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Sample records for sio2 film induced

  1. Influence of outgassing organic contamination on the transmittance and laser-induced damage of SiO2 sol-gel antireflection film

    NASA Astrophysics Data System (ADS)

    Yang, Liang; Xiang, Xia; Miao, Xinxiang; Li, Zhijie; Zhou, Guorui.; Yan, Zhonghua; Yuan, Xiaodong; Zheng, Wanguo; Zu, Xiaotao

    2015-12-01

    The influence of organic contamination (rubber outgassing) on the transmittance of the SiO2 sol-gel antireflection (AR) film and laser-induced damage threshold (LIDT) at 355 nm for 3ω AR film and at 1064 nm for 1ω AR film is studied. The correlation between the contamination time and the transmittance loss/LIDT of 1ω/3ω AR film is also investigated both in atmospheric and vacuum environments. The results show that the transmittance loss increases with increasing contamination time, and the LIDT decreases with increasing contamination time for both in atmospheric and vacuum environments. In addition, the resistance against contamination of the 1ω film is stronger than 3ω film, and the contamination is more serious in vacuum than in an atmosphere environment for the same contamination time. Meanwhile, the damage mechanism is also discussed. It indicated that both the porous structure and photo-thermal absorption contribute to the decreasing LIDT of the sol-gel AR film.

  2. Electron beam induced damage in PECVD Si3N4 and SiO2 films on InP

    NASA Technical Reports Server (NTRS)

    Pantic, Dragan M.; Kapoor, Vik J.; Young, Paul G.; Williams, Wallace D.; Dickman, John E.

    1990-01-01

    Phosphorus rich plasma enhanced chemical vapor deposition (PECVD) of silicon nitride and silicon dioxide films on n-type indium phosphide (InP) substrates were exposed to electron beam irradiation in the 5 to 40 keV range for the purpose of characterizing the damage induced in the dielectic. The electron beam exposure was on the range of 10(exp -7) to 10(exp -3) C/sq cm. The damage to the devices was characterized by capacitance-voltage (C-V) measurements of the metal insulator semiconductor (MIS) capacitors. These results were compared to results obtained for radiation damage of thermal silicon dioxide on silicon (Si) MOS capacitors with similar exposures. The radiation induced damage in the PECVD silicon nitride films on InP was successfully annealed out in an hydrogen/nitrogen (H2/N2) ambient at 400 C for 15 min. The PECVD silicon dioxide films on InP had the least radiation damage, while the thermal silicon dioxide films on Si had the most radiation damage.

  3. Large Electric Field–Enhanced–Hardness Effect in a SiO2 Film

    PubMed Central

    Revilla, Reynier I.; Li, Xiao-Jun; Yang, Yan-Lian; Wang, Chen

    2014-01-01

    Silicon dioxide films are extensively used in nano and micro–electromechanical systems. Here we studied the influence of an external electric field on the mechanical properties of a SiO2 film by using nanoindentation technique of atomic force microscopy (AFM) and friction force microscopy (FFM). A giant augmentation of the relative elastic modulus was observed by increasing the localized electric field. A slight decrease in friction coefficients was also clearly observed by using FFM with the increase of applied tip voltage. The reduction of the friction coefficients is consistent with the great enhancement of sample hardness by considering the indentation–induced deformation during the friction measurements. PMID:24681517

  4. Large Electric Field-Enhanced-Hardness Effect in a SiO2 Film

    NASA Astrophysics Data System (ADS)

    Revilla, Reynier I.; Li, Xiao-Jun; Yang, Yan-Lian; Wang, Chen

    2014-03-01

    Silicon dioxide films are extensively used in nano and micro-electromechanical systems. Here we studied the influence of an external electric field on the mechanical properties of a SiO2 film by using nanoindentation technique of atomic force microscopy (AFM) and friction force microscopy (FFM). A giant augmentation of the relative elastic modulus was observed by increasing the localized electric field. A slight decrease in friction coefficients was also clearly observed by using FFM with the increase of applied tip voltage. The reduction of the friction coefficients is consistent with the great enhancement of sample hardness by considering the indentation-induced deformation during the friction measurements.

  5. Effects of thermal annealing on photoluminescence of Si+/C+ implanted SiO2 films

    NASA Astrophysics Data System (ADS)

    Chen, Yin-Yu; Chao, Der-Sheng; Tsai, Hsu-Sheng; Liang, Jenq-Horng

    2016-04-01

    The mechanisms of photoluminescence (PL) originating from Si+/C+ implanted SiO2 are still unclear and need to be clarified. Thus, the purpose of this study is to thoroughly investigate the effects of ion implantation and post-annealing temperature on microstructures and PL characteristics of the Si+/C+ implanted SiO2 films. A comparative analysis was also conducted to clarify the different optical properties between the Si+ and Si+/C+ implanted SiO2 films. In this study, thermally-grown SiO2 films on Si substrates were used as the matrix materials. The Si+ ions and C+ ions were separately implanted into the SiO2 films at room temperature. After ion implantation, the post-annealing treatments were carried out using the furnace annealing (FA) method at various temperatures (600-1100 °C) for 1 h in a N2 ambient. The PL characteristics of the implanted SiO2 films were analyzed using a fluorescence spectrophotometer. The results revealed that the distinct PL peaks were observed at approximately 310, 450 and 650 nm in the Si+-implanted SiO2 films, which can be attributed to the defects, the so-called oxygen deficiency centers (ODCs) and non-bridging oxygen hole centers (NBOHCs), in the materials. In contrast to the Si+ ion implantation, the SiO2 films which were sequentially implanted with Si+ and C+ ions and annealed at 1100 °C can emit white light corresponding to the PL peaks located at around 420, 520 and 720 nm, those can be assigned to the Si-C bonding, C-C graphite-like structure (sp2), and Si nanocrystals, respectively. Moreover, a correlation between the optical properties, microstructures, and bonding configurations of the Si+/C+ implanted SiO2 films was also established in this study.

  6. Highly Luminescent Hybrid SiO2-Coated CdTe Quantum Dots Retained Initial Photoluminescence Efficiency in Sol-Gel SiO2 Film.

    PubMed

    Sun, Hongsheng; Xing, Yugui; Wu, Qinan; Yang, Ping

    2015-02-01

    A highly luminescent silica film was fabricated using tetraethyl orthosilicate (TEOS) and 3-aminopropyltrimethoxysilane (APS) through a controlled sol-gel reaction. The pre-hydrolysis of TEOS and APS which resulted in the mixture of TEOS and APS in a molecular level is a key for the formation of homogenous films. The aminopropyl groups in APS play an important role for obtaining homogeneous film with high photoluminescence (PL). Red-emitting hybrid SiO2-coated CdTe nano-crystals (NCs) were fabricated by a two-step synthesis including a thin SiO2 coating via a sol-gel process and a subsequent refluxing using green-emitting CdTe NCs. The hybrid SiO2-coated CdTe NCs were embedded in a functional SiO2 film via a two-step process including adding the NCs in SiO2 sol with a high viscosity and almost without ethanol and a subsequent spinning coating. The hybrid SiO2-coated CdTe NCs retained their initial PL efficiency (54%) in the film. Being encapsulated with the hybrid NCs in the film, no change on the absorption and PL spectra of red-emitting CdTe NCs (632 nm) was observed. This indicates the hybrid NCs is stable enough during preparation. This phenomenon is ascribed to the controlled sol-gel process and a hybrid SiO2 shell on CdTe NCs. Because these films exhibited high PL efficiency and stability, they will be utilizable for potential applications in many fields. PMID:26353691

  7. Room temperature bonding of SiO2 and SiO2 by surface activated bonding method using Si ultrathin films

    NASA Astrophysics Data System (ADS)

    Utsumi, Jun; Ide, Kensuke; Ichiyanagi, Yuko

    2016-02-01

    The bonding of metal electrodes and insulator hybrid interfaces is one of the key techniques in three-dimensional integration technology. Metal materials such as Cu or Al are easily directly bonded by surface activated bonding at room temperature, but insulator materials such as SiO2 or SiN are not. Using only Si ultrathin films, we propose a new bonding technique for SiO2/SiO2 bonding at room temperature. Two SiO2 surfaces, on which Si thin films were deposited, were contacted in vacuum. We confirmed that the thickness of the layer was about 7 nm by transmission electron microscopy observation and that the layer was non crystalline by electron energy loss spectroscopy analysis. No metal material was found in the bonding interface by energy-dispersive X-ray spectroscopy analysis. The surface energy was about 1 J/m2, and the bonding strength was more than 25 MPa. This bonding technique was successfully realized to enable SiO2/SiO2 bonding without a metal adhesion layer.

  8. Optical properties of Ag nanoclusters formed by irradiation and annealing of SiO2/SiO2:Ag thin films

    NASA Astrophysics Data System (ADS)

    Güner, S.; Budak, S.; Gibson, B.; Ila, D.

    2014-08-01

    We have deposited five periodic SiO2/SiO2 + Ag multi-nano-layered films on fused silica substrates using physical vapor deposition technique. The co-deposited SiO2:Ag layers were 2.7-5 nm and SiO2 buffer layers were 1-15 nm thick. Total thickness was between 30 and 105 nm. Different concentrations of Ag, ranging from 1.5 to 50 molecular% with respect to SiO2 were deposited to determine relevant rates of nanocluster formation and occurrence of interaction between nanoclusters. Using interferometry as well as in situ thickness monitoring, we measured the thickness of the layers. The concentration of Ag in SiO2 was measured with Rutherford Backscattering Spectrometry (RBS). To nucleate Ag nanoclusters, 5 MeV cross plane Si ion bombardments were performed with fluence varying between 5 × 1014 and 1 × 1016 ions/cm2 values. Optical absorption spectra were recorded in the range of 200-900 nm in order to monitor the Ag nanocluster formation in the thin films. Thermal annealing treatment at different temperatures was applied as second method to form varying size of nanoclusters. The physical properties of formed super lattice were criticized for thermoelectric applications.

  9. Strengthening sapphire at elevated temperatures by SiO 2 films

    NASA Astrophysics Data System (ADS)

    Feng, Li-Ping; Liu, Zheng-Tang; Li, Qiang

    2007-04-01

    SiO 2 films have been prepared on sapphire by radio frequency magnetron reactive sputtering in order to increase the optical and mechanical properties of infrared windows and domes of sapphire at elevated temperatures. Infrared transmission and flexural strength of uncoated and coated sapphires have been investigated at different temperatures. SiO 2 films were shown to have apparent antireflective effect on sapphire substrate at room temperature. With increasing temperature, the coated sapphires have larger average transmission than the uncoated ones. The temperature was proven to only weakly affect the absorption coefficient and antireflection capability of the deposited films. It is also indicated that the flexural strengths of the c-axis sapphire samples coated with SiO 2 films are increased by 1.2 and 1.5 times than those of uncoated at 600 and 800 °C, respectively.

  10. Preparation of SiO2 film utilizing equilibrium reaction in aqueous solution

    NASA Astrophysics Data System (ADS)

    Kawahara, Hideo; Sakai, Y.; Goda, Takuji; Hishinuma, Akihiro; Takemura, Kazuo

    1991-08-01

    It has been reported in previous works on the LPD (liquid phase deposition) method that SiO2 film deposition could be made by utilizing the chemical transition from supersaturation to saturation in silica dissolution in H2SiF6 aqueous solution. In this study, the supersaturated state was obtained and maintained by employing the dependence of silica solubility on H2SiF6 solution temperature without a reaction initiator. As for the influence of the process parameters on SiO2 film properties, it came into notice that a dense film structure was obtained in the deposition at higher solution temperature (around 60 degree(s)C). As a result, transparent and crack-free thick SiO2 film over 10 microns was obtained by this advanced LPD method.

  11. Ion assisted deposition of SiO2 film from silicon

    NASA Astrophysics Data System (ADS)

    Pham, Tuan. H.; Dang, Cu. X.

    2005-09-01

    Silicon dioxide, SiO2, is one of the preferred low index materials for optical thin film technology. It is often deposited by electron beam evaporation source with less porosity and scattering, relatively durable and can have a good laser damage threshold. Beside these advantages the deposition of critical optical thin film stacks with silicon dioxide from an E-gun was severely limited by the stability of the evaporation pattern or angular distribution of the material. The even surface of SiO2 granules in crucible will tend to develop into groove and become deeper with the evaporation process. As the results, angular distribution of the evaporation vapor changes in non-predicted manner. This report presents our experiments to apply Ion Assisted Deposition process to evaporate silicon in a molten liquid form. By choosing appropriate process parameters we can get SiO2 film with good and stable property.

  12. Nanoporous SiO2 thin films made by atomic layer deposition and atomic etching.

    PubMed

    Ghazaryan, Lilit; Kley, E-Bernhard; Tünnermann, Andreas; Szeghalmi, Adriana

    2016-06-24

    A new route to prepare nanoporous SiO2 films by mixing atomic-layer-deposited alumina and silica in an Å-scale is presented. The selective removal of Al2O3 from the composites using wet chemical etching with phosphoric acid resulted in nanoporous thin SiO2 layers. A diffusion-controlled dissolution mechanism is identified whereby an interesting reorganization of the residual SiO2 is observed. The atomic scale oxide mixing is decisive in attaining and tailoring the film porosity. The porosity and the refractive index of nanoporous silica films were tailored from 9% to 69% and from 1.40 to 1.13, respectively. The nanoporous silica was successfully employed as antireflection coatings and as diffusion membranes to encapsulate nanostructures. PMID:27176497

  13. Nanoporous SiO2 thin films made by atomic layer deposition and atomic etching

    NASA Astrophysics Data System (ADS)

    Ghazaryan, Lilit; Kley, E.-Bernhard; Tünnermann, Andreas; Szeghalmi, Adriana

    2016-06-01

    A new route to prepare nanoporous SiO2 films by mixing atomic-layer-deposited alumina and silica in an Å-scale is presented. The selective removal of Al2O3 from the composites using wet chemical etching with phosphoric acid resulted in nanoporous thin SiO2 layers. A diffusion-controlled dissolution mechanism is identified whereby an interesting reorganization of the residual SiO2 is observed. The atomic scale oxide mixing is decisive in attaining and tailoring the film porosity. The porosity and the refractive index of nanoporous silica films were tailored from 9% to 69% and from 1.40 to 1.13, respectively. The nanoporous silica was successfully employed as antireflection coatings and as diffusion membranes to encapsulate nanostructures.

  14. Anti-fogging nanofibrous SiO(2) and nanostructured SiO(2)-TiO(2) films made by rapid flame deposition and in situ annealing.

    PubMed

    Tricoli, Antonio; Righettoni, Marco; Pratsinis, Sotiris E

    2009-11-01

    Transparent, pure SiO(2), TiO(2), and mixed silica-titania films were (stochastically) deposited directly onto glass substrates by flame spray pyrolysis of organometallic solutions (hexamethyldisiloxane or tetraethyl orthosilicate and/or titanium tetra isopropoxide in xylene) and stabilized by in situ flame annealing. Silicon dioxide films consisted of a network of interwoven nanofibers or nanowires several hundred nm long and 10-15 nm thick, as determined by microscopy. These nanowire or nanofibrous films were formed by chemical vapor deposition (surface growth) on bare glass substrates during scalable combustion of precursor solutions at ambient conditions, for the first time to our knowledge, as determined by thermophoretic sampling of the flame aerosol and microscopy. In contrast, titanium dioxide films consisted of nanoparticles 3-5 nm in diameter that were formed in the flame and deposited onto the glass substrate, resulting in highly porous, lace-like nanostructures. Mixed SiO(2)-TiO(2) films (40 mol % SiO(2)) had similar morphology to pure TiO(2) films. Under normal solar radiation, all such films having a minimal thickness of about 300 nm completely prevented fogging of the glass substrates. These anti-fogging properties were attributed to inhibition of water droplet formation by such super-hydrophilic coatings as determined by wetting angle measurements. Deactivated (without UV radiation) pure TiO(2) coatings lost their super-hydrophilicity and anti-fogging properties even though their wetting angle was reduced by their nanowicking. In contrast, SiO(2)-TiO(2) coatings exhibited the best anti-fogging performance at all conditions taking advantage of the high surface coverage by TiO(2) nanoparticles and the super-hydrophilic properties of SiO(2) on their surface. PMID:19621912

  15. Thermoelectric generators from SiO2/SiO2 + Ge nanolayer thin films modified by MeV Si ions

    NASA Astrophysics Data System (ADS)

    Budak, S.; Gulduren, E.; Allen, B.; Cole, J.; Lassiter, J.; Colon, T.; Muntele, C.; Alim, M. A.; Bhattacharjee, S.; Johnson, R. B.

    2015-01-01

    We prepared thermoelectric generator devices from 100 alternating layers of SiO2/SiO2 + Ge superlattice thin films using Magnetron DC/RF Sputtering. Rutherford Backscattering Spectrometry (RBS) and RUMP simulation software package were used to determine the proportions of Si and Ge in the grown multilayer films and the thickness of the grown multi-layer films. 5 MeV Si ion bombardments were performed using the AAMU-Pelletron ion beam accelerator, to form quantum clusters in the multi-layer superlattice thin films, in order to tailor the thermoelectrical and optical properties. We characterized the fabricated thermoelectric devices using cross-plane Seebeck coefficient, van der Pauw resistivity, mobility, density (carrier concentration), Hall Effect coefficient, Raman, Fluorescence, Photoluminescence, Atomic Force Microscopy (AFM) and Impedance analyzing measurements. Some suitable high energy ion fluences and thermal annealings caused some remarkable thermoelectrical and optical changes in the fabricated multilayer thin film systems.

  16. Effects of modifiers on the hydrophobicity of SiO2 films from nano-husk ash

    NASA Astrophysics Data System (ADS)

    Xu, Kejing; Sun, Qingwen; Guo, Yanqing; Dong, Shuhua

    2013-07-01

    Nano-husk ashes were prepared by burning rice-husk with self-propagating method. The super-hydrophobic SiO2 films from nano-husk ash were prepared by sol-gel method using hydroxy silicone oil (HSO), hexamethyldisilazane (HMS), or methyl triethoxysilane (MTS) as modifiers. The effects of modifiers on the hydrophobic property of SiO2 films were studied, and the performances were characterized by the XRD, UV-vis, BET, EDS, SEM, IR, and Contact Angle Analyzer. The results showed that the contact angle of SiO2 films was more than 160° when volume ratio of the modifiers to silicon-sodium solution (SSS) was 0.15. The mechanism of modifiers on SiO2 surfaces is a graft copolymerization. The hydrophobic groups in the modifiers replace the hydroxy groups on SiO2 surfaces and make SiO2 surfaces present super-hydrophobicity.

  17. Laser-induced chemical vapor deposition of SiO2

    NASA Astrophysics Data System (ADS)

    Boyer, P. K.; Roche, G. A.; Ritchie, W. H.; Collins, G. J.

    1982-04-01

    We have demonstrated rapid (3000 Å/min) photochemical deposition of silicon dioxide from gas phase donor molecules. An ArF (193 nm) laser was used to excite and dissociate gas phase SiH4 and N2O molecules in contrast to earlier work with incoherent mercury lamps. We have achieved 20 times the deposition rate, limited the dissociation volume to a localized region, and minimized the direct impingement of UV photons on the substrate. Although the SiO2 deposition rate was insensitive to substrate temperature from 20 to 600 °C, film quality noticeably improved above 200 °C. Metal-oxide-semiconductor capacitors were fabricated and characterized in order to measure SiO2 electrical properties. Film composition was investigated using Auger and infrared spectroscopy techniques and showed that the SiO2 is stoichiometric and contains less than 5% nitrogen.

  18. The hybrid photocatalyst of TiO2-SiO2 thin film prepared from rice husk silica

    NASA Astrophysics Data System (ADS)

    Klankaw, P.; Chawengkijwanich, C.; Grisdanurak, N.; Chiarakorn, Siriluk

    2012-03-01

    The TiO2-SiO2 thin film was prepared by self-assembly method by mixing SiO2 precursor with titanium precursor solution and aged to obtain a co-precipitation of silica and titanium crystals. Dip coating method was applied for thin film preparation on glass slide. The X-ray diffraction (XRD) of the self-assembly thin film had no characteristic property of SiO2 and even anatase TiO2 but indicated new crystal structure which was determined from the Fourier Transform Infrared Spectrophotometer (FTIR) as a hybridized Ti-O-Si bonding. The surface area and surface volume of the self-assembly sample were increased when SiO2 was incorporated into the film. The self-assembly TiO2-SiO2 thin film exhibited the enhanced photocatalytic decolorization of methylene blue (MB) dye. The advantages of SiO2 are; (1) to increase the adsorbability of the film and (2) to provide the hydroxyl radical to promote the photocatalytic reaction. The self-assembly thin film with the optimum molar ratio (SiO2:TiO2) as 20:80 gave the best performance for photocatalytic decolorization of MB dye with the overall efficiency of 81%.

  19. Direct fabrication of graphene on SiO2 enabled by thin film stress engineering

    PubMed Central

    McNerny, Daniel Q.; Viswanath, B.; Copic, Davor; Laye, Fabrice R.; Prohoda, Christophor; Brieland-Shoultz, Anna C.; Polsen, Erik S.; Dee, Nicholas T.; Veerasamy, Vijayen S.; Hart, A. John

    2014-01-01

    We demonstrate direct production of graphene on SiO2 by CVD growth of graphene at the interface between a Ni film and the SiO2 substrate, followed by dry mechanical delamination of the Ni using adhesive tape. This result is enabled by understanding of the competition between stress evolution and microstructure development upon annealing of the Ni prior to the graphene growth step. When the Ni film remains adherent after graphene growth, the balance between residual stress and adhesion governs the ability to mechanically remove the Ni after the CVD process. In this study the graphene on SiO2 comprises micron-scale domains, ranging from monolayer to multilayer. The graphene has >90% coverage across centimeter-scale dimensions, limited by the size of our CVD chamber. Further engineering of the Ni film microstructure and stress state could enable manufacturing of highly uniform interfacial graphene followed by clean mechanical delamination over practically indefinite dimensions. Moreover, our findings suggest that preferential adhesion can enable production of 2-D materials directly on application-relevant substrates. This is attractive compared to transfer methods, which can cause mechanical damage and leave residues behind. PMID:24854632

  20. Effects of Mev Si Ions and Thermal Annealing on Thermoelectric and Optical Properties of SiO2/SiO2+Ge Multi-nanolayer thin Films

    NASA Astrophysics Data System (ADS)

    Budak, S.; Alim, M. A.; Bhattacharjee, S.; Muntele, C.

    Thermoelectric generator devices have been prepared from 200 alternating layers of SiO2/SiO2+Ge superlattice films using DC/RF magnetron sputtering. The 5 MeV Si ionsbombardmenthasbeen performed using the AAMU Pelletron ion beam accelerator to formquantum dots and / or quantum clusters in the multi-layer superlattice thin films to decrease the cross-plane thermal conductivity, increase the cross-plane Seebeck coefficient and increase the cross-plane electrical conductivity to increase the figure of merit, ZT. The fabricated devices have been annealed at the different temperatures to tailor the thermoelectric and optical properties of the superlattice thin film systems. While the temperature increased, the Seebeck coefficient continued to increase and reached the maximum value of -25 μV/K at the fluenceof 5x1013 ions/cm2. The decrease in resistivity has been seen between the fluence of 1x1013 ions/cm2 and 5x1013 ions/cm2. Transport properties like Hall coefficient, density and mobility did not change at all fluences. Impedance spectroscopy has been used to characterize the multi-junction thermoelectric devices. The loci obtained in the C*-plane for these data indicate non-Debye type relaxation displaying the presence of the depression parameter.

  1. Charging mechanism of electret film made of potassium-ion-doped SiO2

    NASA Astrophysics Data System (ADS)

    Hashiguchi, G.; Nakasone, D.; Sugiyama, T.; Ataka, M.; Toshiyoshi, H.

    2016-03-01

    A charging model is proposed for an electret film made of potassium-ion-doped SiO2 that can be formed between the two opposing micro-electrodes of a micro-electrostatic actuator, separated by a microscopic gap. On the basis of experimental evidence that charging only occurs in the positively biased electrode during the charging process and that the charging polarity is negative, we assumed that the cause of the electret charges is negatively charged oxygen ions residing in the SiO2 film, which arise as a consequence of potassium ion depletion. This assumption was supported by SIMS (Secondary Ion Mass Spectroscopy) analyses that indicate the presence of a depletion region of potassium ions near the interface of the silicon and the oxide film on the positively biased electrode. Calculations of the charged potential using Poisson's equation with the spatially distributed negative charges in the depletion region showed good agreement with the measured surface potential. It appears that our charging model can consistently elucidate potassium ion electret technology.

  2. Influence of adsorption kinetics on stress evolution in magnetron-sputtered SiO2 and SiNx films

    NASA Astrophysics Data System (ADS)

    Li, Jingping; Fang, Ming; He, Hongbo; Shao, Jianda; Li, Zhaoyang

    2013-07-01

    An in situ multi-beam optical sensor system was used to monitor and analyze the force per unit width (F/w) and stress evolution during several stages in magnetron-sputtered SiO2 and SiNx films. Stress was observed to relieve quickly after interrupt and recover rapidly after growth resumption in both films. Stress relief was reversible in SiO2 film but partial reversible in SiNx film. Stress relief results from both physical and chemical adsorption. Stress recovery is caused by physical desorption. And chemical adsorption results in an irreversible stress relief component. No chemical adsorption occurs in SiO2 film because of the stable chemical structure. The relationship between adsorption kinetics and films' mechanical behavior is revealed.

  3. Mixed films of TiO2-SiO2 deposited by double electron-beam coevaporation

    NASA Astrophysics Data System (ADS)

    Chen, Jyh-Shin; Chao, Shiuh; Kao, Jiann-Shiun; Niu, Huan; Chen, Chih-Hsin

    1996-01-01

    We used double electron-beam coevaporation to fabricate TiO2-SiO2 mixed films. The deposition process included oxygen partial pressure, substrate temperature, and deposition rate, all of which were real-time computer controlled. The optical properties of the mixed films varied from pure SiO2 to pure TiO2 as the composition of the films varied accordingly. X-ray diffraction showed that the mixed films all have amorphous structure with a SiO2 content of as low as 11%. Atomic force microscopy showed that the mixed film has a smoother surface than pure TiO2 film because of its amorphous structure. Linear and Bruggeman's effective medium approximation models fit the experimental data better than other models.

  4. Preparation and characterization of transparent hydrophilic photocatalytic TiO2/SiO2 thin films on polycarbonate.

    PubMed

    Fateh, Razan; Dillert, Ralf; Bahnemann, Detlef

    2013-03-19

    Transparent hydrophilic photocatalytic TiO2 coatings have been widely applied to endow the surfaces self-cleaning properties. A mixed metal oxide (TiO2/SiO2) can enhance the photocatalytic performance improving the ability of surface adsorption and increasing the amount of hydroxyl surface groups. The present work introduces a systematic study concerning the effect of the SiO2 addition to TiO2 films on the wettability, the photocatalytic activity, the adhesion strength, and the mechanical stability of the films. Transparent hydrophilic photocatalytic TiO2/SiO2 thin films were used to coat the polycarbonate (PC) substrate which was precoated by an intermediate SiO2 layer. The TiO2/SiO2 thin film was prepared employing a bulk TiO2 powder (Sachtleben Hombikat UV 100) and different molar ratios of tetraethoxysilane in acidic ethanol. A dip-coating process was used to deposit the films onto the polycarbonate substrate. The films were characterized by UV/vis spectrophotometry, FTIR spectroscopy, ellipsometry, BET, AFM, XRD, and water contact angle measurements. The mechanical stability and the UV resistance were examined. The photocatalytic activity of the coated surface was calculated from the kinetic analysis of methylene blue photodegradation measurements and compared with the photocatalytic activity of Pilkington Activ sheet glass. The coated surfaces displayed considerable photocatalytic activity and superhydrophilicity after exposure to UV light. The addition of SiO2 results in an improvement of the photocatalytic activity of the TiO2 film reaching the highest value at molar ratio TiO2/SiO2 equal to 1:0.9. The prepared films exhibit a good stability against UV(A) irradiation. PMID:23363048

  5. Structure of ultrathin crystalline SiO2 films on Mo(112)

    NASA Astrophysics Data System (ADS)

    Ricci, Davide; Pacchioni, Gianfranco

    2004-04-01

    The geometrical and electronic structures of a thin SiO2 film epitaxially grown on a Mo(112) substrate have been determined by first-principles density-functional theory calculations. β-cristobalite, β-tridymite, α-quartz, and β-quartz phases were considered. The film grows initially with an OH-terminated β-cristobalite structure which provides the strongest adhesion energy to the Mo substrate. High-temperature annealing results in a complete dehydroxylation and reconstruction of the top layer of the cristobalite film with the formation of two-membered silica rings. This accounts for a specific band at 795 cm-1 observed in the Fourier transform infra-red (FTIR) spectrum of the annealed epilayer.

  6. Preparation and characterization of amine-functionalized SiO 2/TiO 2 films for formaldehyde degradation

    NASA Astrophysics Data System (ADS)

    Photong, Somjate; Boonamnuayvitaya, Virote

    2009-09-01

    This paper investigated the gaseous formaldehyde degradation by the amine-functionalized SiO 2/TiO 2 photocatalytic films for improving indoor air quality. The films were synthesized via the co-condensation reaction of methyltrimethoxysilane (MTMOS) and 3-aminopropyltrimethoxysilane (APTMS). The physicochemical properties of prepared photocatalysts were characterized with N 2 adsorption/desorption isotherms measurement, X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy (FT/IR). The effect of amine-functional groups and the ratio of MTMOS/APTMS precursors on the formaldehyde adsorption and photocatalytic degradation were investigated. The results showed that the formaldehyde adsorption and photocatalytic degradation of the APTMS-functionalized SiO 2/TiO 2 film was higher than that of SiO 2/TiO 2 film due to the surface adsorption on amine sites and the relatively high of the specific surface area of the APTMS-functionalized SiO 2/TiO 2 film (˜15 times higher than SiO 2/TiO 2). The enhancement of the formaldehyde degradation of the film can be attributed to the synergetic effect of adsorption and subsequent photocatalytic decomposition. The repeatability of photocatalytic film was also tested and the degradation efficiency was 91.0% of initial efficiency after seven cycles.

  7. An Interfacial Europium Complex on SiO2 Nanoparticles: Reduction-Induced Blue Emission System

    PubMed Central

    Ishii, Ayumi; Hasegawa, Miki

    2015-01-01

    In this study, Eu-coated SiO2 nanoparticles have been prepared, consisting of an interfacial complex of Eu and 1,10-phenanthroline (phen) at the solid surfaces of the SiO2/Eu nanostructures. The as-prepared SiO2/Eu/phen nanoparticles exhibits sharp red emission via energy transfer from the phen to the EuIII. After sintering at 200 °C in air, the emission is tuned from red to blue. The blue emission is originated from EuII. This reduction-induced emissive phenomenon resulted from the electron-donating environment created by the surrounding phen and SiO2, which is the first reported fabrication of a stable EuII-based emissive material using mild conditions (reaction in air and at low temperature) and an organic-inorganic hybrid nanostructure. The existence of two different stable oxidation states with characteristic emissions, blue emissive EuII and red emissive EuIII, suggests significant potential applications as novel luminescent materials with inorganic-organic hybrid structures. PMID:26122318

  8. An Interfacial Europium Complex on SiO2 Nanoparticles: Reduction-Induced Blue Emission System

    NASA Astrophysics Data System (ADS)

    Ishii, Ayumi; Hasegawa, Miki

    2015-06-01

    In this study, Eu-coated SiO2 nanoparticles have been prepared, consisting of an interfacial complex of Eu and 1,10-phenanthroline (phen) at the solid surfaces of the SiO2/Eu nanostructures. The as-prepared SiO2/Eu/phen nanoparticles exhibits sharp red emission via energy transfer from the phen to the EuIII. After sintering at 200 °C in air, the emission is tuned from red to blue. The blue emission is originated from EuII. This reduction-induced emissive phenomenon resulted from the electron-donating environment created by the surrounding phen and SiO2, which is the first reported fabrication of a stable EuII-based emissive material using mild conditions (reaction in air and at low temperature) and an organic-inorganic hybrid nanostructure. The existence of two different stable oxidation states with characteristic emissions, blue emissive EuII and red emissive EuIII, suggests significant potential applications as novel luminescent materials with inorganic-organic hybrid structures.

  9. Electron-beam-induced formation mechanisms for Ti2O3-SiO2 composite nanofibers

    NASA Astrophysics Data System (ADS)

    Shin, Jae Won; Yang, Dae Jin; Lee, Seok-Hoon; Kim, Jin-Gyu; Yoo, Seung Jo; Yun, Dong Yeol; Lee, Dea Uk; Kim, Tae Whan

    2014-09-01

    Anatase TiO2 nanoparticles with high crystallinity were embedded in the SiO2 matrix by electrospining and calcining. As-calcined TiO2-SiO2 nanofibers were transformed into Ti2O3-SiO2 nanofibers owing to in situ electron-beam irradiation in a transmission electron microscope. The microstructural properties and the mechanisms of electron-beam-induced formation of Ti2O3-SiO2 composite nanofibers were described on the basis of the obtained high-resolution transmission electron microscopy images, fast-Fourier-transformed patterns, and energy dispersive spectroscopy profiles.

  10. Amorphous SnO2-SiO2 thin films with reticular porous morphology for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Chen, L. B.; Li, C. C.; Wang, T. H.

    2008-12-01

    Amorphous SnO2-SiO2 thin films with reticular porous morphology were fabricated by electrostatic spray deposition method for lithium-ion batteries. An initial discharge capacity of the SnO2-SiO2 electrodes with 15% of SiO2 was about 1271 mA h/g, and the reversible capacity stayed in the range of 869-501 mA h/g during the successive 100 cycles, but only 1141 and 694-174 mA h/g for the pure SnO2 electrodes. The high capacity was attributed to the addition of SiO2, which facilitated the formation of the Li-Sn alloy. The improved cycle performance was due to reticular porous structure, which accommodated the volume change during cycling.

  11. Characterization of ultrathin InSb nanocrystals film deposited on SiO2/Si substrate

    PubMed Central

    2011-01-01

    Recently, solid-phase recrystallization of ultrathin indium antimonide nanocrystals (InSb NCs (films grown on SiO2/Si substrate is very attractive, because of the rapid development of thermal annealing technique. In this study, the recrystallization behavior of 35 nm indium antimonide film was studied. Through X-ray diffraction (XRD) analysis, it is demonstrated that the InSb film is composed of nanocrystals after high temperature rapid thermal annealing. Scanning electron microscopy shows that the film has a smooth surface and is composed of tightly packed spherical grains, the average grain size is about 12.3 nm according to XRD results. The optical bandgap of the InSb NCs film analyzed by Fourier Transform infrared spectroscopy measurement is around 0.26 eV. According to the current-voltage characteristics of the InSb NCs/SiO2/p-Si heterojunction, the film has the rectifying behavior and the turn-on voltage value is near 1 V. PMID:22112251

  12. Photosensitive GeO2-SiO2 films for ultraviolet laser writing of channel waveguides and bragg gratings with Cr-loaded waveguide structure.

    PubMed

    Takahashi, Masahide; Sakoh, Akifumi; Ichii, Kentaro; Tokuda, Yomei; Yoko, Toshinobu; Nishii, Junji

    2003-08-01

    Irradiation with intense ultraviolet laser pulses induced a large refractive-index change in 30GeO2-70SiO2 waveguide-grade thin films prepared by the plasma-enhanced chemical vapor deposition method, which contained a large amount of photoactive Ge2+ defects. The maximum index change in the as-deposited films by KrF and XeF excimer laser irradiation was estimated to be 1.2 x 10(-3) and 0.28 x 10(-3), respectively. These results clearly indicate that the photorefractivity of GeO2-SiO2 glasses is due to a Ge2+ defect in origin. The channel waveguide and the planar Bragg gratings were directly written in the photoactive Ge(2+)-enriched GeOs-SiO2 thin films by pulsed ultraviolet laser irradiation with a Cr-metal-loaded-type waveguide structure. PMID:12916627

  13. Optical characterization of SiO2 thin films using universal dispersion model over wide spectral range

    NASA Astrophysics Data System (ADS)

    Franta, Daniel; Nečas, David; Ohlídal, Ivan; Giglia, Angelo

    2016-04-01

    Vacuum evaporated SiO2 thin films are very important in a design and manufacturing of optical devices produced in optics industry. In this contribution a reliable and precise optical characterization of such SiO2 thin films is performed using the combined method of spectrophotometry at normal incidence and variable-angle spectroscopic ellipsometry applied over spectral range from far IR to extreme UV (0.01-45 eV). This method uses the Universal Dispersion Model based on parametrization of the joint density of states and structural model comprising film defects such as nanometric boundary roughness, inhomogeneity and area non-uniformity. The optical characterization over the wide spectral range provides not only the spectral dependencies of the optical constants of the films within the wide range but, more significantly, it enables their correct and precise determination within the spectral range of interest, i.e. the range of their transparency. Furthermore, measurements in the ranges of film absorption, i. e. phonon excitations in IR and electron excitations in UV, reveal information about the material structure. The results of the optical characterization of the SiO2 thin films prepared on silicon single crystal substrates under various technological conditions are presented in detail for two selected samples. Beside film thicknesses and values of dispersion parameters and spectral dependencies of the optical constants of the SiO2 films, the characterization also enables quantification of film defects and their parameters are presented as well. The results concerning the optical constants of SiO2 films are compared with silica optical constants determined in our earlier studies.

  14. Absorption enhancement in thin film a-Si solar cells with double-sided SiO2 particle layers

    NASA Astrophysics Data System (ADS)

    Chen, Le; Wang, Qing-Kang; Shen, Xiang-Qian; Chen, Wen; Huang, Kun; Liu, Dai-Ming

    2015-10-01

    Light absorption enhancement is very important for improving the power conversion efficiency of a thin film a-Si solar cell. In this paper, a thin-film a-Si solar cell model with double-sided SiO2 particle layers is designed, and then the underlying mechanism of absorption enhancement is investigated by finite difference time domain (FDTD) simulation; finally the feasible experimental scheme for preparing the SiO2 particle layer is discussed. It is found that the top and bottom SiO2 particle layers play an important role in anti-reflection and light trapping, respectively. The light absorption of the cell with double-sided SiO2 layers greatly increases in a wavelength range of 300 nm-800 nm, and the ultimate efficiency increases more than 22% compared with that of the flat device. The cell model with double-sided SiO2 particle layers reported here can be used in varieties of thin film solar cells to further improve their performances. Project supported by the National High-Tech Research and Development Program of China (Grant No. 2011AA050518), the University Research Program of Guangxi Education Department, China (Grant No. LX2014288), and the Natural Science Foundation of Guangxi Zhuang Autonomous Region, China (Grant No. 2013GXNSBA019014).

  15. Room temperature synthesis of porous SiO2 thin films by plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Barranco, A.; Cotrino, J.; Yubero, F.; Espinós, J. P.; González-Elipe, A. R.

    2004-07-01

    Silicon dioxide thin films with variable and controlled porosity have been prepared at room temperature by plasma enhanced chemical vapor deposition in an electron cyclotron resonance microwave reactor with a downstream configuration. The procedure consists of the deposition of successive cycles consisting of a sacrificial organic-polymeric layer and, afterward, a silicon dioxide layer. Toluene and oxygen are used as precursors of the organic layers and Si(CH3)3Cl and oxygen for the SiO2. During deposition of the latter, the organic layer is simultaneously burned off. In these conditions, the release of gases produced by oxidation of the organic-polymeric layer take place while the oxide layer is being deposited. Thus, modification of the nucleation and growing mechanism of the silicon oxide thin film take place. The porosity of the final porous SiO2 thin films increases with the thickness of the sacrificial organic layer. The porous SiO2 films prepared with the aforementioned method are free of carbon and chlorine contamination as confirmed by Fourier-transform infrared spectroscopy, x-ray photoelectron spectroscopy, and Rutherford backscattering spectroscopy. Depending on their porosity, the SiO2 thin films are either transparent or scattered visible light. The former have refractive index lower than that of thermal silicon dioxide and the latter show membranelike behavior in gas diffusion experiments. All the samples have good adhesion to the substrates used for the deposition, either polished Si wafer, glass plates, or standard porous supports. They have columnar microstructure, as determined by scanning electron microscopy. A preliminary ultraviolet-visible characterization of the optically transparent thin films reveals that transmission of light through glass increases by 7%-8% when the porous silica is deposited on this substrate. These films prove to be very efficient as antireflective coatings and are of interest for photovoltaic and similar applications

  16. Role of HfO2/SiO2 thin-film interfaces in near-ultraviolet absorption and pulsed laser damage

    DOE PAGESBeta

    Papernov, Semyon; Kozlov, Alexei A.; Oliver, James B.; Smith, Chris; Jensen, Lars; Guenster, Stefan; Maedebach, Heinrich; Ristau, Detlev

    2016-07-15

    Here, the role of thin-film interfaces in the near-ultraviolet (near-UV) absorption and pulsed laser-induced damage was studied for ion-beam-sputtered and electron-beam-evaporated coatings comprised from HfO2 and SiO2 thin-film pairs. To separate contributions from the bulk of the film and from interfacial areas, absorption and damage threshold measurements were performed for a one-wave (355-nm wavelength) thick, HfO2 single-layer film and for a film containing seven narrow HfO2 layers separated by SiO2 layers. The seven-layer film was designed to have a total optical thickness of HfO2 layers, equal to one wave at 355 nm and an E-field peak and average intensity similarmore » to a single-layer HfO2 film. Absorption in both types of films was measured using laser calorimetry and photothermal heterodyne imaging. The results showed a small contribution to total absorption from thin-film interfaces as compared to HfO2 film material. The relevance of obtained absorption data to coating near-UV, nanosecond-pulse laser damage was verified by measuring the damage threshold and characterizing damage morphology. The results of this study revealed a higher damage resistance in the seven-layer coating as compared to the single-layer HfO2 film in both sputtered and evaporated coatings. The results are explained through the similarity of interfacial film structure with structure formed during the codeposition of HfO2 and SiO2 materials.« less

  17. Nuclear-magnetic-resonance characterization of doped SiO2 films used in integrated circuits

    NASA Astrophysics Data System (ADS)

    Schilling, Frederic C.; Steiner, Kurt G.; Obeng, Yaw S.

    1995-07-01

    Phosphorus-doped silicon dioxide dielectric films, prepared by plasma-enhanced chemical-vapor deposition at low temperature (400 °C), play a critical role in the reliability of very large scale integration devices. The phosphorus in the phosphosilicate glass (PSG) neutralizes the effect of mobile ion species and improves the glass flow, resulting in better gap filling and improved planarization. To extract the maximum contribution from this and other doped films (boron and germanium doped) in advanced sub-0.5 μm complimentary metal-oxide-semiconductor technologies, it is necessary to understand dopant incorporation and the effects of variation in the exposure to water, dopant concentration, and high-temperature annealing. An analysis of PSG by 1H, 29Si, and 31P solid-state nuclear magnetic resonance establishes the chemistry of the phosphorus dopant incorporation and the effect of moisture on the glass structures. Exposure to water results in a depolymerization of the PSG structures and a concurrent decrease in the crosslink density of the glass network. Similar concentrations of silanols are observed in both doped and undoped samples of SiO2. An increase in silanol concentration is found in P-doped glass after exposure to moisture in air. The level of exposure to water will determine the extent of structural changes in the dielectric film. Variations in this exposure can be expected to produce variability in the glass flow and other properties of the dielectric.

  18. Nuclear-magnetic-resonance characterization of doped SiO2 films used in integrated circuits

    NASA Astrophysics Data System (ADS)

    Schilling, Frederic C.; Steiner, Kurt G.; Obeng, Yaw S.

    1995-09-01

    Phosphorus-doped silicon dioxide dielectric films, prepared by plasma-enhanced chemical-vapor deposition at low temperature (400 °C), play a critical role in the reliability of very large scale integration devices. The phosphorus in the phosphosilicate glass (PSG) neutralizes the effect of mobile ion species and improves the glass flow, resulting in better gap filling and improved planarization. To extract the maximum contribution from this and other doped films (boron and germanium doped) in advanced sub-0.5 μm complimentary metal-oxide-semiconductor technologies, it is necessary to understand dopant incorporation and the effects of variation in the exposure to water, dopant concentration, and high-temperature annealing. An analysis of PSG by 1H, 29Si, and 31P solid-state nuclear magnetic resonance establishes the chemistry of the phosphorus dopant incorporation and the effect of moisture on the glass structures. Exposure to water results in a depolymerization of the PSG structures and a concurrent decrease in the crosslink density of the glass network. Similar concentrations of silanols are observed in both doped and undoped samples of SiO2. An increase in silanol concentration is found in P-doped glass after exposure to moisture in air. The level of exposure to water will determine the extent of structural changes in the dielectric film. Variations in this exposure can be expected to produce variability in the glass flow and other properties of the dielectric.

  19. Solution-processed crack-free oxide films formed using SiO2 nanoparticles and organoalkoxysiloxane precursors

    NASA Astrophysics Data System (ADS)

    Na, Moonkyong; Rhee, Shi-Woo

    2015-07-01

    Crack-free uniform oxide films were deposited by spin-on-glass method using a mixture solution of organoalkoxysiloxane network former and SiO2 nanoparticles. In the range of molar ratio of SiO2 nanoparticles to oragnoalkoxysiloxanes between 0.6:1 and 1:1, stable sols were formed and smooth and uniform oxide films could be obtained. Fourier-transform infrared (FT-IR) spectroscopy was used to investigate the chemical properties of the films, and we found that Sisbnd Osbnd Si structures were effectively formed via condensation reactions during curing at 150 °C. The effect of three different organic side groups in the organoalkoxsiloxane on the film properties was investigated. Precursors containing methyl groups effectively formed Sisbnd Osbnd Si network with SiO2 nanoparticles, which was confirmed by the increased intensity of the Sisbnd O asymmetric stretching mode at 1080 cm-1 in the FT-IR spectra. Smooth and continuous films were obtained using precursors containing methyl and phenyl groups, with root-mean-square surface roughness of 1.05 nm (methyl precursor) and 1.16 nm (phenyl precursor). The shrinkage of the oxide film formed with phenyl groups was less than 1%. The dielectric properties of the oxide films were characterized, and we observed leakage currents in the range of 10-9 to 10-8 A/cm2 just prior to the dielectric breakdown with the films formed using precursors containing methyl and phenyl groups

  20. Preparation and characterization of SiO2/TiO2/methylcellulose hybrid thick films for optical waveguides

    NASA Astrophysics Data System (ADS)

    Yang, Jun; Zhang, Xinyu; Wang, Pei; Ming, Hai; Wu, Yunxia; Xie, Jianping; Zhang, Junying

    2005-07-01

    SiO2/TiO2/methylcellulose composite materials processed by the sol-gel technique were studied for optical waveguide applications. With the help of methylcellulose, an organic binder, SiO2/TiO2/methylcellulose hybrid thick films were prepared by a single spin-coating processes. After annealing at 70 Celsius degree for an hour, 2.5-?m crack-free and dense organic--inorganic hybrid optical films with a refractive index of 1.537 were achieved. Optical losses of plane waveguide made up of those films and ordinary slide glass substrate are around 0.3 dB/cm at 650 nm. Scanning electronmicroscopy (SEM) and UV-visible spectroscopy (UV-VIS), have been used to characterize the thick films.

  1. Unconventional magnetization of Fe3O4 thin film grown on amorphous SiO2 substrate

    NASA Astrophysics Data System (ADS)

    Yin, Jia-Xin; Liu, Zhi-Guo; Wu, Shang-Fei; Wang, Wen-Hong; Kong, Wan-Dong; Richard, Pierre; Yan, Lei; Ding, Hong

    2016-06-01

    High quality single crystal Fe3O4 thin films with (111) orientation had been prepared on amorphous SiO2 substrate by pulsed laser deposition. The magnetization properties of the films are found to be unconventional. The Verwey transition temperature derived from the magnetization jump is around 140K, which is higher than the bulk value and it can be slightly suppressed by out-plane magnetic field; the out-of-plane magnetization, which is unexpectedly higher than the in-plane value, is also significantly increased as compared with the bulk value. Our findings highlight the unusual magnetization of Fe3O4 thin film grown on the amorphous SiO2 substrate.

  2. Desorption induced by electronic transitions of Na from SiO2: relevance to tenuous planetary atmospheres.

    NASA Astrophysics Data System (ADS)

    Yakshinskiy, B. V.; Madey, T. E.

    2000-04-01

    The authors have studied the desorption induced by electronic transitions (DIET) of Na adsorbed on model mineral surfaces, i.e. amorphous, stoichiometric SiO2 films. They find that electron stimulated desorption (ESD) of atomic Na occurs for electron energy thresholds as low as ≡4 eV, that desorption cross-sections are high (≡1×10-19cm2 at 11 eV), and that desorbing atoms are 'hot', with suprathermal velocities. The estimated Na desorption rate from the lunar surface via ESD by solar wind electrons is a small fraction of the rate needed to sustain the Na atmosphere. However, the solar photon flux at energies ≥5 eV exceeds the solar wind electron flux by orders of magnitude; there are sufficient ultraviolet photons incident on the lunar surface to contribute substantially to the lunar Na atmosphere via PSD of Na from the surface.

  3. Lateral protonic/electronic hybrid oxide thin-film transistor gated by SiO2 nanogranular films

    NASA Astrophysics Data System (ADS)

    Zhu, Li Qiang; Chao, Jin Yu; Xiao, Hui

    2014-12-01

    Ionic/electronic interaction offers an additional dimension in the recent advancements of condensed materials. Here, lateral gate control of conductivities of indium-zinc-oxide (IZO) films is reported. An electric-double-layer (EDL) transistor configuration was utilized with a phosphorous-doped SiO2 nanogranular film to provide a strong lateral electric field. Due to the strong lateral protonic/electronic interfacial coupling effect, the IZO EDL transistor could operate at a low-voltage of 1 V. A resistor-loaded inverter is built, showing a high voltage gain of ˜8 at a low supply voltage of 1 V. The lateral ionic/electronic coupling effects are interesting for bioelectronics and portable electronics.

  4. Self-assembled dual in-plane gate thin-film transistors gated by nanogranular SiO2 proton conductors for logic applications.

    PubMed

    Zhu, Li Qiang; Sun, Jia; Wu, Guo Dong; Zhang, Hong Liang; Wan, Qing

    2013-03-01

    Phosphorus (P)-doped nanogranular SiO(2) films are deposited by plasma-enhanced chemical vapor deposition at room temperature, and a high proton conductivity of ~5.6 × 10(-4) S cm(-1) is measured at room temperature with a relative humidity of 70%. The accumulation of protons at the SiO(2)/indium-zinc-oxide (IZO) interface induces a large electric-double-layer (EDL) capacitance. Thin-film transistors (TFTs) with two in-plane gates are self-assembled on transparent conducting glass substrates. The large EDL capacitance can effectively modulate the IZO channel with a current ON/OFF ratio of >10(7). Such TFTs calculate dual input signals at the gate level coupled with a floating gate, analogous to that of neuron MOS (vMOS). AND logic is demonstrated on the neuron TFTs. Such neuron TFTs gated by P-doped nanogranular SiO(2) shows an effective electrostatic modulation on conductivities of oxide semiconductors, which is meaningful for portable chemical-biological sensing applications. PMID:23364424

  5. Self-assembled dual in-plane gate thin-film transistors gated by nanogranular SiO2 proton conductors for logic applications

    NASA Astrophysics Data System (ADS)

    Zhu, Li Qiang; Sun, Jia; Wu, Guo Dong; Zhang, Hong Liang; Wan, Qing

    2013-02-01

    Phosphorus (P)-doped nanogranular SiO2 films are deposited by plasma-enhanced chemical vapor deposition at room temperature, and a high proton conductivity of ~5.6 × 10-4 S cm-1 is measured at room temperature with a relative humidity of 70%. The accumulation of protons at the SiO2/indium-zinc-oxide (IZO) interface induces a large electric-double-layer (EDL) capacitance. Thin-film transistors (TFTs) with two in-plane gates are self-assembled on transparent conducting glass substrates. The large EDL capacitance can effectively modulate the IZO channel with a current ON/OFF ratio of >107. Such TFTs calculate dual input signals at the gate level coupled with a floating gate, analogous to that of neuron MOS (vMOS). AND logic is demonstrated on the neuron TFTs. Such neuron TFTs gated by P-doped nanogranular SiO2 shows an effective electrostatic modulation on conductivities of oxide semiconductors, which is meaningful for portable chemical-biological sensing applications.

  6. Nanostructured Er3+-doped SiO2-TiO2 and SiO2-TiO2-Al2O3 sol-gel thin films for integrated optics

    NASA Astrophysics Data System (ADS)

    Predoana, Luminita; Preda, Silviu; Anastasescu, Mihai; Stoica, Mihai; Voicescu, Mariana; Munteanu, Cornel; Tomescu, Roxana; Cristea, Dana

    2015-08-01

    The nanostructured multilayer silica-titania or silica-titania-alumina films doped with Er3+ were prepared by sol-gel method. The sol-gel method is a flexible and convenient way to prepare oxide films on several types of substrates, and for this reason it was extensively investigated for optical waveguides fabrication. The selected molar composition was 90%SiO2-10%TiO2 or 85%SiO2-10%TiO2-5% Al2O3 and 0.5% Er2O3. The films were characterized by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Spectroellipsometry (SE), as well as by Atomic Force Microscopy (AFM) and photoluminescence (PL). The films deposited on Si/SiO2 substrate by dip-coating or spin-coating, followed by annealing at 900 °C, presented homogenous and continuous surface and good adherence to the substrate. Differences were noticed in the structure and properties of the prepared films, depending on the composition and the number of deposited layers. Channel optical waveguides were obtained by patterning Er3+-doped SiO2-TiO2 and SiO2-TiO2-Al2O3 sol-gel layers deposited on oxidized silicon wafers.

  7. High-Sensitivity Infrared Characterization of Ultrathin SiO2 Film by Grazing Internal Reflection Method

    NASA Astrophysics Data System (ADS)

    Matsui, Yuichi; Miyagawa, Yasuo; Izumitani, Junko; Okuyama, Masanori; Hamakawa, Yoshihiro

    1992-02-01

    A new kind of high-sensitivity infrared spectroscopy for characterizing SiO2 ultrathin film of 2-10 nm thickness of metal-SiO2-Si structure has been developed by the grazing internal reflection (GIR) method. At a large incident angle of 80 degrees onto the metal-SiO2-Si interface having SiO2 film of 2 nm thickness, a very large absorption of about 90% has been obtained at around 1240 cm-1 corresponding to the Si-O-Si bond. The measured data including the incident angle dependence agree well with the calculated values analyzed by Fresnel’s formula. Moreover, slight absorptions of Si-H and Si-OH have easily been measured as a strong signal change of about 1-7%.

  8. Tip-Induced Deformation of Graphene on SiO2 Assessed by Capacitance Measurement

    NASA Astrophysics Data System (ADS)

    Naitou, Yuichi

    2012-11-01

    Tip-induced deformation of graphene on a SiO2 substrate was probed through a combination of scanning capacitance microscopy (SCM) and dynamic force microscopy (DFM). Spectroscopic analysis revealed that the resonant frequency shift (Δf) of the probe tip oscillation and the modulated capacitance (ΔC) simultaneously measured on graphene depend on the externally applied bias voltage while keeping the tip-sample distance constant. This finding is interpreted as a result of a local displacement of the graphene surface caused by the electrostatic force between the probe tip and graphene. The approach curve of the SCM tip toward graphene can be used to calibrate the observed ΔC spectra, quantitatively yielding an average deformation of approximately 0.31 nm in trilayer graphene and 0.21 nm in single-layer graphene.

  9. Solid-state dewetting of ultra-thin Au films on SiO2 and HfO2

    NASA Astrophysics Data System (ADS)

    Seguini, G.; Llamoja Curi, J.; Spiga, S.; Tallarida, G.; Wiemer, C.; Perego, M.

    2014-12-01

    Ultra-thin Au films with thickness (h) ranging from 0.5 to 6.0 nm were deposited at room temperature (RT) by means of e-beam evaporation on SiO2 and HfO2. Due to the natural solid-state dewetting (SSD) of the as-deposited films, Au nanoparticles (NPs) were formed on the substrates. By properly adjusting the h value, the size and the density of the Au NPs can be finely tuned. For h = 0.5 nm, spherical-like Au NPs with diameter below 5 nm and density in the order of 1012 Au NPs cm-2 were obtained without any additional thermal treatment independently from the substrate. The dependence of the Au NPs characteristics on the substrate starts to be effective for h ≥ 1.0 nm where the Au NPs diameter is in the 5-10 nm range and the density is around 1011 Au NPs cm-2. The effect of a subsequent high temperature (400-800 °C) annealing in N2 atmosphere on the Au NPs was investigated as well. For h ≤ 1.0 nm, the Au NPs characteristics evidenced an excellent thermal stability. Whereas the thermal treatment affects the cristallinity of the Au NPs. For the thicker films (2.0 ≤ h ≤ 6.0 nm), the thermal treatment becomes effective to induce the SSD. The proposed methodology can be exploited for the synthesis of Au NPs with diameter below 10 nm on different substrates at RT.

  10. Influence of plasma-generated negative oxygen ion impingement on magnetron sputtered amorphous SiO2 thin films during growth at low temperatures

    NASA Astrophysics Data System (ADS)

    Macias-Montero, M.; Garcia-Garcia, F. J.; Álvarez, R.; Gil-Rostra, J.; González, J. C.; Cotrino, J.; Gonzalez-Elipe, A. R.; Palmero, A.

    2012-03-01

    Growth of amorphous SiO2 thin films deposited by reactive magnetron sputtering at low temperatures has been studied under different oxygen partial pressure conditions. Film microstructures varied from coalescent vertical column-like to homogeneous compact microstructures, possessing all similar refractive indexes. A discussion on the process responsible for the different microstructures is carried out focusing on the influence of (i) the surface shadowing mechanism, (ii) the positive ion impingement on the film, and (iii) the negative ion impingement. We conclude that only the trend followed by the latter and, in particular, the impingement of O- ions with kinetic energies between 20 and 200 eV, agrees with the resulting microstructural changes. Overall, it is also demonstrated that there are two main microstructuring regimes in the growth of amorphous SiO2 thin films by magnetron sputtering at low temperatures, controlled by the amount of O2 in the deposition reactor, which stem from the competition between surface shadowing and ion-induced adatom surface mobility.

  11. Comparison of the Sputter Rates of Oxide Films Relative to the Sputter Rate of SiO2

    SciTech Connect

    Baer, Donald R.; Engelhard, Mark H.; Lea, Alan S.; Nachimuthu, Ponnusamy; Droubay, Timothy C.; Kim, J.; Lee, B.; Mathews, C.; Opila, R. L.; Saraf, Laxmikant V.; Stickle, William F.; Wallace, Robert; Wright, B. S.

    2010-09-02

    Because of the increasing technological importance of oxide films for a variety of applications, there is a growing interest in knowing the sputter rates for a wide variety of oxides. To support needs of users of the Environmental Molecular Sciences Laboratory (EMSL) User facility as well as our research programs, we have made a series of measurements of the sputter rates for oxide films that have been grown by oxygen plasma assisted molecular beam epitaxy (OPA-MBE), pulsed laser deposition (PLD), Atomic Layer Deposition (ALD), electrochemical oxidation, or sputter deposition. The sputter rates for these oxide films were determined in comparison to the sputter rates for thermally grown SiO2, a common sputter rate reference material. The film thicknesses and densities of these films were usually measured using x-ray reflectivity (XRR). These samples were mounted in an x-ray photoelectron spectroscopy (XPS) system or an Auger electron spectrometer for sputtering measurements using argon ion sputtering. Although the primary objective was to determine relative sputter rates at a fixed angle, the measurements were also used to determine: i) the angle dependence of the relative sputter rates; ii) the energy dependence of the relative sputter rates; and iii) the extent of ion beam reduction for the various oxides. Materials examined include: SiO2 (reference films), Al2O3, CeO2, Cr2O3, Fe2O3, HfO2, ITO (In-Sn-oxide) Ta2O5, TiO2 (anatase and rutile) and ZnO. We find that the sputter rates for the oxides can vary up to a factor of two (usually slower) from that observed for SiO2. The ratios of sputter rates to SiO2 appear to be relatively independent of ion beam energy for the range of 1kV to 4 kV and for incident angles of less than 50º. As expected, the ion beam reduction of the oxides varies with the sputter angle. These studies demonstrate that we can usually obtain sputter rate reproducibility better than 5% for similar oxide films.

  12. Well-organized meso-macroporous TiO2/SiO2 film derived from amphiphilic rubbery comb copolymer.

    PubMed

    Jeon, Harim; Lee, Chang Soo; Patel, Rajkumar; Kim, Jong Hak

    2015-04-15

    We report the facile synthesis of a well-organized meso-macroporous TiO2/SiO2 thin film with high porosity and good interconnectivity from a binary mixture (i.e., titania precursor and polymer template). Our process is based on self-assembly of the amphiphilic rubbery comb copolymer, poly(dimethylsiloxane)-g-poly(oxyethylene methacrylate) (PDMS-g-POEM) with titanium tetraisopropoxide (TTIP). SiO2 is self-provided by thermal oxidation of PDMS chains during calcination under air. The selective, preferential interaction between TTIP and the hydrophilic POEM chains was responsible for the formation of well-organized TiO2/SiO2 films, as supported by transmission electron microscopy, scanning electron microscopy, X-ray photospectroscopy, and X-ray diffraction analyses. We investigated in detail the effect of precursor content, solvent type, and polymer concentration on thin film morphology. Photodegradation of methyl orange by the well-organized meso-macroporous TiO2/SiO2 film was greater than that of a dense TiO2 film prepared without PDMS-g-POEM as well as a SiO2-etched TiO2 film. These results indicate that the well-organized structure and SiO2 doping of the TiO2 film play a pivotal role in enhancing its photocatalytic properties. PMID:25805232

  13. Carrier and heat transport properties of polycrystalline GeSn films on SiO2

    NASA Astrophysics Data System (ADS)

    Uchida, Noriyuki; Maeda, Tatsuro; Lieten, Ruben R.; Okajima, Shingo; Ohishi, Yuji; Takase, Ryohei; Ishimaru, Manabu; Locquet, Jean-Pierre

    2015-12-01

    We evaluated the potential of polycrystalline (poly-) GeSn as channel material for the fabrication of thin film transistors (TFTs) at a low thermal budget (<600 °C). Poly-GeSn films with a grain size of ˜50 nm showed a carrier mobility of ˜30 cm2 V-1 s-1 after low-temperature annealing at 475-500 °C. Not only carrier mobility but also thermal conductivity of the films is important in assessing the self-heating effect of the poly-GeSn channel TFT. The thermal conductivity of the poly-GeSn films is 5-9 W m-1 K-1, which is significantly lower compared with 30-60 W m-1 K-1 of bulk Ge; this difference results from phonon scattering at grain boundaries and Sn interstitials. The poly-GeSn films have higher carrier mobility and thermal conductivity than poly-Ge films annealed at 600 °C, because of the improved crystal quality and coarsened grain size resulting from Sn-induced crystallization. Therefore, the poly-GeSn film is well-suited as channel material for TFTs, fabricated with a low thermal budget.

  14. Design of high-performance memristor cell using W-implanted SiO2 films

    NASA Astrophysics Data System (ADS)

    Li, Wenqing; Liu, Xinqiang; Wang, Yongqiang; Dai, Zhigao; Wu, Wei; Cheng, Li; Zhang, Yupeng; Liu, Qi; Xiao, Xiangheng; Jiang, Changzhong

    2016-04-01

    Highly reproducible bipolar resistance switching was demonstrated in a composite material of W-implanted silicon dioxide. Because of its excellent dielectric properties, SiO2 was selected as the sole active material for fabricating the resistance switching devices. The device employed a metal-insulator-semiconductor structure, showing an excellent resistance switching performance (the ON/OFF ratio is close to ˜106). In addition, this sandwich structure device shows a forming-free resistance switching behavior. The overall device performance of the SiO2-based memristor has the potential to open up a new avenue to a large-scale high-performance resistive random access memory, which could significantly impact their existing applications.

  15. Synthesis of mesoporous TiO2/SiO2 hybrid films as an efficient photocatalyst by polymeric micelle assembly.

    PubMed

    Li, Yunqi; Bastakoti, Bishnu Prasad; Imura, Masataka; Hwang, Soo Min; Sun, Ziqi; Kim, Jung Ho; Dou, Shi Xue; Yamauchi, Yusuke

    2014-05-12

    Thermally stable mesoporous TiO2/SiO2 hybrid films with pore size of 50 nm have been synthesized by adopting the polymeric micelle-assembly method. A triblock copolymer, poly(styrene-b-2-vinyl pyridine-b-ethylene oxide), which serves as a template for the mesopores, was utilized to form polymeric micelles. The effective interaction of titanium tetraisopropoxide (TTIP) and tetraethyl orthosilicate (TEOS) with the polymeric micelles enabled us to fabricate stable mesoporous films. By changing the molar ratio of TEOS and TTIP, several mesoporous TiO2/SiO2 hybrid films with different compositions can be synthesized. The presence of amorphous SiO2 phase effectively retards the growth of anatase TiO2 crystal in the pore walls and retains the original mesoporous structure, even at higher temperature (650 °C). These TiO2/SiO2 hybrid films are of very high quality, without any cracks or voids. The addition of SiO2 phase to mesoporous TiO2 films not only adsorbs more organic dyes, but also significantly enhances the photocatalytic activity compared to mesoporous pure TiO2 film without SiO2 phase. PMID:24710980

  16. Phase transformation behaviors of SiO2 doped Ge2Sb2Te5 films for application in phase change random access memory

    NASA Astrophysics Data System (ADS)

    Ryu, Seung Wook; Oh, Jin Ho; Lee, Jong Ho; Choi, Byung Joon; Kim, Won; Hong, Suk Kyoung; Hwang, Cheol Seong; Kim, Hyeong Joon

    2008-04-01

    The improvement in the phase change characteristics of Ge2Sb2Te5 (GST) films for phase change random access memory applications was investigated by doping the GST films with SiO2 using cosputtering at room temperature. As the sputtering power of SiO2 increased from 0to150W, the activation energy for crystallization increased from 2.1±0.2to3.1±0.15eV. SiO2 inhibited the crystallization of the amorphous GST films, which improved the long term stability of the metastable amorphous phase. The melting point decreased with increasing concentration of SiO2, which reduced the power consumption as well as the reset current.

  17. Optical, Structural and Electrochemical Properties of CeO2--Al2O3--SiO2 Thin Films

    NASA Astrophysics Data System (ADS)

    Saygin Hinczewski, Dursen; Hinczewski, Michael; Sorar, Idris; Pehlivan, Esat; Tepehan, Fatma Z.; Tepehan, Galip G.

    2008-03-01

    CeO2 thin films can be used as counter-electrodes in electrochromic devices, but have the disadvantage of slow reaction kinetics. Thus research has shifted to composite CeO2 films as more promising ion-storage candidates. In this work, we examine the sol-gel coating and characterization of CeO2--Al2O3--SiO2 transparent thin films deposited onto glass microslides and indium-tin-oxide-coated conducting glass. We investigate the evolution of the surface morphology, and the optical, structural and electrochemical properties of the films with varying Si-Al-Ce mol ratios. In particular we find the formation of novel complex phase-segregated structures at the surface, which have the potential for enhancing Li ion insertion/extraction.

  18. The role of film interfaces in near-ultraviolet absorption and pulsed-laser damage in ion-beam-sputtered coatings based on HfO2/SiO2 thin-film pairs

    DOE PAGESBeta

    Ristau, Detlev; Papernov, S.; Kozlov, A. A.; Oliver, J. B.; Smith, C.; Jensen, L.; Gunster, S.; Madebach, H.

    2015-11-23

    The role of thin-film interfaces in the near-ultraviolet absorption and pulsed-laser–induced damage was studied for ion-beam–sputtered and electron-beam–evaporated coatings comprised from HfO2 and SiO2 thin-film pairs. To separate contributions from the bulk of the film and from interfacial areas, absorption and damage-threshold measurements were performed for a one-wave (355-nm wavelength) thick, HfO2 single-layer film and for a film containing seven narrow HfO2 layers separated by SiO2 layers. The seven-layer film was designed to have a total optical thickness of HfO2 layers, equal to one wave at 355 nm and an E-field peak and average intensity similar to a single-layer HfO2more » film. Absorption in both types of films was measured using laser calorimetry and photothermal heterodyne imaging. The results showed a small contribution to total absorption from thin-film interfaces, as compared to HfO2 film material. The relevance of obtained absorption data to coating near-ultraviolet, nanosecond-pulse laser damage was verified by measuring the damage threshold and characterizing damage morphology. The results of this study revealed a higher damage resistance in the seven-layer coating as compared to the single-layer HfO2 film in both sputtered and evaporated coatings. Here, the results are explained through the similarity of interfacial film structure with structure formed during the co-deposition of HfO2 and SiO2 materials.« less

  19. The role of film interfaces in near-ultraviolet absorption and pulsed-laser damage in ion-beam-sputtered coatings based on HfO2/SiO2 thin-films pairs

    DOE PAGESBeta

    Papernov, S.; Kozlov, A. A.; Oliver, J. B.; Smith, C.; Jensen, L.; Ristau, D.; Gunster, S.; Madebach, H.

    2015-11-23

    Here, the role of thin-film interfaces in the near-ultraviolet absorption and pulsed-laser–induced damage was studied for ion-beam–sputtered and electron-beam–evaporated coatings comprised from HfO2 and SiO2 thin-film pairs. To separate contributions from the bulk of the film and from interfacial areas, absorption and damage-threshold measurements were performed for a one-wave (355-nm wavelength) thick, HfO2 single-layer film and for a film containing seven narrow HfO2 layers separated by SiO2 layers. The seven-layer film was designed to have a total optical thickness of HfO2 layers, equal to one wave at 355 nm and an E-field peak and average intensity similar to a single-layermore » HfO2 film. Absorption in both types of films was measured using laser calorimetry and Photothermal heterodyne imaging. The results showed a small contribution to total absorption from thin-film interfaces, as compared to HfO2 film material. The relevance of obtained absorption data to coating near-ultraviolet, nanosecond-pulse laser damage was verified by measuring the damage threshold and characterizing damage morphology. The results of this study revealed a higher damage resistance in the seven-layer coating as compared to the single-layer HfO2 film in both sputtered and evaporated coatings. The results are explained through the similarity of interfacial film structure with structure formed during the co-deposition of HfO2 and SiO2 materials.« less

  20. State Transition of a Defect Causing Random-Telegraph-Noise Fluctuation in Stress-Induced Leakage Current of Thin SiO2 Films in a Metal-Oxide-Silicon Structure

    NASA Astrophysics Data System (ADS)

    Ishida, Takeshi; Tega, Naoki; Mori, Yuki; Miki, Hiroshi; Mine, Toshiyuki; Kume, Hitoshi; Torii, Kazuyoshi; Yamada, Ren-ichi; Shiraishi, Kenji

    2013-11-01

    Dynamic fluctuation in stress-induced leakage current - called “variable stress-induced leakage current” - in a gate oxide of a metal-oxide-semiconductor structure was investigated. Variable stress-induced leakage current is attributed to random telegraph noise, which is associated with the state-transition of a single defect. To analyze the mechanism of the state-transition, dependence of state-transition probabilities on gate current and on temperature were investigated. These dependences indicate that the state-transition mechanism is a defect-structure transition by charge collision.

  1. Robust topological surface states of Bi2Se3 thin films on amorphous SiO2/Si substrate and a large ambipolar gating effect

    NASA Astrophysics Data System (ADS)

    Bansal, Namrata; Koirala, Nikesh; Brahlek, Matthew; Han, Myung-Geun; Zhu, Yimei; Cao, Yue; Waugh, Justin; Dessau, Daniel S.; Oh, Seongshik

    2014-06-01

    The recent emergence of topological insulators (TI) has spurred intensive efforts to grow TI thin films on various substrates. However, little is known about how robust the topological surface states (TSS) are against disorders and other detrimental effects originating from the substrates. Here, we report the observation of a well-defined TSS on Bi2Se3 films grown on amorphous SiO2 (a-SiO2) substrates and a large gating effect on these films using the underneath doped-Si substrate as the back gate. The films on a-SiO2 were composed of c-axis ordered but random in-plane domains. However, despite the in-plane randomness induced by the amorphous substrate, the transport properties of these films were superior to those of similar films grown on single-crystalline Si(111) substrates, which are structurally better matched but chemically reactive with the films. This work sheds light on the importance of chemical compatibility, compared to lattice matching, for the growth of TI thin films, and also demonstrates that the technologically important and gatable a-SiO2/Si substrate is a promising platform for TI films.

  2. An influence of technological parameters of plasma-chemical deposition of SiO2 films on their electro-physical properties

    NASA Astrophysics Data System (ADS)

    Romanov, A. A.; Serkov, A. V.; Hruleva, E. S.

    2016-07-01

    In this article a formation process of dielectric films on silicon (100) and silicon carbide using plasma-chemical deposition is described. Experimental relationships of SiO2 films thickness and main technological parameters are presented. Values of electro-physical parameters of films are measured.

  3. Magnetic-field-induced photocurrent in metal-dielectric-semiconductor heterostructures based on cobalt nanoparticles SiO2(Co)/GaAs

    NASA Astrophysics Data System (ADS)

    Pavlov, V. V.; Lutsev, L. V.; Usachev, P. A.; Astretsov, A. A.; Stognij, A. I.; Novitskii, N. N.; Pisarev, R. V.

    2016-02-01

    Magnetic-field influence on photocurrent in heterostructures of silicon dioxide films with cobalt nanoparticles SiO2(Co) grown on gallium arsenide GaAs substrate has been studied in the avalanche regime at room temperature. High values of magnetic-field-induced photocurrent were found in the vicinity and above the GaAs bandgap of ∼1.4 eV. For photon energies E > 1.4 eV the photocurrent significantly increases, while the avalanche process is suppressed by the magnetic field, and the current flowing through the heterostructure decreases. The photocurrent is enhanced in the SiO2(Co 60 at%)/GaAs heterostructure at the magnetic field H=1.65 kOe by factor of about 10 for the photon energy E=1.5 eV. This phenomenon is explained by a model based on electronic transitions in magnetic fields with the spin-dependent recombination process at deep impurity centers in the SiO2(Co)/GaAs interface region.

  4. Highly effective strain-induced band-engineering of (111) oriented, direct-gap GeSn crystallized on amorphous SiO2 layers

    NASA Astrophysics Data System (ADS)

    Li, Haofeng; Wang, Xiaoxin; Liu, Jifeng

    2016-03-01

    We demonstrate highly effective strain-induced band-engineering of (111) oriented direct-gap Ge1-xSnx thin films (0.074 < x < 0.085) crystallized on amorphous SiO2 towards 3D photonic integration. Due to a much smaller Poisson's ratio for (111) vs. (100) orientation, 0.44% thermally induced biaxial tensile strain reduces the direct-gap by 0.125 eV towards enhanced direct-gap semiconductor properties, twice as effective as the tensile strain in Ge(100) films. Correspondingly, the optical response is extended to λ = 2.8 μm. A dilatational deformation potential of a = -12.8 ± 0.8 eV is derived. These GeSn films also demonstrate high thermal stability, offering both excellent direct-gap optoelectronic properties and fabrication/operation robustness for integrated photonics.

  5. The formation of nano-size SiO2 thin film on an aluminum plate with hexamethyldisilazane (HMDSA) and hexamethyldisiloxane (HMDSO)

    NASA Astrophysics Data System (ADS)

    Ma, H. K.; Zhao, E.; Yeh, C. L.; Chung, K. M.

    2003-02-01

    This study is using HMDSA (C6H19NSi2) or HMDSO (C6H18OSi2) vapor into C3H8/air premixed flames to form SiO2 thin film on the surface of an aluminum plate. With the addition of HMDSO or HMDSA to premixed flames, an orange secondary flame or a flame brush appeared and was contributed to the formation of SiO2 particles. Based upon the EDS, XPS and FTIR analysis, it is believed that the synthesized products consist of mainly SiO2 and a small amount of SiO. The pure SiO2 crystal structure, was proved by XRD analysis, which may form from the SiO2 amorphous structure after high temperature (1300°C) thermal treatment. The nano-size SiO2 particles, which ranged from 2.5-25 nm, are proved by analysis of the BET and TEM. A 2-D CFD-RC code with 12 reduced chemical reaction mechanism, based upon the SIMPLER procedure, was successfully employed to predict the flame temperature and both of the SiO2 and SiO concentration profiles. Compared with the experimental results, the calculated temperature profiles in the post-flame region are in good agreement with the measured data and observation phenomena.

  6. The effect of SiO2 on TiO2 up-conversion photoluminescence film

    NASA Astrophysics Data System (ADS)

    Meng, Xiaoqi; Li, Lianqiang; Zou, Kaishun; Liu, Juncheng

    2014-11-01

    In order to increase the photoelectric conversion efficiency of silicon solar cell, the up-conversion film has been tried to enhance the response of the solar cells to the infrared band. Yb3+, Er3+ co-doped SiO2/TiO2 composite films with different Ti/Si molar ratio were deposited on the glass substrate with sol-gel method and spin-coating technique. The effect of different molar ratio of Ti/Si on the film's morphology and optical properties was investigated. The morphology, the absorption spectra and photoluminescence (PL) spectra of the film were tested and analyzed. After the film was annealed at 900 °C, the XRD diffraction pattern indicated that rare earths ions have evenly dispersed into the matrix lattice. The FT-IR showed that Si ions entered into the lattice of titanium dioxide, and the Ti-O-Si bonds came into being. When the film pumped with a laser of 980 nm, there were a dominant red emission and several weak green peaks. In addition, with the increase of the mole ratio of Si/Ti, the intensity of the film's up-conversion luminescence increases at first and then decreases. When the molar ratio of Si/Ti is 1/8, the sample had the highest intensity of up-conversion luminescence.

  7. Novel low-stress SiO2-xFx film deposited by room-temperture liquid-phase deposition method

    NASA Astrophysics Data System (ADS)

    Yeh, Ching-Fa; Lin, Shyue-Shyh

    1995-09-01

    To develop a low-stress thin film for micromachined devices, a novel liquid-phase deposition (LPD) SiO2 - xFx technique utilizing silica-saturated H2SiF6 solution with H2O addition only is proposed. Due to extremely low-temperature processing and fluorine incorporation, the stress of the LPD SiO2 - xFx film can be less than 100 MPa. In this paper, we found that the deposition parameter of H2O addition has much efect on the stress of as-deposited LPD oxide. The stress variations with thermal cycling has also been clarified. We found that the LPD SiO2 - xFx film will be a good candidate as low-stress film for micromachined devices.

  8. The reason for the increased threshold switching voltage of SiO2 doped Ge2Sb2Te5 thin films for phase change random access memory

    NASA Astrophysics Data System (ADS)

    Ryu, Seung Wook; Lee, Jong Ho; Ahn, Young Bae; Kim, Choon Hwan; Yang, Bong Seob; Kim, Gun Hwan; Kim, Soo Gil; Lee, Se-Ho; Hwang, Cheol Seong; Kim, Hyeong Joon

    2009-09-01

    This study examined the threshold switching voltage (VT) of 150 nm thick SiO2 doped Ge2Sb2Te5 (SGST) films for phase change random access memory applications. The VT of the SGST films increased from ˜0.9 V (for GST) to ˜1.5 V with increasing SiO2 content. The optical band gap and Urbach edge of the SGST films were similar regardless of the SiO2 concentration. The dielectric constant decreased by ˜37% and the electrical resistivity increased by ˜19%. The increase in VT of SGST films is associated with an effective increase in electric field and the decreased generation rate caused by impact ionization.

  9. Effect of carbon enrichment induced by photoresist on highly selective SiO2 etching

    NASA Astrophysics Data System (ADS)

    Chu, Changwoong; Chi, Kyeong-Koo; Moon, Joo-Tae

    2002-11-01

    We propose two models to discuss the behavior of the selective etching of SiO2 to the underlying Si3N4 with changing wafer surface temperatures. For this investigation, three specimens, SiO2, Si3N4, and poly-Si, which are nonpatterned, photoresist-patterned, and poly-silicon-patterned, respectively, have been etched in a surface wave plasma system equipped with an electrostatic chuck for wafer temperature control. The coolant temperature, which controls the wafer temperature, has been changed from -20 to 50 °C. For the nonpatterned wafer, the etch rates of SiO2, Si3N4, and poly-Si increase and the selectivities decreases with wafer temperature. However, for the samples patterned with either photoresist or poly-Si, the etch rates of SiO2 decrease with wafer temperature. The temperature rise also leads to an enhancement of selectivity of SiO2/Si3N4, and the steeper profile angles. The presence of a masking layer, even for the poly-Si-patterned samples, results in a different etching behavior. This is because the sticking probability of the polymer precursor becomes smaller on the sidewall of the profile with the temperature increase. Therefore the thickness of polymer on the sidewall of the contact hole decreases, and the thickness of polymer on the bottom increases as the wafer temperature goes up. Comparing photoresist-patterned samples with poly-Si-patterned ones, we can corroborate the role of the photoresist mask layer, which provides a higher carbon-to-fluorine ratio at the near surface. The carbon enrichment accelerates more steeply the etch rate decrement of the substrate layer. In summary, there are two main contributions attributed by the substrate temperature: changing the sticking coefficient of the fluorocarbon precursor and enhancing the photoresist erosion.

  10. Sol-gel preparation and characterization of SiO2 coated VO2 films with enhanced transmittance and high thermochromic performance

    NASA Astrophysics Data System (ADS)

    Li, Dezeng; Shan, Yongkui; Huang, Fuqiang; Ding, Shangjun

    2014-10-01

    Vanadium dioxide (VO2) films prepared at low-temperature with a low cost are considerable for energy-saving applications. Here, SiO2 coated VO2 films with clearly enhanced visible transmittance by introducing antireflection coatings (ARCs) and excellent thermochromic performance were present. The VO2 films have been prepared via a stable and low-cost sol-gel synthesis route using vanadium pentaoxide powder as precursor, and their structural, morphological, optical and electrical properties and thermochromic performance were systemically characterized. The resistance of VO2 films varies by 4 orders of magnitude and the transmittance changes from 11.8% to 69.3% at 2500 nm while no significant deviation appears in the visible region during metal-insulator transition (MIT). Nanoporous SiO2 coating with good optical transparency was coated on the surface of VO2 film via sol-gel dip-coating technique to enhance its optical transmittance, and the visible transmittance is increased by 14.6% due to the significantly decreased reflectance. The critical transition temperature (63 °C) and infrared switching properties of VO2 films are not much deteriorated by applying SiO2 layer. The synergistic effect of antireflection and thermochromism on SiO2 coated VO2 films was investigated.

  11. Luminescence of Eu(3+) doped SiO2 Thin Films and Glass Prepared by Sol-gel Technology

    NASA Technical Reports Server (NTRS)

    Castro, Lymari; Jia, Weiyi; Wang, Yanyun; Santiago, Miguel; Liu, Huimin

    1998-01-01

    Trivalent europium ions are an important luminophore for lighting and display. The emission of (5)D0 to (7)F2 transition exhibits a red color at about 610 nm, which is very attractive and fulfills the requirement for most red-emitting phosphors including lamp and cathode ray phosphorescence materials. Various EU(3+) doped phosphors have been developed, and luminescence properties have been extensively studied. On the other hand, sol-gel technology has been well developed by chemists. In recent years, applications of this technology to optical materials have drawn a great attention. Sol-gel technology provides a unique way to obtain homogeneous composition distribution and uniform doping, and the processing temperature can be very low. In this work, EU(3+) doped SiO2 thin films and glasses were prepared by sol-gel technology and their spectroscopic properties were investigated.

  12. Frequency-dependence of the switching voltage in electronic switching of Pt-dispersed SiO2 thin films

    NASA Astrophysics Data System (ADS)

    Choi, Byung Joon; Chen, I.-Wei

    2016-06-01

    The switching time-voltage dependence of electronic resistive switching was studied for understanding the switching dynamics in Pt-dispersed SiO2 thin film devices. Trapezoidal voltage pulses with opposite polarities were consecutively introduced and thereby transient on-switching and offswitching were examined. A prior on-switching voltage determines the off-switching voltage regardless of the sweeping rate of the pulse for the prior on-switching. However, the off-switching voltage was sensitive to the sweeping rate of the subsequent pulses for off-switching. The frequencydependent impedance of both the device and the surrounding circuit element are thought to result in the variation of the off-switching voltage; otherwise, the switching voltage is independent of time.

  13. Effects of applying bias voltage on metal-coated pentacene films on SiO2 studied by hard X-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Hirosawa, Ichiro; Watanabe, Takeshi; Oji, Hiroshi; Yasuno, Satoshi; Koganezawa, Tomoyuki; Tada, Keisuke; Yoshimoto, Noriyuki

    2016-03-01

    The effects of bias voltage application on C 1s photoelectron kinetic energies in Au- and Ag-coated pentacene films on SiO2 were studied by hard X-ray photoelectron spectroscopy. It was observed that the kinetic energies of C 1s were smaller in shallow regions in contact with metals than in mid regions of the pentacene films. The differences in C 1s kinetic energy between the shallow and mid regions of the Ag-coated pentacene films were slightly larger than those of the Au-coated films. The differences in the kinetic energies were decreased by applying negative voltages. The larger effect of voltage application was observed in the Ag-coated film than in the Au-coated film. In addition, partially reduced Si atoms in SiO2 were found at the interface to the pentacene film.

  14. SiO2 Film Grown On Glass In Aqueous Solution

    NASA Astrophysics Data System (ADS)

    Kawahara, Hideo; Goda, Takuji; Nagayama, Hirotsugu; Honda, Hisao; Hishinuma, Akihiro

    1989-12-01

    Si02 film deposition on a glass was made by LPD method (Liquid Phase Deposition). This process involes the deposition and growth of Si02 layer on glass surface while immersing it in hexafluorosilicic acid (H2SiF6) solution supersaturated with silica. In this study, the influence of the impurities and H2SiF6 concentration in the solution on Si02 film properties was investigated by use of SIMS, ICP, Ellipsometry,IRRS and etch rate measurement. The results showed that LPD based Si02 film composition was scarcely affected by the concentration of such impurities as Na, K and Ca contained in the solution. Furthermore it was found that higher H2SiF6 concentration led to Si02 film with lower refractive index and lower etch rate. To have proper understanding of these apparently inconsistent results, the specific role of fluorine contained in the solution and the film was discussed.

  15. Fabrication and super-hydrophilic property of transparent TiO2/SiO2 film from sol-gel process

    NASA Astrophysics Data System (ADS)

    Zhang, Rui; Zhang, Yihe; Xu, Caiyun; Yu, Li; Lv, Fengzhu

    2011-11-01

    A series of transparent and super-hydrophilic TiO2/SiO2 composite films with high adhesion to the glass were fabricated by dipping methods. The sol was prepared using peroxotitanium complex (PTC) as precursor by sol-gel process at low temperature. The properties of transmittance, hydrophility and adhesion were characterized by ultraviolet-visible spectrophotometer, water contact angle and the tape test, and the structure was analyzed by Fourier transform infrared spectroscopy (FTIR). The relationship of structure, surfactant and the compound action of TiO2/SiO2 was investigated. The results indicated that the fabricated films achieved excellent transmittance to slide glass of over 90%. Because of the poor adhesion of pure TiO2 film, the TiO2/SiO2 composite film with polyvinyl alcohol (PVA) as the surfactant was prepared. The tape test indicated that the composite film had a steady adhesion on the surface of glass. At the same time, the water contact angle of the films was blow 5° after exposed to the UV light. Furthermore, the glass insulators with TiO2/SiO2 composite film were placed in the outdoor environment, and it showed self-cleaning ability after water drenching. It was proved from the experiments that the transparent TiO2/SiO2 hybrid films with self-cleaning property possessed potential application in the fields of outdoor glass constructions, suspended glass disk insulators and auto windshields.

  16. Fabrication and super-hydrophilic property of transparent TiO2/SiO2 film from sol-gel process

    NASA Astrophysics Data System (ADS)

    Zhang, Rui; Zhang, Yihe; Xu, Caiyun; Yu, Li; Lv, Fengzhu

    2012-04-01

    A series of transparent and super-hydrophilic TiO2/SiO2 composite films with high adhesion to the glass were fabricated by dipping methods. The sol was prepared using peroxotitanium complex (PTC) as precursor by sol-gel process at low temperature. The properties of transmittance, hydrophility and adhesion were characterized by ultraviolet-visible spectrophotometer, water contact angle and the tape test, and the structure was analyzed by Fourier transform infrared spectroscopy (FTIR). The relationship of structure, surfactant and the compound action of TiO2/SiO2 was investigated. The results indicated that the fabricated films achieved excellent transmittance to slide glass of over 90%. Because of the poor adhesion of pure TiO2 film, the TiO2/SiO2 composite film with polyvinyl alcohol (PVA) as the surfactant was prepared. The tape test indicated that the composite film had a steady adhesion on the surface of glass. At the same time, the water contact angle of the films was blow 5° after exposed to the UV light. Furthermore, the glass insulators with TiO2/SiO2 composite film were placed in the outdoor environment, and it showed self-cleaning ability after water drenching. It was proved from the experiments that the transparent TiO2/SiO2 hybrid films with self-cleaning property possessed potential application in the fields of outdoor glass constructions, suspended glass disk insulators and auto windshields.

  17. Optical, electrical and dielectric properties of TiO 2-SiO 2 films prepared by a cost effective sol-gel process

    NASA Astrophysics Data System (ADS)

    Vishwas, M.; Rao, K. Narasimha; Gowda, K. V. Arjuna; Chakradhar, R. P. S.

    2011-12-01

    Titanium dioxide (TiO 2) and silicon dioxide (SiO 2) thin films and their mixed films were synthesized by the sol-gel spin coating method using titanium tetra isopropoxide (TTIP) and tetra ethyl ortho silicate (TEOS) as the precursor materials for TiO 2 and SiO 2 respectively. The pure and composite films of TiO 2 and SiO 2 were deposited on glass and silicon substrates. The optical properties were studied for different compositions of TiO 2 and SiO 2 sols and the refractive index and optical band gap energies were estimated. MOS capacitors were fabricated using TiO 2 films on p-silicon (1 0 0) substrates. The current-voltage ( I- V) and capacitance-voltage ( C- V) characteristics were studied and the electrical resistivity and dielectric constant were estimated for the films annealed at 200 °C for their possible use in optoelectronic applications.

  18. Optical, electrical and dielectric properties of TiO2-SiO2 films prepared by a cost effective sol-gel process.

    PubMed

    Vishwas, M; Rao, K Narasimha; Gowda, K V Arjuna; Chakradhar, R P S

    2011-12-01

    Titanium dioxide (TiO(2)) and silicon dioxide (SiO(2)) thin films and their mixed films were synthesized by the sol-gel spin coating method using titanium tetra isopropoxide (TTIP) and tetra ethyl ortho silicate (TEOS) as the precursor materials for TiO(2) and SiO(2) respectively. The pure and composite films of TiO(2) and SiO(2) were deposited on glass and silicon substrates. The optical properties were studied for different compositions of TiO(2) and SiO(2) sols and the refractive index and optical band gap energies were estimated. MOS capacitors were fabricated using TiO(2) films on p-silicon (100) substrates. The current-voltage (I-V) and capacitance-voltage (C-V) characteristics were studied and the electrical resistivity and dielectric constant were estimated for the films annealed at 200°C for their possible use in optoelectronic applications. PMID:21924670

  19. Preparation of MgF2-SiO2 thin films with a low refractive index by a solgel process.

    PubMed

    Ishizawa, Hitoshi; Niisaka, Shunsuke; Murata, Tsuyoshi; Tanaka, Akira

    2008-05-01

    Porous MgF(2)-SiO(2) thin films consisting of MgF(2) particles connected by an amorphous SiO(2) binder are prepared by a solgel process. The films have a low refractive index of 1.26, sufficient strength to withstand wiping by a cloth, and a high environmental resistance. The refractive index of the film can be controlled by changing the processing conditions. Films can be uniformly formed on curved substrates and at relatively low temperatures, such as 100 degrees C. The low refractive index of the film, which cannot be achieved by conventional dry processes, is effective in improving the performance of antireflective coatings. PMID:18449247

  20. Polymeric fibre optic sensor based on a SiO2 nanoparticle film for humidity sensing on wounds

    NASA Astrophysics Data System (ADS)

    Gomez, David; Morgan, Stephen P.; Hayes Gill, Barrie R.; Korposh, Serhiy

    2016-05-01

    Optical fibre sensors have the potential to be incorporated into wound dressings to monitor moisture and predict healing without the need to remove the dressing. A low cost polymeric optical fibre humidity sensor based on evanescent wave absorption is demonstrated for skin humidity measurement. The sensor is fabricated by coating the fibre with a hydrophilic film based on bilayers of Poly(allylamine hydrochloride) (PAH) and SiO2 mesoporous nanoparticles. The Layer-by-Layer method was used for the deposition of the layers. Multimode polymeric optical fibre with a cladding diameter of 250μm was covered by 7 layers of PAH/SiO2 film on the central region of an unclad fibre with a diameter of 190μm. The length of the sensitive region is 30mm. Experiment results show a decrease in light intensity when relative humidity increases due to refractive index changes of the fibre coating. The sensitivity obtained was 200mV/%RH and the sensor was demonstrated to provide a faster response to changes in the humidity of the skin microenvironment than a commercial sensor.

  1. A hybrid model for the charging process of the amorphous SiO2 film in radio frequency microelectromechanical system capacitive switches

    NASA Astrophysics Data System (ADS)

    Wang, Li-Feng; Huang, Qing-An; Tang, Jie-Ying; Liao, Xiao-Ping

    2011-03-01

    Charging is one of the most important reliability issues in radio frequency microelectro- mechanical systems (RF MEMS) capacitive switches since it makes the actuation voltage unstable. This paper proposes a hybrid model to describe the transient dielectric charging and discharging process in the defect-rich amorphous SiO2 RF MEMS capacitive switches and verifies experimentally. The hybrid model contains two parts according to two different charging mechanisms of the amorphous SiO2, which are the polarisation and charge injection. The models for polarisation and for charge injection are established, respectively. Analysis and experimental results show that polarisation is always effective, while the charge injection has a threshold electric field to the amorphous SiO2 film. Under different control voltage conditions, the hybrid model can accurately describe the experimental data. Project supported by the National Natural Science Foundation of China (Grant No. 60676043).

  2. Photosensitivity of 20GeO2 : 80SiO2 hydrogen-loaded and non-hydrogen-loaded thin films

    NASA Astrophysics Data System (ADS)

    Rajni; Pita, K.; Ho, Charles K. F.; Swee Chuan, Tjin; Hin, Kam Chan

    2006-06-01

    Photosensitive materials offer great potential for passive and active optical devices in communication, data manipulation and storage. We prepared photosensitive germanosilicate (20GeO2 : 80SiO2) inorganic thin films by the sol gel method. These films were annealed at various temperatures in the range of 700 900 °C. The films annealed at 900 °C were found to be fully densified and were porous when annealed below 900 °C. The UV KrF laser (248 nm) has been used to induce refractive index change (Δn). We have studied the Fourier transform infra-red (FTIR) spectroscopy and the refractive index changes of the hydrogen-loaded and as-deposited samples before and after UV illumination. For the porous samples, the -OH absorption band around 3400 cm-1 increases with hydrogen-loading and decreases with UV radiation. The hydrogen-loading has induced absorption around 500 600 cm-1 for all our samples (both porous and dense samples) and that indicates the formation of Si H bonds. The Si H absorption bands disappeared after UV illumination. We observed the high Δn of about 0.0094 for the as-deposited dense film annealed at 900 °C and value enhanced to 0.0096 after H2-loading. For our samples, the large induced refractive index change is explained in terms of the formation of the oxygen related defects upon UV exposure. This is related to the induced absorption band around 620 740 cm-1 in the FTIR spectra.

  3. Direct tunneling stress-induced leakage current in ultrathin HfO2/SiO2 gate dielectric stacks

    NASA Astrophysics Data System (ADS)

    Samanta, Piyas; Man, Tsz Yin; Zhang, Qingchun; Zhu, Chunxiang; Chan, Mansun

    2006-11-01

    The conduction mechanism(s) and behavior of direct tunneling stress-induced leakage current (SILC) through ultrathin hafnium oxide (HfO2)/silicon dioxide (SiO2) dual layer gate stack in metal-oxide-semiconductor (MOS) devices have been experimentally investigated in-depth. Both transient and steady-state SILCs have been studied after constant voltage stress (CVS) and constant current stress (CCS) in n-MOS capacitors with negative bias on the tantalum nitride (TaN) gate. The present report clearly indicates that the observed steady-state SILC is due to assisted tunneling via both monoenergetic trapped positive charges and neutral electron traps generated in the HfO2 layer during either CVS or CCS. SILC measured immediately after stress decays slowly due to tunnel detrapping of stress-induced trapped holes in the HfO2 layer. Furthermore, the mechanisms for stress-induced charge carrier generation/trapping and trap creation in the dielectric have been discussed. Our analysis also shows that CVS degrades the dielectric integrity more severely than CCS in the 4.2nm physically thick HfO2/SiO2 stack.

  4. Effect of N2 dielectric barrier discharge treatment on the composition of very thin SiO2-like films deposited from hexamethyldisiloxane at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Reuter, R.; Gherardi, N.; Benedikt, J.

    2012-11-01

    The continuous deposition of thin SiO2-like films by means of a dielectric barrier discharge with helium or nitrogen gas with small admixture of hexamethyldisiloxane (HMDSO) has been compared to a layer-by-layer deposition process, in which a very thin (0.7 nm and 2.5 nm) films are deposited from HMDSO precursor and treated afterwards by a pure N2 dielectric barrier discharge (DBD). Presented results clearly show that a carbon-free SiO2-like films can be obtained in the latter process, even if the continuous deposition led to carbon-rich material. Surface reactions of N2-DBD generated excited species (metastables, ions, or possibly photons) with surface bonded carbon are responsible for this effect. Moreover, OH-free and oxidation-resistant films can be produced even at the room substrate temperature.

  5. Purely electronic switching with high uniformity, resistance tunability, and good retention in Pt-dispersed SiO2 thin films for ReRAM.

    PubMed

    Choi, Byung Joon; Chen, Albert B K; Yang, Xiang; Chen, I-Wei

    2011-09-01

    Resistance switching memory operating by a purely electronic switching mechanism, which was first realized in Pt-dispersed SiO2 thin films, satisfies criteria including high uniformity, fast switching speed, and long retention for non-volatile memory application. This resistive element obeys Ohm's law for the area dependence, but its resistance exponentially increases with the film thickness, which provides new freedom to tailor the device characteristics. PMID:24737180

  6. SYNCHROTRON RADIATION, FREE ELECTRON LASER, APPLICATION OF NUCLEAR TECHNOLOGY, ETC.: Identification of pore size in porous SiO2 thin film by positron annihilation

    NASA Astrophysics Data System (ADS)

    Zhang, Zhe; Qin, Xiu-Bo; Wang, Dan-Ni; Yu, Run-Sheng; Wang, Qiao-Zhan; Ma, Yan-Yun; Wang, Bao-Yi

    2009-02-01

    Positron annihilation lifetime and Doppler broadening of annihilation line techniques have been used to obtain information about the small pore structure and size of porous SiO2 thin film produced by sputtered Al-Si thin film and etched Al-Si thin film. The film is prepared by an Al/Si 75:25 at.-% (Al75Si25) target with the radiofrequency (RF) power of 66 W at room temperature. A 5 wt.-% phosphoric acid solution is used to etch the Al cylinders. All the Al cylinders dissolved in the solution after 15 h at room temperature, and the sample is subsequently rinsed in pure water. In this way, the porous SiO2 on the Si substrate is produced. From our results, the values of all lifetime components in the spectra of Al-Si thin film are less than 1 ns, but the value of one of the lifetime components in the spectra of porous SiO2 thin film is τ = 7.80 ns. With these values of lifetime, RTE (Rectangular Pore Extension) model has been used to analyze the pore size.

  7. Thickness-dependent white electroluminescence from diamond/CeF3/SiO2 multilayered films

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoping; Liu, Ping; Wang, Lijun; Li, Jian

    2014-03-01

    Diamond/CeF3/SiO2 multilayered films electroluminescent (EL) devices were made, and we found that the EL spectrum at room temperature depends on the CeF3 layer thickness. The EL spectrum shows that the main peaks are located at 527 nm, 593 nm, and 742 nm when the CeF3 layer thickness is less than 0.5 μm, but when the CeF3 layer thickness is greater than 0.5 μm, the electroluminescence spectrum obviously exhibits three bands, which are centered at 310-380 nm (ultraviolet emission), 520-580 nm (green-yellow emission), and 700-735 nm (red emission). The white EL brightness of the device (for thicker CeF3 layer) reaches a maximum of 15 cd/m2 at a forward applied voltage of 225 V, which can be distinguished at the sunlight in the light by the naked eye.

  8. Film growth, adsorption and desorption kinetics of indigo on SiO2

    NASA Astrophysics Data System (ADS)

    Scherwitzl, Boris; Resel, Roland; Winkler, Adolf

    2014-05-01

    Organic dyes have recently been discovered as promising semiconducting materials, attributable to the formation of hydrogen bonds. In this work, the adsorption and desorption behavior, as well as thin film growth was studied in detail for indigo molecules on silicon dioxide with different substrate treatments. The material was evaporated onto the substrate by means of physical vapor deposition under ultra-high vacuum conditions and was subsequently studied by Thermal Desorption Spectroscopy (TDS), Auger Electron Spectroscopy, X-Ray Diffraction, and Atomic Force Microscopy. TDS revealed initially adsorbed molecules to be strongly bonded on a sputter cleaned surface. After further deposition a formation of dimers is suggested, which de-stabilizes the bonding mechanism to the substrate and leads to a weakly bonded adsorbate. The dimers are highly mobile on the surface until they get incorporated into energetically favourable three-dimensional islands in a dewetting process. The stronger bonding of molecules within those islands could be shown by a higher desorption temperature. On a carbon contaminated surface no strongly bonded molecules appeared initially, weakly bonded monomers rather rearrange into islands at a surface coverage that is equivalent to one third of a monolayer of flat-lying molecules. The sticking coefficient was found to be unity on both substrates. The desorption energies from carbon covered silicon dioxide calculated to 1.67 ± 0.05 eV for multilayer desorption from the islands and 0.84 ± 0.05 eV for monolayer desorption. Corresponding values for desorption from a sputter cleaned surface are 1.53 ± 0.05 eV for multilayer and 0.83 ± 0.05 eV for monolayer desorption.

  9. Film growth, adsorption and desorption kinetics of indigo on SiO2

    PubMed Central

    Scherwitzl, Boris; Resel, Roland; Winkler, Adolf

    2015-01-01

    Organic dyes have recently been discovered as promising semiconducting materials, attributable to the formation of hydrogen bonds. In this work, the adsorption and desorption behavior, as well as thin film growth was studied in detail for indigo molecules on silicon dioxide with different substrate treatments. The material was evaporated onto the substrate by means of physical vapor deposition under ultra-high vacuum conditions and was subsequently studied by Thermal Desorption Spectroscopy (TDS), Auger Electron Spectroscopy, X-Ray Diffraction, and Atomic Force Microscopy. TDS revealed initially adsorbed molecules to be strongly bonded on a sputter cleaned surface. After further deposition a formation of dimers is suggested, which de-stabilizes the bonding mechanism to the substrate and leads to a weakly bonded adsorbate. The dimers are highly mobile on the surface until they get incorporated into energetically favourable three-dimensional islands in a dewetting process. The stronger bonding of molecules within those islands could be shown by a higher desorption temperature. On a carbon contaminated surface no strongly bonded molecules appeared initially, weakly bonded monomers rather rearrange into islands at a surface coverage that is equivalent to one third of a monolayer of flat-lying molecules. The sticking coefficient was found to be unity on both substrates. The desorption energies from carbon covered silicon dioxide calculated to 1.67 ± 0.05 eV for multilayer desorption from the islands and 0.84 ± 0.05 eV for monolayer des orption. Corresponding values for desorption from a sputter cleaned surface are 1.53 ± 0.05 eV for multilayer and 0.83 ± 0.05 eV for monolayer desorption. PMID:24832297

  10. Phonon induced luminescence decay in monolayer MoS2 on SiO2/Si substrates

    NASA Astrophysics Data System (ADS)

    Saigal, Nihit; Ghosh, Sandip

    2015-12-01

    Exfoliated monolayer MoS2 films on SiO2/Si substrates have been studied using photoluminescence (PL), Raman and reflectance contrast (RC) spectroscopies. With increase in temperature, the intensity of the two dominant PL spectral features A and D, attributed to A exciton/trion and to defects, seemingly decay in an activated fashion with an energy ˜ 50 meV , which is close to the energies of E2 g 1 and A1g phonons. Comparison of absorption spectrum derived from RC with circular polarization resolved PL spectrum suggests that both D and A emissions are associated with bound excitons, the A emission involving relatively weakly localized ones. The PL decay behaviour is explained using a phenomenological model where non-radiative loss of excitons is determined by the number of excited phonon modes. This corroborates the recent finding of strong A exciton and A1g phonon coupling in monolayer MoS2.

  11. Adsorption and self-assembly of M13 phage into directionally organized structures on C and SiO2 films.

    PubMed

    Moghimian, Pouya; Srot, Vesna; Rothenstein, Dirk; Facey, Sandra J; Harnau, Ludger; Hauer, Bernhard; Bill, Joachim; van Aken, Peter A

    2014-09-30

    A versatile method for the directional assembly of M13 phage using amorphous carbon and SiO2 thin films was demonstrated. A high affinity of the M13 phage macromolecules for incorporation into aligned structures on an amorphous carbon surface was observed at the concentration range, in which the viral nanofibers tend to disorder. In contrast, the viral particles showed less freedom to adopt an aligned orientation on SiO2 films when deposited in close vicinity. Here an interpretation of the role of the carbon surface in significant enhancement of adsorption and generation of viral arrays with a high orientational order was proposed in terms of surface chemistry and competitive electrostatic interactions. This study suggests the use of amorphous carbon substrates as a template for directional organization of a closely-packed and two-dimensional M13 viral film, which can be a promising route to mineralize a variety of smooth and homogeneous inorganic nanostructure layers. PMID:25195499

  12. SiO2 nanoparticle-induced impairment of mitochondrial energy metabolism in hepatocytes directly and through a Kupffer cell-mediated pathway in vitro

    PubMed Central

    Xue, Yang; Chen, Qingqing; Ding, Tingting; Sun, Jiao

    2014-01-01

    The liver has been shown to be a primary target organ for SiO2 nanoparticles in vivo, and may be highly susceptible to damage by these nanoparticles. However, until now, research focusing on the potential toxic effects of SiO2 nanoparticles on mitochondria-associated energy metabolism in hepatocytes has been lacking. In this work, SiO2 nanoparticles 20 nm in diameter were evaluated for their ability to induce dysfunction of mitochondrial energy metabolism. First, a buffalo rat liver (BRL) cell line was directly exposed to SiO2 nanoparticles, which induced cytotoxicity and mitochondrial damage accompanied by decreases in mitochondrial dehydrogenase activity, mitochondrial membrane potential, enzymatic expression in the Krebs cycle, and activity of the mitochondrial respiratory chain complexes I, III and IV. Second, the role of rat-derived Kupffer cells was evaluated. The supernatants from Kupffer cells treated with SiO2 nanoparticles were transferred to stimulate BRL cells. We observed that SiO2 nanoparticles had the ability to activate Kupffer cells, leading to release of tumor necrosis factor-α, nitric oxide, and reactive oxygen species from these cells and subsequently to inhibition of mitochondrial respiratory chain complex I activity in BRL cells. PMID:24959077

  13. Ion-irradiation-induced amorphization of Cu nanoparticles embedded in SiO2

    NASA Astrophysics Data System (ADS)

    Johannessen, B.; Kluth, P.; Llewellyn, D. J.; Foran, G. J.; Cookson, D. J.; Ridgway, M. C.

    2007-11-01

    Elemental Cu nanoparticles embedded in SiO2 were irradiated with 5MeVSn3+ . The nanoparticle structure was studied as a function of Sn3+ fluence by extended x-ray absorption fine structure spectroscopy, small-angle x-ray scattering, and transmission electron microscopy. Prior to irradiation, Cu nanoparticles exhibited the face-centered-cubic structure. Upon irradiation at intermediate fluences ( 1×1013 to 1×1014ions/cm2 ), the first nearest neighbor Cu-Cu coordination number decreased, while the Debye-Waller factor, bondlength, and third cumulant of the bondlength distribution increased. In particular, at a fluence of 1×1014ions/cm2 we argue for the presence of an amorphous Cu phase, for which we deduce the structural parameters. Low temperature annealing (insufficient for nanoparticle growth) of the amorphous Cu returned the nanoparticles to the initial preirradiation structure. At significantly higher irradiation fluences ( 1×1015 to 1×1016ions/cm2 ), the nanoparticles were dissolved in the matrix with a Cu coordination similar to that of Cu2O .

  14. Enhanced high-frequency electromagnetic properties of FeCoB-SiO2/SiO2 multilayered granular films

    NASA Astrophysics Data System (ADS)

    Yang, F. F.; Yan, S. S.; Yu, M. X.; Kang, S. S.; Chen, Y. X.; Sun, J. S.; Xu, Q. T.; Bai, H. L.; Xu, T. S.; Li, Q.; Pan, S. B.; Liu, G. L.; Mei, L. M.

    2012-04-01

    A series of FeCoB-SiO2/SiO2 multilayered granular films with various thickness were prepared by alternating co-sputtering FeCoB and SiO2 targets and single-sputtering SiO2 target. As-deposited films were annealed in a magnetic field at different temperature. The high-frequency magnetic and electrical transport properties were investigated. The films annealed above 250 °C show good soft magnetic properties and obvious uniaxial magnetic anisotropy. The resistivity (ρ), coercivity (Hce) decrease and complex permeability (μ˜), ferromagnetic resonance frequency (fr) increase with increasing annealing temperature and thickness. The desirable high ρ (∼5.92 mΩ cm), considerable frequency linewidth (Δf∼4.02 GHz) and high μ˜ (μ‧=120 at low frequency, μmax″=80) were obtained for the 252 nm films annealed at 250 °C. The amorphous or nanograin phase and strong exchange coupling effect are responsible for the good high-frequency magnetic performance. The electrical transport properties show the films with high ρ and large μ˜ are near the conductive percolation threshold. Moreover, the Δf, damp coefficient (α) and Gilbert damping parameter (G) were discussed based on phenomenological Landau-Lifshitz-Gilbert equation.

  15. Sensitive elements of vacuum sensors based on porous nanostructured SiO2-SnO2 sol-gel films

    NASA Astrophysics Data System (ADS)

    Averin, I. A.; Igoshina, S. E.; Moshnikov, V. A.; Karmanov, A. A.; Pronin, I. A.; Terukov, E. I.

    2015-06-01

    The objects of investigation are porous nanostructured SiO2-SnO2 sol-gel films used as sensitive elements on vacuum sensors. The properties of the films with spherical, labyrinth, and percolation mesh structures are analyzed. It is shown that the resistance of sensitive elements based on these films sharply drops at a pressure below the atmospheric value. Processes taking place in the films at subatmospheric pressures are studied. It is found that the desorption of water vapor increases the resistance of the sensitive elements of vacuum sensors, whereas the desorption of carbon dioxide and oxygen decreases the resistance. This agrees with experimental data.

  16. SiO2 doped Ge2Sb2Te5 thin films with high thermal efficiency for applications in phase change random access memory.

    PubMed

    Ryu, Seung Wook; Lyeo, Ho-Ki; Lee, Jong Ho; Ahn, Young Bae; Kim, Gun Hwan; Kim, Choon Hwan; Kim, Soo Gil; Lee, Se-Ho; Kim, Ka Young; Kim, Jong Hyeop; Kim, Won; Hwang, Cheol Seong; Kim, Hyeong Joon

    2011-06-24

    This study examined the various physical, structural and electrical properties of SiO(2) doped Ge(2)Sb(2)Te(5) (SGST) films for phase change random access memory applications. Interestingly, SGST had a layered structure (LS) resulting from the inhomogeneous distribution of SiO(2) after annealing. The physical parameters able to affect the reset current of phase change memory (I(res)) were predicted from the Joule heating and heat conservation equations. When SiO(2) was doped into GST, thermal conductivity largely decreased by ∼ 55%. The influence of SiO(2)-doping on I(res) was examined using the test phase change memory cell. I(res) was reduced by ∼ 45%. An electro-thermal simulation showed that the reduced thermal conductivity contributes to the improvement of cell efficiency as well as the reduction of I(res), while the increased dynamic resistance contributes only to the latter. The formation and presence of the LS thermal conductivity in the set state test cell after repeated switching was confirmed. PMID:21572208

  17. Effects of Defects in SiO2 Thin Films Prepared on Polyethylene Terephthalate by High-Temperature E-beam Deposition

    NASA Astrophysics Data System (ADS)

    Han, Jin‑Woo; Kang, Hee‑Jin; Kim, Jong‑Hwan; Seo, Dae‑Shik

    2006-08-01

    In this study, we characterized silicon oxide (SiO2) thin film prepared on polyethylene terephthalate (PET) substrates by electron-beam (e-beam) deposition for transparent barrier application. As the chamber temperature is increased from 30 to 110 °C, the roughness increases while water vapor transmission rate (WVTR) decreases. Under these conditions, WVTR of PET can be reduced from a level of 0.57 g/m2/day (bare subtrate) to 0.05 g/m2/day after application of a 200-nm-thick SiO2 coating at 110 °C. A more efficient way to improve permeation of PET was carried out by using a double sided coating of a 5-μm-thick parylene film. It was found that WVTR for PET substrates can be reduced to a level of -0.2 g/m2/day. The double-sided parylene coating on PET could contribute in lowering the stress of oxide film, which greatly improves the WVTR data. These results indicate that the SiO2/parylene/PET barrier coatings have a high potential for flexible organic light-emitting diode (OLED) applications.

  18. XPS study of the Al/SiO2 interface viewed from the SiO2 side

    NASA Technical Reports Server (NTRS)

    Hecht, M. H.; Grunthaner, F. J.; Maserjian, J.

    1984-01-01

    The first nondestructive measurement of the chemical and physical characteristics of the interface between bulk SiO2 and thick aluminum films is presented. Both X-ray photoelectron spectroscopy (XPS) and electrical measurements of unannealed resistively evaporated Al films on thermal SiO2 indicate an atomically abrupt interface. Postmetallization annealing (PMA) at 450 C induces reduction of the SiO2 by the aluminum, resulting in the layer ordering SiO2/Al2O3/Si/Al. The XPS measurement is performed from the SiO2 side after removal of the Si substrate after etching with XeF2 gas and thinning of the SiO2 layer with HF:ETOH. This represents a powerful new approach to the study of metal-insulator and other interfaces.

  19. The enhanced photocatalytic activity and self-cleaning properties of mesoporous SiO2 coated Cu-Bi2O3 thin films.

    PubMed

    Shan, Wenjie; Hu, Yun; Zheng, Mengmeng; Wei, Chaohai

    2015-04-28

    Mesoporous SiO2 coated Cu-Bi2O3 thin films (meso-SiO2/Cu-Bi2O3) were prepared on glass substrates using a simple sol-gel/spin-coating method. The structure and optical properties were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, a UV-vis spectrophotometer and a water contact angle meter. The photocatalytic activity and self-cleaning properties of the films were investigated through the degradation of methyl orange and stearic acid, respectively. It was found that the meso-SiO2/Cu-Bi2O3 thin films were highly transparent and showed excellent superhydrophilicity even in the dark. The thin films exhibited enhanced photocatalytic activity and self-cleaning properties compared to pure Bi2O3 films, which was attributed to the cooperation of the interfacial charge transfer between Bi2O3 and surface Cu species as well as the unique mesoporous SiO2 structure. The results showed that the films can be used as promising self-cleaning and antifogging materials. PMID:25801807

  20. Switchable and tunable film bulk acoustic resonator fabricated using barium strontium titanate active layer and Ta2O5/SiO2 acoustic reflector

    NASA Astrophysics Data System (ADS)

    Sbrockey, N. M.; Kalkur, T. S.; Mansour, A.; Khassaf, H.; Yu, H.; Aindow, M.; Alpay, S. P.; Tompa, G. S.

    2016-08-01

    A solidly mounted acoustic resonator was fabricated using a Ba0.60Sr0.40TiO3 (BST) film deposited by metal organic chemical vapor deposition. The device was acoustically isolated from the substrate using a Bragg reflector consisting of three pairs of Ta2O5/SiO2 layers deposited by chemical solution deposition. Transmission electron microscopy verified that the Bragg reflector was not affected by the high temperatures and oxidizing conditions necessary to process high quality BST films. Electrical characterization of the resonator demonstrated a quality factor (Q) of 320 and an electromechanical coupling coefficient (Kt2) of 7.0% at 11 V.

  1. The structural studies of Ag containing TiO2-SiO2 gels and thin films deposited on steel

    NASA Astrophysics Data System (ADS)

    Adamczyk, Anna; Rokita, Magdalena

    2016-06-01

    FTIR spectroscopic structural studies of titania-silica monolith samples as well as thin films deposited on steel were described in this work. Thin films were synthesized by the sol-gel method applying the dip coating as separate one-component TiO2 and/or SiO2 layers or as two-component TiO2-SiO2 thin films. Silver nanoparticles were incorporated into the structure from pure SiO2 sol, deposited then as an additional layer in those hybrid multilayers systems. Except the spectroscopic studies, XRD diffraction, SEM microscopy with EDX analysis and AFM microscopy were applied. The structural studies allow to describe and compare the structure and the morphology of thin films, as well those Ag free as Ag containing ones, also by the comparison with the structure of bulk samples. In FTIR spectra, the band observed at about 613 cm-1 can be connected with the presence of the non-tetrahedral cation in the structure and is observed only in the spectra of Ag containing bulk samples and thin films. The bands at 435-467 cm-1 are due to the stretching vibrations of Ti-O bonds or as well to the bending vibrations of O-Si-O one. In the ranges of 779-799 cm-1 and 1027-1098 cm-1, the bands ascribed to the symmetric stretching vibrations and asymmetric vibrations of Si-O-Si connections, respectively, are observed. SEM and AFM images gave the information on the microstructure and the topography of samples surface. XRD measurements confirmed the presence of only amorphous phase in samples up to 500 °C and allowed to observe the tendency of their crystallization.

  2. SiO2/TiO2/n-Si/Ag(Cr)/TiO2 thin films with superhydrophilicity and low-emissivity

    NASA Astrophysics Data System (ADS)

    Loka, Chadrasekhar; Ryeol Park, Kyoung; Lee, Kee-Sun

    2016-01-01

    In this study, SiO2/TiO2/n-Si/Ag(Cr)/TiO2 multilayer structures have been designed and deposited by the RF and DC magnetron sputtering at room temperature. The as-deposited TiO2/glass films which are initially amorphous in nature were subjected to post annealing at 673 K for anatase phase TiO2. The anatase TiO2 films showed an optical bandgap ˜3.32 eV. The Ag(Cr)/TiO2 showed very low-emissivity (low-e) value ˜0.081 which is evaluated by using the sheet resistance (6.51 Ω/□) of the films. All the deposited films showed high visible transmittance (˜81%) and high infrared reflectance (72%) which are recorded by using the UV-vis-NIR spectrophotometer. In addition, experimentally obtained optical properties were in good agreement with the simulation data. The TiO2/n-Si heterojunction concept has been employed to enhance the superhydrophilicity of the deposited multilayer stack, TiO2/n-Si/Ag(Cr)/TiO2 films exhibited best superhydrophilicity with water contact angle ˜2°. The deposited multilayer structures SiO2/TiO2/n-Si/Ag(Cr)/TiO2 and TiO2/n-Si/Ag(Cr)/TiO2 achieved significant low-e and superhydrophilicity.

  3. Implantation of plasmonic nanoparticles in SiO2 by pulsed laser irradiation of gold films on SiOx-coated fused silica and subsequent thermal annealing

    NASA Astrophysics Data System (ADS)

    Stolzenburg, H.; Peretzki, P.; Wang, N.; Seibt, M.; Ihlemann, J.

    2016-06-01

    The pulsed UV-laser irradiation of thin noble metal films deposited on glass substrates leads to the incorporation of metal particles in the glass, if a sufficiently high laser fluence is applied. This process is called laser implantation. For the implantation of gold into pure fused silica, high laser fluences (∼1 J/cm2 at 193 nm laser wavelength) are required. Using a SiOx (x ≈ 1) coated SiO2-substrate, the implantation of gold into this coating can be accomplished at significantly lower fluences starting from 0.2 J/cm2 (comparable to those used for standard glass). Particles with diameters in the range of 10-60 nm are implanted to a depth of about 40 nm as identified by transmission electron microscopy. An additional high temperature annealing step in air leads to the oxidation of SiOx to SiO2, without influencing the depth distribution of particles significantly. Only superficial, weakly bound particles are released and can be wiped away. Absorption spectra show a characteristic plasmon resonance peak at 540 nm. Thus, pure silica glass (SiO2) with near surface incorporated plasmonic particles can be fabricated with this method. Such material systems may be useful for example as robust substrates for surface enhanced Raman spectroscopy (SERS).

  4. Chemical reactions during plasma-enhanced atomic layer deposition of SiO2 films employing aminosilane and O2/Ar plasma at 50 °C

    NASA Astrophysics Data System (ADS)

    Lu, Yi; Kobayashi, Akiko; Kondo, Hiroki; Ishikawa, Kenji; Sekine, Makoto; Hori, Masaru

    2014-01-01

    We report the temporal evolution of surface species observed in situ using attenuated total reflection Fourier transform infrared absorption spectroscopy (ATR-FTIR) during plasma-enhanced atomic layer deposition (PE-ALD) of SiO2 films employing aminosilane and an O2/Ar plasma at a temperature of 50 °C. Reversals in the appearance of IR absorbance features associated with SiO-H, C-Hx, and Si-H proved to coincide with the self-limiting reaction property in ALD. Our IR results indicate that an O2/Ar plasma can both removed CHx groups and transform SiH surface species to SiOH. In addition, SiO2 deposition was confirmed by a continuous increase in Si-O absorbance with each PE-ALD step, which becomes stable after several cycles. On the basis of our results, the mechanism of low temperature SiO2 PE-ALD was discussed.

  5. High energy ion irradiation induced surface patterning on a SiO2 glass substrate

    NASA Astrophysics Data System (ADS)

    Srivastava, S. K.; Ganesan, K.; Gangopadhyay, P.; Panigrahi, B. K.; Nair, K. G. M.; Tyagi, A. K.

    2014-11-01

    Experimental results about formation of self-organized surface patterns on a silica glass substrate due to irradiations with high energy Au ions at various angles of incidences have been reported in this paper. Pattern formations are found to vary significantly from theoretical predictions. Orientation, growth of ripples and ripple characteristics observed here do not conform to established results of low energy heavy-ion irradiation studies. High energy Au ion-induced effects (e.g., surface stress, mass redistribution and surface current) have been suitably invoked to explain observed phenomena.

  6. Microstructure and optical dispersion characterization of nanocomposite sol-gel TiO2-SiO2 thin films with different compositions

    NASA Astrophysics Data System (ADS)

    Kermadi, S.; Agoudjil, N.; Sali, S.; Zougar, L.; Boumaour, M.; Broch, L.; En Naciri, A.; Placido, F.

    2015-06-01

    Nanocomposite TiO2-SiO2 thin films with different compositions (from 0 to 100 mol% TiO2) were deposited by sol-gel dip-coating method on silicon substrate. Crystal structure, chemical bonding configuration, composition and morphology evolutions with composition were followed by Raman scattering, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy and scanning electron microscopy respectively. The refractive index and the extinction coefficient were derived in a broad band wavelength (250-900 nm) from spectroscopic ellipsometry data with high accuracy and correlated with composition and microstructure. Results showed an anatase structure for 100% TiO2 with a grain size in 6-10 nm range. Whereas, the inclusion of SiO2 enlarges the optical band gap and suppresses the grain growth up to 4 nm in size. High TiO2 dispersion in SiO2 matrix was observed for all mixed materials. The refractive index (at λ = 600 nm) increases linearly with composition from 1.48 (in 100% SiO2) to 2.22 (in 100% TiO2) leading to lower dense material, its dispersion being discussed in terms of the Wemple-DiDomenico single oscillator model. Hence, the optical parameters, such optical dispersion energies E0 and Ed, the average oscillators, strength S0 and wavelength λ0 and the ratio of the carrier concentration to the effective mass N/m∗ have been derived. The analysis revealed a strong dependence on composition and structure. The optical response was also investigated in term of complex optical conductivity (σ) and both volume and surface energy loss functions (VELF and SELF).

  7. Study on external electric field-induced structural changes in the initial growth of pentacene on amorphous SiO2

    NASA Astrophysics Data System (ADS)

    Zeng, Yuanqi; Tao, Bo; Chen, Jiankui; Yin, Zhouping

    2016-05-01

    External electric field-induced structural changes in the initial growth processes of pentacene on a sylanol-saturated amorphous SiO2 surface have been investigated using molecular dynamics simulations. A series of electric fields with different directions and strengths are applied to the initial lateral-orientated pentacene cluster. After that different molecular orientations are observed, which obviously present the regulatory effects of an electric field on the molecular orientation. When the electric field perpendicular to the molecular plane is applied to the pentacene cluster, the pentacene molecules keep the lying-down conformation regardless of changes in the electric field strength. Contrary to that, under the electric field parallel to the pentacene long axes or short axes with proper strength, the pentacene cluster undergoes a conformational transition from a lying-down conformation to a standing-up one. The results of this work may enrich the information on the electric field-induced orientation controllable fabrication approaches of organic semiconductor thin films.

  8. Detection of short range order in SiO2 thin-films by grazing-incidence wide and small-angle X-ray scattering

    NASA Astrophysics Data System (ADS)

    Nagata, Kohki; Ogura, Atsushi; Hirosawa, Ichiro; Suwa, Tomoyuki; Teramoto, Akinobu; Ohmi, Tadahiro

    2016-04-01

    The effects of the fabrication process conditions on the microstructure of silicon dioxide thin films of <10 nm thickness are presented. The microstructure was investigated using grazing-incidence wide and small-angle X-ray scattering methods with synchrotron radiation. The combination of a high brilliance light source and grazing incident configuration enabled the observation of very weak diffuse X-ray scattering from SiO2 thin films. The results revealed different microstructures, which were dependent on oxidizing species or temperature. The micro-level properties differed from bulk properties reported in the previous literature. It was indicated that these differences originate from inner stress. The detailed structure in an amorphous thin film was not revealed owing to detection difficulties.

  9. Room-temperature NH3 gas sensors based on Ag-doped γ-Fe2O3/SiO2 composite films with sub-ppm detection ability.

    PubMed

    Tang, Yongliang; Li, Zhijie; Zu, Xiaotao; Ma, Jinyi; Wang, Lu; Yang, Jing; Du, Bo; Yu, Qingkai

    2015-11-15

    In this report, NH3 gas sensors based on Ag-doped γ-Fe2O3/SiO2 composite films are investigated. The composite films were prepared with a sol-gel process, and the films' electrical resistance responded to the change of NH3 concentration in the environment. The SEM and AFM investigations showed that the films had a porous structure, and the XRD investigation indicated that the size of Ag particles changed with the modification of Ag loading content. Through a comparative gas sensing study among the Ag-doped composite films, undoped composite film, γ-Fe2O3 film, and SiO2 film, the Ag-doped composite films were found to be much more sensitive than the sensors based on the undoped composite film and γ-Fe2O3 film at room temperature, indicating the significant influences of the SiO2 and Ag on the sensing property. Moreover, the sensor based on Ag-doped (4%) γ-Fe2O3/SiO2 composite film was able to detect the NH3 gas at ppb level. Conversely, the responses of the sensor to other test gases (C2H5OH, CO, H2, CH4 and H2S) were all markedly low, suggesting excellent selectivity. PMID:26057440

  10. Comparative analysis of breakdown mechanism in thin SiO2 oxide films in metal-oxide-semiconductor structures under the action of heavy charged particles and a pulsed voltage

    NASA Astrophysics Data System (ADS)

    Zinchenko, V. F.; Lavrent'ev, K. V.; Emel'yanov, V. V.; Vatuev, A. S.

    2016-02-01

    Regularities in the breakdown of thin SiO2 oxide films in metal-oxide-semiconductors structures of power field-effect transistors under the action of single heavy charged particles and a pulsed voltage are studied experimentally. Using a phenomenological approach, we carry out comparative analysis of physical mechanisms and energy criteria of the SiO2 breakdown in extreme conditions of excitation of the electron subsystem in the subpicosecond time range.

  11. Optimization of a Solution-Processed SiO2 Gate Insulator by Plasma Treatment for Zinc Oxide Thin Film Transistors.

    PubMed

    Jeong, Yesul; Pearson, Christopher; Kim, Hyun-Gwan; Park, Man-Young; Kim, Hongdoo; Do, Lee-Mi; Petty, Michael C

    2016-01-27

    We report on the optimization of the plasma treatment conditions for a solution-processed silicon dioxide gate insulator for application in zinc oxide thin film transistors (TFTs). The SiO2 layer was formed by spin coating a perhydropolysilazane (PHPS) precursor. This thin film was subsequently thermally annealed, followed by exposure to an oxygen plasma, to form an insulating (leakage current density of ∼10(-7) A/cm(2)) SiO2 layer. Optimized ZnO TFTs (40 W plasma treatment of the gate insulator for 10 s) possessed a carrier mobility of 3.2 cm(2)/(V s), an on/off ratio of ∼10(7), a threshold voltage of -1.3 V, and a subthreshold swing of 0.2 V/decade. In addition, long-term exposure (150 min) of the pre-annealed PHPS to the oxygen plasma enabled the maximum processing temperature to be reduced from 180 to 150 °C. The resulting ZnO TFT exhibited a carrier mobility of 1.3 cm(2)/(V s) and on/off ratio of ∼10(7). PMID:26704352

  12. High quality SiO2/Si interfaces of poly-crystalline silicon thin film transistors by annealing in wet atmosphere

    NASA Astrophysics Data System (ADS)

    Sano, Naoki; Sekiya, Mitsunobu; Hara, Masaki; Kohno, Atsushi; Sameshima, Toshiyuki

    1995-05-01

    A new post-metallization annealing technique was developed to improve the quality of metal-oxide-semiconductor (MOS) devices using SiO2 films formed by a parallel-plate remote plasma chemical vapor deposition as gate insulators. The quality of the interface between SiO2 and crystalline Si was investigated by capacitance-voltage (C-V) measurements. An H2O vapor annealing at 270 C for 30 min efficiently decreased the interface trap density to 2.0 x 10(exp 10) cm(exp -2) eV(exp -1), and the effective oxide charge density from 1 x 10(exp 12) to 5 x 10(exp 9) cm(exp -2). This annealing process was also applied to the fabrication of Al-gate polycrystalline silicon thin film transistors (poly-Si TFT's) at 270 C. In p-channel poly-Si TFT's, the carrier mobility increased from 60-400 cm(exp 2) V(exp -1) s(exp - 1) and the threshold voltage decreased from - 5.5 to - 1.7 V.

  13. Water adsorption, solvation and deliquescence of alkali halide thin films on SiO2 studied by ambient pressure X-ray photoelectron spectroscopy

    SciTech Connect

    Arima, Kenta; Jiang, Peng; Deng, Xingyi; Bluhm, Henrik; Salmeron, Miquel

    2010-03-31

    The adsorption of water on KBr thin films evaporated onto SiO2 was investigated as a function of relative humidity (RH) by ambient pressure X-ray photoelectron spectroscopy. At 30percent RH adsorbed water reaches a coverage of approximately one monolayer. As the humidity continues to increase, the coverage of water remains constant or increases very slowly until 60percent RH, followed by a rapid increase up to 100percent RH. At low RH a significant number of the Br atoms are lost due to irradiation damage. With increasing humidity solvation increases ion mobility and gives rise to a partial recovery of the Br/K ratio. Above 60percent RH the increase of the Br/K ratio accelerates. Above the deliquescence point (85percent RH), the thickness of the water layer continues to increase and reaches more than three layers near saturation. The enhancement of the Br/K ratio at this stage is roughly a factor 2.3 on a 0.5 nm KBr film, indicating a strong preferential segregation of Br ions to the surface of the thin saline solution on SiO2.

  14. Dewetting behavior of electron-beam-deposited Au thin films on various substrates: graphenes, quartz, and SiO2 wafers

    NASA Astrophysics Data System (ADS)

    Lee, Seung-Hwan; Kwak, Eun-Hye; Jeong, Goo-Hwan

    2015-02-01

    We demonstrate the dewetting behavior of Au thin films on the following substrates: single- and multilayer mechanically exfoliated graphene, and SiO2 and ST-cut quartz wafers. The 1-nm-thick Au thin films were prepared by electron beam deposition. The mean sizes of the Au nanoparticles from as-deposited samples were 0.4, 0.9, 1.6, and 2.3 nm and increased after a 60-min annealing at 900 °C to 5.1, 6.4, 9.4, and 10.8 nm for SiO2, ST-cut quartz, mono- and bi-layer graphene, respectively. Conversely, the areal densities of the Au nanoparticles decreased in all substrates with increasing annealing time. The different sizes, areal densities, and morphological evolutions of the Au nanoparticles due to annealing on the different substrates imply different interfacial interactions between Au and each surface. In addition, it is worth noting that single-walled carbon nanotubes (SWNTs) can be grown using the dewetted Au nanoparticles on graphene-coated quartz substrates. Finally, the present work can contribute to not merely precise formation of Au nanoparticles via dewetting phenomenon but also surface modification of graphene and SWNT growth.

  15. Growth of residual stress-free ZnO films on SiO2/Si substrate at room temperature for MEMS devices

    NASA Astrophysics Data System (ADS)

    Singh, Jitendra; Ranwa, Sapana; Akhtar, Jamil; Kumar, Mahesh

    2015-06-01

    ZnO thick Stress relaxed films were deposited by reactive magnetron sputtering on 2"-wafer of SiO2/Si at room temperature. The residual stress of ZnO films was measured by measuring the curvature of wafer using laser scanning method and found in the range of 0.18 x 109 to 11.28 x 109 dyne/cm2 with compressive in nature. Sputter pressure changes the deposition rates, which strongly affects the residual stress and surface morphologies of ZnO films. The crystalline wurtzite structure of ZnO films were confirmed by X-ray diffraction and a shift in (0002) diffraction peak of ZnO towards lower 2θ angle was observed with increasing the compressive stress in the films. The band gap of ZnO films shows a red shift from ˜3.275 eV to ˜3.23 eV as compressive stress is increased, unlike the stress for III-nitride materials. A relationship between stress and band gap of ZnO was derived and proposed. The stress-free growth of piezoelectric films is very important for functional devices applications.

  16. XRD, ESCA and C- V investigations of Al 2O 3 SiO 2 composite thin films synthesized by high dose oxygen ion implantation

    NASA Astrophysics Data System (ADS)

    Dubey, S. K.; Yadav, A. D.

    1998-10-01

    High purity aluminium (99.999%) films were deposited onto cleaned silicon substrates. 30 keV 16O 2+ ions were implanted in Al-Si system with dose levels varying from 1 × 10 17 to 7 × 10 17 O 2+ cm -2. X-ray diffraction (XRD) studies reveal the formation of α-Al 2O 3 phase at all doses and γ-Al 2O 3 and SiO 2 phases only for high dose implants. ESCA studies for Al 2p 3/2 and Si 2p lines at various depths confirm the formation of Al 2O 3 at all doses and the gradual chemical transformation of the SiO x towards the stoichiometric composition of SiO 2 with implanted oxygen dose. The interface-state density of Al 2O 3·SiO 2-Si MOS device shows approximately U shape distribution with a discrete peak at <0.4 eV above the valence band edge.

  17. Comparison of Multilayer Dielectric Thin Films for Future Metal-Insulator-Metal Capacitors: Al2O3/HfO2/Al2O3 versus SiO2/HfO2/SiO2

    NASA Astrophysics Data System (ADS)

    Park, Sang-Uk; Kwon, Hyuk-Min; Han, In-Shik; Jung, Yi-Jung; Kwak, Ho-Young; Choi, Woon-Il; Ha, Man-Lyun; Lee, Ju-Il; Kang, Chang-Yong; Lee, Byoung-Hun; Jammy, Raj; Lee, Hi-Deok

    2011-10-01

    In this paper, two kinds of multilayered metal-insulator-metal (MIM) capacitors using Al2O3/HfO2/Al2O3 (AHA) and SiO2/HfO2/SiO2 (SHS) were fabricated and characterized for radio frequency (RF) and analog mixed signal (AMS) applications. The experimental results indicate that the AHA MIM capacitor (8.0 fF/µm2) is able to provide a higher capacitance density than the SHS MIM capacitor (5.1 fF/µm2), while maintaining a low leakage current of about 50 nA/cm2 at 1 V. The quadratic voltage coefficient of capacitance, α gradually decreases as a function of stress time under constant voltage stress (CVS). The parameter variation of SHS MIM capacitors is smaller than that of AHA MIM capacitors. The effects of CVS on voltage linearity and time-dependent dielectric breakdown (TDDB) characteristics were also investigated.

  18. Solution-Processed VO2-SiO2 Composite Films with Simultaneously Enhanced Luminous Transmittance, Solar Modulation Ability and Anti-Oxidation property

    NASA Astrophysics Data System (ADS)

    Zhao, Lili; Miao, Lei; Liu, Chengyan; Li, Chao; Asaka, Toru; Kang, Yipu; Iwamoto, Yuji; Tanemura, Sakae; Gu, Hui; Su, Huirong

    2014-11-01

    Recently, researchers spare no efforts to fabricate desirable vanadium dioxide (VO2) film which provides simultaneously high luminous transmittance and outstanding solar modulation ability, yet progress towards the optimization of one aspect always comes at the expense of the other. Our research devotes to finding a reproducible economic solution-processed strategy for fabricating VO2-SiO2 composite films, with the aim of boosting the performance of both aspects. Compare to VO2 film, an improvement of 18.9% (from 29.6% to 48.5%) in the luminous transmittance as well as an increase of 6.0% (from 9.7% to 15.7%) in solar modulation efficiency is achieved when the molar ratio of Si/V attains 0.8. Based on the effective medium theory, we simulate the optical spectra of the composite films and the best thermochromic property is obtained when the filling factor attains 0.5, which is consistent with the experimental results. Meanwhile, the improvement of chemical stability for the composite film against oxidation has been confirmed. Tungsten is introduced to reduce the phase transition temperature to the ambient temperature, while maintain the thermochromism required for application as smart window. Our research set forth a new avenue in promoting practical applications of VO2-based thermochromic fenestration.

  19. Solution-processed VO2-SiO2 composite films with simultaneously enhanced luminous transmittance, solar modulation ability and anti-oxidation property.

    PubMed

    Zhao, Lili; Miao, Lei; Liu, Chengyan; Li, Chao; Asaka, Toru; Kang, Yipu; Iwamoto, Yuji; Tanemura, Sakae; Gu, Hui; Su, Huirong

    2014-01-01

    Recently, researchers spare no efforts to fabricate desirable vanadium dioxide (VO2) film which provides simultaneously high luminous transmittance and outstanding solar modulation ability, yet progress towards the optimization of one aspect always comes at the expense of the other. Our research devotes to finding a reproducible economic solution-processed strategy for fabricating VO2-SiO2 composite films, with the aim of boosting the performance of both aspects. Compare to VO2 film, an improvement of 18.9% (from 29.6% to 48.5%) in the luminous transmittance as well as an increase of 6.0% (from 9.7% to 15.7%) in solar modulation efficiency is achieved when the molar ratio of Si/V attains 0.8. Based on the effective medium theory, we simulate the optical spectra of the composite films and the best thermochromic property is obtained when the filling factor attains 0.5, which is consistent with the experimental results. Meanwhile, the improvement of chemical stability for the composite film against oxidation has been confirmed. Tungsten is introduced to reduce the phase transition temperature to the ambient temperature, while maintain the thermochromism required for application as smart window. Our research set forth a new avenue in promoting practical applications of VO2-based thermochromic fenestration. PMID:25384345

  20. Solution-Processed VO2-SiO2 Composite Films with Simultaneously Enhanced Luminous Transmittance, Solar Modulation Ability and Anti-Oxidation property

    PubMed Central

    Zhao, Lili; Miao, Lei; Liu, Chengyan; Li, Chao; Asaka, Toru; Kang, Yipu; Iwamoto, Yuji; Tanemura, Sakae; Gu, Hui; Su, Huirong

    2014-01-01

    Recently, researchers spare no efforts to fabricate desirable vanadium dioxide (VO2) film which provides simultaneously high luminous transmittance and outstanding solar modulation ability, yet progress towards the optimization of one aspect always comes at the expense of the other. Our research devotes to finding a reproducible economic solution-processed strategy for fabricating VO2-SiO2 composite films, with the aim of boosting the performance of both aspects. Compare to VO2 film, an improvement of 18.9% (from 29.6% to 48.5%) in the luminous transmittance as well as an increase of 6.0% (from 9.7% to 15.7%) in solar modulation efficiency is achieved when the molar ratio of Si/V attains 0.8. Based on the effective medium theory, we simulate the optical spectra of the composite films and the best thermochromic property is obtained when the filling factor attains 0.5, which is consistent with the experimental results. Meanwhile, the improvement of chemical stability for the composite film against oxidation has been confirmed. Tungsten is introduced to reduce the phase transition temperature to the ambient temperature, while maintain the thermochromism required for application as smart window. Our research set forth a new avenue in promoting practical applications of VO2-based thermochromic fenestration. PMID:25384345

  1. Quantitative Estimation of Aluminum-Induced Negative Charge Region Top Area of SiO2 Based on Frequency-Dependent AC Surface Photovoltage

    NASA Astrophysics Data System (ADS)

    Shimizu, Hirofumi; Wakashima, Hiroya; Ishikawa, Takuma; Ikeda, Masanori

    2007-11-01

    Most aluminum (Al) in Al-contaminated and thermally oxidized n-type silicon (Si) dioxide (SiO2) is clarified to be segregated at the very top area of SiO2, causing a negative charge, as has been suggested by the formation of an (AlOSi)- network and/or AlO2- based on AC surface photovoltage (SPV). For a strongly inverted state at an oxidation temperature of 800 °C for 1 h, the thickness of the Al-induced negative charge region is quantitatively determined to be 2.4 nm on the basis of AC SPV after successive step etching and chemical analysis. As oxidation duration increased at 800 °C for 3 h, the strongly inverted state changed into a weakly inverted state, where the thickness of the Al-rich region is reduced (0.8 nm), proving that more than half of the (AlOSi)- network collapse and/or Al diffuses inside SiO2 during a longer oxidation duration.

  2. Thickness of the {SiO2}/{Si} interface and composition of silicon oxide thin films: effect of wafer cleaning procedures

    NASA Astrophysics Data System (ADS)

    Stedile, F. C.; Baumvol, I. J. R.; Oppenheim, I. F.; Trimaille, I.; Ganem, J.-J.; Rigo, S.

    1996-09-01

    We determined the areal density of Si atoms constituting the oxide-silicon interface and the stoichiometry of ultra-thin silicon oxide films, thermally grown on Si(001) in dry 18O 2 atmospheres, using the channeling of α-particles along the <001> axis of the Si substrates associated with grazing angle detection of the scattered particles. The amount of 18O atoms in the films was determined independently using the 18O(p,α) 15N nuclear reaction at 730 keV. The Si wafers were submitted to different cleaning procedures before oxidation in 18O 2, namely: standard RCA cleaning, HF etching followed by a rinse in ethanol and rapid thermal cleaning (RTC) under high vacuum. The stoichiometry of all oxide films having thicknesses between 2 and 13 nm could be fitted assuming a ratio {O}/{Si} = 2 , that is, the films were constituted by silicon dioxide. By comparing the results for samples cleaned in different ways, however, we noticed a pronounced change in the number of atoms in the non-registered Si layers at the {SiO2}/{Si} interface and so in the thickness of these interfaces.

  3. Magnetic nanoparticles induced dielectric enhancement in (La, Gd)2O3: SiO2 composite systems

    NASA Astrophysics Data System (ADS)

    Kao, T. H.; Mukherjee, S.; Yang, H. D.

    2013-11-01

    Magnetic Gd2O3 and non-magnetic La2O3 nanoparticles (NPs) have been synthesized together with different doping concentrations in SiO2 matrix via sol-gel route calcination at 700 °C and above. Properly annealed NP-glass composite systems show enhancement of dielectric constant and magnetodielectric effect (MDE) near room temperature, depending on superparamagnetic NPs concentrations. From application point of view, the enhancement of dielectric constant along with MDE can be achieved by tuning the NPs size through varying calcination temperature and/or increasing the doping concentration of magnetic rare earth oxide.

  4. High frequency capacitance-voltage characteristics of thermally grown SiO2 films on beta-SiC

    NASA Technical Reports Server (NTRS)

    Tang, S. M.; Berry, W. B.; Kwor, R.; Zeller, M. V.; Matus, L. G.

    1990-01-01

    Silicon dioxide films grown under dry and wet oxidation environment on beta-SiC films have been studied. The beta-SiC films had been heteroepitaxially grown on both on-axis and 2-deg off-axis (001) Si substrates. Capacitance-voltage and conductance-voltage characteristics of metal-oxide-semiconductor structures were measured in a frequency range of 10 kHz to 1 MHz. From these measurements, the interface trap density and the effective fixed oxide charge density were observed to be generally lower for off-axis samples.

  5. Optical properties of ion-beam-synthesized Au nanoparticles in SiO2 matrix

    NASA Astrophysics Data System (ADS)

    Hsieh, Chang-Lin; Oyoshi, Keiji; Chao, Der-Sheng; Tsai, Hsu-Sheng; Hong, Wei-Lun; Takeda, Yoshihiko; Liang, Jenq-Horng

    2016-05-01

    In recent years, gold (Au) nanoparticles have been synthesized via various methods and used in optical and biomedical detection. Au nanoparticles contain some remarkable dimension-dependent optical properties due to surface plasmon resonance (SPR) in Au nanoparticles which causes high absorption in visible light regions. Since SPR in well-crystallized Au nanoparticles can enhance the local electromagnetic field, it is thus expected that greater efficiency in the photoluminescence (PL) originating from oxygen deficiency centers (ODC) can be achieved in Au-implanted SiO2 matrix. In order to demonstrate the enhancement of PL, Au nanoparticles were formed in SiO2 film using ion beam synthesis and their optical and microstructural properties were also investigated in this study. The results revealed that a clear absorption peak at approximately 530 nm was identified in the UV-Vis spectra and was attributed to SPR induced by Au nanoparticles in SiO2. The SPR of Au nanoparticles is also dependent on thermal treatment conditions, such as post-annealing temperature and ambient. The Au nanoparticle-containing SiO2 film also displayed several distinctive peaks at approximately 320, 360, 460, and 600 nm in the PL spectra and were found to be associated with ODC-related defects and non-bridging oxygen hole centers (NBOHC) in SiO2. In addition, the PL peak intensities increased as post-annealing temperature increased, a finding contradictory to the defect recovery but highly consistent with the SPR tendency. A maximum PL emission was achieved when the Au-implanted SiO2 film was annealed at 1100 °C for 1 h under N2. Therefore, the existence of Au nanoparticles in SiO2 film can induce SPR effects as well as enhance PL emission resulting from defect-related luminescence centers.

  6. Fabrication of mechanically robust, self-cleaning and optically high-performance hybrid thin films by SiO2&TiO2 double-shelled hollow nanospheres

    NASA Astrophysics Data System (ADS)

    Yao, Lin; He, Junhui; Geng, Zhi; Ren, Tingting

    2015-07-01

    Low-cost antireflection (AR) thin films on large-area optical surfaces are important for high-performance optical devices, display devices and photovoltaic cells. In the current work, SiO2&TiO2 double-shell hollow nanospheres (DSHNs) were designed, synthesized and utilized as building blocks for fabricating multifunctional AR thin films. By optimizing the porosity of SiO2&TiO2 DSHN and thin film structure, substrates with DSHN thin films attained transmittance as high as 99.4% and average transmittance up to 98.5% in the visible region. The nano-composite SiO2-TiO2 films exhibited intrinsic superhydrophilicity, anti-fogging and high photocatalytic activity. Tape peeling test, sponge washing test, and high temperature and moisture proof test showed favorable robustness and functional durability of the thin films, which make them extremely attractive for applications in lenses, photovoltaic cells and windows of high-rise buildings.Low-cost antireflection (AR) thin films on large-area optical surfaces are important for high-performance optical devices, display devices and photovoltaic cells. In the current work, SiO2&TiO2 double-shell hollow nanospheres (DSHNs) were designed, synthesized and utilized as building blocks for fabricating multifunctional AR thin films. By optimizing the porosity of SiO2&TiO2 DSHN and thin film structure, substrates with DSHN thin films attained transmittance as high as 99.4% and average transmittance up to 98.5% in the visible region. The nano-composite SiO2-TiO2 films exhibited intrinsic superhydrophilicity, anti-fogging and high photocatalytic activity. Tape peeling test, sponge washing test, and high temperature and moisture proof test showed favorable robustness and functional durability of the thin films, which make them extremely attractive for applications in lenses, photovoltaic cells and windows of high-rise buildings. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02467f

  7. Fabrication and characterization of Er+3 doped SiO2/SnO2 glass-ceramic thin films for planar waveguide applications

    NASA Astrophysics Data System (ADS)

    Guddala, S.; Chiappini, A.; Armellini, C.; Turell, S.; Righini, G. C.; Ferrari, M.; Narayana Rao, D.

    2015-02-01

    Glass-ceramics are a kind of two-phase materials constituted by nanocrystals embedded in a glass matrix and the respective volume fractions of crystalline and amorphous phase determine the properties of the glass-ceramics. Among these properties transparency is crucial in particular when confined structures, such as, dielectric optical waveguides, are considered. Moreover, the segregation of dopant rare-earth ions, like erbium, in low phonon energy crystalline medium makes these structures more promising in the development of waveguide amplifiers. Here we are proposing a new class of low phonon energy tin oxide semiconductor medium doped silicate based planar waveguides. Er3+ doped (100-x) SiO2-xSnO2 (x= 10, 20, 25 and 30mol%), glass-ceramic planar waveguide thin films were fabricated by a simple sol-gel processing and dip coating technique. XRD and HRTEM studies indicates the glass-ceramic phase of the film and the dispersion of ~4nm diameter of tin oxide nanocrystals in the amorphous phase of silica. The spectroscopic assessment indicates the distribution of the dopant erbium ions in the crystalline medium of tin oxide. The observed low losses, 0.5±0.2 dB/cm, at 1.54 μm communication wavelength makes them a quite promising material for the development of high gain integrated optical amplifiers.

  8. Peculiarities of optical absorption originating from boundaries of quasi-crystalline Si-C-O-N films deposited on a SiO 2 amorphous-like substrate

    NASA Astrophysics Data System (ADS)

    Makowska-Janusik, M.

    2004-08-01

    The ultraviolet (UV)-absorption spectra, originating from boundaries formed by partially crystallised Si-C-O-N film deposited on a SiO 2 substrate, were simulated using a semi-empirical quantum-chemical parametrisation method (PM3). Several Si-C-O-N modelled structural clusters, covered with different types of atoms, namely: carbon, silicon, oxygen and hydrogen, were considered. The initial geometry of the investigated clusters was built following extended X-ray absorption fine structure experimental data. Each of the considered clusters was geometrically optimised by total energy minimisation to simulate the influence of the interface, formed between the films and substrate, on the electronic parameters of the investigated structure. Correlation was found between the total energy of a particular cluster, the values of the HOMO-LUMO energy gap splitting and the spectral features of the electronic density of states (DOS). A substantial influence of external sheets on spectral positions in the DOS was found. For the UV-absorption spectra, additional spectral maxima did appear upon changing of the Si-C-O-N covering sheet. The present work is devoted to a study of the influence of the cluster's boundary conditions (surrounding chosen cluster shell) on electronic properties and optical absorption of the corresponding Si-C-O-N clusters.

  9. Using instability of nanometric liquid Cu films on SiO2 substrates to determine the underlying van der Waals potential

    NASA Astrophysics Data System (ADS)

    González, Alejandro G.; Diez, Javier A.; Wu, Yueying; Fowlkes, Jason D.; Rack, Philip D.; Kondic, Lou

    2013-11-01

    We study the instability of nanometric Cu thin films on a SiO2 substrate. The metal is melted by means of laser pulses for some tens of nanoseconds. The free surface destabilizes during the liquid lifetime, leading to the formation of holes at first and to metal drops on the substrate in later stages. By analyzing the Fourier transforms of the SEM images obtained during the metal film evolution, we determine the emerging length scales for both early and late stages of the instability development. The results are analyzed within the framework of a long-wave hydrodynamic model, which introduces van der Waals forces by means of disjoining and conjoining pressures. These forces are characterized by a pair of exponents for the ratio h / h * , where h is the liquid thickness and h* is a residual one. We find that the pair (3 , 2) provides a good agreement for the relationship of the wavelength with maximum growth rate, λm, while other typical pairs, such as (4 , 3) and (9 , 3) do not provide accurate description of the experimental data. Supported by CONICET-Argentina grant PIP 844/2011 (AGG, JAD), and by NSF grants CBET-1235651 (PDR) and CBET-1235710 (LK).

  10. Stress relaxation in dual ion beam sputtered Nb2O5 and SiO2 thin films: application in a Fabry-Pérot filter array with 3D nanoimprinted cavities

    NASA Astrophysics Data System (ADS)

    Ullah, Anayat; Wilke, Hans; Memon, Imran; Shen, Yannan; Nguyen, Duc Toan; Woidt, Carsten; Hillmer, Hartmut

    2015-05-01

    Miniaturized spectrometers can be implemented using Fabry-Pérot (FP) filter arrays. Such filters are defined by two parallel mirrors with a resonance cavity in between. For high optical quality, ion beam sputtered distributed Bragg reflectors (DBRs), with alternating high and low refractive index material pairs, can be used as the FP mirrors; while 3D nanoimprint technology provides an efficient way of implementing multiple organic FP cavities of different heights in a single step. However, the high residual stress in ion beam sputtered films results in poor adhesion between the DBR films and the organic polymer cavities, causing debonding of the DBR. Therefore, the residual stress of the ion beam sputtered films forming the DBRs must be reduced. Niobium pentoxide (Nb2O5) and silicon dioxide (SiO2) are used as the DBR materials in this work due to their high index contrast, resulting in high reflectivity for only a few alternating pairs. Stress relaxation in ion beam sputtered Nb2O5 and SiO2 films is achieved in this work by deposition under simultaneous high energy ion bombardment (oxygen and argon gas mixture) from a second ion source. Using this technique, the film density and hence compressive film stress for both Nb2O5 and SiO2 films is reduced without introducing any additional optical absorption in the films. FP filter arrays fabricated with stress reduced Nb2O5 and SiO2 as DBR films exhibit high optical and mechanical performance, with good adhesion between the films and the polymer cavity.

  11. Optical and physical properties of solgel-derived GeO2:SiO2 films in photonic applications

    NASA Astrophysics Data System (ADS)

    Ho, Charles K. F.; Pal, Rajni; Djie, H. S.; Pita, Kantisara; Ngo, Nam Quoc; Osipowicz, T.

    2007-07-01

    The functionality of optical components relies heavily on the composition-dependent properties of germanosilicate materials, which include the refractive index, photosensitivity, and microstructural properties. Recent studies and parallel developments are presented of germanosilicate films with composition x of Ge content (i.e., xGeO2:(1-x)SiO2) that were synthesized by the solgel process for various integrated photonic applications undertaken. The following novel aspects are discussed with respect to the effect of composition of the glassy films (0.05≤x≤0.40): determination of spectral optical properties, UV imprinting of optical waveguides with relatively large index change (Δn), and quantum-well intermixing enhancement observed in InGaAs(P)/InP quantum-well optical devices. The implications of the results are discussed.

  12. Optical and physical properties of solgel-derived GeO2:SiO2 films in photonic applications.

    PubMed

    Ho, Charles K F; Pal, Rajni; Djie, H S; Pita, Kantisara; Ngo, Nam Quoc; Osipowicz, T

    2007-07-10

    The functionality of optical components relies heavily on the composition-dependent properties of germanosilicate materials, which include the refractive index, photosensitivity, and microstructural properties. Recent studies and parallel developments are presented of germanosilicate films with composition x of Ge content (i.e., xGeO(2):(1-x)SiO(2)) that were synthesized by the solgel process for various integrated photonic applications undertaken. The following novel aspects are discussed with respect to the effect of composition of the glassy films (0.05

  13. Organic-Modified SiO2 Thin Film Coatings Obtained by the Sol-Gel Method

    NASA Astrophysics Data System (ADS)

    Zareba-Grodź, I.; Szeluga, U.; Bukowska, E.; Hermanowicz, K.; Miśta, W.; Maruszewski, K.

    2006-02-01

    Transparent thin films of silica-containing organic copolymers have been obtained by combining organic photopolymerisation and the sol-gel method. The samples have been characterized via IR spectroscopy, N2-adsorption (77 K), thermal gravimetric analysis (TGA) and differential thermal analysis (DTA). The viscoelastic nature of the materials have been investigated via the DMTA technique by applying stress to the samples and monitoring their responses. Textural properties such as: specific surface areas (SBET), pore volume (Vp), average pore sizes (Rp) and micropore volumes (VDR) have been obtained. The complete adsorption-desorption isotherms and pore size distributions have been analyzed following the Dollimore-Heal method.

  14. Effects of addition of supramolecular assembly on the anatase nanocrystalline precipitation of sol-gel derived SiO2-TiO2 coating films by hot-water treatment.

    PubMed

    Katagiri, Kiyofumi; Harada, Genki; Matsuda, Atsunori; Kogure, Toshihiro; Muto, Hiroyuki; Sakai, Mototsugu

    2006-06-01

    Effects of the addition of a supramolecular assembly of cetyltrimethylammonium bromide in SiO2-TiO2 gel films on the formation of anatase type TiO2 nanocrystals with hot-water treatment were investigated. Anatase nanocrystals were formed in the whole SiO2-TiO2 gel films with the addition of cetyltrimethylammonium bromide by the treatment, whereas the nanocrystals were formed only on the film surface in the case of gel films without cetyltrimethylammonium bromide. Cetyltrimethylammonium bromide molecules in the SiO2-TiO2 gel films were completely removed by the hot-water treatment and the following UV irradiation. In the usual procedure for preparation of porous materials, the removal of template molecular assemblies required high temperature treatment over 400 degrees C. In this system, all the processes were performed at temperatures less than 100 degrees C. Additionally, the porous structure produced by the removal of micellar assembly allowed anatase nanocrystals to be formed inside the films. Therefore, the method presented in this work provides us with the novel photocatalyst coatings of porous membrane with highly-dispersed TiO2 nanocrystals via low temperature process. PMID:17025087

  15. The Study of Femtosecond Laser Irradiation on GaAs Solar Cells With TiO2/SiO2 Anti-Reflection Films

    NASA Astrophysics Data System (ADS)

    Hua, Yinqun; Shi, Zhiguo; Wu, Wenhui; Chen, Ruifang; Rong, Zhen; Ye, Yunxia; Liu, Haixia

    Femtosecond laser ablation on GaAs solar cells for space power has been investigated. In particular, we studied the effects of laser energy and laser number on the ablation of solar cells. Furthermore, the morphologies and microstructure of ablation were characterized by the non-contact optical profilometer and scanning electron microscope (SEM). The photovoltaic properties were tested by the volt ampere characteristic test system. The abaltion threshold of the TiO2/SiO2 anti-reflection film of GaAs solar cells was obtained from the linear fit of the dependence of the square diameter of the ablated area with the natural logarithm of the femtosecond laser pulse energy, the resulting threshold of the laser fluence is about 0.31J/cm2, and the corresponding energy is 5.4uJ. The ablation depth showed nonlinear dependence of energy. With the fixed energy 6uJ and the increasing laser number, the damage degree increases obviously. Furthermore, the electric properties also suffer a certain degradation. Among all the evaluated electric properties, the photoelectric conversion efficiency (η) degraded remarkably.

  16. Understanding surface core-level shifts using the Auger parameter: A study of Pd atoms adsorbed on ultrathin SiO2 films

    NASA Astrophysics Data System (ADS)

    Kaden, William E.; Büchner, Christin; Lichtenstein, Leonid; Stuckenholz, Stefanie; Ringleb, Franziska; Heyde, Markus; Sterrer, Martin; Freund, Hans-Joachim; Giordano, Livia; Pacchioni, Gianfranco; Nelin, Connie J.; Bagus, Paul S.

    2014-03-01

    Auger parameter (Δα) measurements have been employed to determine the extent to which initial- and final-state effects govern surface core-level shifts in x-ray photoelectron spectroscopy (XPS) measurements of Pd atoms confined between a bilayer SiO2 film and its Ru(0001) support. For atoms bound in this manner, we note negative binding energy shifts (ΔBEs) of ˜0.3 eV, relative to the Pd 3d peak position in the bulk, and attribute these shifts to large variations in the initial-state orbital energies of the supported atoms (˜1.1 eV towards EF), coupled with decreased final-state relaxation contributions (˜0.8 eV). Theoretical calculations reveal that, despite small partial positive charges and decreased final-state screening, the decreased 4d-5sp hybridization of the undercoordinated Pd atoms results in large enough upward 3d orbital-energy shifts to yield the net-negative ΔBE noted by XPS.

  17. Intensified magneto-resistance by rapid thermal annealing in magnetite (Fe3O4) thin film on SiO2 glass substrate

    NASA Astrophysics Data System (ADS)

    Kobori, H.; Morii, K.; Yamasaki, A.; Sugimura, A.; Taniguchi, T.; Horie, T.; Naitoh, Y.; Shimizu, T.

    2012-12-01

    We have observed large magneto-resistance (MR) intensified by rapid thermal annealing (RTA) in magnetite (Fe3O4) thin film (MTF) on SiO2 glass (a-SiO2) substrate. The MTF was produced by the RF magnetron sputtering method by using a magnetite target. The electrical resistivity (ER) of as-grown MTF (AG-MTF) showed the Mott's variable range hopping behavior, which implies that the AG-MTF is amorphous-like. Although the magneto-resistance (MR) ratio of bulk single crystal is very small except around the Verwey transition temperature (VTT), that of the AG-MTF showed moderately large below room temperature. Due to RTA of the AG-MTF by use of an IR image furnace, the MR ratio of MTFs was intensified, and especially by the annealing around the Curie temperature (585°C) of magnetite. Furthermore the ER of the rapid thermally annealed MTF (RTA-MTF) showed a slight kink at around the VTT, which indicates that the crystallinity of the RTA-MTF is higher than that of the AG-MTF The MTF produced by the RF magnetron sputtering method are composed of magnetite fine particles (MFPs). We consider that the directions of magnetic moments of MFPs in the MTF were spatially randomized by the RTA and the strong spin scattering of itinerant electrons transferring between adjacent MFPs caused the intensification of the MR ratio.

  18. Shock-induced transformations in the system NaAlSiO4-SiO2 - A new interpretation

    NASA Technical Reports Server (NTRS)

    Sekine, Toshimori; Ahrens, Thomas J.

    1992-01-01

    New internally consistent interpretations of the phases represented by the high pressure phase shock wave data for an albite-rich rock, jadeite, and nepheline in the system NaAlSiO4-SiO2, are obtained using the results of static high pressure investigations, and the recent discovery of the hollandite phase in a shocked meteorite. We conclude that nepheline transforms directly to the calcium ferrite structure, whereas albite transforms possibly to the hollandite structure. Shock Hugoniots for the other plagioclase and alkali feldspars also indicate that these transform to hollandite structures. The pressure-volume data at high pressure could alternatively represent the compression of an amorphous phase. Moreover, the shock Hugoniot data are expected to reflect the properties of the melt above shock stresses of 60-80 GPa. The third order Birch-Murnaghan equation of state parameters are given for the calcium ferrite type NaAlSiO4 and for albite-rich, orthoclase-rich, and anorthite-rich hollandites.

  19. Formation and characterization of high-density FeSi nanodots on SiO2 induced by remote H2 plasma

    NASA Astrophysics Data System (ADS)

    Zhang, Hai; Makihara, Katsunori; Ohta, Akio; Ikeda, Mitsuhisa; Miyazaki, Seiichi

    2016-01-01

    We demonstrated the formation of high-density iron silicide nanodots (NDs) on thermally grown SiO2 by exposing an electron-beam-evaporated Fe/amorphous-Si/Fe (Fe/a-Si/Fe) trilayer stack to remote H2 plasma without any external heating and characterized their silicidation state and crystalline phase. After the remote H2 plasma exposure, the formation of NDs with an areal density of ˜4.3 × 1011 cm-2 and an average height of ˜7.1 nm was confirmed. X-ray photoelectron spectroscopy (XPS) analyses indicate silicidation reaction induced by the remote H2 plasma exposure, which was accompanied by the agglomeration of Fe and Si atoms on the SiO2 surface. The formation of a crystalline β-FeSi2 phase was confirmed by Raman scattering spectroscopy and XRD pattern measurements. The electrical separation among the β-FeSi2 NDs was confirmed from changes in surface potential due to charging of the dots. The surface potential of the NDs changed in a stepwise manner with respect to the tip voltage because of multistep electron injection into and extraction from the semiconductor β-FeSi2 NDs.

  20. Effect of multilayer structure on high-frequency properties of FeCo/(FeCo)0.63(SiO2)0.37 nanogranular films on flexible substrates

    PubMed Central

    2013-01-01

    The high-frequency properties of the FeCo-SiO2 monolayer nanogranular films and FeCo/(FeCo)0.63(SiO2)0.37 multilayer nanogranular films which were elaborated on flexible substrates by magnetron sputtering system were studied. Compared to the monolayer films with the same FeCo content, the multilayer structures comprised of FeCo/(FeCo)0.63(SiO2)0.37 exhibit more excellent properties that the real and imaginary parts of permeability, more than the double value of the monolayer, increase to 250 and 350, respectively. The variation was considered owing to the reduction of the anisotropy field. PMID:23641952

  1. Plasmon-induced charge separation at two-dimensional gold semishell arrays on SiO2@TiO2 colloidal crystals

    NASA Astrophysics Data System (ADS)

    Wu, Ling; Nishi, Hiroyasu; Tatsuma, Tetsu

    2015-10-01

    Photoelectrodes based on plasmonic Au semishell (or halfshell) arrays are developed. A colloidal crystal consisting of SiO2@TiO2 core-shell particles is prepared on a TiO2-coated transparent electrode. A Au semishell (or halfshell) array is deposited by sputtering or evaporation on the colloidal crystal. An electrode with the semishell (or halfshell) array exhibits negative photopotential shifts and anodic photocurrents under visible light at 500-800 nm wavelengths in an aqueous electrolyte containing an electron donor. In particular, hydroquinone and ethanol are good electron donors. The photocurrents can be explained in terms of plasmon-induced charge separation at the Au-TiO2 interface.

  2. Dry etched SiO2 Mask for HgCdTe Etching Process

    NASA Astrophysics Data System (ADS)

    Chen, Y. Y.; Ye, Z. H.; Sun, C. H.; Deng, L. G.; Zhang, S.; Xing, W.; Hu, X. N.; Ding, R. J.; He, L.

    2016-04-01

    A highly anisotropic etching process with low etch-induced damage is indispensable for advanced HgCdTe (MCT) infrared focal plane array (IRFPA) detectors. The inductively coupled plasma (ICP) enhanced reactive ion etching technique has been widely adopted in manufacturing HgCdTe IRFPA devices. An accurately patterned mask with sharp edges is decisive to accomplish pattern duplication. It has been reported by our group that the SiO2 mask functions well in etching HgCdTe with high selectivity. However, the wet process in defining the SiO2 mask is limited by ambiguous edges and nonuniform patterns. In this report, we patterned SiO2 with a mature ICP etching technique, prior to which a thin ZnS film was deposited by thermal evaporation. The SiO2 film etching can be terminated at the auto-stopping point of the ZnS layer thanks to the high selectivity of SiO2/ZnS in SF6 based etchant. Consequently, MCT etching was directly performed without any other treatment. This mask showed acceptable profile due to the maturity of the SiO2 etching process. The well-defined SiO2 pattern and the etched smooth surfaces were investigated with scanning electron microscopy and atomic force microscope. This new mask process could transfer the patterns exactly with very small etch-bias. A cavity with aspect-ratio (AR) of 1.2 and root mean square roughness of 1.77 nm was achieved first, slightly higher AR of 1.67 was also get with better mask profile. This masking process ensures good uniformity and surely benefits the delineation of shrinking pixels with its high resolution.

  3. Dry etched SiO2 Mask for HgCdTe Etching Process

    NASA Astrophysics Data System (ADS)

    Chen, Y. Y.; Ye, Z. H.; Sun, C. H.; Deng, L. G.; Zhang, S.; Xing, W.; Hu, X. N.; Ding, R. J.; He, L.

    2016-09-01

    A highly anisotropic etching process with low etch-induced damage is indispensable for advanced HgCdTe (MCT) infrared focal plane array (IRFPA) detectors. The inductively coupled plasma (ICP) enhanced reactive ion etching technique has been widely adopted in manufacturing HgCdTe IRFPA devices. An accurately patterned mask with sharp edges is decisive to accomplish pattern duplication. It has been reported by our group that the SiO2 mask functions well in etching HgCdTe with high selectivity. However, the wet process in defining the SiO2 mask is limited by ambiguous edges and nonuniform patterns. In this report, we patterned SiO2 with a mature ICP etching technique, prior to which a thin ZnS film was deposited by thermal evaporation. The SiO2 film etching can be terminated at the auto-stopping point of the ZnS layer thanks to the high selectivity of SiO2/ZnS in SF6 based etchant. Consequently, MCT etching was directly performed without any other treatment. This mask showed acceptable profile due to the maturity of the SiO2 etching process. The well-defined SiO2 pattern and the etched smooth surfaces were investigated with scanning electron microscopy and atomic force microscope. This new mask process could transfer the patterns exactly with very small etch-bias. A cavity with aspect-ratio (AR) of 1.2 and root mean square roughness of 1.77 nm was achieved first, slightly higher AR of 1.67 was also get with better mask profile. This masking process ensures good uniformity and surely benefits the delineation of shrinking pixels with its high resolution.

  4. Growth of CsLiB6O10 thin films on Si substrate by pulsed laser deposition using SiO2 and CaF2 as buffer layers

    NASA Astrophysics Data System (ADS)

    Yeo, J. S.; Akella, A.; Huang, T. F.; Hesselink, L.

    1998-03-01

    CsLiB6O10 (CLBO) thin films are grown on Si (100) and (111) substrates using lower index SiO2 and CaF2 as buffer layers by pulsed KrF (248 nm) excimer laser ablation of stoichiometric CLBO targets over a temperature range of 425 to 725°C. A CaF2 buffer layer is grown on Si by laser ablation while SiO2 is prepared by standard thermal oxidation. From extended x-ray analysis, it is determined that CaF2 is growth with preferred orientation on Si (100) at temperatures lower than 525°C while on Si (111) substrate, CaF2 is grown epitaxially over the temperature range; this agrees well with observed reflection high energy electron diffraction patterns. X-ray 2θ-scans indicate that crystalline CLBO are grown on SiO2/Si and CaF2/Si (100). Analysis of reflectance spectra from CLBO/SiO2/Si yields the absorption edge at 182 nm. Surface roughness of the CaF2 and CLBO/CaF2/Si film are 19 and 15 nm, respectively. This relatively rough surface caused by the ablation of wide bandgap CaF2 and CLBO limits the application of CLBO for waveguiding measurement.

  5. Direct measurements of irradiation-induced creep in micropillars of amorphous Cu56Ti38Ag6, Zr52Ni48, Si, and SiO2

    NASA Astrophysics Data System (ADS)

    Özerinç, Sezer; Kim, Hoe Joon; Averback, Robert S.; King, William P.

    2015-01-01

    We report in situ measurements of irradiation-induced creep on amorphous (a-) Cu56Ti38Ag6, Zr52Ni48, Si, and SiO2. Micropillars 1 μm in diameter and 2 μm in height were irradiated with ˜2 MeV heavy ions during uniaxial compression at room temperature. The creep measurements were performed using a custom mechanical testing apparatus utilizing a nanopositioner, a silicon beam transducer, and an interferometric laser displacement sensor. We observed Newtonian flow in all tested materials. For a-Cu56Ti38Ag6, a-Zr52Ni48, a-Si, and Kr+ irradiated a-SiO2 irradiation-induced fluidities were found to be nearly the same, ≈3 GPa-1 dpa-1, whereas for Ne+ irradiated a-SiO2 the fluidity was much higher, 83 GPa-1 dpa-1. A fluidity of 3 GPa-1 dpa-1 can be explained by point-defect mediated plastic flow induced by nuclear collisions. The fluidity of a-SiO2 can also be explained by this model when nuclear stopping dominates the energy loss, but when the electronic stopping exceeds 1 keV/nm, stress relaxation in thermal spikes also contributes to the fluidity.

  6. Fracture-induced amorphization of polycrystalline SiO2 stishovite: a potential platform for toughening in ceramics

    PubMed Central

    Nishiyama, Norimasa; Wakai, Fumihiro; Ohfuji, Hiroaki; Tamenori, Yusuke; Murata, Hidenobu; Taniguchi, Takashi; Matsushita, Masafumi; Takahashi, Manabu; Kulik, Eleonora; Yoshida, Kimiko; Wada, Kouhei; Bednarcik, Jozef; Irifune, Tetsuo

    2014-01-01

    Silicon dioxide has eight stable crystalline phases at conditions of the Earth's rocky parts. Many metastable phases including amorphous phases have been known, which indicates the presence of large kinetic barriers. As a consequence, some crystalline silica phases transform to amorphous phases by bypassing the liquid via two different pathways. Here we show a new pathway, a fracture-induced amorphization of stishovite that is a high-pressure polymorph. The amorphization accompanies a huge volume expansion of ~100% and occurs in a thin layer whose thickness from the fracture surface is several tens of nanometers. Amorphous silica materials that look like strings or worms were observed on the fracture surfaces. The amount of amorphous silica near the fracture surfaces is positively correlated with indentation fracture toughness. This result indicates that the fracture-induced amorphization causes toughening of stishovite polycrystals. The fracture-induced solid-state amorphization may provide a potential platform for toughening in ceramics. PMID:25297473

  7. Using shaped pulses to probe energy deposition during laser-induced damage of SiO2 surfaces

    SciTech Connect

    Carr, C W; Cross, D; Feit, M D; Bude, J D

    2008-10-24

    Laser-induced damage initiation in silica has been shown to follow a power-law behavior with respect to pulse-length. Models based on thermal diffusion physics can successfully predict this scaling and the effect of pulse shape for pulses between about 3ns and 10ns. In this work we use sophisticated new measurement techniques and novel pulse shape experiments to test the limits of this scaling. We show that simple pulse length scaling fails for pulses below about 3ns. Furthermore, double pulse initiation experiments suggest that energy absorbed by the first pulse is lost on time scales much shorter than would be predicted for thermal diffusion. This time scale for energy loss can be strongly modulated by maintaining a small but non-zero intensity between the pulses. By producing damage with various pulse shapes and pulse trains it is demonstrated that the properties of any hypothetical thermal absorber become highly constrained.

  8. Time-resolved imaging of material response during laser-induced bulk damage in SiO2

    SciTech Connect

    Demos, S G; Negres, R A

    2008-10-24

    We report on time resolved imaging of the dynamic events taking place during laser-induced damage in the bulk of fused silica samples with nanosecond temporal resolution and one micron spatial resolution. These events include: shock/pressure wave formation and propagation, transient absorption, crack propagation and formation of residual stress fields. The work has been performed using a time-resolved microscope system that utilizes a probe pulse to acquire images at delay times covering the entire timeline of a damage event. Image information is enhanced using polarized illumination and simultaneously recording the two orthogonal polarization image components. For the case of fused silica, an electronic excitation is first observed accompanied by the onset of a pressure wave generation and propagation. Cracks are seen to form early in the process and reach their final size at about 25 ns into the damage event. In addition, changes that in part are attributed to transient absorption in the modified material are observed for delays up to about 200 microseconds.

  9. O atoms loss coefficient on porous SiO2 and TiO2 measured by plasma induced fluorescence

    NASA Astrophysics Data System (ADS)

    Allegraud, Katia; Gatilova, Lina; Guaitella, Olivier; Guillon, Jean; Rousseau, Antoine

    2006-10-01

    The time evolution of O atoms density in the gas phase during the post-discharge of a pulsed plasma is studied using a plasma induced fluorescence technique (PIF): a main long pulse creates the plasma and a shorter one re-excites atoms in the time post-discharge was used. The gas pressure is 133 Pa in N2/O2 mixture and the plasma is a pulsed DC discharge. The surface loss coefficient of O atoms on pyrex, porous silica, porous TiO2 is measured, this latter being a photocatalytic material. It is shown that the presence of porous silica or TiO2 leads to a stong increase of the O atom surface loss coefficient. When nano cluster of TiO2 are deposited on porous silica, the loss coefficient is first high and comparable to the case of the porous silica, but decreases after few milliseconds. Such a decrease of the surface loss coefficient has recently been reported in a pulsed microwave discharge [1]. The effect of the pre-irradiation of the porous materials by external ultraviolet is also studied. [1] G. Cartry, X. Duten and A. Rousseau Plasma Sources Sci. Technol. 15 (2006) 479--488

  10. Electrical behavior of MIS devices based on Si nanoclusters embedded in SiOxNy and SiO2 films

    PubMed Central

    2011-01-01

    We examined and compared the electrical properties of silica (SiO2) and silicon oxynitride (SiOxNy) layers embedding silicon nanoclusters (Sinc) integrated in metal-insulator-semiconductor (MIS) devices. The technique used for the deposition of such layers is the reactive magnetron sputtering of a pure SiO2 target under a mixture of hydrogen/argon plasma in which nitrogen is incorporated in the case of SiOxNy layer. Al/SiOxNy-Sinc/p-Si and Al/SiO2-Sinc/p-Si devices were fabricated and electrically characterized. Results showed a high rectification ratio (>104) for the SiOxNy-based device and a resistive behavior when nitrogen was not incorporating (SiO2-based device). For rectifier devices, the ideality factor depends on the SiOxNy layer thickness. The conduction mechanisms of both MIS diode structures were studied by analyzing thermal and bias dependences of the carriers transport in relation with the nitrogen content. PMID:21711698

  11. In vacuo growth studies of Ru thin films on Si, SiN, and SiO2 by high-sensitivity low energy ion scattering

    NASA Astrophysics Data System (ADS)

    Coloma Ribera, R.; van de Kruijs, R. W. E.; Sturm, J. M.; Yakshin, A. E.; Bijkerk, F.

    2016-08-01

    In vacuo high-sensitivity low energy ion scattering (HS-LEIS) has been used to investigate the initial growth stages of DC sputtered Ru on top of Si, SiN, and SiO2. The high surface sensitivity of this technique allowed an accurate determination of surface coverages and thicknesses required for closing the Ru layer on all three substrates. The Ru layer closes (100% Ru surface signal) at about 2.0, 3.2, and 4.7 nm on top of SiO2, SiN, and Si, respectively. In-depth Ru concentration profiles can be reconstructed from the Ru surface coverages when considering an error function like model. The large intermixing (4.7 nm) for the Ru-on-Si system is compared to the reverse system (Si-on-Ru), where only 0.9 nm intermixing occurs. The difference is predominantly explained by the strong Si surface segregation that is observed for Ru-on-Si. This surface segregation effect is also observed for Ru-on-SiN but is absent for Ru-on-SiO2. For this last system, in vacuo HS-LEIS analysis revealed surface oxygen directly after deposition, which suggests an oxygen surface segregation effect for Ru-on-SiO2. In vacuo XPS measurements confirmed this hypothesis based on the reaction of Ru with oxygen from the SiO2, followed by oxygen surface segregation.

  12. Analysis of thermal detrapping of holes created by electron irradiation in high purity amorphous SiO2 using the induced and secondary current measurements

    NASA Astrophysics Data System (ADS)

    Said, K.; Moya, G.; Si Ahmed, A.; Damamme, G.; Kallel, A.

    2016-01-01

    Isothermal detrapping of holes after electron irradiation (using a SEM) in high purity amorphous SiO2 is evaluated at different temperatures (in the range 300-663 K) by means of the induced and secondary current measurements. In order to single out the hole detrapping, the specific charging conditions (1 keV defocused electron beam of low density) leading to positive charging are adopted. The thermal detrapping, which stems from a single trap, begins at 523 K and is completed at 663 K. After annealing in air at 973 K during 48 h, two detrapping stages are revealed: the former is connected with an additional shallow trap, while the latter requires temperatures above 663 K for a complete detrapping. The first order kinetics describes reasonably well the detrapping process. The frequency factors (near 1010 s-1) and the activation energies (about 1.6 eV) deduced from this analysis could be assigned, respectively, to the relaxation connected to detrapping and to the trap energy level of the charged oxygen vacancy.

  13. Orientation-induced enhancement in electromagnetic properties of ZnFe2O4/SiO2/PANI core/shell/shell nanostructured disks

    NASA Astrophysics Data System (ADS)

    Wang, Jiaheng; Or, Siu Wing

    2016-05-01

    ZnFe2O4/SiO2/PANI (ZSP) core/shell/shell nanostructured disks are prepared and fabricated into paraffin-bonded ZSP composite rings with random, vertical, and horizontal orientations of the easy magnetization planes of the ZSP disks in the paraffin binder in order to study the effect of directional orientation of the easy magnetization planes on their electromagnetic properties. The easy magnetization planes induced by shape anisotropy and oriented by a magnetic field in the vertically oriented ring result in a general enhancement in permeability of 7-60% in the broad UHF-Ku (0.1-18 GHz) bands, while those in the horizontally oriented ring lead to a significant enhancement of 58-1100% in the low-frequency L and S (1-4 GHz) bands, in comparison with the randomly oriented ring. The observed permeability agrees with the theoretical prediction based on the Landau-Lifshitz-Gilbert equation and the Bruggeman's effective medium theory. The horizontal and vertical arrangements of dipolar polarizations in the vertically and horizontally oriented rings give rise to 3-11% enhancement and weakening in permittivity, respectively, compared to the randomly oriented ring. The enhancement in permeability also improves and broadens the electromagnetic wave absorption in both vertically and horizontally oriented rings, especially in the L and S bands for the horizontally oriented ring.

  14. Densification and residual stress induced by CO2 laser-based mitigation of SiO2 surfaces

    SciTech Connect

    Feit, M D; Matthews, M J; Soules, T F; Stolken, J S

    2010-10-21

    Knowing the ultimate surface morphology resulting from CO{sub 2} laser mitigation of induced laser damage is important both for determining adequate treatment protocols, and for preventing deleterious intensification upon subsequent illumination of downstream optics. Physical effects such as evaporation, viscous flow and densification can strongly affect the final morphology of the treated site. Evaporation is a strong function of temperature and will play a leading role in determining pit shapes when the evaporation rate is large, both because of material loss and redeposition. Viscous motion of the hot molten material during heating and cooling can redistribute material due to surface tension gradients (Marangoni effect) and vapor recoil pressure effects. Less well known, perhaps, is that silica can densify as a result of structural relaxation, to a degree depending on the local thermal history. The specific volume shrinkage due to structural relaxation can be mistaken for material loss due to evaporation. Unlike evaporation, however, local density change can be reversed by post annealing. All of these effects must be taken into account to adequately describe the final morphology and optical properties of single and multiple-pass mitigation protocols. We have investigated, experimentally and theoretically, the significance of such densification on residual stress and under what circumstances it can compete with evaporation in determining the ultimate post treatment surface shape. In general, understanding final surface configurations requires taking all these factors including local structural relaxation densification, and therefore the thermal history, into account. We find that surface depressions due to densification can dominate surface morphology in the non-evaporative regime when peak temperatures are below 2100K.

  15. Enhanced and Retarded SiO2 Growth on Thermally Oxidized Fe-Contaminated n-Type Si(001) Surfaces

    NASA Astrophysics Data System (ADS)

    Shimizu, Hirofumi; Hagiwara, Hiroyuki

    2013-04-01

    At the beginning of the oxidation of Fe-contaminated n-type Si(001) surfaces, Fe reacted with oxygen (O2) on the silicon (Si) substrate to form Fe2O3 and oxygen-induced point defects (emitted Si + vacancies). SiO2 growth was mainly enhanced by catalytic action of Fe. At 650 °C, SiO2 growth of the contaminated samples was faster than in reference samples rinsed in RCA solution during the first 60 min. However, it substantially slowed and became less than that of the reference samples. As the oxidation advanced, approximately half of the contaminated Fe atoms became concentrated close to the surface area of the SiO2 film layer. This Fe2O3-rich SiO2 layer acted as a diffusion barrier against oxygen species. The diffusion of oxygen atoms toward the SiO2/Si interface may have been reduced, and in turn, the emission of Si self-interstitials owing to oxidation-induced strain may have been decreased at the SiO2/Si interface, resulting in the retarded oxide growth. These results are evidence that emitted Si self-interstitials are oxidized not in the Fe2O3-rich SiO2 layer, but at the SiO2/Si interface in accordance with a previously proposed model. A possible mechanism based on the interfacial Si emission model is discussed. The activation energies for the oxide growth are found to be in accord with the enhanced and reduced growths of the Fe-contaminated samples.

  16. Testing Asymmetry in Plasma-Ball Growth Seeded by a Nanoscale Absorbing Defect Embedded in a SiO2 Thin-Film Matrix Subjected to UV Pulsed-Laser Radiation

    SciTech Connect

    Papernov, S.; Schmid, A.W.

    2008-09-16

    Previous studies of ultraviolet, nanosecond-pulsed-laser damage in thin films revealed nanoscale absorbing defects as a major source of damage initiation. It was also demonstrated that damage (crater formation) is facilitated by plasma-ball formation around absorbing defects. In this work an attempt is made to verify the symmetry of the plasma ball by irradiating SiO2 thin film with embedded gold nanoparticles from the side of either the air/film or substrate/film interfaces. Crater-formation thresholds derived in each case support preferential plasma-ball growth in the direction of the laser-beam source. The strong impact of internal E-field distribution is identified.

  17. Quantum-confinement effect in individual Ge1-xSnx quantum dots on Si(111) substrates covered with ultrathin SiO2 films using scanning tunneling spectroscopy

    NASA Astrophysics Data System (ADS)

    Nakamura, Yoshiaki; Masada, Akiko; Ichikawa, Masakazu

    2007-07-01

    The authors observed a quantum-confinement effect in individual Ge1-xSnx quantum dots (QDs) on Si (111) substrates covered with ultrathin SiO2 films using scanning tunneling spectroscopy at room temperature. The quantum-confinement effect was featured by an increase in the energy band gap of ˜1.5eV with a decrease in QD diameter from 35to4nm. The peaks for quantum levels of QDs became broader with a decrease in the height-diameter aspect ratio of QDs, demonstrating the gradual emergence of two dimensionality in density of states of quasi zero-dimensional QDs with the QD flattening.

  18. Epitaxial growth of ultrahigh density Ge1-xSnx quantum dots on Si (111) substrates by codeposition of Ge and Sn on ultrathin SiO2 films

    NASA Astrophysics Data System (ADS)

    Nakamura, Yoshiaki; Masada, Akiko; Cho, Sung-Pyo; Tanaka, Nobuo; Ichikawa, Masakazu

    2007-12-01

    A method to form epitaxial Ge1-xSnx quantum dots (QDs) on Si (111) substrates has been developed by codeposition of Ge and Sn on ultrathin SiO2 films with predeposited Ge nuclei. Hemispherical Ge1-xSnx QDs with an ultrahigh density (˜1012 cm-2) were epitaxially grown in the nanometer-size range. The QD size was controlled by changing the GeSn deposition amount. High-resolution transmission electron microscopy observations revealed that the main formed Ge1-xSnx QDs had less strain and no misfit dislocations.

  19. Effects of Line and Pillar Array Microengineered SiO2 Thin Films on the Osteogenic Differentiation of Human Bone Marrow-Derived Mesenchymal Stem Cells.

    PubMed

    Carvalho, Angela; Pelaez-Vargas, Alejandro; Hansford, Derek J; Fernandes, Maria H; Monteiro, Fernando J

    2016-02-01

    A primary goal in bone tissue engineering is the design of implants that induce controlled, guided, and rapid healing. The events that normally lead to the integration of an implant into bone and determine the performance of the device occur mainly at the tissue-implant interface. Topographical surface modification of a biomaterial might be an efficient tool for inducing stem cell osteogenic differentiation and replace the use of biochemical stimuli. The main goal of this work was to develop micropatterned bioactive silica thin films to induce the osteogenic differentiation of human bone marrow-derived mesenchymal stem cells (hMSCs) only through topographical stimuli. Line and pillar micropatterns were developed by a combination of sol-gel/soft lithography and characterized by scanning electron microscopy, atomic force microscopy, and contact angle measurements. hMSCs were cultured onto the microfabricated thin films and flat control for up to 21 days under basal conditions. The micropatterned groups induced levels of osteogenic differentiation and expression of osteoblast-associated markers higher than those of the flat controls. Via comparison of the micropatterns, the pillars caused a stronger response of the osteogenic differentiation of hMSCs with a higher level of expression of osteoblast-associated markers, ALP activity, and extracellular matrix mineralization after the cells had been cultured for 21 days. These findings suggest that specific microtopographic cues can direct hMSCs toward osteogenic differentiation. PMID:26771563

  20. Cu doping effect on FePt grains prepared by rapid thermal annealing on SiO2 substrate and wall structure in TbFeCo/FePt CGC-like film

    NASA Astrophysics Data System (ADS)

    Itoh, Akiyoshi; Itoh, Yujii; Nanba, Kensuke; Adachi, Yoshiharu; Motohashi, Masataka; Tsukamoto, Arata

    2006-04-01

    We report that Cu substitution is effective in raising the degree of (001) crystal orientation of FePt grains prepared by rapid thermal annealing on SiO2. We fabricated coupled granular and continuous (CGC) like films such as TbFeCo on FePt grains. The wall coercivity was about twice that of the TbFeCo single layer film. From three-dimensional micromagnetic simulations with Landau-Lifshitz-Gilbert (LLG) equation, it was confirmed that wall coercivity was enhanced and domain shapes made smooth in CGC film. When the thickness of the TbFeCo layer was thin, wall width was thinner than the theoretical value.

  1. Imaging of electronic defect states in SiO2 and HfSiOx films with sub-nanometer spatial resolution by two-way Single Electron Tunneling Force Mircroscopy

    NASA Astrophysics Data System (ADS)

    Johnson, J. P.; Zheng, N.; Williams, C. C.

    2007-03-01

    Electronic defects in dielectric materials are currently in sharp focus, for nano-technology and quantum information processing. A novel technique has been developed for imaging these states with sub-nanometer spatial resolution. It can be applied to completely non-conducting dielectric films, in contrast to the STM. The method is based on force detected single electron tunneling events to and from the defect states [1-3]. The exponential dependence of the tunneling rate on tip-sample gap provides the same spatial resolution as STM. An oscillating AFM tip is scanned at constant height above the sample surface. A voltage waveform, synchronous with the tip motion is applied. When the tip is above an accessible state, individual electrons shuttle between tip and state with the applied voltage (300 Hz). The two-way tunneling causes a detectable change in tip resonance. Images of SiO2 and HfSiOx films show a repeatable, random array of individual ``point-like'' defect states, some with sub-nanometer width. Spectroscopic measurements of the defect energy are also performed by this approach. The new method and an analysis of the defects in SiO2 and HfSiOx will be presented. [1] E Bussman et al., Appl. Phys. Lett. 85, 2538 (2004) [2] E Bussman and CC Williams, Appl. Phys. Lett. 88, 263108 (2006) [3] E Bussman et al., Nano Lett. 6, 2577 (2006)

  2. Ferroelectric properties of Bi2VO5.5 thin films on LaAlO3 and SiO2/Si substrates with LaNiO3 base electrode

    NASA Astrophysics Data System (ADS)

    Satyalakshmi, K. M.; Varma, K. B. R.; Hegde, M. S.

    1995-07-01

    Ferroelectric bismuth vanadate Bi2VO5.5 (BVO) thin films have been grown on LaAlO3 (LAO) and SiO2/Si substrates with LaNiO3 (LNO) base electrodes by the pulsed laser deposition technique. The effect of substrate temperature on the ferroelectric properties of BVO thin films, has been studied by depositing the thin films at different temperatures. The BVO thin films grown on LNO/LAO were textured whereas the thin films grown on LNO/SiO2/Si were polycrystalline. The BVO thin films grown at 450 °C exhibited good ferroelectric properties indicating that LNO acts as a good electrode material. The remanent polarization Pr and coercive field Ec obtained for the BVO thin films grown at 450 °C on LNO/LAO and LNO/SiO2/Si were 2.5 μC/cm2, 37 kV/cm and 4.6μC/cm2, 93 kV/cm, respectively.

  3. Influence of SiO2/In2O3 film acoustical waveguide on the mode index of Ti:LiNbO3 optical waveguide in acousto-optical mode converter

    NASA Astrophysics Data System (ADS)

    Lin, Hang-you; Ning, Ji-ping; Geng, Fan

    2004-04-01

    TE/TM mode converter is a key element of integrated acoustooptical tunable filter (AOTF). Employing SiO2/In2O3 film as acoustical waveguide can suppress sidelobes effectively and simplify fabrication technique in integrated quasi-collinear AOTF. In this report, the eigenvalue equation and the field solution of such configuration has been obtained by using modified Wenzel-Kramers-Brillouin (WKB) method. The results are compared with those by using vector finite element method (VFEM). When the optical waveguides are covered by such oxide film, the difference of mode indices of both polarizations and the effective propagation velocity of surface acoustical wave (SAW) will decrease, and these decreases lead the shift of optical wavelength, which mainly results in the change of the former.

  4. Study on the laser-induced damage performance of HfO2, Sc2O3, Y2O3, Al2O3 and SiO2 monolayer coatings

    NASA Astrophysics Data System (ADS)

    Zhu, Meiping; Yi, Kui; Li, Dawei; Qi, Hongji; Zhao, Yuanan; Liu, Jie; Liu, Xiaofeng; Hu, Guohang; Shao, Jianda

    2013-11-01

    The laser induced damage threshold (LIDT) and damage morphology of the monolayer coating are easily influenced by the finish condition of the substrate, which makes it difficult to compare the LIDT of different coating materials. In order to eliminate the influence of defect and sub-defect on the substrate, HfO2, Sc2O3, Y2O3, Al2O3 and SiO2 monolayer coatings were prepared on 1064 nm HfO2/SiO2 high reflection coatings, using conventional e-beam deposition. The LIDT, as well as the damage morphology after laser irradiation at wavelength of 1064 nm, was measured and compared with that of the monolayer coating deposited on BK7 glass substrate.

  5. Preparation and Characterization of SnO2-Nanoparticle-Included Ink Solution and Its Application to the Patterned Pt Films on SiO2/Si Substrates.

    PubMed

    Lee, Su Yeon; Lee, Ho Nyun; Kim, Hyun Jong; Lee, Seong Eui; Lee, Hee Chul

    2015-11-01

    Pure SnO2 nanoparticles with a single tetragonal phase were fabricated and characterized for use as ink solution. It was possible to obtain the SnO2 nanoparticles through the calcination process of SnC204 powders prepared by a hydrothermal reaction of an aqueous solution containing SnCl2 x 2H2O and H2C2O4. The SnO2 powder, synthesized at 600 degrees C, showed a single tetragonal phase, while the powders synthesized at 550 degrees C or lower were composed of a mixture of tetragonal and orthorhombic phases. The particle size of the SnO2 powder with single tetragonal phase was as small as 100 nm and its surface specific area was 12.31 m2/g. It was possible to fabricate the SnO2-nanoparticle-included ink solution for nanoparticle printing by adding a small amount of the previously prepared SnO2 powder to an aqueous solution of glycerol. The region of SnO2 nanoparticles formed by dropping the ink solution was able to successfully fill the gaps between Pt electrodes patterned on SiO2/Si substrates; the range of the gap between the electrodes was from 10 to 100 μm. PMID:26726540

  6. The properties of SiO 2 films using direct photo-chemical vapor deposition on strained SiGe layers

    NASA Astrophysics Data System (ADS)

    Lin, C. T.; Chang, S. J.; Nayak, D. K.; Shiraki, Y.

    1996-02-01

    Low temperature silicon-dioxide (SiO 2) layers were deposited on strained SiGe by using direct photo-chemical vapor deposition (DPCVD) with a deuterium lamp as the excitation source. It was found that the deposition rate increases linearly with the chamber pressure. The Auger electron spectroscopy profile shows that neither was Ge rejected nor was a Ge-rich layer formed after devices were fabricated. The capacitance-voltage ( C- V) measurements show that the flat-band voltage is about -1.1 V with an effective oxide charge of about 7 × 10 10 cm -2 and interface trap density of 3 × 10 11 cm -2 eV -1. At room temperature, the leakage current is about 3 × 10 -9 A/cm 2 under a 2 × 10 6 V/cm electric field. The breakdown field can reach over 16 MV/cm at 1 μA/cm 2 for these SiGe metal-oxide semiconductor (MOS) diodes.

  7. Width determination of SiO2-films in Si-based devices using low-loss EFTEM: image contrast as a function of sample thickness.

    PubMed

    Schaffer, Bernhard; Grogger, Werner; Hofer, Ferdinand

    2003-01-01

    Energy filtering transmission electron microscopy (EFTEM) has become one of the most efficient tools for specimen characterization at nanometer length scales. EFTEM imaging is most often carried out in the core-loss region but image intensity becomes more and more a limiting factor with decreasing feature size. Alternatively, it is possible to record EFTEM images in the low-loss region, where intensities are essentially higher and where in many cases the images contain material specific contrasts. In this paper we investigate the influence of the important parameters on the material contrast between silicon and silicon dioxide, e.g. specimen thickness, specimen orientation, energy-loss and energy selecting slit width. We show that sample thickness plays an important role and present two methods to calculate material contrast as a function of energy-loss and sample thicknesses. The first method uses spectra taken from both materials at different sample thickness by electron energy-loss spectroscopy, the second calculates contrast directly from a series of energy filtered images. From the results we determine the ideal acquisition parameters for the Si/SiO(2) system and demonstrate imaging at sufficient resolution below 2nm with a test sample of thin SiO(2) layers on Si. PMID:12694852

  8. Damage Thresholds and Morphology of the Front- and Back-Irradiated SiO2 Thin Films Containing Gold Nanoparticles as Artificial Absorbing Defects

    SciTech Connect

    Papernov, S.; Schmid, A.W.; Oliver, J.B.; Rigatti, A.L.

    2008-01-30

    Previous ultraviolet-pulsed, laser-damage studies using model thin films with gold nanoparticles as artificial absorbing defects revealed damage morphology in a form of submicrometer-scaled craters. It was also demonstrated that for defects smaller than 20 nm, crater formation is preceded by plasma-ball formation around absorbing defects. In this work an attempt is made to verify symmetry of the plasma ball by conducting film irradiation from the side of the air/film or substrate/film interfaces. In each case, crater-formation thresholds are derived and crater morphology is analyzed by means of atomic force microscopy.

  9. Abrasion-resistant solgel antireflective films with a high laser-induced damage threshold for inertial confinement fusion

    NASA Astrophysics Data System (ADS)

    Xu, Yao; Zhang, Lei; Wu, Dong; Sun, Yu Han; Huang, Zu Xing; Jiang, Xiao Dong; Wei, Xiao Feng; Li, Zhi Hong; Dong, Bao Zhong; Wu, Zhong Hua

    2005-09-01

    To prepare abrasion-resistant antireflective (AR) films for inertial confinement fusion, four solgel routes have been investigated on polysiloxane-modified and polyvinylalcohol- (PVA-) modified SiO2 sols. As confirmed with a transmissive electron microscope, different fractal structure characteristics of the modified SiO2 particles are disclosed by small-angle x-ray scattering technology. And it is these special fractal characteristics that determine the performance of AR films on the level of internal microstructure. A 29Si magic angle spinning and nuclear magnetic resonance study has been successfully applied in explaining the fractal microstructure and its relation to the laser-induced damage threshold (LIDT) of AR films. The films modified by PVA120000 or acetic acid-catalyzed polysiloxane have higher LIDTs than those films modified by PVA16000 or hydrochloride acid-catalyzed polysiloxane. The films from PVA-modified SiO2 sols have a stronger abrasion resistance but lower antireflection than those films from polysiloxane-modified SiO2 sols. In addition, the films from polysiloxane-modified SiO2 sols can possess high transmittance and high LIDT if the polysiloxane synthesis condition is appropriately chosen, but the abrasion resistance is not as good as that from PVA modification. If strong abrasion resistance is necessary, a possible resolution may be to choose a more appropriate hydrophilic polymer than PVA. If not, polysiloxane-modified silica sol can also work when polysiloxane is synthesized under acetic acid catalysis.

  10. Growth and structure of water on SiO2 films on Si investigated byKelvin probe microscopy and in situ X-ray Spectroscopies

    SciTech Connect

    Verdaguer, A.; Weis, C.; Oncins, G.; Ketteler, G.; Bluhm, H.; Salmeron, M.

    2007-06-14

    The growth of water on thin SiO{sub 2} films on Si wafers at vapor pressures between 1.5 and 4 torr and temperatures between -10 and 21 C has been studied in situ using Kelvin Probe Microscopy and X-ray photoemission and absorption spectroscopies. From 0 to 75% relative humidity (RH) water adsorbs forming a uniform film 4-5 layers thick. The surface potential increases in that RH range by about 400 mV and remains constant upon further increase of the RH. Above 75% RH the water film grows rapidly, reaching 6-7 monolayers at around 90% RH and forming a macroscopic drop near 100%. The O K-edge near-edge X-ray absorption spectrum around 75% RH is similar to that of liquid water (imperfect H-bonding coordination) at temperatures above 0 C and ice-like below 0 C.

  11. Effect of power on interface and electrical properties of SiO2 films produced by plasma-enhanced chemical-vapor deposition

    NASA Astrophysics Data System (ADS)

    Landheer, D.; Xu, D.-X.; Tao, Y.; Sproule, G. I.

    1995-02-01

    The effect of power on the electrical and interface properties of silicon dioxide films produced by direct plasma-enhanced chemical-vapor deposition, using nitrous oxide and silane with high helium dilution, has been investigated. Auger depth profiling measurements indicate that while the bulk of the films have no measurable impurities, the interface region contains about 1.6 x 10(exp 15) atoms/sq cm of nitrogen. In contrast to thermal oxides, there is no thick interface layer with a large intrinsic compressive stress. The interface-state densities of the films obtained from capacitance-voltage measurements on metal-oxide-semiconductor diodes increase with increasing plasma power, but these can be removed to some extent by high-temperature annealing at temperatures in the range 800-950 C. The flatband voltage is relatively insensitive to plasma power. Thermal oxide samples have been subjected to the plasma processes and these also show evidence of plasma damage. A thin layer produced at the interface by a separate plasma oxynitridation process is shown to be incapable of protecting the Si/SiO2 interface from the plasma damage produced by subsequent high-power plasma deposition processes. The nature of the interface states is discussed.

  12. Shear strength of metal - SiO2 contacts

    NASA Technical Reports Server (NTRS)

    Pepper, S. V.

    1978-01-01

    The strength of the bond between metals and SiO2 was studied by measuring the static coefficient of friction of metals contacting alpha-quartz in ultrahigh vacuum. It was found that copper with either chemisorbed oxygen, nitrogen, or sulphur exhibited higher contact strength on stoichiometric SiO2 than did clean copper. Since the surface density of states induced by these species on copper is similar, it appears that the strength of the interfacial bond can be related to the density of states on the metal surface.

  13. Shear strength of metal - SiO2 contacts

    NASA Technical Reports Server (NTRS)

    Pepper, S. V.

    1978-01-01

    The strength of the bond between metals and SiO2 is studied by measuring the static coefficient of friction of metals contacting alpha-quartz in ultrahigh vacuum. It was found that copper with either chemisorbed oxygen, nitrogen or sulphur exhibited higher contact strength on stoichiometric SiO2 than did clean copper. Since the surface density of states induced by these species on copper is similar, it appears that the strength of the interfacial bond can be related to the density of states on the metal surface.

  14. Localized corrosion of 316L stainless steel with SiO2-CaO films obtained by means of sol-gel treatment.

    PubMed

    Vallet-Regí, M; Izquierdo-Barba, I; Gil, F J

    2003-11-01

    Sol-gel films on austenitic stainless steel (AISI 316L) polished wafer were prepared from sono-sols obtained from tetraethylorthosilane and hydrated calcium nitrate. However, pitting was observed in different places on the stainless steel surfaces. The corrosion resistance was evaluated by the polarization resistance in simulated body fluid environment at 37 degrees C. The critical current density, the passive current density, the corrosion potential, and the critical pitting potential were studied. The austenitic stainless steel 316L treated presents important electrochemical corrosion and consequently its application as endosseous implants is not possible. PMID:14566812

  15. 3D micro- and nano-machining of hydrogenated amorphous silicon films on SiO2/Si and glass substrates

    NASA Astrophysics Data System (ADS)

    Soleimani-Amiri, S.; Zanganeh, S.; Ramzani, R.; Talei, R.; Mohajerzadeh, S.; Azimi, S.; Sanaee, Z.

    2015-07-01

    We report on the hydrogen-assisted deep reactive ion etching of hydrogenated amorphous silicon (a-Si:H) films deposited using radio-frequency plasma enhanced chemical vapor deposition (RF-PECVD). High aspect-ratio vertical and 3D amorphous silicon features, with the desired control over the shaping of the sidewalls, in micro and nano scales, were fabricated in ordered arrays. The suitable adhesion of amorphous Si film to the underlayer allows one to apply deep micro- and nano-machining to these layers. By means of a second deposition of amorphous silicon on highly curved 3D structures and subsequent etching, the fabrication of amorphous silicon rings is feasible. In addition to photolithography, nanosphere colloidal lithography and electron beam lithography were exploited to realize ultra-small features of amorphous silicon. We have also investigated the optical properties of fabricated hexagonally patterned a-Si nanowire arrays on glass substrates and demonstrated their high potential as active layers for solar cells. This etching process presents an inexpensive method for the formation of highly featured arrays of vertical and 3D amorphous silicon rods on both glass and silicon substrates, suitable for large-area applications.

  16. Highly Reliable Liquid-Phase-Deposited SiO2 with Nitrous Oxide Plasma Post-Treatment for Low-Temperature-Processed Polysilicon Thin Film Transistors

    NASA Astrophysics Data System (ADS)

    Yeh, Ching-Fa; Chen, Darren Chi-Hsiang; Lu, Cheng-Yu; Liu, Chung; Lee, Su-Tseng; Liu, Cheng-Hong; Chen, Tai-Ju

    2002-10-01

    Low-temperature (˜300°C) N2O-plasma post-treatment for liquid-phase-deposited (LPD) gate oxide has been proposed for the first time. This treatment successfully takes the place of conventional furnace annealing in O2 ambient. Results of physicochemical and electrical characteristics show that N2O-plasma post-treated LPD-SiO2 has a high electrical breakdown field and low interface state density. In addition, N2O-plasma treatment also improves the Si-rich phenomenon of LPD-SiO2. From the comparison with pure N2O-plasma oxidation film, LPD-SiO2 with its short re-oxidation time in N2O plasma plays an important role in relieving interfacial stress. Finally, the novel technology is applied to the gate oxide of low-temperature-processed (LTP) polysilicon thin film transistors (poly-Si TFTs). The device performance reveals excellent electrical characteristics, and the reliability shows a satisfactory result, as well as the gate oxide reliability. It is believed that the N2O-plasma post-treatment not only improves the oxide quality, but also effectively passivates the trap states of poly-Si TFTs.

  17. Vacuum ultraviolet thin films. I - Optical constants of BaF2, CaF2, LaF3, MgF2, Al2O3, HfO2, and SiO2 thin films. II - Vacuum ultraviolet all-dielectric narrowband filters

    NASA Technical Reports Server (NTRS)

    Zukic, Muamer; Torr, Douglas G.; Spann, James F.; Torr, Marsha R.

    1990-01-01

    An iteration process matching calculated and measured reflectance and transmittance values in the 120-230 nm VUV region is presently used to ascertain the optical constants of bulk MgF2, as well as films of BaF2, CaF2, LaF3, MgF2, Al2O3, HfO2, and SiO2 deposited on MgF2 substrates. In the second part of this work, a design concept is demonstrated for two filters, employing rapidly changing extinction coefficients, centered at 135 nm for BaF2 and 141 nm for SiO2. These filters are shown to yield excellent narrowband spectral performance in combination with narrowband reflection filters.

  18. Reflectance, Solar Absorptivity, and Thermal Emissivity of SiO(2)-Coated Aluminum.

    PubMed

    Hass, G; Ramsey, J B; Heaney, J B; Triolo, J J

    1969-02-01

    The reflectance, solar absorptivity (alpha), and the total normal and hemispherical emissivity (epsilonNu and epsilon) of evaporated aluminum coated with SiO(2) films of various thicknesses were determined. High vacuum evaporation with an electron gun was used for preparing uv transparent undecomposed films of SiO(2) up to thicknesses of more than 3.5 micro Because of their hardness, chemical stability, and excellent adherence, evaporated SiO(2) films were found to be very suitable as protective layers for aluminum front surface mirrors, especially if high reflectance in the uv is required. alpha of SiO(2)-coated Al was determined to be about 11 % and to be essentially independent of the SiO(2) thickness, whereas epsilonNu and epsilon increased with increasing oxide thickness, and reached values of 0.62 and 0.55, respectively, for a SiO(2) thickness of 3.75 micro. Films of this type are, therefore, suitable as surface layers for controlling the temperature of satellites in orbit. Ultraviolet irradiation in vacuum at one and five times the equivalent solar energy decreased the uv and visible reflectance of SiO(2)-coated Al. The effect of this reflectance decrease on alpha/epsilon and on the temperature of an orbiting satellite is discussed. PMID:20072214

  19. SAW-grade SiO2 for advanced microfluidic devices

    NASA Astrophysics Data System (ADS)

    Winkler, Andreas; Menzel, Siegfried; Schmidt, Hagen

    2009-05-01

    Acoustoelectronic devices based on surface acoustic wave (SAW) technology are primarily used in radio frequency filters, delay lines, duplexers, amplifiers and RFID tags. Thereby, SAW's are excited at the surface of piezoelectric materials (e.g. Quartz, LiTaO3, LiNbO3) by an RF signal applied via interdigital transducers (IDTs)1. Novel SAW applications that emerged recently in the field of microfluidics such as the handling of minimum quantities of fluids or gases2,3 require a fluid compatible design approach, high power durability and long lifetime of the devices. However, conventional SAW devices with finger electrodes arranged on top of the chip surface experience acoustomigration damage4,5 at high power input and/or higher operating temperature leading to failure of the device. Additionally, inappropriate material systems or chip surface topography can limit their performance in microfluidic application. To overcome these limitations the electrodes can be buried in an acoustically suited ("SAW-grade") functional layer which moreover should be adjustable to the specific biotechnological task. Depending on the properties of this layer, it can suppress the acoustomigration impact6 and improve the power durability of the device. Also, a reduction of the thermally-induced frequency shift is possible7. The present paper describes a novel SAW based chip technology approach using a modular concept. Here, the electrodes are buried in surface polished SAW-grade SiO2 fabricated by means of reactive RF magnetron sputtering from a SiO2- target. This approach will be demonstrated for two different metallization systems based on Al or Cu thin films on 128° YX-LiNbO3 substrates. We also show the application of the SiO2-layer with respect to compensation of thermallyinduced frequency shift and bio /chemical surface modification. Investigations were carried out using atomic force microscopy, laser-pulse acoustic measurement, glow-discharge optical emission spectroscopy

  20. Study of O3-TEOS SiO2 Cladding for Silicon Photonics Devices

    NASA Astrophysics Data System (ADS)

    Kinoshita, Keizo; Horikawa, Tsuyoshi; Shimura, Daisuke; Takahashi, Hiroyuki; Mogami, Tohru

    2015-09-01

    Silicon Photonics (SiPh) is a promising technology for large-capacity and wide-band data communications for the distance from millimeter to 100 meters which corresponded well to data center applications. This paper describes about O3-TEOS SiO2 film developments as an upper cladding over Si waveguide core fabricated on silicon-on-insulator wafers. It was compared with a plasma-enhanced chemical-vapor-deposition (PE-CVD) SiO2 film used widely as the cladding material. The O3-TEOS SiO2 showed very high gap-fill characteristic at parallel arrangement of two waveguides. However, its propagation loss was 1.83 dB/cm which is three times larger than that of the conventional PE-CVD SiO2 cladding. Chemical analyses by FT-IR and TDS for these two types of cladding films were carried out to clarify this reason. It was clearly shown that remained water within the O3-TEOS SiO2 cladding could cause the larger propagation loss by O-H stretching absorption. The water exclusion procedure should be developed to apply O3-TEOS SiO2 for the cladding materials. This work was supported by NEDO.

  1. Shock induced reaction in Chicxulub target materials (CaSO4 and SiO2) and their relation to extinctions

    NASA Technical Reports Server (NTRS)

    Chen, Guangqing; Ahrens, Thomas J.

    1993-01-01

    The global platinum element rich layer, the presence of shocked quartz grains (in some cases with stishovite), and the observation of a tektite-rich layer, precisely at the K-T boundary, are the three major arguments for the extinction bolide impact hypothesis of Alvarez et al. Tektites (spherules) from Beloc in Haiti and Mimbral in Mexico received particular interest because of their geological proximity to the Chicxulub impact structure, which is a leading candidate for at least one of the K-T impact craters. Although in most localities the original glass has weathered to clay minerals, some shock-induced glass is found in outcrops and drill cores which is used for Ar-38/Ar-39 dating. The glassy tektites were found to be chemically similar and coeval at 65.0 Ma with Chicxulub melt rock. Two kinds of K-T spherules were discovered: (1) a silic black glass; and (2) a yellow glass, enriched in Ca, Mg, and S. The high sulfur content of the glass and the abundance of anhydrite (CaSO4) in the carbonate-evaporite sequence observed in Drill Holes Y-1 and Y-2 at Chicxulub prompted studies of calcium sulfate devolatization. Further discussion of our experiments is presented.

  2. Light Induced Water Oxidation on Cobalt-Phosphate (Co-Pi) Catalyst Modified Semi-Transparent, Porous SiO2-BiVO4 Electrodes

    SciTech Connect

    Pilli, S. K.; Deutsch, T. G.; Furtak, T. E.; Turner, J. A.; Brown, L. D.; Herring, A. M.

    2012-04-21

    A facile and simple procedure for the synthesis of semi-transparent and porous SiO{sub 2}-BiVO{sub 4} electrodes is reported. The method involves a surfactant assisted metal-organic decomposition at 500 C. An earth abundant oxygen evolution catalyst (OEC), cobalt phosphate (Co-Pi), has been used to modify the SiO{sub 2}-BiVO{sub 4} electrode by electrodeposition (ED) and photoassisted electrodeposition (PED) methods. Modified electrodes by these two methods have been examined for light induced water oxidation and compared to the unmodified SiO{sub 2}-BiVO{sub 4} electrodes by various photoelectrochemical techniques. The PED method was a more effective method of OEC preparation than the ED method as evidenced by an increased photocurrent magnitude during photocurrent-potential (I-V) characterizations. Electrode surfaces catalyzed by PED exhibited a very large cathodic shift (420 mV) in the onset potential for water oxidation. The chopped-light I-V measurements performed at different intervals over 24-hour extended testing under illumination and applied bias conditions show a fair photostability for PED Co-Pi modified SiO{sub 2}-BiVO{sub 4}.

  3. In-situ luminescence monitoring of ion-induced damage evolution in SiO2 and Al2O3

    DOE PAGESBeta

    Crespillo, Miguel L.; Graham, Joseph T.; Zhang, Yanwen; Weber, William J.

    2015-12-17

    Real-time, in-situ ionoluminescence measurements provide information of evolution of emission bands with ion fluence, and thereby establish a correlation between point defect kinetics and phase stability. Using fast light ions (2 MeV H and 3.5 He MeV) and medium mass-high energy ions (8 MeV O, E=0.5 MeV/amu), scintillation materials of a-SiO2, crystalline quartz, and Al2O3 are comparatively investigated at room temperature with the aim of obtaining a further insight on the structural defects induced by ion irradiation and understand the role of electronic energy loss on the damage processes. For more energetic heavy ions, the electronic energy deposition pattern offersmore » higher rates of excitation deeper into the material and allows to evaluate the competing mechanisms between the radiative and non-radiative de-excitation processes. Irradiations with 8 MeV O ions have been selected corresponding to the electronic stopping regime, where the electronic stopping power is dominant, and above the critical amorphization threshold for quartz. Lastly, the usefulness of IBIL and its specific capabilities as a sensitive tool to investigate the material characterization and evaluation of radiation effects are demonstrated.« less

  4. Temperature-Dependent Cathodoluminescence of Disordered SiO2 Layers

    NASA Astrophysics Data System (ADS)

    Jensen, Amberly; Dennison, J. R.; Wilson, Gregory; Dekany, Justin

    2013-03-01

    Optical coatings of disordered thin film SiO2/SiOx dielectric samples on reflective metal substrates exhibited electron-induced luminescence (cathodoluminescence) under electron beam irradiation. These experiments provided measurements of the absolute radiance and emission spectra as functions of incident electron energy, flux and power over a range of sample temperatures (<40 K to >300 K). The overall luminescent intensity increased linearly with increasing power, plateaued, then fell off approximately exponentially. Spectrometer data revealed four spectral bands. The structural defects associated with three of the four bands have been identified. Temperature dependence of the peak intensity and central position differs for the lower and higher energy bands. These results are interpreted with a model of the band structure of highly disordered trapped states within the band gap of SiO2, used to describe the excitation of electrons from the valence band to the conduction band and subsequent relaxation into trapped states. The cathodoluminescence model describes these experimental observations, providing a fundamental basis for understanding the dependence of cathodoluminescence on irradiation time and accumulated charge, incident flux and energy, and sample thickness and temperature. This work was supported by funds from NASA Goddard Space Flight Center, a NASA Space Technology Graduate Research Fellowship, and NRC Senior Research Fellowship at AFRL.

  5. Electronic sputtering of vitreous SiO2: Experimental and modeling results

    NASA Astrophysics Data System (ADS)

    Toulemonde, M.; Assmann, W.; Trautmann, C.

    2016-07-01

    The irradiation of solids with swift heavy ions leads to pronounced surface and bulk effects controlled by the electronic energy loss of the projectiles. In contrast to the formation of ion tracks in bulk materials, the concomitant emission of atoms from the surface is much less investigated. Sputtering experiments with different ions (58Ni, 127I and 197Au) at energies around 1.2 MeV/u were performed on vitreous SiO2 (a-SiO2) in order to quantify the emission rates and compare them with data for crystalline SiO2 quartz. Stoichiometry of the sputtering process was verified by monitoring the thickness decreases of a thin SiO2 film deposited on a Si substrate. Angular distributions of the emitted atoms were measured by collecting sputtered atoms on arc-shaped Cu catcher foils. Subsequent analysis of the number of Si atoms deposited on the catcher foils was quantified by elastic recoil detection analysis providing differential as well as total sputtering yields. Compared to existing data for crystalline SiO2, the total sputtering yields for vitreous SiO2 are by a factor of about five larger. Differences in the sputtering rate and track formation characteristics between amorphous and crystalline SiO2 are discussed within the frame of the inelastic thermal spike model.

  6. Long-pulse laser-induced damage in an optical anti-reflective film: II. Experimental research

    NASA Astrophysics Data System (ADS)

    Li, Changli; Ma, Yao; Wang, Di; Wang, Zhiyang; Zhang, Xihe; Liu, Haiming

    2014-12-01

    In order to verify the result of theoretical analysis about long-pulse flat-topped multi-Gaussian laser-induced damage in an optical anti-reflection film with HfO2/SiO2 composite film coating on a BK7 substrate (BK7:HfO2/SiO2), an experimental system was built, which carried out the experiment and analysis, focusing on the pulse-length 1.0 ms, flat-topped laser-induced damage. The result shows that the thermal effect is the main reason for damage under the long-pulse flat-topped laser. Moreover, the stripping and shedding occur because of the heating stress of the film happening at an early stage of the laser irradiation. However, the crack happens at laser irradiation termination. The correctness of the theoretical analysis results is verified.

  7. The study on SiO2 pattern fabrication using Ge1.5Sn0.5Sb2Te5 as resists.

    PubMed

    Xi, Hongzhu; Liu, Qian; Tian, Ye; Guo, Shengming; Cu, Maoyou; Zhang, Gengmin

    2013-02-01

    Ge1.5Sn0.5Sb2Te5 (GSST) can be easily induced to phase transition from amorphous state to crystalline state by a laser direct writing (LDW) system. The results show that the crystalline phase of GSST is more durable against acid solution corrosion than the amorphous phase. So nano-scale patterns and structures can be formed on the GSST film resists using laser-induced phase change and wet etching. Moreover, reactive ion etching (RIE) technology was applied to transfer these patterns onto the SiO2 substrate. The result shows to the extent that GSST material has thermal resist characteristics with high resolution and well etching selectivity to SiO2 when etched in the CHF3, which is compatibility with the future nanofabricate processing. PMID:23646524

  8. CoCrPt -SiO2 granular-type longitudinal media on Ru underlayer for sputtered tape applications

    NASA Astrophysics Data System (ADS)

    Lee, Hwan-Soo; Zhu, Jian-Gang; Laughlin, David E.

    2008-04-01

    CoCrPt -SiO2 films for use as thin film tape media have been investigated. Bias sputtering and high Ar pressure were utilized to achieve desirable media properties (good in-plane orientation and enhanced grain decoupling) in these media. The in-plane orientation of the bias sputtered CoCrPt -SiO2 magnetic layer was well maintained even at a high content of SiO2 as Ru was used as an underlayer and deposited at high Ar pressure. Films of (10.0) textured CoCrPt -SiO2 on a Ru underlayer showed a large in-plane coercivity of 4000Oe and transmission electron microscopy revealed an average grain size of about 10nm, well decoupled by the oxide. The in-plane coercivity was a strong function of the Ru thickness.

  9. Optical properties of the Al2O3/SiO2 and Al2O3/HfO2/SiO2 antireflective coatings

    NASA Astrophysics Data System (ADS)

    Marszałek, Konstanty; Winkowski, Paweł; Jaglarz, Janusz

    2014-01-01

    Investigations of bilayer and trilayer Al2O3/SiO2 and Al2O3/HfO2/SiO2 antireflective coatings are presented in this paper. The oxide films were deposited on a heated quartz glass by e-gun evaporation in a vacuum of 5 × 10-3 [Pa] in the presence of oxygen. Depositions were performed at three different temperatures of the substrates: 100 °C, 200 °C and 300 °C. The coatings were deposited onto optical quartz glass (Corning HPFS). The thickness and deposition rate were controlled with Inficon XTC/2 thickness measuring system. Deposition rate was equal to 0.6 nm/s for Al2O3, 0.6 nm - 0.8 nm/s for HfO2 and 0.6 nm/s for SiO2. Simulations leading to optimization of the thin film thickness and the experimental results of optical measurements, which were carried out during and after the deposition process, have been presented. The optical thickness values, obtained from the measurements performed during the deposition process were as follows: 78 nm/78 nm for Al2O3/SiO2 and 78 nm/156 nm/78 nm for Al2O3/HfO2/SiO2. The results were then checked by ellipsometric technique. Reflectance of the films depended on the substrate temperature during the deposition process. Starting from 240 nm to the beginning of visible region, the average reflectance of the trilayer system was below 1 % and for the bilayer, minima of the reflectance were equal to 1.6 %, 1.15 % and 0.8 % for deposition temperatures of 100 °C, 200 °C and 300 °C, respectively.

  10. Optical properties of self-assembled TiO2-SiO2 double-layered photonic crystals.

    PubMed

    Oh, Yong Taeg; Koo, Bo Ra; Shin, Dong Chan

    2013-01-01

    The optical properties of self-assembled TiO2/SiO2 double-layered photonic crystals were examined using SiO2 and TiO2 nanopowders. The SiO2 and TiO2 nanopowders were fabricated using the well-known Stöber process, and the double-layered structure was self-assembled by an evaporation method. Self-assembled TiO2 thin film was coated at a 1.2 mm thickness by the evaporation process, and 3 atomic layers of the SiO2 layer was coated onto the TiO2 thin film. The relative reflectance peak intensity of the photonic bandgap in the specimen was 13% before thermal treatment. The peak value was increased by sequential heat-treatments and reached the highest value of 21% at 400 degrees C. PMID:23646797

  11. Mass spectrometric studies of SiO2 deposition in an indirect plasma enhanced LPCVD system

    NASA Technical Reports Server (NTRS)

    Iyer, R.; Lile, D. L.; Mcconica, C. M.

    1993-01-01

    Reaction pathways for the low temperature deposition of SiO2 from silane and indirect plasma-excited oxygen-nitrogen mixtures are proposed based on experimental evidence gained from mass spectrometry in an indirect plasma enhanced chemical vapor deposition chamber. It was observed that about 80-85 percent of the silane was oxidized to byproduct hydrogen and only about 15-20 percent to water. Such conversion levels have led us to interpret that silanol (SiH3OH) could be the precursor for SiO2 film deposition, rather than siloxane /(SiH3)2O/ which has generally been cited in the literature. From mass spectrometry, we have also shown the effects of the plasma, and of mixing small amounts of N2 with the oxygen flow, in increasing the deposition rate of SiO2. Free radical reaction of nitric oxide, synthesized from the reaction of oxygen and nitrogen in the plasma chamber, and an *ncrease in atomic oxygen concentration, are believed to be the reasons for these SiO2 deposition rate increases. Through mass spectrometry we have, in addition, been able to identify products, presumably originating from terminating reactions, among a sequence of chemical reactions proposed for the deposition of SiO2.

  12. Investigation of laser induced damage threshold measurement with single-shot on thin films

    NASA Astrophysics Data System (ADS)

    Liu, Zhichao; Zheng, Yi; Pan, Feng; Lin, Qi; Ma, Ping; Wang, Jian

    2016-09-01

    A method for rapid determination of laser induced damage threshold (LIDT) of optical coatings is proposed and investigated in this paper. By use of this method, the LIDT of thin film can be rapidly obtained by only one shot. The modulation of laser beam profile, which is considered as a negative factor in conventional LIDT test, is utilized in this method. Basing on image processing technique, the damage information could be extracted from the comparison between the damage pattern and beam intensity distribution in the test region. The applicability and repeatability of this testing method has been verified on three type reflectors, HfO2/SiO2, HfO2/Al2O3 and Ta2O5/SiO2. In addition, the experimental results showed that appropriate beam size, laser energy and image compression ratio are the key factors to ensure a high accuracy of LIDT.

  13. Graphene growth at the interface between Ni catalyst layer and SiO2/Si substrate.

    PubMed

    Lee, Jeong-Hoon; Song, Kwan-Woo; Park, Min-Ho; Kim, Hyung-Kyu; Yang, Cheol-Woong

    2011-07-01

    Graphene was synthesized deliberately at the interface between Ni film and SiO2/Si substrate as well as on top surface of Ni film using chemical vapor deposition (CVD) which is suitable for large-scale and low-cost synthesis of graphene. The carbon atom injected at the top surface of Ni film can penetrate and reach to the Ni/SiO2 interface for the formation of graphene. Once we have the graphene in between Ni film and SiO2/Si substrate, the substrate spontaneously provides insulating SiO2 layer and we may easily get graphene/SiO2/Si structure simply by discarding Ni film. This growth of graphene at the interface can exclude graphene transfer step for electronic application. Raman spectroscopy and optical microscopy show that graphene was successfully synthesized at the back of Ni film and the coverage of graphene varies with temperature and time of synthesis. The coverage of graphene at the interface depends on the amount of carbon atoms diffused into the back of Ni film. PMID:22121737

  14. Effects of CO 2 laser conditioning of the antireflection Y 2O 3/SiO 2 coatings at 351 nm

    NASA Astrophysics Data System (ADS)

    Wei, Chaoyang; He, Hongbo; Shao, Jianda; Wang, Tao; Zhang, Dongping; Fan, Zhengxiu

    2005-08-01

    Y 2O 3/SiO 2 coatings were deposited on fused silica by electron beam evaporation. A continuous wave CO 2 laser was used to condition parts of the prepared samples at different scanning speeds in the air. LAMBDA 900 spectrometer was used to investigate the changes of the transmittance and residual reflection spectrum. A Nomarski microscope under dark field was used to examine the changes of the micro defect density. The changes of the surface roughness and the microstructure of the film before and after conditioning were investigated by AFM and X-ray diffraction, respectively. We found that laser-induced damage threshold (LIDT) of the films conditioning at 30 mm/s scanning speed was increased by more than a factor of 3 over the thresholds of the as-deposited films. The conditioning effect was correlated with an irradiation-induced decrease of the defect density and absorption of the films.

  15. Antioxidant and antiradical SiO2 nanoparticles covalently functionalized with gallic acid.

    PubMed

    Deligiannakis, Yiannis; Sotiriou, Georgios A; Pratsinis, Sotiris E

    2012-12-01

    Gallic acid (GA) and its derivatives are natural polyphenolic substances widely used as antioxidants in nutrients, medicine and polymers. Here, nanoantioxidant materials are engineered by covalently grafting GA on SiO(2) nanoparticles (NPs). A proof-of-concept is provided herein, using four types of well-characterized SiO(2) NPs of specific surface area (SSA) 96-352 m(2)/g. All such hybrid SiO(2)-GA NPs had the same surface density of GA molecules (~1 GA per nm(2)). The radical-scavenging capacity (RSC) of the SiO(2)-GA NPs was quantified in comparison with pure GA based on the 2,2-diphenyl-1-picrylhydrazyl (DPPH(•)) radical method, using electron paramagnetic resonance (EPR) and UV-vis spectroscopy. The scavenging of DPPH radicals by these nanoantioxidant SiO(2)-GA NPs showed mixed-phase kinetics: An initial fast-phase (t(1/2) <1 min) corresponding to a H-Atom Transfer (HAT) mechanism, followed by a slow-phase attributed to secondary radical-radical reactions. The slow-reactions resulted in radical-induced NP agglomeration, that was more prominent for high-SSA NPs. After their interaction with DPPH radicals, the nanoantioxidant particles can be reused by simple washing with no impairment of their RSC. PMID:23121088

  16. Interface modification of MoS2/SiO2 leading to conversion of conduction type of MoS2

    NASA Astrophysics Data System (ADS)

    Lin, Yow-Jon; Su, Ting-Hong

    2016-11-01

    Few-layer MoS2 prepared by the chemical vapor deposition method is deposited on SiO2 samples with/without sulfide treatment in order to experimentally study the mechanism of conduction-type conversion in MoS2. The MoS2 thin film deposited on a SiO2 substrate with sulfide treatment shows n-type behavior, whereas the MoS2 thin film deposited on a SiO2 substrate without sulfide treatment exhibits p-type behavior. Experimental identification confirms that n-type conversion is due to a combined effect of the broken Sisbnd O bonds and the formation of Sisbnd S bonds at the SiO2 surface that results in the removal of oxygen dangling bonds and a change in the MoS2sbnd SiO2 interaction.

  17. Undetactable levels of genotoxicity of SiO2 nanoparticles in in vitro and in vivo tests

    PubMed Central

    Kwon, Jee Young; Kim, Hye Lim; Lee, Jong Yun; Ju, Yo Han; Kim, Ji Soo; Kang, Seung Hun; Kim, Yu-Ri; Lee, Jong-Kwon; Jeong, Jayoung; Kim, Meyoung-Kon; Maeng, Eun Ho; Seo, Young Rok

    2014-01-01

    Background Silica dioxide (SiO2) has been used in various industrial products, including paints and coatings, plastics, synthetic rubbers, and adhesives. Several studies have investigated the genotoxic effects of SiO2; however, the results remain controversial due to variations in the evaluation methods applied in determining its physicochemical properties. Thus, well characterized chemicals and standardized methods are needed for better assessment of the genotoxicity of nanoparticles. Methods The genotoxicity of SiO2 was evaluated using two types of well characterized SiO2, ie, 20 nm (−) charge (SiO EN20(−)2) and 100 nm (−) charge (SiO EN100(−)2). Four end point genotoxicity tests, ie, the bacterial mutation assay, in vitro chromosomal aberration test, in vivo comet assay, and in vivo micronucleus test, were conducted following the test guidelines of the Organization for Economic Cooperation and Development (OECD) with application of Good Laboratory Practice. Results No statistically significant differences were found in the bacterial mutation assay, in vitro chromosomal aberration test, in vivo comet assay, and in vivo micronucleus test when tested for induction of genotoxicity in both two types of SiO2 nanoparticles. Conclusion These results suggest that SiO2 nanoparticles, in particular SiO2EN20(−) and SiO2EN100(−), are not genotoxic in both in vitro and in vivo systems under OECD guidelines. Further, the results were generated in accordance with OECD test guidelines, and Good Laboratory Practice application; it can be accepted as reliable information regarding SiO2-induced genotoxicity. PMID:25565835

  18. Reversible control of magnetic domains in a Tb0.3Dy0.7Fe2/Pt/PbZr0.56Ti0.44O3 thin film heterostructure deposited on Pt/TiO2/SiO2/Si substrate

    NASA Astrophysics Data System (ADS)

    More-Chevalier, J.; Ferri, A.; Cibert, C.; Poullain, G.; Desfeux, R.; Bouregba, R.

    2014-06-01

    Tb0.3Dy0.7Fe2/Pt/PbZr0.56Ti0.44O3 (Terfenol-D/Pt/PZT) magnetoelectric (ME) thin films were deposited on Pt/TiO2/SiO2/Si substrate. Ferroelectric and magnetic properties were characterized at room temperature. At zero dc magnetic field and out of mechanical resonance, a variation of the voltage across the ferroelectric film was obtained when a small external ac magnetic field was applied to the device. The corresponding ME voltage coefficient was 1.27 V/cm Oe. On the same sample, local magnetic domain patterns were imaged by magnetic force microscopy. Reversible changes in magnetic domain patterns were observed when a dc electric field of 120 to 360 kV/cm was applied to the ferroelectric layer. These results confirm that both magnetic control of ferroelectric polarization and electric control of magnetization are achievable on ME thin films devices deposited on silicon substrates.

  19. Structural, ferroelectric and optical properties of Bi2VO5.5 thin films deposited on platinized silicon {(100) Pt/TiO2/SiO2/Si} substrates

    NASA Astrophysics Data System (ADS)

    Kumari, N.; Krupanidhi, S. B.; Varma, K. B. R.

    2008-06-01

    Bismuth vanadate (Bi2VO5.5, BVO) thin films have been deposited by a pulsed laser ablation technique on platinized silicon substrates. The surface morphology of the BVO thin films has been studied by atomic force microscopy (AFM). The optical properties of the BVO thin films were investigated using spectroscopic ellipsometric measurements in the 300 820 nm wavelength range. The refractive index (n), extinction coefficient (k) and thickness of the BVO thin films have been obtained by fitting the ellipsometric experimental data in a four-phase model (air/BVOrough/BVO/Pt). The values of the optical constants n and k that were determined through multilayer analysis at 600 nm were 2.31 and 0.056, respectively. For fitting the ellipsometric data and to interpret the optical constants, the unknown dielectric function of the BVO films was constructed using a Lorentz model. The roughness of the films was modeled in the Brugmann effective medium approximation and the results were compared with the AFM observations.

  20. Contrast mechanism due to interface trapped charges for a buried SiO2 microstructure in scanning electron microscopy.

    PubMed

    Zhang, Hai-Bo; Li, Wei-Qin; Wu, Dan-Wei

    2009-01-01

    We clarify the scanning electron microscopic contrast mechanism for imaging a buried SiO(2) trench microstructure with interface trapped charges by simulating both electron scattering and transport. Here, the interface trapped charges make the SiO(2) film more negatively charged and increase excess holes in the space charge distribution of the electron scattering region. The generated positive surface electric field thus redistributes some emitted secondary electrons and results in the dark contrast. This contrast mechanism is validated by comparing with experiments, and it may also provide an interesting approach for imaging and detecting deep interface trapped charges in insulating films. PMID:19029106

  1. Y1Ba2Cu3O(6+delta) growth on thin Y-enhanced SiO2 buffer layers on silicon

    NASA Technical Reports Server (NTRS)

    Robin, T.; Mesarwi, A.; Wu, N. J.; Fan, W. C.; Espoir, L.; Ignatiev, A.; Sega, R.

    1991-01-01

    SiO2 buffer layers as thin as 2 nm have been developed for use in the growth of Y1Ba2Cu3O(6+delta) thin films on silicon substrates. The SiO2 layers are formed through Y enhancement of silicon oxidation, and are highly stoichiometric. Y1Ba2Cu3O(6+delta) film growth on silicon with thin buffer layers has shown c orientation and Tc0 = 78 K.

  2. Local diffusion induced roughening in cobalt phthalocyanine thin film growth.

    PubMed

    Gedda, Murali; Subbarao, Nimmakayala V V; Goswami, Dipak K

    2014-07-29

    We have studied the kinetic roughening in the growth of cobalt phthalocyanine (CoPc) thin films grown on SiO2/Si(001) surfaces as a function of the deposition time and the growth temperature using atomic force microscopy (AFM). We have observed that the growth exhibits the formation of irregular islands, which grow laterally as well as vertically with coverage of CoPc molecules, resulting rough film formation. Our analysis further disclosed that such formation is due to an instability in the growth induced by local diffusion of the molecules following an anomalous scaling behavior. The instability relates the (ln(t))(1/2), with t as deposition time, dependence of the local surface slope as described in nonequilibrium film growth. The roughening has been characterized by calculating different scaling exponents α, β, and 1/z determined from the height fluctuations obtained from AFM images. We obtained an average roughness exponent α = 0.78 ± 0.04. The interface width (W) increases following a power law as W ∼ t(β), with growth exponent β = 0.37 ± 0.05 and lateral correlation length (ξ) grows as ξ ∼ t(1/z) with dynamic exponent 1/z = 0.23 ± 0.06. The exponents revealed that the growth belongs to a different class of universality. PMID:24992503

  3. Studies on TiO2/SiO2 and Pd/TiO2/SiO2 Catalysts in Photoreduction of CO2 with H2O to Methanol

    NASA Astrophysics Data System (ADS)

    Zbudniewek, K.; Góralski, J.; Rynkowski, J.

    2012-12-01

    The development of industry induced a massive increase in the emission of carbon dioxide into the atmosphere. A large amount of CO2 and its general availability causes that it could be a cheap reactant in a reaction that runs in a way similar to photosynthesis in plants. Pure TiO2 and metal doped TiO2 are the most studied semiconductor catalysts for photoreduction of CO2. The TiO2/SiO2 and Pd/TiO2/SiO2 catalysts were prepared and studied by temperature-programmed desorption, X-ray diffraction analysis, SEM-EDS, temperature-programmed reduction and then used for the methanol synthesis. The photoactivity of Pd/TiO2/SiO2 catalysts in the reduction of CO2 with H2O was tested at room temperature using photoreactor equipped with 16 lamps. The wavelength was characteristic of near ultraviolet. Post-reaction products were identified with gas chromatograph equipped with the flame ionization detector. Pd doping made the catalysts photoactive and the photoactivity of catalysts was changing as follows: 1%Pd/5%TiO2/SiO2 > 1% Pd/10% TiO2/SiO2 > 1% Pd/15% TiO2/SiO2. Optimum ultraviolet radiation time in the photoreduction of CO2 to methanol was 7 h. An addition of Pd does not change the surface of the carrier.

  4. Fabrication of high performance thin-film transistors via pressure-induced nucleation

    PubMed Central

    Kang, Myung-Koo; Kim, Si Joon; Kim, Hyun Jae

    2014-01-01

    We report a method to improve the performance of polycrystalline Si (poly-Si) thin-film transistors (TFTs) via pressure-induced nucleation (PIN). During the PIN process, spatial variation in the local solidification temperature occurs because of a non-uniform pressure distribution during laser irradiation of the amorphous Si layer, which is capped with an SiO2 layer. This leads to a four-fold increase in the grain size of the poly-Si thin-films formed using the PIN process, compared with those formed using conventional excimer laser annealing. We find that thin films with optimal electrical properties can be achieved with a reduction in the number of laser irradiations from 20 to 6, as well as the preservation of the interface between the poly-Si and the SiO2 gate insulator. This interface preservation becomes possible to remove the cleaning process prior to gate insulator deposition, and we report devices with a field-effect mobility greater than 160 cm2/Vs. PMID:25358809

  5. Study of the kinetics and mechanism of the thermal nitridation of SiO2

    NASA Technical Reports Server (NTRS)

    Vasquez, R. P.; Madhukar, A.; Grunthaner, F. J.; Naiman, M. L.

    1985-01-01

    X-ray photoelectron spectroscopy (XPS) has been used to study the nitridation time and temperature dependence of the nitrogen distribution in thermally nitrided SiO2 films. The XPS data show that the maximum nitrogen concentration near the (SiO(x)N(y)/Si interface is initially at the interface, but moves 20-25 A away from the interface with increasing nitridation time. Computer modeling of the kinetic processes involved is carried out and reveals a mechanism in which diffusing species, initially consisting primarily of nitrogen, react with the substrate, followed by formation of the oxygen-rich oxynitride due to reaction of the diffusing oxygen displaced by the slower nitridation of the SiO2. The data are consistent with this mechanism provided the influence of the interfacial strain on the nitridation and oxidation kinetics is explicitly accounted for.

  6. Space electric field concentrated effect for Zr:SiO2 RRAM devices using porous SiO2 buffer layer

    PubMed Central

    2013-01-01

    To improve the operation current lowing of the Zr:SiO2 RRAM devices, a space electric field concentrated effect established by the porous SiO2 buffer layer was investigated and found in this study. The resistive switching properties of the low-resistance state (LRS) and high-resistance state (HRS) in resistive random access memory (RRAM) devices for the single-layer Zr:SiO2 and bilayer Zr:SiO2/porous SiO2 thin films were analyzed and discussed. In addition, the original space charge limited current (SCLC) conduction mechanism in LRS and HRS of the RRAM devices using bilayer Zr:SiO2/porous SiO2 thin films was found. Finally, a space electric field concentrated effect in the bilayer Zr:SiO2/porous SiO2 RRAM devices was also explained and verified by the COMSOL Multiphysics simulation model. PMID:24330524

  7. CMOS-Compatible Top-Down Fabrication of Periodic SiO2 Nanostructures using a Single Mask.

    PubMed

    Meng, Lingkuan; Gao, Jianfeng; He, Xiaobin; Li, Junjie; Wei, Yayi; Yan, Jiang

    2015-12-01

    We propose a CMOS-compatible top-down fabrication technique of highly-ordered and periodic SiO2 nanostructures using a single amorphous silicon (α-Si) mask layer. The α-Si mask pattern is precisely transferred into the underlying SiO2 substrate material with a high fidelity by a novel top-down fabrication. It is the first time for α-Si film used as an etch mask to fabricate SiO2 nanostructures including nanoline, nanotrench, and nanohole arrays. It is observed that the α-Si mask can significantly reduce the pattern edge roughness and achieve highly uniform and smooth sidewalls. This behavior may be attributed to the presence of high concentration of dangling bonds in α-Si mask surface. By controlling the process condition, it is possible to achieve a desired vertical etched profile with a controlled size. Our results demonstrate that SiO2 pattern as small as sub-20 nm may be achievable. The obtained SiO2 pattern can be further used as a nanotemplate to produce periodic or more complex silicon nanostructures. Moreover, this novel top-down approach is a potentially universal method that is fully compatible with the currently existing Si-based CMOS technologies. It offers a greater flexibility for the fabrication of various nanoscale devices in a simple and efficient way. PMID:26306538

  8. A kinetic model for the thermal nitridation of SiO2/Si

    NASA Technical Reports Server (NTRS)

    Vasquez, R. P.; Madhukar, A.

    1986-01-01

    To explain the observed nitrogen distributions in thermally nitridated SiO2 films, a kinetic model is proposed in which the nitridation process is simulated, using the first-order chemical kinetics and Arrhenius dependence of the diffusion and reaction rates on temperature. The calculations show that initially, as the substrate reacts with diffusing nitrogen, a nitrogen-rich oxynitride forms at the SiO2-Si interface, while at nitridation temperatures above 1000 C, an oxygen-rich oxynitride subsequently forms at the interface, due to reaction of the substrate with an increasingly concentrated oxygen displaced by the slower nitridation of the SiO2. This sequence of events results in a nitrogen distribution in which the peak of the interfacial nitrogen concentration occurs away from the interface. The results are compared with the observed nitrogen distribution. The calculated results have correctly predicted the positions of the interfacial nitrogen peaks at the temperatures of 800, 1000, and 1150 C. To account for the observed width of the interfacial nitrogen distribution, it was found necessary to include in the simulations the effect of interfacial strain.

  9. XPS study of interface formation of CVD SiO2 on InSb

    NASA Astrophysics Data System (ADS)

    Vasquez, R. P.; Grunthaner, F. J.

    1981-10-01

    The interfacial chemistry of CVD SiO2 films deposited on thin native oxides grown on InSb substrates is examined using X-ray photoemission spectroscopy (XPS) and a relatively benign chemical etching technique for depth profiling. An intensity analysis of XPS spectra is used to derive the compositional structure of the interfaces obtained in the SiO2/native oxide/InSb system. Peak positions in these spectra are used to follow the change in substrate surface potential during the etch sequence, and to establish the chemical nature of the species formed during deposition and subsequent processing. Reaction of the substrate with oxygen resulted in an In-rich native oxide and 1-2 monolayers of excess elemental Sb at the native-oxide/substrate interface, incompletely oxidized silane reduced the native oxide, leaving less than 1 monolayer of elemental In at the SiO2/native oxide interface. Etch removal of this thin In-rich layer leads to a change in the substrate surface potential of 0.06 eV, corresponding to a net increase in positive charge. The results are consistent with simple thermodynamic considerations; they are also compared to previously reported studies of deposited dielectrics on III-V compound semiconductors.

  10. Application of mesoporous SiO2 layer as an insulating layer in high performance hole transport material free CH3NH3PbI3 perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Cheng, Nian; Liu, Pei; Bai, Sihang; Yu, Zhenhua; Liu, Wei; Guo, Shi-Shang; Zhao, Xing-Zhong

    2016-07-01

    A mesoporous SiO2 layer is successfully introduced into the hole transport material free perovskite solar cells by spin-coating a SiO2 paste onto the TiO2 scaffold layer. This SiO2 layer can act as an insulating layer and effectively inhibit the charge recombination between the TiO2 layer and carbon electrode. The variation of power conversion efficiencies with the thickness of SiO2 layer is studied here. Under optimized SiO2 thickness, perovskite solar cell fabricated on the TiO2/SiO2 film shows a superior power conversion efficiency of ∼12% and exhibits excellent long time stability for 30 days.

  11. Dilute magnetic semiconductors based on wide bandgap SiO 2 with and without transition metal elements

    NASA Astrophysics Data System (ADS)

    Dinh, Van An; Sato, Kazunori; Katayama-Yoshida, Hiroshi

    2005-10-01

    Material designs based on the first principle calculations of electronic structures are proposed for α-quartz SiO 2-based dilute magnetic semiconductors. The incorporation of transition metals (TMs) into Si sites and of the non-TM atoms into O sites are treated for various concentrations. At temperatures higher than room temperature, most of the TM-doped SiO 2 have no magnetism, yet Si 1- xMn xO 2 might achieve the ferromagnetism. The substitution of O by non-TM atoms as C or N also induces the magnetism in the host. However, while the N's substitution induces the ferromagnetism, C's substitution causes an anti-ferromagnetic behavior in the host material SiO 2.

  12. Highly transparent and efficient counter electrode using SiO2/PEDOT-PSS composite for bifacial dye-sensitized solar cells.

    PubMed

    Song, Dandan; Li, Meicheng; Li, Yingfeng; Zhao, Xing; Jiang, Bing; Jiang, Yongjian

    2014-05-28

    A highly transparent and efficient counter electrode was facilely fabricated using SiO2/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) inorganic/organic composite and used in bifacial dye-sensitized solar cells (DSCs). The optical properties of SiO2/PEDOT-PSS electrode can be tailored by the blending amount of SiO2 and film thickness, and the incorporation of SiO2 in PEDOT-PSS provides better transmission in the long wavelength range. Meanwhile, the SiO2/PEDOT-PSS counter electrode shows a better electrochemical catalytic activity than PEDOT-PSS electrode for triiodide reduction, and the role of SiO2 in the catalytic process is investigated. The bifacial DSC with SiO2/PEDOT-PSS counter electrode achieves a high power conversion efficiency (PCE) of 4.61% under rear-side irradiation, which is about 83% of that obtained under front-side irradiation. Furthermore, the PCE of bifacial DSC can be significantly increased by adding a reflector to achieve bifacial irradiation, which is 39% higher than that under conventional front-side irradiation. PMID:24802383

  13. Formation of nucleoplasmic protein aggregates impairs nuclear function in response to SiO2 nanoparticles.

    PubMed

    Chen, Min; von Mikecz, Anna

    2005-04-15

    Despite of their exponentially growing use, little is known about cell biological effects of nanoparticles. Here, we report uptake of silica (SiO(2)) nanoparticles to the cell nucleus where they induce aberrant clusters of topoisomerase I (topo I) in the nucleoplasm that additionally contain signature proteins of nuclear domains, and protein aggregation such as ubiquitin, proteasomes, cellular glutamine repeat (polyQ) proteins, and huntingtin. Formation of intranuclear protein aggregates (1) inhibits replication, transcription, and cell proliferation; (2) does not significantly alter proteasomal activity or cell viability; and (3) is reversible by Congo red and trehalose. Since SiO(2) nanoparticles trigger a subnuclear pathology resembling the one occurring in expanded polyglutamine neurodegenerative disorders, we suggest that integrity of the functional architecture of the cell nucleus should be used as a read out for cytotoxicity and considered in the development of safe nanotechnology. PMID:15777787

  14. Shock temperatures of SiO2 and their geophysical implications

    NASA Technical Reports Server (NTRS)

    Lyzenga, G. A.; Ahrens, T. J.; Mitchell, A. C.

    1983-01-01

    High pressure shock state temperatures of SiO2 were measured in specimens of single crystal alpha-quartz and fused quartz. Projectile impact and pyrometry techniques were employed to impart pressures in the 60-140 GPa range. Shock-induced phase transformations were observed near 70 and 50 GPa along the alpha- and fused-quartz Hugoniots. It is suggested that the transformation consists of melting of the shock-synthesized stishovite, with melting delayed by the superheating of the crystalline phase. Details of the stishovite-liquid phase boundaries have been determined, including stishovite melting at 4500 K under 70 GPa, with the melting accompanied by a relative volume change of about 2.7% and a latent heat of fusion of about 2.4 MJ/kg. At 100 GPa, an approximate limit of 3500 K for the melting of SiO2 is indicated for solid mantle mineral assemblages, such as the earth's mantle

  15. Effects of antimony (Sb) on electron trapping near SiO2/4H-SiC interfaces

    NASA Astrophysics Data System (ADS)

    Mooney, P. M.; Jiang, Zenan; Basile, A. F.; Zheng, Yongju; Dhar, Sarit

    2016-07-01

    To investigate the mechanism by which Sb at the SiO2/SiC interface improves the channel mobility of 4H-SiC MOSFETs, 1 MHz capacitance measurements and constant capacitance deep level transient spectroscopy (CCDLTS) measurements were performed on Sb-implanted 4H-SiC MOS capacitors. The measurements reveal a significant concentration of Sb donors near the SiO2/SiC interface. Two Sb donor related CCDLTS peaks corresponding to shallow energy levels in SiC were observed close to the SiO2/SiC interface. Furthermore, CCDLTS measurements show that the same type of near-interface traps found in conventional dry oxide or NO-annealed capacitors are present in the Sb implanted samples. These are O1 traps, suggested to be carbon dimers substituted for O dimers in SiO2, and O2 traps, suggested to be interstitial Si in SiO2. However, electron trapping is reduced by a factor of ˜2 in Sb-implanted samples compared with samples with no Sb, primarily at energy levels within 0.2 eV of the SiC conduction band edge. This trap passivation effect is relatively small compared with the Sb-induced counter-doping effect on the MOSFET channel surface, which results in improved channel transport.

  16. Crystallisation of Ge nanoclusters in SiO 2 caused by electron irradiation in TEM

    NASA Astrophysics Data System (ADS)

    Klimenkov, M.; Matz, W.; Nepijko, S. A.; Lehmann, M.

    2001-07-01

    Ge nanoparticles fabricated by ion implantation technique in SiO 2 thin film crystallise after irradiation with a high-energy electron beam. The crystallisation process depends on the irradiation fluence and flux. Irradiation with a fluence above 6×10 3 C/ cm2 results in cluster growth and above 4×10 4 C/ cm2 in crystallisation. An irradiation with flux below 150 A/cm 2 leads to the crystallisation of Ge nanoparticles in the form of single crystals. For irradiation flux above this value the formation of twinned and multiply twinned particles (MTP) was observed.

  17. Control of resputtering in biased CoCrPt -SiO2 media to enhance grain decoupling and grain size distribution

    NASA Astrophysics Data System (ADS)

    Lee, Hwan-Soo; Guo, Vickie W.; Zhu, Jian-Gang; Laughlin, David E.

    2008-04-01

    A CoCrPt -SiO2 magnetic layer was investigated as functions of argon pressure and substrate bias voltage. Use of these two parameters provided fine tuning of the average kinetic energy of incoming Ar +, which causes resputtering and, consequently, influences adatom mobility during film growth. Biasing and high Ar pressure resulted in a significant improvement in grain decoupling and grain size distribution in the films. Furthermore, resputtering of the metal and oxide species from the growing CoCrPt -SiO2 film was interpreted in terms of the surface adhesion energy of the species on the metal Ru underlayer.

  18. Devitrification and delayed crazing of SiO2 on single-crystal silicon and chemically vapor-deposited silicon nitride

    NASA Technical Reports Server (NTRS)

    Choi, Doo Jin; Scott, William D.

    1987-01-01

    The linear growth rate of cristobalite was measured in thin SiO2 films on silicon and chemically vapor-deposited silicon nitride. The presence of trace impurities from alumina furnace tubes greatly increased the crystal growth rate. Under clean conditions, the growth rate was still 1 order-of-magnitude greater than that for internally nucleated crystals in bulk silica. Crystallized films cracked and lifted from the surface after exposure to atmospheric water vapor. The crystallization and subsequent crazing and lifting of protective SiO2 films on silicon nitride should be considered in long-term applications.

  19. Intensity analysis of XPS spectra to determine oxide uniformity - Application to SiO2/Si interfaces

    NASA Technical Reports Server (NTRS)

    Vasquez, R. P.; Grunthaner, F. J.

    1980-01-01

    A simple method of determining oxide uniformity is derived which requires no knowlege of film thickness, escape depth, or film composition. The method involves only the measurement of oxide and substrate intensities and is illustrated by analysis of XPS spectral data for thin SiO2 films grown both thermally and by low-temperature chemical vapor deposition on monocrystalline Si. A region 20-30 A thick is found near the SiO2/Si interface on thermally oxidized samples which has an inelastic mean free path 35% less than that found in the bulk oxide. This is interpreted as being due to lattice mismatch resulting in a strained region which is structurally, but not stoichiometrically, distinct from the bulk oxide.

  20. Local atomic and electronic structure of oxide/GaAs and SiO2/Si interfaces using high-resolution XPS

    NASA Technical Reports Server (NTRS)

    Grunthaner, F. J.; Grunthaner, P. J.; Vasquez, R. P.; Lewis, B. F.; Maserjian, J.; Madhukar, A.

    1979-01-01

    The chemical structures of thin SiO2 films, thin native oxides of GaAs (20-30 A), and the respective oxide-semiconductor interfaces, have been investigated using high-resolution X-ray photoelectron spectroscopy. Depth profiles of these structures have been obtained using argon ion bombardment and wet chemical etching techniques. The chemical destruction induced by the ion profiling method is shown by direct comparison of these methods for identical samples. Fourier transform data-reduction methods based on linear prediction with maximum entropy constraints are used to analyze the discrete structure in oxides and substrates. This discrete structure is interpreted by means of a structure-induced charge-transfer model.

  1. Behaviour of Copper In Annealed Cu/Sio2/Si Systems For On-Chip Interconnections

    NASA Astrophysics Data System (ADS)

    Htwe, Thant Zin; Latt, Khin Maung

    2010-01-01

    The electrical and structural properties of thin copper films attract increasing attention nowadays because of the use for on-chip interconnections. The main advantages of copper are the excellent conductivity and the relatively high stability against electro migration damaging. Interdiffusion at the copper/silicon interface can be a remarkable drawback of the interconnection quality even at room temperature which leads to the use of barrier layers between copper and silicon in technical applications. Often, thermal annealing of the as-deposited copper films is required to ensure proper process integration. In the present paper, Copper thin films of thickness 100 nm are deposited on SiO2/Si by ionized metal plasma deposition method. Then samples are annealed at different temperatures under high vacuum condition. The behavior of copper and the mechanism of compound formation studied at different temperatures, using scanning electron microscopy SEM, X-ray diffraction XRD and four point probe method. Diffusion of Cu into SiO2/Si layer start at 550° C and form CuxSiy. Oxidation of Cu is also take place at high temperature annealing.

  2. Scalable flame synthesis of SiO2 nanowires: dynamics of growth.

    PubMed

    Tricoli, Antonio; Righettoni, Marco; Krumeich, Frank; Stark, Wendelin J; Pratsinis, Sotiris E

    2010-11-19

    Silica nanowire arrays were grown directly onto plain glass substrates by scalable flame spray pyrolysis of organometallic solutions (hexamethyldisiloxane or tetraethyl orthosilicate). The silicon dioxide films consisted of a network of interwoven nanowires from a few to several hundred nanometres long (depending on the process conditions) and about 20 nm in diameter, as determined by scanning electron microscopy. These films were formed rapidly (within 10-20 s) at high growth rates (ca 11-30 nm s(-1)) by chemical vapour deposition (surface growth) at ambient conditions on the glass substrate as determined by thermophoretic sampling of the flame aerosol and microscopy. In contrast, on high purity quartz nearly no nanowires were grown while on steel substrates porous SiO(2) films were formed. Functionalization with perfluorooctyl triethoxysilane converted the nanowire surface from super-hydrophilic to hydrophobic. Additionally, their hermetic coating by thin carbon layers was demonstrated also revealing their potential as substrates for synthesis of other functional 1D composite structures. This approach is a significant step towards large scale synthesis of SiO(2) nanowires facilitating their utilization in several applications. PMID:20972311

  3. Scalable flame synthesis of SiO2 nanowires: dynamics of growth

    PubMed Central

    Tricoli, Antonio; Righettoni, Marco; Krumeich, Frank; Stark, Wendelin J; Pratsinis, Sotiris E

    2013-01-01

    Silica nanowire arrays were grown directly onto plain glass substrates by scalable flame spray pyrolysis of organometallic solutions (hexamethyldisiloxane or tetraethyl orthosilicate). The silicon dioxide films consisted of a network of interwoven nanowires from a few to several hundred nanometres long (depending on the process conditions) and about 20 nm in diameter, as determined by scanning electron microscopy. These films were formed rapidly (within 10–20 s) at high growth rates (ca 11–30 nm s−1) by chemical vapour deposition (surface growth) at ambient conditions on the glass substrate as determined by thermophoretic sampling of the flame aerosol and microscopy. In contrast, on high purity quartz nearly no nanowires were grown while on steel substrates porous SiO2 films were formed. Functionalization with perfluorooctyl triethoxysilane converted the nanowire surface from super-hydrophilic to hydrophobic. Additionally, their hermetic coating by thin carbon layers was demonstrated also revealing their potential as substrates for synthesis of other functional 1D composite structures. This approach is a significant step towards large scale synthesis of SiO2 nanowires facilitating their utilization in several applications. PMID:20972311

  4. Durable solgel antireflective films with high laser-induced damage thresholds for inertial confinement fusion

    NASA Astrophysics Data System (ADS)

    Xu, Yao; Zhang, Lei; Wu, Dong; Sun, Yu Han; Huang, Zu Xing; Jiang, Xiao Dong; Wei, Xiao Feng; Li, Zhi Hong; Dong, Bao Zhong; Wu, Zhong Hua

    2005-04-01

    We tested the use of two hydrophobic methyl-substituted silane precursors, methyltriethoxysilane and dimethyldiethoxysilane, to synthesize methyl-modified silica sols by a two-step method and a cohydrolysis method to produce durable antireflective films with high laser-induced-damage thresholds (LIDTs). Using small-angle x-ray scattering technology, we obtained details of the microstructure of clusters in sol and found various double fractal structural characteristics in the methyl-modified silica clusters; our findings were confirmed by transmission-electron micrographs. Through a 29Si magic-angle spin nuclear magnetic resonance study of the corresponding xerogels, we determined the double-fractal microstructure, which we then related to the LIDTs of AR films. The distribution configuration of methyls in clusters determined the double-fractal microstructure of clusters and then the LIDTs of AR films. The LIDTs of films produced by the cohydrolysis method (the highest was 38 J/cm2 for 1-ns, 1064-nm laser action) were much higher than those from the two-step method because of the loose netlike clusters in the former configuration. During the 220-day aging, the transmittance of hydrophobic AR film decreased ~0.2%. So it is practicable to prepare durable AR films with higher LIDTs than those of normal AR SiO2 films only by introducing hydrophobic methyls into a Si-O-Si matrix of clusters if an appropriate hydrophobic precursor is chosen.

  5. Microstructural modifications induced by rapid thermal annealing in plasma deposited SiOxNyHz films

    NASA Astrophysics Data System (ADS)

    del Prado, A.; San Andrés, E.; Mártil, I.; González-Díaz, G.; Bravo, D.; López, F. J.; Fernández, M.; Martínez, F. L.

    2003-07-01

    The effect of rapid thermal annealing (RTA) processes on the structural properties of SiOxNyHz films was investigated. The samples were deposited by the electron cyclotron resonance plasma method, using SiH4, O2 and N2 as precursor gases. For SiOxNyHz films with composition close to that of SiO2, which have a very low H content, RTA induces thermal relaxation of the lattice and improvement of the structural order. For films of intermediate composition and of compositions close to SiNyHz, the main effect of RTA is the release of H at high temperatures (T>700 °C). This H release is more significant in films containing both Si-H and N-H bonds, due to cooperative reactions between both kinds of bonds. In these films the degradation of structural order associated to H release prevails over thermal relaxation, while in those films with only N-H bonds, thermal relaxation predominates. For annealing temperatures in the 500-700 °C range, the passivation of dangling bonds by the nonbonded H in the films and the transition from the paramagnetic state to the diamagnetic state of the K center result in a decrease of the density of paramagnetic defects. The H release observed at high annealing temperatures is accompanied by an increase of density of paramagnetic defects.

  6. Dissolution Kinetics of SiO2 into CaO-Fe2O3-SiO2 Slag

    NASA Astrophysics Data System (ADS)

    Yu, Bin; Lv, Xuewei; Xiang, Shenglin; Xu, Jian

    2016-06-01

    High-basicity sinter is the predominant Fe-bearing material used in blast furnace process in East Asia. The dissolution of SiO2 into molten calcium ferrite influences the assimilation process. In this study, a rotating cylinder method was used to explore the dissolution kinetics of SiO2 into CaO-Fe2O3-SiO2 slag. The influencing factors, including temperature, rotating time and speed, and initial composition of the slag, were considered. Results showed that the dissolution rate increased with increasing rotation speed and temperature, whereas the increase in ω(SiO2) or ω(Fe2O3)/ ω(CaO) ratio in the initial slag composition decreased the dissolution rate. The diffusion coefficient and activation energy of SiO2 during the dissolution process ranged from 2.09 × 10-6 to 6.40 × 10-6 cm2 s-1 and 106.62 to 248.20 kJ mol-1, respectively. Concentration difference between the boundary layer and bulk phase was the primary driving force of the dissolution process; however, this process was also influenced by the slag viscosity and ion diffusivity.

  7. Electrochemically controlled transport of lithium through ultrathin SiO2

    NASA Astrophysics Data System (ADS)

    Ariel, Nava; Ceder, Gerbrand; Sadoway, Donald R.; Fitzgerald, Eugene A.

    2005-07-01

    Monolithically integrating the energy supply unit on a silicon integrated circuit (IC) requires the development of a thin-film solid-state battery compatible with silicon IC fabrication methods, materials, and performance. We have envisioned materials that can be processed in a silicon fabrication environment, thus bringing local stored energy to silicon ICs. By incorporating the material directly onto the silicon wafer, the economic parallelism that silicon complementary metal-oxide-semiconductor (CMOS) technology has enjoyed can be brought to power incorporation in each IC on a processed wafer. It is natural to look first towards silicon CMOS materials, and ask which materials need enhancement, which need replacement, and which can be used "as is." In this study, we begin by using two existing CMOS materials and one unconventional material for the construction of a source of electric power. We have explored the use of thermally grown silicon dioxide (SiO2) as thin as 9nm acting as an electrolyte material candidate in a solid-state power cell integrated on silicon. Other components of the thin-film cell consisted of rf-sputtered lithium cobalt oxide (LiCoO2) as the cathode and highly doped n-type polycrystalline silicon (polysilicon) grown by low-pressure chemical-vapor deposition as the anode. All structures were fabricated using conventional microelectronics fabrication technology. The charge and discharge behaviors of the LiCoO2/SiO2/polysilicon cells were studied. On the basis of the impedance measurements an equivalent circuit model of an ultrathin cell was inferred, and its microstructure was characterized by electron microscopy imaging. In spite of its high series resistance (˜4×107Ω ), we have shown that an ultrathin layer of an as-deposited Li-free SiO2 is an interesting candidate for an electrolyte or controllable barrier layer in lithium-ion-based devices.

  8. Enhanced photoluminescence from CdS with SiO2 nanopillar arrays

    PubMed Central

    Li, Wei; Wang, Shaolei; He, Sufeng; Wang, Jing; Guo, Yanyan; Guo, Yufeng

    2015-01-01

    In this paper, the enhanced photoluminescence from CdS thin film with SiO2 nanopillar array (NPA) was demonstrated. The CdS was prepared using chemical bath deposition in a solution bath containing CdSO4, SC(NH2)2, and NH4OH. The SiO2 NPA was fabricated by the nanosphere lithography (NSL) techniques. The nanopillar is about 50 nm in diameter, and the height is 150 nm. As a result, the sample with NPA shows an obvious improvement of photoluminescence (PL), compared with the one without NPA. In addition, we also observed that the PL intensity is increased ~5 times if the active layer is deposited on the nanopillar arrays and covered by a thin metal film of Al. It is noteworthy that the enhancement of photoluminescence could be attributed to the roughness of the surface, the 2D photonic band gap (PBG) effect and the surface plasmon resonance (SPR) effects. PMID:26077552

  9. Sn Spheres Embedded in a SiO2 Matrix: Synthesis and Potential Application As Self-Destructing Materials.

    PubMed

    Hien, Vu Xuan; Heo, Young-Woo

    2016-08-24

    We introduce a simple process for the fabrication of SiO2 films embedded with β-Sn-rich nano/microspheres. Sn spheres with maximum and minimum sizes of 10 μm (near the SiO2 surface) and 5 nm (at the Si/SiO2 interface) were grown within a 0.7-5.7 μm-thick SiO2 layer by evaporating SnO powders onto an Si (100) substrate for 1-600 min at 600-900 °C and 0.001-5.0 Torr. A possible growth mechanism of these materials is discussed. The current-voltage characteristics of the as-fabricated samples were investigated to identify potential applications. During these tests, small flashes of light and the presence of damaged areas were observed at the oxide surfaces of the samples using an optical camera and a field emission scanning electron microscope, respectively. The electrical breakdown and shutdown of the devices observed in the current-voltage curves were attributed to the destruction of the SiO2 surface. In addition, the current-time responses show that the size of the damaged regions can be controlled by the voltage and duration of the applied stress, and are independent of the size and shape of the electrodes. The present materials thus possess great potential for applications in self-destructing devices. PMID:27463945

  10. Structural stability of Cu nanocrystals in SiO 2 exposed to high-energy ion irradiation

    NASA Astrophysics Data System (ADS)

    Johannessen, B.; Kluth, P.; Glover, C. J.; Kluth, S. M.; Foran, G. J.; Cookson, D. J.; Llewellyn, D. J.; Ridgway, M. C.

    2006-09-01

    Cu nanocrystals (NCs) were synthesized in SiO 2 by ion implantation and thermal annealing. Annealing at two different temperatures of 950 °C and 650 °C yielded two different nanocrystal size distributions with an average diameter of 8.1 and 2.5 nm, respectively. Subsequently the NCs were exposed to 5.0 MeV Sn 3+ ion irradiation simultaneously with a thin Cu film as a bulk reference. The short-range atomic structure and average NC diameter was measured by means of extended X-ray absorption fine structure (EXAFS) spectroscopy and small angle X-ray scattering (SAXS), respectively. Consistent with the high regeneration rate of bulk elemental metals, no irradiation induced defects were observed for the reference, whereas the small NCs (2.5 nm) were dissolved as Cu monomers in the matrix. The latter was attributed to irradiation-induced mixing of Cu, Si and O based on dynamic binary collision simulations. For the large NCs (8.1 nm) only minor structural changes were observed upon irradiation, consistent with a more bulk-like pre-irradiation structure.

  11. In situ synthesis and hydrothermal crystallization of nanoanatase TiO2 -SiO2 coating on aramid fabric (HTiSiAF) for UV protection.

    PubMed

    Deng, Hui; Zhang, Hongda

    2015-10-01

    TiO2 -SiO2 thin film was prepared by sol-gel method and coated on the aramid fabric to prepare functional textiles. The aramid fabric was dipped and withdrawn in TiO2 -SiO2 gel and hydrothermal crystallization at 80(°) C, then its UV protection functionality was evaluated. The crystalline phase and the surface morphology of TiO2 -SiO2 thin film were characterized using SEM, XRD, and AFM respectively. SEM showed hydrothermal crystallization led to a homogeneous dispersion of anatase nonocrystal in TiO2 -SiO2 film, and XRD suggested the mean particle size of the formed anatase TiO2 was less than 30 nm. AFM indicated that hydrothermal treatment enhanced the crystallization of TiO2 . UV protection analysis suggested that the hydrothermally treated coated textile had a better screening property in comparison with TiO2 -SiO2 gel and native aramid fabric. PMID:26303384

  12. Improved techniques for growth of large-area single-crystal Si sheets over SiO2 using lateral epitaxy by seeded solidification

    NASA Astrophysics Data System (ADS)

    Tsaur, B.-Y.; Fan, J. C. C.; Geis, M. W.; Silversmith, D. J.; Mountain, R. W.

    1981-10-01

    Continuous single-crystal Si sheets over SiO2 with areas of several square centimeters have been produced from poly-Si films by the LESS technique (lateral epitaxy by seeded solidification). Seeding is achieved either with a narrow stripe opening in a recessed SiO2 layer on a single-crystal Si substrate or with an external single-crystal Si seed. N-channel metal-oxide-semiconductor field-effect transistors (MOSFET's) fabricated in these films exhibit surface electron mobilities as high as 700 sq cm/V s.

  13. Silicon-silicon bonds in the oxide near the SiO 2/Si interface

    NASA Astrophysics Data System (ADS)

    Terada, Naozumi; Haga, Takashi; Miyata, Noriyuki; Moriki, Kazunori; Fujisawa, Masami; Morita, Mizuho; Ohmi, Tadahiro; Hattori, Takeo

    The contribution of the SiO 2/Si interface structure to optical absorption below the optical absorption edge of fused quartz was studied by measuring the reflectance of thermally grown ultrathin silicon oxide films. From the modified Kramers-Kronig analysis of reflectance, it was found that optical absorption at the photon energy of 7.8 eV arises from Si sbnd Si bonds in the oxide film within 1.4 nm of the interface. The approximate areal density of Si sbnd Si bonds is 7 × 10 14 cm -2 and is approximately equal to the areal density of silicon su☐ides determined by X-ray photoelectron spectroscopy.

  14. Molecular dynamics of liquid SiO2 under high pressure

    NASA Technical Reports Server (NTRS)

    Rustad, James R.; Yuen, David A.; Spera, Frank J.

    1990-01-01

    The molecular dynamics of pure SiO2 liquids was investigated up to pressures of 20 GPa at 4000 K using 252, 498, 864, and 1371 particles. The results obtained suggest that the pressure-induced maxima in the self-diffusion coefficients of both oxygen and silicon are dependent on the system size. In the case of larger systems, the maximum decreases and shifts to lower pressures. Changes in the velocity autocorrelation function with increasing pressure are described. The populations of anomalously coordinated silicon and oxygen are then discussed as a function of pressure and system size.

  15. Molecular-Orientation-Induced Rapid Roughening and Morphology Transition in Organic Semiconductor Thin-Film Growth

    PubMed Central

    Yang, Junliang; Yim, Sanggyu; Jones, Tim S.

    2015-01-01

    We study the roughening process and morphology transition of organic semiconductor thin film induced by molecular orientation in the model of molecular semiconductor copper hexadecafluorophthalocyanine (F16CuPc) using both experiment and simulation. The growth behaviour of F16CuPc thin film with the thickness, D, on SiO2 substrate takes on two processes divided by a critical thickness: (1) D ≤ 40 nm, F16CuPc thin films are composed of uniform caterpillar-like crystals. The kinetic roughening is confirmed during this growth, which is successfully analyzed by Kardar-Parisi-Zhang (KPZ) model with scaling exponents α = 0.71 ± 0.12, β = 0.36 ± 0.03, and 1/z = 0.39 ± 0.12; (2) D > 40 nm, nanobelt crystals are formed gradually on the caterpillar-like crystal surface and the film growth shows anomalous growth behaviour. These new growth behaviours with two processes result from the gradual change of molecular orientation and the formation of grain boundaries, which conversely induce new molecular orientation, rapid roughening process, and the formation of nanobelt crystals. PMID:25801646

  16. Plasmonic properties of Ag nanoparticles embedded in GeO2-SiO2 matrix by atom beam sputtering.

    PubMed

    Mohapatra, Satyabrata

    2016-02-01

    Nanocomposite thin films containing Ag nanoparticles embedded in the GeO2-SiO2 matrix were synthesized by the atom beam co-sputtering technique. The structural, optical and plasmonic properties and the chemical composition of the nanocomposite thin films were studied by transmission electron microscopy (TEM) with energy dispersive X-ray spectroscopy (EDX), UV-visible absorption spectroscopy and X-ray photoelectron spectroscopy (XPS). UV-visible absorption studies on Ag-SiO2 nanocomposites revealed the presence of a strong localized surface plasmon resonance (LSPR) peak characteristic of Ag nanoparticles at 413 nm, which showed a blue shift of 26 nm (413 to 387 nm) along with a significant broadening and drastic decrease in intensity with the incorporation of 16 at% of Ge into the SiO2 matrix. TEM studies on Ag-GeO2-SiO2 nanocomposite thin films confirmed the presence of Ag nanoparticles with an average size of 3.8 nm in addition to their aggregates with an average size of 16.2 nm. Thermal annealing in air resulted in strong enhancement in the intensity of the LSPR peak, which showed a regular red shift of 51 nm (from 387 to 438 nm) with the increase in annealing temperature up to 500 °C. XPS studies showed that annealing in air resulted in oxidation of excess Ge atoms in the nanocomposite into GeO2. Our work demonstrates the possibility of controllably tuning the LSPR of Ag nanoparticles embedded in the GeO2-SiO2 matrix by single-step thermal annealing, which is interesting for optical applications. PMID:26766559

  17. Lysine adsorption on the silanized SiO 2-surface for immobilization of the estrogen receptor hER α

    NASA Astrophysics Data System (ADS)

    Cherkouk, C.; Rebohle, L.; Skorupa, W.

    2011-03-01

    We investigated the adsorption of the L-lysine (200 mmol) molecule to a silanized SiO 2 surface as a function of the pH value. The SSC (Spraying Spin Coating) method [Cherkouk et al., J. Colloid Interf. Sci. 337 (2009) 375-380] was applied to functionalize the SiO 2 surface by using the (3-aminopropyl)trimethoxysilane (APMS) as coupling agent with a NH 2 functional group. We adsorbed lysine molecules to the silane film for pH-values of 2.5, 7.5, 8.7, 9.5 and 13, which correspond to the di-cationic, cationic, zwitterinonic (pH 8.7 and 9.5) and the anionic charge state of lysine, respectively. The infrared spectroscopy is not suitable to investigate the system because the NH 3+ signal at 1600 cm -1 originating from the silane film overlaps with the infrared signal of the deprotonated carboxyl group of the lysine molecule. X-ray photoelectron spectroscopy (XPS) was used to measure the binding energies C 1s and N 1s as function of the pH value. This pH change affects the charge state which was fitted in the XPS spectra to obtain the optimal adsorption conditions at pH 7.5 of the lysine to the functionalized SiO 2 surface.

  18. Avalanches in compressed porous SiO(2)-based materials.

    PubMed

    Nataf, Guillaume F; Castillo-Villa, Pedro O; Baró, Jordi; Illa, Xavier; Vives, Eduard; Planes, Antoni; Salje, Ekhard K H

    2014-08-01

    The failure dynamics in SiO(2)-based porous materials under compression, namely the synthetic glass Gelsil and three natural sandstones, has been studied for slowly increasing compressive uniaxial stress with rates between 0.2 and 2.8 kPa/s. The measured collapsed dynamics is similar to Vycor, which is another synthetic porous SiO(2) glass similar to Gelsil but with a different porous mesostructure. Compression occurs by jerks of strain release and a major collapse at the failure point. The acoustic emission and shrinking of the samples during jerks are measured and analyzed. The energy of acoustic emission events, its duration, and waiting times between events show that the failure process follows avalanche criticality with power law statistics over ca. 4 decades with a power law exponent ɛ≃ 1.4 for the energy distribution. This exponent is consistent with the mean-field value for the collapse of granular media. Besides the absence of length, energy, and time scales, we demonstrate the existence of aftershock correlations during the failure process. PMID:25215740

  19. SHI induced effects on the electrical and optical properties of HfO2 thin films deposited by RF sputtering

    NASA Astrophysics Data System (ADS)

    Manikanthababu, N.; Dhanunjaya, M.; Nageswara Rao, S. V. S.; Pathak, A. P.

    2016-07-01

    The continuous downscaling of Metal Oxide Semiconductor (MOS) devices has reached a limit with SiO2 as a gate dielectric material. Introducing high-k dielectric materials as a replacement for the conservative SiO2 is the only alternative to reduce the leakage current. HfO2 is a reliable and an impending material for the wide usage as a gate dielectric in semiconductor industry. HfO2 thin films were synthesized by RF sputtering technique. Here, we present a study of Swift Heavy Ion (SHI) irradiation with100 MeV Ag ions for studying the optical properties as well as 80 MeV Ni ions for studying the electrical properties of HfO2/Si thin films. Rutherford Backscattering Spectrometry (RBS), Field Emission Scanning Electron Microscope (FESEM), energy-dispersive X-ray spectroscopy (EDS), profilometer and I-V (leakage current) measurements have been employed to study the SHI induced effects on both the structural, electrical and optical properties.

  20. Wetting properties of phospholipid dispersion on tunable hydrophobic SiO2-glass plates.

    PubMed

    Alexandrova, Lidia; Karakashev, Stoyan I; Grigorov, L; Phan, Chi M; Smoukov, Stoyan K

    2015-06-01

    We study the wetting properties of very small droplets of salty aqueous suspensions of unilamellar liposomes of DMPC (dimyristoylphosphatidylcholine), situated on SiO2-glass surfaces with different levels of hydrophobicity. We evaluated two different measures of hydrophobicity of solid surfaces - receding contact angles and the thickness of wetting films trapped between an air bubble and the solid surface at different levels of hydrophobicity. We established a good correlation between methods which differ significantly in measurement difficulty and experimental setup. We also reveal details of the mechanism of wetting of different surfaces by the DMPC liposome suspension. Hydrophilic surfaces with water contact angles in the range of 0° to 35° are readily hydrophobized by the liposomes and only showed corresponding contact angles in the range 27°-43°. For same range of surface hydrophobicities, there was a clear reduction of the thickness of the wetting films between the surface and a bubble, reaching a minimum in the 35°-40° range. At higher levels of hydrophobicity both pure water and the liposome suspension show similar contact angles, and the thickness of wetting films between a bubble and those surfaces increases in parallel. Our analysis showed that the only force able to stabilize the film under these experimental conditions is steric repulsion. The latter suggests that nanobubbles adsorbed on hydrophobic parts of the surface, and coated with a DMPC layer, may be the cause of the 40-70 nm thickness of wetting films we observe. PMID:25441448

  1. Engineered magnetic core-shell SiO2/Fe microspheres and "medusa-like" microspheres of SiO2/iron oxide/carbon nanofibers or nanotubes.

    PubMed

    Mero, On; Sougrati, Moulay-Tahar; Jumas, Jean-Claude; Margel, Shlomo

    2014-08-19

    Iron oxide (IO) thin coatings of controlled thickness on SiO2 microspheres of narrow size distribution were prepared by decomposition at 160 °C of triiron dodecacarbonyl onto silica microspheres dispersed in diethylene glycol diethyl ether free of surfactant or stabilizer. The dried washed SiO2/IO core-shell microspheres were annealed at different temperatures and time periods under inert (Ar) or reducing (H2) atmosphere. The effect of temperature on the chemical composition, morphology, crystallinity, and magnetic properties of the IO and the elemental Fe nanoparticles type coatings onto the SiO2 core microspheres has been elucidated. "Medusa-like" SiO2/IO/carbon nanofibers and tubes particles were prepared by CVD of ethylene on the surface of the SiO2/IO microspheres at different temperatures. The morphology change of the grafted carbon nanofibers and tubes as a function of the CVD temperature was also elucidated. PMID:25089849

  2. Suppression of photo-bias induced instability for amorphous indium tungsten oxide thin film transistors with bi-layer structure

    NASA Astrophysics Data System (ADS)

    Liu, Po-Tsun; Chang, Chih-Hsiang; Chang, Chih-Jui

    2016-06-01

    This study investigates the instability induced by bias temperature illumination stress (NBTIS) for an amorphous indium-tungsten-oxide thin film transistor (a-IWO TFT) with SiO2 backchannel passivation layer (BPL). It is found that this electrical degradation phenomenon can be attributed to the generation of defect states during the BPL process, which deteriorates the photo-bias stability of a-IWO TFTs. A method proposed by adding an oxygen-rich a-IWO thin film upon the a-IWO active channel layer could effectively suppress the plasma damage to channel layer during BPL deposition process. The bi-layer a-IWO TFT structure with an oxygen-rich back channel exhibits superior electrical reliability of device under NBTIS.

  3. Nonvolatile memory characteristics of WSi2 nanocrystals embedded in SiO2 dielectrics.

    PubMed

    Seo, Ki Bong; Lee, Dong Uk; Han, Seung Jong; Kim, Seon Pil; Kim, Eun Kyu

    2011-01-01

    A nano-floating gate capacitor with WSi2 nanocrystals embedded in SiO2 dielectrics was fabricated. The WSi2 nanocrystals were created from ultrathin WSi2 film during rapid thermal annealing process and their average size and density were about 2.5 nm and 3.59 x 10(12) cm(-2), respectively. The flat-band voltage shift due to the carrier charging effect of WSi2 nanocrystals were measured up to 5.9 V when the gate voltage sweep in the range of +/- 9 V. The memory window was decreased from 3.7 V to 1.9 V after 1 h and remained about 3.7 V after 10(5) programming/erasing cycles. These results show that there is a possibility for the WSi2 nanocrystals to be applied to nonvolatile memory devices. PMID:21446472

  4. Structure and morphology of ion irradiated Au nanocrystals in SiO 2

    NASA Astrophysics Data System (ADS)

    Kluth, P.; Johannessen, B.; Kluth, S. M.; Foran, G. J.; Cookson, D. J.; Ridgway, M. C.

    2006-09-01

    We have investigated the effect of ion irradiation on the structure and morphology of Au nanocrystals (NCs) fabricated by ion beam synthesis in a thin SiO 2 layer on a Si substrate. Extended X-ray absorption fine structure (EXAFS) spectroscopy measurements show a significant drop in the average Au-Au coordination, as well as a loss of medium and long range order with increasing irradiation dose. Small angle X-ray scattering (SAXS) measurements reveal a concomitant reduction in average NC size. These observations are a consequence of structural disorder and collisional mixing induced by the irradiation. The observed reduction in average Au-Au coordination by EXAFS differs significantly from that estimated from the average NC sizes evaluated using SAXS. This behavior can be explained by the dissolution of Au NCs into the SiO 2 matrix. A significant bond-length contraction indicates that part of this material forms small Au clusters (dimers, trimers, etc.) during irradiation that cannot be detected by SAXS. Combining the results from SAXS and EXAFS measurements, we estimate the volume fraction of such clusters.

  5. Fabrication of rattle-type TiO2/SiO2 core/shell particles with both high photoactivity and UV-shielding property.

    PubMed

    Ren, Yuan; Chen, Min; Zhang, Yang; Wu, Limin

    2010-07-01

    Rattle-type TiO(2)@void@SiO(2) particles, with commercial TiO(2) particles encapsulated into hollow SiO(2) shell, were fabricated by successive coating of multilayer polyelectrolytes and SiO(2) shell onto TiO(2) particles and then treatment by UV irradiation to remove the polyelectrolyte layers. TEM observation showed that the composite particles had a unique rattle-type structure in which there existed void space between TiO(2) core and SiO(2) shell. The photocatalytic degradation of Rhodamine B indicated that these composite particles with larger void space tended to have higher photoactivity. The polyurethane films doped with rattle-type TiO(2)@void@SiO(2) composite particles had very good UV-shielding property. PMID:20536170

  6. Effect of resist mask roughing on the etching profile of SiO2 trench under the presence of local charging

    NASA Astrophysics Data System (ADS)

    Inagaki, Shinpei; Yagisawa, Takashi; Makabe, Toshiaki

    2009-10-01

    The reactive ion etching (RIE) of high-aspect ratio contact hole made of SiO2 has been traditionally performed by fluorocarbon gas CxFy diluted with Ar (> 90%) in a two-frequency capacitively coupled plasma (2f-CCP) reactor. The RIE proceeds under the competition among surface protection by the deposition of CxFy radicals, chemical sputtering by energetic ions, and topological charging caused by the difference of velocity distribution of ions and electrons coming to the surface. In our previous work, feature profile evolution of SiO2 trench pattern was predicted by using the level-set method considering mixing layer and CxFy polymer layer on SiO2 substrate. It is experimentally known that the roughness of the photoresist mask on SiO2 film makes large influence on the etching profile, called ``faceting'' or ``striation'' probably due to the high-energy ion impact. In this study, we develop our feature profile model in order to investigate the relation between resist mask roughing and the feature profile of SiO2 trench. Attention will be paid to the scattering of incident ions on the faceting structure of the resist mask and local charging as functions of the flux velocity distribution of ions and radicals.

  7. Direct fabrication of hybrid nanofibres composed of SiO2-PMMA nanospheres via electrospinning.

    PubMed

    Zhang, Ran; Shang, Tinghua; Yang, Guang; Jia, Xiaolong; Cai, Qing; Yang, Xiaoping

    2016-08-01

    The direct fabrication of hybrid nanofibres composed of poly(methyl methacrylate)-grafted SiO2 (SiO2-PMMA) nanospheres via electrospinning was investigated in detail. SiO2-PMMA nanospheres were successfully prepared, with the SiO2 nanospheres synthesized via the Stober method, followed by in situ surface-initiated atom transfer radical polymerization of methyl methacrylate (MMA). Electrospinning was carried out with N,N-dimethylformamide (DMF) as the solvent to disperse SiO2-PMMA nanospheres. The size of the SiO2 core, the molecular weight of the PMMA shell and the concentration of the SiO2-PMMA/DMF solution all had substantial effects on the morphology and structure of electrospun nanofibres composed of SiO2-PMMA nanospheres. When these determining factors were well-tailored, it was found that one-dimensional necklace-like nanofibres were obtained, with SiO2-PMMA nanospheres aligned one by one along the fibre. The successful fabrication of nanofibres by directly electrospinning the SiO2-PMMA/DMF solution verified that polymer-grafted particles possess polymer-like characteristics, which endowed them with the ability to be processed into desirable shapes and structures. PMID:27092439

  8. Silicon (100)/SiO2 by XPS

    SciTech Connect

    Jensen, David S.; Kanyal, Supriya S.; Madaan, Nitesh; Vail, Michael A.; Dadson, Andrew; Engelhard, Mark H.; Linford, Matthew R.

    2013-09-25

    Silicon (100) wafers are ubiquitous in microfabrication and, accordingly, their surface characteristics are important. Herein, we report the analysis of Si (100) via X-ray photoelectron spectroscopy (XPS) using monochromatic Al K radiation. Survey scans show that the material is primarily silicon and oxygen, and the Si 2p region shows two peaks that correspond to elemental silicon and silicon dioxide. Using these peaks the thickness of the native oxide (SiO2) was estimated using the equation of Strohmeier.1 The oxygen peak is symmetric. The material shows small amounts of carbon, fluorine, and nitrogen contamination. These silicon wafers are used as the base material for subsequent growth of templated carbon nanotubes.

  9. Single Particle Jumps in Sheared SiO2

    NASA Astrophysics Data System (ADS)

    McMahon, Sean; Vollmayr-Lee, Katharina; Cookmeyer, Jonathan; Horbach, Juergen

    We study the dynamics of a sheared glass via molecular dynamics simulations. Using the BKS potential we simulate the strong glass former SiO2. The system is initially well equilibrated at a high temperature, then quenched to a temperature below the glass transition, and, after a waiting time at the desired low temperature, sheared with constant strain rate. We present preliminary results of an analysis of single particle trajectories of the sheared glass. We acknowledge the support via NSF REU Grant #PHY-1156964, DoD ASSURE program, and NSF-MRI CHE-1229354 as part of the MERCURY high-performance computer consortium. We thank G.P. Shrivastav, Ch. Scherer and B. Temelso.

  10. In vitro and in vivo genotoxicity investigations of differently sized amorphous SiO2 nanomaterials.

    PubMed

    Maser, Elena; Schulz, Markus; Sauer, Ursula G; Wiemann, Martin; Ma-Hock, Lan; Wohlleben, Wendel; Hartwig, Andrea; Landsiedel, Robert

    2015-12-01

    In vitro and in vivo genotoxic effects of differently sized amorphous SiO2 nanomaterials were investigated. In the alkaline Comet assay (with V79 cells), non-cytotoxic concentrations of 300 and 100-300μg/mL 15nm-SiO2 and 55nm-SiO2, respectively, relevant (at least 2-fold relative to the negative control) DNA damage. In the Alkaline unwinding assay (with V79 cells), only 15nm-SiO2 significantly increased DNA strand breaks (and only at 100μg/mL), whereas neither nanomaterial (up to 300μg/mL) increased Fpg (Formamidopyrimidine DNA glycosylase)-sensitive sites reflecting oxidative DNA base modifications. In the Comet assay using rat precision-cut lung slices, 15nm-SiO2 and 55nm-SiO2 induced significant DNA damage at ≥100μg/mL. In the Alkaline unwinding assay (with A549 cells), 30nm-SiO2 and 55nm-SiO2 (with larger primary particle size (PPS)) induced significant increases in DNA strand breaks at ≥50μg/mL, whereas 9nm-SiO2 and 15nm-SiO2 (with smaller PPS) induced significant DNA damage at higher concentrations. These two amorphous SiO2 also increased Fpg-sensitive sites (significant at 100μg/mL). In vivo, within 3 days after single intratracheal instillation of 360μg, neither 15nm-SiO2 nor 55nm-SiO2 caused genotoxic effects in the rat lung or in the bone marrow. However, pulmonary inflammation was observed in both test groups with findings being more pronounced upon treatment with 15nm-SiO2 than with 55nm-SiO2. Taken together, the study shows that colloidal amorphous SiO2 with different particle sizes may induce genotoxic effects in lung cells in vitro at comparatively high concentrations. However, the same materials elicited no genotoxic effects in the rat lung even though pronounced pulmonary inflammation evolved. This may be explained by the fact that a considerably lower dose reached the target cells in vivo than in vitro. Additionally, the different time points of investigation may provide more time for DNA damage repair after instillation. PMID:26653985