhardness tester techniques. The case depth, surface hardness, and phase formation variations were observed with a variation in initial surface roughness. The diffraction patterns of the plasma-nitrided samples showed the modified intensities of the α and γ phases along with those of the CrN, Fe4N, and Fe3N phases. Hardness and case depth variations were observed with a variation in surface roughness. A maximum hardness of 1058 Hv and a case depth of 95 μm were achieved in least surface-roughened samples.

  7. Phase formation in selected surface-roughened plasma-nitrided 304 austenite stainless steel

    PubMed Central

    Singh, Gajendra Prasad; Joseph, Alphonsa; Raole, Prakash Manohar; Barhai, Prema Kanta; Mukherjee, Subroto

    2008-01-01

    Direct current (DC) glow discharge plasma nitriding was carried out on three selected surface-roughened AISI 304 stainless steel samples at 833 K under 4 mbar pressures for 24 h in the presence of N2:H2 gas mixtures of 50 : 50 ratios. After plasma nitriding, the phase formation, case depth, surface roughness, and microhardness of a plasma-nitrided layer were evaluated by glancing angle x-ray diffractogram, optical microscope, stylus profilometer, and Vickers microhardness tester techniques. The case depth, surface hardness, and phase formation variations were observed with a variation in initial surface roughness. The diffraction patterns of the plasma-nitrided samples showed the modified intensities of the α and γ phases along with those of the CrN, Fe4N, and Fe3N phases. Hardness and case depth variations were observed with a variation in surface roughness. A maximum hardness of 1058 Hv and a case depth of 95 μm were achieved in least surface-roughened samples. PMID:27877982

  8. Nanotribological response of a plasma nitrided bio-steel.

    PubMed

    Samanta, Aniruddha; Chakraborty, Himel; Bhattacharya, Manjima; Ghosh, Jiten; Sreemany, Monjoy; Bysakh, Sandip; Rane, Ramkrishna; Joseph, Alphonsa; Jhala, Ghanshyam; Mukherjee, Subroto; Das, Mitun; Mukhopadhyay, Anoop K

    2017-01-01

    AISI 316L is a well known biocompatible, austenitic stainless steel (SS). It is thus a bio-steel. Considering its importance as a bio-prosthesis material here we report the plasma nitriding of AISI 316L (SS) followed by its microstructural and nanotribological characterization. Plasma nitriding of the SS samples was carried out in a plasma reactor with a hot wall vacuum chamber. For ease of comparison these plasma nitrided samples were termed as SSPN. The experimental results confirmed the formations of an embedded nitrided metal layer zone (ENMLZ) and an interface zone (IZ) between the ENMLZ and the unnitrided bulk metallic layer zone (BMLZ) in the SSPN sample. These ENMLZ and IZ in the SSPN sample were richer in iron nitride (FeN) chromium nitride (CrN) along with the austenite phase. The results from nanoindentation, microscratch, nanoscratch and sliding wear studies confirmed that the static contact deformation resistance, the microwear, nanowear and sliding wear resistance of the SSPN samples were much better than those of the SS samples. These results were explained in terms of structure-property correlations.

  9. Effect of oxygen plasma on nanomechanical silicon nitride resonators

    NASA Astrophysics Data System (ADS)

    Luhmann, Niklas; Jachimowicz, Artur; Schalko, Johannes; Sadeghi, Pedram; Sauer, Markus; Foelske-Schmitz, Annette; Schmid, Silvan

    2017-08-01

    Precise control of tensile stress and intrinsic damping is crucial for the optimal design of nanomechanical systems for sensor applications and quantum optomechanics in particular. In this letter, we study the influence of oxygen plasma on the tensile stress and intrinsic damping of nanomechanical silicon nitride resonators. Oxygen plasma treatments are common steps in micro and nanofabrication. We show that oxygen plasma for only a few minutes oxidizes the silicon nitride surface, creating several nanometer thick silicon dioxide layers with a compressive stress of 1.30(16) GPa. Such oxide layers can cause a reduction in the effective tensile stress of a 50 nm thick stoichiometric silicon nitride membrane by almost 50%. Additionally, intrinsic damping linearly increases with the silicon dioxide film thickness. An oxide layer of 1.5 nm grown in just 10 s in a 50 W oxygen plasma almost doubled the intrinsic damping. The oxide surface layer can be efficiently removed in buffered hydrofluoric acid.

  10. Effect of Plasma Nitriding on the Performance of WC-Co Cutting Tools

    NASA Astrophysics Data System (ADS)

    Hamzaoglu, Ebru; Yilmaz, Safak; Gulmez, Turgut

    2011-04-01

    This paper presents the effect of nitriding process parameters on the cutting performance of WC-Co tools. The cutting performance was measured by CNC machining of GG25 cast iron parts. The hardness and phase composition of nitrided layer were determined for different plasma nitriding temperatures and times. The hardness of the nitrided layer increased at all plasma nitrided conditions investigated. However, the machining performance of the cutting inserts varied in the range between a 60% increase and a 40% decrease after plasma nitriding. The maximum number of machined parts was seen when the insert was nitrided at 600 °C-4 h and at 500 °C-4 h.

  11. A dc Penning Surface-Plasma Source

    DTIC Science & Technology

    2007-11-02

    LA-UR-93-2990 Title: A dc Penning Surface-Plasma Source Author(s): Submitted to: H. Vernon Smith, Jr., Paul Allison, Carl Geisik, David R...Type: HC Number of Copies In Library: 000001 Record ID: 28620 A de Penning Surface-Plasma Source* H. Vernon Smith, Jr., Paul Allison, Carl Geisik...Schechter, J. H. Whealton, and J. J. Donaghy, ATP Conf. Proc. No. 158, 366 (1987). 8) H. V. Smith, Jr., N. M. Schnurr, D. H. Whitaker , and K. E. Kalash

  12. Microstructure and Properties of Plasma Source Nitrided AISI 316 Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Li, G. Y.; Lei, M. K.

    2017-01-01

    Plasma source nitriding is a relatively new nitriding technology which can overcome those inherent shortcomings associated with conventional direct current plasma nitriding technology such as the arcing surface damage, the edging effect and the hollow cathode effect. There is considerable study on the properties of nitrided samples for laboratorial scale plasma source nitriding system; however, little information has been reported on the industrial-scale plasma source nitriding system. In this work, AISI 316 austenitic stainless steel samples were nitrided by an industrial-scale plasma source nitriding system at various nitriding temperatures (350, 400, 450 and 500 °C) with a floating potential. A high-nitrogen face-centered-cubic phase (γN) formed on the surface of nitrided sample surface. As the nitriding temperature was increased, the γN phase layer thickness increased, varying from 1.5 μm for the lowest nitriding temperature of 350 °C, to 30 μm for the highest nitriding temperature of 500 °C. The maximum Vickers microhardness of the γN phase layer with a peak nitrogen concentration of 20 at.% is about HV 0.1 N 15.1 GPa at the nitriding temperature of 450 °C. The wear and corrosion experimental results demonstrated that the γN phase was formed on the surface of AISI 316 austenitic stainless steel by plasma source nitriding, which exhibits not only high wear resistance, but also good pitting corrosion resistance.

  13. Microstructure and Properties of Plasma Source Nitrided AISI 316 Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Li, G. Y.; Lei, M. K.

    2016-11-01

    Plasma source nitriding is a relatively new nitriding technology which can overcome those inherent shortcomings associated with conventional direct current plasma nitriding technology such as the arcing surface damage, the edging effect and the hollow cathode effect. There is considerable study on the properties of nitrided samples for laboratorial scale plasma source nitriding system; however, little information has been reported on the industrial-scale plasma source nitriding system. In this work, AISI 316 austenitic stainless steel samples were nitrided by an industrial-scale plasma source nitriding system at various nitriding temperatures (350, 400, 450 and 500 °C) with a floating potential. A high-nitrogen face-centered-cubic phase (γN) formed on the surface of nitrided sample surface. As the nitriding temperature was increased, the γN phase layer thickness increased, varying from 1.5 μm for the lowest nitriding temperature of 350 °C, to 30 μm for the highest nitriding temperature of 500 °C. The maximum Vickers microhardness of the γN phase layer with a peak nitrogen concentration of 20 at.% is about HV 0.1 N 15.1 GPa at the nitriding temperature of 450 °C. The wear and corrosion experimental results demonstrated that the γN phase was formed on the surface of AISI 316 austenitic stainless steel by plasma source nitriding, which exhibits not only high wear resistance, but also good pitting corrosion resistance.

  14. Plasma deposited silicon nitride for indium phosphide encapsulation

    NASA Technical Reports Server (NTRS)

    Valco, G. J.; Kapoor, V. J.; Biedenbender, M. D.; Williams, W. D.

    1989-01-01

    The composition and the annealing characteristics of plasma-deposited silicon-nitride encapsulating films on the ion-implanted InP substrates were investigated, using two different substrate-cleaning procedures (organic solvents and HF or HIO3 solutions) prior to encapsulation. The effect of plasma deposition of silicon nitride on the InP substrates was assessed through the current-voltage characteristics of Schottky diodes. Results of XPS analyses showed that the cleaning procedure that employed HF solution left less oxygen on the InP surface than the procedure involving HIO3. No chemical interaction between the film and the substrate was observed before or after annealing.

  15. Plasma deposited silicon nitride for indium phosphide encapsulation

    NASA Technical Reports Server (NTRS)

    Valco, G. J.; Kapoor, V. J.; Biedenbender, M. D.; Williams, W. D.

    1989-01-01

    The composition and the annealing characteristics of plasma-deposited silicon-nitride encapsulating films on the ion-implanted InP substrates were investigated, using two different substrate-cleaning procedures (organic solvents and HF or HIO3 solutions) prior to encapsulation. The effect of plasma deposition of silicon nitride on the InP substrates was assessed through the current-voltage characteristics of Schottky diodes. Results of XPS analyses showed that the cleaning procedure that employed HF solution left less oxygen on the InP surface than the procedure involving HIO3. No chemical interaction between the film and the substrate was observed before or after annealing.

  16. Thermal Plasma Synthesis of Crystalline Gallium Nitride Nanopowder from Gallium Nitrate Hydrate and Melamine

    PubMed Central

    Kim, Tae-Hee; Choi, Sooseok; Park, Dong-Wha

    2016-01-01

    Gallium nitride (GaN) nanopowder used as a blue fluorescent material was synthesized by using a direct current (DC) non-transferred arc plasma. Gallium nitrate hydrate (Ga(NO3)3∙xH2O) was used as a raw material and NH3 gas was used as a nitridation source. Additionally, melamine (C3H6N6) powder was injected into the plasma flame to prevent the oxidation of gallium to gallium oxide (Ga2O3). Argon thermal plasma was applied to synthesize GaN nanopowder. The synthesized GaN nanopowder by thermal plasma has low crystallinity and purity. It was improved to relatively high crystallinity and purity by annealing. The crystallinity is enhanced by the thermal treatment and the purity was increased by the elimination of residual C3H6N6. The combined process of thermal plasma and annealing was appropriate for synthesizing crystalline GaN nanopowder. The annealing process after the plasma synthesis of GaN nanopowder eliminated residual contamination and enhanced the crystallinity of GaN nanopowder. As a result, crystalline GaN nanopowder which has an average particle size of 30 nm was synthesized by the combination of thermal plasma treatment and annealing.

  17. Thermal Plasma Synthesis of Crystalline Gallium Nitride Nanopowder from Gallium Nitrate Hydrate and Melamine.

    PubMed

    Kim, Tae-Hee; Choi, Sooseok; Park, Dong-Wha

    2016-02-24

    Gallium nitride (GaN) nanopowder used as a blue fluorescent material was synthesized by using a direct current (DC) non-transferred arc plasma. Gallium nitrate hydrate (Ga(NO₃)₃∙xH₂O) was used as a raw material and NH₃ gas was used as a nitridation source. Additionally, melamine (C₃H₆N₆) powder was injected into the plasma flame to prevent the oxidation of gallium to gallium oxide (Ga₂O₃). Argon thermal plasma was applied to synthesize GaN nanopowder. The synthesized GaN nanopowder by thermal plasma has low crystallinity and purity. It was improved to relatively high crystallinity and purity by annealing. The crystallinity is enhanced by the thermal treatment and the purity was increased by the elimination of residual C₃H₆N₆. The combined process of thermal plasma and annealing was appropriate for synthesizing crystalline GaN nanopowder. The annealing process after the plasma synthesis of GaN nanopowder eliminated residual contamination and enhanced the crystallinity of GaN nanopowder. As a result, crystalline GaN nanopowder which has an average particle size of 30 nm was synthesized by the combination of thermal plasma treatment and annealing.

  18. CVD diamond growth by dc plasma torch

    NASA Astrophysics Data System (ADS)

    Klocek, Paul; Hoggins, James T.; Taborek, Peter; McKenna, Tom A.

    1990-12-01

    A dc arc discharge plasma torch has been developed for chemical vapor deposition (CVD) diamond growth. The apparatus and process parameters are described. Free-standing polycrystalline diamond samples of 50 mm by 50 mm by a few mm have been grown at high rates. The Raman spectra of the samples show little nondiamond structure. Transmission electron microscopy indicates that the diamond is highly twinned and has a high defect concentration. The infrared spectra indicate the presence of hydrogen contamination in the diamond via absorption bands associated with carbon-hydrogen motion. 2.

  19. Improvement of wear resistance for C45 steel using plasma nitriding, nitrocarburizing and nitriding/ manganese phosphating duplex treatment

    NASA Astrophysics Data System (ADS)

    Doan, T. V.; Kusmič, D.; Pospíchal, M.; Dobrocký, D.

    2017-02-01

    This article focuses on effect of plasma nitriding, nitrocarburizing and nitriding/manganese phosphating duplex treatments to wear resistance of C45 steel substrate. The wear test “ball on disc” was conducted to evaluate the coefficient of friction and wear rate using the BRUKER UMT-3 tribometer. The analysis results indicated that nitrocarburizing obtained the best wear resistance; the worst wear resistance was plasma nitriding. Manganese phosphating coating enabled to reduce the coefficient of friction enhanced wear resistance nitrided layer. The used surface treatments also improve non-equal wear of tempered surface over the sliding track.

  20. Bone tissue response to plasma-nitrided titanium implant surfaces

    PubMed Central

    FERRAZ, Emanuela Prado; SVERZUT, Alexander Tadeu; FREITAS, Gileade Pereira; SÁ, Juliana Carvalho; ALVES, Clodomiro; BELOTI, Marcio Mateus; ROSA, Adalberto Luiz

    2015-01-01

    A current goal of dental implant research is the development of titanium (Ti) surfaces to improve osseointegration. Plasma nitriding treatments generate surfaces that favor osteoblast differentiation, a key event to the process of osteogenesis. Based on this, it is possible to hypothesize that plasma-nitrided Ti implants may positively impact osseointegration. Objective The aim of this study was to evaluate the in vivo bone response to Ti surfaces modified by plasma-nitriding treatments. Material and Methods Surface treatments consisted of 20% N2 and 80% H2, 450°C and 1.5 mbar during 1 h for planar and 3 h for hollow cathode. Untreated surface was used as control. Ten implants of each surface were placed into rabbit tibiae and 6 weeks post-implantation they were harvested for histological and histomorphometric analyses. Results Bone formation was observed in contact with all implants without statistically significant differences among the evaluated surfaces in terms of bone-to-implant contact, bone area between threads, and bone area within the mirror area. Conclusion Our results indicate that plasma nitriding treatments generate Ti implants that induce similar bone response to the untreated ones. Thus, as these treatments improve the physico-chemical properties of Ti without affecting its biocompatibility, they could be combined with modifications that favor bone formation in order to develop new implant surfaces. PMID:25760262

  1. Bone tissue response to plasma-nitrided titanium implant surfaces.

    PubMed

    Ferraz, Emanuela Prado; Sverzut, Alexander Tadeu; Freitas, Gileade Pereira; Sá, Juliana Carvalho; Alves, Clodomiro; Beloti, Marcio Mateus; Rosa, Adalberto Luiz

    2015-01-01

    A current goal of dental implant research is the development of titanium (Ti) surfaces to improve osseointegration. Plasma nitriding treatments generate surfaces that favor osteoblast differentiation, a key event to the process of osteogenesis. Based on this, it is possible to hypothesize that plasma-nitrided Ti implants may positively impact osseointegration. Objective The aim of this study was to evaluate the in vivo bone response to Ti surfaces modified by plasma-nitriding treatments. Material and Methods Surface treatments consisted of 20% N2 and 80% H2, 450°C and 1.5 mbar during 1 h for planar and 3 h for hollow cathode. Untreated surface was used as control. Ten implants of each surface were placed into rabbit tibiae and 6 weeks post-implantation they were harvested for histological and histomorphometric analyses. Results Bone formation was observed in contact with all implants without statistically significant differences among the evaluated surfaces in terms of bone-to-implant contact, bone area between threads, and bone area within the mirror area. Conclusion Our results indicate that plasma nitriding treatments generate Ti implants that induce similar bone response to the untreated ones. Thus, as these treatments improve the physico-chemical properties of Ti without affecting its biocompatibility, they could be combined with modifications that favor bone formation in order to develop new implant surfaces.

  2. Simulation of the dc Plasma in Carbon Nanotube Growth

    NASA Technical Reports Server (NTRS)

    Hash, David; Bose, Deepak; Govindan, T. R.; Meyyappan, M.; Biegel, Bryan (Technical Monitor)

    2003-01-01

    A model for the dc plasma used in carbon nanotube growth is presented, and one-dimensional simulations of an acetylene/ammonia/argon system are performed. The effect of dc bias is illustrated by examining electron temperature, electron and ion densities, and neutral densities. Introducing a tungsten filament in the dc plasma, as in hot filament chemical vapor deposition with plasma assistance, shows negligible influence on the system characteristics.

  3. Moessbauer spectroscopy study on the corrosion resistance of plasma nitrided ASTM F138 stainless steel in chloride solution

    SciTech Connect

    Souza, S.D. de; Olzon-Dionysio, M.; Basso, R.L.O.; Souza, S. de

    2010-10-15

    Plasma nitriding of ASTM F138 stainless steel samples has been carried out using dc glow discharge under 80% H{sub 2}-20% N{sub 2} gas mixture, at 673 K, and 2, 4, and 7 h time intervals, in order to investigate the influence of treatment time on the microstructure and the corrosion resistance properties. The samples were characterized by scanning electron microscopy, glancing angle X-ray diffraction and conversion electron Moessbauer spectroscopy, besides electrochemical tests in NaCl aerated solution. A modified layer of about 6 {mu}m was observed for all the nitrided samples, independent of nitriding time. The X-ray diffraction analysis shows broad {gamma}{sub N} phase peaks, signifying a great degree of nitrogen supersaturation. Besides {gamma}{sub N,} the Moessbauer spectroscopy results indicated the occurrence of {gamma}' and {epsilon} phases, as well as some other less important phases. Corrosion measurements demonstrate that the plasma nitriding time affects the corrosion resistance and the best performance is reached at 4 h treatment. It seems that the {epsilon}/{gamma}' fraction ratio plays an important role on the resistance corrosion. Additionally, the Moessbauer spectroscopy was decisive in this study, since it was able to identify and quantify the iron phases that influence the corrosion resistance of plasma nitrided ASTM F138 samples.

  4. Bright nitriding of Cr-Mo-steels in plasma and gas

    SciTech Connect

    Larisch, B.; Spies, H.J.; Hoeck, K.

    1995-12-31

    Although the reduction of the white layer in special gas atmospheres directly after nitriding and bright nitriding were reported a long time ago, the white layer is mostly removed by mechanical or chemical means in industrial practice. The main reason for this is poor process control. However, new requirements such as the duplex treatment (nitriding + hardcoating), demand a more detailed examination of bright nitriding. Today, new possibilities exist for process control in gas nitriding by solid electrolyte sensors. Steel grades 17CrMoV10 and 31CrMoV9 were bright nitrided in gas and plasma. In contrast to the above experiments, in the two-step technology no white layer forms in the first step (20min) at a higher nitriding potential. By this, the formation of a soft surface layer (of iron) can be avoided. Limits of this technology--for instance in the depth of the formed nitrided case--are discussed. Reasons for the often discussed faster nitriding in plasma are explained on the basis of the experimental results. The influence of ion bombardment in plasma nitriding on the activation of the surface and the nitriding results is discussed in comparison to gas nitriding. In this context the advantages of plasma nitriding--with respect to higher chromium alloyed steels (>5%Cr), which tend to passivation--are shown.

  5. Pulsed DC magnetron sputtered piezoelectric thin film aluminum nitride – Technology and piezoelectric properties

    SciTech Connect

    Stoeckel, C. Kaufmann, C.; Hahn, R.; Schulze, R.; Billep, D.; Gessner, T.

    2014-07-21

    Pulsed DC magnetron sputtered aluminum nitride (AlN) thin films are prepared on several seed layers and at different sputtering conditions. The piezoelectric c-axis (002) orientation of the AlN is analyzed with X-ray diffraction method. The transverse piezoelectric coefficient d{sub 31} is determined with a Laser-Doppler-Vibrometer at cantilevers and membranes by analytical calculations and finite element method. Additionally, thin film AlN on bulk silicon is used to characterize the longitudinal piezoelectric charge coefficient d{sub 33}.

  6. Effect of plasma nitriding and titanium nitride coating on the corrosion resistance of titanium.

    PubMed

    Wang, Xianli; Bai, Shizhu; Li, Fang; Li, Dongmei; Zhang, Jing; Tian, Min; Zhang, Qian; Tong, Yu; Zhang, Zichuan; Wang, Guowei; Guo, Tianwen; Ma, Chufan

    2016-09-01

    The passive film on the surface of titanium can be destroyed by immersion in a fluoridated acidic medium. Coating with titanium nitride (TiN) may improve the corrosion resistance of titanium. The purpose of this in vitro study was to investigate the effect of duplex treatment with plasma nitriding and TiN coating on the corrosion resistance of cast titanium. Cast titanium was treated with plasma nitriding and TiN coating. The corrosion resistance of the duplex-treated titanium in fluoride-containing artificial saliva was then investigated through electrochemical and immersion tests. The corroded surface was characterized by scanning electron microscopy (SEM) with energy-dispersive spectroscopy surface scan analysis. The data were analyzed using ANOVA (α=.05) RESULTS: Duplex treatment generated a dense and uniform TiN film with a thickness of 4.5 μm. Compared with untreated titanium, the duplex-treated titanium displayed higher corrosion potential (Ecorr) values (P<.001) and lower corrosion current density (Icorr) values (P<.001). SEM results showed that the surface of untreated titanium was more heavily corroded than that of duplex-treated titanium. Surface scan analysis of duplex-treated titanium that had been immersed in artificial saliva containing 2 g/L fluoride revealed fluorine on the titanium surface, whereas fluorine was not observed on the surface of untreated titanium after immersion in fluoride-containing artificial saliva. The concentration of titanium ions released from the treated titanium was less than the amount released from untreated titanium (P<.001). Duplex treatment by plasma nitriding and TiN coating significantly improved the corrosion resistance of cast titanium in a fluoride-containing environment. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  7. Accelerated nitridation and oxidation by plasma on polyethylene

    NASA Astrophysics Data System (ADS)

    Olayo, M. G.; Colín, E.; Cruz, G. J.; Morales, J.; Olayo, R.

    2009-12-01

    Glow discharges of oxygen and nitrogen were applied to low density polyethylene thin films in order to study accelerated oxidation and nitridation in the polymer. The studies were focused on the morphologic, crystalline and hydrophilic evolution promoted by plasma exposure. The particular chemical characteristics of the gases and the constant impact of high-energy particles on the surfaces produced different types of erosion. Oxygen plasmas produced the release of fragments from the polymeric surface which created fibered textures and nitrogen plasmas resulted in folded morphologies of nano and micro dimensions on polyethylene. The plasmas of both gases increased and decreased the crystallinity in the polymers, between 33% and 57%, with similar tendencies, differing only in the percentage of crystallinity. The plasma exposure produced a decrease in the contact angles of water on polyethylene in the first 30 min of plasma, from 70% in the untreated polymers, to 45% and 35% as a consequence of the polar groups added to the surface.

  8. Hardening Roll Surface by Plasma Nitriding with Subsequent Hardfacing

    NASA Astrophysics Data System (ADS)

    Pesin, A.; Pustovoytov, D.; Vafin, R.; Yagafarov, I.; Vardanyan, E.

    2017-05-01

    The wear of the surface layer of rolls after ion nitriding in glow discharge, followed by a coating of TiN -TiAlN plasma arc are studied and simulated. stress-strain state of the material rolls under asymmetric rolling with ultra-high shear deformations is simulated. The effect of thermal fields, formed upon contact of the tool and a deformable sheet, the structure of aluminum alloys, are considered.

  9. Effect of Plasma Nitriding Parameters on the Wear Resistance of Alloy Inconel 718

    NASA Astrophysics Data System (ADS)

    Kovací, Halim; Ghahramanzadeh ASL, Hojjat; Albayrak, Çigdem; Alsaran, Akgün; Çelik, Ayhan

    2016-11-01

    The effect of the temperature and duration of plasma nitriding on the microstructure and friction and wear parameters of Inconel 718 nickel alloy is investigated. The process of plasma nitriding is conducted in a nitrogen-hydrogen gaseous mixture at a temperature of 400, 500 and 600°C for 1 and 4 h. The modulus of elasticity of the nitrided layer, the micro- and nanohardness, the surface roughness, the friction factor and the wear resistance of the alloy are determined prior to and after the nitriding. The optimum nitriding regime providing the best tribological characteristics is determined.

  10. Energy Balance in DC Arc Plasma Melting Furnace

    NASA Astrophysics Data System (ADS)

    Zhao, Peng; Meng, Yuedong; Yu, Xinyao; Chen, Longwei; Jiang, Yiman; Ni, Guohua; Chen, Mingzhou

    2009-04-01

    In order to treat hazardous municipal solid waste incinerator's (MSWI) fly ash, a new DC arc plasma furnace was developed. Taking an arc of 100 V/1000 A DC as an example, the heat transfer characteristics of the DC arc plasma, ablation of electrodes, heat properties of the fly ash during melting, heat transfer characteristics of the flue gas, and heat loss of the furnace were analyzed based on the energy conservation law, so as to achieve the total heat information and energy balance during plasma processing, and to provide a theoretical basis for an optimized design of the structure and to improve energy efficiency.

  11. Pulsed plasma ion nitriding and control of the compound zone (or white layer)

    SciTech Connect

    Pye, D.

    1995-12-31

    Ion nitriding of alloy steels has been studied for many years using the process gases of hydrogen and nitrogen and utilizing specific furnace control parameters, and has proven to be both an effective and commercially viable process when dealing with uniform shapes. However, complex shape geometries require a different approach as far as the process method is concerned. It is through the use of pulsed plasma DC power in conjunction with hot wall furnace technology that complex shapes, such as gears and extrusion dies, can be successfully treated with no serious risk of mechanical damage to the part as a result of arc discharging. Consideration of the material surface is extremely important and is effected by sputter cleaning. The ion nitriding process, using pulsed DC power and process temperatures ranging from 800 F (425 C) to 1,050 F (565 C) and cycle times from 1--60 hours, have been used, depending on the pretreatment which may have taken place (such as tempering of the martensitic stainless steels and highly alloyed steels). The ability to control the process parameters allows considerable flexibility in tailoring specific chemical and metallurgical surface properties, which are desirable for a particular material and shape being treated.

  12. Humidity-dependent stability of amorphous germanium nitrides fabricated by plasma nitridation

    SciTech Connect

    Kutsuki, Katsuhiro; Okamoto, Gaku; Hosoi, Takuji; Shimura, Takayoshi; Watanabe, Heiji

    2007-10-15

    We have investigated the stability of amorphous germanium nitride (Ge{sub 3}N{sub 4}) layers formed by plasma nitridation of Ge(100) surfaces using x-ray photoelectron spectroscopy and atomic force microscopy. We have found that humidity in the air accelerates the degradation of Ge{sub 3}N{sub 4} layers and that under 80% humidity condition, most of the Ge-N bonds convert to Ge-O bonds, producing a uniform GeO{sub 2} layer, within 12 h even at room temperature. After this conversion of nitrides to oxides, the surface roughness drastically increased by forming GeO{sub 2} islands on the surfaces. These findings indicate that although Ge{sub 3}N{sub 4} layers have superior thermal stability compared to the GeO{sub 2} layers, Ge{sub 3}N{sub 4} reacts readily with hydroxyl groups and it is therefore essential to take the best care of the moisture in the fabrication of Ge-based devices with Ge{sub 3}N{sub 4} insulator or passivation layers.

  13. Damage development of gallium nitride under plasma exposure

    NASA Astrophysics Data System (ADS)

    Ogawa, Daisuke; Banno, Yoshitsugu; Nakano, Yoshitaka; Nakamura, Keiji

    2016-09-01

    Plasma damage has been focused on since 1990s. In this era, this issue was manly targeted onto silicon-based semiconductors. However, since the gallium nitride (GaN) was paid attentions to after blue LEDs, they start to consider the damages given to GaN as well. We have so far utilized photoluminescence (PL) emission from the surface of GaN film to monitor the evolution of damage given by plasma exposure. This measurement gives us clues how plasma exposure changed intermediate electronical states in the film without taking the film out of the chamber. First of all, we analyzed the development of damage given by argon plasma, which is one of the most fundamental plasma to analyze. Argon plasma is responsible to give only physical damages over a GaN film. Our PL measurements showed a significant decrease within approximately 10 seconds after the plasma exposure started. This means that ions and radiations created from the plasma gives significant damages to the GaN film even short period of time. Chlorine-related gas is normally utilized for chemical etching. Chlorine species realize continuous damage layer removals, but some reports already mentioned that the processed device has difference electrical properties after the plasma exposure. In this presentation, we will show what happens to GaN film after the plasma exposure in terms of crystal structure and impurities of GaN, by connecting PL emission and ex-situ measurements.

  14. Caracterisation of Titanium Nitride Layers Deposited by Reactive Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Roşu, Radu Alexandru; Şerban, Viorel-Aurel; Bucur, Alexandra Ioana; Popescu, Mihaela; Uţu, Dragoş

    2011-01-01

    Forming and cutting tools are subjected to the intense wear solicitations. Usually, they are either subject to superficial heat treatments or are covered with various materials with high mechanical properties. In recent years, thermal spraying is used increasingly in engineering area because of the large range of materials that can be used for the coatings. Titanium nitride is a ceramic material with high hardness which is used to cover the cutting tools increasing their lifetime. The paper presents the results obtained after deposition of titanium nitride layers by reactive plasma spraying (RPS). As deposition material was used titanium powder and as substratum was used titanium alloy (Ti6Al4V). Macroscopic and microscopic (scanning electron microscopy) images of the deposited layers and the X ray diffraction of the coatings are presented. Demonstration program with layers deposited with thickness between 68,5 and 81,4 μm has been achieved and presented.

  15. Structural modification of boron nitride nanotubes by plasma irradiation

    NASA Astrophysics Data System (ADS)

    Ikuno, Takashi; Begtrup, Gavi; Aloni, Shaul; Kis, Andras; Okawa, David; Zettl, Alex

    2006-03-01

    Boron nitride (BN) and boron-carbon-nitride (B-C-N) nanotubes (NTs) are candidates for potential nanosized electronic and optical devices due to extraordinary physical and chemical properties. In terms of electronic property, in contrast to the insulating BNNTs with about 5.5 eV band gap, ternary B-C-N NTs has semiconducting property, the band gap of which is primarily determined by their chemical compositions. Although one of the methods to make B-C-N NTs is C doping to BNNTs, it is difficult to modify the structure and composition of BNNTs due to its chemical inertness and strong sp2 bond. In this study, we performed to modify the structure and composition of BNNTs by plasma irradiation for synthesizing B-C-N NTs. Hydrocarbon plasma was utilized for structural modification of BNNTs. The structural properties and the composition were characterized by high-resolution transmission electron microscopy and electron energy loss spectroscopy. After the plasma irradiation, outer several BN layers were modified to wavy structure from straight shape, and the defects were observed in almost BN layers, indicating destruction of crystal structure by collision of energetic particles in plasma and BNNTs. There are 5 -- 30 at% of C in BNNTs and C atoms were inhomogeneously distributed in B-C-N NTs. The electron transport property of the modified B-C-N NTs will be reported in our presentation.

  16. Nitriding molybdenum: Effects of duration and fill gas pressure when using 100-Hz pulse DC discharge technique

    NASA Astrophysics Data System (ADS)

    Ikhlaq, U.; R., Ahmad; Shafiq, M.; Saleem, S.; S. Shah, M.; Hussain, T.; A. Khan, I.; K., Abbas; S. Abbas, M.

    2014-10-01

    Molybdenum is nitrided by a 100-Hz pulsed DC glow discharge technique for various time durations and fill gas pressures to study the effects on the surface properties of molybdenum. X-ray diffractometry (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) are used for the structural and morphological analysis of the nitrided layers. Vickers' microhardness tester is utilized to investigate surface microhardness. Phase analysis shows the formation of more molybdenum nitride molecules for longer nitriding durations at fill gas pressures of 2 mbar and 3 mbar (1 bar = 105 Pa). A considerable increase in surface microhardness (approximately by a factor of 2) is observed for longer duration (10 h) and 2-mbar pressure. Longer duration (10 h) and 2-mbar fill gas pressure favors the formation of homogeneous, smooth, hard layers by the incorporation of more nitrogen.

  17. Generation of ammonia plasma using a helical antenna and nitridation of GaAs surface

    NASA Astrophysics Data System (ADS)

    Yasui, Kanji; Arayama, Tatsuro; Okutani, Satoshi; Akahane, Tadashi

    2003-05-01

    Using the ammonia (NH 3) plasma generated by a helical antenna surrounded by two magnetic coils, the transition of the discharge mode from low-density plasma to high-density one was observed. At the transition, the emission intensities from the H atoms and NH radicals especially increased in the optical emission spectroscopy, while the intensities of the other emission lines also increased abruptly. The nitridation of gallium arsenide (GaAs) surface was performed using the high-density NH 3 plasma, and the properties of the nitrided surface layer were compared with those nitrided by high-density N 2 plasma using the same apparatus. From the spectroscopic ellipsometry measurements, the thickness of the nitrided layer was estimated to be 16-18 nm, while that by N 2 was 3-4 nm. From the Ga 3d spectra, the contamination with oxygen in the nitridation layer by NH 3 plasma was less than that by N 2 plasma.

  18. Device performance of in situ steam generated gate dielectric nitrided by remote plasma nitridation

    NASA Astrophysics Data System (ADS)

    Al-Shareef, H. N.; Karamcheti, A.; Luo, T. Y.; Bersuker, G.; Brown, G. A.; Murto, R. W.; Jackson, M. D.; Huff, H. R.; Kraus, P.; Lopes, D.; Olsen, C.; Miner, G.

    2001-06-01

    In situ steam generated (ISSG) oxides have recently attracted interest for use as gate dielectrics because of their demonstrated reliability improvement over oxides formed by dry oxidation. [G. Minor, G. Xing, H. S. Joo, E. Sanchez, Y. Yokota, C. Chen, D. Lopes, and A. Balakrishna, Electrochem. Soc. Symp. Proc. 99-10, 3 (1999); T. Y. Luo, H. N. Al-Shareef, G. A. Brown, M. Laughery, V. Watt, A. Karamcheti, M. D. Jackson, and H. R. Huff, Proc. SPIE 4181, 220 (2000).] We show in this letter that nitridation of ISSG oxide using a remote plasma decreases the gate leakage current of ISSG oxide by an order of magnitude without significantly degrading transistor performance. In particular, it is shown that the peak normalized transconductance of n-channel devices with an ISSG oxide gate dielectric decreases by only 4% and the normalized drive current by only 3% after remote plasma nitridation (RPN). In addition, it is shown that the reliability of the ISSG oxide exhibits only a small degradation after RPN. These observations suggest that the ISSG/RPN process holds promise for gate dielectric applications.

  19. Reactive DC magnetron sputtered zirconium nitride (ZrN) thin film and its characterization

    NASA Astrophysics Data System (ADS)

    Subramanian, B.; Ashok, K.; Sanjeeviraja, C.; Kuppusami, P.; Jayachandran, M.

    2008-05-01

    Zirconium nitride (ZrN) thin films were prepared by using reactive direct current (DC) magnetron sputtering onto different substrates. A good polycrystalline nature with face centered cubic structure was observed from X-ray Diffraction for ZrN thin films. The observed 'd' values from the X-ray Diffraction pattern were found to be in good agreement with the standard 'd' values (JCPDS-89-5269). An emission peak is observed at 587nm from Photoluminescence studies for the excitation at 430nm. The resistivity value (ρ) of 2.1798 (μΩ cm) was observed. ZrN has high wear resistance and low coefficient of friction. A less negative value of Ecorr and lower value of Icorr observed for ZrN / Mild Steel (MS) clearly confirm the better corrosion resistance than the bare substrate. Also the higher Rct value and lower Cdl value was observed for ZrN / MS from Nyquist - plot.

  20. Band gap effects of hexagonal boron nitride using oxygen plasma

    SciTech Connect

    Sevak Singh, Ram; Leong Chow, Wai; Yingjie Tay, Roland; Hon Tsang, Siu; Mallick, Govind; Tong Teo, Edwin Hang

    2014-04-21

    Tuning of band gap of hexagonal boron nitride (h-BN) has been a challenging problem due to its inherent chemical stability and inertness. In this work, we report the changes in band gaps in a few layers of chemical vapor deposition processed as-grown h-BN using a simple oxygen plasma treatment. Optical absorption spectra show a trend of band gap narrowing monotonically from 6 eV of pristine h-BN to 4.31 eV when exposed to oxygen plasma for 12 s. The narrowing of band gap causes the reduction in electrical resistance by ∼100 fold. The x-ray photoelectron spectroscopy results of plasma treated hexagonal boron nitride surface show the predominant doping of oxygen for the nitrogen vacancy. Energy sub-band formations inside the band gap of h-BN, due to the incorporation of oxygen dopants, cause a red shift in absorption edge corresponding to the band gap narrowing.

  1. Ion nitriding; Proceedings of the International Conference, Cleveland, OH, Sept. 15-17, 1986

    NASA Technical Reports Server (NTRS)

    Spalvins, T. (Editor)

    1987-01-01

    The present conference discusses plasma-assisted surface coating/modification processes, the applications to date of ion nitriding, the effects of nitrogen on metal surfaces, ion nitriding mechanisms in Cr, Al and Cr + Al-containing 1040 steel, ion nitriding of Al and its alloys, life enhancement for forging dies, novel anode plasma nitriding developments, and a comparative study of the pulsed and dc ion-nitriding behavior in specimens with blind holes. Also discussed are the influence of heating method on ion nitriding, surface hardening of marage steels by ion nitriding without core hardness reduction, plasma nitriding of nodular cast iron sput gears, NbN composites for superconductors, the carburization of tungsten in a glow discharge methane plasma, economic considerations concerning plasma nitriding, and the corrosion properties obtained by ion nitriding.

  2. Reactive Spark Plasma Sintering (SPS) of Nitride Reinforced Titanium Alloy Composites (Postprint)

    DTIC Science & Technology

    2014-08-15

    AFRL-RX-WP-JA-2014-0177 REACTIVE SPARK PLASMA SINTERING (SPS) OF NITRIDE REINFORCED TITANIUM ALLOY COMPOSITES (POSTPRINT) Jaimie S...titanium–vanadium alloys, has been achieved by introducing reactive nitrogen gas during the spark plasma sintering (SPS) of blended titanium and...lcomReactive spark plasma sintering (SPS) of nitride reinforced titanium alloy compositeshttp://dx.doi.org/10.1016/j.jallcom.2014.08.049 0925-8388

  3. Improving electrochemical properties of AISI 1045 steels by duplex surface treatment of plasma nitriding and aluminizing

    NASA Astrophysics Data System (ADS)

    Haftlang, Farahnaz; Habibolahzadeh, Ali; Sohi, Mahmoud Heydarzadeh

    2015-02-01

    Improvement in electrochemical behavior of AISI 1045 steel after applying aluminum nitride coating was investigated in 3.5% NaCl solution, using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) analyses. Aluminum nitride coating was applied on the steel surface by duplex treatment of pack aluminizing and plasma nitriding. Some specimens were plasma nitrided followed by aluminizing (PN-Al), while the others were pack aluminized followed by plasma nitriding (Al-PN). Topological and structural studies of the modified surfaces were conducted using scanning electron microscope (SEM) equipped by energy dispersive X-ray spectroscope (EDS), and X-ray diffractometer (XRD). The electrochemical measurements showed that the highest corrosion and polarization (Rp) resistances were obtained in PN-Al specimens, having single phase superficial layer of AlN. Pitting mechanism was dominant reason of lower corrosion resistance in the Al-PN specimens.

  4. Plasma enhanced atomic layer deposition of silicon nitride using neopentasilane

    SciTech Connect

    Weeks, Stephen Nowling, Greg; Fuchigami, Nobi; Bowes, Michael; Littau, Karl

    2016-01-15

    Progress in transistor scaling has increased the demands on the material properties of silicon nitride (SiN{sub x}) thin films used in device fabrication and at the same time placed stringent restrictions on the deposition conditions employed. Recently, low temperature plasma enhanced atomic layer deposition has emerged as a viable technique for depositing these films with a thermal budget compatible with semiconductor processing at sub-32 nm technology nodes. For these depositions, it is desirable to use precursors that are free from carbon and halogens that can incorporate into the film. Beyond this, it is necessary to develop processing schemes that minimize the wet etch rate of the film as it will be subjected to wet chemical processing in subsequent fabrication steps. In this work, the authors introduce low temperature deposition of SiN{sub x} using neopentasilane [NPS, (SiH{sub 3}){sub 4}Si] in a plasma enhanced atomic layer deposition process with a direct N{sub 2} plasma. The growth with NPS is compared to a more common precursor, trisilylamine [TSA, (SiH{sub 3}){sub 3 }N] at identical process conditions. The wet etch rates of the films deposited with NPS are characterized at different plasma conditions and the impact of ion energy is discussed.

  5. Manufacture of fully dense uranium nitride pellets using hydride derived powders with spark plasma sintering

    NASA Astrophysics Data System (ADS)

    Malkki, Pertti; Jolkkonen, Mikael; Hollmer, Tobias; Wallenius, Janne

    2014-09-01

    Applying a combination of hydriding/nitriding of metallic uranium with the spark plasma sintering technique, we show that uranium nitride pellets with an average porosity of 0.2% may be manufactured. This is considerably smaller than the lowest porosity previously reported in the literature. The high density is attained by sintering at 1650 °C for only three minutes.

  6. Plasma-assisted interface engineering of boron nitride nanostructure films.

    PubMed

    Pakdel, Amir; Bando, Yoshio; Golberg, Dmitri

    2014-10-28

    Today many aspects of science and technology are progressing into the nanoscale realm where surfaces and interfaces are intrinsically important in determining properties and performances of materials and devices. One familiar phenomenon in which interfacial interactions play a major role is the wetting of solids. In this work we use a facile one-step plasma method to control the wettability of boron nitride (BN) nanostructure films via covalent chemical functionalization, while their surface morphology remains intact. By tailoring the concentration of grafted hydroxyl groups, superhydrophilic, hydrophilic, and hydrophobic patterns are created on the initially superhydrophobic BN nanosheet and nanotube films. Moreover, by introducing a gradient of the functional groups, directional liquid spreading toward increasing [OH] content is achieved on the films. The resulting insights are meant to illustrate great potentials of this method to tailor wettability of ceramic films, control liquid flow patterns for engineering applications such as microfluidics and biosensing, and improve the interfacial contact and adhesion in nanocomposite materials.

  7. Surface Texturing-Plasma Nitriding Duplex Treatment for Improving Tribological Performance of AISI 316 Stainless Steel

    PubMed Central

    Lin, Naiming; Liu, Qiang; Zou, Jiaojuan; Guo, Junwen; Li, Dali; Yuan, Shuo; Ma, Yong; Wang, Zhenxia; Wang, Zhihua; Tang, Bin

    2016-01-01

    Surface texturing-plasma nitriding duplex treatment was conducted on AISI 316 stainless steel to improve its tribological performance. Tribological behaviors of ground 316 substrates, plasma-nitrided 316 (PN-316), surface-textured 316 (ST-316), and duplex-treated 316 (DT-316) in air and under grease lubrication were investigated using a pin-on-disc rotary tribometer against counterparts of high carbon chromium bearing steel GCr15 and silicon nitride Si3N4 balls. The variations in friction coefficient, mass loss, and worn trace morphology of the tested samples were systemically investigated and analyzed. The results showed that a textured surface was formed on 316 after electrochemical processing in a 15 wt % NaCl solution. Grooves and dimples were found on the textured surface. As plasma nitriding was conducted on a 316 substrate and ST-316, continuous and uniform nitriding layers were successfully fabricated on the surfaces of the 316 substrate and ST-316. Both of the obtained nitriding layers presented thickness values of more than 30 μm. The nitriding layers were composed of iron nitrides and chromium nitride. The 316 substrate and ST-316 received improved surface hardness after plasma nitriding. When the tribological tests were carried out under dry sliding and grease lubrication conditions, the tested samples showed different tribological behaviors. As expected, the DT-316 samples revealed the most promising tribological properties, reflected by the lowest mass loss and worn morphologies. The DT-316 received the slightest damage, and its excellent tribological performance was attributed to the following aspects: firstly, the nitriding layer had high surface hardness; secondly, the surface texture was able to capture wear debris, store up grease, and then provide continuous lubrication. PMID:28773996

  8. Surface Texturing-Plasma Nitriding Duplex Treatment for Improving Tribological Performance of AISI 316 Stainless Steel.

    PubMed

    Lin, Naiming; Liu, Qiang; Zou, Jiaojuan; Guo, Junwen; Li, Dali; Yuan, Shuo; Ma, Yong; Wang, Zhenxia; Wang, Zhihua; Tang, Bin

    2016-10-27

    Surface texturing-plasma nitriding duplex treatment was conducted on AISI 316 stainless steel to improve its tribological performance. Tribological behaviors of ground 316 substrates, plasma-nitrided 316 (PN-316), surface-textured 316 (ST-316), and duplex-treated 316 (DT-316) in air and under grease lubrication were investigated using a pin-on-disc rotary tribometer against counterparts of high carbon chromium bearing steel GCr15 and silicon nitride Si₃N₄ balls. The variations in friction coefficient, mass loss, and worn trace morphology of the tested samples were systemically investigated and analyzed. The results showed that a textured surface was formed on 316 after electrochemical processing in a 15 wt % NaCl solution. Grooves and dimples were found on the textured surface. As plasma nitriding was conducted on a 316 substrate and ST-316, continuous and uniform nitriding layers were successfully fabricated on the surfaces of the 316 substrate and ST-316. Both of the obtained nitriding layers presented thickness values of more than 30 μm. The nitriding layers were composed of iron nitrides and chromium nitride. The 316 substrate and ST-316 received improved surface hardness after plasma nitriding. When the tribological tests were carried out under dry sliding and grease lubrication conditions, the tested samples showed different tribological behaviors. As expected, the DT-316 samples revealed the most promising tribological properties, reflected by the lowest mass loss and worn morphologies. The DT-316 received the slightest damage, and its excellent tribological performance was attributed to the following aspects: firstly, the nitriding layer had high surface hardness; secondly, the surface texture was able to capture wear debris, store up grease, and then provide continuous lubrication.

  9. Effect of plasma nitriding treatment on structural, tribological and electrochemical properties of commercially pure titanium.

    PubMed

    Çelik, İlhan; Karakan, Mehmet

    2016-02-01

    In this study, plasma nitriding treatment was applied to commercially pure titanium (Grade 2). Structural properties, electrochemical and tribological behaviours of the nitrided pure titanium specimens were comparatively investigated. Microstructure and morphology of the plasma nitrided specimens were analysed by X-ray diffraction and scanning electron microscopy. Furthermore, corrosion tests were conducted in Ringer's solution, which represents a human body environment, to determine electrochemical properties. Then, tribological and frictional properties were investigated using pin-on-disc tribometer, and a micro-hardness tester was used to measure the hardness of the coatings. The results showed that plasma nitrided specimens exhibited higher surface hardness than the untreated specimens did. In addition, the plasma nitrided specimens at 700 °C presented significantly better performance than the other plasma nitrided specimens (at 500 °C and 600 °C) under dry wear conditions. Moreover, corrosion test results showed that corrosion behaviours of untreated and nitrided samples had similar characteristic. © IMechE 2015.

  10. Mechanical properties and biocompatibility of plasma-nitrided laser-cut 316L cardiovascular stents.

    PubMed

    Arslan, Erdem; Iğdil, Mustafa C; Yazici, Hilal; Tamerler, Candan; Bermek, Hakan; Trabzon, Levent

    2008-05-01

    The effect of surface modification of laser-cut 316L cardiovascular stents by low-T plasma nitriding was evaluated in terms of mechanical properties and biocompatibility of the stents. The plasma nitriding was performed at 400, 450 or 500 degrees C using various ratios of nitrogen-hydrogen gas mixtures. The flexibility and radial strength were measured in crimped and expanded state of the stents, respectively. The mechanical properties could be adjusted and improved by plasma nitriding conducted at temperatures lower than 450 degrees C and/or nitrogen content less than 10% in the treatment gas. An osteoblast cell culture model system was utilized to investigate the effect of plasma nitriding of the stents on the biological response towards the stents, using biological criteria such as cell viability, alkaline phosphatase and nitric oxide production. In terms of cell viability and alkaline phosphatase production, the plasma nitriding procedure did not appear to negatively affect the biocompatibility of the 316L steel stents. However, in terms of nitric oxide production that was slightly increased in the presence of the plasma-nitrided stents, an indirect improvement in the biocompatibility could possibly be expected.

  11. Plasma enhanced metalorganic chemical vapor deposition of amorphous aluminum nitride

    NASA Astrophysics Data System (ADS)

    Harris, H.; Biswas, N.; Temkin, H.; Gangopadhyay, S.; Strathman, M.

    2001-12-01

    Plasma enhanced deposition of amorphous aluminum nitride (AlN) using trimethylaluminum, hydrogen, and nitrogen was performed in a capacitively coupled plasma system. Temperature was varied from 350 to 550 °C, and pressure dependence of the film structure was investigated. Films were characterized by Fourier transform infrared, Rutherford backscattering (RBS), ellipsometry, and x-ray diffraction (XRD). The films are amorphous in nature, as indicated by XRD. Variations in the refractive index were observed in ellipsometric measurements, which is explained by the incorporation of carbon in the films, and confirmed by RBS. Capacitance-voltage, conductance-voltage (G-V), and current-voltage measurements were performed to reveal bulk and interface electrical properties. The electrical properties showed marked dependence on processing conditions of the AlN films. Clear peaks as observed in the G-V characteristics indicated that the losses are predominantly due to interface states. The interface state density ranged between 1010 and 1011eV-1 cm-2. Annealing in hydrogen resulted in lowering of interface state density values.

  12. Structure and properties of nitrided surface layer produced on NiTi shape memory alloy by low temperature plasma nitriding

    NASA Astrophysics Data System (ADS)

    Czarnowska, Elżbieta; Borowski, Tomasz; Sowińska, Agnieszka; Lelątko, Józef; Oleksiak, Justyna; Kamiński, Janusz; Tarnowski, Michał; Wierzchoń, Tadeusz

    2015-04-01

    NiTi shape memory alloys are used for bone and cardiological implants. However, on account of the metallosis effect, i.e. the release of the alloy elements into surrounding tissues, they are subjected to various surface treatment processes in order to improve their corrosion resistance and biocompatibility without influencing the required shape memory properties. In this paper, the microstructure, topography and morphology of TiN surface layer on NiTi alloy, and corrosion resistance, both before and after nitriding in low-temperature plasma at 290 °C, are presented. Examinations with the use of the potentiodynamic and electrochemical impedance spectroscopy methods were carried out and show an increase of corrosion resistance in Ringer's solution after glow-discharge nitriding. This surface titanium nitride layer also improved the adhesion of platelets and the proliferation of osteoblasts, which was investigated in in vitro experiments with human cells. Experimental data revealed that nitriding NiTi shape memory alloy under low-temperature plasma improves its properties for bone implant applications.

  13. Surface hardening of VT-22 alloy by inductively coupled plasma nitriding and magnetron deposition of TiN films

    NASA Astrophysics Data System (ADS)

    Kharkov, Maxim M.; Kaziev, Andrey V.; Tumarkin, Alexander V.; Drobinin, Vyacheslav E.; Stepanova, Tatiana V.; Pisarev, Alexander A.

    2017-01-01

    The surface of VT-22 Russian grade titanium alloy samples was modified by inductively coupled plasma (ICP) nitriding followed by magnetron deposition of TiN coatings. Different operating conditions of ICP nitriding and magnetron deposition were considered. The microhardness depth profiles were measured for samples after nitriding. The performance of TiN coatings was examined with a scratch tester.

  14. Dust structurization observed in a dc glow discharge dusty plasma

    NASA Astrophysics Data System (ADS)

    Heinrich, Jonathon R.; Kim, Su-Hyun; Merlino, Robert L.

    2010-11-01

    Dusty plasmas, which are inherently open systems which require an ionization source to replenish the plasma absorbed on the grains, tend to exhibit self-organization. Various structures have been observed in dusty plasmas such as dust crystals, voids, and vortices. Due to the presence of drifting ions in dc discharge plasmas, spontaneously excited dust acoustic waves are also a common occurrence. By adjusting the discharge parameters we have observed a new phenomenon in dusty plasmas -- the spontaneous formation of three-dimensional stationary dust density structures. These structures appear as an ordered pattern consisting of alternating regions of high and low dust density arranged in a nested bowl-type configuration The stationary structure evolves from dust density waves that slow down as their wavelength decreases and eventually stop moving when the wavelength reaches some minimum size.

  15. Study of atmospheric pressure plasma jet parameters generated by DC voltage driven cold plasma source

    NASA Astrophysics Data System (ADS)

    Wang, Xingxing; Shashurin, Alexey

    2017-08-01

    In this work, plasma and discharge parameters of a DC voltage driven cold plasma source were measured. The device exhibits a plasma jet with a length of 3 cm and a pulsation frequency of about 2.75 kHz. The peak current of each pulse was about 1.1 mA, and the duration was about 5 μs. The repetition rate could be increased by raising the DC voltage level. By utilizing the microwave scattering system, electron density in the plasma was measured to be about ˜1011 cm-3. Vibrational and rotational temperatures of atmospheric pressure plasma jets were also measured by optical emission spectroscopy. The vibrational temperature was measured to be 2850 K and rotational temperature to be 300 K at the applied voltage of 5 kV. No strong dependence of the temperatures was found with the DC voltage level.

  16. Spectroscopic diagnostics of active screen plasma nitriding processes: on the interplay of active screen and model probe plasmas

    NASA Astrophysics Data System (ADS)

    Hamann, S.; Börner, K.; Burlacov, I.; Spies, H.-J.; Röpcke, J.

    2015-09-01

    In a reactor used for active screen plasma nitriding (ASPN) the interplay of two plasma types, (i) the plasma of the cylindrical active screen driven in a pulsed dc mode (f = 1 kHz, 60% duty cycle) and (ii) the plasma at an internal model probe driven in a cw dc mode, ignited in a low pressure H2-N2 gas mixture (p = 3 mbar) containing small amounts of CH4 and CO2 have been studied by tunable diode laser infrared absorption (TDLAS) and optical emission spectroscopy (OES) techniques. Applying in situ TDLAS the evolution of the carbon containing precursors, CH4 and CO2, and of the reaction products, NH3, HCN, CO and H2O, has been monitored. The degree of dissociation of the carbon containing precursor molecules varied between 70% and 92%. The concentrations of the reaction products were found to be in the range 1012…1015 molecules cm-3. By analyzing the development of the molecular concentrations at changes of gas mixtures and plasma power values, it was found that (i) HCN and NH3 are the main products of plasma conversion in the case of methane admixture and (ii) CO, HCN and NH3 in the carbon dioxide case. The fragmentation efficiencies of methane and carbon dioxide (RF(CH4)  ≈  1…2   ×   1015 molecules J-1, RF(CO2)  ≈  0.5…1.0   ×   1016 molecules J-1) and the respective conversion efficiencies to the product molecules (R C(product) ≈ 1013-1015 molecules J-1) have been determined for different gas mixtures and plasma power values, while the influence of probe and screen plasmas, i.e. the phenomena caused by the interplay of both plasma sources, was analyzed. The additional usage of the plasma at the model probe has a sensitive influence on the generation of the reaction products, in particular that of NH3 and HCN. With the help of OES the rotational temperature of the screen plasma could be determined, which increases with power from 770 K to 950 K. Also with power the ionic component of nitrogen molecules, i

  17. Active screen plasma nitriding enhances cell attachment to polymer surfaces

    NASA Astrophysics Data System (ADS)

    Kaklamani, Georgia; Bowen, James; Mehrban, Nazia; Dong, Hanshan; Grover, Liam M.; Stamboulis, Artemis

    2013-05-01

    Active screen plasma nitriding (ASPN) is a well-established technique used for the surface modification of materials, the result of which is often a product with enhanced functional performance. Here we report the modification of the chemical and mechanical properties of ultra-high molecular weight poly(ethylene) (UHMWPE) using 80:20 (v/v) N2/H2 ASPN, followed by growth of 3T3 fibroblasts on the treated and untreated polymer surfaces. ASPN-treated UHMWPE showed extensive fibroblast attachment within 3 h of seeding, whereas fibroblasts did not successfully attach to untreated UHMWPE. Fibroblast-coated surfaces were maintained for up to 28 days, monitoring their metabolic activity and morphology throughout. The chemical properties of the ASPN-treated UHMWPE surface were studied using X-ray photoelectron spectroscopy, revealing the presence of Csbnd N, Cdbnd N, and Ctbnd N chemical bonds. The elastic modulus, surface topography, and adhesion properties of the ASPN-treated UHMWPE surface were studied over 28 days during sample storage under ambient conditions and during immersion in two commonly used cell culture media.

  18. dc-plasma-sprayed electronic-tube device

    DOEpatents

    Meek, T.T.

    1982-01-29

    An electronic tube and associated circuitry which is produced by dc plasma arc spraying techniques is described. The process is carried out in a single step automated process whereby both active and passive devices are produced at very low cost. The circuitry is extremely reliable and is capable of functioning in both high radiation and high temperature environments. The size of the electronic tubes produced are more than an order of magnitude smaller than conventional electronic tubes.

  19. Optical properties of silicon nitride films formed by plasma-chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Vlasukova, L. A.; Komarov, F. F.; Parkhomenko, I. N.; Milchanin, O. V.; Leont'ev, A. V.; Mudryi, A. V.; Togambaeva, A. K.

    2013-03-01

    The optical properties and structure of layers of silicon nitride deposited on silicon substrates by plasma-aided chemical vapor deposition at 300°C are studied by ellipsometry, Raman scattering, IR spectroscopy, and photoluminescence techniques. It is found that immediately after deposition the silicon nitride contains hydrogen in the form of Si-H bonds. Annealing (1100°C, 30 min) leads to dehydrogenation and densification of the nitride layer. An intense Si3N4 photoluminescence signal is detected in the green. Immediately after deposition the photoluminescence peak appears at 542 nm and annealing shifts it to shorter wavelengths.

  20. Numerical simulation of discharge plasma generation and nitriding the metals and alloys

    NASA Astrophysics Data System (ADS)

    Koval, T. V.; Manakov, R. A.; Nguyen Bao, Hung; Tran My, Kim An

    2017-01-01

    This research provides the numerical simulation of the plasma generation in a hollow cathode as well as the diffusion of nitrogen atoms into the metal in the low-pressure glow discharge plasma. The characteristics of the gas discharge were obtained and the relation of the basic technological parameters and the structural and phase state of the nitrided material were defined. Authors provided the comparison of calculations with the experimental results of titanium nitriding by low-pressure glow discharge plasma in a hollow cathode.

  1. Rolling Contact Fatigue Failure Mechanisms of Plasma-Nitrided Ductile Cast Iron

    NASA Astrophysics Data System (ADS)

    Wollmann, D.; Soares, G. P. P. P.; Grabarski, M. I.; Weigert, N. B.; Escobar, J. A.; Pintaude, G.; Neves, J. C. K.

    2017-05-01

    Rolling contact fatigue (RCF) of a nitrided ductile cast iron was investigated. Flat washers machined from a pearlitic ductile cast iron bar were quenched and tempered to maximum hardness, ground, polished and divided into four groups: (1) specimens tested as quenched and tempered; (2) specimens plasma-nitrided for 8 h at 400 °C; (3) specimens plasma-nitrided and submitted to a diffusion process for 16 h at 400 °C; and (4) specimens submitted to a second tempering for 24 h at 400 °C. Hardness profiles, phase analyses and residual stress measurements by x-ray diffraction, surface roughness and scanning electron microscopy were applied to characterize the surfaces at each step of this work. Ball-on-flat washer tests were conducted with a maximum contact pressure of 3.6 GPa, under flood lubrication with a SAE 90 API GL-5 oil at 50 °C. Test ending criterion was the occurrence of a spalling. Weibull analysis was used to characterize RCF's lifetime data. Plasma-nitrided specimens exhibited a shorter RCF lifetime than those just quenched and tempered. The effects of nitriding on the mechanical properties and microstructure of the ductile cast iron are discussed in order to explain the shorter endurance of nitrided samples.

  2. The effect of plasma-nitrided titanium surfaces on osteoblastic cell adhesion, proliferation, and differentiation.

    PubMed

    Ferraz, Emanuela P; Sa, Juliana C; de Oliveira, Paulo T; Alves, Clodomiro; Beloti, Marcio M; Rosa, Adalberto L

    2014-04-01

    In this study, we evaluated the effect of new plasma-nitrided Ti surfaces on the progression of osteoblast cultures, including cell adhesion, proliferation and differentiation. Ti surfaces were treated using two plasma-nitriding protocols, hollow cathode for 3 h (HC 3 h) and 1 h (HC 1 h) and planar for 1 h. Untreated Ti surfaces were used as control. Cells derived from human alveolar and rat calvarial bones were cultured on Ti surfaces for periods of up to 14 days and the following parameters were evaluated: cell morphology, adhesion, spreading and proliferation, alkaline phosphatase (ALP) activity, extracellular matrix mineralization, and gene expression of key osteoblast markers. Plasma-nitriding treatments resulted in Ti surfaces with distinct physicochemical characteristics. The cell adhesion and ALP activity were higher on plasma-nitrided Ti surfaces compared with untreated one, whereas cell proliferation and extracellular matrix mineralization were not affected by the treatments. In addition, the plasma-nitrided Ti surfaces increased the ALP, reduced the osteocalcin and did not affect the Runx2 gene expression. We have shown that HC 3 h and planar Ti surfaces slightly favored the osteoblast differentiation process, and then these surfaces should be considered for further investigation using preclinical models. Copyright © 2013 Wiley Periodicals, Inc.

  3. Nitrogen plasma instabilities and the growth of silicon nitride by electron cyclotron resonance microwave plasma chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Pool, F. S.

    1997-03-01

    Nitrogen plasma instabilities have been identified through fluctuations in the ion current density and substrate floating potential. The behavior of the plasma instabilities was found to be confined to the pressure regime 0.9 mTorrplasmas occurred following the transition from an underdense to overdense plasma, where an overdense plasma is defined for densities greater than the critical density nc=7.4×1010 cm-3. The instabilities are a consequence of the nonlinear dynamics present in electron cyclotron resonance (ECR) plasmas and indicative of a transition between plasma modes as the pressure increases from 0.9 to 1.6 mTorr. The plasma instabilities are suppressed with the introduction of silane for the deposition of silicon nitride, although the plasma still undergoes a transition from an underdense to overdense plasma at 1.0 mTorr. The transition pressure delineated regions of poor and optimum electrical properties of silicon nitride films deposited from a dilute nitrogen-silane (N2/SiH4=5) plasma. To evaluate growth conditions, the flux of energetic ions to deposited atoms was approximated by examination of the ratio of ion current density to deposition rate. This ratio was found to be well correlated to the electrical properties of ECR microwave plasma deposited silicon nitride films for pressures above the underdense to overdense transition at 1.0 mTorr.

  4. Corrosion resistance of zirconium oxynitride coatings deposited via DC unbalanced magnetron sputtering and spray pyrolysis-nitriding

    NASA Astrophysics Data System (ADS)

    Cubillos, G. I.; Bethencourt, M.; Olaya, J. J.

    2015-02-01

    ZrOxNy/ZrO2 thin films were deposited on stainless steel using two different methods: ultrasonic spray pyrolysis-nitriding (SPY-N) and the DC unbalanced magnetron sputtering technique (UBMS). Using the first method, ZrO2 was initially deposited and subsequently nitrided in an anhydrous ammonia atmosphere at 1023 K at atmospheric pressure. For UBMS, the film was deposited in an atmosphere of air/argon with a Φair/ΦAr flow ratio of 3.0. Structural analysis was carried out through X-ray diffraction (XRD), and morphological analysis was done through scanning electron microscopy (SEM) and atomic force microscopy (AFM). Chemical analysis was carried out using X-ray photoelectron spectroscopy (XPS). ZrOxNy rhombohedral polycrystalline film was produced with spray pyrolysis-nitriding, whereas using the UBMS technique, the oxynitride films grew with cubic Zr2ON2 crystalline structures preferentially oriented along the (2 2 2) plane. Upon chemical analysis of the surface, the coatings exhibited spectral lines of Zr3d, O1s, and N1s, characteristic of zirconium oxynitride/zirconia. SEM analysis showed the homogeneity of the films, and AFM showed morphological differences according to the deposition technique of the coatings. Zirconium oxynitride films enhanced the stainless steel's resistance to corrosion using both techniques. The protective efficacy was evaluated using electrochemical techniques based on linear polarization (LP). The results indicated that the layers provide good resistance to corrosion when exposed to chloride-containing media.

  5. Generation of low-temperature plasma by low-pressure arcs for synthesis of nitride coatings

    NASA Astrophysics Data System (ADS)

    Krysina, O. V.; Koval, N. N.; Lopatin, I. V.; Shugurov, V. V.; Kovalsky, S. S.

    2016-01-01

    Experiments were performed to study gas, metal, and mixed metal-gas plasmas. The plasmas were generated with the use of an arc evaporator and a gas-plasma source with a hot filament and hollow cathode that were operated independently or simultaneously. It has been revealed that the arc current of gas-plasma source affects the parameters of the metal-gas plasma and the element concentrations in the coatings. It has been demonstrated that the characteristics of the nitride coatings produced by plasma-assisted vacuum-arc deposition can be controlled by varying the parameters of the arc in the gas-plasma source.

  6. Properties of N-rich Silicon Nitride Film Deposited by Plasma-Enhanced Atomic Layer Deposition

    NASA Astrophysics Data System (ADS)

    Jhang, Pei-Ci; Lu, Chi-Pin; Shieh, Jung-Yu; Yang, Ling-Wu; Yang, Tahone; Chen, Kuang-Chao; Lu, Chih-Yuan

    2017-07-01

    An N-rich silicon nitride film, with a lower refractive index (RI) than the stoichiometric silicon nitride (RI = 2.01), was deposited by alternating the exposure of dichlorosilane (DCS, SiH2Cl2) and that of ammonia (NH3) in a plasma-enhanced atomic layer deposition (PEALD) process. In this process, the plasma ammonia was easily decomposed to reactive radicals by RF power activating so that the N-rich silicon nitride was easily formed by excited ammonia radicals. The growth kinetics of N-rich silicon nitride were examined at various deposition temperatures ranging from 400 °C to 630 °C; the activation energy (Ea) decreased as the deposition temperature decreased below 550 °C. N-rich silicon nitride film with a wide range of values of refractive index (RI) (RI = 1.86-2.00) was obtained by regulating the deposition temperature. At the optimal deposition temperature, the effects of RF power, NH3 flow rate and NH3 flow time were on the characteristics of the N-rich silicon nitride film were evaluated. The results thus reveal that the properties of the N-rich silicon nitride film that was formed by under plasma-enhanced atomic layer deposition (PEALD) are dominated by deposition temperature. In charge trap flash (CTF) study, an N-rich silicon nitride film was applied to MAONOS device as a charge-trapping layer. The films exhibit excellent electron trapping ability and favor a fresh cell data retention performance as the deposition temperature decreased.

  7. Particle and gas velocity measurements in a dc plasma jet

    SciTech Connect

    Lesinski, J.; Mizera-Lesinska, B.; Jurewicz, J.; Boulos, M.I.

    1980-01-01

    Measurements were made, using Laser Doppler Anemometry (LDA), of the velocity of 53 ..mu..m alumina particles as they are injected in a dc plasma jet operated with an argon-nitrogen mixture (18.9 l/min argon and 4.7 l/min nitrogen) at a power level of 15.2 kW. Results obtained at distances between 5 and 150 mm from the nozzle showed the particles to penetrate the plasma jet and attain the gas velocity at about 50 mm from their point of injection. Plasma velocity measurements in the core region of the jet proved to be particularly difficult. Limitations of the LDA system with regard to its spatial resolution and seeding requirements are discussed.

  8. Discharge Characteristics of DC Arc Water Plasma for Environmental Applications

    NASA Astrophysics Data System (ADS)

    Li, Tianming; Sooseok, Choi; Takayuki, Watanabe

    2012-12-01

    A water plasma was generated by DC arc discharge with a hafnium embedded rod-type cathode and a nozzle-type anode. The discharge characteristics were examined by changing the operation parameter of the arc current. The dynamic behavior of the arc discharge led to significant fluctuations in the arc voltage and its frequency. Analyses of the high speed image and the arc voltage waveform showed that the arc discharge was in the restrike mode and its frequency varied within several tens of kilohertz according to the operating conditions. The larger thermal plasma volume was generated by the higher flow from the forming steam with a higher restrike frequency in the higher arc current conditions. In addition, the characteristics of the water plasma jet were investigated by means of optical emission spectroscopy to identify the abundant radicals required in an efficient waste treatment process.

  9. Control of the stabilization of cubic boron nitride thin films deposited by unbalanced magnetron sputtering and dc pulsed substrate biasing

    NASA Astrophysics Data System (ADS)

    Otano-Rivera, Wilfredo

    The formation of cubic boron nitride (cBN) thin films deposited by unbalanced magnetron sputtering and dc pulsed substrate biasing has been studied. Thin films were deposited at different pressures and negative bias voltages to study the effect of the energetic bombardment on the stabilization conditions of the cubic phase of BN thin films. It is shown that it is possible to clearly define a stabilization window for cBN by controlling the sputtering deposition process parameters of pressure and negative substrate bias. It is also shown that at higher deposition pressures charge exchange and momentum transfer collisions in the plasma sheath reduce the bombardment energy of the particles. These collisional processes result in the use of a higher substrate bias voltages for increasing gas pressures in order to maintain the momentum per arriving boron atom, P/a, imparted to the growing film inside the stabilization window for the cubic phase. The end result is a trend where the substrate bias voltage for the formation of cBN increases negatively as a function of pressure times sheath thickness. A series of films were also deposited on different types of substrates in order to study the effects of chemistry and epitaxy on the nucleation of cBN. It was possible to nucleate the BN cubic phase on a wide variety of substrates. Diamond coated silicon substrates were the only ones that showed a marked effect on the nucleation of the cBN, where the FWHM of the FTIR signal was reduced two-fold as compared to the FTIR signal of films deposited on silicon under similar deposition conditions. The experimental results suggest that there is a threshold energy for the bombarding ions below which it is not possible to nucleate cBN. This result, in combination with the fact that P/a controls the cBN stabilization during the nucleation stage and other reported observations pertinent to the cBN thin film formation, leads to a proposed mechanism for the nucleation and growth stages of cBN.

  10. Sulfide Stress Cracking and Electrochemical Corrosion of Precipitation Hardening Steel After Plasma Oxy-Nitriding

    NASA Astrophysics Data System (ADS)

    Granda-Gutiérrez, E. E.; Díaz-Guillén, J. C.; Díaz-Guillén, J. A.; González, M. A.; García-Vázquez, F.; Muñóz, R.

    2014-09-01

    In this paper, we present the results of a duplex plasma nitriding followed by an oxidizing stage process (which is also referred as oxy-nitriding) on the corrosion behavior of a 17-4PH precipitation hardening stainless steel. The formation of both, expanded martensite (b.c.t. α'N-phase) and chromium oxide (type Cr2O3) in the subsurface of oxy-nitrided samples at specific controlled conditions, leads in a noticeable increasing in the time-to-rupture during the sulfide stress cracking test, in comparison with an untreated reference sample. Oxy-nitriding improves the corrosion performance of the alloy when it is immersed in solutions saturated by sour gas, which extends the application potential of this type of steel in the oil and gas extraction and processing industry. The presence of the oxy-nitrided layer inhibits the corrosion process that occurs in the near-surface region, where hydrogen is liberated after the formation of iron sulfides, which finally produces a fragile fracture by micro-crack propagation; the obtained results suggest that oxy-nitriding slows this process, thus delaying the rupture of the specimen. Moreover, oxy-nitriding produces a hard, sour gas-resistant surface, but do not significantly affect the original chloride ion solution resistance of the material.

  11. Characterization of low-temperature silicon nitride films produced by inductively coupled plasma chemical vapor deposition

    SciTech Connect

    Xu, Q.; Ra, Y.; Bachman, M.; Li, G. P.

    2009-01-15

    Silicon nitride films were synthesized at 170 deg. C by using inductively coupled plasma chemical vapor deposition under three microwave power conditions of 500, 800, and 1000 W. The chemical, physical and electrical properties of the deposited silicon nitride films were characterized by Fourier transform infrared, wet etching, atomic force microscopy, ellipsometry, J-V, and C-V measurements of metal-insulator-semiconductor. The microwave power for film deposition is found to play an important role at the films' properties. A high microwave power reduces the retention of hydrogen in a form of Si-H and N-H atomic bonds. The microwave power significantly affects the density of pin holes; the 800 W film has the lowest density of pin holes. In general, the low-temperature silicon nitride films possess better surface roughness than the conventional silicon nitride films produced at higher temperatures. The low-temperature silicon nitride films exhibit an abrupt breakdown, a characteristic of avalanche breakdown. The variation in breakdown strength is correlated with the change in pin-hole density, and the 800 W silicon nitride film possesses the highest breakdown strength. The microwave power has limited influences on leakage current and resistivity of the films. All the low-temperature silicon nitride films are characterized by high-density fixed charges and interface charge traps, of which both densities vary slightly with the microwave power for film deposition.

  12. Early stages of plasma induced nitridation of Si (111) surface and study of interfacial band alignment

    SciTech Connect

    Shetty, Satish; Shivaprasad, S. M.

    2016-02-07

    We report here a systematic study of the nitridation of the Si (111) surface by nitrogen plasma exposure. The surface and interface chemical composition and surface morphology are investigated by using RHEED, X-ray photoelectron spectroscopy, and atomic force microscopy (AFM). At the initial stage of nitridation two superstructures—“8 × 8” and “8/3 × 8/3”—form, and further nitridation leads to 1 × 1 stoichiometric silicon nitride. The interface is seen to have the Si{sup 1+} and Si{sup 3+} states of silicon bonding with nitrogen, which suggests an atomically abrupt and defect-free interface. The initial single crystalline silicon nitride layers are seen to become amorphous at higher thicknesses. The AFM image shows that the nitride nucleates at interfacial dislocations that are connected by sub-stoichiometric 2D-nitride layers, which agglomerate to form thick overlayers. The electrical properties of the interface yield a valence band offset that saturates at 1.9 eV and conduction band offset at 2.3 eV due to the evolution of the sub-stoichiometric interface and band bending.

  13. Sulfide Stress Cracking and Electrochemical Corrosion of Precipitation Hardening Steel After Plasma Oxy-Nitriding

    NASA Astrophysics Data System (ADS)

    Granda-Gutiérrez, E. E.; Díaz-Guillén, J. C.; Díaz-Guillén, J. A.; González, M. A.; García-Vázquez, F.; Muñóz, R.

    2014-11-01

    In this paper, we present the results of a duplex plasma nitriding followed by an oxidizing stage process (which is also referred as oxy-nitriding) on the corrosion behavior of a 17-4PH precipitation hardening stainless steel. The formation of both, expanded martensite (b.c.t. α'N-phase) and chromium oxide (type Cr2O3) in the subsurface of oxy-nitrided samples at specific controlled conditions, leads in a noticeable increasing in the time-to-rupture during the sulfide stress cracking test, in comparison with an untreated reference sample. Oxy-nitriding improves the corrosion performance of the alloy when it is immersed in solutions saturated by sour gas, which extends the application potential of this type of steel in the oil and gas extraction and processing industry. The presence of the oxy-nitrided layer inhibits the corrosion process that occurs in the near-surface region, where hydrogen is liberated after the formation of iron sulfides, which finally produces a fragile fracture by micro-crack propagation; the obtained results suggest that oxy-nitriding slows this process, thus delaying the rupture of the specimen. Moreover, oxy-nitriding produces a hard, sour gas-resistant surface, but do not significantly affect the original chloride ion solution resistance of the material.

  14. Tribological and corrosion properties of plasma nitrided and nitrocarburized 42CrMo4 steel

    NASA Astrophysics Data System (ADS)

    Kusmic, D.; Van Thanh, D.

    2017-02-01

    This article deals with tribological and corrosion resistance comparison of plasma nitrided and nitrocarburized 42CrMo4 steel used for breech mechanism in the armament production. Increasing of materials demands (like wear resistance, surface hardness, running-in properties and corrosion resistance) used for armament production and in other industrial application leads in the field of surface treatment. Experimental steel samples were plasma nitrided under different nitriding gas ratio at 500 °C for 15h and nitrocarburized for 45 min at temperature 590°C and consequently post-oxidized for 10 min at 430°C. Individual 42CrMo4 steel samples were subsequently metallographically evaluated and characterized by hardness and microhardness measuring. The wear test “ball on disc” was realized for measuring of adhesive wear and coefficient of friction during unlubricated sliding. NSS corrosion tests were realized for corrosion resistance evaluation and expressed by corroded area and calculated corrosion rate. The corrosion resistance evaluation is by the surface corrosion-free surfaces evaluation supplemented using the laser confocal microscopy. Due to different surface treatment and plasma nitriding conditions, there are wear resistance and corrosion resistance differences evident between the plasma nitrided steel samples as well.

  15. Temporally and Spatially Resolved Plasma Spectroscopy in Pulsed Laser Deposition of Ultra-Thin Boron Nitride Films (Postprint)

    DTIC Science & Technology

    2015-04-24

    in the plasma plume. Boron, being the lighter of the two species ( atomic weights: B¼ 10.81, N¼ 14.01), will escape the Knudsen layer of plasma plume...AFRL-RX-WP-JA-2016-0196 TEMPORALLY AND SPATIALLY RESOLVED PLASMA SPECTROSCOPY IN PULSED LASER DEPOSITION OF ULTRA-THIN BORON NITRIDE...AND SPATIALLY RESOLVED PLASMA SPECTROSCOPY IN PULSED LASER DEPOSITION OF ULTRA-THIN BORON NITRIDE FILMS (POSTPRINT) 5a. CONTRACT NUMBER FA8650

  16. Cold atmospheric plasma jet in an axial DC electric field

    NASA Astrophysics Data System (ADS)

    Lin, Li; Keidar, Michael

    2016-08-01

    Cold atmospheric plasma (CAP) jet is currently intensively investigated as a tool for new and potentially transformative cancer treatment modality. However, there are still many unknowns about the jet behavior that requires attention. In this paper, a helium CAP jet is tested in an electrostatic field generated by a copper ring. Using Rayleigh microwave scattering method, some delays of the electron density peaks for different ring potentials are observed. Meanwhile, a similar phenomenon associated with the bullet velocity is found. Chemical species distribution along the jet is analyzed based on the jet optical emission spectra. The spectra indicate that a lower ring potential, i.e., lower DC background electric field, can increase the amount of excited N2, N2+, He, and O in the region before the ring, but can decrease the amount of excited NO and HO almost along the entire jet. Combining all the results above, we discovered that an extra DC potential mainly affects the temporal plasma jet properties. Also, it is possible to manipulate the chemical compositions of the jet using a ring with certain electric potentials.

  17. Cold atmospheric plasma jet in an axial DC electric field

    SciTech Connect

    Lin, Li E-mail: keidar@gwu.edu; Keidar, Michael E-mail: keidar@gwu.edu

    2016-08-15

    Cold atmospheric plasma (CAP) jet is currently intensively investigated as a tool for new and potentially transformative cancer treatment modality. However, there are still many unknowns about the jet behavior that requires attention. In this paper, a helium CAP jet is tested in an electrostatic field generated by a copper ring. Using Rayleigh microwave scattering method, some delays of the electron density peaks for different ring potentials are observed. Meanwhile, a similar phenomenon associated with the bullet velocity is found. Chemical species distribution along the jet is analyzed based on the jet optical emission spectra. The spectra indicate that a lower ring potential, i.e., lower DC background electric field, can increase the amount of excited N{sub 2}, N{sub 2}{sup +}, He, and O in the region before the ring, but can decrease the amount of excited NO and HO almost along the entire jet. Combining all the results above, we discovered that an extra DC potential mainly affects the temporal plasma jet properties. Also, it is possible to manipulate the chemical compositions of the jet using a ring with certain electric potentials.

  18. Thermal stability of an ultrathin hafnium oxide film on plasma nitrided Si(100)

    NASA Astrophysics Data System (ADS)

    Skaja, K.; Schönbohm, F.; Weier, D.; Lühr, T.; Keutner, C.; Berges, U.; Westphal, C.

    2013-10-01

    We report on the thermal stability of an ultrathin hafnium oxide film on a plasma nitrided Si(100) surface. The ultrathin silicon nitride buffer layer was produced by an ECR-plasma ion source. Onto this buffer layer a thin hafnium oxide film was prepared by electron beam evaporation. The thermal stability of the layer stack was checked by systematic annealing steps. A detailed angle resolved X-ray photoelectron spectroscopy study of the interfaces is presented. For chemical surface studies high-resolution spectra of the Si 2p and Hf 4f signals were taken. It is demonstrated that the thermal stability of hafnium oxide thin films can be increased by a smooth and homogenous buffer layer of silicon nitride.

  19. Reactive Plasma Nitriding of AL2O3 Powder in Thermal Spray

    NASA Astrophysics Data System (ADS)

    Shahien, Mohammed; Yamada, Motohiro; Yasui, Toshiaki; Fukumoto, Masahiro

    Among advanced ceramics, aluminum nitride (AlN) had attracted much attention in the field of electrical and structural applications due to its outstanding properties. However, it is difficult to fabricate AlN coating by conventional thermal spray processes directly. Due to the thermal decomposition of feedstock AlN powder during spraying without a stable melting phase (which is required for deposition in thermal spray). Reactive plasma spraying (RPS) has been considered as a promising technology for in-situ formation of AlN thermally sprayed coatings. In this study the possibility of fabrication of AlN coating by reactive plasma nitriding of alumina (Al2O3) powder using N2/H2 plasma was investigated. It was possible to fabricate a cubic-AlN (c-AlN) based coating and the fabricated coating consists of c-AlN, α-Al2O3, Al5O6N and γ-Al2O3. It was difficult to understand the nitriding process from the fabricated coatings. Therefore, the Al2O3 powders were sprayed and collected in water. The microstructure observation of the collected powder and its cross section indicate that the reaction started from the surface. Thus, the sprayed particles were melted and reacted in high temperature reactive plasma and formed aluminum oxynitride which has cubic structure and easily nitride to c-AlN. During the coatings process the particles collide, flatten, and rapidly solidified on a substrate surface. The rapid solidification on the substrate surface due to the high quenching rate of the plasma flame prevents AlN crystal growth to form the hexagonal phase. Therefore, it was possible to fabricate c-AlN/Al2O3 based coatings through reactive plasma nitriding reaction of Al2O3 powder in thermal spray.

  20. Effect of Plasma Nitriding and Nitrocarburizing on HVOF-Sprayed Stainless Steel Coatings

    NASA Astrophysics Data System (ADS)

    Park, Gayoung; Bae, Gyuyeol; Moon, Kyungil; Lee, Changhee

    2013-12-01

    In this work, the effects of plasma nitriding (PN) and nitrocarburizing on HVOF-sprayed stainless steel nitride layers were investigated. 316 (austenitic), 17-4PH (precipitation hardening), and 410 (martensitic) stainless steels were plasma-nitrided and nitrocarburized using a N2 + H2 gas mixture and the gas mixture containing C2H2, respectively, at 550 °C. The results showed that the PN and nitrocarburizing produced a relatively thick nitrided layer consisting of a compound layer and an adjacent nitrogen diffusion layer depending on the crystal structures of the HVOF-sprayed stainless steel coatings. Also, the diffusion depth of nitrogen increased when a small amount of C2H2 (plasma nitrocarburizing process) was added. The PN and nitrocarburizing resulted in not only an increase of the surface hardness, but also improvement of the load bearing capacity of the HVOF-sprayed stainless steel coatings because of the formation of CrN, Fe3N, and Fe4N phases. Also, the plasma-nitrocarburized HVOF-sprayed 410 stainless steel had a superior surface microhardness and load bearing capacity due to the formation of Cr23C6 on the surface.

  1. Optimum temperature on corrosion resistance for plasma ion nitrided 316L stainless steel in sea water solution

    NASA Astrophysics Data System (ADS)

    Chong, Sang-Ok; Kim, Seong-Jong

    2017-01-01

    The aim of this research is to investigate the optimum plasma ion nitriding temperature on corrosion resistance in natural sea water for plasma ion nitrided 316L stainless steel. Plasma ion nitriding was conducted at different temperatures of 350, 400, 450, and 500 °C with a mixture of 75% of nitrogen and 25% of hydrogen during 10 h. In conclusion of anodic polarization test, a wide passive potential region and a high corrosion potential were observed at a plasma ion nitriding temperature of 450 °C. Moreover, relatively less damage depth and clean surface micrographs were observed at 450 °C as results of observation of three-dimensional (3D) microscope and scanning electron microscope (SEM) after polarization experiments. In addition, higher corrosion potential and lower corrosion current density were indicated at plasma ion nitrided samples than the value of untreated substrate after Tafel analysis. Hence, plasma ion nitrided at 450 °C in sea water solution represented optimum corrosion resistance among the all the plasma ion nitriding temperature parameters.

  2. Growing aluminum nitride films by Plasma-Enhanced Atomic Layer Deposition at low temperatures

    NASA Astrophysics Data System (ADS)

    Tarala, V. A.; Altakhov, A. S.; Martens, V. Ya; Lisitsyn, S. V.

    2015-11-01

    Aluminum nitride films have been grown by Plasma-Enhanced Atomic Layer Deposition method. It was found that at temperatures of 250 °C and 280 °C increase of the plasma exposure step duration over 6 s, as well as increase of reactor purge step duration over 1 s does not affect the growth rate, however, it affects the microstructure of the films. It was found that crystalline aluminum nitride films deposit with plasma exposure duration over 10 s and the reactor purging over 10 s. When the temperature drops the increase of reactor purge step duration and plasma exposure step duration over 20 s is required for crystalline AlN film growth.

  3. Effect of structural steel ion plasma nitriding on material durability in pulsed high magnetic fields

    NASA Astrophysics Data System (ADS)

    Spirin, A. V.; Krutikov, V. I.; Koleukh, D. S.; Mamaev, A. S.; Paranin, S. N.; Gavrilov, N. V.; Kaigorodov, A. S.

    2017-05-01

    The work was aimed to study the influence of plasma nitriding on electrical and mechanical properties of structural steels and their durability in pulsed high magnetic field. The plates and cylindrical magnetic flux concentrators were made of several steel grades (30KhGS, 40Kh, 50KhGA, 38Kh2MYuA, and U8A), heat-treated, and subjected to the low-temperature (400, 500°C) plasma nitriding. Electrical and mechanical properties of materials, phase composition of steel surface layer, microstructure and microhardness profiles were investigated on the plates before and after plasma treatment. Microstructure and microhardness profiles across the subsurface layer of plasma treated and untreated concentrators applied for high magnetic field generation were also studied. Magnetic field of 50 T under tens of microseconds in duration inside the flux concentrators was generated by long-life outer coil.

  4. Experimental and numerical study on plasma nitriding of AISI P20 mold steel

    NASA Astrophysics Data System (ADS)

    Nayebpashaee, N.; Vafaeenezhad, H.; Kheirandish, Sh.; Soltanieh, M.

    2016-09-01

    In this study, plasma nitriding was used to fabricate a hard protective layer on AISI P20 steel, at three process temperatures (450°C, 500°C, and 550°C) and over a range of time periods (2.5, 5, 7.5, and 10 h), and at a fixed gas N2:H2 ratio of 75vol%:25vol%. The morphology of samples was studied using optical microscopy and scanning electron microscopy, and the formed phase of each sample was determined by X-ray diffraction. The elemental depth profile was measured by energy dispersive X-ray spectroscopy, wavelength dispersive spectroscopy, and glow dispersive spectroscopy. The hardness profile of the samples was identified, and the microhardness profile from the surface to the sample center was recorded. The results show that ɛ-nitride is the dominant species after carrying out plasma nitriding in all strategies and that the plasma nitriding process improves the hardness up to more than three times. It is found that as the time and temperature of the process increase, the hardness and hardness depth of the diffusion zone considerably increase. Furthermore, artificial neural networks were used to predict the effects of operational parameters on the mechanical properties of plastic mold steel. The plasma temperature, running time of imposition, and target distance to the sample surface were all used as network inputs; Vickers hardness measurements were given as the output of the model. The model accurately reproduced the experimental outcomes under different operational conditions; therefore, it can be used in the effective simulation of the plasma nitriding process in AISI P20 steel.

  5. Plasma Nitriding of CP Titanium Grade-2 and Ti-6Al-4V Grade-5

    NASA Astrophysics Data System (ADS)

    Deepak, J. R.; Bupesh Raja, V. K.; Senthil Kumar, J.; Thomas, Subin; Raju Vithaiyathil, Thomas

    2017-05-01

    Titanium metal is considered to be asset material due to its high tribological properties. Since these tribological properties like hardness, roughness, wear resistance etc. are influenced by the surface properties of the material, so obviously any changes in the surface of the material has direct impact on the tribological properties too. Nitriding is a heat-treating process that diffuses nitrogen into the surface of a metal to create a case hardened surface. The main objective is that to implement the plasma nitriding process to both CP Titanium grade-2 and Ti-6Al-4V grade-5 and to observe the improvements in the tribological properties with respect to the parent materials.

  6. Ionized Magnetron Sputtering with a Coupled DC and Microwave Plasma

    NASA Astrophysics Data System (ADS)

    Hayden, D. B.; Green, K. M.; Juliano, D. R.; Ruzic, D. N.; Weiss, C. A.; Lantsman, A.; Ishii, J.

    1996-10-01

    A DC magnetron sputtering system is enhanced via an antenna microwave source. The ability of the microwaves to ionize the metal atoms from the aluminum target though electron impact and Penning ionization is studied as a function of microwave power, magnetron power, and pressure. A bias in the tens of volts (negative) is applied to the substrate and sample. This creates an electric field between the plasma and the substrate which is designed to draw the metal ions into the sample orthogonally for filling increased aspect ratio trenches. A quartz crystal oscillator is placed behind a gridded energy analyzer and embedded in the substrate. It determines the ion-to-neutral ratio and the deposition rate, and the gridded energy analyzer determines the energy spectrum of the ions, the ion current density, and the uniformity. These quantities are compared to the results of a computer simulation.

  7. Mesenchymal stem cell adhesion and spreading on microwave plasma-nitrided titanium alloy.

    PubMed

    Clem, William C; Konovalov, Valery V; Chowdhury, S; Vohra, Yogesh K; Catledge, Shane A; Bellis, Susan L

    2006-02-01

    Improved methods to increase surface hardness of metallic biomedical implants are being developed in an effort to minimize the formation of wear debris particles that cause local pain and inflammation. However, for many implant surface treatments, there is a risk of film delamination due to the mismatch of mechanical properties between the hard surface and the softer underlying metal. In this article, we describe the surface modification of titanium alloy (Ti-6Al-4V), using microwave plasma chemical vapor deposition to induce titanium nitride formation by nitrogen diffusion. The result is a gradual transition from a titanium nitride surface to the bulk titanium alloy, without a sharp interface that could otherwise lead to delamination. We demonstrate that vitronectin adsorption, as well as the adhesion and spreading of human mesenchymal stem cells to plasma-nitrided titanium is equivalent to that of Ti-6Al-4V, while hardness is improved 3- to 4-fold. These in vitro results suggest that the plasma nitriding technique has the potential to reduce wear, and the resulting debris particle release, of biomedical implants without compromising osseointegration; thus, minimizing the possibility of implant loosening over time. (c) 2005 Wiley Periodicals, Inc.

  8. Mesenchymal stem cell adhesion and spreading on microwave plasma-nitrided titanium alloy

    PubMed Central

    Clem, William C.; Konovalov, Valery V.; Chowdhury, S.; Vohra, Yogesh K.; Catledge, Shane A.; Bellis, Susan L.

    2008-01-01

    Improved methods to increase surface hardness of metallic biomedical implants are being developed in an effort to minimize the formation of wear debris particles that cause local pain and inflammation. However, for many implant surface treatments, there is a risk of film delamination due to the mismatch of mechanical properties between the hard surface and the softer underlying metal. In this article, we describe the surface modification of titanium alloy (Ti-6Al-4V), using microwave plasma chemical vapor deposition to induce titanium nitride formation by nitrogen diffusion. The result is a gradual transition from a titanium nitride surface to the bulk titanium alloy, without a sharp interface that could otherwise lead to delamination. We demonstrate that vitronectin adsorption, as well as the adhesion and spreading of human mesenchymal stem cells to plasma-nitrided titanium is equivalent to that of Ti-6Al-4V, while hardness is improved 3- to 4-fold. These in vitro results suggest that the plasma nitriding technique has the potential to reduce wear, and the resulting debris particle release, of biomedical implants without compromising osseointegration; thus, minimizing the possibility of implant loosening over time. PMID:16265649

  9. The effect of plasma nitriding and post oxidation on fretting wear behaviour of a high strength alloy steel

    NASA Astrophysics Data System (ADS)

    Prakash, N. Arun; Bennett, C. J.

    2017-05-01

    The fretting wear performance of the non-nitrided, nitrided and nitrided-post oxidized high strength alloy steel, W460 were investigated in the gross slip regime at ambient condition. Fretting wear tests were performed with an applied normal load of 250 and 650 N at a displacement amplitude of 100 μm using a cylinder-on-flat configuration. X-ray analysis (XRD) revealed the formation of the iron-nitrided Fe3N and Fe4N during plasma nitriding and iron oxide phases of hematite (Fe2O3) and magnetite (Fe3O4) during post-oxidation of the cylindrical steel samples. The steady state tangential force coefficient decreases when the nitrided and post-oxidized samples were fretted against the non-nitrided steel material when compared to the non-nitrided steel contact pair. The steady state tangential force coefficient decreased with an increase in applied normal load across all of the fretting conditions. The total dissipated energy and the total wear volume increased with an increase in applied normal load with total wear volume of the non-nitrided vs nitrided and non-nitrided vs nitrided post-oxidized sample pairs, showing a reduction in the wear volume of approximately 50% compared to the non-nitrided vs non-nitrided combination under the fretting conditions examined. The worn surface morphology of the fretted samples examined using a scanning electron microscope showed the presence of loose wear debris in the wear track, fragmented wear debris, delamination cracks, delamination with large discontinuities, plate-like wear debris, oxide patches and formation of large cavities.

  10. Deposition of titanium nitride and hydroxyapatite-based biocompatible composite by reactive plasma spraying

    NASA Astrophysics Data System (ADS)

    Roşu, Radu Alexandru; Şerban, Viorel-Aurel; Bucur, Alexandra Ioana; Dragoş, Uţu

    2012-02-01

    Titanium nitride is a bioceramic material successfully used for covering medical implants due to the high hardness meaning good wear resistance. Hydroxyapatite is a bioactive ceramic that contributes to the restoration of bone tissue, which together with titanium nitride may contribute to obtaining a superior composite in terms of mechanical and bone tissue interaction matters. The paper presents the experimental results in obtaining composite layers of titanium nitride and hydroxyapatite by reactive plasma spraying in ambient atmosphere. X-ray diffraction analysis shows that in both cases of powders mixtures used (10% HA + 90% Ti; 25% HA + 75% Ti), hydroxyapatite decomposition occurred; in variant 1 the decomposition is higher compared with the second variant. Microstructure of the deposited layers was investigated using scanning electron microscope, the surfaces presenting a lamellar morphology without defects such as cracks or microcracks. Surface roughness values obtained vary as function of the spraying distance, presenting higher values at lower thermal spraying distances.

  11. Gettering of interstitial iron in silicon by plasma-enhanced chemical vapour deposited silicon nitride films

    NASA Astrophysics Data System (ADS)

    Liu, A. Y.; Sun, C.; Markevich, V. P.; Peaker, A. R.; Murphy, J. D.; Macdonald, D.

    2016-11-01

    It is known that the interstitial iron concentration in silicon is reduced after annealing silicon wafers coated with plasma-enhanced chemical vapour deposited (PECVD) silicon nitride films. The underlying mechanism for the significant iron reduction has remained unclear and is investigated in this work. Secondary ion mass spectrometry (SIMS) depth profiling of iron is performed on annealed iron-contaminated single-crystalline silicon wafers passivated with PECVD silicon nitride films. SIMS measurements reveal a high concentration of iron uniformly distributed in the annealed silicon nitride films. This accumulation of iron in the silicon nitride film matches the interstitial iron loss in the silicon bulk. This finding conclusively shows that the interstitial iron is gettered by the silicon nitride films during annealing over a wide temperature range from 250 °C to 900 °C, via a segregation gettering effect. Further experimental evidence is presented to support this finding. Deep-level transient spectroscopy analysis shows that no new electrically active defects are formed in the silicon bulk after annealing iron-containing silicon with silicon nitride films, confirming that the interstitial iron loss is not due to a change in the chemical structure of iron related defects in the silicon bulk. In addition, once the annealed silicon nitride films are removed, subsequent high temperature processes do not result in any reappearance of iron. Finally, the experimentally measured iron decay kinetics are shown to agree with a model of iron diffusion to the surface gettering sites, indicating a diffusion-limited iron gettering process for temperatures below 700 °C. The gettering process is found to become reaction-limited at higher temperatures.

  12. Surface modification of 30CrNiMo8 low-alloy steel by active screen setup and conventional plasma nitriding methods

    NASA Astrophysics Data System (ADS)

    Ahangarani, Sh.; Sabour, A. R.; Mahboubi, F.

    2007-12-01

    In this paper, we report on a comparative study of active screen plasma nitriding (ASPN) and conventional dc plasma nitriding (CPN) behavior of 30CrNiMo8 low-alloy steel that has been examined under various process conditions. The process variables included active screen setup parameters (screen and iron plate top lids placed on the screen setup with 8 mm of hole size), treatment temperature (550 and 580 °C), gas mixture (75/25 and 25/75 of N 2/H 2) and treatment time (5 and 10 h) in 500 Pa pressure. The structure and phases composition of the diffusion zone and compound layer were studied by X-ray diffraction (XRD), microhardness tests, light optical microscopy and scanning electron microscopy (SEM). It was observed that treated sample surfaces in both CPN and ASPN methods consist of γ' and ɛ phases, and while the nitriding time and/or temperature increases, the intensity of ɛ phase in the compound layer will increase for ASPN and decrease for CPN method. Results show that the amount of nitrogen transferred from holes of screen toward the sample surface via sputtering and re-condensation mechanism can be affected due to the hardness and thickness of the layer.

  13. Formation of silicon nitride nanopillars in dual-frequency capacitively coupled plasma and their application to Si nanopillar etching

    SciTech Connect

    Park, C. K.; Kim, H. T.; Kim, D. Y.; Lee, N.-E.

    2007-07-15

    During the etching process of a silicon nitride layer in CH{sub 2}F{sub 2}/H{sub 2}/Ar dual-frequency superimposed capacitively coupled plasmas, CH{sub x}F{sub y} polymer nanodots were formed on the silicon nitride surface and, as a result, silicon nitride nanopillars were fabricated. The H{sub 2} and low frequency power (P{sub LF}) were found to play a critical role in determining the density and diameters of the pillars due to the change in the degree of hydrofluorocarbon polymerization. Silicon nitride nanopillars with a diameter as small as congruent with 25 nm and an aspect ratio as large as congruent with 3.2 were formed, and silicon nanopillars could also be fabricated by the inductively coupled Cl{sub 2}/Ar plasma etching of a Si substrate using the silicon nitride nanopillars as a hard mask.

  14. Some Temperature Effects on AISI-304 Nitriding in an Inductively Coupled RF Plasma

    SciTech Connect

    Valencia-Alvarado, R.; Barocio, S. R.; Mercado-Cabrera, A.; Pena-Eguiluz, R.; Munoz-Castro, A. E.; Piedad-Beneitez, A. de la; Rosa-Vazquez, J. de la; Lopez-Callejas, R.; Godoy-Cabrera, O. G.

    2006-12-04

    Some recent results obtained from nitriding AISI 304 stainless steel samples, 1.2 cm in diameter and 0.5 cm thick are reported here in the case of an 85% hydrogen and 15% nitrogen mixture work gas. The process was carried out from 300 to 400 W for (13.56 MHz) inductively coupled plasma within a 60 cm long pyrex glass tube 3.5 cm in diameter where the samples were biased up to -300 V with respect to earth. The resulting hardness appears to be a function of the substrate temperature which varied from 200 deg. C at a 0 V bias to 550 deg. C at -300 V. The plasma density at 400 W reached 3x1010 cm-3 with a 4 eV electron temperature. Prior to nitriding, all the samples were polished with 0.05 {mu}m diamond paste, leading to a 30 nm average roughness (Ra). After nitriding at -300 V, the Ra rose until {approx}400 nm while hardness values of 1500 HV under 300 g loads were measured. X ray diffraction indicates that the extended phase amplitude ({gamma}N), Fe and Cr nitride depends on the substrate temperature.

  15. TEM studies of plasma nitrided austenitic stainless steel.

    PubMed

    Stróz, D; Psoda, M

    2010-03-01

    Cross-sectional transmission electron microscopy and X-ray phase analysis were used to study the structure of a layer formed during nitriding the AISI 316L stainless steel at temperature 440 degrees C. It was found that the applied treatment led to the formation of 6-microm-thick layer of the S-phase. There is no evidence of CrN precipitation. The X-ray diffraction experiments proved that the occurred austenite lattice expansion - due to nitrogen atoms - depended on the crystallographic direction. The cross-sectional transmission electron microscopy studies showed that the layer consisted of a single cubic phase that contained a lot of defects such as dislocations, stacking faults, slip bands and twins. The high-resolution electron microscopy observations were applied to study the defect formation due to the nitriding process. It was shown that the presence of great number of stacking faults leads to formation of nanotwins. Weak, forbidden {100} reflections were still another characteristic feature of the S-phase. These were not detected in the X-ray spectra of the phase. Basing on the high-resolution electron microscopy studies it can be suggested that the short-range ordering of the nitrogen atoms in the octahedral sites inside the f.c.c. matrix lattice takes place and gives rise to appearance of these spots. It is suggested that the cubic lattice undergoes not only expansion but also slight rombohedral distortion that explains differences in the lattice expansion for different crystallographic directions.

  16. PIC/MCC simulation for magnetized capacitively coupled plasmas driven by combined dc/rf sources

    NASA Astrophysics Data System (ADS)

    Yang, Shali; Zhang, Ya; Jiang, Wei; Wang, Hongyu; Wang, Shuai

    2016-09-01

    Hybrid dc/rf capacitively coupled plasma (CCP) sources have been popular in substrate etching due to their simplicity in the device structure and better plasma property. In this work, the characteristics of magnetized capacitively coupled plasmas driven by combined dc/rf sources are described by a one-dimensional Particle-in-cell/Monte Carlo collision (PIC/MCC) model. The simulation is using a rf source of 13.56MHz in argon and at a low pressure of 50mTorr. The effects of dc voltage and magnetic field on the plasmas are examined for 200-400V and 0-200Gs. It is found that, to some extent, dc voltage will increase the plasma density, but plasma density drops with increasing dc voltage. The magnetic field will enhance the plasma density significantly, due to the magnetic field will increase the electron life time and decrease the loss to the electrodes. In the bulk plasma, electron temperature is increased with the magnetic field but decreased with the dc voltage. The electron temperature in sheath is higher than in bulk plasma, due to stochastic heating in sheath is greater than Ohmic heating in bulk plasma under low gas pressure. National Natural Science Foundation of China (11405067, 11105057, 11305032, 11275039).

  17. The effect of RF-DC plasma N2-H2 in the selective hardening process for micro-patterned AISI420

    NASA Astrophysics Data System (ADS)

    Herdianto, Hengky; Santjojo, D. J. Djoko H.; Masruroh

    2017-08-01

    The high density of RF-DC plasma N2-H2 was used to make precise micro-texturing onto AISI420 has complex textured geometry. The original 2D micro-patterns were drawn onto substrate surface by maskless patterning using by of nano-carbon ink. These micro-patterned specimens were further plasma-nitrided at 673 K for 5.4 ks by 70 Pa using the hollow cathode device. The emissive light spectroscopy shows species in plasma were nitrogen atoms together with NH radicals and nitrogen molecular ions. Unprinted surface areas had selectively nitrided, have high nitrogen solute contents up to 12 mass%. Masked area just corresponded to carbon-mapping from printed nano-carbon inks, while unprinted surface to nitrogen mapping. The hardness profile had stepwise change across the borders between these printed and unprinted areas; e.g., the hardness on unprinted surface was 1200 Hv while it remained to be 350 Hv on printed surface. This selective nitriding and hardening enabled to construct the 3D textured miniature dies and products by chemical etching of printed area. These two peaks were related to extended martensitic lattice by high nitrogen extraordinary solid solution. The phase transformation from martensitic lattice α'-Fe through expanded phase into ɛ-Fe3N lattice.

  18. Tungsten nitride coatings obtained by HiPIMS as plasma facing materials for fusion applications

    NASA Astrophysics Data System (ADS)

    Tiron, Vasile; Velicu, Ioana-Laura; Porosnicu, Corneliu; Burducea, Ion; Dinca, Paul; Malinský, Petr

    2017-09-01

    In this work, tungsten nitride coatings with nitrogen content in the range of 19-50 at% were prepared by reactive multi-pulse high power impulse magnetron sputtering as a function of the argon and nitrogen mixture and further exposed to a deuterium plasma jet. The elemental composition, morphological properties and physical structure of the samples were investigated by Rutherford backscattering spectrometry, atomic force microscopy and X-ray diffraction. Deuterium implantation was performed using a deuterium plasma jet and its retention in nitrogen containing tungsten films was investigated using thermal desorption spectrometry. Deuterium retention and release behaviour strongly depend on the nitrogen content in the coatings and the films microstructure. All nitride coatings have a polycrystalline structure and retain a lower deuterium level than the pure tungsten sample. Nitrogen content in the films acts as a diffusion barrier for deuterium and leads to a higher desorption temperature, therefore to a higher binding energy.

  19. Evaluation of the Effect of Different Plasma-Nitriding Parameters on the Properties of Low-Alloy Steel

    NASA Astrophysics Data System (ADS)

    Zdravecká, Eva; Slota, Ján; Solfronk, Pavel; Kolnerová, Michaela

    2017-07-01

    This work is concerned with the surface treatment (ion nitriding) of different plasma-nitriding parameters on the characteristics of DIN 1.8519 low-alloy steel. The samples were nitrided from 500 to 570 °C for 5-40 h using a constant 25% N2-75% H2 gaseous mixture. Lower temperature (500-520 °C) favors the formation of compound layers of γ' and ɛ iron nitrides in the surface layers, whereas a monophase γ'-Fe4 N layer can be obtained at a higher temperature. The hardness of this layer can be obtained when nitriding is performed at a higher temperature, and the hardness decreases when the temperature increases to 570 °C. These results indicate that pulsed plasma nitriding is highly efficient at 550 °C and can form thick and hard nitrided layers with satisfactory mechanical properties. The results show the optimized nitriding process at 540 °C for 20 h. This process can be an interesting means of enhancing the surface hardness of tool steels to forge dies compared to stamped steels with zinc coating with a reduced coefficient of friction and improving the anti-sticking properties of the tool surface.

  20. Effect of gas composition on corrosion behavior and growth of apatite on plasma nitrided titanium alloy Beta-21S

    NASA Astrophysics Data System (ADS)

    Mohan, L.; Anandan, C.

    2013-03-01

    Titanium alloy beta 21S with composition Ti-15Mo-3Nb-3Al-0.2Si was plasma nitrided using inductively coupled RF Plasma with 100% N2 and 80% N2-20% H2 at 800 °C for 4 h. XRD and micro Raman studies show the formation of titanium nitrides. Potentiodynamic polarization studies in Hank's solution show the corrosion resistance of the 80-20% (N2-H2) treated samples to be better than the 100% N2 treated samples. However, untreated samples show better corrosion resistance than the treated samples. Electrochemical impedance spectroscopy (EIS) studies show higher charge transfer resistance and lower double layer capacitance for the substrate compared to the nitrided samples. FESEM images of samples immersed in SBF show that growth of apatite is more and the size of deposits are larger on nitrided samples, especially on those nitrided with hydrogen dilution, as compared to that on the untreated substrate. EDS results show a decrease in nitrogen content and increase in oxygen content after corrosion experiments. XPS spectra from the nitrided and corrosion tested samples show the presence of oxide, nitride and oxynitride on the surface and after corrosion studies the samples are covered with oxide. Nitrided samples immersed in Hank's solution for one day show higher amount of calcium, phosphorous and oxygen in hydroxide form than the substrate.

  1. Plasma-enhanced CVD silicon nitride antireflection coatings for solar cells

    NASA Technical Reports Server (NTRS)

    Johnson, C. C.; Wydeven, T.; Donohoe, K.

    1983-01-01

    Multilayer plasma-enhanced chemical vapor deposition (PECVD) silicon nitride antireflection coatings were deposited on space quality silicon solar cells. Preliminary experiments indicated that multilayer coatings decreased the total reflectance of polished silicon from 35 percent to less than 3 percent over the spectral range 0.4-1.0 micron. The solar cell energy conversion efficiency was increased from an average of 8.84 percent to an average of 12.63 percent.

  2. Plasma-Enhanced Deposition of Silicon Nitride from SiH4-N2 Mixture

    NASA Astrophysics Data System (ADS)

    Katoh, Kazuhisa; Yasui, Masaru; Watanabe, Hideo

    1983-05-01

    Excellent silicon nitride films which can be used as the gate insulator of an a-Si FET are fabricated by RF glow-discharge of SiH4-N2-H2 gas mixtures. Resistivity of larger than 1× 1016 Ω\\cdotcm and breakdown strength of 6× 106 V/cm are realized. The optimum deposition conditions are evaluated and briefly discussed in connection with mechanisms of the plasma-enhanced deposition.

  3. Formation of Primary Amines on Silicon Nitride Surfaces: a Direct, Plasma-Based Pathway to Functionalization

    DTIC Science & Technology

    2007-01-19

    radio frequency glow discharge plasma fed with humidified air was examined by reaction with an amine-specific molecular label, fluorinated benzaldehyde ...nm of silicon nitride were purchased from Lance Goddard Associates (Foster City, CA). Glutaraldehyde, 4-(trifluoromethyl) benzaldehyde (TFMB...track the formation of primary amines on the surface with sub-monolayer sensitivity, a more easily detectable label is required. Benzaldehydes are known

  4. Structure and properties of commercially pure titanium nitrided in the plasma of a low-pressure gas discharge produced by a PINK plasma generator

    NASA Astrophysics Data System (ADS)

    Ivanov, Yu F.; Akhmadeev, Yu H.; Lopatin, I. V.; Petrikova, E. A.; Krysina, V.; Koval, N. N.

    2015-11-01

    The paper analyzes the surface structure and properties of commercially pure VT1-0 titanium nitrided in the plasma of a low-pressure gas discharge produced by a PINK plasma generator. The analysis demonstrates that the friction coefficient of the nitrided material decreases more than four times and its wear resistance and microhardness increases more than eight and three times, respectively. The physical mechanisms responsible for the enhancement of strength and tribological properties of the material are discussed.

  5. Reactive spark plasma sintering (SPS) of nitride reinforced titanium alloy composites

    SciTech Connect

    Borkar, Tushar; Nag, Soumya; Ren, Yang; Tiley, Jaimie; Banerjee, Rajarshi

    2014-12-25

    Coupled in situ alloying and nitridation of titanium–vanadium alloys, has been achieved by introducing reactive nitrogen gas during the spark plasma sintering (SPS) of blended titanium and vanadium elemental powders, leading to a new class of nitride reinforced titanium alloy composites. The resulting microstructure includes precipitates of the d-TiN phase with the NaCl structure, equiaxed (or globular) precipitates of a nitrogen enriched hcp a(Ti,N) phase with a c/a ratio more than what is expected for pure hcp Ti, and fine scale plate-shaped precipitates of hcp a-Ti, distributed within a bcc b matrix. During SPS processing, the d-TiN phase appears to form at a temperature of 1400 C, while only hcp a(Ti,N) and a-Ti phases form at lower processing temperatures. Consequently, the highest microhardness is exhibited by the composite processed at 1400 C while those processed at 1300 C or below exhibit lower values. Processing at temperatures below 1300 C, resulted in an incomplete alloying of the blend of titanium and vanadium powders. These d-TiN precipitates act as heterogeneous nucleation sites for the a(Ti,N) precipitates that appear to engulf and exhibit an orientation relationship with the nitride phase at the center. Furthermore, fine scale a-Ti plates are precipitated within the nitride precipitates, presumably resulting from the retrograde solubility of nitrogen in titanium.

  6. Effect of pulsed plasma nitriding on mechanical and tribological performance of Ck45 steel.

    PubMed

    Rastkar, A R; Kiani, A; Alvand, F; Shokri, B; Amirzadeh, M

    2011-06-01

    We studied the mechanical properties and wear performance of AISI 1045 (Ck45) carbon steel under the influence of pulsed plasma nitriding. The treatments were performed at temperatures of 500 and 550 degrees C in N2:H2 gas ratios of 1:3 and 3:1 and the working pressure of 10 mbar for 1 to 4 hours. Samples were examined by X-ray diffraction, optical, electron and atomic force microscopy, microhardness tests, roughness measurements and wear tests. Nitride layers were mainly composed of epsilon-(Fe2-3N) or gamma'-(Fe4N) depending on the gas ratio and/or temperature and time. When the nitriding time is increased, the composition of the compound layer varies from monophase gamma'-(Fe4N) to the two phase of epsilon-(Fe2-3N) and gamma'-(Fe4N). The highest thickness and hardness of the layers were obtained at 550 degrees C in the N2:H2 gas ratios of 3:1 for 4 h. The topographical evolution and surface roughness of the samples showed that all the roughness parameters increase with increasing the temperature. The friction coefficient of all samples was higher than that of untreated material. Wear performance of all nitrided samples was significantly better than that of untreated material.

  7. Residual gas analysis of a dc plasma for carbon nanofiber growth

    SciTech Connect

    Cruden, Brett A.; Cassell, Alan M.; Hash, David B.; Meyyappan, M.

    2004-11-01

    We report the analysis of a plasma enhanced chemical vapor deposition process for carbon nanofiber growth. A direct current (dc) plasma is employed with a mixture of acetylene and ammonia. Residual gas analysis is performed on the downstream plasma effluent to determine degrees of precursor dissociation and high molecular weight species formation. Results are correlated to growth quality obtained in the plasma as a function of dc voltage/power, gas mixture, and pressure. Behaviors in plasma chemistry are understood through application of a zero-dimensional model.

  8. [Automatic adjustment control system for DC glow discharge plasma source].

    PubMed

    Wan, Zhen-zhen; Wang, Yong-qing; Li, Xiao-jia; Wang, Hai-zhou; Shi, Ning

    2011-03-01

    There are three important parameters in the DC glow discharge process, the discharge current, discharge voltage and argon pressure in discharge source. These parameters influence each other during glow discharge process. This paper presents an automatic control system for DC glow discharge plasma source. This system collects and controls discharge voltage automatically by adjusting discharge source pressure while the discharge current is constant in the glow discharge process. The design concept, circuit principle and control program of this automatic control system are described. The accuracy is improved by this automatic control system with the method of reducing the complex operations and manual control errors. This system enhances the control accuracy of glow discharge voltage, and reduces the time to reach discharge voltage stability. The glow discharge voltage stability test results with automatic control system are provided as well, the accuracy with automatic control system is better than 1% FS which is improved from 4% FS by manual control. Time to reach discharge voltage stability has been shortened to within 30 s by automatic control from more than 90 s by manual control. Standard samples like middle-low alloy steel and tin bronze have been tested by this automatic control system. The concentration analysis precision has been significantly improved. The RSDs of all the test result are better than 3.5%. In middle-low alloy steel standard sample, the RSD range of concentration test result of Ti, Co and Mn elements is reduced from 3.0%-4.3% by manual control to 1.7%-2.4% by automatic control, and that for S and Mo is also reduced from 5.2%-5.9% to 3.3%-3.5%. In tin bronze standard sample, the RSD range of Sn, Zn and Al elements is reduced from 2.6%-4.4% to 1.0%-2.4%, and that for Si, Ni and Fe is reduced from 6.6%-13.9% to 2.6%-3.5%. The test data is also shown in this paper.

  9. N2 plasma etching processes of microscopic single crystals of cubic boron nitride

    NASA Astrophysics Data System (ADS)

    Tamura, Takahiro; Takami, Takuya; Yanase, Takashi; Nagahama, Taro; Shimada, Toshihiro

    2017-06-01

    We studied the N2 plasma etching of cubic boron nitride (cBN). We have developed experimental techniques for handling 200-µm-size single crystals for the preparation of surfaces with arbitrary crystal indexes, plasma processes, and surface analyses. We successfully prepared smooth surfaces of cBN with roughness smaller than 10 nm and found that the etching behavior was strongly influenced by the surface indexes. The morphology of the etched surfaces can be explained by the chemical stability of (111)B surfaces.

  10. Catalyst-free Indium Nitride Nanostructures Grown by Plasma-Assisted MOCVD

    NASA Astrophysics Data System (ADS)

    Norman, Dever; Hamad, Samir; Seo, Hye-Won

    2010-03-01

    The growth of Indium Nitride nanostructures directly on n-type Si (111) substrate was achieved without ammonia using nitrogen plasma as sole atomic nitrogen contribution. In this study we determine the growth conditions for optimal structural characteristics adjusting plasma generation power, substrate temperature, and III/V ratio. The structures formed nucleation sites directly interspersed on Si substrate without the use of hetero catalysis. SEM observations show that structurally the nanostructures range from narrow and horizontal with a high 1-dimensional consistency in width and length, to vertical and conical. Effects of the growth parameters along with the growth mechanism of nanostructures will be discussed.

  11. Melting and spheroidization of hexagonal boron nitride in a microwave-powered, atmospheric pressure nitrogen plasma `

    SciTech Connect

    Gleiman, S. S.; Phillips, J.

    2001-01-01

    We have developed a method for producing spherically-shaped, hexagonal phase boron nitride (hBN) particles of controlled diameter in the 10-100 micron size range. Specifically, platelet-shaped hBN particles are passed as an aerosol through a microwave-generated, atmospheric pressure, nitrogen plasma. In the plasma, agglomerates formed by collisions between input hBN particles, melt and forms spheres. We postulate that this unprecedented process takes place in the unique environment of a plasma containing a high N-atom concentration, because in such an environment the decomposition temperature can be raised above the melting temperature. Indeed, given the following relationship [1]: BN{sub (condensed)} {leftrightarrow} B{sub (gas)} + N{sub (gas)}. Standard equilibrium thermodynamics indicate that the decomposition temperature of hBN is increased in the presence of high concentrations of N atoms. We postulate that in our plasma system the N atom concentration is high enough to raise the decomposition temperature above the (undetermined) melting temperature. Keywords Microwave plasma, boron nitride, melting, spherical, thermodynamics, integrated circuit package.

  12. Study of the Characteristics of DC and ICP Hybrid Discharge Plasmas

    NASA Astrophysics Data System (ADS)

    WANG, Zhan; GAO, Wei; ZHANG, Peng; YAN, Huijie; REN, Chunsheng

    2015-03-01

    In this paper, the double-discharge plasma generated by radio frequency (RF) and direct current (DC) has been investigated. In comparison with their single-frequency counterpart, the interaction between the two excitations is significant and beneficial. The results show that the RF discharge can effectively increase the DC discharge current and decrease the DC voltage; meanwhile the DC discharge is favorable to feed abundant high energy seed electrons to the ICP discharge sustaining at 13.56 MHz for the latter to acquire higher plasma density and lower plasma potential by increasing the ionization rate. The innovative design has been demonstrated to facilitate more homogeneous performance with higher plasma density. supported by National Natural Science Foundation of China (No. 11475038)

  13. Manual modification and plasma exposure of boron nitride ceramic to study Hall effect thruster plasma channel material erosion

    NASA Astrophysics Data System (ADS)

    Satonik, Alexander J.

    Worn Hall effect thrusters (HET) show a variety of unique microstructures and elemental compositions in the boron nitride thruster channel walls. Worn thruster channels are typically created by running test thrusters in vacuum chambers for hundreds of hours. Studies were undertaken to manually modify samples of boron nitride without the use of a hall effect thruster. Samples were manually abraded with an abrasive blaster and sandpaper, in addition to a vacuum heater. Some of these samples were further exposed to a xenon plasma in a magnetron sputter device. Sandpaper and abrasive blaster tests were used to modify surface roughness values of the samples from 10,000 A to 150,000 A, matching worn thruster values. Vacuum heat treatments were performed on samples. These treatments showed the ability to modify chemical compositions of boron nitride samples, but not in a manner matching changes seen in worn thruster channels. Plasma erosion rate was shown to depend on the grade of the BN ceramic and the preparation of the surface prior to plasma exposure. Abraded samples were shown to erode 43% more than their pristine counterparts. Unique surface features and elemental compositions on the worn thruster channel samples were overwritten by new surface features on the ceramic grains. The microscope images of the ceramic surface show that the magnetron plasma source rounded the edges of the ceramic grains to closely match the worn HET surface. This effect was not as pronounced in studies of ion beam bombardment of the surface and appears to be a result of the quasi-neutral plasma environment.

  14. Plasma-Enhanced Atomic Layer Deposition of Silicon Nitride Using a Novel Silylamine Precursor.

    PubMed

    Park, Jae-Min; Jang, Se Jin; Yusup, Luchana L; Lee, Won-Jun; Lee, Sang-Ick

    2016-08-17

    We report the plasma-enhanced atomic layer deposition (PEALD) of silicon nitride thin film using a silylamine compound as the silicon precursor. A series of silylamine compounds were designed by replacing SiH3 groups in trisilylamine by dimethylaminomethylsilyl or trimethylsilyl groups to obtain sufficient thermal stability. The silylamine compounds were synthesized through redistribution, amino-substitution, lithiation, and silylation reactions. Among them, bis(dimethylaminomethylsilyl)trimethylsilyl amine (C9H29N3Si3, DTDN2-H2) was selected as the silicon precursor because of the lowest bond dissociation energy and sufficient vapor pressures. The energies for adsorption and reaction of DTDN2-H2 with the silicon nitride surface were also calculated by density functional theory. PEALD silicon nitride thin films were prepared using DTDN2-H2 and N2 plasma. The PEALD process window was between 250 and 400 °C with a growth rate of 0.36 Å/cycle. The best film quality was obtained at 400 °C with a RF power of 100 W. The PEALD film prepared showed good bottom and sidewall coverages of ∼80% and ∼73%, respectively, on a trench-patterned wafer with an aspect ratio of 5.5.

  15. Plasma-Enhanced Pulsed Laser Deposition of Wide Bandgap Nitrides for Space Power Applications

    NASA Technical Reports Server (NTRS)

    Triplett, G. E., Jr.; Durbin, S. M.

    2004-01-01

    The need for a reliable, inexpensive technology for small-scale space power applications where photovoltaic or chemical battery approaches are not feasible has prompted renewed interest in radioisotope-based energy conversion devices. Although a number of devices have been developed using a variety of semiconductors, the single most limiting factor remains the overall lifetime of the radioisotope battery. Recent advances in growth techniques for ultra-wide bandgap III-nitride semiconductors provide the means to explore a new group of materials with the promise of significant radiation resistance. Additional benefits resulting from the use of ultra-wide bandgap materials include a reduction in leakage current and higher operating voltage without a loss of energy transfer efficiency. This paper describes the development of a novel plasma-enhanced pulsed laser deposition system for the growth of cubic boron nitride semiconducting thin films, which will be used to construct pn junction devices for alphavoltaic applications.

  16. Mass spectroscopy of the ion flux produced during inductively coupled plasma nitriding process

    NASA Astrophysics Data System (ADS)

    Kolodko, D. V.; Kaziev, A. V.; Ageychenkov, D. G.; Meshcheryakova, E. A.; Pisarev, A. A.; Tumarkin, A. V.

    2017-05-01

    Ion fluxes on the surface of sample embedded in inductively coupled plasma have been studied in conditions typical for titanium alloy nitriding: total pressure 0.44 Pa, Ar/N2 = 70%/30%, and RF power 1500 W. The gas composition was independently monitored by the quadrupole analyser. The ion fluxes were sampled using a specially designed electrostatic extractor and then analysed with a magnetic sector mass-separator. The extractor design allowed us to apply a bias voltage to the plasma facing electrode thus imitating interaction of ions with the surface during the plasma processing. The ion fluxes of Ar+, {{{N}}}2{}+, and N+ on the surface were measured. The mass spectroscopy diagnostics unit is suitable for extensive ion content studies in the plasma technology facilities.

  17. Fabrication of boron nitride nanotube-gold nanoparticle hybrids using pulsed plasma in liquid.

    PubMed

    Ponraj, Sri balaji; Chen, Zhiqiang; Li, Lu Hua; Shankaranarayanan, Jayanth Suryanarayanan; Rajmohan, Gayathri Devi; du Plessis, Johan; Sinclair, Andrew J; Chen, Ying; Wang, Xungai; Kanwar, Jagat R; Dai, Xiujuan J

    2014-09-09

    Plasma, generated in liquid at atmospheric pressure by a nanosecond pulsed voltage, was used to fabricate hybrid structures from boron nitride nanotubes and gold nanoparticles in deionized water. The pH was greatly reduced, conductivity was significantly increased, and concentrations of reactive oxygen and nitrogen species in the water were increased by the plasma treatment. The treatment reduced the length of the nanotubes, giving more individual cuplike structures, and introduced functional groups onto the surface. Gold nanoparticles were successively assembled onto the functionalized surfaces. The reactive species from the liquid plasma along with the nanosecond pulsed electric field seem to play a role in the shortening and functionalization of the nanotubes and the assembly of gold nanoparticles. The potential for targeted drug delivery was tested in a preliminary investigation using doxorubicin-loaded plasma-treated nanotubes which were effective at killing ∼99% of prostate cancer cells.

  18. The Role of Activated Nitrogen Species on Double-folded Screen Nitriding Process

    NASA Astrophysics Data System (ADS)

    Kim, Sanggweon; Lee, Jaehoon; Saito, Nagahiro; Takai, Osamu

    2013-03-01

    As clean and energy saving surface hardening technology, plasma nitriding techniques have been evolved with object of higher performance in the last decades. Even though the diffusion of nitrogen inward to steel is occurred at the final step, solid diffusion from surface, energy transition from gas molecule of nitrogen to atomic or an activated state have many different steps depending on the plasma conditions, parameters and the design of each equipment. And this study made comparative on nitrogen sources transfer with conventional DC plasma nitriding and novel nitriding process using plasma diagnosis and metallurgical observation. With different vacuum pressure, gas ratio and new designed electrode (double-folded screen cathode electrode), it showed a different behavior of DC plasma nitriding including the nano-sized nitride on the outer surface of specimen due to nitrogen source of determining plasma species. In this study, plasma species was able to identify with optical emission spectroscopy (OES) studies. From these observations, we could understand better role of ions or neutral nitrogen species, like neutral nitrogen (N), N2+ and NHx radicals in plasma nitriding process with different parameters. And cutting layers of nitride specimen were showed the results due to a different species gas flow ratio or plasma conditions.

  19. Direct synthesis of metal nitride by CO2 or XeCl laser plasma

    NASA Astrophysics Data System (ADS)

    Boulmer-Leborgne, Chantal; Thomann, A. L.; Hermann, Joerg

    1994-09-01

    The present work deals with a new nitriding method applied to titanium: the Ti surface nitriding is carried out by direct laser irradiation in the presence of ambient nitrogen. The experimental procedure is performed in a chamber containing N2 gas, allowing plasma study by emission spectroscopy. Two pulsed laser types are used, a TEA-CO2 ((lambda) equals 10.6 micrometers ) and a XeCl excimer ((lambda) equals 308 nm) in order to compare the laser- material coupling influence on the layer synthesis process. The laser beam is focused perpendicularly to the Ti samples. Different experimental conditions are achieved to investigate the influence of laser and gas parameters on the process. Using the CO2 laser, a N2 plasma is created on the Ti surface. With the XeCl excimer laser, a Ti plasma on the sample appears. After treatment, the surface state of the samples is studied and chemical analysis of the targets are carried out. The TiN synthesis is evidenced. Presence of oxinitride in the compound and native surface oxygen reduction by hydrogen plasma are examined.

  20. Dynamics of runaway tails with time-dependent sub-Dreicer dc fields in magnetized plasmas

    SciTech Connect

    Moghaddam-Taaheri, E.; Vlahos, L.

    1987-10-01

    The evolution of runaway tails driven by sub-Dreicer time-dependent dc fields in a magnetized plasma are studied numerically using a quasilinear code based on the Ritz--Galerkin method and finite elements. It is found that the runaway tail maintained a negative slope during the dc field increase. Depending on the values of the dc electric field at t = 0 and the electron gyrofrequency to the plasma frequency ratio the runaway tail became unstable to the anomalous Doppler resonance or remained stable before the saturation of the dc field at some maximum value. The systems that remained stable during this stage became unstable to the anomalous Doppler or the C-hacekerenkov resonances when the dc field was kept at the saturation level or decreased. Once the instability is triggered, the runaway tail is isotropized.

  1. Dynamics of runaway tails with time-dependent sub-Dreicer dc fields in magnetized plasmas

    NASA Technical Reports Server (NTRS)

    Moghaddam-Taaheri, E.; Vlahos, L.

    1987-01-01

    The evolution of runaway tails driven by sub-Dreicer time-dependent dc fields in a magnetized plasma are studied numerically using a quasi-linear code based on the Ritz-Galerkin method and finite elements. It is found that the runaway tail maintained a negative slope during the dc field increase. Depending on the values of the dc electric field at t = 0 and the electron gyrofrequency to the plasma frequency ratio the runaway tail became unstable to the anomalous Doppler resonance or remained stable before the saturation of the dc field at some maximum value. The systems that remained stable during this stage became unstable to the anomalous Doppler or the Cerenkov resonances when the dc field was kept at the saturation level or decreased. Once the instability is triggered, the runaway tail is isotropized.

  2. Dynamics of runaway tails with time-dependent sub-Dreicer dc fields in magnetized plasmas

    NASA Technical Reports Server (NTRS)

    Moghaddam-Taaheri, E.; Vlahos, L.

    1987-01-01

    The evolution of runaway tails driven by sub-Dreicer time-dependent dc fields in a magnetized plasma are studied numerically using a quasi-linear code based on the Ritz-Galerkin method and finite elements. It is found that the runaway tail maintained a negative slope during the dc field increase. Depending on the values of the dc electric field at t = 0 and the electron gyrofrequency to the plasma frequency ratio the runaway tail became unstable to the anomalous Doppler resonance or remained stable before the saturation of the dc field at some maximum value. The systems that remained stable during this stage became unstable to the anomalous Doppler or the Cerenkov resonances when the dc field was kept at the saturation level or decreased. Once the instability is triggered, the runaway tail is isotropized.

  3. DC-SIGN and Influenza Hemagglutinin Dynamics in Plasma Membrane Microdomains Are Markedly Different

    PubMed Central

    Itano, Michelle S.; Neumann, Aaron K.; Liu, Ping; Zhang, Feng; Gratton, Enrico; Parak, Wolfgang J.; Thompson, Nancy L.; Jacobson, Ken

    2011-01-01

    DC-SIGN, a Ca2+-dependent transmembrane lectin, is found assembled in microdomains on the plasma membranes of dendritic cells. These microdomains bind a large variety of pathogens and facilitate their uptake for subsequent antigen presentation. In this study, DC-SIGN dynamics in microdomains were explored with several fluorescence microscopy methods and compared with dynamics for influenza hemagglutinin (HA), which is also found in plasma membrane microdomains. Fluorescence imaging indicated that DC-SIGN microdomains may contain other C-type lectins and that the DC-SIGN cytoplasmic region is not required for microdomain formation. Fluorescence recovery after photobleaching measurements showed that neither full-length nor cytoplasmically truncated DC-SIGN in microdomains appreciably exchanged with like molecules in other microdomains and the membrane surround, whereas HA in microdomains exchanged almost completely. Line-scan fluorescence correlation spectroscopy indicated an essentially undetectable lateral mobility for DC-SIGN but an appreciable mobility for HA within their respective domains. Single-particle tracking with defined-valency quantum dots confirmed that HA has significant mobility within microdomains, whereas DC-SIGN does not. By contrast, fluorescence recovery after photobleaching indicated that inner leaflet lipids are able to move through DC-SIGN microdomains. The surprising stability of DC-SIGN microdomains may reflect structural features that enhance pathogen uptake either by providing high-avidity platforms and/or by protecting against rapid microdomain endocytosis. PMID:21641311

  4. DC Plasma Synthesis of Vertically Aligned Carbon Nanofibers for Biointerfacing

    NASA Astrophysics Data System (ADS)

    Pearce, Ryan Christopher

    Vertically aligned carbon nanofibers (VACNFs) are a class of materials whose nanoscale dimensions and physical properties makes them uniquely suitable as functional elements in many applications for biodetection and biointerfacing on a cellular level. Control of VACNF synthesis by catalytic plasma enhanced chemical vapor deposition (PECVD) presents many challenges in integration into devices and structures designed for biointerfacing, such as transparent or flexible substrates. This dissertation addresses ways to overcome many of these issues in addition to deepening the fundamental understanding of nano-synthesis in catalytic PECVD. First, a survey of the field of VACNF synthesis and biointerfacing is presented, identifying the present challenges and greatest experimental applications. It is followed by experimental observations that elucidate the underlying mechanism to fiber alignment during synthesis, a critical step for deterministic control of fiber growth. Using a grid of electrodes patterned by photolithography on an insulating substrate, it was found that the alignment of the fibers is controlled by the anisotropic etching provided by ions during dc-PECVD synthesis. The VACNFs that have been utilized for many cellular interfacing experiments have unique mechanical and fluorescent properties due to a SiNx coating. The mechanism for SiNx deposition to VACNF sidewalls during synthesis is explored in addition to a detailed study of the optical properties of the coating. To explain the optical properties of this coating it is proposed that the source of photoluminescence for the SiNx coated VACNFs is quantum confinement effects due to the presence of silicon nanoclusters embedded in a Si3N4 matrix. These luminescent fibers have proven useful as registry markers in cell impalefection studies. To realize VACNF arrays used as an inflatable angioplasty balloon with embedded fibers to deliver drugs across the blood-brain barrier, a method for transferring fibers to

  5. Surface-charging effect of capacitively coupled plasmas driven by combined dc/rf sources

    SciTech Connect

    Zhang Quanzhi; Jiang Wei; Zhao Shuxia; Wang Younian

    2010-03-15

    The surface charging effect in hybrid dc/rf capacitively coupled plasmas is investigated by particle-in-cell/Monte Carlo simulations with an equivalent-circuit module. When the thickness of the dielectric is fixed, the self-bias dc voltage induced by the charge accumulated in the dielectric first increases and then decreases with increased dc voltage. The ratio of electron-to-ion charge flowing into the dielectric increases from -1.195 to -2.582. Increasing the dc voltage results in the number of high-energy ions bombarding the dielectric decreasing. The average electron energy at the dielectric decreases to the minimum value at the biggest self-bias dc voltage in the beginning and then rapidly increases. While fixing the dc source with thickening the dielectric, the self-bias dc voltage rises, but the charge ratio decreases. The average electron energy decreases monotonically and the ion-energy distributions (IEDs) at the dielectric are shifted toward the higher energy region. The results imply that the applied dc voltage may increase the electron flux and average energy to the dielectric at the cost of reduced etching rate, which may mitigate the notching effect. The applied dc voltage can also serve as a tool to modulate the ion IEDs. At the same time, a thicker dielectric will require higher applied dc voltage.

  6. Modification of Low-Alloy Steel Surface by Plasma Electrolytic Nitriding

    NASA Astrophysics Data System (ADS)

    Kusmanov, S. A.; Smirnov, A. A.; Silkin, S. A.; Belkin, P. N.

    2016-07-01

    The structure of the low-alloy steel after plasma electrolytic nitriding (PEN) in electrolyte containing ammonium nitrate was investigated. The cross-sectional microstructure, composition, and phase constituents of modified layer under different processing conditions were characterized. It is shown that anode PEN provides the saturation of steel with nitrogen and formation of α-Fe2O3, FeO, and Fe3O4 oxides, Fe2-3N nitride, and martensite. The aqueous solution that contained 15 wt.% NH4Cl and 5 wt.% NH4NO3 allows one to obtain the hardened layer with a thickness of 80 μm and a microhardness up to 740 HV during 5 min at 850 °C. Surface roughness decreases from 1.5 to 0.8 μm after 5-min PEN at 650 °C. The proposed electrolyte and processing mode (750 °C, 10 min) enable to obtain the decrease in the weight loss after lubricate wear testing by a factor of 2.7. The base-nitrate electrolyte conditioned a decrease in the corrosion current density by a factor of 9 due to passivating effect of the oxide and nitride of iron.

  7. Deposition of titanium nitride layers by electric arc - Reactive plasma spraying method

    NASA Astrophysics Data System (ADS)

    Şerban, Viorel-Aurel; Roşu, Radu Alexandru; Bucur, Alexandra Ioana; Pascu, Doru Romulus

    2013-01-01

    Titanium nitride (TiN) is a ceramic material which possesses high mechanical properties, being often used in order to cover cutting tools, thus increasing their lifetime, and also for covering components which are working in corrosive environments. The paper presents the experimental results on deposition of titanium nitride coatings by a new combined method (reactive plasma spraying and electric arc thermal spraying). In this way the advantages of each method in part are combined, obtaining improved quality coatings in the same time achieving high productivity. Commercially pure titanium wire and C45 steel as substrate were used for experiments. X-ray diffraction analysis shows that the deposited coatings are composed of titanium nitride (TiN, Ti2N) and small amounts of Ti3O. The microstructure of the deposited layers, investigated both by optical and scanning electron microscopy, shows that the coatings are dense, compact, without cracks and with low porosity. Vickers microhardness of the coatings presents maximum values of 912 HV0.1. The corrosion tests in 3%NaCl solution show that the deposited layers have a high corrosion resistance compared to unalloyed steel substrate.

  8. Nitrogen-Plasma-Activated Hierarchical Nickel Nitride Nanocorals for Energy Applications.

    PubMed

    Ouyang, Bo; Zhang, Yongqi; Zhang, Zheng; Fan, Hong Jin; Rawat, Rajdeep Singh

    2017-09-01

    Developing transition metal nitrides with unique nanomorphology is important for many energy storage and conversion processes. Here, a facile and novel one-step approach of growing 3D hierarchical nickel nitride (hNi3 N) on Ni foam via nitrogen plasma is reported. Different from most conventional chemical synthesis, the hNi3 N is obtained in much shorter growth duration (≤15 min) without any hazardous or reactive sources and oxide precursors at a moderate reaction zone temperature of ≤450 °C. Among possible multifunctionalities of the obtained nanocoral hNi3 N, herein the performance in reversible lithium ion storage and electrocatalytic oxygen evolution reaction (OER) is demonstrated. The as-obtained hNi3 N delivers a considerable cycling performance and rate stability as a lithium ion battery anode, and its property can be further enhanced by coating the hNi3 N surface with graphene quantum dots. The hNi3 N also serves as an active OER catalyst with high activity and stability. Additionally, on the basis of controlled growth under different nitrogen plasma treatment time, the formation mechanism of the nanocoralline hNi3 N is outlined for further extension to other materials. The results on time- and energy-efficient nitrogen-plasma-based preparation of hNi3 N pave the way for the development of high-performance metal nitride electrodes for energy storage and conversion. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Effects of ROS and RNS in non-equilibrium plasma enhanced oxidizing and nitriding

    NASA Astrophysics Data System (ADS)

    Datsyuk, Vitaly; Izmailov, Igor; Naumov, Vadym; Khomich, Vladimir; Tsiolko, Vyacheslav

    2016-09-01

    Plasma enhanced oxidizing and nitriding processes are of great interest for physics and applications. However, despite all advances in plasma technology, mechanisms of non-equilibrium plasma chemistry are not quite clear, particularly concerning reactive oxygen and nitrogen species (ROS/RNS) in metastable states. We tried to study this matter more detail. Experiments were done in a low temperature magnetron with a non-self-sustained glow discharge in oxygen/nitrogen/argon mixtures, employing electrical and optical diagnostics. Measurements showed that plasma processing is accompanied by the formation of electronically excited particles ROS/RNS. Computer modeling by using 0D-kinetic and 1D-fluid models including ionization, excitation, dissociation-recombination, vibrational relaxation, collisional quenching and radiation revealed the most probable mechanisms of plasma-chemical transformations. Effects of metastables of singlet oxygen O2*(a,b)and nitrogen N2*(A)as well as small but important radicals O*(1 D), N*(2 D) were also examined. Our study confirms the role of ROS/RNS in plasma kinetics and indicates the way toward more efficient oxygen and nitrogen plasma processing.

  10. Investigation on Plasma Jet Flow Phenomena During DC Air Arc Motion in Bridge-Type Contacts

    NASA Astrophysics Data System (ADS)

    Zhai, Guofu; Bo, Kai; Chen, Mo; Zhou, Xue; Qiao, Xinlei

    2016-05-01

    Arc plasma jet flow in the air was investigated under a bridge-type contacts in a DC 270 V resistive circuit. We characterized the arc plasma jet flow appearance at different currents by using high-speed photography, and two polished contacts were used to search for the relationship between roughness and plasma jet flow. Then, to make the nature of arc plasma jet flow phenomena clear, a simplified model based on magnetohydrodynamic (MHD) theory was established and calculated. The simulated DC arc plasma was presented with the temperature distribution and the current density distribution. Furthermore, the calculated arc flow velocity field showed that the circular vortex was an embodiment of the arc plasma jet flow progress. The combined action of volume force and contact surface was the main reason of the arc jet flow. supported by National Natural Science Foundation of China (Nos. 51307030, 51277038)

  11. Thermal and Kerr nonlinear properties of plasma-deposited silicon nitride/ silicon dioxide waveguides.

    PubMed

    Ikeda, Kazuhiro; Saperstein, Robert E; Alic, Nikola; Fainman, Yeshaiahu

    2008-08-18

    We introduce and present experimental evaluations of loss and nonlinear optical response in a waveguide and an optical resonator, both implemented with a silicon nitride/ silicon dioxide material platform prepared by plasma-enhanced chemical vapor deposition with dual frequency reactors that significantly reduce the stress and the consequent loss of the devices. We measure a relatively small loss of approximately 4dB/cm in the waveguides. The fabricated ring resonators in add-drop and all-pass arrangements demonstrate quality factors of Q=12,900 and 35,600. The resonators are used to measure both the thermal and ultrafast Kerr nonlinearities. The measured thermal nonlinearity is larger than expected, which is attributed to slower heat dissipation in the plasma-deposited silicon dioxide film. The n2 for silicon nitride that is unknown in the literature is measured, for the first time, as 2.4 x 10(-15)cm(2)/W, which is 10 times larger than that for silicon dioxide.

  12. Friction and wear of plasma-deposited amorphous hydrogenated films on silicon nitride

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa

    1991-01-01

    An investigation was conducted to examine the friction and wear behavior of amorphous hydrogenated carbon (a-C:H) films in sliding contact with silicon nitride pins in both dry nitrogen and humid air environments. Amorphous hydrogenated carbon films approximately 0.06 micron thick were deposited on silicon nitride flat substrates by using the 30 kHz ac glow discharge of a planar plasma reactor. The results indicate that an increase in plasma deposition power gives an increase in film density and hardness. The high-density a-C:H films deposited behaved tribologically much like bulk diamond. In the dry nitrogen environment, a tribochemical reaction produced a substance, probably a hydrocarbon-rich layer, that decreased the coefficient of friction. In the humid air environment, tribochemical interactions drastically reduced the wear life of a-C:H films and water vapor greatly increased the friction. Even in humid air, effective lubrication is possible with vacuum-annealed a-C:H films. The vacuum-annealed high-density a-C:H film formed an outermost superficial graphitic layer, which behaved like graphite, on the bulk a-C:H film. Like graphite, the annealed a-C:H film with the superficial graphitic layer showed low friction when adsorbed water vapor was present.

  13. A mathematical model and simulation results of plasma enhanced chemical vapor deposition of silicon nitride films

    NASA Astrophysics Data System (ADS)

    Konakov, S. A.; Krzhizhanovskaya, V. V.

    2015-01-01

    We developed a mathematical model of Plasma Enhanced Chemical Vapor Deposition (PECVD) of silicon nitride thin films from SiH4-NH3-N2-Ar mixture, an important application in modern materials science. Our multiphysics model describes gas dynamics, chemical physics, plasma physics and electrodynamics. The PECVD technology is inherently multiscale, from macroscale processes in the chemical reactor to atomic-scale surface chemistry. Our macroscale model is based on Navier-Stokes equations for a transient laminar flow of a compressible chemically reacting gas mixture, together with the mass transfer and energy balance equations, Poisson equation for electric potential, electrons and ions balance equations. The chemical kinetics model includes 24 species and 58 reactions: 37 in the gas phase and 21 on the surface. A deposition model consists of three stages: adsorption to the surface, diffusion along the surface and embedding of products into the substrate. A new model has been validated on experimental results obtained with the "Plasmalab System 100" reactor. We present the mathematical model and simulation results investigating the influence of flow rate and source gas proportion on silicon nitride film growth rate and chemical composition.

  14. High energy electron fluxes in dc-augmented capacitively coupled plasmas I. Fundamental characteristics

    SciTech Connect

    Wang Mingmei; Kushner, Mark J.

    2010-01-15

    Power deposition from electrons in capacitively coupled plasmas (CCPs) has components from stochastic heating, Joule heating, and from the acceleration of secondary electrons through sheaths produced by ion, electron, or photon bombardment of electrodes. The sheath accelerated electrons can produce high energy beams which, in addition to producing excitation and ionization in the gas can penetrate through the plasma and be incident on the opposite electrode. In the use of CCPs for microelectronics fabrication, there may be an advantage to having these high energy electrons interact with the wafer. To control the energy and increase the flux of the high energy electrons, a dc bias can be externally imposed on the electrode opposite the wafer, thereby producing a dc-augmented CCP (dc-CCP). In this paper, the characteristics of dc-CCPs will be discussed using results from a computational study. We found that for a given rf bias power, beams of high energy electrons having a narrow angular spread (<1 deg. ) can be produced incident on the wafer. The maximum energy in the high energy electron flux scales as {epsilon}{sub max}=-V{sub dc}+V{sub rf}+V{sub rf0}, for a voltage on the dc electrode of V{sub dc}, rf voltage of V{sub rf}, and dc bias on the rf electrode of V{sub rf0}. The dc current from the biased electrode must return to ground through surfaces other than the rf electrode and so seeks out a ground plane, typically the side walls. If the side wall is coated with a poorly conducting polymer, the surface will charge to drive the dc current through.

  15. Submicrometre particle filtration with a dc activated plasma textile

    NASA Astrophysics Data System (ADS)

    Rasipuram, S. C.; Wu, M.; Kuznetsov, I. A.; Kuznetsov, A. V.; Levine, J. F.; Jasper, W. J.; Saveliev, A. V.

    2014-01-01

    Plasma textiles are novel fabrics incorporating the advantages of cold plasma and low-cost non-woven or woven textile fabrics. In plasma textiles, electrodes are integrated into the fabric, and a corona discharge is activated within and on the surface of the fabric by applying high voltages above 10 kV between the electrodes. When the plasma textile is activated, submicrometre particles approaching the textile are charged by the deposition of ions and electrons produced by the corona, and then collected by the textile material. A stable plasma discharge was experimentally verified on the surface of the textile that was locally smooth but not rigid. A filtration efficiency close to 100% was observed in experiments conducted on salt particles with diameters ranging from 50 to 300 nm. Unlike conventional fibrous filters, the plasma textile provided uniform filtration in this range, without exhibiting a maximum particle penetration size.

  16. Microstructure and Properties of Plasma-Nitrided Fe-Based Superalloy Fe-25Ni-15Cr

    NASA Astrophysics Data System (ADS)

    Xu, Xiaolei; Yu, Zhiwei; Hou, Caiyun; Song, Weixiu; Wang, Yingzhu

    2017-07-01

    Fe-based superalloy Fe-25Ni-15Cr was plasma nitrided at a low temperature of 723 K (450 °C). The nitrided layer was characterized by optical microscopy (OPM) and scanning electron microscopy (SEM) and X-ray diffraction (XRD) through stepwise mechanical polishing and transmission electron microscopy (TEM). The results indicated that the double expanded austenite ( γ N1 and γ N2) was developed on the nitrided surface. Energy-dispersive X-ray spectrum (EDS) revealed that separate expanded austenite layers with distinctly different nitrogen contents occurred: high (18.98 to 11.49 at. pct) in the surface layer and low (5.87 to 5.32 at. pct) in the subsurface. XRD analysis indicated that large lattice expansion and distortion relative to the untreated austenite of an idea face-centered-cubic (fcc) structure occurred on the γ N1, but low expansion and less distortion on the γ N2. No obvious lattice distortion on the γ N1 was determined by calculating its electron diffraction pattern (EDP), except for detectable lattice expansion. Inconformity between XRD and EDP results suggested that the high compressive residual stress in the γ N1 was mainly responsible for the lattice distortion of the γ N1. TEM indicated that the γ N1 layer exhibited the monotonous contrast characteristic of an amorphous phase contrast to some extent, and corresponding EDP showed a strong diffuse scattering effect. It was suggested that the pre-precipitation took place in the γ N1 in the form of strongly bonded Cr-N clusters or pairs. Decomposition of the γ N1 into CrN and γ occurred at the grain boundaries, and the orientation of both phases remained cubic and cubic relationship, i.e., the planes and the directions with identical Miller indices in both phases were parallel. The nitrided surface was found to have significantly improved wear resistance. Further, the nitrided surface showed no adverse effect in the corrosion resistance but slight improvement in the 3.5 pct NaCl solution.

  17. Gallium nitride nanoneedles grown in extremely non-equilibrium nitrogen plasma

    SciTech Connect

    Mangla, O.; Roy, S.

    2016-05-23

    In the present work, gallium nitride (GaN) nanoneedles are grown on quartz substrates using the high fluence ions of GaN produced by hot, dense and extremely non-equlibrium nitrogen plasma in a modified dense plasma focus device. The formation of nanoneedles is obtained from the scanning electron microscopy with mean size of the head of nanoneedles ~ 70 nm. The nanoneedles are found to be poly-crystalline when studied structurally through the X-ray diffraction. The optical properties of nanoneedles studied using absorption spectra which show more absorption for nanoneedles depsoited one shot of ions irradiation. In addition, the band gap of nanoneedles is found to be increased as compared to bulk GaN. The obtained nanoneedles with increased band gap have potential applications in detector systems.

  18. Trap density of GeNx/Ge interface fabricated by electron-cyclotron-resonance plasma nitridation

    NASA Astrophysics Data System (ADS)

    Fukuda, Yukio; Otani, Yohei; Toyota, Hiroshi; Ono, Toshiro

    2011-07-01

    We have investigated GeNx/Ge interface properties using Si3N4(7 nm)/GeNx(2 nm)/Ge metal-insulator-semiconductor structures fabricated by the plasma nitridation of Ge substrates using an electron-cyclotron-resonance-generated nitrogen plasma. The interface trap density (Dit) measured by the conductance method is found to be distributed symmetrically in the Ge band gap with a minimum Dit value lower than 3 × 1011 cm-2eV-1 near the midgap. This result may lead to the development of processes for the fabrication of p- and n-Ge Schottky-barrier (SB) source/drain metal-insulator-semiconductor field-effect transistors using chemically and thermally robust GeNx dielectrics as interlayers for SB source/drain contacts and high-κ gate dielectrics.

  19. Inductively coupled plasma reactive ion etching of III-nitride semiconductors

    NASA Astrophysics Data System (ADS)

    Shah, A. P.; Laskar, M. R.; Rahman, A. A.; Gokhale, M. R.; Bhattacharya, A.

    2013-02-01

    III-Nitride semiconductor materials are resistant to most wet chemical etch processes, and hence the only viable alternative is to use dry etching for device processing. However, the conventional Reactive Ion Etching (RIE) process results in very slow etch-rates because of low reactive ion density, and larger surface damage due to high energy ion bombardment. Using Inductively Coupled Plasma (ICP) RIE, a very fast etch-rate and smooth morphology is achieved due to independent control of ion density and ion energy. In this paper, we present our results on ICP-RIE of epitaxial III-N materials, namely c-plane and a-plane oriented GaN, AlN, AlxGa1-xN using various chlorine plasma chemistries based on Cl2 and BCl3. We have examined the role of BCl3 deoxidising pre-treatment on the etching of AlGaN alloys.

  20. Synthesis of boron-nitride nanocages and fullerenes in a BN plasma

    NASA Astrophysics Data System (ADS)

    Krstic, Predrag; Han, Longtao

    2016-09-01

    Synthesis of boron-nitride fullerenes, nano-cocoons and nano-cages by self-organization of BN molecules in a high-temperature plasma is simulated using the DFT tight-binding method. No boron nano-cluster or catalysts nano-particle are needed to initiate this process. By varying the plasma temperature and the BN density, as well as the time of growth we can simulate growth of he sp2 cages of various shape, size and quality. Role of hydrogen in HBNH and H2BNH2 synthesis is also considered. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

  1. International Conference on Nitride Semiconductors (10th) Held in Washington, DC on August 25-30, 2013

    DTIC Science & Technology

    2014-08-17

    Nitrides, Optical Properties of Nitrides, Optical Properties of Quantum Wells , and Visible Quantum Dots. There were 7 invited presentations, 81...causes current droop? Are the narrow quantum wells the problem?"), F. Schubert (RPI, US, What cause current droop? Will better designs solve the...High-quality In-rich InGaN- based Multiple- quantum - well Structures by High-pressure Metalorganic Vapor Phase Epitaxy 12:15 pm-1:00 pm Jiirgen

  2. Comparison of pulsating DC and DC power air-water plasma jet: A method to decrease plume temperature and increase ROS

    NASA Astrophysics Data System (ADS)

    Liu, K.; Hu, H.; Lei, J.; Hu, Y.; Zheng, Z.

    2016-12-01

    Most air-water plasma jets are rich in hydroxyl radicals (•OH), but the plasma has higher temperatures, compared to that of pure gas, especially when using air as working gas. In this paper, pulsating direct current (PDC) power was used to excite the air-water plasma jet to reduce plume temperature. In addition to the temperature, other differences between PDC and DC plasma jets are not yet clear. Thus, comparative studies of those plasmas are performed to evaluate characteristics, such as breakdown voltage, temperature, and reactive oxygen species. The results show that the plume temperature of PDC plasma is roughly 5-10 °C lower than that of DC plasma in the same conditions. The •OH content of PDC is lower than that of DC plasma, whereas the O content of PDC plasma is higher. The addition of water leads in an increase in the plume temperature and in the production of •OH with two types of power supplies. The production of O inversely shows a declining tendency with higher water ratio. The most important finding is that the PDC plasma with 100% water ratio achieves lower temperature and more abundant production of •OH and O, compared with DC plasma with 0% water ratio.

  3. Diagnostics of ballistic electrons in a DC/RF hybrid capacitively coupled plasma reactor

    NASA Astrophysics Data System (ADS)

    Xu, Lin; Chen, Lee; Ranjan, Alok; Funk, Merritt; Bravenec, Ron; Economou, Demetre; Donnelly, Vincent; Sundararajan, Radha

    2008-10-01

    The DC/RF hybrid is a capacitively coupled plasma etcher with RF voltage on the bottom electrode and negative DC bias on the upper electrode. This configuration can significantly alleviate the electron shading effect and preserve photoresist integrity during plasma etching. It is thought that a group of ballistic electrons is responsible for these results. These high-energy electrons start as secondaries emitted from the negatively-biased DC electrode and accelerate across the DC sheath. They acquire high enough energy in the sheath such that they can cross the bulk plasma without gas-phase collisions. The ballistic electrons either strike the RF electrode or are trapped in the plasma bulk depending on the RF phase. Two gridded energy analyzers mounted on the back of the RF electrode were used to determine the energy distribution of ballistic electrons. The dependence of the ballistic electron energy distribution on DC voltage, pressure and RF power will be presented and compared with simulation results.

  4. Atomic Layer Deposition of Silicon Nitride from Bis(tert-butylamino)silane and N2 Plasma.

    PubMed

    Knoops, Harm C M; Braeken, Eline M J; de Peuter, Koen; Potts, Stephen E; Haukka, Suvi; Pore, Viljami; Kessels, Wilhelmus M M

    2015-09-09

    Atomic layer deposition (ALD) of silicon nitride (SiNx) is deemed essential for a variety of applications in nanoelectronics, such as gate spacer layers in transistors. In this work an ALD process using bis(tert-butylamino)silane (BTBAS) and N2 plasma was developed and studied. The process exhibited a wide temperature window starting from room temperature up to 500 °C. The material properties and wet-etch rates were investigated as a function of plasma exposure time, plasma pressure, and substrate table temperature. Table temperatures of 300-500 °C yielded a high material quality and a composition close to Si3N4 was obtained at 500 °C (N/Si=1.4±0.1, mass density=2.9±0.1 g/cm3, refractive index=1.96±0.03). Low wet-etch rates of ∼1 nm/min were obtained for films deposited at table temperatures of 400 °C and higher, similar to that achieved in the literature using low-pressure chemical vapor deposition of SiNx at >700 °C. For novel applications requiring significantly lower temperatures, the temperature window from room temperature to 200 °C can be a solution, where relatively high material quality was obtained when operating at low plasma pressures or long plasma exposure times.

  5. Adhesion, friction, and wear of plasma-deposited thin silicon nitride films at temperatures to 700 C

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Pouch, J. J.; Alterovitz, S. A.; Pantic, D. M.; Johnson, G. A.

    1988-01-01

    The adhesion, friction, and wear behavior of silicon nitride films deposited by low- and high-frequency plasmas (30 kHz and 13.56 MHz) at various temperatures to 700 C in vacuum were examined. The results of the investigation indicated that the Si/N ratios were much greater for the films deposited at 13.56 MHz than for those deposited at 30 kHz. Amorphous silicon was present in both low- and high-frequency plasma-deposited silicon nitride films. However, more amorphous silicon occurred in the films deposited at 13.56 MHz than in those deposited at 30 kHz. Temperature significantly influenced adhesion, friction, and wear of the silicon nitride films. Wear occurred in the contact area at high temperature. The wear correlated with the increase in adhesion and friction for the low- and high-frequency plasma-deposited films above 600 and 500 C, respectively. The low- and high-frequency plasma-deposited thin silicon nitride films exhibited a capability for lubrication (low adhesion and friction) in vacuum at temperatures to 500 and 400 C, respectively.

  6. Formation of Expanded Austenite on a Cold-Sprayed AISI 316L Coating by Low-Temperature Plasma Nitriding

    NASA Astrophysics Data System (ADS)

    Adachi, Shinichiro; Ueda, Nobuhiro

    2015-12-01

    Low-temperature plasma nitriding at temperatures below 450 °C is commonly applied to austenitic stainless steels to enhance wear resistance, while maintaining corrosion resistance, by forming expanded austenite (known as the S-phase). In this work, low-temperature plasma nitriding of cold-sprayed AISI 316L coatings was examined. A cold-spray technique was developed to produce metal coatings with less oxidation. However, the cold-sprayed AISI 316L coating obtained by use of nitrogen gas as propellant contained many interconnected pores and cracks, and was, consequently, unsuitable as an anticorrosive coating. Therefore, laser post-treatment was used to modify the coating and increase its density to similar to that of bulk steel. The anticorrosive performance of this coating on a carbon steel substrate in NaCl solution was substantially improved. Subsequent low-temperature plasma nitriding enhanced the wear resistance by two orders of magnitude. It is concluded that cold-sprayed AISI 316L coatings treated by laser post-treatment and subsequent low-temperature plasma nitriding could be used as protective coatings under severe wear and corrosion conditions.

  7. Spectroscopic investigations of plasma nitriding processes: A comparative study using steel and carbon as active screen materials

    NASA Astrophysics Data System (ADS)

    Hamann, S.; Burlacov, I.; Spies, H.-J.; Biermann, H.; Röpcke, J.

    2017-04-01

    Low-pressure pulsed DC H2-N2 plasmas were investigated in the laboratory active screen plasma nitriding monitoring reactor, PLANIMOR, to compare the usage of two different active screen electrodes: (i) a steel screen with the additional usage of CH4 as carbon containing precursor in the feeding gas and (ii) a carbon screen without the usage of any additional gaseous carbon precursor. Applying the quantum cascade laser absorption spectroscopy, the evolution of the concentration of four stable molecular species, NH3, HCN, CH4, and C2H2, has been monitored. The concentrations were found to be in a range of 1012-1016 molecules cm-3. By analyzing the development of the molecular concentrations at variations of the screen plasma power, a similar behavior of the monitored reaction products has been found for both screen materials, with NH3 and HCN as the main reaction products. When using the carbon screen, the concentration of HCN and C2H2 was 30 and 70 times higher, respectively, compared to the usage of the steel screen with an admixture of 1% CH4. Considering the concentration of the three detected hydrocarbon reaction products, a combustion rate of the carbon screen of up to 69 mg h-1 has been found. The applied optical emission spectroscopy enabled the determination of the rotational temperature of the N2+ ion which has been in a range of 650-900 K increasing with the power in a similar way in the plasma of both screens. Also with power the ionic component of nitrogen molecules, represented by the N2+ (0-0) band of the first negative system, as well as the CN (0-0) band of the violet system increase strongly in relation to the intensity of the neutral nitrogen component, i.e., the N2 (0-0) band of the second positive system. In addition, steel samples have been treated with both the steel and the carbon screen resulting in a formation of a compound layer of up to 10 wt. % nitrogen and 10 wt. % carbon, respectively, depending on the screen material.

  8. Tribocorrosion studies of metallic biomaterials: The effect of plasma nitriding and DLC surface modifications.

    PubMed

    Zhao, Guo-Hua; Aune, Ragnhild E; Espallargas, Nuria

    2016-10-01

    The medical grade pure titanium, stainless steel and CoCrMo alloy have been utilized as biomaterials for load-bearing orthopedic prosthesis. The conventional surgery metals suffer from a combined effect of wear and corrosion once they are implanted, which may significantly accelerate the material degradation process. In this work, the tribocorrosion performance of the metallic biomaterials with different surface modifications was studied in the simulated body fluid for the purpose of investigating the effect of the surface treatments on the tribocorrosion performance and eventually finding the most suitable implantation materials. The metals were subjected to surface modifications by plasma nitriding in different treatment temperatures or physical vapor deposition (PVD) to produce diamond-like carbon (DLC) coating, respectively. The dry wear and tribocorrosion properties of the samples were evaluated by using a reciprocating ball-on-disc tribometer equipped with an electrochemical cell. Prior to the tribocorrosion tests, their electrochemical behavior was measured by the potentiodynamic polarization in phosphate buffer saline (PBS) solution at room temperature. Both stainless steel and CoCrMo after low temperature nitriding kept their passive nature by forming an expanded austenite phase. The DLC coated samples presented the low anodic corrosion current due to the chemical inertness of the carbon layer. During the tribocorrosion tests at open circuit potential, the untreated and low temperature nitrided samples exhibited significant potential drop towards the cathodic direction, which was a result of the worn out of the passive film. Galvanic coupling was established between the depassivated (worn) area and the still passive (unworn) area, making the materials suffered from wear-accelerated corrosion. The DLC coating performed as a solid lubricant in both dry wear and tribocorrosion tests, and the resulting wear after the tests was almost negligible. Copyright

  9. Spatially-resolved spectral image of a microwave-induced plasma with Okamoto-cavity for nitridation of steel substrate.

    PubMed

    Sato, Shigeo; Arai, Yuuki; Wagatsuma, Kazuaki

    2014-01-01

    When a nitrogen microwave-induced plasma produced with an Okamoto-cavity was employed as a source for the nitridation of steel samples, the characteristics of the plasma were investigated by analyzing a spatially-resolved emission image of nitrogen excited species obtained with a two-dimensionally imaging spectrograph. Our previous study had reported on an excellent performance of the Okamoto-cavity microwave-induced plasma (MIP), enabling a nitrided layer having a several-micrometer-thickness to form on an iron substrate, even if the treatment is completed within 1 min, which is superior to a conventional plasma nitriding using low-pressure glow discharges requiring a prolonged treatment time. In this paper, the reason for this is discussed based on a spectrometric investigation. The emission images of band heads of nitrogen molecule and nitrogen molecule ion extended toward the axial/radial directions of the plasma at larger microwave powers supplied to the MIP, thus elevating the number density of the excited species of nitrogen, which would activate any chemical reaction on the iron substrate. However, a drastic increase in the growth rate of the nitrided layer when increasing the microwave power from 600 to 700 W, which had been observed in our previous study, could not be explained only from such a variation in the excited species of nitrogen. This result is probably because the growth process is dominantly controlled by thermal diffusion of nitrogen atom after it enters into the iron substrate, where the substrate temperature is the most important parameter concerning the mobility in the iron lattice. Therefore, the Okamoto-cavity MIP could contribute to a thermal source through radiative heating as well as a source of nitrogen excited species, especially in the growth process of the nitrided layer.

  10. Radio Frequency Plasma Synthesis of Boron Nitride Nanotubes (BNNTs) for Structural Applications: Part I

    NASA Technical Reports Server (NTRS)

    Hales, Stephen J.; Alexa, Joel A.; Jensen, Brian J.; Thomsen, Donald L.

    2016-01-01

    It is evident that nanotubes, such as carbon, boron nitride and even silicon, offer great potential for many aerospace applications. The opportunity exists to harness the extremely high strength and stiffness exhibited by high-purity, low-defect nanotubes in structural materials. Even though the technology associated with carbon nanotube (CNT) development is mature, the mechanical property benefits have yet to be fully realized. Boron nitride nanotubes (BNNTs) offer similar structural benefits, but exhibit superior chemical and thermal stability. A broader range of potential structural applications results, particularly as reinforcing agents for metal- and ceramic- based composites. However, synthesis of BNNTs is more challenging than CNTs mainly because of the higher processing temperatures required, and mass production techniques have yet to emerge. A promising technique is radio frequency plasma spray (RFPS), which is an inductively coupled, very high temperature process. The lack of electrodes and the self- contained, inert gas environment lend themselves to an ultraclean product. It is the aim of this White Paper to survey the state of the art with regard to nano-material production by analyzing the pros and cons of existing methods. The intention is to combine the best concepts and apply the NASA Langley Research Center (LaRC) RFPS facility to reliably synthesize large quantities of consistent, high-purity BNNTs.

  11. Previous heat treatment inducing different plasma nitriding behaviors in martensitic stainless steels

    SciTech Connect

    Figueroa, C. A.; Alvarez, F.; Mitchell, D. R. G.; Collins, G. A.; Short, K. T.

    2006-09-15

    In this work we report a study of the induced changes in structure and corrosion behavior of martensitic stainless steels nitrided by plasma immersion ion implantation (PI{sup 3}) at different previous heat treatments. The samples were characterized by x-ray diffraction and glancing angle x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy, and potentiodynamic measurements. Depending on the proportion of retained austenite in the unimplanted material, different phase transformations are obtained at lower and intermediate temperatures of nitrogen implantation. At higher temperatures, the great mobility of the chromium yields CrN segregations like spots in random distribution, and the {alpha}{sup '}-martensite is degraded to{alpha}-Fe (ferrite). The nitrided layer thickness follows a fairly linear relationship with the temperature and a parabolic law with the process time. The corrosion resistance depends strongly on chromium segregation from the martensitic matrix, as a result of the formation of CrN during the nitrogen implantation process and the formation of Cr{sub x}C during the heat treatment process. Briefly speaking, the best results are obtained using low tempering temperature and low implantation temperature (below 375 deg. ) due to the increment of the corrosion resistance and nitrogen dissolution in the structure with not too high diffusion depths (about 5-10 {mu}m)

  12. In vitro corrosion resistance of plasma source ion nitrided austenitic stainless steels.

    PubMed

    Le, M K; Zhu, X M

    2001-04-01

    Plasma source ion nitriding has emerged as a low-temperature, low-pressure nitriding approach for low-energy implanting nitrogen ions and then diffusing them into steel and alloy. In this work, a single high nitrogen face-centered-cubic (f.c.c.) phase (gammaN) formed on the 1Cr18Ni9Ti and AISI 316L austenitic stainless steels with a high nitrogen concentration of about 32 at % was characterized using Auger electron spectroscopy, electron probe microanalysis, glancing angle X-ray diffraction, and transmission electron microscopy. The corrosion resistance of the gammaN-phase layer was studied by the electrochemical cyclic polarization measurement in Ringer's solutions buffered to pH from 3.5 to 7.2 at a temperature of 37 degrees C. No pitting corrosion in the Ringer's solutions with pH = 7.2 and 5.5 was detected for the gammaN-phase layers on the two stainless steels. The high pitting potential for the gammaN-phase layers is higher, about 500 and 600 mV, above that of the two original stainless steels, respectively, in the Ringer's solution with pH = 3.5. The corroded surface morphologies of the gammaN-phase layers observed by scanning electron microscopy are consistent with the results of the electrochemical polarization measurement.

  13. Co-deposition of titanium and iron nitrides on SS-321 by using plasma focus

    NASA Astrophysics Data System (ADS)

    Ahmad, R.; Hassan, M.; Murtaza, G.; Akhter, J. I.; Qayyum, A.; Waheed, A.; Zakaullah, M.

    2006-02-01

    This article reports the co-deposition process of TiN0.9 and (Fe,Cr)(2)N compounds on SS-321 substrate using a 2.3 kJ dense plasma focus device operated with N-2 discharges. X-ray diffraction analysis is performed to investigate the ion-induced changes in the near surface structure of the SS-321. Scanning electron microscopy with the energy dispersive X-ray spectroscopy is carried out to analyse the surface morphology and the elemental composition of the nitrided samples. The results reveal that at the low fluence of ion bombardment, a non-stoichiometric tertiary phase (Fe,Cr)(x)N is developed, which transforms into a stable stoichiometric compound (Fe,Cr)(2)N by increasing the ion flux. Some CrN precipitates are also observed because of the thermal effect produced by the bombardment of energetic ion beam. Vickers micro-hardness values are increased more than twice for typical ion nitrided samples.

  14. Experimental and theoretical study on interaction between lanthanum and nitrogen during plasma rare earth nitriding

    NASA Astrophysics Data System (ADS)

    Zhang, C. S.; Yan, M. F.; Sun, Z.

    2013-12-01

    In present work, the interaction between lanthanum (La) and nitrogen (N) during plasma rare earth nitriding of M50NiL martensitic steel is analyzed. Phase compositions, elemental contents as well as microhardness profiles of surface layers are investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and microhardness tester to observe the changes of the N contents in treated layers. The results of microhardness, XRD and EDS indicate that the addition of pure La can speed up the denitriding rate compared with the case without La addition. The XPS results reveal that the presence of the Lasbnd O and Lasbnd N bond reduces the peak intensity of the Mesbnd N bond, which indicates that the addition of La element can reduce the N contents in nitrided layers through the surface oxidation and the attraction of La atoms. The theoretical thermodynamic calculations are employed to further clarify the denitriding function of the surface oxidation and the attraction between La and N atoms.

  15. Valence band offset and interface stoichiometry at epitaxial Si{sub 3}N{sub 4}/Si(111) heterojunctions formed by plasma nitridation

    SciTech Connect

    Lee, H.-M.; Kuo, C.-T.; Gwo Shangjr; Shiu, H.-W.; Chen, C.-H.

    2009-11-30

    Ultrathin {beta}-Si{sub 3}N{sub 4}(0001) epitaxial films formed by N{sub 2}-plasma nitridation of Si(111) substrates have been studied by photoelectron spectroscopy using synchrotron radiation. The valence band offset at the {beta}-Si{sub 3}N{sub 4}/Si interface was determined by valence-band photoelectron spectra to be 1.8 eV. Furthermore, the Si 2p core-level emissions were analyzed for nitride (Si{sup 4+}) and subnitride (Si{sup 3+} and Si{sup +}) components to characterize the interface stoichiometry. In contrast to the interfaces formed by ammonia thermal nitridation and N{sub 2}-plasma nitridation at room temperature, the interface formed by N{sub 2}-plasma nitridation at high substrate temperature is very close to subnitride free with an abrupt composition transition.

  16. Simulation studies on the evolution of gallium nitride on a liquid gallium surface under plasma bombardment.

    PubMed

    Vasquez, M R; Flauta, R E; Wada, M

    2008-02-01

    Monte Carlo simulations were conducted to study the formation of gallium-nitride (GaN) layer on liquid gallium (Ga) sputtering target immersed in nitrogen (N(2)) plasma. In the simulation model, N ions were assumed to possess energy equal to the bias voltage applied to the sputtering target with respect to the plasma. The results showed the surface morphology of GaN changed from a relatively smooth GaN on Ga surface at 50 eV N ion energy to a rough surface with GaN dendrites on liquid Ga at 500 eV ion energy. Further increase in N ion energy up to 1 keV resulted in smaller density of GaN dendrites on surface. Increasing surface coverage of Ga by GaN substantially reduced the sputtering yield of Ga from the target. These simulation results were correlated with previously reported experimental observations on liquid Ga surface immersed in the nitrogen plasma of a plasma-sputter-type ion source.

  17. Organometallic chemical vapor deposition of silicon nitride films enhanced by atomic nitrogen generated from surface-wave plasma

    SciTech Connect

    Okada, H.; Kato, M.; Ishimaru, T.; Sekiguchi, H.; Wakahara, A.; Furukawa, M.

    2014-02-20

    Organometallic chemical vapor deposition of silicon nitride films enhanced by atomic nitrogen generated from surface-wave plasma is investigated. Feasibility of precursors of triethylsilane (TES) and bis(dimethylamino)dimethylsilane (BDMADMS) is discussed based on a calculation of bond energies by computer simulation. Refractive indices of 1.81 and 1.71 are obtained for deposited films with TES and BDMADMS, respectively. X-ray photoelectron spectroscopy (XPS) analysis of the deposited film revealed that TES-based film coincides with the stoichiometric thermal silicon nitride.

  18. Thermal relaxation of a two dimensional plasma in a dc magnetic field. Part 2: Numerical simulation

    NASA Technical Reports Server (NTRS)

    Hsu, J. Y.; Joyce, G.; Montgomery, D.

    1974-01-01

    The thermal relaxation process for a spatially uniform two dimensional plasma in a uniform dc magnetic field is simulated numerically. Thermal relaxation times are defined in terms of the time necessary for the numerically computer Boltzman H-function to decrease through a given part of the distance to its minimum value. Dependence of relaxation time on two parameters is studied: number of particles per Debye square and ratio of gyrofrequency to plasma frequency.

  19. Thermal plasma treatment of stormwater sediments: comparison between DC non-transferred and partially transferred arc plasma.

    PubMed

    Li, O L; Guo, Y; Chang, J S; Saito, N

    2015-01-01

    The disposal of enormous amount of stormwater sediments becomes an emerging worldwide problem. Stormwater sediments are contaminated by heavy metals, phosphorus, trace organic and hydrocarbons, and cannot be disposed without treatment. Thermal plasma decontamination technology offers a high decomposition rate in a wide range of toxic organic compound and immobilization of heavy metal. In this study, we compared the treatment results between two different modes of thermal plasma: (1) a non-transferred direct current (DC) mode and (2) a partial DC-transferred mode. The reductions of total organic carbon (TOC) were, respectively, 25% and 80% for non-transferred and partially transferred plasma, respectively. Most of the toxic organic compounds were converted majorly to CxHy. In the gaseous emission, the accumulated CxHy, CO, NO and H2S were significantly higher in partially transferred mode than in non-transferred mode. The solid analysis demonstrated that the concentrations of Ca and Fe were enriched by 500% and 40%, respectively. New chemical compositions such as KAlSi3O8, Fe3O4, NaCl and CaSO4 were formed after treatment in partially DC-transferred mode. The power inputs were 1 and 10 kW, respectively, for non-transferred DC mode and a partially DC-transferred mode. With a lower energy input, non-transferred plasma treatment can be used for decontamination of sediments with low TOC and metal concentration. Meanwhile, partially transferred thermal plasma with higher energy input is suitable for treating sediments with high TOC percentage and volatile metal concentration. The organic compounds are converted into valuable gaseous products which can be recycled as an energy source.

  20. Experimental tests for carbon nanomaterial synthesis using DC plasma jet

    NASA Astrophysics Data System (ADS)

    Lange, H.; Łabȩdź, O.; Tylska, I.; Huczko, A.; Bystrzejewski, M.

    2014-11-01

    In the frame of this work some experimental tests were performed in the plasma jet. Pure ethanol vapour alone or with the addition of fine iron powder were used to synthesize few-layer graphene or carbon-encapsulated iron nanoparticles, respectively.

  1. Effects of the Process Parameters on the Microstructure and Properties of Nitrided 17-4PH Stainless Steel

    NASA Astrophysics Data System (ADS)

    Wang, Jun; Lin, Yuanhua; Zeng, Dezhi; Yan, Jing; Fan, Hongyuan

    2013-04-01

    The effects of process parameters on the microstructure, microhardness, and dry-sliding wear behavior of plasma nitrided 17-4PH stainless steel were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and wear testing. The results show that a wear-resistant nitrided layer was formed on the surface of direct current plasma nitrided 17-4PH martensitic stainless steel. The microstructure and thickness of the nitrided layer is dependent on the treatment temperature rather than process pressure. XRD indicated that a single α N phase was formed during nitriding at 623 K (350 °C). When the temperature increased, the α N phase disappeared and CrN transformed in the nitrided layer. The hardness measurement demonstrated that the hardness of the stainless substrate steel increased from 320 HV0.1 in the untreated condition increasing to about 1275HV0.1 after nitriding 623 K (350 °C)/600 pa/4 hours. The extremely high values of the microhardness achieved by the great misfit-induced stress fields associated with the plenty of dislocation group and stacking fault. Dry-sliding wear resistance was improved by DC plasma nitriding. The best wear-resistance performance of a nitrided sample was obtained after nitriding at 673 K (350 °C), when the single α N-phase was produced and there were no CrN precipitates in the nitrided layer.

  2. Experimental and modelling study of the plasma vapour-phase synthesis of ultrafine aluminum nitride powders

    NASA Astrophysics Data System (ADS)

    da Cruz, Antonio-Carlos

    An experimental and theoretical study of the fundamentals of the vapour phase synthesis of ultrafine aluminum nitride (AIN) particles using thermal plasma was carried out. The study used the concept of a transferred-arc reactor which produces AlN ultrafine powders in two stages: evaporation of aluminum (Al) metal by the transferred-arc in non nitriding conditions; and the reaction between Al vapour and ammonia (NH3) in a separate tubular reactor. A new version of this reactor concept was built in which the transferred-arc chamber and tubular reactor were vertically aligned. This reactor design allowed the study of both radial and axial mixing of ammonia with the plasma chamber off-gas. Ultrafine powders with a specific surface area (SSA) in the range of 38--270 m2/g were produced in two plasma chamber off-gas temperature levels (1800 and 2000 K), with different quenching intensities, and two different plasma gas compositions (pure Ar and Ar/H2 mixture). The dependence of the particle size and composition on the reactor operating conditions was investigated. Depending on the plasma gas composition, two different trends were observed for the SSA as a function of quenching intensity, with the radial injection of NH3. A two-dimensional numerical model was developed for the nucleation and growth of ultrafine particles in this system, using the method of moments. A new equation for the nucleation rate for the AlN system was developed. This equation considers the effect of reaction on the surface of clusters of the new phase. This new modelling approach could explain the trends observed experimentally. The importance of the mechanisms for the gas-to-condensed phase transition in the AlN system were examined. The sinterability of the powder produced was examined. Sintering to full density was achieved at 1550°C. Because of the high oxygen content of the powder, a second phase identified as aluminum oxynitride (ALON) was observed to form.

  3. Ion-plasma nitriding of austenitic steel in a low-pressure low-frequency inductive discharge with ferrite core

    NASA Astrophysics Data System (ADS)

    Isupov, M. V.; Pinaev, V. A.; Mul, D. O.; Belousova, N. S.

    2017-05-01

    An experimental investigation of ion-plasma nitriding of austenitic stainless steel AISI 321 in a low-frequency (100 kHz) nitrogen inductive discharge has been performed for the nitrogen pressure of 7 Pa, nitrogen ion densities of 1010-1011 cm-3, sample temperatures of 440-590 °C, the densities of current on the sample surface of 1.2-3.3 mA/cm2, sample biases of -500 and -750 V. The time of ion-plasma treatment was 20 and 60 min. It is shown that even for the short (20 min.) ion-plasma treatment in the low-frequency inductive discharge, formation of nitrided layers with the thickness of up to 40 μm and microhardness of up to 9 GPa is observed.

  4. Controlled oxidation, biofunctionalization, and patterning of alkyl monolayers on silicon and silicon nitride surfaces using plasma treatment.

    PubMed

    Rosso, Michel; Giesbers, Marcel; Schroën, Karin; Zuilhof, Han

    2010-01-19

    A new method is presented for the fast and reproducible functionalization of silicon and silicon nitride surfaces coated with covalently attached alkyl monolayers. After formation of a methyl-terminated 1-hexadecyl monolayer on H-terminated Si(100) and Si(111) surfaces, short plasma treatments (1-3 s) are sufficient to create oxidized functionalities without damaging the underlying oxide-free silicon. The new functional groups can, e.g., be derivatized using the reaction of surface aldehyde groups with primary amines to form imine bonds. In this way, plasma-treated monolayers on silicon or silicon nitride surfaces were successfully coated with nanoparticles, or proteins such as avidin. In addition, we demonstrate the possibility of micropatterning, using a soft contact mask during the plasma treatment. Using water contact angle measurements, ellipsometry, XPS, IRRAS, AFM, and reflectometry, proof of principle is demonstrated of a yet unexplored way to form patterned alkyl monolayers on oxide-free silicon surfaces.

  5. Hot Plasma from Solar Active Region Cores: a Test of AC and DC Coronal Heating Models?

    NASA Astrophysics Data System (ADS)

    Schmelz, J. T.; Asgari-Targhi, M.; Christian, G. M.; Dhaliwal, R. S.; Pathak, S.

    2015-06-01

    Direct current (DC) models of solar coronal heating invoke magnetic reconnection to convert magnetic free energy into heat, whereas alternating current (AC) models invoke wave dissipation. In both cases the energy is supplied by photospheric footpoint motions. For a given footpoint velocity amplitude, DC models predict lower average heating rates but greater temperature variability when compared to AC models. Therefore, evidence of hot plasma (T > 5 MK) in the cores of active regions could be one of the ways for current observations to distinguish between AC and DC models. We have analyzed data from the X-Ray Telescope (XRT) and the Atmospheric Imaging Assembly for 12 quiescent active region cores, all of which were observed in the XRT Be_thick channel. We did Differential Emission Measure (DEM) analysis and achieved good fits for each data set. We then artificially truncated the hot plasma of the DEM model at 5 MK and examined the resulting fits to the data. For some regions in our sample, the XRT intensities continued to be well-matched by the DEM predictions, even without the hot plasma. This truncation, however, resulted in unacceptable fits for the other regions. This result indicates that the hot plasma is present in these regions, even if the precise DEM distribution cannot be determined with the data available. We conclude that reconnection may be heating the hot plasma component of these active regions.

  6. HOT PLASMA FROM SOLAR ACTIVE REGION CORES: A TEST OF AC AND DC CORONAL HEATING MODELS?

    SciTech Connect

    Schmelz, J. T.; Christian, G. M.; Dhaliwal, R. S.; Pathak, S.; Asgari-Targhi, M.

    2015-06-20

    Direct current (DC) models of solar coronal heating invoke magnetic reconnection to convert magnetic free energy into heat, whereas alternating current (AC) models invoke wave dissipation. In both cases the energy is supplied by photospheric footpoint motions. For a given footpoint velocity amplitude, DC models predict lower average heating rates but greater temperature variability when compared to AC models. Therefore, evidence of hot plasma (T > 5 MK) in the cores of active regions could be one of the ways for current observations to distinguish between AC and DC models. We have analyzed data from the X-Ray Telescope (XRT) and the Atmospheric Imaging Assembly for 12 quiescent active region cores, all of which were observed in the XRT Be-thick channel. We did Differential Emission Measure (DEM) analysis and achieved good fits for each data set. We then artificially truncated the hot plasma of the DEM model at 5 MK and examined the resulting fits to the data. For some regions in our sample, the XRT intensities continued to be well-matched by the DEM predictions, even without the hot plasma. This truncation, however, resulted in unacceptable fits for the other regions. This result indicates that the hot plasma is present in these regions, even if the precise DEM distribution cannot be determined with the data available. We conclude that reconnection may be heating the hot plasma component of these active regions.

  7. Modeling a short cold cathode DC discharge device with controllable plasma parameters

    NASA Astrophysics Data System (ADS)

    Kudryavtsev, Anatoly; Adams, Steven; Demidov, Vladimir; Bogdanov, Yevgeny

    2009-11-01

    A short (without positive column) DC gas-discharge device with a cold cathode has been modeled. The device consists of the plane disk-shaped cathode and anode while the inter-electrode gap is bounded by a cylindrical wall. The cathode and anode are each 2.5 cm in diameter, and the inter-electrode gap is 12 mm. The wall is made of conducting parts divided by an insulator. The modeling has been performed for argon plasma at 1 Torr pressure. It is demonstrated in the model that spatial distributions of electron density and temperature and argon metastable atom density depend on the DC voltage applied to different conducting parts of the wall. Applied voltage can trap within the device volume energetic electrons arising from atomic and molecular processes in the plasma. This leads to a modification in the heating of slow electrons by energetic electrons and as a result modifies the controlling plasma parameters.

  8. An evidence of period doubling bifurcation in a dc driven semiconductor-gas discharge plasma

    NASA Astrophysics Data System (ADS)

    Mansuroglu, D.; Uzun-Kaymak, I. U.; Rafatov, I.

    2017-05-01

    We present an experimental study of nonlinearity observed in a dc driven semiconductor-gas discharge system. The plasma glow is generated using planar electrodes in a vacuum chamber filled with nitrogen gas at partial atmospheric pressure. The discharge behaves oscillatory in time, showing single and sometimes multiple periodicities in plasma current and voltage measurements. Harmonic frequency generations and period doubling cascade are investigated experimentally by varying the applied voltage. To identify the stability condition, numerical simulations are conducted using COMSOL® Multiphysics software. The discharge is modeled as a one dimensional plasma slab. Numerical results are in good agreement with the experimental measurements.

  9. Superconducting structure with layers of niobium nitride and aluminum nitride

    DOEpatents

    Murduck, J.M.; Lepetre, Y.J.; Schuller, I.K.; Ketterson, J.B.

    1989-07-04

    A superconducting structure is formed by depositing alternate layers of aluminum nitride and niobium nitride on a substrate. Deposition methods include dc magnetron reactive sputtering, rf magnetron reactive sputtering, thin-film diffusion, chemical vapor deposition, and ion-beam deposition. Structures have been built with layers of niobium nitride and aluminum nitride having thicknesses in a range of 20 to 350 Angstroms. Best results have been achieved with films of niobium nitride deposited to a thickness of approximately 70 Angstroms and aluminum nitride deposited to a thickness of approximately 20 Angstroms. Such films of niobium nitride separated by a single layer of aluminum nitride are useful in forming Josephson junctions. Structures of 30 or more alternating layers of niobium nitride and aluminum nitride are useful when deposited on fixed substrates or flexible strips to form bulk superconductors for carrying electric current. They are also adaptable as voltage-controlled microwave energy sources. 8 figs.

  10. Superconducting structure with layers of niobium nitride and aluminum nitride

    DOEpatents

    Murduck, James M.; Lepetre, Yves J.; Schuller, Ivan K.; Ketterson, John B.

    1989-01-01

    A superconducting structure is formed by depositing alternate layers of aluminum nitride and niobium nitride on a substrate. Deposition methods include dc magnetron reactive sputtering, rf magnetron reactive sputtering, thin-film diffusion, chemical vapor deposition, and ion-beam deposition. Structures have been built with layers of niobium nitride and aluminum nitride having thicknesses in a range of 20 to 350 Angstroms. Best results have been achieved with films of niobium nitride deposited to a thickness of approximately 70 Angstroms and aluminum nitride deposited to a thickness of approximately 20 Angstroms. Such films of niobium nitride separated by a single layer of aluminum nitride are useful in forming Josephson junctions. Structures of 30 or more alternating layers of niobium nitride and aluminum nitride are useful when deposited on fixed substrates or flexible strips to form bulk superconductors for carrying electric current. They are also adaptable as voltage-controlled microwave energy sources.

  11. Control of plasma-liquid interaction of atmospheric DC glow discharge using liquid electrode

    NASA Astrophysics Data System (ADS)

    Shirai, Naoki; Aoki, Ryuta; Nito, Aihito; Aoki, Takuya; Uchida, Satoshi; Tochikubo, Fumiyoshi

    2014-10-01

    Atmospheric plasma in contact with liquid have a variety of interesting phenomena and applications. Previously, we investigated the fundamental characteristics of an atmospheric dc glow discharge using a liquid electrode with a miniature helium flow. We tried to control the plasma-liquid interaction by changing the plasma parameter such as gas species, liquid, and applied voltage. Sheath flow system enables another gas (N2, O2, Ar) flow to around the helium core flow. It can control the gas species around the discharge. When liquid (NaCl aq.) cathode DC discharge is generated, Na emission (588 nm) can be observed from liquid surface with increasing discharge current. Na emission strongly depends on the discharge current and liquid temperature. However, when Ar sheath flow is used, the intensity of Na becomes weak. When liquid anode DC discharge is generated, self-organized luminous pattern formation can be observed at the liquid surface. The pattern depends on existence of oxygen gas in gap. By changing the oxygen gas ratio in the gap, variety of pattern formation can be observed. The discharge in contact with liquid also can be used for synthesis of metal nanoparticles at plasma-liquid interface. Size and shape of nanoparticles depend on discharge gases. This work was supported financially in part by a Grant-in-Aid for Scientific Research on Innovative Areas (No 21110007) from MEXT, Japan.

  12. Synthesis of Nanosized Titanium Oxide and Nitride Through Vacuum Arc Plasma Expansion Technique

    NASA Astrophysics Data System (ADS)

    Lepeshev, A. A.; Karpov, I. V.; Ushakov, A. V.; Fedorov, L. Yu.; Shaihadinov, A. A.

    2016-12-01

    Physical vapor deposition techniques such vacuum arc plasma deposition — which are very commonly used in thin film technology — appear to hold much promise for the synthesis of nanocrystalline thin films as well as nanoparticles. Monodisperse and spherical titanium oxide (TiO2) and nitride nanoparticles were produced at room temperature as a cluster beam in the gas phase using a cluster-deposition source. Using the basic principles of the gas condensation method, this study has developed vacuum arc nanoparticle synthesis system. We demonstrate that major process deposition parameter is the pressure in the plasma chamber. This is the major advantage of these techniques over thermal evaporation. Our method affords TiN powders with high specific surface areas exceeding 200m2g-1. TEM micrograph of TiO2 nanoparticles prepared at an oxygen pressure of 60Pa show an average particle size of 6nm. TiO2 nanoparticles prepared at an oxygen pressure of 70Pa were observed to not have a reduced average particle size.

  13. Structural and chemical analysis of annealed plasma-enhanced atomic layer deposition aluminum nitride films

    SciTech Connect

    Broas, Mikael Vuorinen, Vesa; Sippola, Perttu; Pyymaki Perros, Alexander; Lipsanen, Harri; Sajavaara, Timo; Paulasto-Kröckel, Mervi

    2016-07-15

    Plasma-enhanced atomic layer deposition was utilized to grow aluminum nitride (AlN) films on Si from trimethylaluminum and N{sub 2}:H{sub 2} plasma at 200 °C. Thermal treatments were then applied on the films which caused changes in their chemical composition and nanostructure. These changes were observed to manifest in the refractive indices and densities of the films. The AlN films were identified to contain light element impurities, namely, H, C, and excess N due to nonideal precursor reactions. Oxygen contamination was also identified in the films. Many of the embedded impurities became volatile in the elevated annealing temperatures. Most notably, high amounts of H were observed to desorb from the AlN films. Furthermore, dinitrogen triple bonds were identified with infrared spectroscopy in the films. The triple bonds broke after annealing at 1000 °C for 1 h which likely caused enhanced hydrolysis of the films. The nanostructure of the films was identified to be amorphous in the as-deposited state and to become nanocrystalline after 1 h of annealing at 1000 °C.

  14. Simulation Study of an Extended Density DC Glow Toroidal Plasma Source

    SciTech Connect

    Granda-Gutierrez, E. E.; Piedad-Beneitez, A. de la; Lopez-Callejas, R.; Godoy-Cabrera, O. G.; Benitez-Read, J. S.; Pacheco-Sotelo, J. O.; Pena-Eguiluz, R.; Mercado-Cabrera, A.; Valencia A, R.; Barocio, S. R.

    2006-12-04

    Conventional wisdom assigns the DC glow discharge regime to plasma currents below {approx}500 mA values, beyond which the discharge falls into the anomalous glow and the turbulent arc regimes. However, we have found evidence that, during toroidal discharges, this barrier can be ostensibly extended up to 800 mA. Thus, a computer simulation has been applied to the evolution of the main electrical characteristics of such a glow discharge plasma in a toroidal vessel in order to design and construct a respective voltage/current controlled source. This should be able to generate a DC plasma in the glow regime with which currents in the range 10-3-100 A can be experimented and 109-1010 cm-3 plasma densities can be achieved to PIII optimization purposes. The plasma is modelled as a voltage-controlled current source able to be turned on whenever the breakdown voltage is reached across the gap between the anode and the vessel wall. The simulation outcome fits well our experimental measurements showing that the plasma current obeys power laws that are dependent on the power current and other control variables such as the gas pressure.

  15. Influence of surface nano/ultrafine structure formed via pre-deep rolling process on the plasma nitriding characteristics of the AISI 316L stainless steel

    NASA Astrophysics Data System (ADS)

    Tadi, A. Jafari; Hosseini, S. R.; Semiromi, M. Naderi

    2017-08-01

    Influence of deep rolling prior to plasma nitriding on microstructure and hardness of the AISI 316L stainless steel was investigated in this paper. Deep rolling using `ball-point' tool was conducted on the 316L stainless steel bar at multiple passes. Then, plasma nitriding was performed on the as-received and deep-rolled kinds at 450 °C temperature for 5 h. Structural characterisation was done using optical microscope, field emission scanning electron microscope, feritscope, X-ray diffractometer, and glow discharge optical emission spectroscope as well as hardness measurement by a Vickers micro-hardness tester at 0.1 kgf. An ultrafine structure and a nitrogen-rich layer were, respectively, formed on the rolled and nitrided surfaces. Surface hardness was increased from 210 up to 450, 670 and 1050 HV0.1 after the rolling, nitriding, and rolling-nitriding processes, respectively. Thickness of the nitrided layer was increased from 12 to 20 µm and diffusion depth of nitrogen from 12 to 25 µm via conducting the deep rolling before the nitriding process. The rolling-nitriding process was resulted in rising of nitrogen concentration by a factor of about 3 at near-surface regions.

  16. Numerical characterization of magnetized capacitively coupled argon plasmas driven by combined dc/rf sources

    NASA Astrophysics Data System (ADS)

    Yang, Shali; Zhang, Ya; Wang, Hong-Yu; Wang, Shuai; Jiang, Wei

    2017-03-01

    The characteristics of magnetized capacitively coupled plasmas (CCPs) driven by combined dc/rf sources in argon have been investigated by a one-dimensional implicit Particle-in-cell/Monte Carlo collision model. Discharges operating at 13.56 MHz with a fixed rf voltage of 300 V are simulated at the pressure of 50 mTorr in argon. Four cases, i.e., CCP driven by rf source, rf + dc sources, rf source with magnetic field, and rf + dc sources with magnetic field, are presented and compared at the Vdc = -100 V, B = 50 Gs, and γi = 0.2. It is found that, with the influence of dc voltage and magnetic field, the plasma density has been greatly enhanced by over one order of magnitude over the rf-only case. This is due to the fact that the mean free path of electrons decreases by the cyclotron motion and the energetic secondary electrons are trapped by the magnetic field, leading to a significant increase in heating and ionization rates. Moreover, transition of the stochastic to Ohmic electron heating mechanism takes place as the magnetic field increases because electron kinetics can be strongly affected by the magnetic field. In general, we have demonstrated that such a configuration will enhance the discharge and thus enable CCPs work under extremely high energy density stably that can never be operated by any other configurations. We expect that such a configuration can promote many related applications, like etching, sputtering, and deposition.

  17. Experiment planning, mathematical modelling, and nonlinear optimization of the ion-nitriding process in a glow-discharge plasma

    SciTech Connect

    Petros, O.; Kuhn, S.; Popa, G.

    1982-06-01

    A new, efficient method for investigating and optimizing the ion-nitriding process in a glow-discharge plasma is proposed and worked out in detail for the mass kinetics of Rp-3 steel. This method, which is based on the concepts of experiment planning, mathematical modelling, and nonlinear optimization, is quite general and potentially applicable to a wide class of technological and other processes depending on several parameters.

  18. Pulsed DC discharge for synthesis of conjugated plasma polymerized aniline thin film

    NASA Astrophysics Data System (ADS)

    Barman, Tapan; Pal, Arup R.

    2012-10-01

    The polymerization of aniline in pulsed dc plasma is studied and the effects of variation of pressure, power, frequency and duty cycle on the chemical structure of the obtained film are examined. During the film deposition optical emission spectroscopy is used to investigate the molecular dissociation of aniline. The chemical structure of the films is characterized using Fourier transform infra-red spectroscopy. The surface morphology is studied using atomic force microscopy. Results show the retention of polyaniline like structure having conjugated nature at some particular discharge conditions. Moreover, it is observed that a strong dependence of film chemistry is obvious on the discharge power, reactor pressure, pulse repetition frequency and duty cycle. The advantages of the pulsed dc for deposition of conjugated plasma polymerizes thin film have been highlighted.

  19. One-dimensional hybrid simulation of the dc/RF combined driven capacitively coupled CF{sub 4} plasmas

    SciTech Connect

    Wang Shuai; Xu Xiang; Wang Younian

    2012-11-15

    We developed a one-dimensional hybrid model to simulate the dc/RF combined driven capacitively coupled plasma for CF{sub 4} discharges. The numerical results show the influence of the dc source on the plasma density distribution, ion energy distributions (IEDs), and ion angle distributions (IADs) on both RF and dc electrodes. The increase of dc voltage impels more ions with high energy to the electrode applied to the dc source, which makes the IEDs at the dc electrode shift toward higher energy and the peaks in IADs shift toward the small angle region. At the same time, it also decreases ion-energy at the RF electrode and enlarges the ion-angles which strike the RF electrode.

  20. Reactive Plasma-Sprayed Aluminum Nitride-Based Coating Thermal Conductivity

    NASA Astrophysics Data System (ADS)

    Shahien, Mohammed; Yamada, Motohiro; Fukumoto, Masahiro; Egota, Kazumi; Okamoto, Kenji

    2015-12-01

    Recently, thick aluminum nitride/alumina (AlN/Al2O3) composite coatings were successfully fabricated through the reactive plasma spraying of fine Al2O3/AlN mixture in the N2/H2 atmospheric plasma. The coatings consist of AlN, Al5O6N, γ-Al2O3, and α-Al2O3 phases. This study will evaluate the thermal conductivity of these complicated plasma-sprayed coatings and optimize the controlling aspects. Furthermore, the influence of the process parameters on the coatings thermal conductivity will be investigated. The fabricated coatings showed very low thermal conductivity (2.43 W/m K) compared to the AlN sintered compacts. It is attributed to the phase composition of the fabricated coatings, oxide content, and porosity. The presence of Al2O3, Al5O6N and the high coating porosity decreased its thermal conductivity. The presence of oxygen in the AlN lattice creates Al vacancies which lead to phonon scattering and therefore suppressed the thermal conductivity. The formation of γ-Al2O3 phase in the coating leads to further decrease in its conductivity, due to its lower density compared to the α-phase. Moreover, the high porosity of the coating strongly suppressed the conductivity. This is due to the complicated microstructure of plasma spray coatings (splats, porosity, and interfaces, particularly in case of reactive spray process), which obviously lowered the conductivity. Furthermore, the measured coating density was lower than the AlN value and suppressed the coating conductivity. In addition, the spraying parameter showed a varied effect on the coating phase composition, porosity, density, and therefore on its conductivity. Although the N2 gas flow improved the nitride content, it suppressed the thermal conductivity gradually. It is attributed to the further increase in the porosity and further decrease in the density of the coatings with the N2 gas. Furthermore, increasing the arc did not show a significant change on the coating thermal conductivity. On the other hand

  1. DC Electric Fields and Associated Plasma Drifts Observed with the C/NOFS Satellite

    NASA Technical Reports Server (NTRS)

    Pfaff, R.; Freudenreich, H.; Bromund, K.; Rowland, D.

    2009-01-01

    Initial DC electric field observations and associated plasma drifts are presented from the Vector Electric Field Investigation (VEFI) on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite. We present statistical averages of the vector fields for the first year of operations that include both the zonal and radial components of the resulting E x B plasma flows at low latitudes. Magnetic field data from the VEFI science magnetometer are used to compute the plasma flows. The DC electric field detector reveals zonal and radial electric fields that undergo strong diurnal variations, typically displaying eastward and outward-directed fields during the day and westward and downward-directed fields at night. There is considerable variation in the large scale DC electric field data, in both the daytime and nighttime cases, with enhanced structures typically observed at night. In general, the measured zonal DC electric field amplitudes include excursions that extend within the 0.4 - 2 m V/m range, corresponding to E x B drifts of the order of 30-150 m/s. The average vertical or radial electric fields may exceed the zonal fields in amplitude by a factor of 1.5 to 2. Although the data compare well, in a general sense, with previous satellite observations and statistical patterns of vertical ion drifts, the E x B drifts we report from C/NOFS rarely show a pronounced pre-reversal enhancement after sunset. We attribute this to a combination of extreme solar minimum conditions and the fact that the C/NOFS orbit of 401 by 867 km carries the probes essentially above the lower altitude regions where the wind-driven dynamo might be expected to create enhanced upwards drifts in the early evening. Evidence for wavenumber 4 tidal effects and other longitudinal signatures have been detected and will be presented. We also discuss off-equatorial electric fields and their relation to the ambient plasma density.

  2. In-Vitro Biocompatibility Studies of Plasma-Nitrided Titanium Alloy β-21S Using Fibroblast Cells

    NASA Astrophysics Data System (ADS)

    Mohan, L.; Raja, M. D.; Uma, T. S.; Rajendran, N.; Anandan, C.

    2016-04-01

    In the present work, titanium alloy β-21S was nitrided in a low-pressure RF plasma with 100% nitrogen and 20% hydrogen-diluted nitrogen at 800 °C for 4 h and the samples were evaluated for in-vitro biocompatibility by using NIH 3T3 fibroblast cell line. Cellular behavior was evaluated in terms of cell morphology and its viability. FESEM was exploited to observe the morphology of the cells fixed over the surface of the implant. Fibroblasts were seemed to be well distributed over the surface with its characteristic spindle-like shape. Over all, the results indicate that nitriding provided a compatible surface for cell attachment and cell growth. Cell viability and proliferation was assessed by using standard MTT assay. Compared with substrate, the nitrided samples exhibited high-percentage cell viability demonstrating their increased biocompatibility. In addition, the nitrided samples facilitate bone-like apatite formation and exhibited a gradual increase of apatite formation after immersion in Hanks' solution.

  3. FAST TRACK COMMUNICATION: Plasma agents in bio-decontamination by dc discharges in atmospheric air

    NASA Astrophysics Data System (ADS)

    Machala, Zdenko; Chládeková, Lenka; Pelach, Michal

    2010-06-01

    Bio-decontamination of water and surfaces contaminated by bacteria (Salmonella typhimurium) was investigated in two types of positive dc discharges in atmospheric pressure air, in needle-to-plane geometry: the streamer corona and its transition to a novel regime called transient spark with short high current pulses of limited energy. Both generate a cold non-equilibrium plasma. Electro-spraying of treated water through a needle electrode was applied for the first time and resulted in fast bio-decontamination. Experiments providing separation of various biocidal plasma agents, along with the emission spectra and coupled with oxidation stress measurements in the cell membranes helped to better understand the mechanisms of microbial inactivation. The indirect exposure of contaminated surfaces to neutral active species was almost as efficient as the direct exposure to the plasma, whereas applying only UV radiation from the plasma had no biocidal effects. Radicals and reactive oxygen species were identified as dominant biocidal agents.

  4. Volt-ampere characteristics of a nitrogen DC plasma arc with anode melting

    NASA Astrophysics Data System (ADS)

    Zhao, Peng; Ni, Guo-Hua; Meng, Yue-Dong; Nagatsu, Masaaki

    2013-06-01

    The characteristics of a nitrogen arc using a graphite cathode and a melting anode in a pilot-scale plasma furnace are investigated. The voltage is examined as a function of current and apparent plasma length. The voltage increases non-linearly with the increase of apparent plasma length, with the current fixed. The experimental data so obtained are compared with the predictions of the Bowman model for the electric arc, and with numerical simulations as well. The level of agreement between the experimental data at the melting anode and the numerical predictions confirms the suitability of the proposed the Bowman model. These characteristics are relevant to the engineering design and evaluation of a DC plasma furnace and reactor for the treatment of hazardous fly ash waste.

  5. Morphological and Electrochemical Study of Sulfide/Nitride Nanostructure Deposited Through Pulsed Plasma Electrolysis

    NASA Astrophysics Data System (ADS)

    Tavakoli, H.; Sobhani, M.

    2017-04-01

    This study investigated the feasibility of coating a steel St12 substrate with a sulfide/nitride layer. The coating process was conducted through a plasma electrolysis technique with a pulsed regime applied at frequencies of 100, 500, and 1000 Hz. It was found that the use of higher frequencies in the mentioned process provides better control over workpiece surface temperature and leads to reduced extent of voltage variations required to achieve a fixed temperature. The coating deposited at the frequency of 1000 Hz and voltage of about 235 V exhibited a nanostructure composed of 50 nm particles. The deposited coating consisted of an outer porous layer and an inner relatively dense layer. The x-ray studies identified the phases of the coating as γ'-Fe4N, Fe2-3N and FeS. The presence of FeS phase reduces the friction coefficient of the surface to about half the value obtainable in its absence. Studying the electrochemical impedance of the layer revealed that using a higher frequency in the deposition process increases the stability of resulting layer against seven days of immersion in the corrosive solution.

  6. Morphological and Electrochemical Study of Sulfide/Nitride Nanostructure Deposited Through Pulsed Plasma Electrolysis

    NASA Astrophysics Data System (ADS)

    Tavakoli, H.; Sobhani, M.

    2017-03-01

    This study investigated the feasibility of coating a steel St12 substrate with a sulfide/nitride layer. The coating process was conducted through a plasma electrolysis technique with a pulsed regime applied at frequencies of 100, 500, and 1000 Hz. It was found that the use of higher frequencies in the mentioned process provides better control over workpiece surface temperature and leads to reduced extent of voltage variations required to achieve a fixed temperature. The coating deposited at the frequency of 1000 Hz and voltage of about 235 V exhibited a nanostructure composed of 50 nm particles. The deposited coating consisted of an outer porous layer and an inner relatively dense layer. The x-ray studies identified the phases of the coating as γ'-Fe4N, Fe2-3N and FeS. The presence of FeS phase reduces the friction coefficient of the surface to about half the value obtainable in its absence. Studying the electrochemical impedance of the layer revealed that using a higher frequency in the deposition process increases the stability of resulting layer against seven days of immersion in the corrosive solution.

  7. Boron nitride nanowalls: low-temperature plasma-enhanced chemical vapor deposition synthesis and optical properties.

    PubMed

    Merenkov, Ivan S; Kosinova, Marina L; Maximovskii, Eugene A

    2017-05-05

    Hexagonal boron nitride (h-BN) nanowalls (BNNWs) were synthesized by plasma-enhanced chemical vapor deposition (PECVD) from a borazine (B3N3H6) and ammonia (NH3) gas mixture at a low temperature range of 400 °C-600 °C on GaAs(100) substrates. The effect of the synthesis temperature on the structure and surface morphology of h-BN films was investigated. The length and thickness of the h-BN nanowalls were in the ranges of 50-200 nm and 15-30 nm, respectively. Transmission electron microscope images showed the obtained BNNWs were composed of layered non-equiaxed h-BN nanocrystallites 5-10 nm in size. The parallel-aligned h-BN layers as an interfacial layer were observed between the film and GaAs(100) substrate. BNNWs demonstrate strong blue light emission, high transparency (>90%) both in visible and infrared spectral regions and are promising for optical applications. The present results enable a convenient growth of BNNWs at low temperatures.

  8. Boron nitride nanowalls: low-temperature plasma-enhanced chemical vapor deposition synthesis and optical properties

    NASA Astrophysics Data System (ADS)

    Merenkov, Ivan S.; Kosinova, Marina L.; Maximovskii, Eugene A.

    2017-05-01

    Hexagonal boron nitride (h-BN) nanowalls (BNNWs) were synthesized by plasma-enhanced chemical vapor deposition (PECVD) from a borazine (B3N3H6) and ammonia (NH3) gas mixture at a low temperature range of 400 °C-600 °C on GaAs(100) substrates. The effect of the synthesis temperature on the structure and surface morphology of h-BN films was investigated. The length and thickness of the h-BN nanowalls were in the ranges of 50-200 nm and 15-30 nm, respectively. Transmission electron microscope images showed the obtained BNNWs were composed of layered non-equiaxed h-BN nanocrystallites 5-10 nm in size. The parallel-aligned h-BN layers as an interfacial layer were observed between the film and GaAs(100) substrate. BNNWs demonstrate strong blue light emission, high transparency (>90%) both in visible and infrared spectral regions and are promising for optical applications. The present results enable a convenient growth of BNNWs at low temperatures.

  9. Growth and characterization of silicon-nitride films by plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Han, I. K.; Lee, Y. J.; Jo, J. W.; Lee, J. I.; Kang, K. N.

    1991-06-01

    Thin films of silicon nitride were deposited on Si wafers by plasma-enhanced chemical vapor deposition (PECVD). For deposition we designed and made hot wall capacitively coupled PECVD equipment which has a radial flow reactor. Using an RF generator of frequency 13.56 MHz and SiH 4 (5% SiH 4 in N 2) + NH 3 and N 2 as reactive gases and the carrier gas, respectively, we systematically varied the substrate temperature (240-360°C), the partial pressure of reactive gases (0.35

  10. Wetting behaviour of carbon nitride nanostructures grown by plasma enhanced chemical vapour deposition technique

    NASA Astrophysics Data System (ADS)

    Ahmad Kamal, Shafarina Azlinda; Ritikos, Richard; Abdul Rahman, Saadah

    2015-02-01

    Tuning the wettability of various coating materials by simply controlling the deposition parameters is essential for various specific applications. In this work, carbon nitride (CNx) films were deposited on silicon (1 1 1) substrates using radio-frequency plasma enhanced chemical vapour deposition employing parallel plate electrode configuration. Effects of varying the electrode distance (DE) on the films' structure and bonding properties were investigated using Field emission scanning electron microscopy, Atomic force microscopy, Fourier transform infrared and X-ray photoemission spectroscopy. The wettability of the films was analyzed using water contact angle measurements. At high DE, the CNx films' surface was smooth and uniform. This changed into fibrous nanostructures when DE was decreased. Surface roughness of the films increased with this morphological transformation. Nitrogen incorporation increased with decrease in DE which manifested the increase in both relative intensities of Cdbnd N to Cdbnd C and Nsbnd H to Osbnd H bonds. sp2-C to sp3-C ratio increased as DE decreased due to greater deformation of sp2 bonded carbon at lower DE. The films' characteristics changed from hydrophilic to super-hydrophobic with the decrease in DE. Roughness ratio, surface porosity and surface energy calculated from contact angle measurements were strongly dependent on the morphology, surface roughness and bonding properties of the films.

  11. Nitride-based laser diodes grown by plasma-assisted molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Skierbiszewski, C.; Turski, H.; Muziol, G.; Siekacz, M.; Sawicka, M.; Cywiński, G.; Wasilewski, Z. R.; Porowski, S.

    2014-02-01

    The progress in the growth of nitride-based laser diodes (LDs) made by plasma-assisted molecular beam epitaxy (PAMBE) is reviewed. In this work we describe the GaN and InGaN growth peculiarities, p-type doping efficiency, and the properties of InGaN quantum wells (QWs) grown by PAMBE. We demonstrate continuous wave (cw) LDs operating in the range from 410 to 482 nm. These LDs were grown on low dislocation (0 0 0 1) c-plane bulk GaN substrate, which allow one to fabricate cw LDs with a lifetime exceeding 2000 h. Also, the ultraviolet LDs at 388 nm grown on (2 0 -2 1) semipolar substrates are discussed. The use of high active nitrogen fluxes up to 2 µm/h during the InGaN growth was essential for pushing the lasing wavelengths of PAMBE LDs above 460 nm. Recent advancement of InGaN growth by PAMBE allows one to demonstrate high-quality quantum QWs and excellent morphology for thick layers. We discuss the influence of LDs design on their parameters such as lasing threshold current and laser beam quality.

  12. ECR plasma synthesis of silicon nitride films on GaAs and InSb

    SciTech Connect

    Barbour, J.C.; Lovejoy, M.L.; Ashby, C.I.H.; Howard, A.J.; Custer, J.S.; Shul, R.J.

    1993-12-31

    Growth of high-quality dielectric films from Electron Cyclotron Resonance (ECR) plasmas provides for low-temperature surface passivation of compound semiconductors. Silicon nitride (SiN{sub x}) films were grown at temperatures from 30 to 250 C on GaAs substrates. Stress in films was measured as a function of bias applied during growth (varied from 0 to 200 V), and of sample annealing treatments. Composition profiles of the samples were measured using ion beam analysis. The GaAs photoluminescence (PL) signal after SiN{sub x} growth without an applied bias (ion energy {congruent}30 eV) was twice as large as the PL signal from the cleaned GaAs substrate. The PL signal from samples biased at -50 and -100 V indicated that damage degraded the passivation quality, while atomic force microscopy of these samples showed a three fold increase in rms surface roughness relative to unbiased samples. The sample grown with a bias of -200 V showed the largest reduction in film stress but also the smallest PL signal.

  13. Nitrogen-Doped Carbon Fiber Paper by Active Screen Plasma Nitriding and Its Microwave Heating Properties.

    PubMed

    Zhu, Naishu; Ma, Shining; Sun, Xiaofeng

    2016-12-28

    In this paper, active screen plasma nitriding (ASPN) treatment was performed on polyacrylonitrile carbon fiber papers. Electric resistivity and microwave loss factor of carbon fiber were described to establish the relationship between processing parameters and fiber's ability to absorb microwaves. The surface processing effect of carbon fiber could be characterized by dynamic thermal mechanical analyzer testing on composites made of carbon fiber. When the process temperature was at 175 °C, it was conducive to obtaining good performance of dynamical mechanical properties. The treatment provided a way to change microwave heating properties of carbon fiber paper by performing different treatment conditions, such as temperature and time parameters. Atomic force microscope, scanning electron microscope, and X-ray photoelectron spectroscopy analysis showed that, during the course of ASPN treatment on carbon fiber paper, nitrogen group was introduced and silicon group was removed. The treatment of nitrogen-doped carbon fiber paper represented an alternative promising candidate for microwave curing materials used in repairing and heating technology, furthermore, an efficient dielectric layer material for radar-absorbing structure composite in metamaterial technology.

  14. Effect of Low-Energy Ions on Plasma-Enhanced Deposition of Cubic Boron Nitride

    NASA Astrophysics Data System (ADS)

    Torigoe, M.; Fukui, S.; Teii, K.; Matsumoto, S.

    2015-09-01

    The effect of low-energy ions on deposition of cubic boron nitride (cBN) films in an inductively coupled plasma with the chemistry of fluorine is studied in terms of ion energy, ion flux, and ion to boron flux ratio onto the substrate. The ion energy and the ion to boron flux ratio are determined from the sheath potential and the ratio of incident ion flux to net deposited boron flux, respectively. For negative substrate biases where sp2-bonded BN phase only or no deposit is formed, both the ion energy and the ion to boron flux ratio are high. For positive substrate biases where cBN phase is formed, the ion energy and the ion to boron flux ratio are estimated in the range of a few eV to 35 eV and 100 to 130, respectively. The impact of negative ions is presumed to be negligible due to their low kinetic energy relative to the sheath potential over the substrate surface. The impact of positive ions with high ion to boron flux ratios is primarily responsible for reduction of the ion energy for cBN film deposition. Work supported in part by a Grant-in-Aid for Scientific Research (B), a Funding Program for Next Generation World-Leading Researchers, and an Industrial Technology Research Grant Program 2008.

  15. Stress control of silicon nitride films deposited by plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Li, Dong-ling; Feng, Xiao-fei; Wen, Zhi-yu; Shang, Zheng-guo; She, Yin

    2016-07-01

    Stress controllable silicon nitride (SiNx) films deposited by plasma enhanced chemical vapor deposition (PECVD) are reported. Low stress SiNx films were deposited in both high frequency (HF) mode and dual frequency (HF/LF) mode. By optimizing process parameters, stress free (-0.27 MPa) SiNx films were obtained with the deposition rate of 45.5 nm/min and the refractive index of 2.06. Furthermore, at HF/LF mode, the stress is significantly influenced by LF ratio and LF power, and can be controlled to be 10 MPa with the LF ratio of 17% and LF power of 150 W. However, LF power has a little effect on the deposition rate due to the interaction between HF power and LF power. The deposited SiNx films have good mechanical and optical properties, low deposition temperature and controllable stress, and can be widely used in integrated circuit (IC), micro-electro-mechanical systems (MEMS) and bio-MEMS.

  16. Microstructures and Mechanical Performance of Plasma-Nitrided Al0.3CrFe1.5MnNi0.5 High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Tang, Wei-Yeh; Chuang, Ming-Hao; Lin, Su-Jien; Yeh, Jien-Wei

    2012-07-01

    This study investigates the effect of plasma nitriding at 798 K (525 °C) on microstructures and the mechanical performance of Al0.3CrFe1.5MnNi0.5 high-entropy alloys (HEAs) obtained using different cast and wrought processing. All the alloys can be well nitride, with a thickness of around 80 μm, and attain a peak hardness level around Hv 1300 near the surface. The main nitride phases are CrN, AlN, and (Mn, Fe)4N. Those of the substrates are bcc, fcc, Al-, and Ni-rich B2 precipitates, and ρ phase. Their relative amounts depend on the prior processing and also change under the heat treatment during nitriding. The formation of ρ phase during nitriding could in-situ harden the substrate to attain the suitable level required for wear applications. This gives the advantage in simplifying the processing for making a wear-resistance component or a mold since austenitizing, quench hardening, and tempering required for steels such as SACM and SKD steels are no longer required and final finishing can be accomplished before nitriding. Nitrided Al0.3CrFe1.5MnNi0.5 samples have much better wear resistance than un-nitrided ones by 49 to 80 times and also exhibit superior adhesive wear resistance to conventional nitrided alloys: nitriding steel SACM-645 (AISI 7140), 316 stainless steel, and hot-mold steel SKD-61 (AISI H13) by 22 to 55 times depending on prior processing. The superiority is due to the fact that the present nitrided alloys possess a much thicker highly hardened layer than the conventional alloys.

  17. Effect of hydrogen addition on the deposition of titanium nitride thin films in nitrogen added argon magnetron plasma

    NASA Astrophysics Data System (ADS)

    Saikia, P.; Bhuyan, H.; Diaz-Droguett, D. E.; Guzman, F.; Mändl, S.; Saikia, B. K.; Favre, M.; Maze, J. R.; Wyndham, E.

    2016-06-01

    The properties and performance of thin films deposited by plasma assisted processes are closely related to their manufacturing techniques and processes. The objective of the current study is to investigate the modification of plasma parameters occurring during hydrogen addition in N2  +  Ar magnetron plasma used for titanium nitride thin film deposition, and to correlate the measured properties of the deposited thin film with the bulk plasma parameters of the magnetron discharge. From the Langmuir probe measurements, it was observed that the addition of hydrogen led to a decrease of electron density from 8.6 to 6.2  ×  (1014 m-3) and a corresponding increase of electron temperature from 6.30 to 6.74 eV. The optical emission spectroscopy study reveals that with addition of hydrogen, the density of argon ions decreases. The various positive ion species involving hydrogen are found to increase with increase of hydrogen partial pressure in the chamber. The thin films deposited were characterized using standard surface diagnostic tools such as x-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), x-ray diffraction (XRD), Raman spectroscopy (RS), scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). Although it was possible to deposit thin films of titanium nitride with hydrogen addition in nitrogen added argon magnetron plasma, the quality of the thin films deteriorates with higher hydrogen partial pressures.

  18. Radio Frequency Plasma Synthesis of Boron Nitride Nanotubes (BNNTs) for Structural Applications. Part II

    NASA Technical Reports Server (NTRS)

    Hales, Stephen J.; Alexa, Joel A.; Jensen, Brian J.

    2016-01-01

    Boron nitride nanotubes (BNNTs) are more thermally and chemically compatible with metal- and ceramic-matrix composites than carbon nanotubes (CNTs). The lack of an abundant supply of defect-free, high-aspect-ratio BNNTs has hindered development as reinforcing agents in structural materials. Recent activities at the National Research Council - Canada (NRC-C) and the University of California - Berkeley (UC-B) have resulted in bulk synthesis of few-walled, small diameter BNNTs. Both processes employ induction plasma technology to create boron vapor and highly reactive nitrogen species at temperatures in excess of 8000 K. Subsequent recombination under controlled cooling conditions results in the formation of BNNTs at a rate of 20 g/hr and 35 g/hr, respectively. The end product tends to consist of tangled masses of fibril-, sheet-, and cotton candy-like materials, which accumulate within the processing equipment. The radio frequency plasma spray (RFPS) facility at NASA Langley (LaRC), developed for metallic materials deposition, has been re-tooled for in-situ synthesis of BNNTs. The NRC-C and UC-B facilities comprise a 60 kW RF torch, a reactor with a stove pipe geometry, and a filtration system. In contrast, the LaRC facility has a 100 kW torch mounted atop an expansive reaction chamber coupled with a cyclone separator. The intent is to take advantage of both the extra power and the equipment configuration to simultaneously produce and gather BNNTs in a macroscopic form amenable to structural material applications.

  19. Plasma etch characteristics of aluminum nitride mask layers grown by low-temperature plasma enhanced atomic layer deposition in SF{sub 6} based plasmas

    SciTech Connect

    Perros, Alexander; Bosund, Markus; Sajavaara, Timo; Laitinen, Mikko; Sainiemi, Lauri; Huhtio, Teppo; Lipsanen, Harri

    2012-01-15

    The plasma etch characteristics of aluminum nitride (AlN) deposited by low-temperature, 200 deg. C, plasma enhanced atomic layer deposition (PEALD) was investigated for reactive ion etch (RIE) and inductively coupled plasma-reactive ion etch (ICP-RIE) systems using various mixtures of SF{sub 6} and O{sub 2} under different etch conditions. During RIE, the film exhibits good mask properties with etch rates below 10r nm/min. For ICP-RIE processes, the film exhibits exceptionally low etch rates in the subnanometer region with lower platen power. The AlN film's removal occurred through physical mechanisms; consequently, rf power and chamber pressure were the most significant parameters in PEALD AlN film removal because the film was inert to the SF{sub x}{sup +} and O{sup +} chemistries. The etch experiments showed the film to be a resilient masking material. This makes it an attractive candidate for use as an etch mask in demanding SF{sub 6} based plasma etch applications, such as through-wafer etching, or when oxide films are not suitable.

  20. Electron behaviors in afterglow of synchronized dc-imposed pulsed fluorocarbon-based plasmas

    NASA Astrophysics Data System (ADS)

    Ueyama, Toshinari; Fukunaga, Yusuke; Tsutsumi, Takayoshi; Takeda, Keigo; Kondo, Hiroki; Ishikawa, Kenji; Sekine, Makoto; Iwata, Manabu; Ohya, Yoshinobu; Sugai, Hideo; Hori, Masaru

    2017-06-01

    Electron behaviors in a pulsed dual radio frequency (RF) capacitively coupled plasma of a mixture of C4F8, O2, and Ar gases, where the DC bias of -300 V in the RF-on period was imposed and synchronously increased to -1000 V in the RF-off period, were investigated. The synchronous DC bias prolongs the electron density (n e) decay and provides emission of Ar at a wavelength of 750.38 nm in early afterglow at 3 µs during the RF-off period of 10 kHz pulse modulation. The rapid n e decay occurred with the electron attachments to the electronegative fluorocarbons, and thus the plasma consisting of positive and negative ions was generated. The DC bias voltage seems to be applied between the electrodes and the positive ions accelerated to the top electrode, and enhanced the secondary electron generation at the top electrode surface in the RF-off period with the ion bombardments, concomitantly with the synchronous emissions.

  1. New perspectives on the dynamics of AC and DC plasma arcs exposed to cross-fields

    NASA Astrophysics Data System (ADS)

    Abdo, Youssef; Rohani, Vandad; Cauneau, François; Fulcheri, Laurent

    2017-02-01

    Interactions between an arc and external fields are crucially important for the design and the optimization of modern plasma torches. Multiple studies have been conducted to help better understand the behavior of DC and AC current arcs exposed to external and ‘self-induced’ magnetic fields, but the theoretical foundations remain very poorly explored. An analytical investigation has therefore been carried out in order to study the general behavior of DC and AC arcs under the effect of random cross-fields. A simple differential equation describing the general behavior of a planar DC or AC arc has been obtained. Several dimensionless numbers that depend primarily on arc and field parameters and the main arc characteristics (temperature, electric field strength) have also been determined. Their magnitude indicates the general tendency pattern of the arc evolution. The analytical results for many case studies have been validated using an MHD numerical model. The main purpose of this investigation was deriving a practical analytical model for the electric arc, rendering possible its stabilization and control, and the enhancement of the plasma torch power.

  2. FAST TRACK COMMUNICATION: Synthesis of cubic-structured monocrystalline titanium nitride nanoparticles by means of a dual plasma process

    NASA Astrophysics Data System (ADS)

    Tavares, J.; Coulombe, S.; Meunier, J.-L.

    2009-05-01

    Titanium nitride has long been used for its favourable mechanical and chemical properties and it has been demonstrated that monocrystallinity in thin films enhances these properties. While the synthesis of monocrystalline thin films is well documented, common synthesis processes for titanium nitride nanoparticles yield only polycrystalline, spherically shaped powders. The process presented here allows for the synthesis of monocrystalline, cube-shaped nanoparticles by means of a dual plasma process. Pulsed electric arc erosion of a Ti cathode in a N-rich atmosphere produced by a radio-frequency discharge is used for the synthesis of the TiN nanoparticles. Electron microscopy revealed the cubic morphology of the synthesized powders and electron diffraction patterning confirmed the crystalline structure of the TiN nanoparticles.

  3. Deposition of silicon nitride from SiCl4 and NH3 in a low pressure RF plasma

    NASA Technical Reports Server (NTRS)

    Ron, Y.; Raveh, A.; Carmi, U.; Inspektor, A.; Avni, R.

    1983-01-01

    Silicon nitride coatings were deposited in a low-pressure (1-10 Torr) RF plasma from SiCl4 and NH3 in the presence of argon onto stainless martensitic steel grounded and floating substrates at 300 C and 440 C respectively. The heating of the substrates depends mainly on the position and the induced RF power. The coatings were identified as silicon nitride by X-ray investigation and were found to contain chlorine by energy-dispersive analysis of X-rays. The growth rate, the microhardness and the chlorine concentration of the coatings were determined as a function of the total gas pressure, the RF power input and the NH3-to-SiCl4 ratio. It was observed that the coatings on the floating substrates have higher deposition rates and are of superior quality.

  4. Effects of post-deposition argon implantation on the memory properties of plasma-deposited silicon nitride films

    NASA Astrophysics Data System (ADS)

    Shams, Q. A.; Brown, W. D.

    1989-10-01

    Post-deposition ion implantation has been used to introduce argon into plasma-enhanced chemically vapor deposited silicon nitride films in an attempt to influence the transfer, trapping, and emission of charge during write/erase exercising of the metal-silicon nitride-silicon oxide-silicon structure. Argon was implanted into the SiH4 -NH3 -N2 deposited films at energies ranging from 25 to 75 keV, current densities ranging from 0.1 to 75 μA/cm2 and fluences ranging from 1×1012 to 1×1016 ions/cm2. Physical properties of the films were studied by ellipsometry and infrared spectroscopy, while high frequency capacitance-voltage (C-V) curves were used to obtain programming, retention, and endurance characteristics.

  5. Modelling chemical reactions in dc plasma inside oxygen bubbles in water

    NASA Astrophysics Data System (ADS)

    Takeuchi, N.; Ishii, Y.; Yasuoka, K.

    2012-02-01

    Plasmas generated inside oxygen bubbles in water have been developed for water purification. Zero-dimensional numerical simulations were used to investigate the chemical reactions in plasmas driven by dc voltage. The numerical and experimental results of the concentrations of hydrogen peroxide and ozone in the solution were compared with a discharge current between 1 and 7 mA. Upon increasing the water vapour concentration inside bubbles, we saw from the numerical results that the concentration of hydrogen peroxide increased with discharge current, whereas the concentration of ozone decreased. This finding agreed with the experimental results. With an increase in the discharge current, the heat flux from the plasma to the solution increased, and a large amount of water was probably vaporized into the bubbles.

  6. Silica nanoparticles produced by DC arc plasma from a solid raw materials

    NASA Astrophysics Data System (ADS)

    Kosmachev, P. V.; Vlasov, V. A.; Skripnikova, N. K.

    2017-05-01

    Plasma synthesis of SiO2 nanoparticles in experimental atmospheric pressure plasma reactor on the basis of DC arc plasma generator was presented in this paper. Solid high-silica raw materials such as diatomite from Kamyshlovskoye deposit in Russia, quartzite from Chupinskoye deposit in Russia and milled window glass were used. The obtained nanoparticles were characterized based on their morphology, chemical composition and size distribution. Scanning electron microscopy, laser diffractometry, nitrogen absorption (Brunauer-Emmett-Teller method), X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy were used to characterize the synthesized products. The obtained silica nanoparticles are agglomerated, have spherical shape and primary diameters between 10-300 nm. All samples of synthesized nanopowders were compared with commercial nanopowders.

  7. Study of dynamical behaviour of the plasma in a dc non-transferred plasma torch using fast imaging

    NASA Astrophysics Data System (ADS)

    Goyal, Vidhi; Ravi, G.; Bandyopadhyay, P.; Banerjee, S.; Yugesh, V.; Mukherjee, S.

    2017-03-01

    The dynamical behaviour of the plasma in a dc non-transferred plasma torch is the result of complex interactions between various forces acting on the plasma column. We have studied this behaviour in a novel experiment comprising a low power (˜25 kW) torch and fast imaging diagnostics. The nitrogen gas plasma torch was operated at atmospheric pressure for a wide range of gas flow rates (20-60 lpm) and currents (70-120 A). A strong axial external magnetic field (100-500 G) was introduced and end-on images of the plasma column were captured using a high speed camera of frame rate ˜117 000 fps. The studies have yielded dominant role of external magnetic on the arc root dynamics. The column is clearly distinguishable in three main parts: central plasma, cathode-anode junction, and radial component of column that attaches to the anode. The dynamics of the column, especially the angular rotational speed of the radial part of the column, is analyzed in detail in terms of the forces that act upon it. The nature of the arc root attachment is observed to vary with variation in main experimental parameters, such as current, magnetic field, and flow. Arguments are invoked to explain the observed phenomena and a model of the physical processes is presented to explain the phenomena.

  8. Formation of Equiaxed Alpha and Titanium Nitride Precipitates in Spark Plasma Sintered TiB/Ti-6Al-4V Composites (Preprint)

    DTIC Science & Technology

    2012-08-01

    AFRL-RX-WP-TP-2012-0372 FORMATION OF EQUIAXED ALPHA AND TITANIUM NITRIDE PRECIPITATES IN SPARK PLASMA SINTERED TiB/Ti-6Al-4V COMPOSITES...ALPHA AND TITANIUM NITRIDE PRECIPITATES IN SPARK PLASMA SINTERED TiB/Ti-6Al-4V COMPOSITES (PREPRINT) 5a. CONTRACT NUMBER FA8650-08-C-5226 5b...distribution of TiN precipitates, as revealed by TEM studies. 15. SUBJECT TERMS Ti-6Al-4V; TiB; TiN; Spark Plasma Sintering ; Composite; α/β phase

  9. SF6/O2 plasma effects on silicon nitride passivation of AlGaN /GaN high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Meyer, David J.; Flemish, Joseph R.; Redwing, Joan M.

    2006-11-01

    The effects of various plasma and wet chemical surface pretreatments on the electrical characteristics of AlGaN /GaN high electron mobility transistors (HEMTs) passivated with plasma-deposited silicon nitride were investigated. The results of pulsed IV measurements show that samples exposed to various SF6/O2 plasma treatments have markedly better rf dispersion characteristics compared to samples that were either untreated or treated in wet buffered oxide etch prior to encapsulation. The improvement in these characteristics correlates with the reduction of carbon on the semiconductor surface as measured with x-ray photoelectron spectroscopy. HEMT channel sheet resistance was also affected by varying silicon nitride deposition parameters.

  10. A simplified analytical model for dc plasma spray torch: influence of gas properties and experimental conditions

    NASA Astrophysics Data System (ADS)

    Rat, V.; Coudert, J. F.

    2006-11-01

    A simplified analytical model is proposed to evaluate some characteristics of the arc jet generated with a dc plasma torch, in the restricted area of atmospheric plasma spraying conditions. The plasma inside the anode nozzle is considered as stationary and is divided into the arc column and a surrounding cold layer which electrically insulates the plasma from the nozzle wall. Radiation and processes related to the arc attachment at the electrodes are not explicitly taken into account. Heat conduction is evaluated by using Kirchoff's potential, which is described, as it is done also for the electrical conductivity, as a function of the gas specific enthalpy instead of temperature. The model is used to calculate the specific enthalpy radial distribution. From that, and by introducing a mean isentropic coefficient, it is possible to calculate the axial velocity of the plasma jet at the nozzle exit and to evaluate the different pressure contributions. The comparison between predicted and previously measured plasma jet velocities shows good agreement for various experimental conditions.

  11. Effects of Gas Flow Rate on the Discharge Characteristics of a DC Excited Plasma Jet

    NASA Astrophysics Data System (ADS)

    Li, Xuechen; Jia, Pengying; Di, Cong; Bao, Wenting; Zhang, Chunyan

    2015-09-01

    A direct current (DC) source excited plasma jet consisting of a hollow needle anode and a plate cathode has been developed to form a diffuse discharge plume in ambient air with flowing argon as the working gas. Using optical and electrical methods, the discharge characteristics are investigated for the diffuse plasma plume. Results indicate that the discharge has a pulse characteristic, under the excitation of a DC voltage. The discharge pulse corresponds to the propagation process of a plasma bullet travelling from the anode to the cathode. It is found that, with an increment of the gas flow rate, both the discharge plume length and the current peak value of the pulsed discharge decrease in the laminar flow mode, reach their minima at about 1.5 L/min, and then slightly increase in the turbulent mode. However, the frequency of the pulsed discharge increases in the laminar mode with increasing the argon flow rate until the argon flow rate equals to about 1.5 L/min, and then slightly decreases in the turbulent mode. supported by National Natural Science Foundation of China (Nos. 10805013, 11375051), Funds for Distinguished Young Scientists of Hebei Province, China (No. A2012201045), Department of Education for Outstanding Youth Project of China (No. Y2011120), and Youth Project of Hebei University of China (No. 2011Q14)

  12. Discharge modes of a DC operated atmospheric pressure air plasma jet

    NASA Astrophysics Data System (ADS)

    Kolb, Juergen; Pei, Xuekai; Kredl, Jana; Lu, Xinpei

    2016-09-01

    By flowing air or nitrogen through a microhollow cathode discharge geometry an afterglow plasma jet can be generated at atmospheric pressure in air. The plasma jet has been successfully used for the inactivation of bacteria and yeast. The responsible reaction chemistry is based on the production of high concentrations of nitric oxide. Production yields depend in particular on gas flow rate and energy dissipated in the plasma. The same parameters also determine different modes of operation for the jet. A true DC operation is achieved for low to moderate gas flow rate of about 1 slm and discharge currents on the order of 10 mA. When increasing the gas flow rate to 10 slm the operation is changing to a self-pulsing mode with characteristics similar to the ones observed for a transient spark. By increasing the current a DC operation can be achieved again also at higher gas flow rates. The parameter regimes for different modes of operation can be described by the reduced electric field E/N.

  13. Towards long-lasting antibacterial stainless steel surfaces by combining double glow plasma silvering with active screen plasma nitriding.

    PubMed

    Dong, Y; Li, X; Tian, L; Bell, T; Sammons, R L; Dong, H

    2011-01-01

    Antibacterial surface modification of biomedical materials has evolved as a potentially effective method for preventing bacterial proliferation on the surfaces of devices. However, thin antibacterial coatings or modified layers can be easily worn down when interacting with other surfaces in relative motion, thus leading to a low durability of the antibacterial surface. To this end, novel biomaterial surfaces with antibacterial Ag agents and a wear-resistant S-phase have been generated on stainless steel by duplex plasma silvering-nitriding techniques for application to load-bearing medical devices. The chemical composition, microstructure, surface topography, roughness and wettability of SS surfaces were characterised using glow discharge optical emission spectroscopy, energy-dispersive spectroscopy/wavelength dispersive spectrometry (WDS), X-ray diffraction, atomic force microscopy and a contact angle goniometer. Optimal surface design for high antimicrobial activity and prolonged durability has been achieved, as evidenced by rapid bacterial killing rates (within 6h), an ultra hard matrix (875 ± 25 Hv), high load-bearing capacity (critical load 37 N) and excellent wear resistance (wear rate 4.9 × 10⁻⁶ mm³ m⁻¹). Ag embedded in the hard substrate of fcc compounds M(4)N (M=Fe, Cr, Ag, etc.) and the expanded fcc nitrogen S-phase shows deep infiltration of 6 ± 1 μm, and provides bactericidal activity against both Gram-negative Escherichia coli NCTC 10418 and Gram-positive Staphylococcus epidermidis NCTC 11047 of over 97% and 90%, respectively, within 6h. The presence of silver in the surface before and after scratching under a progressive load applied up to 60 N using a diamond stylus was confirmed by WDS.

  14. Aerosynthesis: Growths of Vertically Aligned Carbon Nanofibers with Air DC Plasma

    SciTech Connect

    Kodumagulla, A; Varanasi, V; Pearce, Ryan; Wu, W-C; Hensley, Dale K; Tracy, Joseph B; McKnight, Timothy E; Melechko, Anatoli

    2014-01-01

    Vertically aligned carbon nanofibers (VACNF) have been synthesized in a mixture of acetone and air using catalytic DC plasma enhanced chemical vapor deposition. Typically, ammonia or hydrogen is used as etchant gas in the mixture to remove carbon that otherwise passivates the catalyst surface and impedes growth. Our demonstration of using air as the etchant gas opens up a possibility that ion etching could be sufficient to maintain the catalytic activity state during synthesis. It also demonstrates the path toward growing VACNFs in open atmosphere.

  15. Anomalous response of supported few-layer hexagonal boron nitride to DC electric fields: a confined water effect?

    NASA Astrophysics Data System (ADS)

    Oliveira, Camilla; Matos, Matheus; Mazzoni, Mário; Chacham, Hélio; Neves, Bernardo

    2013-03-01

    Hexagonal boron nitride (h-BN) is a two-dimensional compound from III-V family, with the atoms of boron and nitrogen arranged in a honeycomb lattice, similar to graphene. Unlike graphene though, h-BN is an insulator material, with a gap larger than 5 eV. Here, we use Electric Force Microscopy (EFM) to study the electrical response of mono and few-layers of h-BN to an electric field applied by the EFM tip. Our results show an anomalous behavior in the dielectric response for h-BN for different bias orientation: for a positive bias applied to the tip, h-BN layers respond with a larger dielectric constant than the dielectric constant of the silicon dioxide substrate; while for a negative bias, the h-BN dielectric constant is smaller than the dielectric constant of the substrate. Based on first-principles calculations, we showed that this anomalous response may be interpreted as a macroscopic consequence of confinement of a thin water layer between h-BN and substrate. These results were confirmed by sample annealing and also also by a comparative analysis with h-BN on a non-polar substrate. All the authors acknowledge financial support from CNPq, Fapemig, Rede Nacional de Pesquisa em Nanotubos de Carbono and INCT-Nano-Carbono.

  16. Deposition of magnesium nitride thin films on stainless steel-304 substrates by using a plasma focus device

    NASA Astrophysics Data System (ADS)

    Ramezani, Amir Hoshang; Habibi, Maryam; Ghoranneviss, Mahmood

    2014-08-01

    In this research, for the first time, we synthesize magnesium nitride thin films on 304-type stainless steel substrates using a Mather-type (2 kJ) plasma focus (PF) device. The films of magnesium nitride are coated with different number of focus shots (like 15, 25 and 35) at a distance of 8 cm from the anode tip and at 0° angular position with respect to the anode axis. For investigation of the structural properties and surface morphology of magnesium nitride films, we utilized the X-ray diffractometer (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) analysis, respectively. Also, the elemental composition is characterized by energy-dispersive X-ray (EDX) analysis. Furthermore, Vicker's microhardness is used to study the mechanical properties of the deposited films. The results show that the degree of crystallinity of deposited thin films (from XRD), the average size of particles and surface roughness (from AFM), crystalline growth of structures (from SEM) and the hardness values of the films depend on the number of focus shots. The EDX analysis demonstrates the existence of the elemental composition of magnesium in the deposited samples.

  17. Effect of deposition parameters on structural and mechanical properties of niobium nitride synthesized by plasma focus device

    NASA Astrophysics Data System (ADS)

    Siddiqui, Jamil; Hussain, Tousif; Ahmad, Riaz; Khalid, Nida

    2015-06-01

    Effects of deposition angle and axial distance on the structural and mechanical properties of niobium nitride synthesized by a dense plasma focus (DPF) system are studied. The x-ray diffraction (XRD) confirms that the deposition parameters affect the growth of multi-phase niobium nitride. Scanning electron microscopy (SEM) shows the granular surface morphology with strong thermally assisted coagulation effects observed at the 5-cm axial distance. The non-porous granular morphology observed at the 9-cm distance along the anode axis is different from those observed at deposition angles of 10° and 20°. Energy dispersive x-ray (EDX) spectroscopy reveals the maximum nitrogen content at the shortest (5 cm) axial position. Atomic force microscopy (AFM) exhibits that the roughness of coated films varies for coatings synthesized at different axial and angular positions, and the Vickers micro-hardness test shows that a maximum hardness value is (08.44 ± 0.01) GPa for niobium nitride synthesized at 5-cm axial distance, which is about 500% more than that of a virgin sample. Project supported by the HEC, Pakistan.

  18. Heating mechanisms and particle flow balancing of capacitively coupled plasmas driven by combined dc/rf sources

    SciTech Connect

    Jiang Wei; Xu Xiang; Dai Zhongling; Wang Younian

    2008-03-15

    Heating mechanisms and particle flow balancing of capacitively coupled plasmas driven by combined dc/rf sources have been investigated by particle-in-cell/Monte Carlo simulations. At low pressure, Ohmic heating will be suppressed and stochastic heating will be enhanced while increasing dc voltage. But the overall heating power will decrease. No heating mode transitions are observed. At high pressure, bulk plasma density decreases at low dc and rf voltage, and the one-side {alpha}-{gamma} transition will occur while increasing dc voltage. After the transition, the plasma density abruptly increases and average electron energy drops. As the result of that, the plasma is sustained by secondary electrons instead of the Ohmic heating of the bulk electrons. The dc source will reduce, or even eliminate at high voltage, the electron charge flowing into the dc powered electrode. Therefore the ratio of electron-to-ion charge flowing into the rf powered electrode over one period increases from -1.0 to -2.0--2.3 for low pressure and -2.2--5.0 for high pressure.

  19. Study on effect of plasma surface treatments for diamond deposition by DC arc plasmatron.

    PubMed

    Kang, In-Je; Joa, Sang-Beom; Lee, Heon-Ju

    2013-11-01

    To improve the thermal conductivity and wear resistance of ceramic materials in the field of renewable energy technologies, diamond coating by plasma processing has been carried out in recent years. This study's goal is to improve diamond deposition on Al2O3 ceramic substrates by plasma surface treatments. Before diamond deposition was carried out in a vacuum, plasma surface treatments using Ar gas were conducted to improve conditions for deposition. We also conducted plasma processing for diamond deposition on Al2O3 ceramic substrates using a DC arc Plasmatron. The Al2O3 ceramic substrates with diamond film (5 x 15 mm2), were investigated by SEM (Scanning Electron Microscopy), AFM (Atomic Force Microscopy) and XRD (X-ray Diffractometer). Then, the C-H stretching of synthetic diamond films by FTIR (Fourier Transform Infrared Spectroscopy) was studied. We identified nanocrystalline diamond films on the Al2O3 ceramic substrates. The results showed us that the deposition rate of diamond films was 2.3 microm/h after plasma surface treatments. Comparing the above result with untreated ceramic substrates, the deposition rate improved with the surface roughness of the deposited diamond films.

  20. Mixed mode oscillations in presence of inverted fireball in an excitable DC glow discharge magnetized plasma

    NASA Astrophysics Data System (ADS)

    Mitra, Vramori; Prakash, N. Hari; Solomon, Infant; Megalingam, Mariammal; Sekar Iyengar, A. N.; Marwan, Norbert; Kurths, Jürgen; Sarma, Arun; Sarma, Bornali

    2017-02-01

    The typical phenomena of mixed mode oscillations and their associated nonlinear behaviors have been investigated in collisionless magnetized plasma oscillations in a DC glow discharge plasma system. Plasma is produced between a cylindrical mesh grid and a constricted anode. A spherical mesh grid of 80% optical transparency is kept inside a cylindrical grid to produce an inverted fireball. Three Langmuir probes are kept in the ambient plasma to measure the floating potential fluctuations at different positions of the chamber. It has been observed that under certain conditions of discharge voltages and magnetic fields, the mixed mode oscillation phenomena (MMOs) appears, and it shows a sequential alteration with the variation of the magnetic fields and probe positions. Low frequency instability has been observed consistently in various experimental conditions. The mechanisms of the low frequency instabilities along with the origin of the MMOs have been qualitatively explained. Extensive linear and nonlinear analysis using techniques such as fast Fourier transform, recurrence quantification analysis, and the well-known statistical computing, skewness, and kurtosis are carried out to explore the complex dynamics of the MMO appearing in the plasma oscillations under various discharge conditions and external magnetic fields.

  1. Influence of injected silver content on synthesis of silver coated nickel particles by DC thermal plasma

    NASA Astrophysics Data System (ADS)

    Park, Si Taek; Kim, Tae-Hee; Park, Dong-Wha

    2016-06-01

    Silver nanoparticle-coated spherical nickel particles were prepared from a mixture of micro-sized silver and nickel as raw materials by DC thermal plasma treatment. The mixture of micro-sized silver and nickel powders was injected into the high-temperature region of an argon thermal plasma jet. Although the silver, with its very high thermal conductivity and relatively low boiling point, was thoroughly evaporated by this process, nickel was not evaporated perfectly because of its comparatively low thermal conductivity and high boiling point. The rough nickel powder was spheroidized as it melted. Finally, silver evaporated by the thermal plasma quickly condensed into nanoparticles on the surfaces of the micro-sized spherical nickel particles, aided by the sharp temperature gradient of the thermal plasma jet. With varying the ratios of silver to nickel feedstock from 1:10 to 5:1, the products synthesized in each condition were examined by XRD, XPS, FE-SEM, and FE-TEM. More silver nanoparticles were attached on the nickel by increasing the injected feedstock to 9.8 at% silver. Meanwhile, a decrease of silver in the products was observed when larger amounts of silver were introduced to the thermal plasma jet. The exposed silver components decreased with greater proportions of silver feedstock because of the metal's dendritic structure and the formation of silver-coated silver particles.

  2. The Influence of Plasma Nitriding Pre-Treatment on Tribological Properties of TiN Coatings Deposited by PACVD

    NASA Astrophysics Data System (ADS)

    Mahdipoor, M. S.; Mahboubi, F.; Ahangarani, Sh.; Raoufi, M.; Elmkhah, H.

    2012-06-01

    The aim of this study is to investigate the effect of plasma nitriding pre-treatment (PN) on mechanical and tribological behavior of TiN coatings produced by plasma-assisted chemical vapor deposition (PACVD). The heat treatment of quench and temper was carried out on hot work AISI H11 (DIN 1.2343) steel samples. A group of samples were plasma nitrided at 500 °C for 4 h in an atmosphere containing 25 vol.% nitrogen and 75 vol.% hydrogen. Then TiN layer was deposited on all of samples at 520 °C temperature, 8 kHz frequency, and 33% duty cycle. The microstructural, mechanical, and tribological properties of the coatings were investigated using SEM, WDS, AFM, microhardness tester, and pin-on-disc wear test. The load of wear test was 10 N and the samples were worn against different pins, ball-bearing steel (DIN 1.3505), and cemented tungsten carbide (WC-Co). The results indicate that the difference of hardness between the samples with PN-TiNlayer and those samples with only TiN layer without PN was 450 HV and the former samples showed a significant amount of wear resistance in comparison to the latter ones.

  3. Role of GaAs surface clearing in plasma deposition of silicon nitride films for encapsulated annealing

    NASA Technical Reports Server (NTRS)

    Valco, G. J.; Kapoor, V. J.

    1985-01-01

    The role of GaAs surface cleaning and plasma reactor cleaning prior to deposition of silicon nitride films for encapsulated annealing has been investigated. X-ray photoelectron spectroscopy was employed to determine the surface characteristics of GaAs treated with HCl, HF, and NH4OH solutions preceded by a degreasing procedure. The HCl clean left the least amount of oxygen on the surface. Fluorine contamination resulting from the CF4 plasma used to clean the reactor was found to be located at the film-substrate interface by Auger electron spectroscopy with argon-ion sputtering. A modified deposition procedure was developed to eliminate the fluorine contamination. Plasma deposition of silicon nitride encapsulating films was found to modify the I-V characteristics of Schottky diodes subsequently formed on GaAs surface. The reverse current of the diodes was slightly reduced. Substrates implanted with Si at 100 keV and a dose of 5 x 10 to the 12th/sq cm showed a peak electron concentration of 1.7 x 10 to the 17th/cu cm at a depth of 0.1-micron with 60 percent activation after encapsulation and annealing at 800 C for 7 min.

  4. Role of GaAs surface clearing in plasma deposition of silicon nitride films for encapsulated annealing

    NASA Technical Reports Server (NTRS)

    Valco, G. J.; Kapoor, V. J.

    1985-01-01

    The role of GaAs surface cleaning and plasma reactor cleaning prior to deposition of silicon nitride films for encapsulated annealing has been investigated. X-ray photoelectron spectroscopy was employed to determine the surface characteristics of GaAs treated with HCl, HF, and NH4OH solutions preceded by a degreasing procedure. The HCl clean left the least amount of oxygen on the surface. Fluorine contamination resulting from the CF4 plasma used to clean the reactor was found to be located at the film-substrate interface by Auger electron spectroscopy with argon-ion sputtering. A modified deposition procedure was developed to eliminate the fluorine contamination. Plasma deposition of silicon nitride encapsulating films was found to modify the I-V characteristics of Schottky diodes subsequently formed on GaAs surface. The reverse current of the diodes was slightly reduced. Substrates implanted with Si at 100 keV and a dose of 5 x 10 to the 12th/sq cm showed a peak electron concentration of 1.7 x 10 to the 17th/cu cm at a depth of 0.1-micron with 60 percent activation after encapsulation and annealing at 800 C for 7 min.

  5. Structural and Dynamical Properties of Microrod Dusty Plasma in a Uniform DC Discharge under Microgravity

    SciTech Connect

    Usachev, Alexander; Zobnin, Andrey; Petrov, Oleg; Fortov, Vladimir

    2008-09-07

    In present experiment an ordering and dynamics of monodisperse nylon rods (D = 10 {mu}m, L = 300 {mu}m) in a uniform DC gas discharge plasma under microgravity have been investigated. Ordered rod structures were registered in DC discharge with a rod concentration of 400-8000 cm{sup -3} and a neon pressure range of 20-50 Pa. The structures revealed orientationally ordered hexagonal structures. DC discharge became unstable at rod number density more then 8000 cm{sup -3}. Rod drift velocities in a permanent electric field were measured for the neon pressure range. Dust acoustic instability ({nu}{approx}0.4{+-}0.1 Hz, {lambda}{approx}1.1{+-}0.4 cm, C{sub DAW}{approx}0.5 cm/s) in rod cloud was observed at a neon pressure of 25 Pa and a rod number density of 1500 cm{sup -3}. Using the 'low' frequency approximation of the linearized DAW dispersion relation and the measured rod drift velocity a rod electric charge had been estimated as Z{sub R}{approx}150000e.

  6. Desorption behavior of zinc atoms from zinc-sulfate solution irradiated with pulsed DC plasma

    NASA Astrophysics Data System (ADS)

    Takaba, Takafumi; Suzuki, Haruka; Toyoda, Hirotaka

    2016-07-01

    A DC pulsed plasma ignited between a metal needle and zinc sulfate (ZnSO4) solution electrode was used to investigate Zn metal desorption from an electrolyte solution. Using an ICCD camera and optical band-pass filter, 2D atomic absorption spectroscopy was carried out during irradiation of pulsed plasma to the surface of the solution. The time-resolved measurement of Zn atoms released to the gas phase revealed that the Zn desorption rate monotonically increased with increasing number of discharge repetitions. The surface temperature of the electrolyte solution was observed with a thermographic camera, and correlations between the H2O and Zn desorption rate were inspected. The correlation between the H2O and Zn desorption rate suggested that Zn desorption is assisted not only by the electric field of the discharge but also by H2O evaporating from the solution.

  7. Formation of ultrasharp vertically aligned Cu-Si nanocones by a DC plasma process.

    PubMed

    Klein, K L; Melechko, A V; Fowlkes, J D; Rack, P D; Hensley, D K; Meyer, H M; Allard, L F; McKnight, T E; Simpson, M L

    2006-03-16

    We report an effective method for the production of ultrasharp vertically oriented silicon nanocones with tip radii as small as 5 nm. These silicon nanostructures were shaped by a high-temperature acetylene and ammonia dc plasma reactive ion etch (RIE) process. Thin-film copper deposited onto Si substrates forms a copper silicide (Cu3Si) during plasma processing, which subsequently acts as a seed material masking the single-crystal cones while the exposed silicon areas are reactive ion etched. In this process, the cone angle is sharpened continually as the structure becomes taller. Furthermore, by lithographically defining the seed material as well as employing an etch barrier material such as titanium, the cone location and substrate topography can be controlled effectively.

  8. 'PK-4' - Laser-driven shear flow in a DC discharge complex plasma

    SciTech Connect

    Kretschmer, M.; Hoefner, H.; Thoma, M.; Fink, M.; Ratynskaia, S.; Morfill, G.; Tarantik, K.; Fortov, V.; Petrov, O.; Usachev, A.; Zobnin, A.; Gerasimov, Yu.

    2005-10-31

    Flows, shear flows, laminar and turbulent flows on the microscopic scales are one of the fundamental issues in fluid dynamics. Due to their special properties, complex plasmas provide an excellent opportunity to study these flows, even on the scale of individual particles. To this end, experiments were conducted in the 'Plasmakristall 4' (PK-4) experimental device that uses the positive column of a high voltage DC discharge to produce complex (dusty) plasmas. The linear geometry of PK-4 provides the opportunity to study all these kinds of flow phenomena as well as waves and collisions. Since gravity distorts most of the effects to be studied with PK-4, the facility is planned to be operated onboard the International Space Station ISS from 2008. In order to generate a high-velocity shear flow PK-4 is now upgraded with a 20W manipulation laser system.

  9. Role of sapphire nitridation temperature on GaN growth by plasma assisted molecular beam epitaxy: Part II. Interplay between chemistry and structure of layers

    NASA Astrophysics Data System (ADS)

    Losurdo, Maria; Capezzuto, Pio; Bruno, Giovanni; Namkoong, Gon; Doolittle, W. Alan; Brown, April S.

    2002-02-01

    The effect of sapphire nitridation temperature on the chemistry and microstructure of the sapphire substrate/GaN interface, nucleation layer, and of the GaN epilayers grown by rf plasma assisted molecular beam epitaxy is investigated. It is found that a sapphire nitridation temperature as low as 200 °C improves the structural and optical quality of GaN epilayers. This result can be explained by the chemistry of the sapphire nitridation process, which is discussed in the framework of a model considering the competitive formation of AlN and oxynitride (NO). In particular, at 200 °C, NO desorbs from the sapphire surface, yielding an homogeneous 6 Å AlN layer upon N2 plasma nitridation. This low temperature AlN template favors the nucleation of hexagonal GaN nuclei which coalesce completely resulting in a hexagonal GaN buffer layer that homogeneously covers the sapphire substrate. This condition promotes the growth of a high quality GaN epilayer. In contrast, high nitridation temperatures result in a mixed AlN/NO nitrided sapphire surface which induce a perturbed and more defected interface with the occurrence of cubic crystallites in the GaN buffer. A sapphire surface with random GaN islands is found upon annealing of the GaN buffer and this condition results in a low-quality GaN epilayer.

  10. Inertization of heavy metals present in galvanic sludge by DC thermal plasma.

    PubMed

    Leal Vieira Cubas, Anelise; de Medeiros Machado, Marília; de Medeiros Machado, Marina; Gross, Frederico; Magnago, Rachel Faverzani; Moecke, Elisa Helena Siegel; Gonçalvez de Souza, Ivan

    2014-01-01

    Galvanic sludge results from the treatment of effluents generated by the industrial metal surface treatment of industrial material, which consists in the deposition of a metal on a surface or a metal surface attack, for example, electrodeposition of conductors (metals) and non conductive, phosphate, anodizing, oxidation and/or printed circuit. The treatment proposed here is exposure of the galvanic sludge to the high temperatures provided by thermal plasma, a process which aims to vitrify the galvanic sludge and render metals (iron, zinc, and chromium) inert. Two different plasma reactors were assembled: with a DC transferred arc plasma torch and with a DC nontransferred arc plasma torch. In this way it was possible to verify which reactor was more efficient in the inertization of the metals and also to investigate whether the addition of quartzite sand to the sludge influences the vitrification of the material. Quantification of water content and density of the galvanic raw sludge were performed, as well as analyzes of total organic carbon (TOC) and identify the elements that make up the raw sludge through spectroscopy X-ray fluorescence (XRF). The chemical composition and the form of the pyrolyzed and vitrified sludge were analyzed by scanning electron microscopy with energy-dispersive X-ray spectrometer (SEM-EDS) analysis, which it is a analysis that shows the chemical of the sample surface. The inertization of the sludge was verified in leaching tests, where the leachate was analyzed by flame atomic absorption spectroscopy (FAAS). The results of water content and density were 64.35% and 2.994 g.cm(-3), respectively. The TOC analysis determined 1.73% of C in the sample of galvanic raw sludge, and XRF analysis determined the most stable elements in the sample, and showed the highest peaks (higher stability) were Fe, Zn, and Cr. The efficiency of the sludge inertization was 100% for chromium, 99% for zinc, and 100% for iron. The results also showed that the most

  11. Structured DC Electric Fields With and Without Associated Plasma Density Gradients Observed with the C/NOFS Satellite

    NASA Technical Reports Server (NTRS)

    Pfaff, R.; Rowland, D.; Klenzing, J.; Freudenreich, H.; Bromund, K.; Liebrecht, C.; Roddy, P.; Hunton, D.

    2009-01-01

    DC electric field observations and associated plasma drifts gathered with the Vector Electric Field Investigation on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite typically reveal considerable variation at large scales (approximately 100's of km), in both daytime and nighttime cases, with enhanced structures usually confined to the nightside. Although such electric field structures are typically associated with plasma density depletions and structures, as observed by the Planar Langmuir Probe on C/NOFS, what is surprising is the number of cases in which large amplitude, structured DC electric fields are observed without a significant plasma density counterpart structure, including their appearance at times when the ambient plasma density appears relatively quiescent. We investigate the relationship of such structured DC electric fields and the ambient plasma density in the C/NOFS satellite measurements observed thus far, taking into account both plasma density depletions and enhancements. We investigate the mapping of the electric fields along magnetic field lines from distant altitudes and latitudes to locations where the density structures, which presumably formed the original seat of the electric fields, are no longer discernible in the observations. In some cases, the electric field structures and spectral characteristics appear to mimic those associated with equatorial spread-F processes, providing important clues to their origins. We examine altitude, seasonal, and longitudinal effects in an effort to establish the origin of such structured DC electric fields observed both with, and without, associated plasma density gradients

  12. DC Electric Fields, Associated Plasma Drifts, and Irregularities Observed on the C/NOFS Satellite

    NASA Technical Reports Server (NTRS)

    Pfaff, R.; Freudenreich, H.; Klenzing, J.

    2011-01-01

    Results are presented from the Vector Electric Field Investigation (VEFI) on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite, a mission designed to understand, model, and forecast the presence of equatorial ionospheric irregularities. The VEFI instrument includes a vector DC electric field detector, a fixed-bias Langmuir probe operating in the ion saturation regime, a flux gate magnetometer, an optical lightning detector, and associated electronics including a burst memory. Compared to data obtained during more active solar conditions, the ambient DC electric fields and their associated E x B drifts are variable and somewhat weak, typically < 1 mV/m. Although average drift directions show similarities to those previously reported, eastward/outward during day and westward/downward at night, this pattern varies significantly with longitude and is not always present. Daytime vertical drifts near the magnetic equator are largest after sunrise, with smaller average velocities after noon. Little or no pre-reversal enhancement in the vertical drift near sunset is observed, attributable to the solar minimum conditions creating a much reduced neutral dynamo at the satellite altitude. The nighttime ionosphere is characterized by larger amplitude, structured electric fields, even where the plasma density appears nearly quiescent. Data from successive orbits reveal that the vertical drifts and plasma density are both clearly organized with longitude. The spread-F density depletions and corresponding electric fields that have been detected thus far have displayed a preponderance to appear between midnight and dawn. Associated with the narrow plasma depletions that are detected are broad spectra of electric field and plasma density irregularities for which a full vector set of measurements is available for detailed study. The VEFI data represents a new set of measurements that are germane to numerous fundamental aspects of the electrodynamics

  13. Numerical simulation of Trichel pulses of negative DC corona discharge based on a plasma chemical model

    NASA Astrophysics Data System (ADS)

    Chen, Xiaoyue; Lan, Lei; Lu, Hailiang; Wang, Yu; Wen, Xishan; Du, Xinyu; He, Wangling

    2017-10-01

    A numerical simulation method of negative direct current (DC) corona discharge based on a plasma chemical model is presented, and a coaxial cylindrical gap is adopted. There were 15 particle species and 61 kinds of collision reactions electrons involved, and 22 kinds of reactions between ions are considered in plasma chemical reactions. Based on this method, continuous Trichel pulses are calculated on about a 100 us timescale, and microcosmic physicochemical process of negative DC corona discharge in three different periods is discussed. The obtained results show that the amplitude of Trichel pulses is between 1–2 mA, and that pulse interval is in the order of 10‑5 s. The positive ions produced by avalanche ionization enhanced the electric field near the cathode at the beginning of the pulse, then disappeared from the surface of cathode. The electric field decreases and the pulse ceases to develop. The negative ions produced by attachment slowly move away from the cathode, and the electric field increases gradually until the next pulse begins to develop. The positive and negative ions with the highest density during the corona discharge process are O4+ and O3- , respectively.

  14. Synthesis of silicon carbide from rice husk in a dc arc plasma reactor

    SciTech Connect

    Nayak, B.B.; Mohanty, B.C.; Singh, S.K.

    1996-05-01

    SiC particles have been synthesized in the {alpha}-phase from a mixture of boiler-burnt rice husk and graphite powder in a dc extended arc plasma reactor on a 200--250 g scale. A SiC yield as high as 72% was achieved at a 3.03:1 carbon-to-silica ratio. 21R polytypism, which is rare to grow, was observed in the SiC. About 90% of the SiC particles produced were found to lie under 163 {micro}m, 50% under 90 {micro}m, and 10% under 28 {micro}m size. Very fine particles under 10 {micro}m size occurred to the extent of 3%. XRD and SEM characterizations were carried out to study the phase and morphology of the particles. Heterogeneous gas-phase reactions seem to be responsible for intermediate-size SiC particle growth in the multitemperature zone dc extended arc plasma reactor.

  15. Production of geopolymers using glass produced from DC plasma treatment of air pollution control (APC) residues.

    PubMed

    Kourti, Ioanna; Rani, D Amutha; Deegan, D; Boccaccini, A R; Cheeseman, C R

    2010-04-15

    Air pollution control (APC) residues are the hazardous waste produced from cleaning gaseous emissions at energy-from-waste (EfW) facilities processing municipal solid waste (MSW). APC residues have been blended with glass-forming additives and treated using DC plasma technology to produce a high calcium alumino-silicate glass. This research has investigated the optimisation and properties of geopolymers prepared from this glass. Work has shown that high strength geopolymers can be formed and that the NaOH concentration of the activating solution significantly affects the properties. The broad particle size distribution of the APC residue glass used in these experiments results in a microstructure that contains unreacted glass particles included within a geopolymer binder phase. The high calcium content of APC residues may cause the formation of some amorphous calcium silicate hydrate (C-S-H) gel. A mix prepared with S/L=3.4, Si/Al=2.6 and [NaOH]=6M in the activating solution, produced high strength geopolymers with compressive strengths of approximately 130 MPa. This material had high density (2070 kg/m(3)) and low porosity. The research demonstrates for the first time that glass derived from DC plasma treatment of APC residues can be used to form high strength geopolymer-glass composites that have potential for use in a range of applications.

  16. Hydrogenation of defects in edge-defined film-fed grown aluminum-enhanced plasma enhanced chemical vapor deposited silicon nitride multicrystalline silicon

    NASA Astrophysics Data System (ADS)

    Jeong, Ji-Weon; Rosenblum, Mark D.; Kalejs, Juris P.; Rohatgi, Ajeet

    2000-05-01

    Gettering of impurities and hydrogen passivation of defects in edge-defined film-fed grown (EFG) multicrystalline silicon were studied by low-cost manufacturable technologies such as emitter diffusion by a spin-on phosphorus dopant source, back surface field formation by screen-printed aluminum, and a post-deposition anneal of plasma enhanced chemical vapor deposited (PECVD) silicon nitride antireflection coating. These processes were carried out in a high-throughput lamp-heated conveyor belt furnace. PECVD silicon nitride-induced hydrogenation of defects in EFG silicon was studied in conjunction with screen-printed aluminum back surface field formation to investigate the synergistic effect of aluminum gettering and silicon nitride hydrogenation of bulk defects. It was found that post-deposition anneal of PECVD silicon nitride at temperatures ranging from 450 to 850 °C, without the coformation of aluminum back surface field on the back, does not provide appreciable passivation or hydrogenation of bulk defects in EFG material. However, simultaneous anneal of PECVD silicon nitride and formation of aluminum back surface field at 850 °C significantly enhanced the hydrogenation ability of the PECVD silicon nitride film. PECVD silicon nitride deposition and a subsequent anneal, after the aluminum back surface field formation, was found to be less effective in passivating bulk defects. It is proposed that aluminum-enhanced hydrogenation from a PECVD silicon nitride film is the result of vacancy generation at the aluminum-silicon interface due to the alloying process. The affinity of hydrogen to react with vacancies provides a chemical potential gradient that increases the flux of atomic hydrogen from the silicon nitride film into the bulk silicon. In addition, vacancies can dissociate hydrogen molecules, increasing the atomic hydrogen content of the bulk silicon. This enhances defect passivation and improves the minority carrier lifetime.

  17. Tumor Biomarker Glycoproteins in the Seminal Plasma of Healthy Human Males Are Endogenous Ligands for DC-SIGN*

    PubMed Central

    Clark, Gary F.; Grassi, Paola; Pang, Poh-Choo; Panico, Maria; Lafrenz, David; Drobnis, Erma Z.; Baldwin, Michael R.; Morris, Howard R.; Haslam, Stuart M.; Schedin-Weiss, Sophia; Sun, Wei; Dell, Anne

    2012-01-01

    DC-SIGN is an immune C-type lectin that is expressed on both immature and mature dendritic cells associated with peripheral and lymphoid tissues in humans. It is a pattern recognition receptor that binds to several pathogens including HIV-1, Ebola virus, Mycobacterium tuberculosis, Candida albicans, Helicobacter pylori, and Schistosoma mansoni. Evidence is now mounting that DC-SIGN also recognizes endogenous glycoproteins, and that such interactions play a major role in maintaining immune homeostasis in humans and mice. Autoantigens (neoantigens) are produced for the first time in the human testes and other organs of the male urogenital tract under androgenic stimulus during puberty. Such antigens trigger autoimmune orchitis if the immune response is not tightly regulated within this system. Endogenous ligands for DC-SIGN could play a role in modulating such responses. Human seminal plasma glycoproteins express a high level of terminal Lewisx and Lewisy carbohydrate antigens. These epitopes react specifically with the lectin domains of DC-SIGN. However, because the expression of these sequences is necessary but not sufficient for interaction with DC-SIGN, this study was undertaken to determine if any seminal plasma glycoproteins are also endogenous ligands for DC-SIGN. Glycoproteins bearing terminal Lewisx and Lewisy sequences were initially isolated by lectin affinity chromatography. Protein sequencing established that three tumor biomarker glycoproteins (clusterin, galectin-3 binding glycoprotein, prostatic acid phosphatase) and protein C inhibitor were purified by using this affinity method. The binding of DC-SIGN to these seminal plasma glycoproteins was demonstrated in both Western blot and immunoprecipitation studies. These findings have confirmed that human seminal plasma contains endogenous glycoprotein ligands for DC-SIGN that could play a role in maintaining immune homeostasis both in the male urogenital tract and the vagina after coitus. PMID:21986992

  18. Coal pyrolysis to acetylene using dc hydrogen plasma torch: effects of system variables on acetylene concentration

    NASA Astrophysics Data System (ADS)

    Chen, Longwei; Meng, Yuedong; Shen, Jie; Shu, Xingsheng; Fang, Shidong; Xiong, Xinyang

    2009-03-01

    In order to unveil the inner mechanisms that determine acetylene concentration, experimental studies on the effect of several parameters such as plasma torch power, hydrogen flux and coal flux were carried out from coal pyrolysis in a dc plasma torch. Xinjiang long flame coals including volatile constituents at a level of about 42% were used in the experiment. Under the following experimental conditions, namely plasma torch power, hydrogen flow rate and pulverized coal feed speed of 2.12 MW, 32 kg h-1 and 900 kg h-1, respectively, acetylene volume concentration of about 9.4% was achieved. The experimental results indicate that parameters such as plasma torch power and coal flux play important roles in the formation of acetylene. Acetylene concentration increases inconspicuously with hydrogen flux. A chemical thermodynamic equilibrium model using the free energy method is introduced in this paper to numerically simulate each experimental condition. The numerical results are qualitatively consistent with the experimental results. Two parameters, i.e. the gas temperature and the ratio of hydrogen/carbon, are considered to be the dominant and independent factors that determine acetylene concentration.

  19. Plasma kinetic processes in a strong d.c. magnetic field

    NASA Technical Reports Server (NTRS)

    Montgomery, D.

    1976-01-01

    Recent results in the kinetic theory of a strongly magnetized plasma are surveyed. Emphasis is on the electrostatic guiding-center plasma in two dimensions, in both the fluid and 'charged rod' descriptions. The basic kinetic description of the plasma is in terms of the statistically-distributed Fourier coefficients associated with the velocity and 'enstrophy' (charge density) fields. It is a universal tendency in such media for enstrophy to flow to shorter wavelengths but for energy to flow to longer wavelengths. A consequence of the energy flow to longer wavelengths is the generation of long-range order in the form of macroscopic vortices. These kinds of structure have been called 'convection cells' and can be extraordinarily efficient in transporting particles transverse to a magnetic field. The tendency to vortex formation can be disrupted by collisions between particles. Modifications of the Fokker-Planck equation for a plasma produced by a strong dc magnetic field are considered in both two and three dimensions.

  20. Plasma parameters of pulsed-dc discharges in methane used to deposit diamondlike carbon films

    SciTech Connect

    Corbella, C.; Rubio-Roy, M.; Bertran, E.; Andujar, J. L.

    2009-08-01

    Here we approximate the plasma kinetics responsible for diamondlike carbon (DLC) depositions that result from pulsed-dc discharges. The DLC films were deposited at room temperature by plasma-enhanced chemical vapor deposition (PECVD) in a methane (CH{sub 4}) atmosphere at 10 Pa. We compared the plasma characteristics of asymmetric bipolar pulsed-dc discharges at 100 kHz to those produced by a radio frequency (rf) source. The electrical discharges were monitored by a computer-controlled Langmuir probe operating in time-resolved mode. The acquisition system provided the intensity-voltage (I-V) characteristics with a time resolution of 1 mus. This facilitated the discussion of the variation in plasma parameters within a pulse cycle as a function of the pulse waveform and the peak voltage. The electron distribution was clearly divided into high- and low-energy Maxwellian populations of electrons (a bi-Maxwellian population) at the beginning of the negative voltage region of the pulse. We ascribe this to intense stochastic heating due to the rapid advancing of the sheath edge. The hot population had an electron temperature T{sub e}{sup hot} of over 10 eV and an initial low density n{sub e}{sup hot} which decreased to zero. Cold electrons of temperature T{sub e}{sup cold}approx1 eV represented the majority of each discharge. The density of cold electrons n{sub e}{sup cold} showed a monotonic increase over time within the negative pulse, peaking at almost 7x10{sup 10} cm{sup -3}, corresponding to the cooling of the hot electrons. The plasma potential V{sub p} of approx30 V underwent a smooth increase during the pulse and fell at the end of the negative region. Different rates of CH{sub 4} conversion were calculated from the DLC deposition rate. These were explained in terms of the specific activation energy E{sub a} and the conversion factor x{sub dep} associated with the plasma processes. The work deepens our understanding of the advantages of using pulsed power supplies

  1. Redeposition in plasma-assisted atomic layer deposition: Silicon nitride film quality ruled by the gas residence time

    NASA Astrophysics Data System (ADS)

    Knoops, Harm C. M.; de Peuter, K.; Kessels, W. M. M.

    2015-07-01

    The requirements on the material properties and growth control of silicon nitride (SiNx) spacer films in transistors are becoming ever more stringent as scaling of transistor structures continues. One method to deposit high-quality films with excellent control is atomic layer deposition (ALD). However, depositing SiNx by ALD has turned out to be very challenging. In this work, it is shown that the plasma gas residence time τ is a key parameter for the deposition of SiNx by plasma-assisted ALD and that this parameter can be linked to a so-called "redeposition effect". This previously ignored effect, which takes place during the plasma step, is the dissociation of reaction products in the plasma and the subsequent redeposition of reaction-product fragments on the surface. For SiNx ALD using SiH2(NHtBu)2 as precursor and N2 plasma as reactant, the gas residence time τ was found to determine both SiNx film quality and the resulting growth per cycle. It is shown that redeposition can be minimized by using a short residence time resulting in high-quality films with a high wet-etch resistance (i.e., a wet-etch rate of 0.5 nm/min in buffered HF solution). Due to the fundamental nature of the redeposition effect, it is expected to play a role in many more plasma-assisted ALD processes.

  2. Effect of process parameters on the mechanical properties of carbon nitride thin films synthesized by plasma assisted pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Tabbal, M.; Mérel, P.; Chaker, M.

    We present an investigation of the effect of the process parameters, namely deposition pressure and laser intensity, on the growth and mechanical properties of carbon nitride (CNx) thin films synthesized by plasma assisted pulsed laser deposition. Deposition at high remote plasma pressure (200 mTorr) enhances both growth rate and nitrogen incorporation (up to 40 at.%), but nano-indentation measurements indicate that these films are very soft and have poor mechanical properties. At low remote plasma pressure (0.5 mTorr), the nitrogen content varies from 24 to 16 at.% with increasing laser intensity as the films become much harder and more elastic, with hardness and Young's modulus values reaching 24 GPa and 230 GPa, respectively. These effects are explained in terms of a thermalization of the laser plasma at 200 mTorr and indicate that plasma activation of nitrogen does not provide any particular benefit to the film properties when deposition is performed at high pressure. However, at low pressure, the benefit of plasma activation is evidenced through enhanced nitrogen incorporation in the films while preserving the highly energetic species in the ablation plume. Such conditions lead to the synthesis, at room temperature, of hard and elastic films having properties close to those of fullerene-like CNx.

  3. Ion-plasma nitriding as a method of instruments and parts durability

    NASA Astrophysics Data System (ADS)

    Samigullin, A. D.; Galiakbarov, A. T.; Galiakbarov, R. T.; Samigullina, A. R.

    2017-01-01

    Improvement of the machines, parts, devices reliability as well as improvement of their quality and operation are topics of interest at the present time. Solution to these problems is related to hardening of the product surface layers in the first place. This article deals with parameters of nitriding process using the example of 38XM steel which is applied in essential parts of turbine installations and compressors operating at temperatures up to 400°C. The article also provides the results of nitriding at different modes.

  4. Tribological evaluation of diamond coating on pure titanium in comparison with plasma nitrided titanium and uncoated titanium

    SciTech Connect

    Yan, B.; Loh, N.L.; Fu, Y.; Sun, C.Q.; Hing, P.

    1999-12-01

    Titanium alloys are characterized by poor tribological properties, and the traditional use of titanium alloys has been restricted to nontribological applications. The deposition of a well adherent diamond coating is a promising way to solve this problem. In this study, the tribological properties of diamond-coated titanium were studied using a pin-on-disk tribometer, and the results were compared with those of pure titanium and plasma nitrided titanium. The tribological behavior of pure titanium was characterized by high coefficient of friction and rapid wear of materials. Plasma nitriding improved the wear resistance only under low normal load; however, this hardened layer was not efficient in improving the wear resistance and the friction properties under high normal load. Diamond coating on pure titanium improved the wear resistance of titanium significantly. Surface profilometry measurement indicated that little or no wear of the diamond coating occurred under the test conditions loads. The roughness of the diamond coating was critical because it controlled the amount of abrasive damage on the counterface. Reducing the surface roughness by polishing led to the reductions in both the friction and wear of the counterface.

  5. Synthesis of aluminum nitride powders from a plasma-assisted ball milled precursor through carbothermal reaction

    SciTech Connect

    Liu, Zhi-jie; Dai, Le-yang; Yang, De-zheng; Wang, Sen; Zhang, Bao-jian; Wang, Wen-chun; Cheng, Tie-han

    2015-01-15

    Highlights: • A novel and high efficiency synthesizing AlN powders method combining mechanical ball milling and DBDP has been developed. • The particle size, the crystallite size, the lattice distortion, the morphology of Al{sub 2}O{sub 3} powders, and the AlN conversion rate are investigated and compared under the ball milled Al{sub 2}O{sub 3} powders with DBDP and without DBDP. • The ball milled Al{sub 2}O{sub 3} powders with DBDP have small spherical structure morphology with very fine particles size and high specific surface area, which result in a higher chemical efficiency and a higher AlN conversion rate at lower thermal temperature. - Abstract: In this paper, aluminum nitride (AlN) powers have been produced with a novel and high efficiency method by thermal annealing at 1100–1600 °C of alumina (Al{sub 2}O{sub 3}) powders which were previously ball milled for various time up to 40 h with and without the assistant of dielectric barrier discharge plasma (DBDP). The ball milled Al{sub 2}O{sub 3} powders with DBDP and without DBDP and the corresponding synthesized AlN powers are characterized by X-ray diffraction, scanning electron microscope, and transmission electron microscopy. From the characteristics of the ball milled Al{sub 2}O{sub 3} powders with DBDP and without DBDP, it can be seen that the ball milled Al{sub 2}O{sub 3} powders with DBDP have small spherical structure morphology with very fine particles size and high specific surface area, which result in a higher chemical efficiency and a higher AlN conversion rate at lower thermal temperature. Meanwhile, the synthesized AlN powders can be known as hexagonal AlN with fine crystal morphology and irregular lump-like structure, and have uniform distribution with the average particle size of about between 500 nm and 1000 nm. This provides an important method for fabricating ultra fine powders and synthesizing nitrogen compounds.

  6. Characterization of Damage of Al2O3/Ge Gate Stack Structure Induced with Light Radiation during Plasma Nitridation

    NASA Astrophysics Data System (ADS)

    Kusumandari; Takeuchi, Wakana; Kato, Kimihiko; Shibayama, Shigehisa; Sakashita, Mitsuo; Nakatsuka, Osamu; Zaima, Shigeaki

    2012-01-01

    We have investigated the effects of light radiation during plasma nitridation on the electrical properties of an Al2O3/Ge gate stack structure using the pallet for plasma evaluation (PAPE) technique. From the capacitance-voltage characteristics, the flatband voltage shift due to fixed oxide charges significantly increases after light exposure with an energy higher than 7.5 eV. In addition, the density of trapped charges near the interface and the interface state density (Dit) also significantly increase after light exposure with an energy over 11.3 eV. The net density of positive fixed oxide charges, the density of trapped charges near the interface, and Dit can be reduced by post-metallization annealing (PMA) in N2 ambient at 300 °C.

  7. High quality epitaxial CoSi{sub 2} using plasma nitridation-mediated epitaxy: The effects of the capping layer

    SciTech Connect

    Lee, Han-Bo-Ram; Gu, Gil Ho; Son, J. Y.; Park, C. G.; Kim, Hyungjun

    2007-11-01

    The epitaxial growth of CoSi{sub 2} from Co with a Ti capping layer using plasma nitridation-mediated epitaxy (PNME) was demonstrated. By exposing the Si substrate to the NH{sub 3} plasma, an a-SiN{sub x} layer was formed with atomic scale thickness controllability. After Co and Ti deposition followed by annealing, high quality epitaxial CoSi{sub 2} was formed on Si(001) with a perfectly flat interface. However, the epitaxial growth was observed for Co with a Ti capping layer prepared only by ex situ deposition, not by in situ deposition. The epitaxial CoSi{sub 2} was analyzed by x-ray diffraction and a scanning transmission electron microscope. Based on these results, the mechanism of PNME and the effects of the Ti capping layer process on silicidation were discussed.

  8. Excitation wavelength dependence of water-window line emissions from boron-nitride laser-produced plasmas

    SciTech Connect

    Crank, M.; Harilal, S. S.; Hassan, S. M.; Hassanein, A.

    2012-02-01

    We investigated the effects of laser excitation wavelength on water-window emission lines of laser-produced boron-nitride plasmas. Plasmas are produced by focusing 1064 nm and harmonically generated 532 and 266 nm radiation from a Nd:YAG laser on BN target in vacuum. Soft x-ray emission lines in the water-window region are recorded using a grazing-incidence spectrograph. Filtered photodiodes are used to obtain complementary data for water-window emission intensity and angular dependence. Spectral emission intensity changes in nitrogen Ly-{alpha} and He-{alpha} are used to show how laser wavelength affects emission. Our results show that the relative intensity of spectral lines is laser wavelength dependent, with the ratio of Ly-{alpha} to He-{alpha} emission intensity decreasing as laser wavelength is shortened. Filtered photodiode measurements of angular dependence showed that 266 and 532 nm laser wavelengths produce uniform emission.

  9. Influence of a transverse magnetic field on arc root movements in a dc plasma torch: Diamagnetic effect of arc column

    SciTech Connect

    Kim, Keun Su

    2009-03-23

    The effect of a transverse magnetic field on the anodic arc root movement inside a dc plasma torch has been investigated. The arc voltage fluctuation, which represents the degree of the arc instability, was reduced to 28.6% of the original value and the high frequency components in the voltage signal also decreased in their magnitudes. The inherent arc instability in a dc thermal plasma torch seems to be suppressed by a diamagnetic effect of the arc column. Furthermore, the measured voltage wave forms indicated that the arc root attachment mode would be controllable by a transverse magnetic field.

  10. Geopolymers prepared from DC plasma treated air pollution control (APC) residues glass: properties and characterisation of the binder phase.

    PubMed

    Kourti, Ioanna; Devaraj, Amutha Rani; Bustos, Ana Guerrero; Deegan, David; Boccaccini, Aldo R; Cheeseman, Christopher R

    2011-11-30

    Air pollution control (APC) residues have been blended with glass-forming additives and treated using DC plasma technology to produce a high calcium aluminosilicate glass (APC glass). This has been used to form geopolymer-glass composites that exhibit high strength and density, low porosity, low water absorption, low leaching and high acid resistance. The composites have a microstructure consisting of un-reacted residual APC glass particles imbedded in a complex geopolymer and C-S-H gel binder phase, and behave as particle reinforced composites. The work demonstrates that materials prepared from DC plasma treated APC residues have potential to be used to form high quality pre-cast products.

  11. Effect of plasma parameters on characteristics of silicon nitride film deposited by single and dual frequency plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Sahu, B. B.; Yin, Yongyi; Han, Jeon G.

    2016-03-01

    This work investigates the deposition of hydrogenated amorphous silicon nitride films using various low-temperature plasmas. Utilizing radio-frequency (RF, 13.56 MHz) and ultra-high frequency (UHF, 320 MHz) powers, different plasma enhanced chemical vapor deposition processes are conducted in the mixture of reactive N2/NH3/SiH4 gases. The processes are extensively characterized using different plasma diagnostic tools to study their plasma and radical generation capabilities. A typical transition of the electron energy distribution function from single- to bi-Maxwellian type is achieved by combining RF and ultra-high powers. Data analysis revealed that the RF/UHF dual frequency power enhances the plasma surface heating and produces hot electron population with relatively low electron temperature and high plasma density. Using various film analysis methods, we have investigated the role of plasma parameters on the compositional, structural, and optical properties of the deposited films to optimize the process conditions. The presented results show that the dual frequency power is effective for enhancing dissociation and ionization of neutrals, which in turn helps in enabling high deposition rate and improving film properties.

  12. Effect of plasma parameters on characteristics of silicon nitride film deposited by single and dual frequency plasma enhanced chemical vapor deposition

    SciTech Connect

    Sahu, B. B. E-mail: hanjg@skku.edu; Yin, Yongyi; Han, Jeon G. E-mail: hanjg@skku.edu

    2016-03-15

    This work investigates the deposition of hydrogenated amorphous silicon nitride films using various low-temperature plasmas. Utilizing radio-frequency (RF, 13.56 MHz) and ultra-high frequency (UHF, 320 MHz) powers, different plasma enhanced chemical vapor deposition processes are conducted in the mixture of reactive N{sub 2}/NH{sub 3}/SiH{sub 4} gases. The processes are extensively characterized using different plasma diagnostic tools to study their plasma and radical generation capabilities. A typical transition of the electron energy distribution function from single- to bi-Maxwellian type is achieved by combining RF and ultra-high powers. Data analysis revealed that the RF/UHF dual frequency power enhances the plasma surface heating and produces hot electron population with relatively low electron temperature and high plasma density. Using various film analysis methods, we have investigated the role of plasma parameters on the compositional, structural, and optical properties of the deposited films to optimize the process conditions. The presented results show that the dual frequency power is effective for enhancing dissociation and ionization of neutrals, which in turn helps in enabling high deposition rate and improving film properties.

  13. A study of the transient plasma potential in a pulsed bi-polar dc magnetron discharge

    NASA Astrophysics Data System (ADS)

    Bradley, J. W.; Karkari, S. K.; Vetushka, A.

    2004-05-01

    The temporal evolution of the plasma potential, Vp, in a pulsed dc magnetron plasma has been determined using the emissive probe technique. The discharge was operated in the 'asymmetric bi-polar' mode, in which the discharge voltage changes polarity during part of the pulse cycle. The probe measurements, with a time-resolution of 20 ns or better, were made along a line above the racetrack, normal to the plane of the cathode target, for a fixed frequency (100 kHz), duty cycle (50%), argon pressure (0.74 Pa) and discharge power (583 W). At all the measured positions, Vp was found to respond to the large and rapid changes in the cathode voltage, Vd, during the different phases of the pulse cycle, with Vp always more positive than Vd. At a typical substrate position (>80 mm from the target), Vp remains a few volts above the most positive surface in the discharge at all times. In the 'on' phase of the pulse, the measurements show a significant axial electric field is generated in the plasma, with the plasma potential dropping by a total of about 30 V over a distance of 70 mm, from the bulk plasma to a position close to the beginning of the cathode fall. This is consistent with measurements made in the dc magnetron. During the stable 'reverse' phase of the discharge, for distances greater than 18 mm from the target, the axial electric field is found to collapse, with Vp elevated uniformly to about 3 V above Vd. Between the target and this field-free region an ion sheath forms, and the current flowing to the target is still an ion current in this 'reverse' period. During the initial 200 ns of the voltage 'overshoot' phase (between 'on' and 'reverse' phases), Vd reached a potential of +290 V; however, close to the target, Vp was found to attain a much higher value, namely +378 V. Along the line of measurement, the axial electric field reverses in direction in this phase, and an electron current of up to 9 A flows to the target. The spatial and temporal measurements of Vp

  14. Effects of edge dc biasing on plasma rotation and transport in a toroidal geometry

    NASA Astrophysics Data System (ADS)

    Fredriksen, Åshild; Riccardi, Claudia; Magni, Simone

    2006-02-01

    We report results from experiments performed to study how a change in boundary conditions affects the plasma state in the toroidal geometry of the Blaamann device in Tromso. The boundary condition was changed by applying a dc bias on a limiter extended around the entire poloidal circumference of the plasma column. Two distinctly different plasma potential states were found. One state was associated with a bias at or negative with respect to the floating potential of the limiter, and a small ion-saturation current. The other state was associated with a positive bias with respect to the floating potential, near or in the electron saturation regime of the limiter. In the latter case the potential minimum in the middle of the cross-section was significantly less negative than in the case of ion-saturation current to the limiter. On the other hand, the grounded limiter provided the best confinement properties, for which the density maximum was significantly higher than for both more positive and more negative biases. This state also had the lowest fluctuation levels, and near zero poloidal velocities close to the boundaries, as well as the smallest radial, anomalous particle transport.

  15. Effects of Edge DC Biasing on Plasma Rotation and Transport in a Toroidal Geometry.

    NASA Astrophysics Data System (ADS)

    Fredriksen, Ashild; Riccardi, Claudia

    2005-10-01

    We report results from experiments performed to study how a change in boundary conditions is affecting the plasma states in the toroidal geometry of the Blaamann device in Tromso. The boundary condition was changed by applying a DC bias on a limiter extended around the entire poloidal circumference of the plasma column. Two distinctly different plasma potential states were found. One state was associated with a bias at or negative with respect to the floating potential of the limiter, and a small ion saturation current. The other state was associated with a positive bias with respect to the floating potential, near or in the electron saturation regime of the limiter. In the latter case the potential minimum in the middle of the cross-section was significantly less negative than in the case of ion-saturation current to the limiter. On the other hand, the grounded limiter provided the best confinement properties, for which the density maximum was significantly higher than for both more positive and more negative biases. This state also had the lowest fluctuation levels, and near zero poloidal velocities close to the boundaries, as well as the smallest radial, anomalous particle transport.

  16. Effect of hexafluoropropylene oxide plasma polymer particle coatings on the rheological properties of boron nitride/poly(dimethylsiloxane) composites.

    PubMed

    Bian, J F; Lujan, W R; Harper-Nixon, D; Jeon, H S; Weinkauf, D H

    2005-10-15

    This work explores the use of conformal nanoscale plasma coatings on the surface of boron nitride (BN) powders to control the rheological properties of BN/poly(dimethylsiloxane) (PDMS) composites. BN particles are conformally coated with hexafluoropropylene oxide (HFPO) in a tumbling RF-plasma reactor. Following the HFPO plasma treatment, XPS evidence indicates the presence of thin coating on the surface of the particles having a F:C ratio of 1.77. Filled BN/PDMS composites are investigated using oscillatory shear rheometry in the concentration range of 0.09-0.41 vol% (varphi). The addition of the plasma treated BN particles to the PDMS matrix reduces the complex viscosity by 40-60% when compared with equally loaded control samples across a broad concentration range. The frequency dependence of the maximum packing fraction (varphi(m)=0.38-0.42) is also observed for both treated and untreated particles. The maximum packing fraction does not appear to be significantly affected by the conformal plasma polymer treatment. The investigation has shown that the relative dynamic viscosity of the BN/PDMS can be described by the modified Mooney equation.

  17. A study on III-nitride recessed-gate field-effect transistors using a remote-oxygen-plasma treatment

    NASA Astrophysics Data System (ADS)

    Lee, Y.-C.; Kao, T.-T.; Shen, S.-C.

    2015-04-01

    We report a comparative study of the device performance of III-nitride (III-N) heterojunction field-effect transistors (HFETs) and metal-insulator-semiconductor field-effect transistors (MISFETs). The influence of a remote-oxygen-plasma treatment was investigated. The plasma-treated recessed-gate HFETs and MISFETs show normally-off characteristics with higher peak transconductance, lower sub-threshold slope, smaller hysteresis. An on-off ratio greater than 2.2E11 with a significant suppression of gate leakage can be achieved in plasma-treated III-N MISFETs. A drain current transient measurement was performed to analyze the traps in these devices and possible origins of these traps are studied. Six traps with characteristic time constants (τ) ranging from 180 s to 3 ms are identified in both HFETs and MISFETs, in addition to a trap which is associated with the ALD-grown gate dielectrics for the MISFETs. The results suggest that improved device performance in these plasma-treated III-N FETs is attributed to the reduced trap states with τ < 400 ms, which are located on III-N surfaces. The slower traps (τ > 2 s) cannot be reduced by the plasma treatment and are related to the oxygen and carbon impurities and the buffer traps in the bulk semiconductors.

  18. Characterization of undoped and Co doped ZnO nanoparticles synthesized by DC thermal plasma method

    NASA Astrophysics Data System (ADS)

    Nirmala, M.; Anukaliani, A.

    2011-02-01

    ZnO nanopowders doped with 5 and 10 at% cobalt were synthesized and their antibacterial activity was studied. Cobalt doped ZnO powders were prepared using dc thermal plasma method. Crystal structure and grain size of the particles were characterized by X-ray diffractometry and optical properties were studied using UV-vis spectroscopy. The particle size and morphology was observed by SEM and HRTEM, revealing rod like morphology. The antibacterial activity of undoped ZnO and cobalt doped ZnO nanoparticles against a Gram-negative bacterium Escherichia coli and a Gram-positive bacterium Bacillus atrophaeus was investigated. Undoped ZnO and cobalt doped ZnO exhibited antibacterial activity against both E. coli and Staphylococcus aureus but it was considerably more effective in the cobalt doped ZnO.

  19. Dusty plasma microparticle cloud control and rapid electrostatic mutual-repulsion expansion in a DC glow discharge

    NASA Astrophysics Data System (ADS)

    Gillman, Eric; Amatucci, Bill

    2016-10-01

    Microparticles in plasma discharges rapidly charge up, typically collecting a net negative charge due to the relatively high mobility of electrons compared to ions. Electrostatic forces can be utilized to control charged microparticle behavior and motion in a plasma discharge. In these experiments a metal wire loop is supplied with an electric potential that can be controlled independently from the DC plasma glow discharge electrodes. By varying the voltage on the wire loop, we can attract, trap, manipulate, suspend, and/or repel microparticles that originate from the DC glow discharge. Experiments studied the properties of electrostatic self-repulsion of a cloud of charged microparticles. By pulsing the plasma and controlling wire loop potential, a cloud of trapped microparticles is released and allowed to rapidly expand. A simple force balance simulation code is used as a model to compare and benchmark actual experimental results. This work was supported by the Naval Research Laboratory base program.

  20. Evolution of an electron energy distribution function in a weak dc magnetic field in solenoidal inductive plasma

    SciTech Connect

    Lee, Min-Hyong; Choi, Seong Wook

    2008-12-01

    We investigated the evolution of the electron energy distribution function (EEDF) in a solenoidal inductively coupled plasma surrounded by an axial dc magnetic field. The increase in the dc magnetic field caused the EEDF to evolve from a bi-Maxwellian to a Maxwellian distribution. At the discharge center, the number of low energy electrons was significantly reduced while the high energy electron population showed little change when a weak dc magnetic field was present. However, at the discharge radial boundary, the high energy electron population decreased significantly with the magnetic field while the change in low energy population was not prominent compared to the discharge boundary. These changes in EEDFs at the boundary and center of the discharge are due to the radial confinement and the restriction of radial transport of electrons by dc magnetic field.

  1. Temporally and spatially resolved plasma spectroscopy in pulsed laser deposition of ultra-thin boron nitride films

    NASA Astrophysics Data System (ADS)

    Glavin, Nicholas R.; Muratore, Christopher; Jespersen, Michael L.; Hu, Jianjun; Fisher, Timothy S.; Voevodin, Andrey A.

    2015-04-01

    Physical vapor deposition (PVD) has recently been investigated as a viable, alternative growth technique for two-dimensional materials with multiple benefits over other vapor deposition synthesis methods. The high kinetic energies and chemical reactivities of the condensing species formed from PVD processes can facilitate growth over large areas and at reduced substrate temperatures. In this study, chemistry, kinetic energies, time of flight data, and spatial distributions within a PVD plasma plume ablated from a boron nitride (BN) target by a KrF laser at different pressures of nitrogen gas were investigated. Time resolved spectroscopy and wavelength specific imaging were used to identify and track atomic neutral and ionized species including B+, B*, N+, N*, and molecular species including N2*, N2+, and BN. Formation and decay of these species formed both from ablation of the target and from interactions with the background gas were investigated and provided insights into fundamental growth mechanisms of continuous, amorphous boron nitride thin films. The correlation of the plasma diagnostic results with film chemical composition and thickness uniformity studies helped to identify that a predominant mechanism for BN film formation is condensation surface recombination of boron ions and neutral atomic nitrogen species. These species arrive nearly simultaneously to the substrate location, and BN formation occurs microseconds before arrival of majority of N+ ions generated by plume collisions with background molecular nitrogen. The energetic nature and extended dwelling time of incident N+ ions at the substrate location was found to negatively impact resulting BN film stoichiometry and thickness. Growth of stoichiometric films was optimized at enriched concentrations of ionized boron and neutral atomic nitrogen in plasma near the condensation surface, providing few nanometer thick films with 1:1 BN stoichiometry and good thicknesses uniformity over macroscopic areas.

  2. Temporally and spatially resolved plasma spectroscopy in pulsed laser deposition of ultra-thin boron nitride films

    SciTech Connect

    Glavin, Nicholas R. E-mail: andrey.voevodin@us.af.mil; Muratore, Christopher; Jespersen, Michael L.; Hu, Jianjun; Fisher, Timothy S.; Voevodin, Andrey A. E-mail: andrey.voevodin@us.af.mil

    2015-04-28

    Physical vapor deposition (PVD) has recently been investigated as a viable, alternative growth technique for two-dimensional materials with multiple benefits over other vapor deposition synthesis methods. The high kinetic energies and chemical reactivities of the condensing species formed from PVD processes can facilitate growth over large areas and at reduced substrate temperatures. In this study, chemistry, kinetic energies, time of flight data, and spatial distributions within a PVD plasma plume ablated from a boron nitride (BN) target by a KrF laser at different pressures of nitrogen gas were investigated. Time resolved spectroscopy and wavelength specific imaging were used to identify and track atomic neutral and ionized species including B{sup +}, B*, N{sup +}, N*, and molecular species including N{sub 2}*, N{sub 2}{sup +}, and BN. Formation and decay of these species formed both from ablation of the target and from interactions with the background gas were investigated and provided insights into fundamental growth mechanisms of continuous, amorphous boron nitride thin films. The correlation of the plasma diagnostic results with film chemical composition and thickness uniformity studies helped to identify that a predominant mechanism for BN film formation is condensation surface recombination of boron ions and neutral atomic nitrogen species. These species arrive nearly simultaneously to the substrate location, and BN formation occurs microseconds before arrival of majority of N{sup +} ions generated by plume collisions with background molecular nitrogen. The energetic nature and extended dwelling time of incident N{sup +} ions at the substrate location was found to negatively impact resulting BN film stoichiometry and thickness. Growth of stoichiometric films was optimized at enriched concentrations of ionized boron and neutral atomic nitrogen in plasma near the condensation surface, providing few nanometer thick films with 1:1 BN stoichiometry and good

  3. Impact of temperature increments on tunneling barrier height and effective electron mass for plasma nitrided thin SiO{sub 2} layer on a large wafer area

    SciTech Connect

    Aygun, G.; Roeder, G.; Erlbacher, T.; Wolf, M.; Schellenberger, M.; Pfitzner, L.

    2010-10-15

    Thermally grown SiO{sub 2} layers were treated by a plasma nitridation process realized in a vertical furnace. The combination of a pulsed-low frequency plasma and a microwave remote plasma with N{sub 2}/NH{sub 3}/He feed gas mixture was used to nitride the thermally grown SiO{sub 2} gate dielectrics of MIS structures. Temperature dependency of effective masses and the barrier heights for electrons in pure thermally grown SiO{sub 2} as well as plasma nitrided SiO{sub 2} in high electric field by means of Fowler-Nordheim regime was determined. It is frequently seen from the literature that either effective electron mass or barrier height (generally effective electron mass) is assumed to be a constant and, as a result, the second parameter is calculated under the chosen assumption. However, in contrast to general attitude of previous studies, this work does not make any such assumptions for the calculation of neither of these two important parameters of an oxide at temperature ranges from 23 to 110 deg. C for SiO{sub 2}, and 23 to 130 deg. C for nitrided oxide. It is also shown here that both parameters are affected from the temperature changes; respectively, the barrier height decreases while the effective mass increases as a result of elevated temperature in both pure SiO{sub 2} and plasma nitrided SiO{sub 2}. Therefore, one parameter could be miscalculated if the other parameter, i.e., effective mass of electron, was assumed to be a constant with respect to variable physical conditions like changing temperature. Additionally, the barrier heights were calculated just by taking constant effective masses for both types of oxides to be able to compare our results to common literature values.

  4. Tribological behaviors of diamond-like carbon coatings on plasma nitrided steel using three BN-containing lubricants

    NASA Astrophysics Data System (ADS)

    Jia, Zheng-feng; Wang, Peng; Xia, Yan-qiu; Zhang, Hao-bo; Pang, Xian-juan; Li, Bin

    2009-04-01

    In this work, diamond-like carbon (DLC) coatings were deposited on plasma nitrided AISI 1045 steel by magnetron sputtering. Three BN-containing additives and molybdenum dithiocarbamate (MoDTC) were added to poly-alpha-olefin (PAO) as additives. The additive content (mass fraction) in PAO was fixed at 0.5 wt%. The friction and wear characters of DLC coatings on nitrided steel discs sliding against AISI 52100 steel balls were tested under the lubricated conditions. It was found that borate esters have a higher load carrying capacity and much better anti-wear and friction-reducing ability than that of MoDTC. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were employed to explore the properties of the worn surface and the mechanism of friction and wear. According to the XPS analysis, the adsorbed organic N-containing compounds and BN are, possibly, the primary reason for the novel borate esters to possess a relatively constant coefficient of friction and lower wear rate. On the other hand, possibly, the MoDTC molecules break down during sliding and produce many Mo-oxides, and then the Mo-oxides destroy the DLC coating because of its sharp edge crystalline solid structure. After destroying the DLC coating, the MoDTC react with metals and form MoS 2 tribofilm, and decrease coefficient of friction of rubbing pairs.

  5. Magnetic properties of single crystalline expanded austenite obtained by plasma nitriding of austenitic stainless steel single crystals.

    PubMed

    Menéndez, Enric; Templier, Claude; Garcia-Ramirez, Pablo; Santiso, José; Vantomme, André; Temst, Kristiaan; Nogués, Josep

    2013-10-23

    Ferromagnetic single crystalline [100], [110], and [111]-oriented expanded austenite is obtained by plasma nitriding of paramagnetic 316L austenitic stainless steel single crystals at either 300 or 400 °C. After nitriding at 400 °C, the [100] direction appears to constitute the magnetic easy axis due to the interplay between a large lattice expansion and the expected decomposition of the expanded austenite, which results in Fe- and Ni-enriched areas. However, a complex combination of uniaxial (i.e., twofold) and biaxial (i.e., fourfold) in-plane magnetic anisotropies is encountered. It is suggested that the former is related to residual stress-induced effects while the latter is associated to the in-plane projections of the cubic lattice symmetry. Increasing the processing temperature strengthens the biaxial in-plane anisotropy in detriment of the uniaxial contribution, in agreement with a more homogeneous structure of expanded austenite with lower residual stresses. In contrast to polycrystalline expanded austenite, single crystalline expanded austenite exhibits its magnetic easy axes along basic directions.

  6. Plasma-deposited germanium nitride gate insulators for indium phosphide metal-insulator-semiconductor field-effect transistors

    NASA Technical Reports Server (NTRS)

    Johnson, Gregory A.; Kapoor, Vik J.

    1991-01-01

    Plasma-deposited germanium nitride was investigated for the first time as a possible gate insulator for InP compound semiconductor metal-insulator-semiconductor FET (MISFET) technology. The germanium nitride films were successfully deposited in a capacitively coupled parallel plate reactor at 13.56 MHz operation using GeH4/N2/NH3 and GeH4/N2 mixtures as reactant gases. The former process produced better quality films with enhanced uniformity, increased deposition rates, and increased resistivity. The breakdown field strength of the films was greater than 10 to the 6th V/cm. Auger electron spectroscopy did not indicate significant chemical composition differences between the two processes. For MISFETs with 2-micron channel lengths fabricated on InP, the device transconductance and threshold voltage for the GeH4/N2/NH3 process were 17 mS/mm and -3.6 V, respectively. The drain-source breakdown voltages were greater than 10 V.

  7. Plasma-deposited germanium nitride gate insulators for indium phosphide metal-insulator-semiconductor field-effect transistors

    NASA Technical Reports Server (NTRS)

    Johnson, Gregory A.; Kapoor, Vik J.

    1991-01-01

    Plasma-deposited germanium nitride was investigated for the first time as a possible gate insulator for InP compound semiconductor metal-insulator-semiconductor FET (MISFET) technology. The germanium nitride films were successfully deposited in a capacitively coupled parallel plate reactor at 13.56 MHz operation using GeH4/N2/NH3 and GeH4/N2 mixtures as reactant gases. The former process produced better quality films with enhanced uniformity, increased deposition rates, and increased resistivity. The breakdown field strength of the films was greater than 10 to the 6th V/cm. Auger electron spectroscopy did not indicate significant chemical composition differences between the two processes. For MISFETs with 2-micron channel lengths fabricated on InP, the device transconductance and threshold voltage for the GeH4/N2/NH3 process were 17 mS/mm and -3.6 V, respectively. The drain-source breakdown voltages were greater than 10 V.

  8. Recombination and thin film properties of silicon nitride and amorphous silicon passivated c-Si following ammonia plasma exposure

    SciTech Connect

    Wan, Yimao; Thomson, Andrew F.; Cuevas, Andres; McIntosh, Keith R.

    2015-01-26

    Recombination at silicon nitride (SiN{sub x}) and amorphous silicon (a-Si) passivated crystalline silicon (c-Si) surfaces is shown to increase significantly following an ammonia (NH{sub 3}) plasma exposure at room temperature. The effect of plasma exposure on chemical structure, refractive index, permittivity, and electronic properties of the thin films is also investigated. It is found that the NH{sub 3} plasma exposure causes (i) an increase in the density of Si≡N{sub 3} groups in both SiN{sub x} and a-Si films, (ii) a reduction in refractive index and permittivity, (iii) an increase in the density of defects at the SiN{sub x}/c-Si interface, and (iv) a reduction in the density of positive charge in SiN{sub x}. The changes in recombination and thin film properties are likely due to an insertion of N–H radicals into the bulk of SiN{sub x} or a-Si. It is therefore important for device performance to minimize NH{sub 3} plasma exposure of SiN{sub x} or a-Si passivating films during subsequent fabrication steps.

  9. Recombination and thin film properties of silicon nitride and amorphous silicon passivated c-Si following ammonia plasma exposure

    NASA Astrophysics Data System (ADS)

    Wan, Yimao; McIntosh, Keith R.; Thomson, Andrew F.; Cuevas, Andres

    2015-01-01

    Recombination at silicon nitride (SiNx) and amorphous silicon (a-Si) passivated crystalline silicon (c-Si) surfaces is shown to increase significantly following an ammonia (NH3) plasma exposure at room temperature. The effect of plasma exposure on chemical structure, refractive index, permittivity, and electronic properties of the thin films is also investigated. It is found that the NH3 plasma exposure causes (i) an increase in the density of Si≡N3 groups in both SiNx and a-Si films, (ii) a reduction in refractive index and permittivity, (iii) an increase in the density of defects at the SiNx/c-Si interface, and (iv) a reduction in the density of positive charge in SiNx. The changes in recombination and thin film properties are likely due to an insertion of N-H radicals into the bulk of SiNx or a-Si. It is therefore important for device performance to minimize NH3 plasma exposure of SiNx or a-Si passivating films during subsequent fabrication steps.

  10. Characterization of hydrogen-plasma interactions with photoresist, silicon, and silicon nitride surfaces

    SciTech Connect

    Thedjoisworo, Bayu A.; Cheung, David; Zamani, Davoud

    2012-05-15

    For the 45 nm technology node and beyond, a major challenge is to achieve reasonably high photoresist ash rates while minimizing the loss of the silicon (Si) substrate and its nitride (Si{sub 3}N{sub 4}). Accordingly, an objective of this work is to characterize the photoresist strip rate under varying conditions of H{sub 2} plasma and the effects of these conditions on Si and Si{sub 3}N{sub 4} etch rates. In addition, we discuss in detail the fundamental mechanisms of the reactions between H atoms and the above substrates and successfully reconcile the process trends obtained with the reaction mechanisms. In this work, photoresist, Si, and Si{sub 3}N{sub 4} films were exposed to downstream pure-H{sub 2} discharges and their removal rates were characterized by ellipsometry as a function of the following parameters: substrate temperature, reactor pressure, H{sub 2} flow rate, and source power. The authors found that the H{sub 2}-based dry ash and Si{sub 3}N{sub 4} etch are both thermally activated reactions, evidenced by the steady increase in etch rate as a function of temperature, with activation energies of {approx}5.0 and {approx}2.7 kcal/mol, respectively. The Si substrate exhibits a rather unique behavior where the etch rate increases initially to a maximum, which occurs at {approx}40 deg. C, and then decreases upon a further increase in temperature. The decrease in the Si etch rate at higher temperatures is attributed to the activation of competing side reactions that consume the chemisorbed H atoms on the Si surface, which then suppresses the Si-etch step. The photoresist and Si{sub 3}N{sub 4} removal rates increase initially with increasing pressure, reaching maxima at {approx}800 and 2000 mTorr, respectively, beyond which the removal rates drop with increasing pressure. The initial increase in removal rate at the low-pressure regime is attributed to the increased atomic-hydrogen density, whereas the decrease in ash rate at the high-pressure regime could be

  11. Growth of ultrananocrystalline diamond film by DC Arcjet plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Chen, G. C.; Li, B.; Yan, Z. Q.; Liu, J.; Lu, F. X.; Ye, H.

    2012-06-01

    Self-standing diamond films were grown by DC Arcjet plasma enhanced chemical vapor deposition (CVD). The feed gasses were Ar/H2/CH4, in which the flow ratio of CH4 to H2 (F/F) was varied from 5% to 20%. Two distinct morphologies were observed by scanning electron microscope (SEM), i.e. the "pineapple-like" morphology and the "cauliflower-like" morphology. It was found that the morphologies of the as-grown films are strongly dependent on the flow ratio of CH4 to H2 in the feed gasses. High resolution transmission electron microscope (HRTEM) survey results revealed that there were nanocrystalline grains within the "pineapple-like" films whilst there were ultrananocrystalline grains within "cauliflower-like" films. X-ray diffraction (XRD) results suggested that (110) crystalline plane was the dominant surface in the "cauliflower-like" films whilst (100) crystalline plane was the dominant surface in the "pineapple-like" films. Raman spectroscopy revealed that nanostructured carbon features could be observed in both types of films. Plasma diagnosis was carried out in order to understand the morphology dependent growth mechanism. It could be concluded that the film morphology was strongly influenced by the density of gas phases. The gradient of C2 radical was found to be different along the growth direction under the different growth conditions.

  12. Effect of a floating circular aperture on a dc glow discharge dusty plasma

    NASA Astrophysics Data System (ADS)

    Heinrich, Jonathon R.; Kim, Su-Hyun; Merlino, Robert L.

    2009-11-01

    We have investigated novel effects observed when a floating aperture, either 6 mm or 8 mm in diameter, is placed 1-2 cm in front of an anode disk (4 cm diameter) that is used to form a dc glow discharge dusty plasma. Dust is incorporated into the anode glow plasma from a tray located below the anode which contained kaolin powder. The glow discharge traps particles with an average size of 1 micron. When the aperture is placed in front of the disk, well-defined pear-shaped or spherical dust clouds are formed, depending on the diameter of the aperture and its distance from the anode. The dust interacts with the aperture through the potential structure associated with the floating (negative) plate in which the aperture is located. The dust cloud is imaged using a CCD camera and a thin sheet of 532 nm laser light. Some of the effects observed include: outwardly expanding spherical dust acoustic waves and shocks, dust rotation around a void formed at the aperture, and a dust/discharge instability in which the discharge is periodically quenched and reignited while the dust cloud expands and contracts, with the dust retaining a residual charge.

  13. Epitaxial Overgrowth of Gallium Nitride Nano-Rods on Silicon (111) Substrates by RF-Plasma-Assisted Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Jui-Tai Ku,; Tsung-Hsi Yang,; Jet-Rung Chang,; Yuen-Yee Wong,; Wu-Ching Chou,; Chun-Yen Chang,; Chiang-Yao Chen,

    2010-04-01

    Strain-free gallium nitride (GaN) overgrowth on GaN nano-rods is realized by RF-plasma assisted molecular beam epitaxy (RF-MBE) on silicon (Si) substrate. The strain-free condition was identified by the strong free A exciton (FXA) photoluminescence (PL) peak at 3.478 eV and the E2 high phonon Raman shift of 567 cm-1. It is clearly demonstrated that the critical diameter of GaN nano-rods is around 80 nm for the overgrowth of strain-free GaN. The blue-shift of PL peak energy and phonon Raman energy with decreasing the diameter of nano-rod result from the strain relaxation of overgrowth GaN.

  14. Selective growth of boron nitride nanotubes by plasma-enhanced chemical vapor deposition at low substrate temperature

    NASA Astrophysics Data System (ADS)

    Guo, L.; Singh, R. N.

    2008-02-01

    Hexagonal boron nitride nanotubes (BNNTs) were synthesized at a low substrate temperature of 800 °C on nickel (Ni) coated oxidized Si(111) wafers in a microwave plasma-enhanced chemical vapor deposition system (MPCVD) by decomposition and reaction of gas mixtures consisting of B2H6-NH3-H2. The 1D BN nanostructures grew preferentially on Ni catalyst islands with a small thickness only. In situ mass spectroscopic analysis and optical emission spectroscopy were used to identify the gas reactions responsible for the BNNT formation. The morphology and structural properties of the deposits were analyzed by SEM, TEM, EDX, SAD and Raman spectroscopy. The growth mechanism of the BNNTs was identified.

  15. Epitaxial Overgrowth of Gallium Nitride Nano-Rods on Silicon (111) Substrates by RF-Plasma-Assisted Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Ku, Jui-Tai; Yang, Tsung-Hsi; Chang, Jet-Rung; Wong, Yuen-Yee; Chou, Wu-Ching; Chang, Chun-Yen; Chen, Chiang-Yao

    2010-04-01

    Strain-free gallium nitride (GaN) overgrowth on GaN nano-rods is realized by RF-plasma assisted molecular beam epitaxy (RF-MBE) on silicon (Si) substrate. The strain-free condition was identified by the strong free A exciton (FXA) photoluminescence (PL) peak at 3.478 eV and the E2 high phonon Raman shift of 567 cm-1. It is clearly demonstrated that the critical diameter of GaN nano-rods is around 80 nm for the overgrowth of strain-free GaN. The blue-shift of PL peak energy and phonon Raman energy with decreasing the diameter of nano-rod result from the strain relaxation of overgrowth GaN.

  16. Direct growth of graphene on in situ epitaxial hexagonal boron nitride flakes by plasma-assisted molecular beam epitaxy

    SciTech Connect

    Xu, Zhongguang; Zheng, Renjing; Khanaki, Alireza; Zuo, Zheng; Liu, Jianlin

    2015-11-23

    Hexagonal boron nitride (h-BN) single-crystal domains were grown on cobalt (Co) substrates at a substrate temperature of 850–900 °C using plasma-assisted molecular beam epitaxy. Three-point star shape h-BN domains were observed by scanning electron microscopy, and confirmed by Raman and X-ray photoelectron spectroscopy. The h-BN on Co template was used for in situ growth of multilayer graphene, leading to an h-BN/graphene heterostructure. Carbon atoms preferentially nucleate on Co substrate and edges of h-BN and then grow laterally to form continuous graphene. Further introduction of carbon atoms results in layer-by-layer growth of graphene on graphene and lateral growth of graphene on h-BN until it may cover entire h-BN flakes.

  17. A study of structural and mechanical properties of nano-crystalline tungsten nitride film synthesis by plasma focus

    NASA Astrophysics Data System (ADS)

    Hussnain, Ali; Singh Rawat, Rajdeep; Ahmad, Riaz; Hussain, Tousif; Umar, Z. A.; Ikhlaq, Uzma; Chen, Zhong; Shen, Lu

    2015-02-01

    Nano-crystalline tungsten nitride thin films are synthesized on AISI-304 steel at room temperature using Mather-type plasma focus system. The surface properties of the exposed substrate against different deposition shots are examined for crystal structure, surface morphology and mechanical properties using X-ray diffraction (XRD), atomic force microscope, field emission scanning electron microscope and nano-indenter. The XRD results show the growth of WN and WN2 phases and the development of strain/stress in the deposited films by varying the number of deposition shots. Morphology of deposited films shows the significant change in the surface structure with different ion energy doses (number of deposition shots). Due to the effect of different ion energy doses, the strain/stress developed in the deposited film leads to an improvement of hardness of deposited films.

  18. Low temperature plasma-enhanced atomic layer deposition of thin vanadium nitride layers for copper diffusion barriers

    SciTech Connect

    Rampelberg, Geert; Devloo-Casier, Kilian; Deduytsche, Davy; Detavernier, Christophe; Blasco, Nicolas

    2013-03-18

    Thin vanadium nitride (VN) layers were grown by atomic layer deposition using tetrakis(ethylmethylamino)vanadium and NH{sub 3} plasma at deposition temperatures between 70 Degree-Sign C and 150 Degree-Sign C on silicon substrates and polymer foil. X-ray photoelectron spectroscopy revealed a composition close to stoichiometric VN, while x-ray diffraction showed the {delta}-VN crystal structure. The resistivity was as low as 200 {mu}{Omega} cm for the as deposited films and further reduced to 143 {mu}{Omega} cm and 93 {mu}{Omega} cm by annealing in N{sub 2} and H{sub 2}/He/N{sub 2}, respectively. A 5 nm VN layer proved to be effective as a diffusion barrier for copper up to a temperature of 720 Degree-Sign C.

  19. Combined complementary plasma diagnostics to characterize a 2f plasma with additional DC current with conditioning effects at the chamber wall

    NASA Astrophysics Data System (ADS)

    Klick, Michael; Rothe, Ralf; Baek, Kye Hyun; Lee, Eunwoo

    2016-09-01

    Multiple frequencies and DC current used in a low-pressure plasma rf discharge result in an increased complexity. This needs plasma diagnostics applied, in particular in a plasma process chamber. That is done under manufacturing conditions which restrict the applicable plasma diagnostics to non-invasive methods with small footprint. So plasma chamber parameters, optical emission spectroscopy (OES), and self-excited electron spectroscopy (SEERS) are used to characterize the plasma and to understand chamber wall conditioning effects in an Ar plasma. The parameters are classified according to their origin--the region they are representative for. The center ion density is estimated from the DC current and compared to the SEERS electron density reflecting the electron density close to that at the chamber wall. The conditioning effects are caused by Si sputtering at a Si wafer changing the chamber wall state only when the chamber is clean, subsequent plasmas in the same chamber are not affected in that way. Through the combination of the complementary methods it can be shown that the chamber wall condition finally changes the radial plasma density distribution. Also the heating of electrons in the sheath is shown to be influenced by conditioning effects.

  20. Redeposition in plasma-assisted atomic layer deposition: Silicon nitride film quality ruled by the gas residence time

    SciTech Connect

    Knoops, Harm C. M. E-mail: w.m.m.kessels@tue.nl; Peuter, K. de; Kessels, W. M. M. E-mail: w.m.m.kessels@tue.nl

    2015-07-06

    The requirements on the material properties and growth control of silicon nitride (SiN{sub x}) spacer films in transistors are becoming ever more stringent as scaling of transistor structures continues. One method to deposit high-quality films with excellent control is atomic layer deposition (ALD). However, depositing SiN{sub x} by ALD has turned out to be very challenging. In this work, it is shown that the plasma gas residence time τ is a key parameter for the deposition of SiN{sub x} by plasma-assisted ALD and that this parameter can be linked to a so-called “redeposition effect”. This previously ignored effect, which takes place during the plasma step, is the dissociation of reaction products in the plasma and the subsequent redeposition of reaction-product fragments on the surface. For SiN{sub x} ALD using SiH{sub 2}(NH{sup t}Bu){sub 2} as precursor and N{sub 2} plasma as reactant, the gas residence time τ was found to determine both SiN{sub x} film quality and the resulting growth per cycle. It is shown that redeposition can be minimized by using a short residence time resulting in high-quality films with a high wet-etch resistance (i.e., a wet-etch rate of 0.5 nm/min in buffered HF solution). Due to the fundamental nature of the redeposition effect, it is expected to play a role in many more plasma-assisted ALD processes.

  1. Inactivation of Microcystis aeruginosa by DC glow discharge plasma: Impacts on cell integrity, pigment contents and microcystins degradation.

    PubMed

    Zhang, Hong; Yang, Linfang; Yu, Zengliang; Huang, Qing

    2014-03-15

    We proposed a method to inactivate M. aeruginosa by using discharge plasma taking at the gas-solution interface supplied by DC power. Multiple analysis techniques including fluorescence excitation-emission matrix (EEM) and flow cytometry (FCM) were used to reveal the inactivation mechanism of M. aeruginosa. The photosynthetic pigment contents including phycocyanin, chlorophyll and metabolites were examined quantitatively. The DC glow discharge plasma caused an increased level of reactive oxygen species (ROS), and the damage of M. aeruginosa cells are mainly attributed to the oxidative stress including OH attack and H2O2 oxidation. Our findings demonstrate that plasma oxidation is a promising technology for inactivation of M. aeruginosa cells with simultaneous removal of microcystins and so it may lead us to a new route to efficient treatment of cyanobacterial blooms.

  2. Modeling and experimental validation of a 1.2 MW DC transferred well-type plasma torch

    NASA Astrophysics Data System (ADS)

    Chau, S. W.; Hsu, K. L.; Lin, D. L.; Chen, J. S.; Tzeng, C. C.

    2007-07-01

    This paper discusses the numerical modeling and experimental validation of a 1.2 MW DC transferred plasma torch, which is equipped with a well-type cathode (WTC). In order to investigate the complicated thermal and flow characteristics due to the interaction between the working gas and electric arc, the flow filed inside the plasma torch is modeled by the magnetic-hydrodynamic (MHD) equations. The governing equations are solved numerically using a finite volume discretization for both cold and hot flow simulations. The numerical simulations are then validated by experimental measurements at a specific operation condition. The predicted results successfully reflect some important features of the studied transferred WTC plasma torch.

  3. Improved tribological properties, electrochemical resistance and biocompatibility of AISI 316L stainless steel through duplex plasma nitriding and TiN coating treatment.

    PubMed

    Kao, Wen-Hsien; Su, Yean-Liang; Horng, Jeng-Haur; Hsieh, Yun-Ting

    2017-07-01

    AISI 316L specimens were nitrided using a low temperature (390℃) plasma nitriding process and then coated with a thin layer of titanium nitride by closed field unbalanced magnetron sputtering. The microstructure, adhesion properties and hardness of the duplex-treated samples were examined using X-ray diffraction, scratch testing and nanoindentation, respectively. In addition, the tribological properties were investigated by means of reciprocating wear tests performed against 316L, Si3N4 and Ti6Al4V balls under a load of 10 N for 24 min in 0.9% NaCl solution. The electrochemical resistance of the samples was evaluated by potentiodynamic polarisation tests. Finally, the biocompatibility of the samples was investigated by seeding purified mouse leukemic monocyte macrophage cells (Raw 264.7) on the sample surface for one, three and five days, respectively. In general, the results showed that the duplex nitriding and titanium nitride coating process significantly improved the tribological properties, electrochemical resistance and biocompatibility of the AISI 316L samples.

  4. Structural, morphological and mechanical properties of niobium nitride thin films grown by ion and electron beams emanated from plasma

    NASA Astrophysics Data System (ADS)

    Siddiqui, Jamil; Hussain, Tousif; Ahmad, Riaz; Umar, Zeeshan A.; Abdus Samad, Ubair

    2016-05-01

    The influence of variation in plasma deposition parameters on the structural, morphological and mechanical characteristics of the niobium nitride films grown by plasma-emanated ion and electron beams are investigated. Crystallographic investigation made by X-ray diffractometer shows that the film synthesized at 10 cm axial distance with 15 plasma focus shots (PFS) exhibits better crystallinity when compared to the other deposition conditions. Morphological analysis made by scanning electron microscope reveals a definite granular pattern composed of homogeneously distributed nano-spheroids grown as clustered particles for the film synthesized at 10 cm axial distance for 15 PFS. Roughness analysis demonstrates higher rms roughness for the films synthesized at shorter axial distance and by greater number of PFS. Maximum niobium atomic percentage (35.8) and maximum average hardness (19.4 ± 0.4 GPa) characterized by energy-dispersive spectroscopy and nano-hardness analyzer respectively are observed for film synthesized at 10 cm axial distance with 15 PFS.

  5. Correlation of film density and wet etch rate in hydrofluoric acid of plasma enhanced atomic layer deposited silicon nitride

    SciTech Connect

    Provine, J. Schindler, Peter; Kim, Yongmin; Walch, Steve P.; Kim, Hyo Jin; Kim, Ki-Hyun; Prinz, Fritz B.

    2016-06-15

    The continued scaling in transistors and memory elements has necessitated the development of atomic layer deposition (ALD) of silicon nitride (SiN{sub x}), particularly for use a low k dielectric spacer. One of the key material properties needed for SiN{sub x} films is a low wet etch rate (WER) in hydrofluoric (HF) acid. In this work, we report on the evaluation of multiple precursors for plasma enhanced atomic layer deposition (PEALD) of SiN{sub x} and evaluate the film’s WER in 100:1 dilutions of HF in H{sub 2}O. The remote plasma capability available in PEALD, enabled controlling the density of the SiN{sub x} film. Namely, prolonged plasma exposure made films denser which corresponded to lower WER in a systematic fashion. We determined that there is a strong correlation between WER and the density of the film that extends across multiple precursors, PEALD reactors, and a variety of process conditions. Limiting all steps in the deposition to a maximum temperature of 350 °C, it was shown to be possible to achieve a WER in PEALD SiN{sub x} of 6.1 Å/min, which is similar to WER of SiN{sub x} from LPCVD reactions at 850 °C.

  6. Unintentional consequences of dual mode plasma reactors: Implications for upscaling lab-record silicon surface passivation by silicon nitride

    NASA Astrophysics Data System (ADS)

    Tong, Jingnan; To, Alexander; Lennon, Alison; Hoex, Bram

    2017-08-01

    Silicon nitride (SiN x ) synthesised by low-temperature plasma enhanced chemical vapour deposition (PECVD) is the most extensively used antireflection coating for crystalline silicon solar cells because of its tunable refractive index in combination with excellent levels of surface and bulk passivation. This has attracted a significant amount of research on developing SiN x films towards an optimal electrical and optical performance. Typically, recipes are first optimised in lab-scale reactors and subsequently, the best settings are transferred to high-throughput reactors. In this paper, we show that for one particular, but widely used, PECVD reactor configuration this upscaling is severely hampered by an important experimental artefact. Specifically, we report on the unintentional deposition of a dual layer structure in a dual mode AK 400 plasma reactor from Roth & Rau which has a significant impact on its surface passivation performance. It is found that the radio frequency (RF) substrate bias ignites an unintentional depositing plasma before the ignition of the main microwave (MW) plasma. This RF plasma deposits a Si-rich intervening SiN x layer (refractive index = 2.4) while using a recipe for stoichiometric SiN x . This layer was found to be 18 nm thick in our case and had an extraordinary impact on the Si surface passivation, witnessed by a reduction in effective surface recombination velocity from 22.5 to 6.2 cm/s. This experimental result may explain some “out of the ordinary” excellent surface passivation results reported recently for nearly stoichiometric SiN x films and has significant consequences when transferring these results to high-throughput deposition systems.

  7. On the scaling of rf and dc self-bias voltages with pressure in electronegative capacitively coupled plasmas

    SciTech Connect

    Agarwal, Ankur; Dorf, Leonid; Rauf, Shahid; Collins, Ken

    2012-03-15

    Higher gas densities and lower diffusion losses at higher operating pressures typically lead to increased charged species densities (and hence flux) for a constant power deposition in capacitively coupled plasmas (CCP). As a result, one would expect that the bias radio-frequency (rf) voltage required to deposit a given power in a CCP reactor decreases with increasing operating pressure. These observations may not hold true in multiple frequency CCPs, commonly used for dielectric etching in microelectronics fabrication, due to nonlinear interactions between the rf sources. Wafer-based measurements of the rf and self-generated direct current (dc) bias voltages in a dual-frequency capacitively coupled electronegative plasma were made, which indicate that the rf and dc voltages vary nonmonotonically with pressure. These experimental results are presented in this paper and a computational plasma model is used to explain the experimental observations for varying 60 MHz and 13 MHz powers in the Ar/CF{sub 4}/CHF{sub 3} plasma over a pressure range of 25 to 400 mTorr. The authors found that while the ion density increases with pressure, the increase is most dominant near the electrode with the high frequency source (60 MHz). The rf and dc bias voltages are ultimately influenced by both charged species density magnitudes and spatial profiles.

  8. Non-uniform plasma distribution in dc magnetron sputtering: origin, shape and structuring of spokes

    NASA Astrophysics Data System (ADS)

    Panjan, Matjaž; Loquai, Simon; Ewa Klemberg-Sapieha, Jolanta; Martinu, Ludvik

    2015-12-01

    Non-homogeneous plasma distribution in the form of organized patterns called spokes was first observed in high power impulse magnetron sputtering (HiPIMS). In the present work we investigate the spoke phenomenon in non-pulsed low-current dc magnetron sputtering (DCMS). Using a high-speed camera the spokes were systematically studied with respect to discharge current, pressure, target material and magnetic field strength. Increase in the discharge current and/or gas pressure resulted in the sequential formation of two, then three and more spokes. The observed patterns were reproducible for the same discharge conditions. Spokes at low currents and pressures formed an elongated arrowhead-like shape and were commonly arranged in symmetrical patterns. Similar spoke patterns were observed for different target materials. When using a magnetron with a weaker magnetic field, spokes had an indistinct and diffuse shape, whereas in stronger magnetic fields spokes exhibited an arrowhead-like shape. The properties of spokes are discussed in relation to the azimuthally dependent electron-argon interactions. It is suggested that a single spoke is formed due to local gas breakdown and subsequent electron drift in the azimuthal direction. The spoke is self-sustained by electrons drifting in complex electric and magnetic fields that cause and govern azimuthally dependent processes: ionization, sputtering, and secondary electron emission. In this view plasma evolves from a single spoke into different patterns when discharge conditions are changed either by the discharge current, pressure or magnetic field strength. The azimuthal length of the spoke is associated with the electron-Ar collision frequency which increases with pressure and results in shortening of spoke until an additional spoke forms at a particular threshold pressure. It is proposed that the formation of additional spokes at higher pressures and discharge currents is, in part, related to the increased transport of

  9. DC non-thermal atmospheric-pressure plasma jet generated using a syringe needle electrode

    NASA Astrophysics Data System (ADS)

    Matra, Khanit

    2016-07-01

    Non-thermal plasma jet was generated by applying a dc source voltage between the syringe needle anode with flowing Argon gas and a planar or a hollow copper cathode in an atmospheric-pressure environment. The two operating discharge modes, which were self-pulsing and a continuous discharge mode, these were mainly controlled by the limitations of the current flowing in the discharge circuit. A ballast resistor was an important factor in affecting the limitations of the operating discharge mode. The gas breakdown was initially generated in the self-pulsing discharge mode at the source voltage of 1.2 kV. This was slightly higher than the breakdown voltage at the experimental condition of 1 lpm of Argon and a 1 mm electrode gap distance. The peak self-pulsing discharge currents were up to 15-20 A with a self-pulsing frequency in the range of 10-20 kHz. The continuous discharge mode could be observed at the higher source voltage with the continuous discharge current within the range of a few milliamperes.

  10. Investigation of multifractal nature of floating potential fluctuations obtained from a dc glow discharge magnetized plasma

    NASA Astrophysics Data System (ADS)

    Shaw, Pankaj Kumar; Saha, Debajyoti; Ghosh, Sabuj; Janaki, M. S.; Iyengar, A. N. Sekar

    2017-03-01

    In this paper, multifractal detrended fluctuation analysis (MF-DFA) has been used to analyze the floating potential fluctuations obtained with a Langmuir probe from a dc glow discharge magnetized plasma device. The generalized Hurst exponents (h(q)) , local fluctuation function (Fq(s)) , the Rényi exponents (τ(q)) and the multifractal spectrum F(α) have been calculated by applying the MF-DFA method. The result of the MF-DFA shows the multifractal nature of these fluctuations. We have investigated the influence of magnetic field on the multifractal nature of the fluctuations and it is seen that degree of multifractality is reduced with the increase in the magnetic field strength. The values of h(q) have been restricted between 0.7 and 1 for the magnetized fluctuations. This result is evidence of the existence of long-range correlations in the fluctuations. Furthermore, we employed shuffle and surrogate approaches to analyze the origins of multifractality. Comparing the MF-DFA results for the data set to those for shuffled and surrogate series, we have found that its multifractal nature is due to the existence of significant long-term correlation.

  11. Fabrication of layered self-standing diamond film by dc arc plasma jet chemical vapor deposition

    SciTech Connect

    Chen, G. C.; Dai, F. W.; Li, B.; Lan, H.; Askari, J.; Tang, W. Z.; Lu, F. X.

    2007-01-15

    Layered self-standing diamond films, consisting of an upper layer, buffer layer, and a lower layer, were fabricated by fluctuating the ratio of methane to hydrogen in high power dc arc plasma jet chemical vapor deposition. There were micrometer-sized columnar diamond crystalline grains in both upper layer and lower layer. The size of the columnar diamond crystalline grains was bigger in the upper layer than that in the lower layer. The orientation of the upper layer was (110), while it was (111) for the lower layer. Raman results showed that no sp{sup 3} peak shift was found in the upper layer, but it was found and blueshifted in the lower layer. This indicated that the internal stress within the film body could be tailored by this layered structure. The buffer layer with nanometer-sized diamond grains formed by secondary nucleation was necessary in order to form the layered film. Growth rate was over 10 {mu}m/h in layered self-standing diamond film fabrication.

  12. Analysis of barium and strontium in sediments by dc plasma emission spectrometry

    USGS Publications Warehouse

    Bowker, P.C.; Manheim, F. T.

    1982-01-01

    The dc plasma are is suited to analysis of barium and strontium in a wide range of sedimentary rock matrices, from sands, shales, and carbonates, to ferromanganese nodules. Samples containing 10 ppm to more than 3000 ppm barium and strontium were studied. Both alkali (3500 ppm lithium borate, from a preliminary fusion) and lanthanum salts (1%) in the final solution are needed to achieve freedom from systematic effects due to extreme variation in matrix. In the absence of La, neither Li, Na, K, nor Cs totally eliminated effects of Al and other constituents on emission. Silica addition to the fusion helps achieve proper flux viscosity to aid removal of fused beads from graphite crucibles. The effect of refractory-substance formers such as aluminum with calcium can be reduced or removed by selection of a portion of the are for emission measurement. However, it was decided not to pursue this approach because of loss in analytical sensitivity and need for greater precision in optical adjustment. Analysis of standard rock samples showed generally satisfactory agreement with precision methods of analysis, and some new standard rock data are reported.

  13. Self-sustained criterion with photoionization for positive dc corona plasmas between coaxial cylinders

    SciTech Connect

    Zheng, Yuesheng; Zhang, Bo He, Jinliang

    2015-06-15

    The positive dc corona plasmas between coaxial cylinders in air under the application of a self-sustained criterion with photoionization are investigated in this paper. A photon absorption function suitable for cylindrical electrode, which can characterize the total photons within the ionization region, is proposed on the basis of the classic corona onset criteria. Based on the general fluid model with the self-sustained criterion, the role of photoionization in the ionization region is clarified. It is found that the surface electric field keeps constant under a relatively low corona current, while it is slightly weakened with the increase of the corona current. Similar tendencies can be found under different conductor radii and relative air densities. The small change of the surface electric field will become more significant for the electron density distribution as well as the ionization activity under a high corona current, compared with the results under the assumption of a constant surface field. The assumption that the surface electric field remains constant should be corrected with the increase of the corona current when the energetic electrons with a distance from the conductor surface are concerned.

  14. Use of dc Ar microdischarge with nonlocal plasma for identification of metal samples

    SciTech Connect

    Kudryavtsev, A. A.; Stefanova, M. S.; Pramatarov, P. M.

    2015-04-07

    The possibility of using the collisional electron spectroscopy (CES) method for the detection of atoms from metal samples is experimentally verified. The detection and identification of metal atoms from a Pt sample in the nonlocal plasma of short (without positive column) dc Ar microdischarge at intermediate pressures (5–30 Torr) is realized in this work. Cathode sputtering is used for atomization of the metal under analysis. The identification of the analyzed metal is made from the energy spectra of groups of fast nonlocal electrons—characteristic electrons released in the Penning ionization of the Pt atoms by Ar metastable atoms and molecules. The acquisition of the electron energy spectra is performed using an additional electrode—a sensor located at the boundary of the discharge volume. The Pt characteristic Penning electrons form the maxima in the electron energy spectra at the energies of their appearance, which are 2.6 eV and 1.4 eV. From the measured energy of the maxima, identification of the metal atoms is accomplished. The characteristic Ar maxima due to pair collisions between Ar metastable atoms and molecules and super-elastic collisions are also recorded. This study demonstrates the possibility of creating a novel microplasma analyzer for atoms from metal samples.

  15. Linear and Nonlinear Dust Acoustic Waves, Shocks and Stationary Structures in a dc-Glow-Discharge Dusty Plasma

    NASA Astrophysics Data System (ADS)

    Merlino, Robert

    2011-10-01

    In 1990, Rao, Shukla, and Yu (Planet. Space Sci. 38, 543) predicted the existence of the dust acoustic (DA) wave, a low-frequency (~ few Hz), compressional dust density wave that propagates through a dusty plasma at a phase speed ~ several cm/s. The DA wave was first observed by Chu et. al., (J. Phys. D: Appl. Phys. 27, 296, 1994) in an rf-produced dusty plasma, and by Barkan et. al., (Barkan et. al. Phys. Plasmas 2, 2161, 1995) who obtained video images of the DA wave trains using light scattering from a dust suspension confined in an anodic glow discharge plasma formed within a Q machine plasma. The dispersion relation for DAWs was measured by Thompson et. al., (Phys. Plasmas 4, 2331, 1997) in a dc glow discharge dusty plasma by modulating the discharge current at a set frequency. DAWs have been investigated by many groups both in weakly-coupled and strongly-coupled dusty plasmas (E. Thomas, Jr., Contrib. Plasma Phys. 49, 316, 2009). In most experiments where DA waves are present, the wave amplitude is relatively high, indicating that they are nonlinear. In this talk, results of our recent experiments on DAWs will be presented. The following experiments, performed in a dc glow-discharge dusty plasma will be described: (1) Observations of spontaneously excited nonlinear, cylindrical DAWs, which exhibit confluence of waves propagating at different speeds. (2) Investigations of self-steepening DAWs that develop into DA shocks with thicknesses comparable to the interparticle separation (Heinrich et. al., Phys. Rev. Lett. 103, 115001, 2009). (3) Measurements of the linear growth rates of DAWs excited in merging dust clouds. (4) The formation of stationary, stable dust density structures appearing as non-propagating DAWs (Heinrich et. al., Phys. Rev. E, in press, 2011). This work was performed in collaboration with S. H. Kim, J. R. Heinrich, and J. K. Meyer. Work supported by DOE Grant No. DE-FG01-04ER54795

  16. Advances and directions of ion nitriding/carburizing

    NASA Astrophysics Data System (ADS)

    Spalvins, Talivaldis

    1989-09-01

    Ion nitriding and carburizing are plasma activated thermodynamic processes for the production of case hardened surface layers not only for ferrous materials, but also for an increasing number of nonferrous metals. When the treatment variables are properly controlled, the use of nitrogenous or carbonaceous glow discharge medium offers great flexibility in tailoring surface/near-surface properties independently of the bulk properties. The ion nitriding process has reached a high level of maturity and has gained wide industrial acceptance, while the more recently introduced ion carburizing process is rapidly gaining industrial acceptance. The current status of plasma mass transfer mechanisms into the surface regarding the formation of compound and diffusion layers in ion nitriding and carbon build-up ion carburizing is reviewed. In addition, the recent developments in design and construction of advanced equipment for obtaining optimized and controlled case/core properties is summarized. Also, new developments and trends such as duplex plasma treatments and alternatives to dc diode nitriding are highlighted.

  17. Advances and directions of ion nitriding/carburizing

    NASA Technical Reports Server (NTRS)

    Spalvins, Talivaldis

    1989-01-01

    Ion nitriding and carburizing are plasma activated thermodynamic processes for the production of case hardened surface layers not only for ferrous materials, but also for an increasing number of nonferrous metals. When the treatment variables are properly controlled, the use of nitrogenous or carbonaceous glow discharge medium offers great flexibility in tailoring surface/near-surface properties independently of the bulk properties. The ion nitriding process has reached a high level of maturity and has gained wide industrial acceptance, while the more recently introduced ion carburizing process is rapidly gaining industrial acceptance. The current status of plasma mass transfer mechanisms into the surface regarding the formation of compound and diffusion layers in ion nitriding and carbon build-up ion carburizing is reviewed. In addition, the recent developments in design and construction of advanced equipment for obtaining optimized and controlled case/core properties is summarized. Also, new developments and trends such as duplex plasma treatments and alternatives to dc diode nitriding are highlighted.

  18. Integrated approach for low-temperature synthesis of high-quality silicon nitride films in PECVD using RF-UHF hybrid plasmas

    NASA Astrophysics Data System (ADS)

    Sahu, B. B.; Shin, Kyung S.; Han, Jeon G.

    2016-02-01

    This study investigates low-temperature plasma nitriding of hydrogenated silicon (SiN x :H) film in radio frequency (RF) and RF-ultra-high frequency (UHF) hybrid plasmas. To study the optimized conditions for the deposition of SiN x :H film, this work adopts a systematic plasma diagnostic approach in the nitrogen-silane and nitrogen-silane-ammonia plasmas. This work also evaluates the capability of plasma and radical formation by utilizing different plasma sources in the PECVD process. For the plasma diagnostics, we have purposefully used the combination of optical emission spectroscopy (OES), intensified CCD (ICCD) camera, vacuum ultraviolet absorption spectroscopy (VUVAS), and RF compensated Langmuir probe (LP). Data reveal that there is significant enhancement in the atomic nitrogen radicals, plasma densities, and film properties using the hybrid plasmas. Measurements show that addition of a small amount of NH3 can significantly reduce the electron temperature, plasma, and radical density. Also, optical and chemical properties of the deposited films are investigated on the basis of plasma diagnostics. Good quality SiN x :H films, with atomic nitrogen to hydrogen ratio of 4:1, are fabricated. The plasma chemistry of the hybrid plasmas is also discussed for its utility for plasma applications.

  19. Plasma synthesis and HPHT consolidation of BN nanoparticles, nanospheres, and nanotubes to produce nanocrystalline cubic boron nitride

    NASA Astrophysics Data System (ADS)

    Stout, Christopher

    Plasma methods offer a variety of advantages to nanomaterials synthesis. The process is robust, allowing varying particle sizes and phases to be generated simply by modifying key parameters. The work here demonstrates a novel approach to nanopowder synthesis using inductively-coupled plasma to decompose precursor, which are then quenched to produce a variety of boron nitride (BN)-phase nanoparticles, including cubic phase, along with short-range-order nanospheres (e.g., nano-onions) and BN nanotubes. Cubic BN (c-BN) powders can be generated through direct deposition onto a chilled substrate. The extremely-high pyrolysis temperatures afforded by the equilibrium plasma offer a unique particle growth environment, accommodating long deposition times while exposing resulting powders to temperatures in excess of 5000K without any additional particle nucleation and growth. Such conditions can yield short-range ordered amorphous BN structures in the form of 20nm diameter nanospheres. Finally, when introducing a rapid-quenching counter-flow gas against the plasma jet, high aspect ratio nanotubes are synthesized, which are collected on substrate situated radially. The benefits of these morphologies are also evident in high-pressure/high-temperature consolidation experiments, where nanoparticle phases can offer a favorable conversion route to super-hard c-BN while maintaining nanocrystallinity. Experiments using these morphologies are shown to begin to yield c-BN conversion at conditions as low as 2.0 GPa and 1500°C when using micron sized c-BN seeding to create localized regions of high pressures due to Hertzian forces acting on the nanoparticles.

  20. A review of the gas species activity and control of pulsed plasma technology during the nitriding, carburizing and carbonitriding processes

    SciTech Connect

    Pye, D.

    1995-12-31

    The control of gas activity and process technology has developed tremendously over the past two decades. While once considered to be primitive control systems using simple PID loops with thermocouples that were suspect and unable to perform repeatedly and consistently during the arduous process of plasma nitriding and processing, developments in recent years have elevated the control of the process into what might be considered one of the most controllable processes of the latter part of this century. The advent of plasma processing technology has improved control methods by observing and harnessing each of the various process parameters into many different combinations of control systems. Some of these control systems can control the complete function of the process, thus freeing the operator entirely for other duties, except that of load and unload, to the point where the operator is intimately involved with the process. Some of the control methods report from the process to a PLC through to a PC, and current developments rely entirely on computers and developed software shown on various screens. This presentation will review some of the more common process control methods, including that of highly developed PC systems.

  1. Measurement of the Energy of Nitrogen Ions Produced in Filippov Type Plasma Focus Used for the Nitriding of Titanium

    NASA Astrophysics Data System (ADS)

    Ghareshabani, E.; Mohammadi, M. A.

    2012-12-01

    In this paper the nitrogen ion properties (maximum energy, current density and the most probable energy) are investigated by using Faraday cup in a time of flight method. These ions are produced in a Filippov type plasma focus (Sahand Facility) device and the Faraday cup was placed in a distance range of 18-24 cm from the top of the anode. Maximum and minimum most probable ion energies are 76 and 8.5 keV for the distance range of 18 and 24 cm, respectively. The displacement from 18 to 24 cm at top of the anode the ion current density varies from 4.5 × 106 to 3.2 × 105 (A m-2). For the investigation of the effect of ions bombardment of materials at different positions, at the optimum working conditions of 14 kV as a working voltage, and 0.25 Torr as a gas pressure, titanium samples are placed in a distance of 21, 22, 23 and 24 cm from the top of the anode (θ = 0) and each sample is put under irradiation for 30 plasma shots. The structure of the nitrided surfaces and their morphologies are characterized by X-ray diffractometry and by scanning electron microscopy, respectively. The average crystallite size deduced for (200) and (222) planes of TiN deposited with 30 shots in different distances are estimate to be from ~13 to ~38 nm.

  2. Low-temperature growth of gallium nitride films by inductively coupled-plasma-enhanced reactive magnetron sputtering

    SciTech Connect

    Ni, Chih-Jui; Chau-Nan Hong, Franklin

    2014-05-15

    Gallium nitride (GaN) films were grown on sapphire substrate by reactive magnetron sputtering. Inductively coupled-plasma (ICP) source was installed between the substrate holder and the sputtering target to increase the plasma density and the degree of ionization of nitrogen gas. Liquid Ga and Ar/N{sub 2} were used as the sputtering target and sputtering gases, respectively. X-ray diffraction measurements confirmed that the authors could grow high quality GaN crystallites at 500 °C. However, the crystalline GaN (0002) peak remained even by lowering the growth temperature down to 300 °C. The N:Ga ratio of the film grown at 500 °C was almost 1:1, and the nitrogen composition became higher toward the 1:1 N:Ga ratio with increasing the growth temperature. The high degree of ionization induced by ICP source was essential to the growth of high crystalline quality GaN films.

  3. Surface passivation of p-type Ge substrate with high-quality GeNx layer formed by electron-cyclotron-resonance plasma nitridation at low temperature

    NASA Astrophysics Data System (ADS)

    Fukuda, Yukio; Okamoto, Hiroshi; Iwasaki, Takuro; Otani, Yohei; Ono, Toshiro

    2011-09-01

    We have investigated the effects of the formation temperature and postmetallization annealing (PMA) on the interface properties of GeNx/p-Ge fabricated by the plasma nitridation of Ge substrates using an electron-cyclotron-resonance-generated nitrogen plasma. The nitridation temperature is found to be a critical parameter in improving the finally obtained GeNx/Ge interface properties. The GeNx/Ge formed at room temperature and treated by PMA at 400 °C exhibits the best interface properties with an interface trap density of 1 × 1011 cm-2 eV-1. The GeNx/Ge interface is unpinned and the Fermi level at the Ge surface can move from the valence band edge to the conduction band edge.

  4. A path for synthesis of boron-nitride nanostructures in volume of arc plasma.

    PubMed

    Han, Longtao; Krstić, Predrag

    2017-02-17

    We find a possible channel for direct nanosynthesis of boron-nitride (BN) nanostructures, including growth of BN nanotubes from a mixture of BN diatomic molecules by quantum-classical molecular dynamics simulations. No catalyst or boron nanoparticle is needed for this synthesis, however the conditions for the synthesis of each of the nanostructures, such as temperature and flux of the BN feedstock are identified and are compatible with the conditions in an electric arc at high pressure. We also find that BN nanostructures can be synthetized by feeding a boron nanoparticle by BN diatomic molecules, however if hydrogen rich molecules like NH3 or HBNH are used as a feedstock, two-dimensional nanoflake stable structures are formed.

  5. A path for synthesis of boron-nitride nanostructures in volume of arc plasma

    NASA Astrophysics Data System (ADS)

    Han, Longtao; Krstić, Predrag

    2017-02-01

    We find a possible channel for direct nanosynthesis of boron-nitride (BN) nanostructures, including growth of BN nanotubes from a mixture of BN diatomic molecules by quantum-classical molecular dynamics simulations. No catalyst or boron nanoparticle is needed for this synthesis, however the conditions for the synthesis of each of the nanostructures, such as temperature and flux of the BN feedstock are identified and are compatible with the conditions in an electric arc at high pressure. We also find that BN nanostructures can be synthetized by feeding a boron nanoparticle by BN diatomic molecules, however if hydrogen rich molecules like NH3 or HBNH are used as a feedstock, two-dimensional nanoflake stable structures are formed.

  6. Scaled synthesis of boron nitride nanotubes, nanoribbons, and nanococoons using direct feedstock injection into an extended-pressure, inductively-coupled thermal plasma.

    PubMed

    Fathalizadeh, Aidin; Pham, Thang; Mickelson, William; Zettl, Alex

    2014-08-13

    A variable pressure (up to 10 atm) powder/gas/liquid injection inductively coupled plasma system has been developed and used to produce high-quality boron nitride nanotubes (BNNTs) at continuous production rates of 35 g/h. Under suitable conditions, collapsed BN nanotubes (i.e., nanoribbons), and closed shell BN capsules (i.e., nanococoons) are also obtained. The process is adaptable to a large variety of feedstock materials.

  7. Scaled Synthesis of Boron Nitride Nanotubes, Nanoribbons, and Nanococoons Using Direct Feedstock Injection into an Extended-Pressure, Inductively-Coupled Thermal Plasma

    NASA Astrophysics Data System (ADS)

    Fathalizadeh, Aidin; Pham, Thang; Mickelson, William; Zettl, Alex

    2015-03-01

    A variable pressure (up to 10 atm) powder or gas injection inductively coupled plasma system has been developed and used to produce high-quality boron nitride nanotubes (BNNTs) at continuous production rates of 35 g/h. Under suitable conditions, collapsed BN nanotubes (i.e., nanoribbons), and closed shell BN capsules (i.e., nanococoons) are also obtained. The process is adaptable to a large variety of feedstock materials.

  8. Development of a DC Glow Discharge Exhibit for the Demonstration of Plasma Behavior in a Magnetic Field

    NASA Astrophysics Data System (ADS)

    Bruder, Daniel

    2010-11-01

    The DC Glow Discharge Exhibit is intended to demonstrate the effects a magnetic field produces on a plasma in a vacuum chamber. The display, which will be featured as a part of The Liberty Science Center's ``Energy Quest Exhibition,'' consists of a DC glow discharge tube and information panels to educate the general public on plasma and its relation to fusion energy. Wall posters and an information booklet will offer brief descriptions of fusion-based science and technology, and will portray plasma's role in the development of fusion as a viable source of energy. The display features a horse-shoe magnet on a movable track, allowing viewers to witness the effects of a magnetic field upon a plasma. The plasma is created from air within a vacuum averaging between 100-200 mTorr. Signage within the casing describes the hardware components. The display is pending delivery to The Liberty Science Center, and will replace a similar, older exhibit presently at the museum.

  9. DC-driven plasma gun: self-oscillatory operation mode of atmospheric-pressure helium plasma jet comprised of repetitive streamer breakdowns

    NASA Astrophysics Data System (ADS)

    Wang, Xingxing; Shashurin, Alexey

    2017-02-01

    This paper presents and studies helium atmospheric pressure plasma jet comprised of a series of repetitive streamer breakdowns, which is driven by pure DC high voltage (self-oscillatory behavior). The repetition frequency of the breakdowns is governed by the geometry of discharge electrodes/surroundings and gas flow rate. Each next streamer is initiated when the electric field on the anode tip recovers after the previous breakdown and reaches the breakdown threshold value of about 2.5 kV cm-1. One type of the helium plasma gun designed using this operational principle is demonstrated. The gun operates on about 3 kV DC high voltage and is comprised of the series of the repetitive streamer breakdowns at a frequency of about 13 kHz.

  10. Deposition and characterization of molybdenum thin films using dc-plasma magnetron sputtering

    SciTech Connect

    Khan, Majid; Islam, Mohammad

    2013-12-15

    Molebdenum (Mo) thin films were deposited on well-cleaned soda-lime glass substrates using DC-plasma magnetron sputtering. In the design of experiment deposition was optimized for maximum beneficial characteristics by monitoring effect of process variables such as deposition power (100–200 W). Their electrical, structural and morphological properties were analyzed to study the effect of these variables. The electrical resistivity of Mo thin films could be reduced by increasing deposition power. Within the range of analyzed deposition power, Mo thin films showed a mono crystalline nature and the crystallites were found to have an orientation along [110] direction. The surface morphology of thin films showed that a highly dense micro structure has been obtained. The surface roughness of films increased with deposition power. The adhesion of Mo thin films could be improved by increasing the deposition power. Atomic force microscopy was used for the topographical study of the films and to determine the roughness of the films. X-ray diffractrometer and scanning electron microscopy analysis were used to investigate the crystallinity and surface morphology of the films. Hall effect measurement system was used to find resistivity, carrier mobility and carrier density of deposited films. The adhesion test was performed using scotch hatch tape adhesion test. Mo thin films prepared at deposition power of 200 W, substrate temperature of 23°C and Ar pressure of 0.0123 mbar exhibited a mono crystalline structure with an orientation along (110) direction, thickness of ∼550 nm and electrical resistivity value of 0.57 × 10{sup −4} Ω cm.

  11. Comparative study on nitridation and oxidation plasma interface treatment for AlGaN/GaN MIS-HEMTs with AlN gate dielectric

    NASA Astrophysics Data System (ADS)

    Zhu, Jie-Jie; Ma, Xiao-Hua; Hou, Bin; Chen, Li-Xiang; Zhu, Qing; Hao, Yue

    2017-02-01

    This paper demonstrated the comparative study on interface engineering of AlN/AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs) by using plasma interface pre-treatment in various ambient gases. The 15 nm AlN gate dielectric grown by plasma-enhanced atomic layer deposition significantly suppressed the gate leakage current by about two orders of magnitude and increased the peak field-effect mobility by more than 50%. NH3/N2 nitridation plasma treatment (NPT) was used to remove the 3 nm poor-quality interfacial oxide layer and N2O/N2 oxidation plasma treatment (OPT) to improve the quality of interfacial layer, both resulting in improved dielectric/barrier interface quality, positive threshold voltage (V th) shift larger than 0.9 V, and negligible dispersion. In comparison, however, NPT led to further decrease in interface charges by 3.38 × 1012 cm‑2 and an extra positive V th shift of 1.3 V. Analysis with fat field-effect transistors showed that NPT resulted in better sub-threshold characteristics and transconductance linearity for MIS-HEMTs compared with OPT. The comparative study suggested that direct removing the poor interfacial oxide layer by nitridation plasma was superior to improving the quality of interfacial layer by oxidation plasma for the interface engineering of GaN-based MIS-HEMTs.

  12. An experimental study on discharge characteristics in a pulsed-dc atmospheric pressure CH3OH/Ar plasma jet

    NASA Astrophysics Data System (ADS)

    Qian, Muyang; Liu, Sanqiu; Yang, Congying; Pei, Xuekai; Lu, Xinpei; Zhang, Jialiang; Wang, Dezhen

    2016-10-01

    Recently, C/H/Ar plasma discharges found enormous potential and possibility in carbonaceous compounds conversion and production. In this work, a pulsed-dc CH3OH/Ar plasma jet generated at atmospheric pressure is investigated by means of optical and electrical diagnosis concerning the variation of its basic parameters, absolute concentration of OH radicals, and plasma temperature with different CH3OH/Ar volume ratios, in the core region of discharge with needle-to-ring electrode configuration. The voltage-current characteristics are also measured at different CH3OH/Ar ratios. Laser-induced fluorescence (LIF) results here show that only small amounts of added methanol vapor to argon plasma (about 0.05% CH3OH/Ar volume ratio) is favorable for the production of OH radicals. The optical emission lines of CH, CN, and C2 radicals have been detected in the CH3OH/Ar plasma. And, the plasma temperatures increase with successive amount of added methanol vapor to the growth plasma. Moreover, qualitative discussions are presented regarding the mechanisms for methanol dissociation and effect of the CH3OH component on the Ar plasma discharge at atmospheric pressure.

  13. Structural evolution and photoluminescence of annealed Si-rich nitride with Si quantum dots prepared by plasma enhanced chemical vapor deposition

    SciTech Connect

    Zeng, Xiangbin Liao, Wugang; Wen, Guozhi; Wen, Xixing; Zheng, Wenjun

    2014-04-21

    Silicon-rich nitride films were deposited by plasma enhanced chemical vapor deposition. Silicon quantum dots (Si QDs) were formed by post-thermal annealing processing verified using the High-Resolution Transmission Electron Microscope. The 1100 °C thermal annealing leads to the nucleation of silicon atoms, the growth of Si QDs, and the rearrangement of Si 2p and N 1s elements. The structural evolution of silicon-rich nitride thin film with post annealing promotes the formation of Si QDs and Si{sub 3}N{sub 4} matrix. We also investigated the effect of the NH{sub 3}-to-SiH{sub 4} ratio R on the photoluminescence (PL) of SiN{sub x} with Si QDs. We found that the broad blue luminescence originates from both quantum confined effect and radiative defects. The intensity of the PL was changed by adjusting the NH{sub 3} flow rate. The increase of R could limit the transformation of Si QDs from amorphous to crystalline status, meanwhile lead to the alteration of distribution of defect states. These can help to understand the annealing-dependent characteristics, the PL mechanisms of silicon-rich nitride and to optimize the fabrication process of Si QDs embedded in nitride.

  14. Boron nitride phosphide thin films grown on quartz substrate by hot-filament and plasma-assisted chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Zhang, X. W.; Xu, S. Y.; Han, G. R.

    2004-10-01

    Boron nitride phosphide films are, for the first time, grown on transparent quartz substrate by hot filament and radio-frequency plasma co-assisted chemical vapor deposition technique. XPS, XRD, SEM, and UV measurements are performed to study the chemical composition, crystallization, microstructure, and optical absorption, respectively. A centipede-like microstructure and undulating ground morphology on the film surface are observed, and their growth mechanism is speculated upon. The chemical composition is determined as BN1-xPx, whose characteristic XRD peak is preliminarily identified. The optical band gap can be modulated between 5.52 eV and 3.74 eV, simply by adjusting the phosphorus content in BN1-xPx through modifying the PH3 flux during the film-deposition process. The merits of the BN1-xPx film, such as high ultraviolet photoelectric sensitivity with negligible sensitivity in the visible region, modifiable wide optical band gap, and good adhesion on transparent substrate, suggest potential applications for ultraviolet photo-electronics.

  15. Large-scale synthesis of uniform hexagonal boron nitride films by plasma-enhanced atomic layer deposition

    PubMed Central

    Park, Hamin; Kim, Tae Keun; Cho, Sung Woo; Jang, Hong Seok; Lee, Sang Ick; Choi, Sung-Yool

    2017-01-01

    Hexagonal boron nitride (h-BN) has been previously manufactured using mechanical exfoliation and chemical vapor deposition methods, which make the large-scale synthesis of uniform h-BN very challenging. In this study, we produced highly uniform and scalable h-BN films by plasma-enhanced atomic layer deposition, which were characterized by various techniques including atomic force microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray diffraction. The film composition studied by X-ray photoelectron spectroscopy and Auger electron spectroscopy corresponded to a B:N stoichiometric ratio close to 1:1, and the band-gap value (5.65 eV) obtained by electron energy loss spectroscopy was consistent with the dielectric properties. The h-BN-containing capacitors were characterized by highly uniform properties, a reasonable dielectric constant (3), and low leakage current density, while graphene on h-BN substrates exhibited enhanced electrical performance such as the high carrier mobility and neutral Dirac voltage, which resulted from the low density of charged impurities on the h-BN surface. PMID:28054603

  16. Direct growth of hexagonal boron nitride/graphene heterostructures on cobalt foil substrates by plasma-assisted molecular beam epitaxy

    SciTech Connect

    Xu, Zhongguang; Khanaki, Alireza; Tian, Hao; Zheng, Renjing; Suja, Mohammad; Liu, Jianlin; Zheng, Jian-Guo

    2016-07-25

    Graphene/hexagonal boron nitride (G/h-BN) heterostructures have attracted a great deal of attention because of their exceptional properties and wide variety of potential applications in nanoelectronics. However, direct growth of large-area, high-quality, and stacked structures in a controllable and scalable way remains challenging. In this work, we demonstrate the synthesis of h-BN/graphene (h-BN/G) heterostructures on cobalt (Co) foil by sequential deposition of graphene and h-BN layers using plasma-assisted molecular beam epitaxy. It is found that the coverage of h-BN layers can be readily controlled on the epitaxial graphene by growth time. Large-area, uniform-quality, and multi-layer h-BN films on thin graphite layers were achieved. Based on an h-BN (5–6 nm)/G (26–27 nm) heterostructure, capacitor devices with Co(foil)/G/h-BN/Co(contact) configuration were fabricated to evaluate the dielectric properties of h-BN. The measured breakdown electric field showed a high value of ∼2.5–3.2 MV/cm. Both I-V and C-V characteristics indicate that the epitaxial h-BN film has good insulating characteristics.

  17. Structural and magnetic phase transitions in chromium nitride thin films grown by rf nitrogen plasma molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Alam, Khan; Disseler, Steven M.; Ratcliff, William D.; Borchers, Julie A.; Ponce-Pérez, Rodrigo; Cocoletzi, Gregorio H.; Takeuchi, Noboru; Foley, Andrew; Richard, Andrea; Ingram, David C.; Smith, Arthur R.

    2017-09-01

    A magnetostructural phase transition is investigated in single-crystal chromium nitride (CrN) thin films grown by rf plasma molecular beam epitaxy on MgO(001) substrates. While still within the vacuum environment following molecular beam epitaxy growth, in situ low-temperature scanning tunneling microscopy, and in situ variable low-temperature reflection high-energy electron diffraction are applied, revealing an atomically smooth and metallic CrN(001) surface, and an in-plane structural transition from 1 ×1 (primitive CrN unit cell) to √{2 }×√{2 }-R 45∘ with a transition temperature of (278 ±3 ) K, respectively. Ex situ temperature-dependent measurements using neutron diffraction are also performed, looking at the structural peaks and likewise revealing a first-order structural transition along the [111] out-of-plane direction, with transition temperatures of (268 ± 3) K. Turning to the magnetic peaks, neutron diffraction confirms a clear magnetic transition from paramagnetic at room temperature to antiferromagnetic at low temperatures with a sharp, first-order phase transition and a Néel temperature of (270 ±2 ) K or (280 ±2 ) K for two different films. In addition to the experimental measurements of structural and magnetic ordering, we also discuss results from first-principles theoretical calculations which explore various possible magnetostructural models.

  18. Approaching Defect-free Amorphous Silicon Nitride by Plasma-assisted Atomic Beam Deposition for High Performance Gate Dielectric

    PubMed Central

    Tsai, Shu-Ju; Wang, Chiang-Lun; Lee, Hung-Chun; Lin, Chun-Yeh; Chen, Jhih-Wei; Shiu, Hong-Wei; Chang, Lo-Yueh; Hsueh, Han-Ting; Chen, Hung-Ying; Tsai, Jyun-Yu; Lu, Ying-Hsin; Chang, Ting-Chang; Tu, Li-Wei; Teng, Hsisheng; Chen, Yi-Chun; Chen, Chia-Hao; Wu, Chung-Lin

    2016-01-01

    In the past few decades, gate insulators with a high dielectric constant (high-k dielectric) enabling a physically thick but dielectrically thin insulating layer, have been used to replace traditional SiOx insulator and to ensure continuous downscaling of Si-based transistor technology. However, due to the non-silicon derivative natures of the high-k metal oxides, transport properties in these dielectrics are still limited by various structural defects on the hetero-interfaces and inside the dielectrics. Here, we show that another insulating silicon compound, amorphous silicon nitride (a-Si3N4), is a promising candidate of effective electrical insulator for use as a high-k dielectric. We have examined a-Si3N4 deposited using the plasma-assisted atomic beam deposition (PA-ABD) technique in an ultra-high vacuum (UHV) environment and demonstrated the absence of defect-related luminescence; it was also found that the electronic structure across the a-Si3N4/Si heterojunction approaches the intrinsic limit, which exhibits large band gap energy and valence band offset. We demonstrate that charge transport properties in the metal/a-Si3N4/Si (MNS) structures approach defect-free limits with a large breakdown field and a low leakage current. Using PA-ABD, our results suggest a general strategy to markedly improve the performance of gate dielectric using a nearly defect-free insulator. PMID:27325155

  19. Approaching Defect-free Amorphous Silicon Nitride by Plasma-assisted Atomic Beam Deposition for High Performance Gate Dielectric.

    PubMed

    Tsai, Shu-Ju; Wang, Chiang-Lun; Lee, Hung-Chun; Lin, Chun-Yeh; Chen, Jhih-Wei; Shiu, Hong-Wei; Chang, Lo-Yueh; Hsueh, Han-Ting; Chen, Hung-Ying; Tsai, Jyun-Yu; Lu, Ying-Hsin; Chang, Ting-Chang; Tu, Li-Wei; Teng, Hsisheng; Chen, Yi-Chun; Chen, Chia-Hao; Wu, Chung-Lin

    2016-06-21

    In the past few decades, gate insulators with a high dielectric constant (high-k dielectric) enabling a physically thick but dielectrically thin insulating layer, have been used to replace traditional SiOx insulator and to ensure continuous downscaling of Si-based transistor technology. However, due to the non-silicon derivative natures of the high-k metal oxides, transport properties in these dielectrics are still limited by various structural defects on the hetero-interfaces and inside the dielectrics. Here, we show that another insulating silicon compound, amorphous silicon nitride (a-Si3N4), is a promising candidate of effective electrical insulator for use as a high-k dielectric. We have examined a-Si3N4 deposited using the plasma-assisted atomic beam deposition (PA-ABD) technique in an ultra-high vacuum (UHV) environment and demonstrated the absence of defect-related luminescence; it was also found that the electronic structure across the a-Si3N4/Si heterojunction approaches the intrinsic limit, which exhibits large band gap energy and valence band offset. We demonstrate that charge transport properties in the metal/a-Si3N4/Si (MNS) structures approach defect-free limits with a large breakdown field and a low leakage current. Using PA-ABD, our results suggest a general strategy to markedly improve the performance of gate dielectric using a nearly defect-free insulator.

  20. Direct growth of hexagonal boron nitride/graphene heterostructures on cobalt foil substrates by plasma-assisted molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Xu, Zhongguang; Khanaki, Alireza; Tian, Hao; Zheng, Renjing; Suja, Mohammad; Zheng, Jian-Guo; Liu, Jianlin

    2016-07-01

    Graphene/hexagonal boron nitride (G/h-BN) heterostructures have attracted a great deal of attention because of their exceptional properties and wide variety of potential applications in nanoelectronics. However, direct growth of large-area, high-quality, and stacked structures in a controllable and scalable way remains challenging. In this work, we demonstrate the synthesis of h-BN/graphene (h-BN/G) heterostructures on cobalt (Co) foil by sequential deposition of graphene and h-BN layers using plasma-assisted molecular beam epitaxy. It is found that the coverage of h-BN layers can be readily controlled on the epitaxial graphene by growth time. Large-area, uniform-quality, and multi-layer h-BN films on thin graphite layers were achieved. Based on an h-BN (5-6 nm)/G (26-27 nm) heterostructure, capacitor devices with Co(foil)/G/h-BN/Co(contact) configuration were fabricated to evaluate the dielectric properties of h-BN. The measured breakdown electric field showed a high value of ˜2.5-3.2 MV/cm. Both I-V and C-V characteristics indicate that the epitaxial h-BN film has good insulating characteristics.

  1. Large-scale synthesis of uniform hexagonal boron nitride films by plasma-enhanced atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Park, Hamin; Kim, Tae Keun; Cho, Sung Woo; Jang, Hong Seok; Lee, Sang Ick; Choi, Sung-Yool

    2017-01-01

    Hexagonal boron nitride (h-BN) has been previously manufactured using mechanical exfoliation and chemical vapor deposition methods, which make the large-scale synthesis of uniform h-BN very challenging. In this study, we produced highly uniform and scalable h-BN films by plasma-enhanced atomic layer deposition, which were characterized by various techniques including atomic force microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray diffraction. The film composition studied by X-ray photoelectron spectroscopy and Auger electron spectroscopy corresponded to a B:N stoichiometric ratio close to 1:1, and the band-gap value (5.65 eV) obtained by electron energy loss spectroscopy was consistent with the dielectric properties. The h-BN-containing capacitors were characterized by highly uniform properties, a reasonable dielectric constant (3), and low leakage current density, while graphene on h-BN substrates exhibited enhanced electrical performance such as the high carrier mobility and neutral Dirac voltage, which resulted from the low density of charged impurities on the h-BN surface.

  2. Wear resistance of TiN(Ti2N)/Ti composite layer formed on C17200 alloy by plasma surface Ti-alloying and nitriding

    NASA Astrophysics Data System (ADS)

    Liu, L.; Shen, H. H.; Liu, X. Z.; Guo, Q.; Meng, T. X.; Wang, Z. X.; Yang, H. J.; Liu, X. P.

    2016-12-01

    The duplex treatment of plasma Ti-alloying and plasma nitriding was applied on the surface of C17200 alloy to improve its wear resistance. C17200 substrate was alloyed with Ti using double glow plasma alloying to form a Ti-alloyed layer in its surface, and then treated by plasma nitriding to make a TiN(Ti2N) alloying layer based on the Ti-alloyed surface. The microstructure and formation mechanism were studied by using GDOES, XRD and SEM. The hardness, tribological property and electrical conductivity of C17200 alloy after plasma alloying and nitriding were investigated by mean of micro-hardness tester, friction and wear testers as well as impedance analyzers. Modulus of elasticity and the adhesive strength of TiN(Ti2N)/Ti composite layer were evaluated by nano-indenter and scratch tester. The result shows that a TiN(Ti2N)-Ti-Be-Cu composite layer with a thickness of 27 μm is formed in the C17200 surface and is mainly composed of TiN, Ti2N, Cu(Ti) solid solution, etc. The composite alloying surface consists of the hard TiN(Ti2N)-rich layer on the top surface and Ti-Cu-Be diffusion layer, showing a strong adhesive strength with the C17200 substrate and a little decrease in the modulus of elasticity. A certain amount of Cu and Be together with TiN/Ti2N exists in the outmost, resulting in a better combination of wear resistance and conductive performance.

  3. Design and Development of High Voltage Direct Current (DC) Sources for the Solar Array Module Plasma Interaction Experiment

    NASA Technical Reports Server (NTRS)

    Bibyk, Irene K.; Wald, Lawrence W.

    1995-01-01

    Two programmable, high voltage DC power supplies were developed as part of the flight electronics for the Solar Array Module Plasma Interaction Experiment (SAMPIE). SAMPIE's primary objectives were to study and characterize the high voltage arcing and parasitic current losses of various solar cells and metal samples within the space plasma of low earth orbit (LEO). High voltage arcing can cause large discontinuous changes in spacecraft potential which lead to damage of the power system materials and significant Electromagnetic Interference (EMI). Parasitic currents cause a change in floating potential which lead to reduced power efficiency. These primary SAMPIE objectives were accomplished by applying artificial biases across test samples over a voltage range from -600 VDC to +300 VDC. This paper chronicles the design, final development, and test of the two programmable high voltage sources for SAMPIE. The technical challenges to the design for these power supplies included vacuum, space plasma effects, thermal protection, Shuttle vibrations and accelerations.

  4. Continuous wavelet transform analysis for self-similarity properties of turbulence in magnetized DC glow discharge plasma

    NASA Astrophysics Data System (ADS)

    Sarma, Bornali; Chauhan, Sourabh S.; Wharton, A. M.; Iyengar, A. N. Sekar; Iyengar

    2013-10-01

    Characterization of self-similarity properties of turbulence in magnetized plasma is being carried out in DC glow discharge plasma. The time series floating potential fluctuation experimental data are acquired from the plasma by Langmuir probe. Continuous wavelet transform (CWT) analysis considering db4 mother wavelet has been applied to the experimental data and self-similarity properties are detected by evaluating the Hurst exponent from the wavelet variance plotting. From the CWT spectrum, effort is made to extract a highly correlated frequency by locating the brightest spot. Accordingly, those signals are treated for finding out correlation dimension and the Liapunov exponent so that the exact frequency responsible for the chaotic behavior could be found out.

  5. Low-temperature ({<=}200 Degree-Sign C) plasma enhanced atomic layer deposition of dense titanium nitride thin films

    SciTech Connect

    Samal, Nigamananda; Du Hui; Luberoff, Russell; Chetry, Krishna; Bubber, Randhir; Hayes, Alan; Devasahayam, Adrian

    2013-01-15

    Titanium nitride (TiN) has been widely used in the semiconductor industry for its diffusion barrier and seed layer properties. However, it has seen limited adoption in other industries in which low temperature (<200 Degree-Sign C) deposition is a requirement. Examples of applications which require low temperature deposition are seed layers for magnetic materials in the data storage (DS) industry and seed and diffusion barrier layers for through-silicon-vias (TSV) in the MEMS industry. This paper describes a low temperature TiN process with appropriate electrical, chemical, and structural properties based on plasma enhanced atomic layer deposition method that is suitable for the DS and MEMS industries. It uses tetrakis-(dimethylamino)-titanium as an organometallic precursor and hydrogen (H{sub 2}) as co-reactant. This process was developed in a Veeco NEXUS Trade-Mark-Sign chemical vapor deposition tool. The tool uses a substrate rf-biased configuration with a grounded gas shower head. In this paper, the complimentary and self-limiting character of this process is demonstrated. The effects of key processing parameters including temperature, pulse time, and plasma power are investigated in terms of growth rate, stress, crystal morphology, chemical, electrical, and optical properties. Stoichiometric thin films with growth rates of 0.4-0.5 A/cycle were achieved. Low electrical resistivity (<300 {mu}{Omega} cm), high mass density (>4 g/cm{sup 3}), low stress (<250 MPa), and >85% step coverage for aspect ratio of 10:1 were realized. Wet chemical etch data show robust chemical stability of the film. The properties of the film have been optimized to satisfy industrial viability as a Ruthenium (Ru) preseed liner in potential data storage and TSV applications.

  6. Effect of DC glow discharge plasma treatment on PET/TiO(2) thin film surfaces for enhancement of bioactivity.

    PubMed

    Navaneetha Pandiyaraj, K; Selvarajan, V; Rhee, Young Ha; Kim, Hyoung Woo; Pavese, Matteo

    2010-08-01

    In this paper, the surfaces of PET/TiO(2) thin film were modified by DC glow discharge plasma as a function of discharge potentials for improving the bioactivity. The hydrophilicity of the plasma-treated PET/TiO(2) film was measured by contact angle measurement and the surface energy was estimated by using Fowkes method. The structural and chemical composition of the plasma-treated PET/TiO(2) was analysed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Immersion in a simulated body solution (SBF) solution was used to evaluate the bioactivity of the plasma-treated PET/TiO(2) samples in vitro. It was found that the plasma treatment modified the surfaces both in chemical composition and crystallinity which makes surface of the PET/TiO(2) to become more hydrophilic compared with untreated one. Analytical and microstructural investigations of SBF results, showed considerable higher rates of apatite formation on the plasma-treated PET/TiO(2) compared to the untreated films.

  7. Improved understanding and control of magnesium-doped gallium nitride by plasma assisted molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Burnham, Shawn D.

    By an improved understanding of Mg-doped GaN through an exhaustive review of current limitations, increased control over the material was achieved by addressing several of these issues. To address the issues of the memory effect, low sticking coefficient and high vapor pressure of Mg, a new Mg dopant source was implemented, characterized and modeled for p-type doping of GaN. The device enhanced the sticking coefficient of Mg by energizing the outgoing Mg flux, and also allowed the first reported demonstration of an abrupt junction between two non-zero Mg concentrations and a graded Mg-doped GaN film. The significant compensation of Mg acceptors at high dopant concentrations was used advantageously to develop a new ex situ resistivity analysis technique using the energy distributions of SIMS to characterize doping of buried layers. The new technique was used to identify the barrier between conductive and resistive Mg doping for increased Mg concentration, which was then used to optimize Mg-doped GaN. Because Mg doping exhibits a dependence upon the growth regime, a new growth and regime characterization technique was developed using specific RHEED intensity responses to repeat growth conditions. During the development of this technique, a new surface kinetics growth model for III-nitrides was discovered based on DMS observations, which suggests preferential buildup of the metal bilayer before growth begins with an unfamiliar cation-anion exchange process initially upon metal shutter opening. Using the new RHEED growth and regime characterization technique, a new growth technique called metal modulated epitaxy (MME) was developed to increase repeatability, uniformity and smoothness. The MME technique was enhanced with a closed-loop control using real-time feedback from RHEED transients to control shutter transitions. This enhancement, called "smart shuttering," led to improved growth rate and further improvement of surface roughness and grain size, which were

  8. Enhancement of the crystalline Ge film growth by inductively coupled plasma-assisted pulsed DC sputtering.

    PubMed

    Kim, Eunkyeom; Han, Seung-Hee

    2014-11-01

    The effect of pulsed DC sputtering on the crystalline growth of Ge thin film was investigated. Ge thin films were deposited on the glass substrates using ICP-assisted pulsed DC sputtering. The Ge target was sputtered using asymmetric bipolar pulsed DC sputtering system with and without assistance of ICP source. The pulse frequency of 200 Hz and the pulse on time of 500 μsec (duty cycle = 10%) were kept during sputtering process. Crystal structures were studied from X-ray diffraction. The X-ray diffraction patterns clearly showed crystalline film structures. The Ge thin films with randomly oriented crystalline were obtained using pulsed DC sputtering without ICP, whereas they had well aligned (220) orientation crystalline using ICP source. Moreover, the combination of ICP assistance and pulsed DC sputtering enhanced the growth of crystalline Ge thin films without hydrogen and metal by in situ deposition. The structure and lattice of the films were studied from TEM images. The cross-sectional TEM images revealed the deposited Ge films with columnar structure.

  9. Analysis of processes in DC arc plasma torches for spraying that use air as plasma forming gas

    NASA Astrophysics Data System (ADS)

    Frolov, V.; Ivanov, D.; Toropchin, A.

    2014-11-01

    Developed in Saint Petersburg State Polytechnical University technological processes of air-plasma spraying of wear-resistant, regenerating, hardening and decorative coatings used in number of industrial areas are described. The article contains examples of applications of air plasma spraying of coatings as well as results of mathematical modelling of processes in air plasma torches for spraying.

  10. Synergistic damage mechanism of corrosion and cavitation-erosion for plasma ion nitrided 18Cr-8Ni-1.1Mn-0.43C stainless steel in seawater

    NASA Astrophysics Data System (ADS)

    Chong, Sang-Ok; Kim, Seong-Jong

    2017-01-01

    In this work, it was investigated that resistance of combination damages of electrochemical corrosion and cavitation-erosion for plasma ion nitrided 18Cr-8Ni-1.1Mn-0.43C stainless steel at various process temperatures under cavitation environment in seawater. The plasma ion nitriding treatment was performed with a gas mixture ratio of 25% N2 and 75% H2 at a temperature of 623, 673, 723, and 773 K for 10 h, at a chamber pressure of 250 Pa. Expanded austenite (γN) was produced at whole plasma ion nitriding temperatures and especially phases of CrN and γ‧ were observed at 773 K in X-ray diffraction (XRD) analysis. In Tafel analysis, the highest corrosion potential and corrosion current density were analyzed on the untreated (non-cavitation) specimen among specimens under the cavitation condition. Under cavitation environment, the highest corrosion potential and the lowest corrosion current density presented at 673 K. As a result of observation of surface morphologies after anodic polarization experiment under cavitation environment, uniform corrosion was observed on the untreated specimen and plasma ion nitrided specimens, while localized corrosion was shown on the untreated substrate under non-cavitation environment. Furthermore, greater damage depth and severe morphologies were observed at plasma ion nitrided specimens than untreated substrate, whereas the greatest weight loss at 723 K was indicated due to the high pitting corrosion potential and wide passivity potential region.

  11. Effect of process parameters on properties of argon–nitrogen plasma for titanium nitride film deposition

    SciTech Connect

    Saikia, Partha; Kakati, Bharat

    2013-11-15

    In this study, the effect of working pressure and input power on the physical properties and sputtering efficiencies of argon–nitrogen (Ar/N{sub 2}) plasma in direct current magnetron discharge is investigated. The discharge in Ar/N{sub 2} is used to deposit TiN films on high speed steel substrate. The physical plasma parameters are determined by using Langmuir probe and optical emission spectroscopy. On the basis of the different reactions in the gas phase, the variation of plasma parameters and sputtering rate are explained. A prominent change of electron temperature, electron density, ion density, and degree of ionization of Ar is found as a function of working pressure and input power. The results also show that increasing working pressure exerts a negative effect on film deposition rate while increasing input power has a positive impact on the same. To confirm the observed physical properties and evaluate the texture growth as a function of deposition parameters, x-ray diffraction study of deposited TiN films is also done.

  12. Effect of Low Pressure Nitrogen DC Plasma on Optical Properties of Biaxial-Oriented Polypropylene (BOPP), Poly Methyl Methacrylate (PMMA) and Poly Vinyl Chloride (PVC) Films

    NASA Astrophysics Data System (ADS)

    Mortazavi, S. H.; Ghoranneviss, M.; Faryadras, S.

    2012-06-01

    In this paper properties of Biaxial-Oriented Polypropylene, Poly Vinyl Chloride and Poly Methyl Methacrylate samples treated by DC glow discharge of N2 plasma have been investigated by UV-Vis_NIR spectrophotometer. It was found that plasma treatment change chemical structure of polymer surfaces. In addition, absorption coefficient, refractive index and extinction coefficient of all treated samples have been slightly changed.

  13. Study of Martensite Ageing with Plasma Ion Nitriding of Steel C300 Using Design of an Experiment

    NASA Astrophysics Data System (ADS)

    Gezicioglu, Yavuz; Inal, Osman Tugay

    2014-09-01

    Double treatment of maraging steel C300 (nitriding + ageing) is studied using experimental design with a full 32 factorial matrix. After this treatment maximum surface hardness is 1270 HV and for the core it is 553 HV.

  14. Polarity functions' characterization and the mechanism of starch modification by DC glow discharge plasma.

    PubMed

    Khorram, S; Zakerhamidi, M S; Karimzadeh, Z

    2015-01-01

    The wheat starch was investigated, before and after exposure to the argon and oxygen glow discharge plasma, without any added chemical reagents, using a novel media polarity functions method. The mechanisms of modification of starch in plasma discharge irradiation were explained using some methods such as; NMR, IR spectroscopy, Kamlet-Abboud-Taft polarity functions (specific and nonspecific interaction) of modified starch. The starch modification, by plasma treatment, shows valuable changes with plasma gas and relative ionized or active species. Characterizations indicate that argon glow discharge plasma increases crosslink in C-2 site of starch. Also, oxygen plasma discharge irradiation tends to oxidize the OH group in C-6 site of carbonyl group. Furthermore, the reported mechanisms show the highest efficiency, because of the stereo-chemical orientation of active sites of starch and plasma potential of wall in plasma media.

  15. Identification of long non-coding RNAs GAS5, linc0597 and lnc-DC in plasma as novel biomarkers for systemic lupus erythematosus.

    PubMed

    Wu, Guo-Cui; Li, Jun; Leng, Rui-Xue; Li, Xiang-Pei; Li, Xiao-Mei; Wang, De-Guang; Pan, Hai-Feng; Ye, Dong-Qing

    2017-04-04

    Despite increasing evidence that long non-coding RNAs (lncRNAs) widely take part in human diseases, the role of lncRNAs in systemic lupus erythematosus (SLE) is largely unknown. In this study, we performed a two-stage study to explore the plasma levels of five lncRNAs (GAS5, linc0949, linc0597, HOTAIRM1 and lnc-DC) and their potential as SLE biomarkers. Compared with healthy controls, plasma levels of GAS5 and lnc-DC were significantly decreased (P < 0.001 and P = 0.002, respectively) while linc0597 were overexpressed in SLE patients (P < 0.001). When SLE patients were divided into SLE without nephritis and lupus nephritis (LN), the levels of lnc-DC were significantly higher in LN compared with SLE without nephritis (P = 0.018), but no significant difference in levels of GAS5 and linc0597 were found between LN and SLE without nephritis; plasma linc0949 level showed no significant difference in all comparisons. Further evaluation on potential biomarkers showed that GAS5, linc0597 and lnc-DC may specifically identify patients with SLE, the combination of GAS5 and linc0597 provided better diagnostic accuracy; lnc-DC may discriminate LN from SLE without nephritis. In summary, GAS5, linc0597 and lnc-DC in plasma could be potential biomarkers for SLE.

  16. An energy-efficient process for decomposing perfluorooctanoic and perfluorooctane sulfonic acids using dc plasmas generated within gas bubbles

    NASA Astrophysics Data System (ADS)

    Yasuoka, K.; Sasaki, K.; Hayashi, R.

    2011-06-01

    Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) are environmentally harmful and persistent substances. Their decomposition was investigated using dc plasmas generated within small gas bubbles in a solution. The plasma characteristics including discharge voltage, voltage drop in the liquid, plasma shape and the emission spectrum were examined with different gases. The decomposition rate and energy efficiency were evaluated by measuring the concentration of fluoride and sulfate ions released from PFOA/PFOS molecules. The concentration of fluoride ions and energy efficiency in the treatment of a PFOS solution were 17.7 mg l-1 (54.8% of the initial amount of fluorine atoms) and 26 mg kWh-1, respectively, after 240 min of operation. The addition of scavengers of hydroxyl radicals and hydrated electrons showed little effect on the decomposition. The decomposition processes were analyzed with an assumption that positive species reacted with PFOA/PFOS molecules at the boundary of the plasma-solution surface. This type of plasma showed a much higher decomposition energy efficiency compared with energy efficiencies reported in other studies.

  17. Enhanced electron-hole plasma stimulated emission in optically pumped gallium nitride nanopillars

    NASA Astrophysics Data System (ADS)

    Lo, M.-H.; Cheng, Y.-J.; Kuo, H.-C.; Wang, S.-C.

    2011-03-01

    An enhanced stimulated emission was observed in optically pumped GaN nanopillars. The nanopillars were fabricated from an epitaxial wafer by patterned pillar etching followed by crystalline regrowth. Under optical excitation, a strong redshifted stimulated emission peak emerged from a broad spontaneous emission background. The emission is attributed to the electron-hole plasma gain at high carrier density. The emission slope efficiency was greatly enhanced by 20 times compared with a GaN substrate under the same pumping condition. The enhancement is attributed to the better photon and gain interaction from the multiple scattering of photons among nanopillars.

  18. Electron field emission enhancement of carbon nanowalls by plasma surface nitridation

    NASA Astrophysics Data System (ADS)

    Takeuchi, Wakana; Kondo, Hiroki; Obayashi, Tomomi; Hiramatsu, Mineo; Hori, Masaru

    2011-03-01

    Carbon nanowalls (CNWs) are two-dimensional carbon nanostructures consisting of stacked graphene sheets standing vertically on the substrate. The sharp edges of CNWs provide us with opportunities for applications as electron field emitter arrays. The effects of nitrogen plasma (NP) treatment on the surface of CNWs have been investigated in order to improve the electron field emission properties. The electron emission current from the edges of CNWs was drastically increased by the NP treatment. Morphological and chemical changes in the CNWs after the NP treatment were characterized using scanning electron microscopy, Raman spectroscopy, and x-ray photoelectron spectroscopy.

  19. X-ray absorption and photoelectron spectroscopic study of plasma-nitrided SiO{sub 2} film

    SciTech Connect

    Song, H.J.; Shin, H.J.; Chung, Youngsu; Lee, J.C.; Lee, M.K.

    2005-06-01

    Plasma-nitrided SiO{sub 2} thin film has been analyzed by synchrotron-radiation-based x-ray absorption and photoelectron spectroscopies (XAS and XPS). High-resolution N 1s XAS and N 1s, O 1s, and Si 2p XPS spectral changes were obtained for different annealing temperatures. N 1s XPS and XAS spectra show that at room temperature, besides the main species of N[Si(O-){sub 3-x}]{sub 3}, there exist free moleculelike N{sub 2} and HN[Si(O-){sub 3}]{sub 2}, H{sub 2}NSi(O-){sub 3}, and N-Si{sub 2}O species with surface contaminants. The spectral intensities of the N{sub 2} and the HN[Si(O-){sub 3}]{sub 2}, H{sub 2}NSi(O-){sub 3}, and N-Si{sub 2}O species decrease as the annealing temperature increases, and finally the nitrogen exists dominantly in the form of N[Si(O){sub 3}]{sub 3} species above 820 K, indicating out-diffusion of molecular N{sub 2} and structural reconstruction to form a stable structure upon annealing. The Si 2p and O 1s XPS spectra show that Si{sup >4+} 2p peak and O 1s peak appear at 103.7 and 534.0 eV, respectively, which are higher binding energies than those of thermally grown oxynitride films with lower coverage on silicon. Upon annealing the sample, these peaks shift towards lower binding energy; {approx}0.3 eV for Si{sup >4+} and 0.4 eV for O 1s. The causes of the peaks appearance at relatively higher binding energy and the peak shift upon annealing are discussed.

  20. Systematical Study of Reliability Issues in Plasma-Nitrided and Thermally Nitrided Oxides for Advanced Dual-Gate Oxide p-Channel Metal-Oxide-Semiconductor Field-Effect Transistors

    NASA Astrophysics Data System (ADS)

    Lo, Wen-Cheng; Wu, Shien-Yang; Chang, Sun-Jay; Chiang, Mu-Chi; Lin, Chih-Yung; Chao, Tien-Sheng; Chang, Chun-Yen

    2007-03-01

    In this study, we compared the effects of negative-bias temperature instability (NBTI) and hot-carrier injection (HCI) on the core and input/output (I/O) p-channel metal-oxide-semiconductor field-effect transistor (PMOSFET) fabricated using the different gate dielectrics of plasma nitrided oxide (PNO) and thermally nitrided oxide (TNO). The mobility and constant overdrive current of the PMOSFETs fabricated using PNO as a gate oxide material are about 30 and 23% higher than those of the devices fabricated using TNO, respectively. The core PMOSFETs fabricated using PNO show a better NBTI and HCI immunity than those fabricated using TNO owing to the lower nitrogen concentration at the SiO2/Si-substrate interface. However, the I/O PMOSFETs fabricated using PNO show a higher HCI-induced degradation rate because of a higher oxide bulk trap density but a better NBTI than the devices fabricated using TNO at a normal stressed bias due to a low interface trap density.

  1. Effect of the magnetic field on the plasma parameters in the cathode fall region of the DC-glow discharge

    NASA Astrophysics Data System (ADS)

    Hassouba, M. A.

    2001-05-01

    Low-density plasma is generated in a cylindrical DC magnetron discharge tube. Distribution of the magnetic field strengths in the radial and axial directions is drawn. Langmuir probe data are obtained at the edge of the cathode fall region of Ar gas discharge at pressure range from 0.5 to 4.0 torr. In the presence of the magnetic field, values of the electron temperature T_e are smaller than that without magnetic field. While plasma density N_e increases by a factor of two than that without magnetic field. The electron density increases with magnetic field due to electron magnetic confinement. Also, the radial distribution of T_e and N_e in the cathode fall region of the glow discharge is discussed. The magnetic field drift velocity plays an important role to make the radial distribution of T_e and N_e slightly changed.

  2. Determination of dissolved boron in fresh, estuarine, and geothermal waters by d.c. argon-plasma emission spectrometry

    USGS Publications Warehouse

    Ball, J.W.; Thompson, J.M.; Jenne, E.A.

    1978-01-01

    A d.c. argon-plasma emission spectrometer is used to determine dissolved boron in natural (fresh and estuarine) water samples. Concentrations ranged from 0.02 to 250 mg l-1. The emission-concentration function is linear from 0.02 to 1000 mg l-1. Achievement of a relative standard deviation of ??? 3% requires frequent restandardization to offset sensitivity changes. Dilution may be necessary to overcome high and variable electron density caused by differences in alkali-metal content and to avoid quenching of the plasma by high solute concentrations of sodium and other easily ionized elements. The proposed method was tested against a reference method and found to be more sensitive, equally or more precise and accurate, less subject to interferences, with a wider linear analytical range than the carmine method. Analyses of standard reference samples yielded results in all cases within one standard deviation of the means. ?? 1978.

  3. Hysteresis in amplitudes of self-excited oscillations for co-axial electrode-geometry DC glow discharge plasma

    NASA Astrophysics Data System (ADS)

    Kumar, R.; Narayanan, R.; Prasad, Awadhesh

    2014-12-01

    Hysteresis in amplitudes of the self-excited oscillations of the floating potential and discharge current is observed in an unmagnetized co-axial electrode-geometry DC glow discharge plasma system. The nonlinearities of these oscillations are studied using standard dynamical analysis tools. The characterization revealed the transition of low-amplitude high-frequency period-n oscillations to a large amplitude low frequency period-1 oscillations through a chaotic intermediate route. The transition of the low amplitude, high frequency period-n oscillations to chaotic type is observed to be linked to the dynamical change in the plasma system, i.e., after a negative differential resistance (NDR) region, whereas the transition from chaotic to period-1 is observed to be linked to a discharge current threshold.

  4. Optical emission spectroscopy of 50 Hz pulsed dc nitrogen-hydrogen plasma in the presence of active screen cage

    NASA Astrophysics Data System (ADS)

    Saeed, A.; Abrar, M.; Khan, A. W.; Jan, F.; Khan, B. S.; Shah, H. U.; Zaka-ul-Islam, M.; Zakaullah, M.

    2016-05-01

    The N2-H2 plasma gas mixture, generated in a 50 Hz pulsed dc discharge system with active screen cage, is characterized by optical emission spectroscopy (OES), as a function of gas pressure, the fractions of hydrogen and current density. The N2 dissociation degree and N atomic density was measured with actinometery where argon gas is used as actinometer. It was shown that the increase in hydrogen fraction enhances the dissociation of N2, until the maximum of 40%. The excitation temperature is determined from Ar-I emission line intensities by using the simple Boltzmann plot method. The dissociation fraction and excitation temperature is found to increase with hydrogen mixing in nitrogen plasma.

  5. Hysteresis in amplitudes of self-excited oscillations for co-axial electrode-geometry DC glow discharge plasma

    SciTech Connect

    Kumar, R.; Narayanan, R.; Prasad, Awadhesh

    2014-12-15

    Hysteresis in amplitudes of the self-excited oscillations of the floating potential and discharge current is observed in an unmagnetized co-axial electrode-geometry DC glow discharge plasma system. The nonlinearities of these oscillations are studied using standard dynamical analysis tools. The characterization revealed the transition of low-amplitude high-frequency period-n oscillations to a large amplitude low frequency period-1 oscillations through a chaotic intermediate route. The transition of the low amplitude, high frequency period-n oscillations to chaotic type is observed to be linked to the dynamical change in the plasma system, i.e., after a negative differential resistance (NDR) region, whereas the transition from chaotic to period-1 is observed to be linked to a discharge current threshold.

  6. Superconducting niobium titanium nitride thin films deposited by plasma-enhanced atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Yemane, Y. T.; Sowa, M. J.; Zhang, J.; Ju, L.; Deguns, E. W.; Strandwitz, N. C.; Prinz, F. B.; Provine, J.

    2017-09-01

    NbTiN has a variety of superconducting applications, ranging from RF cavities to single-photon detectors. Here, we systematically investigated the plasma-enhanced atomic layer deposition (PEALD) of Nb x Ti{}1-x{{N}} with the organometallic precursors (t-butylimido) tris(diethyamido) niobium(V) and tetrakis (dimethylamido) titanium in conjunction with a remote H2/N2 plasma. Deposited film properties have been studied as a function of the ratio of Nb to Ti precursor pulses within each ALD supercycle. PEALD NbTiN films were characterized with spectroscopic ellipsometry (thickness, optical properties), four point probe (resistivity), x-ray photoelectron spectroscopy (composition), x-ray reflectivity (density and thickness), x-ray diffraction (crystallinity), and superconductivity measurements. The PEALD process has shown distinct advantages over deposition of superconducting films via thermal ALD or sputtering, for example a lower processing temperature and more efficient control of film composition. This control of film composition enabled the tuning of electrical and superconducting properties, such as varying the superconducting critical temperature T C between 6.9 and 13.2 K.

  7. Effects of different plasma species (atomic N, metastable N2*, and ions) on the optical properties of dilute nitride materials grown by plasma-assisted molecular-beam epitaxy

    NASA Astrophysics Data System (ADS)

    Oye, Michael M.; Mattord, Terry J.; Hallock, Gary A.; Bank, Seth R.; Wistey, Mark A.; Reifsnider, Jason M.; Ptak, Aaron J.; Yuen, Homan B.; Harris, James S.; Holmes, Archie L.

    2007-11-01

    This letter studies the effects of atomic N, metastable N2*, and ionic species on the optical properties of dilute nitride materials. Ga0.8In0.2N0.01As0.99 was grown using a 1% N2 in Ar gas mix from an Applied-Epi Unibulb™ rf plasma source. Isonitrogen samples with and without ions were studied using various plasma operating conditions. Optical emission spectrometry was used to characterize relative proportions of different active nitrogen plasma species (atomic N and metastable N2*). Samples grown without ions and with a higher proportion of atomic N resulted in the best overall material quality, although this improvement was observed at high annealing temperatures. At lower annealing temperatures, increased blueshifts were observed for samples grown with a higher proportion of atomic N; however, there was no noticeable influence of ions on blueshift regardless of whether atomic N or metastable N2* was the dominant species present in the plasma. The key implication of this work is that it helps to elucidate a possible reason for some of the contradictory reports in the literature. The ions are not solely responsible for the commonly reported "plasma damage." Furthermore, we demonstrate herein that atomic N and metastable N2* each have different effects on the optical properties of dilute nitride materials grown by plasma-assisted molecular-beam epitaxy.

  8. Frictional and structural characterization of ion-nitrided low and high chromium steels

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1985-01-01

    Low Cr steels AISI 41410, AISI 4340, and high Cr austenitic stainless steels AISI 304, AISI 316 were ion nitrided in a dc glow discharge plasma consisting of a 75 percent H2 - 25 percent N2 mixture. Surface compound layer phases were identified, and compound layer microhardness and diffusion zone microhardness profiles were established. Distinct differences in surface compound layer hardness and diffusion zone profiles were determined between the low and high Cr alloy steels. The high Cr stainless steels after ion nitriding displayed a hard compound layer and an abrupt diffusion zone. The compound layers of the high Cr stainless steels had a columnar structure which accounts for brittleness when layers are exposed to contact stresses. The ion nitrided surfaces of high and low Cr steels displayed a low coefficient of friction with respect to the untreated surfaces when examined in a pin and disk tribotester.

  9. Frictional and structural characterization of ion-nitrided low and high chromium steels

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1985-01-01

    Low Cr steels AISI 41410, AISI 4340, and high Cr austenitic stainless steels AISI 304, AISI 316 were ion nitrided in a dc glow discharge plasma consisting of a 75 percent H2 - 25 percent N2 mixture. Surface compound layer phases were identified, and compound layer microhardness and diffusion zone microhardness profiles were established. Distinct differences in surface compound layer hardness and diffusion zone profiles were determined between the low and high Cr alloy steels. The high Cr stainless steels after ion nitriding displayed a hard compound layer and an abrupt diffusion zone. The compound layers of the high Cr stainless steels had a columnar structure which accounts for brittleness when layers are exposed to contact stresses. The ion nitrided surfaces of high and low Cr steels displayed a low coefficient of friction with respect to the untreated surfaces when examined in a pin and disk tribotester.

  10. Effects of Ti-C:H coating and plasma nitriding treatment on tribological, electrochemical, and biocompatibility properties of AISI 316L.

    PubMed

    Kao, W H; Su, Y L; Horng, J H; Zhang, K X

    2016-08-01

    Ti-C:H coatings were deposited on original, nitrided, and polished-nitrided AISI 316L stainless steel substrates using a closed field unbalanced magnetron sputtering system. Sliding friction wear tests were performed in 0.89 wt.% NaCl solution under a load of 30 N against AISI 316L stainless steel, Si3N4, and Ti6Al4V balls, respectively. The electrochemical properties of the various specimens were investigated by means of corrosion tests performed in 0.89 wt.% NaCl solution at room temperature. Finally, the biocompatibility properties of the specimens were investigated by performing cell culturing experiments using purified mouse leukemic monocyte macrophage cells (Raw264.7). In general, the results showed that plasma nitriding followed by Ti-C:H coating deposition provides an effective means of improving the wear resistance, anti-corrosion properties, and biocompatibility performance of AISI 316L stainless steel. © The Author(s) 2016.

  11. Low-Temperature Plasma-Assisted Atomic Layer Deposition of Silicon Nitride Moisture Permeation Barrier Layers.

    PubMed

    Andringa, Anne-Marije; Perrotta, Alberto; de Peuter, Koen; Knoops, Harm C M; Kessels, Wilhelmus M M; Creatore, Mariadriana

    2015-10-14

    Encapsulation of organic (opto-)electronic devices, such as organic light-emitting diodes (OLEDs), photovoltaic cells, and field-effect transistors, is required to minimize device degradation induced by moisture and oxygen ingress. SiNx moisture permeation barriers have been fabricated using a very recently developed low-temperature plasma-assisted atomic layer deposition (ALD) approach, consisting of half-reactions of the substrate with the precursor SiH2(NH(t)Bu)2 and with N2-fed plasma. The deposited films have been characterized in terms of their refractive index and chemical composition by spectroscopic ellipsometry (SE), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FTIR). The SiNx thin-film refractive index ranges from 1.80 to 1.90 for films deposited at 80 °C up to 200 °C, respectively, and the C, O, and H impurity levels decrease when the deposition temperature increases. The relative open porosity content of the layers has been studied by means of multisolvent ellipsometric porosimetry (EP), adopting three solvents with different kinetic diameters: water (∼0.3 nm), ethanol (∼0.4 nm), and toluene (∼0.6 nm). Irrespective of the deposition temperature, and hence the impurity content in the SiNx films, no uptake of any adsorptive has been observed, pointing to the absence of open pores larger than 0.3 nm in diameter. Instead, multilayer development has been observed, leading to type II isotherms that, according to the IUPAC classification, are characteristic of nonporous layers. The calcium test has been performed in a climate chamber at 20 °C and 50% relative humidity to determine the intrinsic water vapor transmission rate (WVTR) of SiNx barriers deposited at 120 °C. Intrinsic WVTR values in the range of 10(-6) g/m2/day indicate excellent barrier properties for ALD SiNx layers as thin as 10 nm, competing with that of state-of-the-art plasma-enhanced chemical vapor-deposited SiNx layers of a few hundred

  12. Structural evolution of Ti destroyable interlayer in large-size diamond film deposition by DC arc plasma jet

    NASA Astrophysics Data System (ADS)

    Guo, Jianchao; Li, Chengming; Liu, Jinlong; Wei, Junjun; Chen, Liangxian; Hua, Chenyi; Yan, Xiongbo

    2016-05-01

    The addition of titanium (Ti) interlayer was verified to reduce the residual stress of diamond films by self-fracturing and facilitate the harvest of a crack-free free-standing diamond film prepared by direct current (DC) arc plasma jet. In this study, the evolution of the Ti interlayer between large-area diamond film and substrate was studied and modeled in detail. The evolution of the interlayer was found to be relevant to the distribution of the DC arc plasma, which can be divided into three areas (arc center, arc main, and arc edge). The formation rate of titanium carbide (TiC) in the arc main was faster than in the other two areas and resulted in the preferred generation of crack in the diamond film in the arc main during cooling. Sandwich structures were formed along with the growth of TiC until the complete transformation of the Ti interlayer. The interlayer released stress via self-fracture. Avoiding uneven fragile regions that formed locally in the interlayer and achieving cooperatively released stress are crucial for the preparation of large crack-free diamond films.

  13. Catastrophic instabilities of modified DA-DC hybrid surface waves in a semi-bounded plasma system

    NASA Astrophysics Data System (ADS)

    Lee, Myoung-Jae; Jung, Young-Dae

    2016-06-01

    We find the catastrophic instabilities and derive the growth rates for the dust-cyclotron resonance (DCR) and dust-rotation resonance (DRR) modes of the modified dust-acoustic and dust-cyclotron (DA-DC) hybrid surface waves propagating at the plasma-vacuum interface where the plasma is semi-bounded and composed of electrons and rotating dust grains. The effects of magnetic field and dust rotation frequency on the DCR- and DDR-modes are also investigated. We find that the dust rotation frequency enhances the growth rate of DCR-mode and the effect of dust rotation on this resonance mode decreases with an increase of the wave number. We also find that an increase of magnetic field strength enhances the DCR growth rate, especially, for the short wavelength regime. In the case of DRR-mode, the growth rate is found to be decreased less sensitively with an increase of the wave number compared with the case of DCR, but much significantly enhanced by an increase of dust rotation frequency. The DRR growth rate also decreases with an increase of the magnetic field strength, especially in the long wavelength regime. Interestingly, we find that catastrophic instabilities occur for both DCR- and DRR-modes of the modified DA-DC hybrid surface waves when the rotational frequency is close to the dust-cyclotron frequency. Both modes can also be excited catastrophically due to the cooperative interaction between the DCR-mode and the DRR-mode.

  14. Dc to ac field conversion due to leaky-wave excitation in a plasma slab behind an ionization front

    NASA Astrophysics Data System (ADS)

    Kostin, V. A.; Vvedenskii, N. V.

    2015-03-01

    We present a way for generating coherent tunable electromagnetic radiation through dc to ac field conversion by an ionization front. The conversion is caused by the excitation of leaky waves behind the transversely limited ionization front propagating in a uniform electrostatic field. This differs significantly from the well-known dc-to-ac-radiation-converter models which consider Doppler-like frequency conversion by a transversely unlimited ionization front propagating in a spatially periodic electric field. We explore the dispersion properties and excitation of these leaky waves radiated through the transverse plasma boundary at the Cherenkov angle to the direction of propagation of a superluminal ionization front as dependent on the parameters of the plasma produced and on the speed of the ionization front. It is shown that not only the center frequency but also the duration and waveform of the generated pulse may significantly depend on the speed of the ionization front. The results indicate the possibility of using such converters based on planar photoconductive antennas to create sources of microwave and terahertz radiation with controllable waveforms that are transformed from video to radio pulse when the angle of incident ionizing radiation is tuned.

  15. Electron cyclotron resonance plasma deposition of silicon nitride: Effect of very low rf substrate bias

    NASA Astrophysics Data System (ADS)

    Buckle, K. A.; Rodgers, J.; Pastor, K.; Constantine, C.; Johnson, D.

    1992-05-01

    Plasma deposition of SiN on silicon substrates in a microwave (2.45 GHz) electron cyclotron resonance SiH4/N2/He, in the ratio 4/10/10, discharge has been investigated as a function of rf (40 MHz) self-biasing of the sample. Low levels of rf bias (0-10 W) were investigated and are reported in this letter. The effect of bias was measured for the deposited films with respect to refractive index, etch rate in BHF, Si—H bonding, and the intrinsic film stress. All depositions were conducted at or near room temperature to evaluate the effect of the applied rf bias on film density. All parameters examined indicated that low levels of rf bias help prepare a high quality, dense film at very low substrate temperatures.

  16. [Experimental study on the corrosion behavior of a type of oral near β-type titanium alloys modified with double glow plasma nitriding].

    PubMed

    Wen, Ke; Li, Fenglan

    2015-12-01

    To study the electrochemical corrosion performance of a type of biomedical materials near beta titanium alloy(Ti-3Zr-2Sn-3Mo-25Nb, TLM) in artificial saliva before and after nitride changing, and to provide clinical basis for clinical application of titanium alloy TLM. The double glow plasma alloying technology was used to nitride the surface of titanium alloy TLM. The surface properties of the modified layer were observed and tested by optical microscope, scanning electron microscope, glow discharge spectrum analyzer, X-ray diffraction and micro hardness tester. Then, electrochemical measurement system was used to test and compare titanium alloy TLM's electrochemical corrosion in artificial saliva before and after its surface change. Finally, the surface morphology of the original titanium alloy and the modified layer was compared by scanning electron microscope. By the technology of double glow plasma nitriding, the surface of the titanium alloy TLM had been successfully nitrided with a modified layer of 4-5 µm in thickness, uniform and compact. Its main compositions were Ti and Ti(2)N. The Microhardness of modified layer also had been improved from (236.8 ± 5.4) to (871.8 ± 5.2) HV. The self-corrosion potential in electrochemical corrosion tests had been increased from -0.559 V to -0.540 V, while the self- corrosion current density had been reduced from 2.091 × 10(-7) A/cm(2) to 7.188 × 10(-8) A/cm(2). Besides, alternating-current impedance(AC Impedance) had also been increased. With the scanning electron microscope, it's obvious that the diameter of corrosion holes on modified layer were approximately 10 µm. As to the diameter and number of corrosion holes on modified layer, they had been decreased comparing with the original titanium alloy. The type of near beta titanium alloy TLM can construct a nitriding modified layer on its surface. Meanwhile, the performance of its anti- corrosion in artificial saliva has been improved, comparing to the original

  17. Efficiency of plasma density control with dc discharge and magnetic field for different surface types in low pressure hypersonic flow

    NASA Astrophysics Data System (ADS)

    Schweigert, Irina

    2013-09-01

    Recently the problem of communication blackout during reentrant flight still remains unsolved. The spacecrafts enter the upper atmospheric layers with a hypersonic speed and the shock heated air around them becomes weakly ionized. The gas ionization behind the shock front is associative in nature and occurs through chemical reactions between fragments of molecules. The formation of a plasma layer near the surfaces of spacecraft causes serious problems related to the blocking of communication channels with the Earth and other spacecrafts. A promising way of restoring the radio communications is the application of electrical and magnetic fields for controlling the plasma layer parameters. Nevertheless the flux of electrons and ions on the surface charges it that essentially decrease the effect of electro-magnetic control of local plasma density. In Ref. it is shown that there is the way to remove the surface charge using the lateral diode string structures. Based on two dimensional kinetic Particle in cell Monte Carlo collision simulations, we study the possibility of local control the plasma layer parameters near a flat surface of two different types. The gas velocity distribution is set with a model profile. We apply DC voltage up to 4 kV and magnetic field B up to 200 G.

  18. Dust particle circulation and vortices in a dc glow discharge dusty plasma

    NASA Astrophysics Data System (ADS)

    Kish, Ayden; Thomas, Edward

    2016-10-01

    Complex, or dusty, plasmas introduce a new charged species - dust grains of up to a few microns in diameter - to the dynamics of a background plasma discharge. While the size of these dust grains allow us to observe many plasma phenomena macroscopically, their presence also results in the generation of other processes that are unique to dusty plasmas. This presentation reports the observations of a recent study of toroidally-shaped dust clouds in a direct-current Argon plasma discharge. These dusty plasma clouds are formed by placing a conducting ring on a lower electrode while generating the plasma using an upper, biased electrode. Dust particles become suspended in the plasma between the two electrodes and, under the correct pressure and discharge conditions, the toroidally-shaped cloud is formed. This work reports on a variety of experimental configurations used to generate the clouds, measurements of particle flow and rotation using particle image velocimetry (PIV), and initial characterization of the plasma conditions that lead to the formation of these structures. Auburn University Undergraduate Research Fellowship and U.S. Department of Energy Grant Number DE-SC0010485.

  19. Plasma nitriding induced growth of Pt-nanowire arrays as high performance electrocatalysts for fuel cells.

    PubMed

    Du, Shangfeng; Lin, Kaijie; Malladi, Sairam K; Lu, Yaxiang; Sun, Shuhui; Xu, Qiang; Steinberger-Wilckens, Robert; Dong, Hanshan

    2014-09-22

    In this work, we demonstrate an innovative approach, combing a novel active screen plasma (ASP) technique with green chemical synthesis, for a direct fabrication of uniform Pt nanowire arrays on large-area supports. The ASP treatment enables in-situ N-doping and surface modification to the support surface, significantly promoting the uniform growth of tiny Pt nuclei which directs the growth of ultrathin single-crystal Pt nanowire (2.5-3 nm in diameter) arrays, forming a three-dimensional (3D) nano-architecture. Pt nanowire arrays in-situ grown on the large-area gas diffusion layer (GDL) (5 cm(2)) can be directly used as the catalyst electrode in fuel cells. The unique design brings in an extremely thin electrocatalyst layer, facilitating the charge transfer and mass transfer properties, leading to over two times higher power density than the conventional Pt nanoparticle catalyst electrode in real fuel cell environment. Due to the similar challenges faced with other nanostructures and the high availability of ASP for other material surfaces, this work will provide valuable insights and guidance towards the development of other new nano-architectures for various practical applications.

  20. Diffusion bonding of boron nitride on metal substrates by plasma activated sintering (PAS) process

    SciTech Connect

    Yoo, S.; Groza, J.R.; Yamazaki, K.; Sudarshan, T.S.

    1996-05-01

    Ceramic coatings have a considerable potential to be used as thermal barriers and improve corrosion and wear resistance of metallic materials at high temperatures. In particular, BN ceramics are excellent candidates for thermal barrier materials because they have superior corrosion and abrasion resistance, low thermal conductivity and high temperature stability. In general, above 1,273 K ceramics have better strength, creep oxidation resistance than metals or superalloys. It is well known that ceramic coatings are difficult to apply on metal substrates due to the different atomic bonding between ceramic and metals. To provide the expected protection, ceramic coating of metals must provide good interfacial bonding, suitable adherence and interface stability. These may be achieved by different processing approaches such as: diffusion bonding under pressure application, thermal spray or mechanical bonding. An alternative method may be sinter-bonding using P/M techniques such as hot isostatic pressing (HIP) when simultaneous sintering of ceramic powders and bonding onto the metal substrate can take place. The purpose of this present work is to verify the potential of the plasma assisted sintering (PAS) process to develop a good diffusion bonding between a BN ceramic layer and the metal substrate while sintering the ceramic layer. In contrast to HIP techniques, sintering and coating in PAS can be completed in a very short time (minutes as compared to hours) concurrent with an observed (not yet demonstrated) capability of particle surface cleaning by removing surface oxides or trapped gases.

  1. Plasma nitriding induced growth of Pt-nanowire arrays as high performance electrocatalysts for fuel cells

    PubMed Central

    Du, Shangfeng; Lin, Kaijie; Malladi, Sairam K.; Lu, Yaxiang; Sun, Shuhui; Xu, Qiang; Steinberger-Wilckens, Robert; Dong, Hanshan

    2014-01-01

    In this work, we demonstrate an innovative approach, combing a novel active screen plasma (ASP) technique with green chemical synthesis, for a direct fabrication of uniform Pt nanowire arrays on large-area supports. The ASP treatment enables in-situ N-doping and surface modification to the support surface, significantly promoting the uniform growth of tiny Pt nuclei which directs the growth of ultrathin single-crystal Pt nanowire (2.5–3 nm in diameter) arrays, forming a three-dimensional (3D) nano-architecture. Pt nanowire arrays in-situ grown on the large-area gas diffusion layer (GDL) (5 cm2) can be directly used as the catalyst electrode in fuel cells. The unique design brings in an extremely thin electrocatalyst layer, facilitating the charge transfer and mass transfer properties, leading to over two times higher power density than the conventional Pt nanoparticle catalyst electrode in real fuel cell environment. Due to the similar challenges faced with other nanostructures and the high availability of ASP for other material surfaces, this work will provide valuable insights and guidance towards the development of other new nano-architectures for various practical applications. PMID:25241800

  2. Plasma nitriding induced growth of Pt-nanowire arrays as high performance electrocatalysts for fuel cells

    NASA Astrophysics Data System (ADS)

    Du, Shangfeng; Lin, Kaijie; Malladi, Sairam K.; Lu, Yaxiang; Sun, Shuhui; Xu, Qiang; Steinberger-Wilckens, Robert; Dong, Hanshan

    2014-09-01

    In this work, we demonstrate an innovative approach, combing a novel active screen plasma (ASP) technique with green chemical synthesis, for a direct fabrication of uniform Pt nanowire arrays on large-area supports. The ASP treatment enables in-situ N-doping and surface modification to the support surface, significantly promoting the uniform growth of tiny Pt nuclei which directs the growth of ultrathin single-crystal Pt nanowire (2.5-3 nm in diameter) arrays, forming a three-dimensional (3D) nano-architecture. Pt nanowire arrays in-situ grown on the large-area gas diffusion layer (GDL) (5 cm2) can be directly used as the catalyst electrode in fuel cells. The unique design brings in an extremely thin electrocatalyst layer, facilitating the charge transfer and mass transfer properties, leading to over two times higher power density than the conventional Pt nanoparticle catalyst electrode in real fuel cell environment. Due to the similar challenges faced with other nanostructures and the high availability of ASP for other material surfaces, this work will provide valuable insights and guidance towards the development of other new nano-architectures for various practical applications.

  3. Development of metal nanocluster ion source based on dc magnetron plasma sputtering at room temperature

    NASA Astrophysics Data System (ADS)

    Majumdar, Abhijit; Köpp, Daniel; Ganeva, Marina; Datta, Debasish; Bhattacharyya, Satyaranjan; Hippler, Rainer

    2009-09-01

    A simple and cost effective nanocluster ion source for the deposition of size selected metal nanocluster has been developed based on the dc magnetron discharge (including pulsed dc discharge). The most important and interesting feature of this cluster source is that it is working at room temperature, cooled by chilled water during the experiment. There is no extraction unit in this device and the cluster streams flow only due to the pressure gradient from source chamber to substrate via quadrupole mass filter. It has provision of multiple substrate holders in the deposition chamber, which can be controlled manually. The facility consists of quadrupole mass filter (QMF 200), which can select masses in the range of 2-125 000 atoms depending on the target materials, with a constant mass resolution (M /ΔM˜25). The dc magnetron discharge at a power of about 130 W with Ar as feed/buffer gas was used to produce the Cu nanocluster in an aggregation tube and deposited on Si (100) wafer temperature.

  4. Development of metal nanocluster ion source based on dc magnetron plasma sputtering at room temperature.

    PubMed

    Majumdar, Abhijit; Köpp, Daniel; Ganeva, Marina; Datta, Debasish; Bhattacharyya, Satyaranjan; Hippler, Rainer

    2009-09-01

    A simple and cost effective nanocluster ion source for the deposition of size selected metal nanocluster has been developed based on the dc magnetron discharge (including pulsed dc discharge). The most important and interesting feature of this cluster source is that it is working at room temperature, cooled by chilled water during the experiment. There is no extraction unit in this device and the cluster streams flow only due to the pressure gradient from source chamber to substrate via quadrupole mass filter. It has provision of multiple substrate holders in the deposition chamber, which can be controlled manually. The facility consists of quadrupole mass filter (QMF 200), which can select masses in the range of 2-125 000 atoms depending on the target materials, with a constant mass resolution (M/DeltaM approximately 25). The dc magnetron discharge at a power of about 130 W with Ar as feed/buffer gas was used to produce the Cu nanocluster in an aggregation tube and deposited on Si (100) wafer temperature.

  5. Structure of the local environment of titanium atoms in multicomponent nitride coatings produced by plasma-ion techniques

    NASA Astrophysics Data System (ADS)

    Krysina, O. V.; Timchenko, N. A.; Koval, N. N.; Zubavichus, Ya V.

    2016-01-01

    An experiment was performed to examine the X-ray Absorption Near-Edge Structure (XANES) and the Extended X-ray Absorption Fine Structure (EXAFS) near the K-edge of titanium in nanocrystalline titanium nitride coatings containing additives of copper, silicon, and aluminum. Using the observation data, the structure parameters of the local environment of titanium atoms have been estimated for the coatings. According to crystallographic data, the Ti-N distance in the bulk phase of titanium nitride is 2.12 Å and the Ti-Ti distance is 3.0 Å. Nearly these values have been obtained for the respective parameters of the coatings. The presence of copper as an additive in a TiN coating increases the Ti-N distance inappreciably compared to that estimated for titanium nitride, whereas addition of silicon decreases the bond distance. It has been revealed that the copper and silicon atoms in Ti-Cu-N and Ti-Si-N coatings do not enter into the crystallographic phase of titanium nitride and do not form bonds with titanium and nitrogen, whereas the aluminum atoms in Ti-Al-N coatings form intermetallic phases with titanium and nitride phases.

  6. Numerical and experimental study on a pulsed-dc plasma jet

    NASA Astrophysics Data System (ADS)

    Liu, X. Y.; Pei, X. K.; Lu, X. P.; Liu, D. W.

    2014-06-01

    A numerical and experimental study of plasma jet propagation in a low-temperature, atmospheric-pressure, helium jet in ambient air is presented. A self-consistent, multi-species, two-dimensional axially symmetric plasma model with detailed finite-rate chemistry of helium-air mixture composition is used to provide insights into the propagation of the plasma jet. The obtained simulation results suggest that the sheath forms near the dielectric tube inner surface and shields the plasma channel from the tube surface. The strong electric field at the edge of the dielectric field enhances the ionization in the air mixing layer; therefore, the streamer head becomes ring-shaped when the streamer runs out of the tube. The avalanche-to-streamer transition is the main mechanism of streamer advancement. Penning ionization dominates the ionization reactions and increases the electrical conductivity of the plasma channel. The simulation results are supported by experimental observations under similar discharge conditions.

  7. Plasticity and ab initio characterizations on Fe 4N produced on the surface of nanocrystallized 18Ni-maraging steel plasma nitrided at lower temperature

    NASA Astrophysics Data System (ADS)

    Yan, M. F.; Wu, Y. Q.; Liu, R. L.

    2009-08-01

    18Ni-maraging steel has been entirely nanocrystallized by a series of processes including solution treatment, hot-rolling deformation, cold-drawn deformation and direct electric heating. The plasma nitriding of nanocrystallized 18Ni-maraging steel was carried out at 410 °C for 3 h and 6 h in a mixture gas of 20% N 2 + 80% H 2 with a pressure of 400 Pa. The surface phase constructions and nitrogen concentration profile in surface layer were analyzed using an X-ray diffractometer (XRD) and the glow discharge spectrometry (GDS), respectively. The results show that an about 2 μm thick compound layer (mono-phase γ'-Fe 4N) can be produced on the top of the surface layer of nanocrystallized 18Ni-maraging steel plasma nitrided at 410 °C for 6 h. The measured hardness value of the nitrided surface is 11.6 GPa. More importantly, the γ'-Fe 4N phase has better plasticity, i.e., its plastic deformation energy calculated from the load-displacement curve obtained by nano-indentation tester is close to that of nanocrystallized 18Ni-maraging steel. Additionally, the mechanical properties of γ'-Fe 4N phase were also characterized by first-principles calculations. The calculated results indicate that the hardness value and the ratio of bulk to shear modulus ( B/ G) of the γ'-Fe 4N phase are 10.15 GPa and 3.12 (>1.75), respectively. This demonstrates that the γ'-Fe 4N phase has higher hardness and better ductility.

  8. Low sheet resistance titanium nitride films by low-temperature plasma-enhanced atomic layer deposition using design of experiments methodology

    SciTech Connect

    Burke, Micheal Blake, Alan; Povey, Ian M.; Schmidt, Michael; Petkov, Nikolay; Carolan, Patrick; Quinn, Aidan J.

    2014-05-15

    A design of experiments methodology was used to optimize the sheet resistance of titanium nitride (TiN) films produced by plasma-enhanced atomic layer deposition (PE-ALD) using a tetrakis(dimethylamino)titanium precursor in a N{sub 2}/H{sub 2} plasma at low temperature (250 °C). At fixed chamber pressure (300 mTorr) and plasma power (300 W), the plasma duration and N{sub 2} flow rate were the most significant factors. The lowest sheet resistance values (163 Ω/sq. for a 20 nm TiN film) were obtained using plasma durations ∼40 s, N{sub 2} flow rates >60 standard cubic centimeters per minute, and purge times ∼60 s. Time of flight secondary ion mass spectroscopy data revealed reduced levels of carbon contaminants in the TiN films with lowest sheet resistance (163 Ω/sq.), compared to films with higher sheet resistance (400–600 Ω/sq.) while transmission electron microscopy data showed a higher density of nanocrystallites in the low-resistance films. Further significant reductions in sheet resistance, from 163 Ω/sq. to 70 Ω/sq. for a 20 nm TiN film (corresponding resistivity ∼145 μΩ·cm), were achieved by addition of a postcycle Ar/N{sub 2} plasma step in the PE-ALD process.

  9. Enhanced thermal stability of Ti/TiO2/n-Ge contacts through plasma nitridation of TiO2 interfacial layer

    NASA Astrophysics Data System (ADS)

    Biswas, Dipankar; Biswas, Jayeeta; Ghosh, Sayantan; Wood, Bingxi; Lodha, Saurabh

    2017-01-01

    This work demonstrates a solution to the problem of increase in Schottky barrier height ( ϕ B ) with thermal annealing (thermal instability) in unpinned (low ϕ B ) Ti/Ti O 2 /n-Ge metal-interfacial layer (IL)-semiconductor (MIS) contacts through plasma nitridation of the Ti O 2 layer. Unlike TiO2, unpinned ( ϕ B = 0.09 eV) Ti O x N y contacts are thermally stable for anneals up to 30 min at 400 °C. The thermal stability improves with increasing nitrogen concentration ([N], 2.5-9.5%) and is independent of thickness (2-5 nm) for [N] = 9.5%. Additionally, the plasma nitridation process is shown to increase the oxygen vacancy concentration (n-type doping) and reduce the ϕ B dependence on Ti O x N y thickness in unannealed Ti O x N y contacts. Enhanced thermal stability is attributed to the incorporated nitrogen acting as a diffusion barrier that prevents contact pinning through reduction of the TiO2 layer by contact metal during the anneal, as well as preserves the amorphous nature of the IL along with its fixed charge and interfacial dipoles that contribute to ϕ B reduction.

  10. Streptococci biofilm decontamination on teeth by low-temperature air plasma of dc corona discharges

    NASA Astrophysics Data System (ADS)

    Kovalóvá, Z.; Zahoran, M.; Zahoranová, A.; Machala, Z.

    2014-06-01

    Non-thermal plasmas of atmospheric pressure air direct current corona discharges were investigated for potential applications in dental medicine. The objective of this ex vivo study was to apply cold plasmas for the decontamination of Streptococci biofilm grown on extracted human teeth, and to estimate their antimicrobial efficiency and the plasma's impact on the enamel and dentine of the treated tooth surfaces. The results show that both positive streamer and negative Trichel pulse coronas can reduce bacterial population in the biofilm by up to 3 logs in a 10 min exposure time. This bactericidal effect can be reached faster (within 5 min) by electrostatic spraying of water through the discharge onto the treated tooth surface. Examination of the tooth surface after plasma exposure by infrared spectroscopy and scanning electron microscopy did not show any significant alteration in the tooth material composition or the tooth surface structures.

  11. Characterization of DC magnetron plasma in Ar/Kr/N2 mixture during deposition of (Cr,Al)N coating

    NASA Astrophysics Data System (ADS)

    Bobzin, K.; Bagcivan, N.; Theiß, S.; Brugnara, R.; Bibinov, N.; Awakowicz, P.

    2017-02-01

    Reactive sputter deposition of (Cr,Al)N coatings in DC magnetron plasmas containing Ar/Kr/N2 mixtures is characterized by applying a combination of voltage–current measurement, optical emission spectroscopy (OES) and numerical simulation. Theoretical and experimental methods supplement each other and their combination permits us to obtain the most reliable information about the processes by physical vapor deposition. Gas temperature (T g) and plasma parameters, namely electron density n e and electron temperature T e are determined by spatial resolved measurements of molecular nitrogen photoemission. Steady-state densities of Cr and Al atoms are measured using OES. The sputtering of Cr and Al atoms is simulated using the TRIDYN code, measured electric current and applied voltage. Transport of sputtered atoms through the plasma volume is simulated by adopting a Monte-Carlo code. In order to quantify the ‘poisoning’ of the target surface with nitrogen, simulated steady state densities of Al and Cr atoms at different states of poisoning and at different distances from the target are compared with the measured densities. In addition, simulated fluxes of Cr and Al atoms to the substrate are compared with the measured deposition rates of the (Cr,Al)N coating.

  12. Fabrication of Ta2O5/GeNx gate insulator stack for Ge metal-insulator-semiconductor structures by electron-cyclotron-resonance plasma nitridation and sputtering deposition techniques

    NASA Astrophysics Data System (ADS)

    Otani, Yohei; Itayama, Yasuhiro; Tanaka, Takuo; Fukuda, Yukio; Toyota, Hiroshi; Ono, Toshiro; Mitsui, Minoru; Nakagawa, Kiyokazu

    2007-04-01

    The authors have fabricated germanium (Ge) metal-insulator-semiconductor (MIS) structures with a 7-nm-thick tantalum pentaoxide (Ta2O5)/2-nm-thick germanium nitride (GeNx) gate insulator stack by electron-cyclotron-resonance plasma nitridation and sputtering deposition. They found that pure GeNx ultrathin layers can be formed by the direct plasma nitridation of the Ge surface without substrate heating. X-ray photoelectron spectroscopy revealed no oxidation of the GeNx layer after the Ta2O5 sputtering deposition. The fabricated MIS capacitor with a capacitance equivalent thickness of 4.3nm showed excellent leakage current characteristics. The interface trap density obtained by the modified conductance method was 4×1011cm-2eV-1 at the midgap.

  13. Catastrophic instabilities of modified DA-DC hybrid surface waves in a semi-bounded plasma system

    SciTech Connect

    Lee, Myoung-Jae; Jung, Young-Dae

    2016-06-15

    We find the catastrophic instabilities and derive the growth rates for the dust-cyclotron resonance (DCR) and dust-rotation resonance (DRR) modes of the modified dust-acoustic and dust-cyclotron (DA-DC) hybrid surface waves propagating at the plasma–vacuum interface where the plasma is semi-bounded and composed of electrons and rotating dust grains. The effects of magnetic field and dust rotation frequency on the DCR- and DDR-modes are also investigated. We find that the dust rotation frequency enhances the growth rate of DCR-mode and the effect of dust rotation on this resonance mode decreases with an increase of the wave number. We also find that an increase of magnetic field strength enhances the DCR growth rate, especially, for the short wavelength regime. In the case of DRR-mode, the growth rate is found to be decreased less sensitively with an increase of the wave number compared with the case of DCR, but much significantly enhanced by an increase of dust rotation frequency. The DRR growth rate also decreases with an increase of the magnetic field strength, especially in the long wavelength regime. Interestingly, we find that catastrophic instabilities occur for both DCR- and DRR-modes of the modified DA-DC hybrid surface waves when the rotational frequency is close to the dust-cyclotron frequency. Both modes can also be excited catastrophically due to the cooperative interaction between the DCR-mode and the DRR-mode.

  14. Flexible reduced graphene oxide supercapacitor fabricated using a nitrogen dc-pulse atmospheric-pressure plasma jet

    NASA Astrophysics Data System (ADS)

    Yang, Cheng-Han; Kuok, Fei-Hong; Liao, Chen-Yu; Wan, Ting-Hao; Chen, Chieh-Wen; Hsu, Cheng-Che; Cheng, I.-Chun; Chen, Jian-Zhang

    2017-02-01

    We use a nitrogen dc-pulse atmospheric-pressure plasma jet to fabricate a flexible reduced graphene oxide (rGO) supercapacitor with polyvinyl alcohol (PVA)/sulfuric acid (H2SO4) gel electrolyte. An areal capacitance of 47.03 mF · cm-2 (evaluated using cyclic voltammetry (CV) under a potential scan rate of 2 mV · s-1) is achieved. The supercapacitor can be operated without apparent degradation under bending with a bending radius of 0.55 cm. After a 1000 cycle CV stability test, the capacitance retention rate is 100% when flat and is 98.6% under bending (bending radius  =  0.55 cm), indicating promising stability of the APPJ-processed flexible supercapacitor.

  15. The use of ion chromatography-dc plasma atomic emission spectrometry for the speciation of trace metals

    SciTech Connect

    Urasa, I.T.

    1991-09-20

    The original objects of this research program were: to interface d.c. plasma atomic emission spectrometer with an ion chromatograph; to characterize and optimize the combined systems for application in the speciation of metals in aqueous solutions; to use this system in the study of the solution chemistry of various metals; and to find ways in which the measurement sensitivity of the method can be enhanced, thereby allowing the detection of metal species at low ppb concentration levels. This approach has been used to study the chemistry of and speciate several elements in solution including: arsenic, chromium, iron, manganese, nickel phosphorus, platinum, selenium, and vanadium. During the course of this research, we have found that the solution chemistry of the elements studied and the speciation data obtained can vary considerably depending on the solution, and the chromatographic conditions employed. The speciation of chromium, iron, and vanadium was found to be highly influenced by the acidity of the sample. The element selective nature of the d.c. plasma detector allows these changes to be monitored, thereby providing quantitative information on the new moieties formed. New approaches are being developed including the use of chelating ligands as preconcentration agents for purposes of reducing further the detection limits of the elements of interest and to improve the overall element speciation scheme. New thrusts are being directed towards the employment of post-column derivatization method coupled with colorimetric measurements to detect and quantify metal species eluting from the chromatographic column. The influence of sample acidity on these investigations will be carefully evaluated. These new thrusts are described in the accompanying Project Renewal Proposal.

  16. Plasma surface treatment to improve surface charge accumulation and dissipation of epoxy resin exposed to DC and nanosecond-pulse voltages

    NASA Astrophysics Data System (ADS)

    Zhang, Cheng; Lin, Haofan; Zhang, Shuai; Xie, Qin; Ren, Chengyan; Shao, Tao

    2017-10-01

    In this paper, deposition by non-thermal plasma is used as a surface modification technique to change the surface characteristics of epoxy resin exposed to DC and nanosecond-pulse voltages. The corresponding surface characteristics in both cases of DC and nanosecond-pulse voltages before and after the modification are compared and investigated. The measurement of the surface potential provides the surface charge distribution, which is used to show the accumulation and dissipation process of the surface charges. Morphology observations, chemical composition and electrical parameters measurements are used to evaluate the treatment effects. The experimental results show that, before the plasma treatment, the accumulated surface charges in the case of the DC voltage are more than that in the case of the nanosecond-pulse voltage. Moreover, the decay rate of the surface charges for the DC voltage is higher than that for the nanosecond-pulse voltage. However, the decay rate is no more than 41% after 1800 s for both types of voltages. After the plasma treatment, the maximum surface potentials decrease to 57.33% and 32.57% of their values before treatment for the DC and nanosecond-pulse voltages, respectively, indicating a decrease in the accumulated surface charges. The decay rate exceeds 90% for both types of voltages. These changes are mainly attributed to a change in the surface nanostructure, an increase in conductivity, and a decrease in the depth of energy level.

  17. Pressure and arc voltage coupling in dc plasma torches: Identification and extraction of oscillation modes

    SciTech Connect

    Rat, V.; Coudert, J. F.

    2010-08-15

    This work is devoted to the instabilities occurring in a plasma torch, such as those found in plasma spraying. These instabilities are responsible for a lack of reproducibility of coatings properties, especially in the case of suspension plasma spraying that is an innovative way to obtain thin coatings of submicron-sized particles. Strong Helmholtz oscillations are highlighted in the plasma flow and it is demonstrated that they overlap with different acoustic modes in addition with the more commonly admitted ''restrike'' mode, the later being due to rearcing events in the arc region. The instabilities occur in the arc voltage but it is experimentally shown in this paper that the pressure within the torch body presents the same kind of instabilities. Besides, a numerical filtering technique has been adapted to isolate the different instability components. The operating parameters of the plasma torch were varied in order to highlight their influence on the amplitude of the different modes, both for the arc voltage and the pressure.

  18. Interaction of DC Microhollow Cathode Discharge Plasma Micro Jet with Liquid Media

    NASA Astrophysics Data System (ADS)

    Zhu, Weidong; Lopez, Jose; Becker, Kurt

    2008-10-01

    There have been different approaches in studying the interaction between plasma and liquid, such as sustained plasmas in contact with liquids and pulsed electric discharge in liquids. Recently, we have discovered that stable plasma can be sustained within a gas cavity maintained inside liquid media. A prototype device with key dimensions in sub-millimeter range were operated successfully in de-ionized water and turbo molecular pump oil with ambient air, pure nitrogen or pure oxygen used as the operating gas. Hydrogen Peroxide production in de-ionized water with ambient air as the working gas is estimated to be about 80 mg/L after 15 minutes plasma jet-water interaction while energy consumption is only about 8-10 W. With the radicals readily generated and directly introduced into the liquid media, it could lead to applications such as in-liquid bio-waste treatment, bio-rich liquid modification, in-situ monitoring/sensing, and filtration of by-products from VOC treatment by plasma.

  19. Initial Results of DC Electric Fields, Associated Plasma Drifts, Magnetic Fields, and Plasma Waves Observed on the C/NOFS Satellite

    NASA Technical Reports Server (NTRS)

    Pfaff, R.; Freudenreich, H.; Bromund, K.; Klenzing, J.; Rowland, D.; Maynard, N.

    2010-01-01

    Initial results are presented from the Vector Electric Field Investigation (VEFI) on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite, a mission designed to understand, model, and forecast the presence of equatorial ionospheric irregularities. The VEFI instrument includes a vector DC electric field detector, a fixed-bias Langmuir probe operating in the ion saturation regime, a flux gate magnetometer, an optical lightning detector, and associated electronics including a burst memory. Compared to data obtained during more active solar conditions, the ambient DC electric fields and their associated E x B drifts are variable and somewhat weak, typically < 1 mV/m. Although average drift directions show similarities to those previously reported, eastward/outward during day and westward/downward at night, this pattern varies significantly with longitude and is not always present. Daytime vertical drifts near the magnetic equator are largest after sunrise, with smaller average velocities after noon. Little or no pre-reversal enhancement in the vertical drift near sunset is observed, attributable to the solar minimum conditions creating a much reduced neutral dynamo at the satellite altitude. The nighttime ionosphere is characterized by larger amplitude, structured electric fields, even where the plasma density appears nearly quiescent. Data from successive orbits reveal that the vertical drifts and plasma density are both clearly organized with longitude. The spread-F density depletions and corresponding electric fields that have been detected thus far have displayed a preponderance to appear between midnight and dawn. Associated with the narrow plasma depletions that are detected are broad spectra of electric field and plasma density irregularities for which a full vector set of measurements is available for detailed study. Finally, the data set includes a wide range of ELF/VLF/HF oscillations corresponding to a variety of plasma waves

  20. Experimental analysis on the nonlinear behavior of DC barrier discharge plasmas

    NASA Astrophysics Data System (ADS)

    Dogan, Mansuroglu; Ilker Umit, Uzun-Kaymak

    2017-01-01

    Nonlinear behavior of glow discharge plasmas is experimentally investigated. The glow is generated between a barrier semiconductor electrode, Chromium doped namely Gallium Arsenide (GaAs:Cr), as a cathode and an Indium-Tin Oxide (ITO) coated glass electrode as an anode, in reverse bias. The planar nature of electrodes provides symmetry in spatial geometry. The discharge behaves oscillatory in the time domain, with single and sometimes multi-periodicities in plasma current and voltage characteristics. In this paper, harmonic frequency generation and transition to chaotic behavior is investigated. The observed current-voltage characteristics of the discharge are discussed in detail.

  1. Determination of trace impurities in boron nitride by graphite furnace atomic absorption spectrometry and electrothermal vaporization inductively coupled plasma optical emission spectrometry using solid sampling

    NASA Astrophysics Data System (ADS)

    Barth, P.; Hassler, J.; Kudrik, I.; Krivan, V.

    2007-09-01

    Two digestion-free methods for trace analysis of boron nitride based on graphite furnace atomic absorption spectrometry (GFAAS) and electrothermal vaporization inductively coupled plasma spectrometry optical emission (ETV-ICP-OES) using direct solid sampling have been developed and applied to the determination of Al, Ca, Cr, Cu, Fe, Mg, Mn, Si, Ti and Zr in four boron nitride materials in concentration intervals of 1-23, 54-735, 0.05-21, 0.005-1.3, 1.6-112, 4.5-20, 0.03-1.8, 6-46, 38-170 and 0.4-2.3 μg g - 1 , respectively. At optimized experimental conditions, with both methods, effective in-situ analyte/matrix separation was achieved and calibration could be performed using calibration curves measured with aqueous standard solutions. In solid sampling GFAAS, before sampling, the platform was covered with graphite powder and, for determination of Si, also the Pd/Mg(NO 3) 2 modifier was used. In the determination of all analyte elements by solid sampling ETV-ICP-OES, Freon R12 was added to argon carrier gas. For solid sampling GFAAS and ETV-ICP-OES, the achievable limits of detection were within 5 (Cu)-130 (Si) ng g - 1 and 8 (Cu)-200 (Si) ng g - 1 , respectively. The results obtained by these two methods for four boron nitride materials of different purity grades are compared each with the other and with those obtained in analysis of digests by ICP-OES. The performance of the two solid sampling methods is compared and discussed.

  2. Chemical state of nitrogen in a high nitrogen face-centered-cubic phase formed on plasma source ion nitrided austenitic stainless steel

    SciTech Connect

    Lei, M.K.; Zhu, X.M.

    2004-09-01

    A single high nitrogen face-centered-cubic phase ({gamma}{sub N}) was formed on the plasma source ion nitrided 1Cr18Ni9Ti (18-8 type) austenitic stainless steel. Auger electron spectroscopy and x-ray photoelectron spectroscopy, in conjunction with ion beam sputtering, were used to determine the chemical composition and bonding of nitrogen in the {gamma}{sub N} phase. The chemical composition of the {gamma}{sub N} phase was shown as a formula with atomic fraction (Fe{sub 0.60},Cr{sub 0.22},Ni{sub 0.18}){sub 2}N. The {gamma}{sub N} phase possessed weaker Cr-N ionic-type bonds and stronger Fe-N ionic-type bonds, compared with the stoichiometric nitrides. The Cr 2p{sub 3sol2} binding energy was 1.1 eV lower than that of CrN and Cr{sub 2}N phases (at 575.5 eV). The chemical shift of the Fe-N bonding compared with the Fe-Fe bonding was nearly 2.1 eV. The N 1s binding energies showed that the nitrogen was in the chemical state with iron (at 396.6 eV) and chromium (at 397.7 eV). All the chromium appeared to be in the Cr-N bond. A part of iron was also observed in the nitride state, and all the nickel was contained in the metallic state.

  3. Spectroscopic investigation of direct current (DC) plasma electrolytic oxidation of zirconium in citric acid.

    PubMed

    Stojadinović, Stevan; Radić-Perić, Jelena; Vasilić, Rastko; Perić, Miljenko

    2014-01-01

    Plasma electrolytic oxidation of zirconium in citric acid was investigated using optical spectroscopy. A rich emission spectrum consisting of about 360 zirconium and 170 oxygen atomic and ionic lines was identified in the spectral regions 313-320, 340-516, and 626-640 nm. It was shown that the remaining features observed in the spectrum could be ascribed to various molecular species, which involve zirconium, oxygen, hydrogen, and carbon. The temperature of the plasma core (T = 7500 ± 1000 K) was determined using measured Zr line intensities, and the temperature of peripheral plasma zone (T = 2800 ± 500 K) was estimated from the intensity distribution within a part of an OH spectrum. The composition of the plasma containing zirconium, oxygen, and hydrogen, under assumption of local thermal equilibrium, was calculated in the temperature range up to 12,000 K and for pressure of 10(5) and 10(7) Pa, in order to explain the appearance of the observed spectral features.

  4. Al-doped zinc oxide films deposited by simultaneous rf and dc excitation of a magnetron plasma: Relationships between plasma parameters and structural and electrical film properties

    NASA Astrophysics Data System (ADS)

    Cebulla, R.; Wendt, R.; Ellmer, K.

    1998-01-01

    A new technique of the simultaneous excitation of a magnetron sputtering discharge by rf and dc was used for the deposition of undoped ZnO- and Al-doped ZnO (ZnO:Al) films. By this technique, it was possible to change the ion-to-neutral ratio ji/jn on the substrates during the film growth by more than a factor of ten, which was revealed by plasma monitor and Langmuir probe measurements. While for a pure dc discharge the ions impinging onto a floating substrate have energies of about Ei≈17 eV, the rf discharge is characterized by Ar-ion energies of about 35 eV. Furthermore, the ion current density for the rf excitation is higher by a factor of about five, which is caused by the higher plasma density in front of the substrate. This leads to a much higher ion-to-neutral ratio ji/jn on the growing film in the case of the rf discharge, which strongly influences the structural and electrical properties of the ZnO(:Al) films. The rf-grown films exhibit about the three times lower specific resistances (ρ≈6×10-4 Ω cm), due to lower mechanical stress, leading to higher charge carrier concentrations and mobilities. Undoped ZnO films exhibited the largest compressive stress values up to 2.8 GPa. The aluminium-doped films have a better (001) texture and larger grains (dg≈38 nm), which can be attributed to the beneficial role of Al as a surfactant. The better crystalline film quality of the ZnO:Al films is the reason for the much lower compressive stress of <0.5 GPa in these layers.

  5. Propagation characteristics of dust-acoustic waves in presence of a floating cylindrical object in the DC discharge plasma

    NASA Astrophysics Data System (ADS)

    Choudhary, Mangilal; Mukherjee, S.; Bandyopadhyay, P.

    2016-08-01

    The experimental observation of the self-excited dust acoustic waves (DAWs) and its propagation characteristics in the absence and presence of a floating cylindrical object is investigated. The experiments are carried out in a direct current (DC) glow discharge dusty plasma in a background of argon gas. Dust particles are found levitated at the interface of plasma and cathode sheath region. The DAWs are spontaneously excited in the dust medium and found to propagate in the direction of ion drift (along the gravity) above a threshold discharge current at low pressure. Excitation of such a low frequency wave is a result of the ion-dust streaming instability in the dust cloud. Characteristics of the propagating dust acoustic wave get modified in the presence of a floating cylindrical object of radius larger than that of the dust Debye length. Instead of propagation in the vertical direction, the DAWs are found to propagate obliquely in the presence of the floating object (kept either vertically or horizontally). In addition, a horizontally aligned floating object forms a wave structure in the cone shaped dust cloud in the sheath region. Such changes in the propagation characteristics of DAWs are explained on the basis of modified potential (or electric field) distribution, which is a consequence of coupling of sheaths formed around the cylindrical object and the cathode.

  6. Propagation characteristics of dust–acoustic waves in presence of a floating cylindrical object in the DC discharge plasma

    SciTech Connect

    Choudhary, Mangilal; Mukherjee, S.; Bandyopadhyay, P.

    2016-08-15

    The experimental observation of the self–excited dust acoustic waves (DAWs) and its propagation characteristics in the absence and presence of a floating cylindrical object is investigated. The experiments are carried out in a direct current (DC) glow discharge dusty plasma in a background of argon gas. Dust particles are found levitated at the interface of plasma and cathode sheath region. The DAWs are spontaneously excited in the dust medium and found to propagate in the direction of ion drift (along the gravity) above a threshold discharge current at low pressure. Excitation of such a low frequency wave is a result of the ion–dust streaming instability in the dust cloud. Characteristics of the propagating dust acoustic wave get modified in the presence of a floating cylindrical object of radius larger than that of the dust Debye length. Instead of propagation in the vertical direction, the DAWs are found to propagate obliquely in the presence of the floating object (kept either vertically or horizontally). In addition, a horizontally aligned floating object forms a wave structure in the cone shaped dust cloud in the sheath region. Such changes in the propagation characteristics of DAWs are explained on the basis of modified potential (or electric field) distribution, which is a consequence of coupling of sheaths formed around the cylindrical object and the cathode.

  7. dc field-emission analysis of GaAs and plasma-source ion-implanted stainless steel

    SciTech Connect

    C. Hernandez; T. Wang; T. Siggins; D. Bullard; H. F. Dylla; C. Reece; N. D. Theodore; D. M. Manos

    2003-06-01

    Field-emission studies have been performed on a GaAs wafer and a sample of its stainless-steel (SS) support electrode that are part of a photocathode gun for the 10 kW Upgrade infrared free electron laser at Jefferson Lab. The objective of the studies presented here is to characterize the effect of both the cleanliness of the wafer and the plasma-source ion-implanted layer on the electrode to suppress field emission. Field emission is the limiting factor to achieve the required 6 MV/m at the surface of the wafer. Potential field emitters are first located on the surface of 1 in. diameter samples with a dc scanning field-emission microscope at 60 MV/m, then each emitter is characterized in a scanning electron microscope equipped with an energy dispersive spectrometer. The GaAs wafer was hydrogen cleaned before the study. The results show three emitters caused by indium contamination during wafer handling. The GaAs wafer thus shows good high-voltage characteristics and the need to maintain cleanliness during handling. The SS sample is hand polished with diamond paste to a 1-m surface finish, then implanted with N2/SiO2 in a plasma-source ion-implantation chamber in preparation for the field-emission studies.

  8. [Initial osteoblast functions on a type of near β-type titanium alloys surfaces modified by the double glow plasma nitriding technology].

    PubMed

    Qu, Y H; Li, F L; Wen, K; Wang, W

    2017-02-09

    Objective: To evaluate the adhesion, proliferation, alkaline phosphatase (ALP) activity and the expression of osteogenesis-related genes and osteoprotegerin (OPG)/receptor activator of NF-κB ligand (RANKL) of osteoblast-like cells on a type of near β-type titanium alloys (Ti-5Zr-3Sn-5Mo-15Nb, TLM) surfaces modified by the double glow plasma nitriding technology, and to investigate the effect of the modified surfaces on the initial functions of osteoblast-like cells. Methods: The surfaces of TLM were modified by the double glow plasma nitriding technology. TLM surfaces without modification were used as control. Cell morphology was observed with scanning electron microscopy (SEM). Methyl thiazolyl tetrazolium (MTT) method was used to measure cell proliferation. Cell ALP activity was evaluated by using reagent kits. The mRNA expression of Runt-related transcription factor-2 (RUNX2), typeⅠcollagen alpha 1 chain (COLⅠ α1) and OPG/RANKL were examined by quantitative real-time PCR(qRT-PCR). Results: Four hour following cell alture, cells on modified surfaces extend filopodia and intercellular junction was tight. Three days later, cell proliferation (0.277±0.007) was significantly higher than that in control group (0.249±0.004) (P<0.01). After two weeks, ALP activity on TLM modified layer (173.6±1.89) was significantly higher than that on unmodified TLM (162.6±2.4) (P<0.01). The mRNA expression of osteoblast marker RUNX2, COLⅠα1 were stronger than that in control group (P<0.05). The expression of OPG mRNA was higher than that in control group (P<0.01), and RANKL mRNA expression was significantly lower than that in control group (P<0.05). Conclusions: The TLM surface modified by the double glow plasma nitriding technology has a positive effect on osteoblasts initial adhesion, proliferation and differentiation, and it can also improve expression of OPG mRNA and has an inhibitory effect on RANKL mRNA expression of osteoblasts.

  9. Investigation of Device Performance and Negative Bias Temperature Instability of Plasma Nitrided Oxide in Nanoscale p-Channel Metal-Oxide-Semiconductor Field-Effect Transistor's

    NASA Astrophysics Data System (ADS)

    Han, In-Shik; Ji, Hee-Hwan; Goo, Tae-Gyu; Yoo, Ook-Sang; Choi, Won-Ho; Na, Min-Ki; Kim, Yong-Goo; Park, Sung-Hyung; Lee, Heui-Seung; Kang, Young-Seok; Kim, Dae-Byung; Lee, Hi-Deok

    2008-04-01

    In this paper, we investigated the device performance and negative bias temperature instability (NBTI) degradation for thermally nitrided oxide (TNO) and plasma nitrided oxide (PNO) in nanoscale p-channel metal oxide semiconductor field effect transistor (PMOSFET). PNOs show the improvement of dielectric performance compared to TNO with no change of the device performance. PNOs also show the improvement of NBTI immunity than TNO at low temperature stress, whereas NBTI immunity of PNO with high N concentration can be worse than TNO at high temperature stress. Recovery effect of NBTI degradation of PNO is lower than that of TNO and it is increased as the N concentration is increased in PNO because the dissociated Si dangling bonds and generated positive oxide charges are repassivated and neutralized, respectively. Moreover, complete recovery of ΔVth is dominated by neutralization of positive oxide charges. Therefore, N contents at polycrystalline Si/SiO2 interface as well as N contents at Si/SiO2 interface can affect significantly on NBTI degradation and recovery effect.

  10. Investigation of complexity dynamics in a DC glow discharge magnetized plasma using recurrence quantification analysis

    SciTech Connect

    Mitra, Vramori; Sarma, Bornali; Sarma, Arun; Janaki, M. S.; Sekar Iyengar, A. N.; Kurths, Jürgen

    2016-06-15

    Recurrence is an ubiquitous feature which provides deep insights into the dynamics of real dynamical systems. A suitable tool for investigating recurrences is recurrence quantification analysis (RQA). It allows, e.g., the detection of regime transitions with respect to varying control parameters. We investigate the complexity of different coexisting nonlinear dynamical regimes of the plasma floating potential fluctuations at different magnetic fields and discharge voltages by using recurrence quantification variables, in particular, DET, L{sub max}, and Entropy. The recurrence analysis reveals that the predictability of the system strongly depends on discharge voltage. Furthermore, the persistent behaviour of the plasma time series is characterized by the Detrended fluctuation analysis technique to explore the complexity in terms of long range correlation. The enhancement of the discharge voltage at constant magnetic field increases the nonlinear correlations; hence, the complexity of the system decreases, which corroborates the RQA analysis.

  11. Morphology of zirconia particles exposed to D.C. arc plasma jet

    NASA Technical Reports Server (NTRS)

    Zaplatynsky, Isidor

    1987-01-01

    Zirconia particles were sprayed into water with an arc plasma gun in order to determine the effect of various gun operating parameters on their morphology. The collected particles were examined by XRD and SEM techniques. A correlation was established between the content of spherical (molten) particles and the operating parameters by visual inspection and regression analysis. It was determined that the composition of the arc gas and the power input were the predominant parameters that affected the melting of zirconia particles.

  12. Destruction of inorganic municipal solid waste incinerator fly ash in a DC arc plasma furnace.

    PubMed

    Zhao, Peng; Ni, Guohua; Jiang, Yiman; Chen, Longwei; Chen, Mingzhou; Meng, Yuedong

    2010-09-15

    Due to the toxicity of dioxins, furans and heavy metals, there is a growing environmental concern on municipal solid waste incinerator (MSWI) fly ash in China. The purpose of this study is directed towards the volume-reduction of fly ash without any additive by thermal plasma and recycling of vitrified slag. This process uses extremely high-temperature in an oxygen-starved environment to completely decompose complex waste into very simple molecules. For developing the proper plasma processes to treat MSWI fly ash, a new crucible-type plasma furnace was built. The melting process metamorphosed fly ash to granulated slag that was less than 1/3 of the volume of the fly ash, and about 64% of the weight of the fly ash. The safety of the vitrified slag was tested. The properties of the slag were affected by the differences in the cooling methods. Water-cooled and composite-cooled slag showed more excellent resistance against the leaching of heavy metals and can be utilized as building material without toxicity problems. Copyright 2010 Elsevier B.V. All rights reserved.

  13. Argon–oxygen dc magnetron discharge plasma probed with ion acoustic waves

    SciTech Connect

    Saikia, Partha Saikia, Bipul Kumar; Goswami, Kalyan Sindhu; Phukan, Arindam

    2014-05-15

    The precise determination of the relative concentration of negative ions is very important for the optimization of magnetron sputtering processes, especially for those undertaken in a multicomponent background produced by adding electronegative gases, such as oxygen, to the discharge. The temporal behavior of an ion acoustic wave excited from a stainless steel grid inside the plasma chamber is used to determine the relative negative ion concentration in the magnetron discharge plasma. The phase velocity of the ion acoustic wave in the presence of negative ions is found to be faster than in a pure argon plasma, and the phase velocity increases with the oxygen partial pressure. Optical emission spectroscopy further confirms the increase in the oxygen negative ion density, along with a decrease in the argon positive ion density under the same discharge conditions. The relative negative ion concentration values measured by ion acoustic waves are compared with those measured by a single Langmuir probe, and a similarity in the results obtained by both techniques is observed.

  14. Plasma deposition of low dielectric constant (k=2.2{approx}2.4) Boron Nitride on methylsilsesquioxane-based nanoporous films

    SciTech Connect

    Liu Jun; Loh, K.P.; Lin Ming; Foo, Y.L.; Wang, W.D.; Chi, D.Z.

    2004-12-01

    The growth of low dielectric constant (k) Boron Nitride (BN) film on silicon as well as methylsilsesquioxane-based nanoporous films (LKD-5109) using plasma-discharged borazine was investigated. BN films were grown using microwave plasma (2.45 GHz) or radio-frequency (rf) atom beam deposition (13.56 MHz) on LKD-5109 in order to evaluate the compatibility of the two plasma processes with the physical integrity of the nanoporous films. Capacitance-voltage measurements were used to characterize the dielectric constants of the films on silicon and BN-integrated LKD (k{sub eff}{approx_equal}2.4). The composition and phases of the films were studied using cross-section transmission electron microscopy and electron-energy-loss spectroscopy. Although the microwave plasma process could produce BC{sub x}N films with a k value of 2.2, the process was not compatible with the nanoporous LKD substrate due to the ion-induced damage of the films. We found that only the rf atom beam deposition process, which was characterized by low-energy neutral fluxes, maintained the dielectric property of the BN-integrated LKD stack at an overall value of 2.4. In addition, the deposited BN films can act as an effective copper diffusion barrier on the LKD and can be lithographically processed to form trench patterns.

  15. Effects of bias voltage on the corrosion resistance of titanium nitride thin films fabricated by dynamic plasma immersion ion implantation-deposition

    NASA Astrophysics Data System (ADS)

    Tian, Xiubo; Fu, Ricky K. Y.; Chu, Paul K.

    2002-01-01

    Dynamic plasma-based thin-film deposition incorporating ion mixing and plasma immersion is an effective technique to synthesize nitride-based hard films. We have fabricated TiN films using a filtered titanium vacuum arc in a nitrogen plasma environment. A pulsed high voltage is applied to the target for a short time when the metallic arc is fired to attain simultaneous plasma deposition and ion mixing. We investigate the dependence of the corrosion resistance and interfacial structure of the treated samples on the applied voltage. Our Auger results reveal an oxygen-rich surface film due to the non-ultra-high-vacuum conditions and high affinity of oxygen to titanium. The corrosion current is reduced by two orders of magnitude comparing the sample processed at 8 kV to the untreated sample, but the 23 kV sample unexpectedly shows worse results. The pitting potential diminishes substantially although the corrosion current is similar to that observed in the 8 kV sample. The polarization test data are consistent with our scanning electron microscopy observation, corroborating the difference in the pitting distribution and appearance. This anomalous behavior is believed to be due to the change in the chemical composition as a result of high-energy ion bombardment.

  16. Experimental Studies of DC-excited Plasma Discharges in HMDSN-SF6 Mixtures

    NASA Astrophysics Data System (ADS)

    Pinto Mota, Rogério; Godoy de Santana, Regiane; Algatti, Mauricio Antonio; Yzumi Honda, Roberto; Eiji Kayama, Milton

    1996-10-01

    The study of the structure of thin films from glow discharges and their correlation with discharge parameters is very important for choosing a pre- determined physical property. In this work, we performed measurements of electron temperature using a cylindrical Langmuir probe in DC discharges of HMDSN/SF6 for several mixtures with the proportion of SF6 varying from 0 to 50%, at a total pressure of 0.6 mbar. The voltage applied across the discharge was kept constant at 800V. The electron temperature varied from 0.6 to 2.0 eV, presenting a parabolic profile decreasing from the middle towards the edge of the electrode. The same behavior was also observed for the film thickness profile. The film growth rate varied from 12 to 155 Åmin, presenting a maximum at 20% SF_6. The FTIR spectra of the polymeric films showed the disappearance of the chemical bonds C-H, Si-H, and Si-CH3 for SF6 percentages above 30%, and the appearance C-F and Si-F chemical bonds.

  17. Plasma nitriding process by direct current glow discharge at low temperature increasing the thermal diffusivity of AISI 304 stainless steel

    SciTech Connect

    Prandel, L. V.; Somer, A.; Assmann, A.; Camelotti, F.; Costa, G.; Bonardi, C.; Jurelo, A. R.; Rodrigues, J. B.; Cruz, G. K.

    2013-02-14

    This work reports for the first time on the use of the open photoacoustic cell technique operating at very low frequencies and at room temperature to experimentally determine the thermal diffusivity parameter of commercial AISI304 stainless steel and AISI304 stainless steel nitrided samples. Complementary measurements of X-ray diffraction and scanning electron microscopy were also performed. The results show that in standard AISI 304 stainless steel samples the thermal diffusivity is (4.0 {+-} 0.3) Multiplication-Sign 10{sup -6} m{sup 2}/s. After the nitriding process, the thermal diffusivity increases to the value (7.1 {+-} 0.5) Multiplication-Sign 10{sup -6} m{sup 2}/s. The results are being associated to the diffusion process of nitrogen into the surface of the sample. Carrying out subsequent thermal treatment at 500 Degree-Sign C, the thermal diffusivity increases up to (12.0 {+-} 2) Multiplication-Sign 10{sup -6} m{sup 2}/s. Now the observed growing in the thermal diffusivity must be related to the change in the phases contained in the nitrided layer.

  18. Feasibility study of silicon nitride protection of plastic encapsulated semiconductors

    NASA Technical Reports Server (NTRS)

    Peters, J. W.; Hall, T. C.; Erickson, J. J.; Gebhart, F. L.

    1979-01-01

    The application of low temperature silicon nitride protective layers on wire bonded integrated circuits mounted on lead frame assemblies is reported. An evaluation of the mechanical and electrical compatibility of both plasma nitride and photochemical silicon nitride (photonitride) passivations (parallel evaluations) of integrated circuits which were then encapsulated in plastic is described. Photonitride passivation is compatible with all wire bonded lead frame assemblies, with or without initial chip passivation. Plasma nitride passivation of lead frame assemblies is possible only if the chip is passivated before lead frame assembly. The survival rate after the environmental test sequence of devices with a coating of plasma nitride on the chip and a coating of either plasma nitride or photonitride over the assembled device is significantly greater than that of devices assembled with no nitride protective coating over either chip or lead frame.

  19. Electron Backscatter Diffraction and Transmission Kikuchi Diffraction Analysis of an Austenitic Stainless Steel Subjected to Surface Mechanical Attrition Treatment and Plasma Nitriding.

    PubMed

    Proust, Gwénaëlle; Retraint, Delphine; Chemkhi, Mahdi; Roos, Arjen; Demangel, Clemence

    2015-08-01

    Austenitic 316L stainless steel can be used for orthopedic implants due to its biocompatibility and high corrosion resistance. Its range of applications in this field could be broadened by improving its wear and friction properties. Surface properties can be modified through surface hardening treatments. The effects of such treatments on the microstructure of the alloy were investigated here. Surface Mechanical Attrition Treatment (SMAT) is a surface treatment that enhances mechanical properties of the material surface by creating a thin nanocrystalline layer. After SMAT, some specimens underwent a plasma nitriding process to further enhance their surface properties. Using electron backscatter diffraction, transmission Kikuchi diffraction, energy dispersive spectroscopy, and transmission electron microscopy, the microstructural evolution of the stainless steel after these different surface treatments was characterized. Microstructural features investigated include thickness of the nanocrystalline layer, size of the grains within the nanocrystalline layer, and depth of diffusion of nitrogen atoms within the material.

  20. Vibrational excitation in O2and Cl2inductively-coupled plasmas and DC discharges

    NASA Astrophysics Data System (ADS)

    Booth, Jean-Paul; Marinov, Daniil; Foucher, Mickael; Annusova, Adriana; Guerra, Vasco

    2016-09-01

    Low-energy electrons can interact with molecules via resonances to cause vibrational excitation with large cross-sections. Such processes can absorb significant energy from the plasma electrons, affecting the electron energy distribution and potentially (via vibration-translation (VT) energy transfer) causing substantial gas heating. The presence of vibrationally excited molecules may significant increase the rates of collisional processes, including electron dissociative attachment and electron impact dissociation into neutral atoms. However, the cross-sections of these processes are often poorly known since they are extremely difficult to measure directly, and reliable theoretical calculations are only now appearing for simple diatomic molecules. We have measured the vibrational distributions in discharges in pure O2 and pure Cl2, using high-sensitivity ultra-broadband ultraviolet absorption spectroscopy. In O2 plasmas significant vibrational excitation is observed, up to v'' =18, with a tail temperature of around 8000K. In Cl2 excitation is only observed up to v'' =3, and the distribution appears to be in local equilibrium with the gas translational temperature (up to 1500K). We are developing a detailed self-consistent 0D global model of these systems including vibrational excitation. Work performed in the LABEX Plas@par project, with financial state aid (ANR-11-IDEX-0004-02 and ANR-13-BS09-0019).

  1. Modelling of the layer evolution during nitriding processes

    SciTech Connect

    Figueroa, U.; Oseguera, J.; Schabes, P.

    1995-12-31

    The evolution of concomitant layers of nitrides is presented. The layer formation is experimentally achieved through two processes: Nitriding with a weakly ionized plasma and nitrogen post-discharge nitriding. The nitriding processes were performed on samples of pure iron and carbon steel. Nitriding temperatures were close but different from the eutectoid transformation point temperature. The experimental layer growth pattern is compared with a model of mass transfer, in which interface mass balance is considered. In the model the authors have considered the formation of one and two compact nitride layers. For short time of treatment, it is shown that a parabolic profile does not satisfactorily describe the layer growth.

  2. Boron nitride nanotubes.

    PubMed

    Chopra, N G; Luyken, R J; Cherrey, K; Crespi, V H; Cohen, M L; Louie, S G; Zettl, A

    1995-08-18

    The successful synthesis of pure boron nitride (BN) nanotubes is reported here. Multi-walled tubes with inner diameters on the order of 1 to 3 nanometers and with lengths up to 200 nanometers were produced in a carbon-free plasma discharge between a BN-packed tungsten rod and a cooled copper electrode. Electron energy-loss spectroscopy on individual tubes yielded B:N ratios of approximately 1, which is consistent with theoretical predictions of stable BN tube structures.

  3. Impact of interstitial oxygen trapped in silicon during plasma growth of silicon oxy-nitride films for silicon solar cell passivation

    NASA Astrophysics Data System (ADS)

    Saseendran, Sandeep S.; Saravanan, S.; Raval, Mehul C.; Kottantharayil, Anil

    2016-03-01

    Low temperature oxidation of silicon in plasma ambient is a potential candidate for replacing thermally grown SiO2 films for surface passivation of crystalline silicon solar cells. In this work, we report the growth of silicon oxy-nitride (SiOxNy) film in N2O plasma ambient at 380 °C. However, this process results in trapping of interstitial oxygen within silicon. The impact of this trapped interstitial oxygen on the surface passivation quality is investigated. The interstitial oxygen trapped in silicon was seen to decrease for larger SiOxNy film thickness. Effective minority carrier lifetime (τeff) measurements on n-type float zone silicon wafers passivated by SiOxNy/silicon nitride (SiNv:H) stack showed a decrease in τeff from 347 μs to 68 μs, for larger SiOxNy film thickness due to degradation in interface properties. From high frequency capacitance-voltage measurements, it was concluded that the surface passivation quality was governed by the interface parameters (fixed charge density and interface state density). High temperature firing of the SiOxNy/SiNv:H stack resulted in a severe degradation in τeff due to migration of oxygen across the interface into silicon. However, on using the SiOxNy/SiNv:H stack for emitter surface passivation in screen printed p-type Si solar cells, an improvement in short wavelength response was observed in comparison to the passivation by SiNv:H alone, indicating an improvement in emitter surface passivation quality.

  4. DC superimposed AC high voltage: A new strategy for transferring stable He atmospheric pressure cold plasma bullets through long dielectric tubes

    NASA Astrophysics Data System (ADS)

    Siadati, S. N.; Sohbatzadeh, F.; Valinataj Omran, Azadeh

    2017-06-01

    This study developed a stable transfer of He atmospheric pressure cold plasma bullets in a large dielectric tube with a length of 70 cm and an inner diameter of 0.4-1.6 cm. DC superimposed AC voltage was used for this purpose. The DC component of the applied voltage generated corona ionization through the tube, which helped in the ignition and transfer of the plasma as a pre-ionization background. The bullets followed the frequency of the AC component; therefore, very high applied energy was not required to ignite this large-scale plasma. To our knowledge, this is the first time such a complex waveform has been reported for the transfer of a plasma bullet. The characteristics of the transferring plasma bullet, such as the power, charge, propagation speed, resistance, AC electrical field (EF) of the plasma, and electrostatic field on the tube surface, were measured. The influence of the tube diameter on these characteristics was investigated. The results showed that the power applied, charge, and power deposited on the target increased as the tube diameter increased. Less plasma resistance and radiation were observed using larger diameters. The root mean square (RMS) values of the axial AC EF of the bullet along the jet axis were higher for the larger diameters, but no special relation between the propagation speed, radial AC EF, and static surface field and tube diameter was observed.

  5. Low temperature plasma enhanced atomic layer deposition of conducting zirconium nitride films using tetrakis (dimethylamido) zirconium and forming gas (5% H{sub 2} + 95% N{sub 2}) plasma

    SciTech Connect

    Muneshwar, Triratna Cadien, Ken

    2015-05-15

    Zirconium nitride (ZrN) has the lowest bulk electrical resistivity and high thermal stability among group IV and V transition metal nitrides, which makes it a promising material for ULSI applications such as a diffusion barrier for Cu interconnects, contact metal in III-V semiconductor devices, and in high density memory structures. Plasma enhanced atomic layer deposition (PEALD) of conducting ZrN thin films using Zr[N(CH{sub 3}){sub 2}]{sub 4} and forming gas (5% H{sub 2} + 95% N{sub 2}) plasma is reported in this article. The growth per cycle (GPC) for every deposition was determined from analysis of dynamic in-situ spectroscopic ellipsometry (d-iSE) measurements. An experimental design is proposed for faster determination of ALD growth saturation curves. At substrate temperature of 150 °C, a GPC of 0.10 nm/cycle was observed for self-limiting ZrN PEALD growth. The electrical resistivity of ZrN films deposited on SiO{sub 2} substrate was found to be 559.5 ± 18.5 μΩ cm with negligible change in resistivity even after ∼1000 h exposure to air. The metallic behavior of our ZrN films was evident from the free electron dispersion component in dielectric response, the broad band of photoelectron emission across Fermi level and the positive temperature coefficient for resistivity of 0.0088/ °C.

  6. Plasma potential of a moving ionization zone in DC magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Panjan, Matjaž; Anders, André

    2017-02-01

    Using movable emissive and floating probes, we determined the plasma and floating potentials of an ionization zone (spoke) in a direct current magnetron sputtering discharge. Measurements were recorded in a space and time resolved manner, which allowed us to make a three-dimensional representation of the plasma potential. From this information we could derive the related electric field, space charge, and the related spatial distribution of electron heating. The data reveal the existence of strong electric fields parallel and perpendicular to the target surface. The largest E-fields result from a double layer structure at the leading edge of the ionization zone. We suggest that the double layer plays a crucial role in the energization of electrons since electrons can gain several 10 eV of energy when crossing the double layer. We find sustained coupling between the potential structure, electron heating, and excitation and ionization processes as electrons drift over the magnetron target. The brightest region of an ionization zone is present right after the potential jump, where drifting electrons arrive and where most local electron heating occurs. The ionization zone intensity decays as electrons continue to drift in the Ez × B direction, losing energy by inelastic collisions; electrons become energized again as they cross the potential jump. This results in the elongated, arrowhead-like shape of the ionization zone. The ionization zone moves in the -Ez × B direction from which the to-be-heated electrons arrive and into which the heating region expands; the zone motion is dictated by the force of the local electric field on the ions at the leading edge of the ionization zone. We hypothesize that electron heating caused by the potential jump and physical processes associated with the double layer also apply to magnetrons at higher discharge power, including high power impulse magnetron sputtering.

  7. Plasma-Radiation-Induced Interface States in Metal-Nitride-Oxide-Silicon Structure of Charge-Coupled Device Image Sensor and Their Reduction Using Pulse-Time-Modulated Plasma

    NASA Astrophysics Data System (ADS)

    Okigawa, Mitsuru; Ishikawa, Yasushi; Samukawa, Seiji

    2003-04-01

    We found that ultraviolet (UV) light from helium discharge plasma and a halogen lamp clearly induce SiO2-Si interface states in a metal-silicon-nitride-oxide-silicon (MNOS) structure. A dark current originating in the interface states of charge-coupled-device (CCD) image sensors also increases by this UV irradiation. Pulse-time-modulated (TM) plasma suppresses the interface states, resulting in the CCD dark current, by decreasing the UV light. On the other hand, results of Capacitance-Voltage (CV) measurement did not show the difference between UV irradiation and no irradiation. This indicates that fixed charges in the SiO2 cannot be generated by the UV lights. Using optical filters, we revealed that a photon energy of 3.90 eV (318 nm) to 4.96 eV (250 nm) causes an increase in the interface states.

  8. Field emission from open ended aluminum nitride nanotubes

    NASA Astrophysics Data System (ADS)

    Tondare, V. N.; Balasubramanian, C.; Shende, S. V.; Joag, D. S.; Godbole, V. P.; Bhoraskar, S. V.; Bhadbhade, M.

    2002-06-01

    This letter reports the field emission measurements from the nanotubes of aluminum nitride which were synthesized by gas phase condensation using the solid-vapor equilibria. A dc arc plasma reactor was used for producing the vapors of aluminum in a reactive nitrogen atmosphere. Nanoparticles and nanotubes of aluminum nitride were first characterized by transmission electron microscope and tube dimensions were found to be varying from 30 to 200 nm in diameter and 500 to 700 nm in length. These tubes were mixed with nanoparticles of size range between 5 and 200 nm in diameter. Tungsten tips coated with these nanoparticles and tubes were used as a field emitter. The field emission patterns display very interesting features consisting of sharp rings which were often found to change their shapes. The patterns are attributed to the open ended nanotubes of aluminum nitride. A few dot patterns corresponding to the nanoparticles were also seen to occur. The Fowler-Nordheim plots were seen to be nonlinear in nature, which reflects the semi-insulating behavior of the emitter. The field enhancement factor is estimated to be 34 500 indicating that the field enhancement due to the nanometric size of the emitter is an important cause for the observed emission.

  9. Numerical study of an ArH2 gas mixture flowing inside and outside a dc plasma torch

    NASA Astrophysics Data System (ADS)

    Eichert, P.; Imbert, M.; Coddet, C.

    1998-12-01

    The flow of gas mixtures in a dc plasma torch is studied using the CFD PHOENICS (CFD PHOENICS, Berkeley, CA) code. In the model, the cold gas mixture (300 K), initially constituted of 85 vol% Ar and 15 vol% H, is introduced into a power input zone where it takes energy and is ejected in the surrounding atmosphere at constant pressure (105 Pa). The flow is assumed to be in chemical equilibrium. Equations of mass, momentum, and energy are discretized using a control-volume method. The turbulent flow is modeled by a k-ɛ two-equations model for the turbulent kinetic energy and its dissipation rate. Finally, the algebraic coupling equations set is solved by means of the SIMPLEST algorithm, implemented into the CFD code, using a hybrid interpolation scheme. Results concern the effect of the torch power on the ArH2 flow. The phenomenon is analyzed through the evolution of velocity and temperature inside and outside the torch. From these calculations, the effect of ambient gas entrainment by the jet is emphasized and a comparison of the level of entrained gas is made with experimental data.

  10. Functionalized boron nitride nanotubes

    DOEpatents

    Sainsbury, Toby; Ikuno, Takashi; Zettl, Alexander K

    2014-04-22

    A plasma treatment has been used to modify the surface of BNNTs. In one example, the surface of the BNNT has been modified using ammonia plasma to include amine functional groups. Amine functionalization allows BNNTs to be soluble in chloroform, which had not been possible previously. Further functionalization of amine-functionalized BNNTs with thiol-terminated organic molecules has also been demonstrated. Gold nanoparticles have been self-assembled at the surface of both amine- and thiol-functionalized boron nitride Nanotubes (BNNTs) in solution. This approach constitutes a basis for the preparation of highly functionalized BNNTs and for their utilization as nanoscale templates for assembly and integration with other nanoscale materials.

  11. Multifunctional bulk plasma source based on discharge with electron injection

    SciTech Connect

    Klimov, A. S.; Medovnik, A. V.; Tyunkov, A. V.; Savkin, K. P.; Shandrikov, M. V.; Vizir, A. V.

    2013-01-15

    A bulk plasma source, based on a high-current dc glow discharge with electron injection, is described. Electron injection and some special design features of the plasma arc emitter provide a plasma source with very long periods between maintenance down-times and a long overall lifetime. The source uses a sectioned sputter-electrode array with six individual sputter targets, each of which can be independently biased. This discharge assembly configuration provides multifunctional operation, including plasma generation from different gases (argon, nitrogen, oxygen, acetylene) and deposition of composite metal nitride and oxide coatings.

  12. Microstructural characterization of Ti-6Al-4V alloy subjected to the duplex SMAT/plasma nitriding.

    PubMed

    Pi, Y; Faure, J; Agoda-Tandjawa, G; Andreazza, C; Potiron, S; Levesque, A; Demangel, C; Retraint, D; Benhayoune, H

    2013-09-01

    In this study, microstructural characterization of Ti-6Al-4V alloy, subjected to the duplex surface mechanical attrition treatment (SMAT)/nitriding treatment, leading to improve its mechanical properties, was carried out through novel and original samples preparation methods. Instead of acid etching which is limited for morphological characterization by scanning electron microscopy (SEM), an original ion polishing method was developed. Moreover, for structural characterization by transmission electron microscopy (TEM), an ion milling method based with the use of two ions guns was also carried out for cross-section preparation. To demonstrate the efficiency of the two developed methods, morphological investigations were done by traditional SEM and field emission gun SEM. This was followed by structural investigations through selected area electron diffraction (SAED) coupled with TEM and X-ray diffraction techniques. The results demonstrated that ionic polishing allowed to reveal a variation of the microstructure according to the surface treatment that could not be observed by acid etching preparation. TEM associated to SAED and X-ray diffraction provided information regarding the nanostructure compositional changes induced by the duplex SMAT/nitriding process.

  13. DC and Structured Electric Fields Observed on the C/NOFS Satellite and Their Association with Longitude, Plasma Density, and Solar Activity

    NASA Technical Reports Server (NTRS)

    Pfaff, Robert; Freudenreich, H.; Rowland, D.; Klenzing, J.

    2012-01-01

    Observations of DC electric fields and associated E x B plasma drifts gathered by the Vector Electric Field Investigation (VEFI) on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite are presented. We show statistical averages of the vector fields and resulting E x B plasma flows for the first three years of operations as a function of season, longitude, local time, and Fl 0.7 conditions. Magnetic field data from the VEFI science magnetometer are used to compute the plasma flows. Although typically displaying eastward and outward-directed fields during the day and westward and downward-directed fields at night, the data from DC electric field detector often reveal variations from this pattern that depend on longitude, solar activity, and plasma density. Clear "wave-4" tidal effects in both electric field components have been detected and will be presented. Zonal plasma drifts show a marked variation with solar activity and may be used as a proxy for neutral winds at night. Evidence for pre-reversal enhancements in the meridional drifts that depend on solar activity is present for some longitudes, and are corroborated by clear evidence in the plasma density data that the spacecraft journeyed below the F-peak during evenings when the rise in the ionosphere is most pronounced. In addition to DC electric fields, the data reveal considerable electric field structures at large scales (approx 100's of km) that are usually confined to the nightside. Although such electric field structures are typically associated with plasma density depletions and structures, what is surprising is the number of cases in which large amplitude, structured DC electric fields are observed without a significant plasma density counterpart structure, including their appearance at times when the ambient plasma density appears relatively quiescent. We investigate the mapping of structured electric fields along magnetic field lines from distant locations and consider

  14. Synthesis of AlN/Al Polycrystals along with Al Nanoparticles Using Thermal Plasma Route

    SciTech Connect

    Kanhe, Nilesh S.; Nawale, A. B.; Kulkarni, N. V.; Bhoraskar, S. V.; Mathe, V. L.; Das, A. K.

    2011-07-15

    This paper for the first time reports the (200) oriented growth of hexagonal Aluminum nitride crystals during synthesis of aluminum nanoparticles in dc transferred arc thermal plasma reactor by gas phase condensation in nitrogen plasma. The structural and morphological study of as synthesized AlN crystal and aluminium nanoparticles was done by using the x-ray diffraction method, scanning electron microscopy and transmission electron microscopy.

  15. High energy electron fluxes in dc-augmented capacitively coupled plasmas. II. Effects on twisting in high aspect ratio etching of dielectrics

    SciTech Connect

    Wang Mingmei; Kushner, Mark J.

    2010-01-15

    In high aspect ratio (HAR) plasma etching of holes and trenches in dielectrics, sporadic twisting is often observed. Twisting is the randomly occurring divergence of a hole or trench from the vertical. Many causes have been proposed for twisting, one of which is stochastic charging. As feature sizes shrink, the fluxes of plasma particles, and ions in particular, into the feature become statistical. Randomly deposited charge by ions on the inside of a feature may be sufficient to produce lateral electric fields which divert incoming ions and initiate nonvertical etching or twisting. This is particularly problematic when etching with fluorocarbon gas mixtures where deposition of polymer in the feature may trap charge. dc-augmented capacitively coupled plasmas (dc-CCPs) have been investigated as a remedy for twisting. In these devices, high energy electron (HEE) beams having narrow angular spreads can be generated. HEEs incident onto the wafer which penetrate into HAR features can neutralize the positive charge and so reduce the incidence of twisting. In this paper, we report on results from a computational investigation of plasma etching of SiO{sub 2} in a dc-CCP using Ar/C{sub 4}F{sub 8}/O{sub 2} gas mixtures. We found that HEE beams incident onto the wafer are capable of penetrating into features and partially neutralizing positive charge buildup due to sporadic ion charging, thereby reducing the incidence of twisting. Increasing the rf bias power increases the HEE beam energy and flux with some indication of improvement of twisting, but there are also changes in the ion energy and fluxes, so this is not an unambiguous improvement. Increasing the dc bias voltage while keeping the rf bias voltage constant increases the maximum energy of the HEE and its flux while the ion characteristics remain nearly constant. For these conditions, the occurrence of twisting decreases with increasing HEE energy and flux.

  16. A novel technique based on a plasma focus device for nano-porous gallium nitride formation on P-type silicon

    NASA Astrophysics Data System (ADS)

    Sharifi Malvajerdi, S.; Salar Elahi, A.; Habibi, M.

    2017-04-01

    A new deposition formation was observed with a Mather-type Plasma Focus Device (MPFD). MPFD was unitized to fabricate porous Gallium Nitride (GaN) on p-type Silicon (Si) substrate with a (100) crystal orientation for the first time in a deposition process. GaN was deposited on Si with 4 and 7 shots. The samples were subjected to a 3 phase annealing procedure. First, the semiconductors were annealed in the PFD with nitrogen plasma shots after their deposition. Second, a thermal chemical vapor deposition annealed the samples for 1 h at 1050 °C by nitrogen gas at a pressure of 1 Pa. Finally, an electric furnace annealed the samples for 1 h at 1150 °C with continuous flow of nitrogen. Porous GaN structures were observed by Field emission scanning electron microscopy and atomic force microscopy. Furthermore, X-Ray diffraction analysis was carried out to determine the crystallinity of GaN after the samples were annealed. Energy-Dispersive X-Ray Spectroscopy indicated the amount of gallium, nitrogen, and oxygen due to the self-oxidation of the samples. Photoluminescence spectroscopy revealed emissions at 2.94 eV and 3.39 eV, which shows that hexagonal wurtzite crystal structures were formed.

  17. DC and Wave Electric Fields and Other Plasma Parameters Observed on Two Sounding Rockets in the Dark Cusp During IMF Bz North and South Conditions

    NASA Technical Reports Server (NTRS)

    Pfaff, R. F.; Acuna, M.; Bounds, S.; Farrell, W.; Freudenreich, H.; Lepping, R.; Vondrak, R.; Maynard, N. C.; Moen, J.; Egeland, A.

    1997-01-01

    Two Black Brant IX sounding rockets were launched into the dark, dayside cusp near magnetic noon on December 2 and 3, 1997, from Ny Alesund, Spitzbergen at 79 N reaching altitudes of approximately 450 km. Real-time ground-based and Wind IMF data were used to determine the launch conditions. The first launch, with Bz north conditions, crossed into and back out of an open field region with merging poleward of the projected trajectory. The second flight, into Bz south conditions, was timed to coincide with an enhancement in the merging rate from a increase in the negative Bz, while the DMSP F13 satellite was situated slightly to the north of the rocket trajectory. Each payload returned DC electric and magnetic fields, plasma waves, energetic particles, photometer data, and thermal plasma data. Data from both flights will be shown, with an emphasis on the DC electric field results. In particular, the data gathered on December 2, 1997 will be used to discuss ionospheric signatures of merging and the open/closed character of the the cusp/low latitude boundary layer. In contrast, the data gathered on December 3, 1997 shows evidence of pulsed electric field structures which will be examined in the context of cusp plasma entry processes. Both data sets returned a rich variety of plasma waves, as well as optical emissions and thermal plasma data.

  18. DC and Wave Electric Fields and Other Plasma Parameters Observed on Two Sounding Rockets in the Dark Cusp during IMF BZ North and South Conditions

    NASA Technical Reports Server (NTRS)

    Pfaff, R. F.; Bounds, S.; Acuna, M.; Maynard, N. C.; Moen, J.; Egeland, A.; Holtet, J.; Maseide, K.; Sandholt, P. E.; Soraas, F.

    1999-01-01

    Two Black Brant IX sounding rockets were launched into the dark, dayside cusp near magnetic noon on December 2 and 3, 1997, from Ny Alesund, Spitzbergen at 79degN reaching altitudes of approximately 450 km. Real-time ground-based and Wind (interplanetary magnetic field) IMF data were used to determine the launch conditions. The first launch, with Bz north conditions, crossed into and back out of an open field region with merging poleward of the projected trajectory. The second flight, into Bz south conditions, was timed to coincide with an enhancement in the merging rate from a increase in the negative Bz, while the (Defense Meteorological Satellite Program) DMSP F13 satellite was situated slightly to the north of the rocket trajectory. Each payload returned DC electric and magnetic fields, plasma waves, energetic particles, photometer data, and thermal plasma data. Data from both flights will be shown, with an emphasis on the DC electric field results. In particular, the data gathered on December 2, 1997 will be used to discuss ionospheric signatures of merging and the open/closed character of the the cusp/low latitude boundary layer. In contrast, the data gathered on December 3, 1997 shows evidence of pulsed electric field structures which will be examined in the context of cusp plasma entry processes. Both data sets returned a rich variety of plasma waves, as well as optical emissions and thermal plasma data.

  19. DC and Wave Electric Fields and Other Plasma Parameters Observed on Two Sounding Rockets in the Dark Cusp during IMF Bz North and South Conditions

    NASA Technical Reports Server (NTRS)

    Pfaff, R. F.; Acuna, M.; Bounds, S.; Farrell, W.; Freudenreich, W.; Lepping, R.; Vondrak, R.; Maynard, N. C.; Moen, J.; Egeland, A.

    1999-01-01

    Two Black Brant IX sounding rockets were launched into the dark, dayside cusp near magnetic noon on December 2 and 3, 1997, from Ny Alesund, Spitzbergen at 79 deg N reaching altitudes of about 450 km. Real-time ground-based and Wind IMF data were used to determine the launch conditions. The first launch, with Bz north conditions, crossed into and back out of an open field region with merging poleward of the projected trajectory. The second flight, into Bz south conditions, was timed to coincide with an enhancement in the merging rate from a increase in the negative Bz, while the DMSP Fl 3 satellite was situated slightly to the north of the rocket trajectory. Each payload returned DC electric and magnetic fields, plasma waves, energetic particles, photometer data, and thermal plasma data. Data from both flights will be shown, with an emphasis on the DC electric field results. In particular, the data gathered on December 2, 1997 will be used to discuss ionospheric signatures of merging and the open/closed character of the the cusp/low latitude boundary layer. In contrast, the data gathered on December 3, 1997 shows evidence of pulsed electric field structures which will be examined in the context of cusp plasma entry processes. Both data sets returned a rich variety of plasma waves, as well as optical emissions and thermal plasma data.

  20. DC and Wave Electric Fields and Other Plasma Parameters Observed on Two Sounding Rockets in the Dark Cusp during IMF BZ North and South Conditions

    NASA Technical Reports Server (NTRS)

    Pfaff, R. F.; Bounds, S.; Acuna, M.; Maynard, N. C.; Moen, J.; Egeland, A.; Holtet, J.; Maseide, K.; Sandholt, P. E.; Soraas, F.

    1999-01-01

    Two Black Brant IX sounding rockets were launched into the dark, dayside cusp near magnetic noon on December 2 and 3, 1997, from Ny Alesund, Spitzbergen at 79degN reaching altitudes of approximately 450 km. Real-time ground-based and Wind (interplanetary magnetic field) IMF data were used to determine the launch conditions. The first launch, with Bz north conditions, crossed into and back out of an open field region with merging poleward of the projected trajectory. The second flight, into Bz south conditions, was timed to coincide with an enhancement in the merging rate from a increase in the negative Bz, while the (Defense Meteorological Satellite Program) DMSP F13 satellite was situated slightly to the north of the rocket trajectory. Each payload returned DC electric and magnetic fields, plasma waves, energetic particles, photometer data, and thermal plasma data. Data from both flights will be shown, with an emphasis on the DC electric field results. In particular, the data gathered on December 2, 1997 will be used to discuss ionospheric signatures of merging and the open/closed character of the the cusp/low latitude boundary layer. In contrast, the data gathered on December 3, 1997 shows evidence of pulsed electric field structures which will be examined in the context of cusp plasma entry processes. Both data sets returned a rich variety of plasma waves, as well as optical emissions and thermal plasma data.

  1. M3D-C1 simulations of the plasma response to RMPs in NSTX-U single-null and snowflake divertor configurations

    DOE PAGES

    Canal, G. P.; Ferraro, N. M.; Evans, T. E.; ...

    2017-04-20

    Here in this work, single- and two-fluid resistive magnetohydrodynamic calculations of the plasma response to n = 3 magnetic perturbations in single-null (SN) and snowflake (SF) divertor configurations are compared with those based on the vacuum approach. The calculations are performed using the code M3D-C1 and are based on simulated NSTX-U plasmas. Significantly different plasma responses were found from these calculations, with the difference between the single- and two-fluid plasma responses being caused mainly by the different screening mechanism intrinsic to each of these models. Although different plasma responses were obtained from these different plasma models, no significant difference betweenmore » the SN and SF plasma responses were found. However, due to their different equilibrium properties, magnetic perturbations cause the SF configuration to develop additional and longer magnetic lobes in the null-point region than the SN, regardless of the plasma model used. The intersection of these longer and additional lobes with the divertor plates are expected to cause more striations in the particle and heat flux target profiles. In addition, the results indicate that the size of the magnetic lobes, in both single-null and snowflake configurations, are more sensitive to resonant magnetic perturbations than to non-resonant magnetic perturbations.« less

  2. N, NH, and NH{sub 2} radical densities in a remote Ar-NH{sub 3}-SiH{sub 4} plasma and their role in silicon nitride deposition

    SciTech Connect

    Oever, P. J. van den; Helden, J. H. van; Hemmen, J. L. van; Engeln, R.; Schram, D. C.; Sanden, M. C. M. van de; Kessels, W. M. M.

    2006-11-01

    The densities of N, NH, and NH{sub 2} radicals in a remote Ar-NH{sub 3}-SiH{sub 4} plasma used for high-rate silicon nitride deposition were investigated for different gas mixtures and plasma settings using cavity ringdown absorption spectroscopy and threshold ionization mass spectrometry. For typical deposition conditions, the N, NH, and NH{sub 2} radical densities are on the order of 10{sup 12} cm{sup -3} and the trends with NH{sub 3} flow, SiH{sub 4} flow, and plasma source current are reported. We present a feasible reaction pathway for the production and loss of the NH{sub x} radicals that is consistent with the experimental results. Furthermore, mass spectrometry revealed that the consumption of NH{sub 3} was typically 40%, while it was over 80% for SiH{sub 4}. On the basis of the measured N densities we deduced the recombination and sticking coefficient for N radicals on a silicon nitride film. Using this sticking coefficient and reported surface reaction probabilities of NH and NH{sub 2} radicals, we conclude that N and NH{sub 2} radicals are mainly responsible for the N incorporation in the silicon nitride film, while Si atoms are most likely brought to the surface in the form of SiH{sub x} radicals.

  3. Chemically Adjusting Plasma Temperature, Energy and Reactivity (CAPTEAR) Method Using NOx and Combustion for Selective Synthesis of Sc3N@C80 Metallic Nitride Fullerenes

    PubMed Central

    Stevenson, Steven; Thompson, M. Corey; Coumbe, H. Louie; Mackey, Mary A.; Coumbe, Curtis E.; Phillips, J. Paige

    2008-01-01

    Goals are (1) to selectively synthesize MNFs in lieu of empty-cage fullerenes (e.g., C60, C70) without compromising MNF yield and (2) to test our hypothesis that MNFs possess a different set of optimal formation parameters than empty-cage fullerenes. In this work, we introduce a novel approach for the selective synthesis of metallic nitride fullerenes (MNFs). This new method is “Chemically Adjusting Plasma Temperature, Energy and Reactivity” (CAPTEAR). The CAPTEAR approach with copper nitrate hydrate uses NOx vapor from NOx generating solid reagents, air and combustion to “tune” the temperature, energy and reactivity of the plasma environment. The extent of temperature, energy and reactive environment is stoichiometrically varied until optimal conditions for selective MNF synthesis are achieved. Analysis of soot extracts indicate that percentages of C60 and Sc3N@C80 are inversely related, whereas the percentages of C70 and higher empty-cage C2n fullerenes are largely unaffected. Hence, there may be a “competitive link” in the formation and mechanism of C60 and Sc3N@C80. Using this CAPTEAR method, purified MNFs (96% Sc3N@C80, 12 mg) have been obtained in soot extracts without a significant penalty in milligram yield when compared to control soot extracts (4% Sc3N@C80, 13 mg Sc3N@C80). The CAPTEAR process with Cu(NO3)2·2.5 H2O uses an exothermic nitrate moiety to suppress empty-cage fullerene formation, whereas Cu functions as a catalyst additive to offset the reactive plasma environment and boost the Sc3N@C80 MNF production. PMID:18052069

  4. Guided Discharge Path by Weak Ionized Region between Two Plasmas Produced by YAG Laser in Atmospheric Air Gap with Non-Uniform DC Electric Field

    NASA Astrophysics Data System (ADS)

    Okano, Daisuke

    1998-11-01

    Guided Discharge Path by Weak Ionized Region between Two Plasmas Produced by YAG Laser in Atmospheric Air Gap with Non-Uniform DC Electric Field*, Daisuke Okano, Kyushu Tokai University, 9-1-1 Toroku, Kumamoto, Japan. -----We have studied on guiding discharge path by weak ionized region between plasmas produced by a visible laser, that is, a YAG laser with wavelength 532nm, in an atmospheric air gap with DC non-uniform electric field using a rod-to-plate electrode. We succeeded in capturing the framing images in the temporal evolution on guiding discharge along the YAG laser light path. From the results of experiments, the region between two plasmas produced by a YAG laser can guide a discharge path, and the region between two plasmas on the laser light path is considered as well as a weak ionized one [1] produced by an excimer laser. [1]J.Sasaki, S.Kubodera, R.Ozaki and T.Uchiyama, J. Appl. Phys., 60 (1986) 3845. *This work was supported by Grant-in-Aid for Scientific Research (C)-no.10650295 of The Ministry of education, Science Sports and Culture in japan.

  5. Analysis of plasma protein adsorption onto DC-Chol-DOPE cationic liposomes by HPLC-CHIP coupled to a Q-TOF mass spectrometer.

    PubMed

    Capriotti, Anna Laura; Caracciolo, Giulio; Caruso, Giuseppe; Cavaliere, Chiara; Pozzi, Daniela; Samperi, Roberto; Laganà, Aldo

    2010-12-01

    Plasma protein adsorption is regarded as a key factor in the in vivo organ distribution of intravenously administered drug carriers, and strongly depends on vector surface characteristics. The present study aimed to characterize the "protein corona" absorbed onto DC-Chol-DOPE cationic liposomes. This system was chosen because it is one of the most efficient and widely used non-viral formulations in vitro and a potential candidate for in vivo transfection of genetic material. After incubation of human plasma with cationic liposomes, nanoparticle-protein complex was separated from plasma by centrifugation. An integrated approach based on protein separation by one-dimensional 12% polyacrylamide gel electrophoresis followed by the automated HPLC-Chip technology coupled to a high-resolution mass spectrometer was employed for protein corona characterization. Thirty gel lanes, approximately 2 mm, were cut, digested and analyzed by HPLC-MS/MS. Fifty-eight human plasma proteins adsorbed onto DC-Chol-DOPE cationic liposomes were identified. The knowledge of the interactions of proteins with liposomes can be exploited for future controlled design of colloidal drug carriers and possibly in the controlled creation of biocompatible surfaces of other devices that come into contact with proteins in body fluids.

  6. Preparation of Ag-containing diamond-like carbon films on the interior surface of tubes by a combined method of plasma source ion implantation and DC sputtering

    NASA Astrophysics Data System (ADS)

    Hatada, R.; Flege, S.; Bobrich, A.; Ensinger, W.; Dietz, C.; Baba, K.; Sawase, T.; Watamoto, T.; Matsutani, T.

    2014-08-01

    Adhesive diamond-like carbon (DLC) films can be prepared by plasma source ion implantation (PSII), which is also suitable for the treatment of the inner surface of a tube. Incorporation of a metal into the DLC film provides a possibility to change the characteristics of the DLC film. One source for the metal is DC sputtering. In this study PSII and DC sputtering were combined to prepare DLC films containing low concentrations of Ag on the interior surfaces of stainless steel tubes. A DLC film was deposited using a C2H4 plasma with the help of an auxiliary electrode inside of the tube. This electrode was then used as a target for the DC sputtering. A mixture of the gases Ar and C2H4 was used to sputter the silver. By changing the gas flow ratios and process time, the resulting Ag content of the films could be varied. Sample characterizations were performed by X-ray photoelectron spectroscopy, secondary ion mass spectrometry, atomic force microscopy and Raman spectroscopy. Additionally, a ball-on-disk test was performed to investigate the tribological properties of the films. The antibacterial activity was determined using Staphylococcus aureus bacteria.

  7. Cancer cells (MCF-7, Colo-357, and LNCaP) viability on amorphous hydrogenated carbon nitride film deposited by dielectric barrier discharge plasma

    SciTech Connect

    Majumdar, Abhijit; Hippler, Rainer; Ummanni, Ramesh; Walther, Reinhard; Schroeder, Karsten

    2009-08-01

    Atmospheric pressure dielectric barrier discharge plasma in CH{sub 4}/N{sub 2} (1:1) gas mixture has been employed to deposit amorphous hydrogenated carbon nitride (aH-CN{sub x}) film. In vitro studies with three different cancer cell lines were carried out on the coated surfaces. Preliminary biocompatibility and effect of CH{sub 4}/N{sub 2} films have been investigated by measuring cell proliferation. Three different cancer cell (MCF-7, Colo-357, and LNCaP) suspensions have been exposed on the surface of aH-CN{sub x} film to investigate the effect of deposited films on viability of cells. Results from the MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2- (4-sulfophenyl)-2H- tetrazolium, inner salt) proliferation assays indicated that the deposited aH-CN{sub x} film is cytotoxic to cancer cell lines. Time course cell viability assay indicated maximum cell death at 24 h after seeding the cells. This effect is dependant on physicochemical and mechanical properties of the deposited films. The deposited film has been characterized by x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The results confirm the presence of C-N, Cident toN, C-H{sub x}, C-O, N-O, overlapping NH, and OH bonds in the film.

  8. Cancer cells (MCF-7, Colo-357, and LNCaP) viability on amorphous hydrogenated carbon nitride film deposited by dielectric barrier discharge plasma

    NASA Astrophysics Data System (ADS)

    Majumdar, Abhijit; Ummanni, Ramesh; Schröder, Karsten; Walther, Reinhard; Hippler, Rainer

    2009-08-01

    Atmospheric pressure dielectric barrier discharge plasma in CH4/N2 (1:1) gas mixture has been employed to deposit amorphous hydrogenated carbon nitride (aH-CNx) film. In vitro studies with three different cancer cell lines were carried out on the coated surfaces. Preliminary biocompatibility and effect of CH4/N2 films have been investigated by measuring cell proliferation. Three different cancer cell (MCF-7, Colo-357, and LNCaP) suspensions have been exposed on the surface of aH-CNx film to investigate the effect of deposited films on viability of cells. Results from the MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H- tetrazolium, inner salt) proliferation assays indicated that the deposited aH-CNx film is cytotoxic to cancer cell lines. Time course cell viability assay indicated maximum cell death at 24 h after seeding the cells. This effect is dependant on physicochemical and mechanical properties of the deposited films. The deposited film has been characterized by x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The results confirm the presence of C-N, C≡N, C-Hx, C-O, N-O, overlapping NH, and OH bonds in the film.

  9. Large-area growth of multi-layer hexagonal boron nitride on polished cobalt foils by plasma-assisted molecular beam epitaxy

    PubMed Central

    Xu, Zhongguang; Tian, Hao; Khanaki, Alireza; Zheng, Renjing; Suja, Mohammad; Liu, Jianlin

    2017-01-01

    Two-dimensional (2D) hexagonal boron nitride (h-BN), which has a similar honeycomb lattice structure to graphene, is promising as a dielectric material for a wide variety of potential applications based on 2D materials. Synthesis of high-quality, large-size and single-crystalline h-BN domains is of vital importance for fundamental research as well as practical applications. In this work, we report the growth of h-BN films on mechanically polished cobalt (Co) foils using plasma-assisted molecular beam epitaxy. Under appropriate growth conditions, the coverage of h-BN layers can be readily controlled by growth time. A large-area, multi-layer h-BN film with a thickness of 5~6 nm is confirmed by Raman spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and transmission electron microscopy. In addition, the size of h-BN single domains is 20~100 μm. Dielectric property of as-grown h-BN film is evaluated by characterization of Co(foil)/h-BN/Co(contact) capacitor devices. Breakdown electric field is in the range of 3.0~3.3 MV/cm, which indicates that the epitaxial h-BN film has good insulating characteristics. In addition, the effect of substrate morphology on h-BN growth is discussed regarding different domain density, lateral size, and thickness of the h-BN films grown on unpolished and polished Co foils. PMID:28230178

  10. Cytocompatibility of amorphous hydrogenated carbon nitride films deposited by CH4/N2 dielectric barrier discharge plasmas with respect to cell lines

    NASA Astrophysics Data System (ADS)

    Majumdar, Abhijit; Schröder, Karsten; Hippler, Rainer

    2008-10-01

    Special amorphous hydrogenated carbon nitride (a-H-CNx) films have been prepared on glass substrates for the investigation of adhesion and proliferation of different mammalian cell lines. CH4/N2 dielectric barrier discharge plasmas were applied to deposit a-H-CNx coatings at half of the atmospheric pressure. Film quality was modified by varying the CH4:N2 ratio and deposition duration. Chemical composition was determined by x-ray photoelectron spectroscopy and Fourier transformed infrared spectroscopy. The N/C ratio was in the range of 0.20-0.55. A very small surface roughness was verified by atomic force microscopy. Human embryonic kidney (HEK) and rat adrenal pheochromocytoma (PC12) cells were cultivated on the a-H-CNx films to investigate the cytocompatibility of these surfaces. The microscopic images show that both kinds of cells lines were unable to survive. The cells did not adhere to the surfaces, and most of the cells died after certain time spans. Increased amounts of nitrogen in the film induce an accelerated cell death. It is concluded, that the deposited CNx film behaves cytotoxic to HEK and PC12 cell lines.

  11. Large-area growth of multi-layer hexagonal boron nitride on polished cobalt foils by plasma-assisted molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Xu, Zhongguang; Tian, Hao; Khanaki, Alireza; Zheng, Renjing; Suja, Mohammad; Liu, Jianlin

    2017-02-01

    Two-dimensional (2D) hexagonal boron nitride (h-BN), which has a similar honeycomb lattice structure to graphene, is promising as a dielectric material for a wide variety of potential applications based on 2D materials. Synthesis of high-quality, large-size and single-crystalline h-BN domains is of vital importance for fundamental research as well as practical applications. In this work, we report the growth of h-BN films on mechanically polished cobalt (Co) foils using plasma-assisted molecular beam epitaxy. Under appropriate growth conditions, the coverage of h-BN layers can be readily controlled by growth time. A large-area, multi-layer h-BN film with a thickness of 5~6 nm is confirmed by Raman spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and transmission electron microscopy. In addition, the size of h-BN single domains is 20~100 μm. Dielectric property of as-grown h-BN film is evaluated by characterization of Co(foil)/h-BN/Co(contact) capacitor devices. Breakdown electric field is in the range of 3.0~3.3 MV/cm, which indicates that the epitaxial h-BN film has good insulating characteristics. In addition, the effect of substrate morphology on h-BN growth is discussed regarding different domain density, lateral size, and thickness of the h-BN films grown on unpolished and polished Co foils.

  12. Large-area growth of multi-layer hexagonal boron nitride on polished cobalt foils by plasma-assisted molecular beam epitaxy.

    PubMed

    Xu, Zhongguang; Tian, Hao; Khanaki, Alireza; Zheng, Renjing; Suja, Mohammad; Liu, Jianlin

    2017-02-23

    Two-dimensional (2D) hexagonal boron nitride (h-BN), which has a similar honeycomb lattice structure to graphene, is promising as a dielectric material for a wide variety of potential applications based on 2D materials. Synthesis of high-quality, large-size and single-crystalline h-BN domains is of vital importance for fundamental research as well as practical applications. In this work, we report the growth of h-BN films on mechanically polished cobalt (Co) foils using plasma-assisted molecular beam epitaxy. Under appropriate growth conditions, the coverage of h-BN layers can be readily controlled by growth time. A large-area, multi-layer h-BN film with a thickness of 5~6 nm is confirmed by Raman spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and transmission electron microscopy. In addition, the size of h-BN single domains is 20~100 μm. Dielectric property of as-grown h-BN film is evaluated by characterization of Co(foil)/h-BN/Co(contact) capacitor devices. Breakdown electric field is in the range of 3.0~3.3 MV/cm, which indicates that the epitaxial h-BN film has good insulating characteristics. In addition, the effect of substrate morphology on h-BN growth is discussed regarding different domain density, lateral size, and thickness of the h-BN films grown on unpolished and polished Co foils.

  13. Tribological behaviour of plasma nitrided cast iron D6510 and cast steel S0050A under the inclined-impact sliding condition with extremely high contact pressure

    NASA Astrophysics Data System (ADS)

    Zhao, C.; Zhang, J.; Nie, X.

    2017-05-01

    Plasma nitriding as a surface modification was applied on two substrate materials: cast iron D6510 and cast steel S0050A. After measurement of the friction coefficients of the treated samples using a pin-on-disc tribotester, an inclined impact-sliding wear tester was utilized to investigate their tribological behaviour under tilting contact with extremely high contact pressure. While numerous surface fatigue cracks, severe chipping, and peeling of the compound layer were observed for the treated cast steel sample, the treated cast iron sample had far fewer surface fatigue cracks without chipping or peeling of the compound at the same test condition. The governing mechanisms of the treated cast iron sample’s superior resistance to surface fatigue failure were revealed by studying the cross-sectional hardness and nitrogen concentration profile. Energy-dispersive X-ray spectroscopy (EDS) analysis indicated that the treated cast iron sample had a smaller nitrogen concentration gradient, which led to a smaller hardness gradient as measured. The results suggest that a smaller hardness gradient between the compound layer and the diffusion zone and a thicker hardened case was able to improve the wear resistance and surface fatigue cracking resistance against high contact loads. Moreover, the smaller friction coefficient of the treated cast iron sample could also be beneficial for improving the wear resistance.

  14. Preparation of silicon carbide SiC-based nanopowders by the aerosol-assisted synthesis and the DC thermal plasma synthesis methods

    SciTech Connect

    Czosnek, Cezary; Bućko, Mirosław M.; Janik, Jerzy F.; Olejniczak, Zbigniew; Bystrzejewski, Michał; Łabędź, Olga; Huczko, Andrzej

    2015-03-15

    Highlights: • Make-up of the SiC-based nanopowders is a function of the C:Si:O ratio in precursor. • Two-stage aerosol-assisted synthesis offers conditions close to equilibrium. • DC thermal plasma synthesis yields kinetically controlled SiC products. - Abstract: Nanosized SiC-based powders were prepared from selected liquid-phase organosilicon precursors by the aerosol-assisted synthesis, the DC thermal plasma synthesis, and a combination of the two methods. The two-stage aerosol-assisted synthesis method provides at the end conditions close to thermodynamic equilibrium. The single-stage thermal plasma method is characterized by short particle residence times in the reaction zone, which can lead to kinetically controlled products. The by-products and final nanopowders were characterized by powder XRD, infrared spectroscopy FT-IR, scanning electron microscopy SEM, and {sup 29}Si MAS NMR spectroscopy. BET specific surface areas of the products were determined by standard physical adsorption of nitrogen at 77 K. The major component in all synthesis routes was found to be cubic silicon carbide β-SiC with average crystallite sizes ranging from a few to tens of nanometers. In some cases, it was accompanied by free carbon, elemental silicon or silica nanoparticles. The final mesoporous β-SiC-based nanopowders have a potential as affordable catalyst supports.

  15. Persistent Longitudinal Variations of Plasma Density and DC Electric Fields in the Low Latitude Ionosphere Observed with Probes on the C/NOFS Satellite

    NASA Technical Reports Server (NTRS)

    Pfaff, R.; Freudenreich, H.; Klenzing, J.; Rowland, D.; Liebrecht, C.; Bromund, K.; Roddy, P.

    2010-01-01

    Continuous measurements using in situ probes on consecutive orbits of the C/N0FS satellite reveal that the plasma density is persistently organized by longitude, in both day and night conditions and at all locations within the satellite orbit, defined by its perigee and apogee of 401 km and 867 km, respectively, and its inclination of 13 degrees. Typical variations are a factor of 2 or 3 compared to mean values. Furthermore, simultaneous observations of DC electric fields and their associated E x B drifts in the low latitude ionosphere also reveal that their amplitudes are also strongly organized by longitude in a similar fashion. The drift variations with longitude are particularly pronounced in the meridional component perpendicular to the magnetic field although they are also present in the zonal component as well. The longitudes of the peak meridional drift and density values are significantly out of phase with respect to each other. Time constants for the plasma accumulation at higher altitudes with respect to the vertical drift velocity must be taken into account in order to properly interpret the detailed comparisons of the phase relationship of the plasma density and plasma velocity variations. Although for a given period corresponding to that of several days, typically one longitude region dominates the structuring of the plasma density and plasma drift data, there is also evidence for variations organized about multiple longitudes at the same time. Statistical averages will be shown that suggest a tidal "wave 4" structuring is present in both the plasma drift and plasma density data. We interpret the apparent association of the modulation of the E x B drifts with longitude as well as that of the ambient plasma density as a manifestation of tidal forces at work in the low latitude upper atmosphere. The observations demonstrate how the high duty cycle of the C/NOFS observations and its unique orbit expose fundamental processes at work in the low latitude

  16. Experimental investigation of dielectric barrier discharge plasma actuators driven by repetitive high-voltage nanosecond pulses with dc or low frequency sinusoidal bias

    NASA Astrophysics Data System (ADS)

    Opaits, Dmitry F.; Likhanskii, Alexandre V.; Neretti, Gabriele; Zaidi, Sohail; Shneider, Mikhail N.; Miles, Richard B.; Macheret, Sergey O.

    2008-08-01

    Experimental studies were conducted of a flow induced in an initially quiescent room air by a single asymmetric dielectric barrier discharge driven by voltage waveforms consisting of repetitive nanosecond high-voltage pulses superimposed on dc or alternating sinusoidal or square-wave bias voltage. To characterize the pulses and to optimize their matching to the plasma, a numerical code for short pulse calculations with an arbitrary impedance load was developed. A new approach for nonintrusive diagnostics of plasma actuator induced flows in quiescent gas was proposed, consisting of three elements coupled together: the schlieren technique, burst mode of plasma actuator operation, and two-dimensional numerical fluid modeling. The force and heating rate calculated by a plasma model was used as an input to two-dimensional viscous flow solver to predict the time-dependent dielectric barrier discharge induced flow field. This approach allowed us to restore the entire two-dimensional unsteady plasma induced flow pattern as well as characteristics of the plasma induced force. Both the experiments and computations showed the same vortex flow structures induced by the actuator. Parametric studies of the vortices at different bias voltages, pulse polarities, peak pulse voltages, and pulse repetition rates were conducted experimentally. The significance of charge buildup on the dielectric surface was demonstrated. The charge buildup decreases the effective electric field in the plasma and reduces the plasma actuator performance. The accumulated surface charge can be removed by switching the bias polarity, which leads to a newly proposed voltage waveform consisting of high-voltage nanosecond repetitive pulses superimposed on a high-voltage low frequency sinusoidal voltage. Advantages of the new voltage waveform were demonstrated experimentally.

  17. Characteristics of silicon nitride deposited by VHF (162 MHz)-plasma enhanced chemical vapor deposition using a multi-tile push-pull plasma source

    NASA Astrophysics Data System (ADS)

    Kim, Ki Seok; Sirse, Nishant; Kim, Ki Hyun; Rogers Ellingboe, Albert; Kim, Kyong Nam; Yeom, Geun Young

    2016-10-01

    To prevent moisture and oxygen permeation into flexible organic electronic devices formed on substrates, the deposition of an inorganic diffusion barrier material such as SiN x is important for thin film encapsulation. In this study, by a very high frequency (162 MHz) plasma-enhanced chemical vapor deposition (VHF-PECVD) using a multi-tile push-pull plasma source, SiN x layers were deposited with a gas mixture of NH3/SiH4 with/without N2 and the characteristics of the plasma and the deposited SiN x film as the thin film barrier were investigated. Compared to a lower frequency (60 MHz) plasma, the VHF (162 MHz) multi-tile push-pull plasma showed a lower electron temperature, a higher vibrational temperature, and higher N2 dissociation for an N2 plasma. When a SiN x layer was deposited with a mixture of NH3/SiH4 with N2 at a low temperature of 100 °C, a stoichiometric amorphous Si3N4 layer with very low Si-H bonding could be deposited. The 300 nm thick SiN x film exhibited a low water vapor transmission rate of 1.18  ×  10-4 g (m2 · d)-1, in addition to an optical transmittance of higher than 90%.

  18. Effect of Low-Pressure Nitrogen DC Plasma Treatment on the Surface Properties of Biaxially Oriented Polypropylene, Poly (Methyl Methacrylate) and Polyvinyl Chloride Films

    NASA Astrophysics Data System (ADS)

    S. Hamideh, Mortazavi; Mahmood, Ghoranneviss; Soheil, Pilehvar; Sina, Esmaeili; Shamim, Zargham; S. Ebrahim, Hashemi; Hamzeh, Jodat

    2013-04-01

    In this study, commercial biaxially oriented polypropylene (BOPP), polyvinyl chloride (PVC) and poly (methyl methacrylate) (PMMA) films were treated with nitrogen plasma over different exposure times in a Pyrex tube surrounded by a DC variable magnetic field. The chemical changes that appeared on the surface of the samples were investigated using Fourier transform infrared (FT-IR) spectroscopy and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy after treatment for 2 min, 4 min and 6 min in a nitrogen plasma chamber. Effects of the plasma treatment on the surface topographies and contact angles of the untreated and plasma treated films were also analyzed by atomic force microscopy (AFM) and a contact angle measuring system. The results show that the plasma treated films become more hydrophilic with an enhanced wettability due to the formation of some new polar groups on the surface of the treated films. Moreover, at higher exposure times, the total surface energy in all treated films increased while a reduction in contact angle occurred. The behavior of surface roughness in each sample was completely different at higher exposure times.

  19. Growing c-axis oriented aluminum nitride films by Plasma-Enhanced Atomic Layer Deposition at low temperatures

    NASA Astrophysics Data System (ADS)

    Tarala, V.; Ambartsumov, M.; Altakhov, A.; Martens, V.; Shevchenko, M.

    2016-12-01

    The possibility of using plasma enhanced atomic layer deposition method for growing heteroepitaxial oriented AlN films on Si (100) and sapphire (001) substrates at temperatures less than 300 °C was investigated. The resulting samples were studied by X-ray diffraction analysis and ellipsometry. It has been shown that, ceteris paribus, AlN films grown on sapphire substrates have higher crystallinity than the samples grown on silicon wafers. With duration of plasma exposure of more than 20 s and at a temperature of 300 °C synthesized heteroepitaxial film had refractive index equal to 2.03±0.03. The X-ray diffraction scans feature (002) and (004) reflections at 2Θ equal to 35.7° and 75.9°, which are characteristic of hexagonal polytype of AlN. For the best sample, (002) reflection had full width on the half maximum of 162±11″

  20. Cobalt and iron segregation and nitride formation from nitrogen plasma treatment of CoFeB surfaces

    NASA Astrophysics Data System (ADS)

    Mattson, E. C.; Michalak, D. J.; Veyan, J. F.; Chabal, Y. J.

    2017-02-01

    Cobalt-iron-boron (CoFeB) thin films are the industry standard for ferromagnetic layers in magnetic tunnel junction devices and are closely related to the relevant surfaces of CoFe-based catalysts. Identifying and understanding the composition of their surfaces under relevant processing conditions is therefore critical. Here we report fundamental studies on the interaction of nitrogen plasma with CoFeB surfaces using infrared spectroscopy, x-ray photoemission spectroscopy, and low energy ion scattering. We find that, upon exposure to nitrogen plasma, clean CoFeB surfaces spontaneously reorganize to form an overlayer comprised of Fe2N3 and BN, with the Co atoms moved well below the surface through a chemically driven process. Subsequent annealing to 400 °C removes nitrogen, resulting in a Fe-rich termination of the surface region.

  1. Crystalline boron nitride aerogels

    DOEpatents

    Zettl, Alexander K.; Rousseas, Michael; Goldstein, Anna P.; Mickelson, William; Worsley, Marcus A.; Woo, Leta

    2017-04-04

    This disclosure provides methods and materials related to boron nitride aerogels. In one aspect, a material comprises an aerogel comprising boron nitride. The boron nitride has an ordered crystalline structure. The ordered crystalline structure may include atomic layers of hexagonal boron nitride lying on top of one another, with atoms contained in a first layer being superimposed on atoms contained in a second layer.

  2. Synthesis of metal nanoparticles by dual plasma electrolysis using atmospheric dc glow discharge in contact with liquid

    NASA Astrophysics Data System (ADS)

    Shirai, Naoki; Uchida, Satoshi; Tochikubo, Fumiyoshi

    2014-04-01

    For the synthesis of metal nanoparticles in aqueous solution, we propose dual plasma electrolysis, which consists of a Hoffman electrolysis apparatus with two atmospheric glow discharge plasmas as electrodes instead of conventional metal electrodes immersed in a liquid. The plasma anode irradiates positive ions to the solution surface while the plasma cathode irradiates electrons to the solution surface. The dual plasma electrolysis system enables us to simultaneously investigate the influence of electron and positive ion irradiation to a solution surface on metal nanoparticle generation at the same current. In this work, we used aqueous solutions of AgNO3, HAuCl4, and their mixture. In dual plasma electrolysis with AgNO3, Ag nanoparticles were only synthesized on the plasma cathode side. This means that Ag nanoparticles are generated via the reduction of Ag+ by electrons. With HAuCl4 solution, Au nanoparticles were synthesized on both the plasma anode and plasma cathode sides. Ion irradiation with the plasma anode is more effective than electron irradiation for Au nanoparticle synthesis. This finding suggests that positive ions from the plasma trigger the dissociative reaction of AuCl4- at the plasma-liquid interface. When a AgNO3-HAuCl4 mixture was used, the synthesized nanoparticles have a structure consisting of a Au core covered with a Ag shell.

  3. Study of selective chemical downstream plasma etching of silicon nitride and silicon oxide for advanced patterning applications

    NASA Astrophysics Data System (ADS)

    Prévost, Emilie; Cunge, Gilles; De-Buttet, Côme; Lagrasta, Sebastien; Vallier, Laurent; Petit-Etienne, Camille

    2017-03-01

    The evolution of integrated components in the semiconductors industry is nowadays looking for ultra-high selective etching processes in order to etch high aspect ratio structures in complicated stacks of ultrathin layers. For ultra-high selective processes, typical plasma etching show limitations, while wet etching processes reach limitations due to capillary forces. For these reasons there is a great regain of interest today in chemical downstream etching systems (CDE), which combine the advantages of plasma and wet treatments. The absence of photons and ions allow to minimize damages and to achieve very high selectivity (in isotropic etching). In this work we investigated the parameters enabling to etch selectively the Si3N4 to the SiO2 by CDE. We shown that the correlation between the gas mixture and the wafer temperature is the key to obtain the desired selectivity. In order to optimize the processing window, the mixture composition (NF3/N2/O2/He) and the temperatures were screened by several DOE (Designs Of Experiments). Conditions are found in which the etching selectivity between the two silicon alloys is higher than 100, which allowed us to clean out sacrificial Si3N4 layers in very high aspect ratio (about 100) silicon trenches of nanometric size (60nm) without damaging the 10nm thin SiO2 caping layer (between the Si and the Si3N4). This demonstrates that downstream plasma etching can perform better than wet treatments in this case.

  4. Photodetectors using III-V nitrides

    DOEpatents

    Moustakas, T.D.; Misra, M.

    1997-10-14

    A photodetector using a III-V nitride and having predetermined electrical properties is disclosed. The photodetector includes a substrate with interdigitated electrodes formed on its surface. The substrate has a sapphire base layer, a buffer layer formed from a III-V nitride and a single crystal III-V nitride film. The three layers are formed by electron cyclotron resonance microwave plasma-assisted molecular beam epitaxy (ECR-assisted MBE). Use of the ECR-assisted MBE process allows control and predetermination of the electrical properties of the photodetector. 24 figs.

  5. Photodetectors using III-V nitrides

    DOEpatents

    Moustakas, Theodore D.; Misra, Mira

    1997-01-01

    A photodetector using a III-V nitride and having predetermined electrical properties is disclosed. The photodetector includes a substrate with interdigitated electrodes formed on its surface. The substrate has a sapphire base layer, a buffer layer formed from a III-V nitride and a single crystal III-V nitride film. The three layers are formed by electron cyclotron resonance microwave plasma-assisted molecular beam epitaxy (ECR-assisted MBE). Use of the ECR-assisted MBE process allows control and predetermination of the electrical properties of the photodetector.

  6. Plasma assisted surface coating/modification processes - An emerging technology

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1987-01-01

    A broad understanding of the numerous ion or plasma assisted surface coating/modification processes is sought. An awareness of the principles of these processes is needed before discussing in detail the ion nitriding technology. On the basis of surface modifications arising from ion or plasma energizing and interactions, it can be broadly classified as deposition of distinct overlay coatings (sputtering-dc, radio frequency, magnetron, reactive; ion plating-diode, triode) and surface property modification without forming a discrete coating (ion implantation, ion beam mixing, laser beam irradiation, ion nitriding, ion carburizing, plasma oxidation. These techniques offer a great flexibility and are capable in tailoring desirable chemical and structural surface properties independent of the bulk properties.

  7. Plasma assisted surface coating/modification processes: An emerging technology

    NASA Astrophysics Data System (ADS)

    Spalvins, T.

    A broad understanding of the numerous ion or plasma assisted surface coating/modification processes is sought. An awareness of the principles of these processes is needed before discussing in detail the ion nitriding technology. On the basis of surface modifications arising from ion or plasma energizing and interactions, it can be broadly classified as deposition of distinct overlay coatings (sputtering-dc, radio frequency, magnetron, reactive; ion plating-diode, triode) and surface property modification without forming a discrete coating (ion implantation, ion beam mixing, laser beam irradiation, ion nitriding, ion carburizing, plasma oxidation). These techniques offer a great flexibility and are capable in tailoring desirable chemical and structural surface properties independent of the bulk properties.

  8. Plasma assisted surface coating/modification processes - An emerging technology

    NASA Astrophysics Data System (ADS)

    Spalvins, T.

    A broad understanding of the numerous ion or plasma assisted surface coating/modification processes is sought. An awareness of the principles of these processes is needed before discussing in detail the ion nitriding technology. On the basis of surface modifications arising from ion or plasma energizing and interactions, it can be broadly classified as deposition of distinct overlay coatings (sputtering-dc, radio frequency, magnetron, reactive; ion plating-diode, triode) and surface property modification without forming a discrete coating (ion implantation, ion beam mixing, laser beam irradiation, ion nitriding, ion carburizing, plasma oxidation. These techniques offer a great flexibility and are capable in tailoring desirable chemical and structural surface properties independent of the bulk properties.

  9. Plasma assisted surface coating/modification processes - An emerging technology

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1987-01-01

    A broad understanding of the numerous ion or plasma assisted surface coating/modification processes is sought. An awareness of the principles of these processes is needed before discussing in detail the ion nitriding technology. On the basis of surface modifications arising from ion or plasma energizing and interactions, it can be broadly classified as deposition of distinct overlay coatings (sputtering-dc, radio frequency, magnetron, reactive; ion plating-diode, triode) and surface property modification without forming a discrete coating (ion implantation, ion beam mixing, laser beam irradiation, ion nitriding, ion carburizing, plasma oxidation. These techniques offer a great flexibility and are capable in tailoring desirable chemical and structural surface properties independent of the bulk properties.

  10. Plasma assisted surface coating/modification processes: An emerging technology

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1986-01-01

    A broad understanding of the numerous ion or plasma assisted surface coating/modification processes is sought. An awareness of the principles of these processes is needed before discussing in detail the ion nitriding technology. On the basis of surface modifications arising from ion or plasma energizing and interactions, it can be broadly classified as deposition of distinct overlay coatings (sputtering-dc, radio frequency, magnetron, reactive; ion plating-diode, triode) and surface property modification without forming a discrete coating (ion implantation, ion beam mixing, laser beam irradiation, ion nitriding, ion carburizing, plasma oxidation). These techniques offer a great flexibility and are capable in tailoring desirable chemical and structural surface properties independent of the bulk properties.

  11. Analytical study of whistler mode waves in presence of parallel DC electric field for relativistic plasma in the magnetosphere of Uranus

    NASA Astrophysics Data System (ADS)

    Pandey, R. S.; Kaur, Rajbir

    2016-10-01

    In present paper, field aligned whistler mode waves are analyzed, in the presence of DC field in background plasma having relativistic distribution function in the magnetosphere of Uranus. The work has been examined for relativistic Maxwellian and loss-cone distribution function. In both the cases, we have studied the effect of various plasma parameters on the growth rate of waves by using the method of characteristics and discussed using data provided by Voyager 2. Growth rate has increased by increasing the magnitude of electric field, temperature anisotropy, energy density and number density of particles for Maxwellian and loss-cone background. However, when relativistic factor (λ =√{ 1 -v2 /c2 }) increases, growth rate decreases. The significant increase in real frequency of whistler waves can be observed. The results can be used for comparative study of planetary magnetospheres. The derivation can also be adapted to study various other instabilities in magnetosphere of Uranus.

  12. Boron nitride composites

    DOEpatents

    Kuntz, Joshua D.; Ellsworth, German F.; Swenson, Fritz J.; Allen, Patrick G.

    2017-02-21

    According to one embodiment, a composite product includes: a matrix material including hexagonal boron nitride and one or more borate binders; and a plurality of cubic boron nitride particles dispersed in the matrix material. According to another embodiment, a composite product includes: a matrix material including hexagonal boron nitride and amorphous boron nitride; and a plurality of cubic boron nitride particles dispersed in the matrix material.

  13. Plasma-Enhanced Atomic Layer Deposition of Ruthenium-Titanium Nitride Mixed-Phase Layers for Direct-Plate Liner and Copper Diffusion Barrier Applications

    NASA Astrophysics Data System (ADS)

    Gildea, Adam James

    Current interconnect networks in semiconductor processing utilize a sputtered TaN diffusion barrier, Ta liner, and Cu seed to improve the adhesion, microstructure, and electromigration resistance of electrochemically deposited copper that fills interconnect wires and vias. However, as wire/via widths shrink due to device scaling, it becomes increasingly difficult to have the volume of a wire/via be occupied with ECD Cu which increases line resistance and increases the delay in signal propagation in IC chips. A single layer that could serve the purpose of a Cu diffusion barrier and ECD Cu adhesion promoter could allow ECD Cu to occupy a larger volume of a wire/via, leading to a decrease in line resistance and decrease in signal delay. Previous work has shown RuTaN, RuWCN, and RuCo films can act as Cu diffusion barriers and be directly platable to thickness of 2-3nm. However, other material selections may prove as effective or possibly better. Mixed-phase films of ruthenium titanium nitride grown by atomic layer deposition (ALD) were investigated for their performance as a Cu diffusion barrier and as a surface for the direct plating of ECD Cu. All Ru was deposited by plasma-enhanced atomic layer deposition (PEALD) while TiN was deposited by either thermal ALD or PEALD. RuTiN, films with thermal ALD TiN and a Ru:Ti of 20:1 showed barrier performance comparable to PVD TaN at 3-4 nm thickness and 15 nm planar films were directly platable. Follow up work is certainly needed for this material set, yet initial results indicate RuTiN could serve as an effective direct plate liner for Cu interconnects.

  14. Characterization and properties of highly adhesive titanium nitride and tungsten nitride thin films

    NASA Astrophysics Data System (ADS)

    Martev, I. N.; Dechev, D. A.; Ivanov, N. P.; Uzunov, T. D.; Kashchieva, E. P.

    2008-05-01

    The paper presents results on the physical characteristics and mechanical properties of titanium nitride (TiN) and tungsten nitride (W2N) thin films grown by reactive DC magnetron sputtering. The films were deposited in a system with several magnetron modules of different sputtering materials suitable for deposition of single-layer metal nitride films and multilayer nitride coatings. The deposition conditions were optimized to obtain films with the highest adhesion to substrates of machine steel and sintered hard alloy. The adhesion of the films was measured in dependence on two principal process parameters: the nitrogen partial pressure in the magnetron discharge gas mixture of nitrogen and argon and the substrate temperature. The composition of the TiN films was determined by Auger electron spectroscopy. The microstructure and the crystallization trend of the films were studied by transmission electron microscopy and selected area electron diffraction. The hardness of the films was examined using standard measuring methods.

  15. Comparative band alignment of plasma-enhanced atomic layer deposited high-k dielectrics on gallium nitride

    NASA Astrophysics Data System (ADS)

    Yang, Jialing; Eller, Brianna S.; Zhu, Chiyu; England, Chris; Nemanich, Robert J.

    2012-09-01

    Al2O3 films, HfO2 films, and HfO2/Al2O3 stacked structures were deposited on n-type, Ga-face, GaN wafers using plasma-enhanced atomic layer deposition (PEALD). The wafers were first treated with a wet-chemical clean to remove organics and an in-situ combined H2/N2 plasma at 650 °C to remove residual carbon contamination, resulting in a clean, oxygen-terminated surface. This cleaning process produced slightly upward band bending of 0.1 eV. Additional 650 °C annealing after plasma cleaning increased the upward band bending by 0.2 eV. After the initial clean, high-k oxide films were deposited using oxygen PEALD at 140 °C. The valence band and conduction band offsets (VBOs and CBOs) of the Al2O3/GaN and HfO2/GaN structures were deduced from in-situ x-ray and ultraviolet photoemission spectroscopy (XPS and UPS). The valence band offsets were determined to be 1.8 and 1.4 eV, while the deduced conduction band offsets were 1.3 and 1.0 eV, respectively. These values are compared with the theoretical calculations based on the electron affinity model and charge neutrality level model. Moreover, subsequent annealing had little effect on these offsets; however, the GaN band bending did change depending on the annealing and processing. An Al2O3 layer was investigated as an interfacial passivation layer (IPL), which, as results suggest, may lead to improved stability, performance, and reliability of HfO2/IPL/GaN structures. The VBOs were ˜0.1 and 1.3 eV, while the deduced CBOs were 0.6 and 1.1 eV for HfO2 with respect to Al2O3 and GaN, respectively.

  16. Zinc oxide based nanocomposite thin film electrodes and the effect of D.C. plasma oxidation power on discharge capacity for lithium ion batteries.

    PubMed

    Akbulut, Hatem; Guler, Mehmet Oguz; Aydin, Yasemin

    2012-12-01

    Zinc oxide based thin films have been grown on glass and stainless steel substrates in two steps; thermal evaporation from high purity metallic zinc and D.C. plasma oxidation. X-ray diffraction has shown that the films were polycrystalline nature and small predominant orientation at some specific planes. Analysis showed that plasma oxidation starts from the thermally evaporated leaf-like surfaces and produces a core-shell structure of ZnO on the metallic Zn. Increasing plasma oxidation power causes increased amount of ZnO volume and resistivity. Coin-type (CR2016) test cells were assembled in an argon-filled glove box and cyclically tested. The electrochemical performance of the films has been studied by cyclic voltammetry. The dependence of converted Li-ions on voltage profile of the films has been determined. It was found that the Zn/ZnO films exhibited highest the number of converted Li-ions at 175 W plasma oxidation conditions. Discharge capacity measurements revealed the double phase structures of Zn/ZnO exhibited significantly high reversible capacities. The high capacity and low capacity fade values were attributed to the high electrical conductivity and buffering ability of metallic Zn in the anodes.

  17. Prediction of plasma-induced damage distribution during silicon nitride etching using advanced three-dimensional voxel model

    SciTech Connect

    Kuboi, Nobuyuki Tatsumi, Tetsuya; Kinoshita, Takashi; Shigetoshi, Takushi; Fukasawa, Masanaga; Komachi, Jun; Ansai, Hisahiro

    2015-11-15

    The authors modeled SiN film etching with hydrofluorocarbon (CH{sub x}F{sub y}/Ar/O{sub 2}) plasma considering physical (ion bombardment) and chemical reactions in detail, including the reactivity of radicals (C, F, O, N, and H), the area ratio of Si dangling bonds, the outflux of N and H, the dependence of the H/N ratio on the polymer layer, and generation of by-products (HCN, C{sub 2}N{sub 2}, NH, HF, OH, and CH, in addition to CO, CF{sub 2}, SiF{sub 2}, and SiF{sub 4}) as ion assistance process parameters for the first time. The model was consistent with the measured C-F polymer layer thickness, etch rate, and selectivity dependence on process variation for SiN, SiO{sub 2}, and Si film etching. To analyze the three-dimensional (3D) damage distribution affected by the etched profile, the authors developed an advanced 3D voxel model that can predict the time-evolution of the etched profile and damage distribution. The model includes some new concepts for gas transportation in the pattern using a fluid model and the property of voxels called “smart voxels,” which contain details of the history of the etching situation. Using this 3D model, the authors demonstrated metal–oxide–semiconductor field-effect transistor SiN side-wall etching that consisted of the main-etch step with CF{sub 4}/Ar/O{sub 2} plasma and an over-etch step with CH{sub 3}F/Ar/O{sub 2} plasma under the assumption of a realistic process and pattern size. A large amount of Si damage induced by irradiated hydrogen occurred in the source/drain region, a Si recess depth of 5 nm was generated, and the dislocated Si was distributed in a 10 nm deeper region than the Si recess, which was consistent with experimental data for a capacitively coupled plasma. An especially large amount of Si damage was also found at the bottom edge region of the metal–oxide–semiconductor field-effect transistors. Furthermore, our simulation results for bulk fin-type field-effect transistor side-wall etching

  18. Determination of impurities in titanium nitride by slurry introduction axial viewed inductively coupled plasma optical emission spectrometry

    NASA Astrophysics Data System (ADS)

    Wang, Zheng; Ni, Zheming; Qiu, Deren; Tao, Guangyi; Yang, Pengyuan

    2005-03-01

    A method of slurry nebulization for inductively coupled plasma optical emission spectrometry (ICP-OES) applied to the analysis of titanium niride(TiN) was reported. The TiN slurry sample was prepared with adding dispersant polyacrylate amine or polyethylene imine for the stabilization and homogenization of suspension, and the amount of additives was optimized. A Babington type cross-flow nebulizer with V-groove was used for nebulization of the slurry for avoidance of blockage from the particles. The stability of slurry was characterized via zeta potential measurement, scanning electron microscope observation, particle size distrbution measurement and signal stability testing. For nm size TiN, calibration curves could be established by aqueous standards and the analytical results were in good accordance with the alkaline fusion method. For μm size TiN, a negative deviation was observed for most of elements and this deviation can be corrected by using Ti intrinsic internal standard method.

  19. Systematic Study of p-type Doping and Related Defects in III-Nitrides: Pathway toward a Nitride HBT

    DTIC Science & Technology

    2012-11-20

    16 Although beneficial for LEDs, lateral surface segregation of indium is detrimental for nitride solar cells and laser diodes , where recombination...1009 (2007). 44 S. D. Burnham, Improved Understanding and Control of Magnesium-Doped Gallium Nitride by Plasma Assisted Molecular Beam Epitaxy, in...mobility, and strong light absorption.1-3 Together these attributes make III- nitrides suited for light-emitting diodes (LEDs), high electron

  20. Improved oxygen diffusion barrier properties of ruthenium-titanium nitride thin films prepared by plasma-enhanced atomic layer deposition.

    PubMed

    Jeong, Seong-Jun; Kim, Doo-In; Kim, Sang Ouk; Han, Tae Hee; Kwon, Jung-Dae; Park, Jin-Seong; Kwon, Se-Hun

    2011-01-01

    Ru-TiN thin films were prepared from bis(ethylcyclopentadienyl)ruthenium and tetrakis(dimethylamino)titanium using plasma-enhanced atomic layer deposition (PEALD). The Ru and TiN were deposited sequentially to intermix TiN with Ru. The composition of Ru-TiN films was controlled precisely by changing the number of deposition cycles allocated to Ru, while fixing the number of deposition cycles allocated to TiN. Although both Ru and TiN thin films have a polycrystalline structure, the microstructure of the Ru-TiN films changed from a TiN-like polycrystalline structure to a nanocrystalline on increasing the Ru intermixing ratio. Moreover, the electrical resistivity of the Ru0.67-TiN0.33 thin films is sufficiently low at 190 microomega x cm and was maintained even after O2 annealing at 750 degrees C. Therefore, Ru-TiN thin films can be utilized as a oxygen diffusion barrier material for future dynamic (DRAM) and ferroelectric (FeRAM) random access memory capacitors.

  1. Recent developments in nitride chemistry

    SciTech Connect

    Niewa, R.; DiSalvo, F.J.

    1998-10-01

    The chemistry of ternary nitrides is reviewed with special focus on developments of the last two years (1996 and 1997). In particular, structures and properties of ternary and higher transition metal nitrides, main group nitrides, subnitrides, and nitride halides are compared, and a section on thermodynamics of ternary nitrides is included. Finally, methods for the preparation of gallium nitride single crystals are summarized.

  2. Comment on: "Characterization of Microroughness Parameters in Titanium Nitride Thin Films Grown by DC Magnetron Sputtering" [J Fusion Energ DOI 10.1007/s10894-012-9510-z

    NASA Astrophysics Data System (ADS)

    Solaymani, Shahram; Ghaderi, Atefeh; Nezafat, Negin Beryani

    2012-12-01

    In recent article [Ali Gelali. Azin Ahmadpourian. Reza Bavadi. M. R. Hantehzadeh. Arman Ahmadpourian. J Fusion Energ DOI 10.1007/s10894-012-9510-z], Ali Geleli et al. studied the PSD and RMS Roughness parameters in Titanium Nitride thin films by AFM data and used the computed fractal dimension value of micrographs to describe the surface morphology of thin films. Here, the correct form of equations and relationship between PSD and RMS will be discussed.

  3. Internal quantum efficiency of III-nitride quantum dot superlattices grown by plasma-assisted molecular-beam epitaxy

    SciTech Connect

    Gacevic, Z.; Kehagias, Th.; Koukoula, T.; Komninou, Ph.

    2011-05-15

    We present a study of the optical properties of GaN/AlN and InGaN/GaN quantum dot (QD) superlattices grown via plasma-assisted molecular-beam epitaxy, as compared to their quantum well (QW) counterparts. The three-dimensional/two-dimensional nature of the structures has been verified using atomic force microscopy and transmission electron microscopy. The QD superlattices present higher internal quantum efficiency as compared to the respective QWs as a result of the three-dimensional carrier localization in the islands. In the QW samples, photoluminescence (PL) measurements point out a certain degree of carrier localization due to structural defects or thickness fluctuations, which is more pronounced in InGaN/GaN QWs due to alloy inhomogeneity. In the case of the QD stacks, carrier localization on potential fluctuations with a spatial extension smaller than the QD size is observed only for the InGaN QD-sample with the highest In content (peak emission around 2.76 eV). These results confirm the efficiency of the QD three-dimensional confinement in circumventing the potential fluctuations related to structural defects or alloy inhomogeneity. PL excitation measurements demonstrate efficient carrier transfer from the wetting layer to the QDs in the GaN/AlN system, even for low QD densities ({approx}10{sup 10} cm{sup -3}). In the case of InGaN/GaN QDs, transport losses in the GaN barriers cannot be discarded, but an upper limit to these losses of 15% is deduced from PL measurements as a function of the excitation wavelength.

  4. Structure and properties of nitrides on the surface of collagen

    NASA Astrophysics Data System (ADS)

    Mironov, M. M.; Grebenshchikova, M. M.

    2017-01-01

    A study of the structure and composition of titanium and hafnium nitride coatings, deposited by condensation from plasma phase, on the leather by methods of scanning electron microscopy and x-ray fluorescence analysis. Nanostructured nitride coatings don’t degrade the properties of the leather and also inhibits the growth of pathogenic microflora and slow the migration of chromium ions.

  5. Effect of Si on DC arc plasma generation from Al-Cr and Al-Cr-Si cathodes used in oxygen

    NASA Astrophysics Data System (ADS)

    Zhirkov, I.; Landälv, L.; Göthelid, E.; Ahlgren, M.; Eklund, P.; Rosen, J.

    2017-02-01

    Al2O3 alloyed with Cr is an important material for the tooling industry. It can be synthesized from an arc discharge using Al-Cr cathodes in an oxygen atmosphere. Due to formation of Al-rich oxide islands on the cathode surface, the arc process stability is highly sensitive to oxygen pressure. For improved stability, the use of Al0.70Cr0.25Si0.05 cathodes has previously been suggested, where Si may reduce island formation. Here, we have investigated the effect of Si by comparing plasma generation and thin film deposition from Al0.7Cr0.3 and Al0.7Cr0.25Si0.05 cathodes. Plasma ion composition, ion energies, ion charge states, neutral species, droplet formation, and film composition have been characterized at different O2 flow rates for arc currents of 60 and 90 A. Si and related compounds are detected in plasma ions and in plasma neutrals. Scanning electron microscopy and energy dispersive X-ray analysis show that the cathode composition and the film composition are the same, with Si present in droplets as well. The effect of Si on the process stability, ion energies, and ion charge states is found to be negligible compared to that of the arc current. The latter is identified as the most relevant parameter for tuning the properties of the reactive discharge. The present work increases the fundamental understanding of plasma generation in a reactive atmosphere, and provides input for the choice of cathode composition and process parameters in reactive DC arc synthesis.

  6. Investigation into nitrided spur gears

    SciTech Connect

    Yilbas, B.S.; Coban, A.; Nickel, J.; Sunar, M.; Sami, M.; Abdul Aleem, B.J.

    1996-12-01

    The cold forging method has been widely used in industry to produce machine parts. In general, gears are produced by shaping or hobbing. One of the shaping techniques is precision forging, which has several advantages over hobbing. In the present study, cold forging of spur gears from Ti-6Al-4V material is introduced. To improve the surface properties of the resulting gears, plasma nitriding was carried out. Nuclear reaction analysis was carried out to obtain the nitrogen concentration, while the micro-PIXE technique was used to determine the elemental distribution in the matrix after forging and nitriding processes. Scanning electron microscopy and x-ray powder diffraction were used to investigate the metallurgical changes and formation of nitride components in the surface region. Microhardness and friction tests were carried out to measure the hardness depth profile and friction coefficient at the surface. Finally, scoring failure tests were conducted to determine the rotational speed at which the gears failed. Three distinct regions were obtained in the nitride region, and at the initial stages of the scoring tests, failure in surface roughness was observed in the vicinity of the tip of the gear tooth. This occurred at a particular rotational speed and work input.

  7. Investigation into nitrided spur gears

    NASA Astrophysics Data System (ADS)

    Yilbas, B. S.; Coban, A.; Nickel, J.; Sunar, M.; Sami, M.; Aleem, B. J. Abdul

    1996-12-01

    The cold forging method has been widely used in industry to produce machine parts. In general, gears are produced by shaping or hobbing. One of the shaping techniques is precision forging, which has several advantages over hobbing. In the present study, cold forging of spur gears from Ti-6A1-4V material is introduced. To improve the surface properties of the resulting gears, plasma nitriding was carried out. Nuclear reaction analysis was carried out to obtain the nitrogen concentration, while the micro-PIXE technique was used to determine the elemental distribution in the matrix after forging and nitriding processes. Scanning electron microscopy and x-ray powder diffraction were used to investigate the metallurgical changes and formation of nitride components in the surface region. Microhardness and friction tests were carried out to measure the hardness depth profile and friction coefficient at the surface. Finally, scoring failure tests were conducted to determine the rotational speed at which the gears failed. Three distinct regions were obtained in the nitride region, and at the initial stages of the scoring tests, failure in surface roughness was observed in the vicinity of the tip of the gear tooth. This occurred at a particular rotational speed and work input.

  8. Preparation of Carbon-Doped TiO2 Nanopowder Synthesized by Droplet Injection of Solution Precursor in a DC-RF Hybrid Plasma Flow System

    NASA Astrophysics Data System (ADS)

    Jang, Juyong; Takana, Hidemasa; Ando, Yasutaka; Solonenko, Oleg P.; Nishiyama, Hideya

    2013-08-01

    Carbon-doped titanium dioxide nanopowder has received much attention because of its higher photocatalytic performance, which is practically activated not only by UV, but also by visible light irradiation. In the present study, C-TiO2 nanopowder was synthesized by droplet injection of solution precursor in a DC-RF hybrid plasma flow system, resulting in higher photocatalytic performance even under visible light irradiation. In-flight C-TiO2 nanoparticles reacted with the high concentration of carbon in plasma flow and were then deposited on the surfaces of two quartz tubes in the upstream and downstream regions of this system. The collected C-TiO2 nanopowder contained anatase-rutile mixed-phase TiO2 and TiC, the contents of which depended on the location of the powder collection, the temperature, and the duration of plasma treatment. Highly functional C-TiO2 nanopowder collected in the downstream region exhibited a higher degradation rate of methylene blue than that of single-phase anatase TiO2, even under visible light irradiation, in spite of being TiC.

  9. Study of sterilization-treatment in pure and N- doped carbon thin films synthesized by inductively coupled plasma assisted pulsed-DC magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Javid, Amjed; Kumar, Manish; Han, Jeon Geon

    2017-01-01

    Electrically-conductive nanocrystalline carbon films, having non-toxic and non-immunogenic characteristics, are promising candidates for reusable medical devices. Here, the pure and N- doped nanocrystalline carbon films are deposited by the assistance of inductively coupled plasma (ICP) in an unbalanced facing target pulsed-DC magnetron sputtering process. Through the optical emission spectroscopy study, the role of ICP assistance and N-doping on the reactive components/radicals during the synthesis is presented. The N-doping enhances the three fold bonding configurations by increasing the ionization and energies of the plasma species. Whereas, the ICP addition increases the plasma density to control the deposition rate and film structure. As a result, sputtering-throughput (deposition rate: 31-55 nm/min), electrical resistivity (4-72 Ωcm) and water contact angle (45.12°-54°) are significantly tailored. Electric transport study across the surface microchannel confirms the superiority of N-doped carbon films for sterilization stability over the undoped carbon films.

  10. Magnetoresistance measurements of superconducting molybdenum nitride thin films

    SciTech Connect

    Baskaran, R. Arasu, A. V. Thanikai; Amaladass, E. P.

    2016-05-23

    Molybdenum nitride thin films have been deposited on aluminum nitride buffered glass substrates by reactive DC sputtering. GIXRD measurements indicate formation of nano-crystalline molybdenum nitride thin films. The transition temperature of MoN thin film is 7.52 K. The transition width is less than 0.1 K. The upper critical field Bc{sub 2}(0), calculated using GLAG theory is 12.52 T. The transition width for 400 µA current increased initially upto 3 T and then decreased, while that for 100 µA current transition width did not decrease.

  11. The use of ion chromatography-dc plasma atomic emission spectrometry for the speciation of trace metals. Annual performance report, February 1, 1989--January 31, 1992

    SciTech Connect

    Urasa, I.T.

    1991-09-20

    The original objects of this research program were: to interface d.c. plasma atomic emission spectrometer with an ion chromatograph; to characterize and optimize the combined systems for application in the speciation of metals in aqueous solutions; to use this system in the study of the solution chemistry of various metals; and to find ways in which the measurement sensitivity of the method can be enhanced, thereby allowing the detection of metal species at low ppb concentration levels. This approach has been used to study the chemistry of and speciate several elements in solution including: arsenic, chromium, iron, manganese, nickel phosphorus, platinum, selenium, and vanadium. During the course of this research, we have found that the solution chemistry of the elements studied and the speciation data obtained can vary considerably depending on the solution, and the chromatographic conditions employed. The speciation of chromium, iron, and vanadium was found to be highly influenced by the acidity of the sample. The element selective nature of the d.c. plasma detector allows these changes to be monitored, thereby providing quantitative information on the new moieties formed. New approaches are being developed including the use of chelating ligands as preconcentration agents for purposes of reducing further the detection limits of the elements of interest and to improve the overall element speciation scheme. New thrusts are being directed towards the employment of post-column derivatization method coupled with colorimetric measurements to detect and quantify metal species eluting from the chromatographic column. The influence of sample acidity on these investigations will be carefully evaluated. These new thrusts are described in the accompanying Project Renewal Proposal.

  12. Titanium Nitride Cermets

    DTIC Science & Technology

    1952-07-01

    7696i ’-Brewer, L., et al. Thermodynamic and Physical Properties of Nitrides. Carbides, Sulfides, i1licides, and Phosphides, Chemistry and Metallurgy of...12 Referen eCs 0 . ...................... • • • 14 WADC TR 52-155 iv LIST OF TABLES I Properties of Titanium Nitride Bodies...15 II Properties of Titanium Nitride-Nickel Bodies............16 III Properties of Titanium Nitride Cermets with Nickel,..... 17 Cobalt, and

  13. Bidirectional DC/DC Converter

    NASA Astrophysics Data System (ADS)

    Pedersen, F.

    2008-09-01

    The presented bidirectional DC/DC converter design concept is a further development of an already existing converter used for low battery voltage operation.For low battery voltage operation a high efficient low parts count DC/DC converter was developed, and used in a satellite for the battery charge and battery discharge function.The converter consists in a bidirectional, non regulating DC/DC converter connected to a discharge regulating Buck converter and a charge regulating Buck converter.The Bidirectional non regulating DC/DC converter performs with relatively high efficiency even at relatively high currents, which here means up to 35Amps.This performance was obtained through the use of power MOSFET's with on- resistances of only a few mille Ohms connected to a special transformer allowing paralleling several transistor stages on the low voltage side of the transformer. The design is patent protected. Synchronous rectification leads to high efficiency at the low battery voltages considered, which was in the range 2,7- 4,3 Volt DC.The converter performs with low switching losses as zero voltage zero current switching is implemented in all switching positions of the converter.Now, the drive power needed, to switch a relatively large number of low Ohm , hence high drive capacitance, power MOSFET's using conventional drive techniques would limit the overall conversion efficiency.Therefore a resonant drive consuming considerable less power than a conventional drive circuit was implemented in the converter.To the originally built and patent protected bidirectional non regulating DC/DC converter, is added the functionality of regulation.Hereby the need for additional converter stages in form of a Charge Buck regulator and a Discharge Buck regulator is eliminated.The bidirectional DC/DC converter can be used in connection with batteries, motors, etc, where the bidirectional feature, simple design and high performance may be useful.

  14. Preparation of uranium nitride

    DOEpatents

    Potter, Ralph A.; Tennery, Victor J.

    1976-01-01

    A process for preparing actinide-nitrides from massive actinide metal which is suitable for sintering into low density fuel shapes by partially hydriding the massive metal and simultaneously dehydriding and nitriding the dehydrided portion. The process is repeated until all of the massive metal is converted to a nitride.

  15. Effect of N{sub 2} and Ar gas on DC arc plasma generation and film composition from Ti-Al compound cathodes

    SciTech Connect

    Zhirkov, Igor Rosen, Johanna; Oks, Efim

    2015-06-07

    DC arc plasma from Ti, Al, and Ti{sub 1−x}Al{sub x} (x = 0.16, 0.25, 0.50, and 0.70) compound cathodes has been characterized with respect to plasma chemistry (charged particles) and charge-state-resolved ion energy for Ar and N{sub 2} pressures in the range 10{sup −6} to 3 × 10{sup −2} Torr. Scanning electron microscopy was used for exploring the correlation between the cathode and film composition, which in turn was correlated with the plasma properties. In an Ar atmosphere, the plasma ion composition showed a reduction of Al of approximately 5 at. % compared to the cathode composition, while deposited films were in accordance with the cathode stoichiometry. Introducing N{sub 2} above ∼5 × 10{sup −3} Torr, lead to a reduced Al content in the plasma as well as in the film, and hence a 1:1 correlation between the cathode and film composition cannot be expected in a reactive environment. This may be explained by an influence of the reactive gas on the arc mode and type of erosion of Ti and Al rich contaminations, as well as on the plasma transport. Throughout the investigated pressure range, a higher deposition rate was obtained from cathodes with higher Al content. The origin of generated gas ions was investigated through the velocity rule, stating that the most likely ion velocities of all cathode elements from a compound cathode are equal. The results suggest that the major part of the gas ions in Ar is generated from electron impact ionization, while gas ions in a N{sub 2} atmosphere primarily originate from a nitrogen contaminated layer on the cathode surface. The presented results provide a contribution to the understanding processes of plasma generation from compound cathodes. It also allows for a more reasonable approach to the selection of composite cathode and experimental conditions for thin film depositions.

  16. Hydrodynamic and direct-current insulator-based dielectrophoresis (H-DC-iDEP) microfluidic blood plasma separation.

    PubMed

    Mohammadi, Mahdi; Madadi, Hojjat; Casals-Terré, Jasmina; Sellarès, Jordi

    2015-06-01

    Evaluation and diagnosis of blood alterations is a common request for clinical laboratories, requiring a complex technological approach and dedication of health resources. In this paper, we present a microfluidic device that owing to a novel combination of hydrodynamic and dielectrophoretic techniques can separate plasma from fresh blood in a microfluidic channel and for the first time allows optical real-time monitoring of the components of plasma without pre- or post-processing. The microchannel is based on a set of dead-end branches at each side and is initially filled using capillary forces with a 2-μL droplet of fresh blood. During this process, stagnation zones are generated at the dead-end branches and some red blood cells (RBCs) are trapped there. An electric field is then applied and dielectrophoretic trapping of RBCs is used to prevent more RBCs entering into the channel, which works like a sieve. Besides, an electroosmotic flow is generated to sweep the rest of the RBCs from the central part of the channel. Consequently, an RBC-free zone of plasma is formed in the middle of the channel, allowing real-time monitoring of the platelet behavior. To study the generation of stagnation zones and to ensure RBC trapping in the initial constrictions, two numerical models were solved. The proposed experimental design separates up to 0.1 μL blood plasma from a 2-μL fresh human blood droplet. In this study, a plasma purity of 99 % was achieved after 7 min, according to the measurements taken by image analysis. Graphical Abstract Schematics of a real-time plasma monitoring system based on a Hydrodynamic and direct-current insulator-based dielectrophoresis microfluidic channel.

  17. M3D-C1 simulations of the plasma response to n = 3 magnetic perturbations applied to the NSTX-U snowflake divertor

    NASA Astrophysics Data System (ADS)

    Canal, G. P.; Ferraro, N. M.; Evans, T. E.; Osborne, T. H.; Menard, J. E.; Ahn, J.-W.; Maingi, R.; Wingen, A.; Ciro, D.; Frerichs, H.; Schmitz, O.; Soukhanoviskii, V.; Waters, I.

    2016-10-01

    Single- and two-fluid resistive magnetohydrodynamic simulations, performed with the code M3D-C1, are used to investigate the effect of n = 3 magnetic perturbations on the SF divertor configuration. The calculations are based on simulated NSTX-U plasmas and the results show that additional and longer magnetic lobes are created in the null-point region of the SF configuration, compared to those in the conventional single-null. The intersection of these additional and longer lobes with the divertor plates are expected to cause more striations in the particle and heat flux target profiles. In addition, the results indicate that the size of the magnetic lobes, in both single-null and SF configurations, are more sensitive to resonant than to non-resonant magnetic perturbations. The results also suggest that lower values of current in non-axisymmetric control coils close enough to the primary x-point would be required to suppress edge localized modes in plasmas with the SF configuration. This work has been supported by the US Department of Energy, Office of Science, Office of Fusion Energy Science under DOE Award DE-SC0012706.

  18. Modifications in Structural, Electrical, Electronic and Mechanical Properties of Titanium Thin Films under different Gas Plasmas

    NASA Astrophysics Data System (ADS)

    Singh, Omveer; Dahiya, Raj P.; Malik, Hitendra K.

    2015-09-01

    In the recent past, Titanium thin films can be grown over different substrates such as silicon, glass and quartz by using versatile deposition techniques DC, RF sputtering, electronic beam and thermal evaporation etc. The grown films are then exposed in different gas environments for individual application. It has been found that Titanium nitride exhibits good chemical stability, mechanical and electrical properties. To investigate these properties in titanium nitride thin films, we have developed a new approach hot cathode arc discharge plasma system. By using this technique, we can measure plasma and nitriding parameters independently. In the present work, we have investigated gases mixture (Nitrogen, Argon and Hydrogen) effect on the structural, mechanical, electrical and electronic properties in plasma system. We have used 100% N2, 50% N2 + 50% Ar and 50% N2 + 50% H2 gases ratio for plasma nitriding. Structural and electronic structure properties are measured from X-ray diffractions (XRD) and X-ray photoelectron spectroscopy (XPS) respectively. The surface morphology of these films were measured using Atomic Force Microscopy (AFM) and the nano-indentation mode is used to find out the hardness of the samples. Government of India.

  19. Nitride passivation of the interface between high-k dielectrics and SiGe

    NASA Astrophysics Data System (ADS)

    Sardashti, Kasra; Hu, Kai-Ting; Tang, Kechao; Madisetti, Shailesh; McIntyre, Paul; Oktyabrsky, Serge; Siddiqui, Shariq; Sahu, Bhagawan; Yoshida, Naomi; Kachian, Jessica; Dong, Lin; Fruhberger, Bernd; Kummel, Andrew C.

    2016-01-01

    In-situ direct ammonia (NH3) plasma nitridation has been used to passivate the Al2O3/SiGe interfaces with Si nitride and oxynitride. X-ray photoelectron spectroscopy of the buried Al2O3/SiGe interface shows that NH3 plasma pre-treatment should be performed at high temperatures (300 °C) to fully prevent Ge nitride and oxynitride formation at the interface and Ge out-diffusion into the oxide. C-V and I-V spectroscopy results show a lower density of interface traps and smaller gate leakage for samples with plasma nitridation at 300 °C.

  20. Milliwatt dc/dc Inverter

    NASA Technical Reports Server (NTRS)

    Mclyman, C. W.

    1983-01-01

    Compact dc/dc inverter uses single integrated-circuit package containing six inverter gates that generate and amplify 100-kHz square-wave switching signal. Square-wave switching inverts 10-volt local power to isolated voltage at another desired level. Relatively high operating frequency reduces size of filter capacitors required, resulting in small package unit.