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Sample records for initially p-type silicon

  1. Application of neutron transmutation doping method to initially p-type silicon material.

    PubMed

    Kim, Myong-Seop; Kang, Ki-Doo; Park, Sang-Jun

    2009-01-01

    The neutron transmutation doping (NTD) method was applied to the initially p-type silicon in order to extend the NTD applications at HANARO. The relationship between the irradiation neutron fluence and the final resistivity of the initially p-type silicon material was investigated. The proportional constant between the neutron fluence and the resistivity was determined to be 2.3473x10(19)nOmegacm(-1). The deviation of the final resistivity from the target for almost all the irradiation results of the initially p-type silicon ingots was at a range from -5% to 2%. In addition, the burn-up effect of the boron impurities, the residual (32)P activity and the effect of the compensation characteristics for the initially p-type silicon were studied. Conclusively, the practical methodology to perform the neutron transmutation doping of the initially p-type silicon ingot was established. PMID:19318259

  2. Transport through a single donor in p-type silicon

    NASA Astrophysics Data System (ADS)

    Miwa, J. A.; Mol, J. A.; Salfi, J.; Rogge, S.; Simmons, M. Y.

    2013-07-01

    Single phosphorus donors in silicon are promising candidates as qubits in the solid state. Here, we present low temperature scanning probe microscopy and spectroscopy measurements of individual phosphorus dopants deliberately placed in p-type silicon ˜1 nm below the surface. The ability to image individual dopants combined with scanning tunnelling spectroscopy allows us to directly study the transport mechanism through the donor. We show that for a single P donor, transport is dominated by a minority carrier recombination process with the surrounding p-type matrix. The understanding gained will underpin future studies of atomically precise mapping of donor-donor interactions in silicon.

  3. Irradiation and annealing of p-type silicon carbide

    SciTech Connect

    Lebedev, Alexander A.; Bogdanova, Elena V.; Grigor'eva, Maria V.; Lebedev, Sergey P.; Kozlovski, Vitaly V.

    2014-02-21

    The development of the technology of semiconductor devices based on silicon carbide and the beginning of their industrial manufacture have made increasingly topical studies of the radiation hardness of this material on the one hand and of the proton irradiation to form high-receptivity regions on the other hand. This paper reports on a study of the carrier removal rate (V{sub d}) in p-6H-SiC under irradiation with 8 MeV protons and of the conductivity restoration in radiation- compensated epitaxial layers of various p-type silicon carbide polytypes. V{sub d} was determined by analysis of capacitance-voltage characteristics and from results of Hall effect measurements. It was found that the complete compensation of samples with the initial value of Na - Nd ≈ 1.5 × 10{sup 18} cm{sup −3} occurs at an irradiation dose of ∼1.1 × 10{sup 16} cm{sup −2}. It is shown that specific features of the sublimation layer SiC (compared to CVD layers) are clearly manifested upon the gamma and electron irradiation and are hardly noticeable under the proton and neutron irradiation. It was also found that the radiation-induced compensation of SiC is retained after its annealing at ≤1000°C. The conductivity is almost completely restored at T ≥ 1200°C. This character of annealing of the radiation compensation is independent of a silicon carbide polytype and the starting doping level of the epitaxial layer. The complete annealing temperatures considerably exceed the working temperatures of SiC-based devices. It is shown that the radiation compensation is a promising method in the technology of high-temperature devices based on SiC.

  4. Anodic etching of p-type cubic silicon carbide

    NASA Technical Reports Server (NTRS)

    Harris, G. L.; Fekade, K.; Wongchotigul, K.

    1992-01-01

    p-Type cubic silicon carbide was anodically etched using an electrolyte of HF:HCl:H2O. The etching depth was determined versus time with a fixed current density of 96.4 mA/sq cm. It was found that the etching was very smooth and very uniform. An etch rate of 22.7 nm/s was obtained in a 1:1:50 HF:HCl:H2O electrolyte.

  5. Laser induced lifetime degradation in p-type crystalline silicon

    SciTech Connect

    Ametowobla, M.; Bilger, G.; Koehler, J. R.; Werner, J. H.

    2012-06-01

    Pulsed, green laser irradiation of uncoated p-type silicon leads to a significant reduction of the effective minority carrier lifetime. The reason for the lifetime drop lies in the introduction of recombination centres into the laser melted and recrystallized surface layer, leading to a low local minority carrier lifetime {tau} Almost-Equal-To 10 ns inside this surface layer. The laser treatment introduces the impurities oxygen, carbon and nitrogen into the silicon and further leads to an n-type doping of the surface layer. There are strong indications that these impurities are responsible for the observed n-type doping, as well as the lifetime reduction after irradiation. Both effects are removed by thermal annealing. An estimate shows that the low local lifetime does nevertheless not affect the performance of industrial or contacted selective solar cell emitter structures.

  6. Laser induced lifetime degradation in p-type crystalline silicon

    NASA Astrophysics Data System (ADS)

    Ametowobla, M.; Bilger, G.; Köhler, J. R.; Werner, J. H.

    2012-06-01

    Pulsed, green laser irradiation of uncoated p-type silicon leads to a significant reduction of the effective minority carrier lifetime. The reason for the lifetime drop lies in the introduction of recombination centres into the laser melted and recrystallized surface layer, leading to a low local minority carrier lifetime τ ≈ 10 ns inside this surface layer. The laser treatment introduces the impurities oxygen, carbon and nitrogen into the silicon and further leads to an n-type doping of the surface layer. There are strong indications that these impurities are responsible for the observed n-type doping, as well as the lifetime reduction after irradiation. Both effects are removed by thermal annealing. An estimate shows that the low local lifetime does nevertheless not affect the performance of industrial or contacted selective solar cell emitter structures.

  7. Ferromagnetic states of p-type silicon doped with Mn

    NASA Astrophysics Data System (ADS)

    Yunusov, Z. A.; Yuldashev, Sh. U.; Igamberdiev, Kh. T.; Kwon, Y. H.; Kang, T. W.; Bakhadyrkhanov, M. K.; Isamov, S. B.; Zikrillaev, N. F.

    2014-05-01

    In this work, the ferromagnetic states of Mn-doped p-type silicon samples were investigated. Two different types of ferromagnetic states have been observed in Si (Mn, B). The samples with a relatively high concentration of Mn revealed a ferromagnetic state with a Curie temperature above room temperature, and that ferromagnetism was due to the Mn x B y ferromagnetic clusters. The samples with a moderate concentration of Mn at low temperatures revealed a ferromagnetic state that was mediated by carriers (holes). The samples demonstrated the anomalous Hall effect at temperatures below 100 K and had a negative magneto-resistivity peak at a temperature close to the Curie temperature. The thermal diffusivity measurements demonstrated the existence of a second-order phase transition in the samples with a moderate Mn concentration. The specific heat's critical exponent α = 0.5, determined from the thermal diffusivity measurements, confirmed the long-range nature of the magnetic exchange interaction in these samples.

  8. P type porous silicon resistivity and carrier transport

    SciTech Connect

    Ménard, S.; Fèvre, A.; Billoué, J.; Gautier, G.

    2015-09-14

    The resistivity of p type porous silicon (PS) is reported on a wide range of PS physical properties. Al/PS/Si/Al structures were used and a rigorous experimental protocol was followed. The PS porosity (P{sub %}) was found to be the major contributor to the PS resistivity (ρ{sub PS}). ρ{sub PS} increases exponentially with P{sub %}. Values of ρ{sub PS} as high as 1 × 10{sup 9} Ω cm at room temperature were obtained once P{sub %} exceeds 60%. ρ{sub PS} was found to be thermally activated, in particular, when the temperature increases from 30 to 200 °C, a decrease of three decades is observed on ρ{sub PS}. Based on these results, it was also possible to deduce the carrier transport mechanisms in PS. For P{sub %} lower than 45%, the conduction occurs through band tails and deep levels in the tissue surrounding the crystallites. When P{sub %} overpasses 45%, electrons at energy levels close to the Fermi level allow a hopping conduction from crystallite to crystallite to appear. This study confirms the potential of PS as an insulating material for applications such as power electronic devices.

  9. Development of improved p-type silicon-germanium alloys

    NASA Technical Reports Server (NTRS)

    Mclane, George; Wood, Charles; Vandersande, Jan; Raag, Valvo; Heshmatpour, Ben

    1987-01-01

    Annealing experiments in the temperature range 1100-1275 C have been performed on p-type Si(0.8)Ge(0.2) samples with BP, B(6.5)P, and GaSb material additives. Both electrical resistivity and Seebeck coefficient generally decrease for these samples as annealing temperature is increased, with thermoelectric power factor sometimes being improved by annealing.

  10. Reassessment of the recombination parameters of chromium in n- and p-type crystalline silicon and chromium-boron pairs in p-type crystalline silicon

    SciTech Connect

    Sun, Chang Rougieux, Fiacre E.; Macdonald, Daniel

    2014-06-07

    Injection-dependent lifetime spectroscopy of both n- and p-type, Cr-doped silicon wafers with different doping levels is used to determine the defect parameters of Cr{sub i} and CrB pairs, by simultaneously fitting the measured lifetimes with the Shockley-Read-Hall model. A combined analysis of the two defects with the lifetime data measured on both n- and p-type samples enables a significant tightening of the uncertainty ranges of the parameters. The capture cross section ratios k = σ{sub n}/σ{sub p} of Cr{sub i} and CrB are determined as 3.2 (−0.6, +0) and 5.8 (−3.4, +0.6), respectively. Courtesy of a direct experimental comparison of the recombination activity of chromium in n- and p-type silicon, and as also suggested by modelling results, we conclude that chromium has a greater negative impact on carrier lifetimes in p-type silicon than n-type silicon with similar doping levels.

  11. Single p-type/intrinsic/n-type silicon nanowires as nanoscale avalanche photodetectors.

    PubMed

    Yang, Chen; Barrelet, Carl J; Capasso, Federico; Lieber, Charles M

    2006-12-01

    We report the controlled synthesis of axial modulation-doped p-type/intrinsic/n-type (p-i-n) silicon nanowires with uniform diameters and single-crystal structures. The p-i-n nanowires were grown in three sequential steps: in the presence of diborane for the p-type region, in the absence of chemical dopant sources for the middle segment, and in the presence of phosphine for the n-type region. The p-i-n nanowires were structurally characterized by transmission electron microscopy, and the spatially resolved electrical properties of individual nanowires were determined by electrostatic force and scanning gate microscopies. Temperature-dependent current-voltage measurements recorded from individual p-i-n devices show an increase in the breakdown voltage with temperature, characteristic of band-to-band impact ionization, or avalanche breakdown. Spatially resolved photocurrent measurements show that the largest photocurrent is generated at the intrinsic region located between the electrode contacts, with multiplication factors in excess of ca. 30, and demonstrate that single p-i-n nanowires function as avalanche photodiodes. Electron- and hole-initiated avalanche gain measurements performed by localized photoexcitation of the p-type and n-type regions yield multiplication factors of ca. 100 and 20, respectively. These results demonstrate the significant potential of single p-i-n nanowires as nanoscale avalanche photodetectors and open possible opportunities for studying impact ionization of electrons and holes within quasi-one-dimensional semiconductor systems. PMID:17163733

  12. Method of mitigating titanium impurities effects in p-type silicon material for solar cells

    NASA Technical Reports Server (NTRS)

    Salama, A. M. (Inventor)

    1980-01-01

    Microstructural evaluation tests performed on Cu-doped, Ti-doped and Cu/Ti doped p-type silicon single crystal wafers, before and after the solar cell fabrication, and evaluation of both dark forward and reverse I-V characteristic records for the solar cells produced from the corresponding silicon wafers, show that Cu mitigates the unfavorable effects of Ti, and thus provides for higher conversion efficiency, thereby providing an economical way to reduce the deleterious effects of titanium, one of the impurities present in metallurgical grade silicon material.

  13. Use of hexamethyldisiloxane for p-type microcrystalline silicon oxycarbide layers

    NASA Astrophysics Data System (ADS)

    Goyal, Prabal; Hong, Junegie; Haddad, Farah; Maurice, Jean-Luc; Cabarrocas, Pere Roca i.; Johnson, Erik

    2016-01-01

    The use of hexamethyldisiloxane (HMDSO) as an oxygen source for the growth of p-type silicon-based layers deposited by Plasma Enhanced Chemical Vapor Deposition is evaluated. The use of this source led to the incorporation of almost equivalent amounts of oxygen and carbon, resulting in microcrystalline silicon oxycarbide thin films. The layers were examined with characterisation techniques including Spectroscopic Ellipsometry, Dark Conductivity, Fourier Transform Infrared Spectroscopy, Secondary Ion Mass Spectrometry and Transmission Electron Microscopy to check material composition and structure. Materials studies show that the refractive indices of the layers can be tuned over the range from 2.5 to 3.85 (measured at 600 nm) and in-plane dark conductivities over the range from 10-8 S/cm to 1 S/cm, suggesting that these doped layers are suitable for solar cell applications. The p-type layers were tested in single junction amorphous silicon p-i-n type solar cells.

  14. Dual ohmic contact to N- and P-type silicon carbide

    NASA Technical Reports Server (NTRS)

    Okojie, Robert S. (Inventor)

    2013-01-01

    Simultaneous formation of electrical ohmic contacts to silicon carbide (SiC) semiconductor having donor and acceptor impurities (n- and p-type doping, respectively) is disclosed. The innovation provides for ohmic contacts formed on SiC layers having n- and p-doping at one process step during the fabrication of the semiconductor device. Further, the innovation provides a non-discriminatory, universal ohmic contact to both n- and p-type SiC, enhancing reliability of the specific contact resistivity when operated at temperatures in excess of 600.degree. C.

  15. Novel method of separating macroporous arrays from p-type silicon substrate

    NASA Astrophysics Data System (ADS)

    Bobo, Peng; Fei, Wang; Tao, Liu; Zhenya, Yang; Lianwei, Wang; Fu, Ricky K. Y.; Chu, Paul K.

    2012-04-01

    This paper presents a novel method to fabricate separated macroporous silicon using a single step of photo-assisted electrochemical etching. The method is applied to fabricate silicon microchannel plates in 100 mm p-type silicon wafers, which can be used as electron multipliers and three-dimensional Li-ion microbatteries. Increasing the backside illumination intensity and decreasing the bias simultaneously can generate additional holes during the electrochemical etching which will create lateral etching at the pore tips. In this way the silicon microchannel can be separated from the substrate when the desired depth is reached, then it can be cut into the desired shape by using a laser cutting machine. Also, the mechanism of lateral etching is proposed.

  16. Suppression of hydrogen diffusion at the hydrogen-induced platelets in p-type Czochralski silicon

    SciTech Connect

    Huang, Y.L.; Ma, Y.; Job, R.; Fahrner, W.R.

    2005-03-28

    Hydrogen diffusion in p-type Czochralski silicon is investigated by combined Raman spectroscope, scanning electron microscope, and spreading resistance probe measurements. Exposure of silicon wafers to rf hydrogen plasma results in the formation of platelets. The increase of hydrogenation duration leads to the growth of the platelets and the reduction of the hydrogen diffusivity. The large platelets grow faster than the small ones. The growth of the platelets is based on the capture of hydrogen. The dependence of the hydrogen diffusivity upon the average size of the platelets suggests that the indiffusion of hydrogen is suppressed by the platelets.

  17. Microhardness studies on thin carbon films grown on P-type, (100) silicon

    NASA Technical Reports Server (NTRS)

    Kolecki, J. C.

    1982-01-01

    A program to grow thin carbon films and investigate their physical and electrical properties is described. Characteristics of films grown by rf sputtering and vacuum arc deposition on p type, (100) silicon wafers are presented. Microhardness data were obtained from both the films and the silicon via the Vickers diamond indentation technique. These data show that the films are always harder than the silicon, even when the films are thin (of the order of 1000 A). Vacuum arc films were found to contain black carbon inclusions of the order of a few microns in size, and clusters of inclusions of the order of tens of microns. Transmission electron diffraction showed that the films being studied were amorphous in structure.

  18. High-temperature elastic moduli of bulk nanostructured n - and p -type silicon germanium

    NASA Astrophysics Data System (ADS)

    Gladden, J. R.; Li, G.; Adebisi, R.; Firdosy, S.; Caillat, T.; Ravi, V.

    2010-07-01

    Resonant ultrasound spectroscopy (RUS) has been used to measure the elastic moduli of n - and p -type doped polycrystalline bulk nanostructured silicon germanium alloys at elevated temperatures. A direct contact RUS transducer system with a working temperature range up to 900 K was successfully constructed for these measurements. For higher temperatures (up to 1300 K), we employed a traditional buffer rod RUS system. Experimental results show the Young’s and shear moduli of p -type SiGe alloys monotonically decrease with increasing temperatures in the 300-1200 K range. The n -type samples show a marked stiffening beginning at 675 K which does not repeat upon cooling or subsequent reheating. We attribute the stiffening of the n -type samples to the thermally activated precipitation of the phosphorous dopant. Electrical resistivity and Seebeck coefficient data are also presented for both types of SiGe which support this conclusion.

  19. Absence of positronium formation in clean buried nanocavities in p-type silicon

    SciTech Connect

    Brusa, R.S.; Macchi, C.; Mariazzi, S.; Karwasz, G.P.; Egger, W.; Sperr, P.; Koegel, G.

    2005-06-15

    Buried nanocavities at about 350 nm depth in Si were produced by thermal treatment of He implanted p-type (100) Si. The internal surfaces of the nanocavities were found free of impurity decorations by examining the high-momentum part of the Doppler-broadened positron annihilation spectra. Positron lifetime measurements with a pulsed slow positron beam show neither a short lifetime (125-150 ps) ascribable to parapositronium nor a longer lifetime (2-4 ns) ascribable to pick-off annihilation of orthopositronium. The lifetime of positrons trapped into nanocavities was found to be about 500 ps. The absence of positronium formation could be explained by an insufficient electron density and a lack of electron states in the band gap at the nanocavities internal surfaces produced in the p-type silicon.

  20. Direct Measurement of Electron Beam Induced Currents in p-type Silicon

    SciTech Connect

    Han, M.G.; Zhu, Y.; Sasaki, K.; Kato, T.; Fisher, C.A.J.; Hirayama, T.

    2010-08-01

    A new method for measuring electron beam induced currents (EBICs) in p-type silicon using a transmission electron microscope (TEM) with a high-precision tungsten probe is presented. Current-voltage (I-V) curves obtained under various electron-beam illumination conditions are found to depend strongly on the current density of the incoming electron beam and the relative distance of the beam from the point of probe contact, consistent with a buildup of excess electrons around the contact. This setup provides a new experimental approach for studying minority carrier transport in semiconductors on the nanometer scale.

  1. Accelerated light-induced degradation for detecting copper contamination in p-type silicon

    SciTech Connect

    Inglese, Alessandro Savin, Hele; Lindroos, Jeanette

    2015-08-03

    Copper is a harmful metal impurity that significantly impacts the performance of silicon-based devices if present in active regions. In this contribution, we propose a fast method consisting of simultaneous illumination and annealing for the detection of copper contamination in p-type silicon. Our results show that, within minutes, such method is capable of producing a significant reduction of the minority carrier lifetime. A spatial distribution map of copper contamination can then be obtained through the lifetime values measured before and after degradation. In order to separate the effect of the light-activated copper defects from the other metastable complexes in low resistivity Cz-silicon, we carried out a dark anneal at 200 °C, which is known to fully recover the boron-oxygen defect. Similar to the boron-oxygen behavior, we show that the dark anneal also recovers the copper defects. However, the recovery is only partial and it can be used to identify the possible presence of copper contamination.

  2. Effective surface passivation of p-type crystalline silicon with silicon oxides formed by light-induced anodisation

    NASA Astrophysics Data System (ADS)

    Cui, Jie; Grant, Nicholas; Lennon, Alison

    2014-12-01

    Electronic surface passivation of p-type crystalline silicon by anodic silicon dioxide (SiO2) was investigated. The anodic SiO2 was grown by light-induced anodisation (LIA) in diluted sulphuric acid at room temperature, a process that is significantly less-expensive than thermal oxidation which is widely-used in silicon solar cell fabrication. After annealing in oxygen and then forming gas at 400 °C for 30 min, the effective minority carrier lifetime of 3-5 Ω cm, boron-doped Czochralski silicon wafers with a phosphorus-doped 80 Ω/□ emitter and a LIA anodic SiO2 formed on the p-type surface was increased by two orders of magnitude to 150 μs. Capacitance-voltage measurements demonstrated a very low positive charge density of 3.4 × 1011 cm-2 and a moderate density of interface states of 6 × 1011 eV-1 cm-2. This corresponded to a silicon surface recombination velocity of 62 cm s-1, which is comparable with values reported for other anodic SiO2 films, which required higher temperatures and longer growth times, and significantly lower than oxides grown by chemical vapour deposition techniques. Additionally, a very low leakage current density of 3.5 × 10-10 and 1.6 × 10-9 A cm-2 at 1 and -1 V, respectively, was measured for LIA SiO2 suggesting its potential application as insulation layer in IBC solar cells and a barrier for potential induced degradation.

  3. Scanning electrochemical microscopy investigations of monolayers bound to p-type silicon substrates.

    PubMed

    Ghilane, Jalal; Hauquier, Fanny; Fabre, Bruno; Hapiot, Philippe

    2006-09-01

    p-Si type electrodes modified with different organic monolayers were investigated by reaction with radical anion and cation electrogenerated at a microelectrode operating in the configuration of a scanning electrochemical microscope. The method proves to be a convenient tool for investigating both the quality and the redox properties of the layer as previously demonstrated on metallic electrodes especially when the sample cannot be electrically connected. Approach curves recorded with the different mediators were used to investigate the electron-transfer rates across alkyl monolayers bound to p-type silicon substrates. Preliminary results indicate that the interfacial electron transfer occurs via electron tunneling through the organic layer as generally described for SAMs grafted on gold electrodes. PMID:16944879

  4. Characterization of irradiated detectors fabricated on p-type silicon substrates for super-LHC

    NASA Astrophysics Data System (ADS)

    Miñano, M.; Campabadal, F.; Escobar, C.; García, C.; González, S.; Lacasta, C.; Lozano, M.; Martí i García, S.; Pellegrini, G.; Rafí, J. M.; Ullán, M.

    2007-12-01

    An upgrade of the large hadron collider (LHC), the Super-LHC (SLHC), towards higher luminosities is currently being discussed as an extension of the LHC physics program. The goal of the SLHC is to operate at a luminosity of 10 35 cm -2 s -1 (10 times larger than that of the LHC one). Thus, the operation of the SLHC implies a need to upgrade the detectors of the LHC experiments. The current tracking system of ATLAS will not cope with that luminosity. New solutions must be investigated to improve the radiation tolerance of the semiconductor detector. p-Type bulk sensors are being considered for the ATLAS tracking system for the SLHC. Microstrip detectors fabricated by CNM-IMB on p-type high-resistivity float zone silicon have been irradiated with neutrons at the TRIGA Mark II reactor in Ljubljana up to a fluence of 10 16 cm -2 (as expected in the innermost region of the ATLAS upgrade) and have been characterized at IFIC Laboratory. The collected charge, after irradiation, has been measured by infrared laser illumination. The leakage current of those sensors is also reported.

  5. Fabrication of p-type porous silicon nanowire with oxidized silicon substrate through one-step MACE

    SciTech Connect

    Li, Shaoyuan; Ma, Wenhui; Zhou, Yang; Chen, Xiuhua; Xiao, Yongyin; Ma, Mingyu; Wei, Feng; Yang, Xi

    2014-05-01

    In this paper, the simple pre-oxidization process is firstly used to treat the starting silicon wafer, and then MPSiNWs are successfully fabricated from the moderately doped wafer by one-step MACE technology in HF/AgNO{sub 3} system. The PL spectrum of MPSiNWs obtained from the oxidized silicon wafers show a large blue-shift, which can be attributed to the deep Q. C. effect induced by numerous mesoporous structures. The effects of HF and AgNO{sub 3} concentration on formation of SiNWs were carefully investigated. The results indicate that the higher HF concentration is favorable to the growth of SiNWs, and the density of SiNWs is significantly reduced when Ag{sup +} ions concentrations are too high. The deposition behaviors of Ag{sup +} ions on oxidized and unoxidized silicon surface were studied. According to the experimental results, a model was proposed to explain the formation mechanism of porous SiNWs by etching the oxidized starting silicon. - Graphical abstract: Schematic cross-sectional views of PSiNWs array formation by etching oxidized silicon wafer in HF/AgNO{sub 3} solution. (A) At the starting point; (B) during the etching process; and (C) after Ag dendrites remove. - Highlights: • Prior to etching, a simple pre-oxidation is firstly used to treat silicon substrate. • The medially doped p-type MPSiNWs are prepared by one-step MACE. • Deposition behaviors of Ag{sup +} ions on oxidized and unoxidized silicon are studied. • A model is finally proposed to explain the formation mechanism of PSiNWs.

  6. Percolation network in resistive switching devices with the structure of silver/amorphous silicon/p-type silicon

    SciTech Connect

    Liu, Yanhong; Gao, Ping; Bi, Kaifeng; Peng, Wei; Jiang, Xuening; Xu, Hongxia

    2014-01-27

    Conducting pathway of percolation network was identified in resistive switching devices (RSDs) with the structure of silver/amorphous silicon/p-type silicon (Ag/a-Si/p-Si) based on its gradual RESET-process and the stochastic complex impedance spectroscopy characteristics (CIS). The formation of the percolation network is attributed to amounts of nanocrystalline Si particles as well as defect sites embedded in a-Si layer, in which the defect sites supply positions for Ag ions to nucleate and grow. The similar percolation network has been only observed in Ag-Ge-Se based RSD before. This report provides a better understanding for electric properties of RSD based on the percolation network.

  7. Evidence for an iron-hydrogen complex in p-type silicon

    NASA Astrophysics Data System (ADS)

    Leonard, S.; Markevich, V. P.; Peaker, A. R.; Hamilton, B.; Murphy, J. D.

    2015-07-01

    Interactions of hydrogen with iron have been studied in Fe contaminated p-type Czochralski silicon using capacitance-voltage profiling and deep level transient spectroscopy (DLTS). Hydrogen has been introduced into the samples from a silicon nitride layer grown by plasma enhanced chemical vapor deposition. After annealing of the Schottky diodes on Si:Fe + H samples under reverse bias in the temperature range of 90-120 °C, a trap has been observed in the DLTS spectra which we have assigned to a Fe-H complex. The trap is only observed when a high concentration of hydrogen is present in the near surface region. The trap concentration is higher in samples with a higher concentration of single interstitial Fe atoms. The defect has a deep donor level at Ev + 0.31 eV. Direct measurements of capture cross section of holes have shown that the capture cross section is not temperature dependent and its value is 5.2 × 10-17 cm2. It is found from an isochronal annealing study that the Fe-H complex is not very stable and can be eliminated completely by annealing for 30 min at 125 °C.

  8. Evidence for an iron-hydrogen complex in p-type silicon

    SciTech Connect

    Leonard, S. Markevich, V. P.; Peaker, A. R.; Hamilton, B.; Murphy, J. D.

    2015-07-20

    Interactions of hydrogen with iron have been studied in Fe contaminated p-type Czochralski silicon using capacitance-voltage profiling and deep level transient spectroscopy (DLTS). Hydrogen has been introduced into the samples from a silicon nitride layer grown by plasma enhanced chemical vapor deposition. After annealing of the Schottky diodes on Si:Fe + H samples under reverse bias in the temperature range of 90–120 °C, a trap has been observed in the DLTS spectra which we have assigned to a Fe-H complex. The trap is only observed when a high concentration of hydrogen is present in the near surface region. The trap concentration is higher in samples with a higher concentration of single interstitial Fe atoms. The defect has a deep donor level at E{sub v} + 0.31 eV. Direct measurements of capture cross section of holes have shown that the capture cross section is not temperature dependent and its value is 5.2 × 10{sup −17} cm{sup 2}. It is found from an isochronal annealing study that the Fe-H complex is not very stable and can be eliminated completely by annealing for 30 min at 125 °C.

  9. Aluminum-natural oxide-P type silicon /MIS/ solar cells

    NASA Astrophysics Data System (ADS)

    Badura, E.; Zdanowicz, W.

    1980-12-01

    MIS (metal-interfacial region-semiconductor) solar cells are attractive because of their relatively high conversion efficiency. Their performance, however, is strongly affected by device preparation. Two methods are described for preparing Al - natural SiO - p-type Si cells which exhibit high photovoltaic values. The first, involving a 'nonsintered oxide' process, entails etching the active silicon surfaces in HF acid and exposing them to air at room temperature for 48 hours. The second method differs from the first only in that it requires the additional step of sintering the oxidized surfaces in a vacuum at about 500 C. In both cases, a semitransparent Al film is then applied to the oxide, after which an Al grid electrode and 70-nm SiOx antireflection coatings are deposited on the device. Measured against both the nonsintered cell and the Schottky barrier cell, the sintered assembly shows the highest open-circuit voltage (0.46-0.492), the highest fill factor (0.66-0.73), and the most efficient dark parameters.

  10. Comparison of boron precipitation in p-type bulk nanostructured and polycrystalline silicon germanium alloy

    NASA Astrophysics Data System (ADS)

    Zamanipour, Zahra; Krasinski, Jerzy S.; Vashaee, Daryoosh

    2013-04-01

    Boron precipitation process and its effect on electronic properties of p-type bulk nanostructured silicon germanium (Si0.8Ge0.2) compared with large grain polycrystalline Si0.8Ge0.2 have been studied. The structures were synthesized and their thermoelectric properties were measured versus temperature during heating and cooling cycles. The experimental data showed stronger temperature variation of Seebeck coefficient, carrier concentration, and conductivity in the nanostructured Si0.8Ge0.2 compared with the polycrystalline form indicating stronger boron precipitation in this structure. The electrical properties of both samples were calculated using a multi-band semi-classical model. The theoretical calculations confirm that the increase of boron precipitation in the nanostructured Si0.8Ge0.2 is responsible for its higher thermal instability. Since the thermoelectric properties of the nanostructured sample degrade as a result of thermal cycling, the material is appropriate only for continuous operation at high temperature without cooling.

  11. RF performances of inductors integrated on localized p+-type porous silicon regions

    NASA Astrophysics Data System (ADS)

    Capelle, Marie; Billoué, Jérôme; Poveda, Patrick; Gautier, Gaël

    2012-09-01

    To study the influence of localized porous silicon regions on radiofrequency performances of passive devices, inductors were integrated on localized porous silicon regions, full porous silicon sheet, bulk silicon and glass substrates. In this work, a novel strong, resistant fluoropolymer mask is introduced to localize the porous silicon on the silicon wafer. Then, the quality factors and resonant frequencies obtained with the different substrates are presented. A first comparison is done between the performances of inductors integrated on same-thickness localized and full porous silicon sheet layers. The effect of the silicon regions in the decrease of performances of localized porous silicon is discussed. Then, the study shows that the localized porous silicon substrate significantly reduces losses in comparison with high-resistivity silicon or highly doped silicon bulks. These results are promising for the integration of both passive and active devices on the same silicon/porous silicon hybrid substrate.

  12. Value Proposition for High Lifetime (p-type) and Thin Silicon Materials in Solar PV Applications: Preprint

    SciTech Connect

    Goodrich, A.; Woodhouse, M.; Hacke, P.

    2012-06-01

    Most silicon PV road maps forecast a continued reduction in wafer thickness, despite rapid declines in the primary incentive for doing so -- polysilicon feedstock price. Another common feature of most silicon-technology forecasts is the quest for ever-higher device performance at the lowest possible costs. The authors present data from device-performance and manufacturing- and system-installation cost models to quantitatively establish the incentives for manufacturers to pursue advanced (thin) wafer and (high efficiency) cell technologies, in an age of reduced feedstock prices. This analysis exhaustively considers the value proposition for high lifetime (p-type) silicon materials across the entire c-Si PV supply chain.

  13. Mixed-phase p-type silicon oxide containing silicon nanocrystals and its role in thin-film silicon solar cells

    NASA Astrophysics Data System (ADS)

    Cuony, P.; Marending, M.; Alexander, D. T. L.; Boccard, M.; Bugnon, G.; Despeisse, M.; Ballif, C.

    2010-11-01

    Lower absorption, lower refractive index, and tunable resistance are three advantages of amorphous silicon oxide containing nanocrystalline silicon grains (nc-SiOx) compared to microcrystalline silicon (μc-Si), when used as a p-type layer in μc-Si thin-film solar cells. We show that p-nc-SiOx with its particular nanostructure increases μc-Si cell efficiency by reducing reflection and parasitic absorption losses depending on the roughness of the front electrode. Furthermore, we demonstrate that the p-nc-SiOx reduces the detrimental effects of the roughness on the electrical characteristics, and significantly increases μc-Si and Micromorph cell efficiency on substrates until now considered too rough for thin-film silicon solar cells.

  14. Surface States and Effective Surface Area on Photoluminescent P-Type Porous Silicon

    NASA Technical Reports Server (NTRS)

    Weisz, S. Z.; Porras, A. Ramirez; Resto, O.; Goldstein, Y.; Many, A.; Savir, E.

    1997-01-01

    The present study is motivated by the possibility of utilizing porous silicon for spectral sensors. Pulse measurements on the porous-Si/electrolyte system are employed to determine the surface effective area and the surface-state density at various stages of the anodization process used to produce the porous material. Such measurements were combined with studies of the photoluminescence spectra. These spectra were found to shift progressively to the blue as a function of anodization time. The luminescence intensity increases initially with anodization time, reaches a maximum and then decreases with further anodization. The surface state density, on the other hand, increases with anodization time from an initial value of about 2 x 10(exp 12)/sq cm surface to about 1013 sq cm for the anodized surface. This value is attained already after -2 min anodization and upon further anodization remains fairly constant. In parallel, the effective surface area increases by a factor of 10-30. This behavior is markedly different from the one observed previously for n-type porous Si.

  15. Improvement of photoelectrochemical hydrogen generation by surface modification of p-type silicon semiconductor photocathodes

    SciTech Connect

    Dominey, R.N.; Lewis, N.S.; Bruce, J.A.; Bookbinder, D.C.; Wrighton, M.S.

    1982-01-27

    The improvement of H/sub 2/ evolution from two different types of catalytic p-type photocathode surfaces has been examined. p-Type Si has been platinized by phtotelectrochemically plating Pt(0) onto the Si surface. Such a photocathode shows significant improvement (compared to naked p-type Si) for photochemical H/sub 2/ evolution with respect to output photovoltage, fill factor, and overall efficiency. Such photocathodes having an optimun amount of Pt(0) give a pH-dependent output voltage with respect to the H/sub 2/O/H/sub 2/ couple, but the dependence is not a simple 59-mV/pH dependence. No pH dependence would be expected if Pt(0) formed a Schottky barrier when plated onto p-type Si. A second kind of H/sub 2/ evolution catalyst has been confined to the surface of p-type Si. Polymeric quantities of an electroactive N,N'-dialkyl-4,4'-bipridinium reagent, (PQ/sup 2 +/.)/sub n/, have been confined to the surface. The Br/sup -/ counterions of the polymer are then exchanged by PtCl/sub 6//sup 2 -/. Photoreduction then yields Pt(0) dispersed in the polymer. Such a surface is again significantly improved compared to naked p-type Si with respect to H/sub 2/ evolution. A comparison of the naked p-Si, the simply platinized, and the (PQ/sup 2 +//sup ///sup +//sub n/.nPt(0))/sub surf./ system is made and contrasted to the expected behavior of an external Schottky barrier photocell driving an electrolysis cell with a Pt cathode. Experiments with n-type MoS/sub 2/, n-type Si, Pt, Au, and W cathodes functionalized with the (PQ/sup 2 +//sup ///sup +/.)sub n/.nPt(0))/sub surf./ system compared to the same surface directly platinized confirm an important difference in the mechanism of H/sub 2/ evolution catalysis for the two surface catalyst systems. p-Type Si modified with optimum amounts of Pt(0) by direct platinization appears to give improved H/sub 2/ evolution efficiency by a mechanism where the Pt(0) serves as a catalyst that does not alter the interface energetics of the

  16. Grown-in defects limiting the bulk lifetime of p-type float-zone silicon wafers

    NASA Astrophysics Data System (ADS)

    Grant, N. E.; Rougieux, F. E.; Macdonald, D.; Bullock, J.; Wan, Y.

    2015-02-01

    We investigate a recombination active grown-in defect limiting the bulk lifetime (τbulk) of high quality float-zone (FZ) p-type silicon wafers. After annealing the samples at temperatures between 80 °C and 400 °C, τbulk was found to increase from ˜500 μs to ˜1.5 ms. By isochronal annealing the p-type samples between 80 °C and 400 °C for 30 min, the annihilation energy (Eann) of the defect was determined to be 0.3 < Eann < 0.7 eV. When the annihilated samples were phosphorus gettered at 880 °C or subject to 0.2 sun illumination for 24 h, τbulk was found to degrade. However, when the samples were subsequently annealed at temperatures between 250 and 400 °C, the defect could be re-annihilated. The experimental results suggest that the defect limiting the lifetime in the p-type FZ silicon is not related to fast diffusing metallic impurities but rather to a lattice-impurity or an impurity-impurity metastable defect.

  17. Photoreduction at illuminated p-type semiconducting silicon photoelectrodes. Evidence for Fermi level pinning

    SciTech Connect

    Bocarsly, A.B.; Bookbinder, D.C.; Dominey, R.N.; Lewis, N.S.; Wrighton, M.S.

    1980-05-21

    Studies of p- and n-type Si electrodes are reported which show that semiconducting Si electrode surfaces do not allow efficient H/sub 2/ evolution in the dark (n type) or upon illumination with band gap or greater energy light (p type). The key experiment is that N,N'-dimethyl-4,4'-bipyridinium (PQ/sup 2 +/) is reversibly reduced at n-type Si in aqueous media at a pH where H/sub 2/ should be evolved at nearly the same potential, but no H/sub 2/ evolution current is observable. The PQ/sup 2+/+/.system may be useful as an electron-transfer mediator, since PQ/sup +/.can be used to effect generation of H/sub 2/ from H/sub 2/O using a heterogeneous catalyst. The PQ/sup +/.can be produced in an uphill sense by illumination of p-type Si in aqueous solutions. Studies of p-type Si in nonaqueous solvents show that PQ/sup 2 +/, PQ/sup +/., Ru(bpy)/sub 3//sup 2 +/, Ru(bpy)/sub 3//sup +/, and Ru(bpy)/sub 3//sup 0/ are all reducible upon illumination of the p-type Si. Interestingly, each species can be photoreduced at a potential approx. 500 mV more positive than at a reversible electrode in the dark. This result reveals that a p-type Si-based photoelectrochemical cell based on PQ/sup 2+/+/., PQ/sup +/l/sup 0//, Ru(bpy)/sub 3//sup 2+/+/, Ru(bpy)/sub 3//sup +/0/, or Ru(bpy)/sub 3//sup 0/-/ would all yield a common output photovoltage, despite the fact that the formal potentials for these couples vary by more than the band gap (1.1 V) of the photocathode. These data support the notion that p-type Si exhibits Fermi level pinning under the conditions employed.Surface chemistry is shown to be able to effect changes in interface kinetics for electrodes exhibiting Fermi level pinning.

  18. Macropore formation in p-type silicon: toward the modeling of morphology

    PubMed Central

    2014-01-01

    The formation of macropores in silicon during electrochemical etching processes has attracted much interest. Experimental evidences indicate that charge transport in silicon and in the electrolyte should realistically be taken into account in order to be able to describe the macropore morphology. However, up to now, none of the existing models has the requested degree of sophistication to reach such a goal. Therefore, we have undertaken the development of a mathematical model (phase-field model) to describe the motion and shape of the silicon/electrolyte interface during anodic dissolution. It is formulated in terms of the fundamental expression for the electrochemical potential and contains terms which describe the process of silicon dissolution during electrochemical attack in a hydrofluoric acid (HF) solution. It should allow us to explore the influence of the physical parameters on the etching process and to obtain the spatial profiles across the interface of various quantities of interest, such as the hole concentration, the current density, or the electrostatic potential. As a first step, we find that this model correctly describes the space charge region formed at the silicon side of the interface. PMID:25386103

  19. Macropore formation in p-type silicon: toward the modeling of morphology.

    PubMed

    Slimani, Amel; Iratni, Aicha; Henry, Hervé; Plapp, Mathis; Chazalviel, Jean-Noël; Ozanam, François; Gabouze, Noureddine

    2014-01-01

    The formation of macropores in silicon during electrochemical etching processes has attracted much interest. Experimental evidences indicate that charge transport in silicon and in the electrolyte should realistically be taken into account in order to be able to describe the macropore morphology. However, up to now, none of the existing models has the requested degree of sophistication to reach such a goal. Therefore, we have undertaken the development of a mathematical model (phase-field model) to describe the motion and shape of the silicon/electrolyte interface during anodic dissolution. It is formulated in terms of the fundamental expression for the electrochemical potential and contains terms which describe the process of silicon dissolution during electrochemical attack in a hydrofluoric acid (HF) solution. It should allow us to explore the influence of the physical parameters on the etching process and to obtain the spatial profiles across the interface of various quantities of interest, such as the hole concentration, the current density, or the electrostatic potential. As a first step, we find that this model correctly describes the space charge region formed at the silicon side of the interface. PMID:25386103

  20. Low resistance Ohmic contact to p-type crystalline silicon via nitrogen-doped copper oxide films

    NASA Astrophysics Data System (ADS)

    Zhang, Xinyu; Wan, Yimao; Bullock, James; Allen, Thomas; Cuevas, Andres

    2016-08-01

    This work explores the application of transparent nitrogen doped copper oxide (CuOx:N) films deposited by reactive sputtering to create hole-selective contacts for p-type crystalline silicon (c-Si) solar cells. It is found that CuOx:N sputtered directly onto crystalline silicon is able to form an Ohmic contact. X-ray photoelectron spectroscopy and Raman spectroscopy measurements are used to characterise the structural and physical properties of the CuOx:N films. Both the oxygen flow rate and the substrate temperature during deposition have a significant impact on the film composition, as well as on the resulting contact resistivity. After optimization, a low contact resistivity of ˜10 mΩ cm2 has been established. This result offers significant advantages over conventional contact structures in terms of carrier transport and device fabrication.

  1. High frequency characteristics and modelling of p-type 6H-silicon carbide MOS structures

    NASA Astrophysics Data System (ADS)

    Fernández, J.; Godignon, P.; Berberich, S.; Rebollo, J.; Brezeanu, G.; Millán, J.

    1996-09-01

    This paper presents the high frequency electrical characteristics and modelling of Al/SiO 2/ p-type 6HSiC structures. The oxide was thermally grown under dry conditions. Capacitance and conductance vs bias and frequency measurements have been performed in daylight and exposing the capacitors to u.v. light. The experimental Cm- Vg and Gm- Vg characteristics show hysteresis effects, which are more important when the samples are exposed to 254 nm u.v. light. This behaviour can be explained in terms of interface traps. The MOS structure modelling is based on an interface trap model in which the interface trap levels are considered to be continuously distributed in the SiC bandgap and only charge exchange between interface trap levels and the SiC bands is allowed. From this formulation and from the Gm- f characteristics, the interface state density and the interface trap time constant have been determined.

  2. Development of radiation hard edgeless detectors with current terminating structure on p-type silicon

    NASA Astrophysics Data System (ADS)

    Verbitskaya, E.; Eremin, V.; Ruggiero, G.

    2011-12-01

    The development of edgeless Si detectors was stimulated by the tasks of the total pp cross-section study in the TOTEM experiment at the Large Hadron Collider at CERN. For this, the dead region at the detector diced side should be reduced below 50 μm. This requirement is successfully realized in edgeless Si detectors with current terminating structure (CTS), which are now operating at LHC. The development of the experiment and future LHC upgrade need the elaboration of radiation hard version of edgeless Si detectors. The current investigation represents an extension in understanding on edgeless detectors operation and development of a new issue - edgeless detectors with CTS on p-type Si.

  3. Transformation of divacancies to divacancy-oxygen pairs in p-type Czochralski-silicon; mechanism of divacancy diffusion

    SciTech Connect

    Ganagona, N. Vines, L.; Monakhov, E. V.; Svensson, B. G.

    2014-01-21

    In this work, a comprehensive study on the transition of divacancy (V{sub 2}) to divacancy-oxygen (V{sub 2}O) pairs in p-type silicon has been performed with deep level transient spectroscopy (DLTS). Czochralski grown, boron doped p-type, silicon samples, with a doping concentration of 2 × 10{sup 15} cm{sup −3} and oxygen content of 7.0 ± 1.5 × 10{sup 17} cm{sup −3}, have been irradiated with 1.8 MeV protons. Isothermal annealing at temperatures in the range of 200 °C–300 °C shows a close to one-to-one correlation between the loss in the donor state of V{sub 2} and the formation of the donor state of V{sub 2}O, located at 0.23 eV above the valence band edge. A concurrent transition takes place between the single acceptor states of V{sub 2} and V{sub 2}O, as unveiled by injection of electrons through optical excitation during the trap filling sequence of the DLTS measurements. Applying the theory for diffusion limited reactions, the diffusivity of V{sub 2} in the studied p-type samples is determined to be (1.5 ± 0.7) × 10{sup −3}exp[−(1.31 ± 0.03) eV/kT] cm{sup 2}/s, and this represents the neutral charge state of V{sub 2}. Further, the data seem to favor a two-stage diffusion mechanism involving partial dissociation of V{sub 2}, although a one-stage process cannot be fully excluded.

  4. On the recombination behaviour of iron in moderately boron-doped p-type silicon

    NASA Astrophysics Data System (ADS)

    Walz, D.; Joly, J.-P.; Kamarinos, G.

    1996-04-01

    The recombination lifetime and diffusion length of intentionally iron-contaminated samples were measured by the Surface Photo Voltage (SPV) and the Elymat technique. The lifetime results from these techniques for intentionally iron-contaminated samples were analysed, in particular for the aspect of the injection-level dependency of recombination lifetime. Based on theoretical considerations, a method for the analysis of deep-level parameters combining constant photon flux SPV and Elymat measurements has been developed. This method is based on a detailed numerical analysis of the Elymat technique, including the Dember electric field, the characteristics of the laser beam, the transport parameters of the semiconductor and multilevel Shockley-Read-Hall (SRH) recombination kinetics. The results of the numerical simulation are applied to the analysis of recombination lifetime measurements on intentionally iron-contaminated samples. We compared numerical simulations and experimental results from SPV and Elymat for p-type samples using the classical acceptor level at E v +0.1 eV and the donor level of FeB pairs at E c -0.3 eV as recombination centre. Better consistency in the interpretation of the results has been found in the doping range 1014 1016 cm-3 supposing the E c -0.3 eV level as predominant recombination centre. An attempt to extract the electron and hole capture cross-sections for this defect is made.

  5. An in situ x-ray photoelectron spectroscopy study of the initial stages of rf magnetron sputter deposition of indium tin oxide on p-type Si substrate

    SciTech Connect

    Rein, M. H.; Holt, A. O.; Hohmann, M. V.; Klein, A.; Thogersen, A.; Mayandi, J.; Monakhov, E. V.

    2013-01-14

    The interface between indium tin oxide and p-type silicon is studied by in situ X-ray photoelectron spectroscopy (XPS). This is done by performing XPS without breaking vacuum after deposition of ultrathin layers in sequences. Elemental tin and indium are shown to be present at the interface, both after 2 and 10 s of deposition. In addition, the silicon oxide layer at the interface is shown to be composed of mainly silicon suboxides rather than silicon dioxide.

  6. Fabrication of p-type porous silicon nanowire with oxidized silicon substrate through one-step MACE

    NASA Astrophysics Data System (ADS)

    Li, Shaoyuan; Ma, Wenhui; Zhou, Yang; Chen, Xiuhua; Xiao, Yongyin; Ma, Mingyu; Wei, Feng; Yang, Xi

    2014-05-01

    In this paper, the simple pre-oxidization process is firstly used to treat the starting silicon wafer, and then MPSiNWs are successfully fabricated from the moderately doped wafer by one-step MACE technology in HF/AgNO3 system. The PL spectrum of MPSiNWs obtained from the oxidized silicon wafers show a large blue-shift, which can be attributed to the deep Q. C. effect induced by numerous mesoporous structures. The effects of HF and AgNO3 concentration on formation of SiNWs were carefully investigated. The results indicate that the higher HF concentration is favorable to the growth of SiNWs, and the density of SiNWs is significantly reduced when Ag+ ions concentrations are too high. The deposition behaviors of Ag+ ions on oxidized and unoxidized silicon surface were studied. According to the experimental results, a model was proposed to explain the formation mechanism of porous SiNWs by etching the oxidized starting silicon.

  7. Electron microscopy analysis of crystalline silicon islands formed on screen-printed aluminum-doped p-type silicon surfaces

    SciTech Connect

    Bock, Robert; Schmidt, Jan; Brendel, Rolf

    2008-08-15

    The origin of a not yet understood concentration peak, which is generally measured at the surface of aluminum-doped p{sup +} regions produced in a conventional screen-printing process is investigated. Our findings provide clear experimental evidence that the concentration peak is due to the microscopic structures formed at the silicon surface during the firing process. To characterize the microscopic nature of the islands (lateral dimensions of 1-3 {mu}m) and line networks of self-assembled nanostructures (lateral dimension of {<=}50 nm), transmission electron microscopy, scanning electron microscopy, scanning transmission electron microscopy, and energy dispersive x-ray analysis are combined. Aluminum inclusions are detected 50 nm below the surface of the islands and crystalline aluminum precipitates of {<=}7 nm in diameter are found within the bulk of the islands. In addition, aluminum inclusions (lateral dimension of {approx}30 nm) are found within the bulk of the self-assembled line networks.

  8. Study of nanoparticles TiO2 thin films on p-type silicon substrate using different alcoholic solvents

    NASA Astrophysics Data System (ADS)

    Muaz, A. K. M.; Hashim, U.; Arshad, M. K. Md.; Ruslinda, A. R.; Ayub, R. M.; Gopinath, Subash C. B.; Voon, C. H.; Liu, Wei-Wen; Foo, K. L.

    2016-07-01

    In this paper, sol-gel method spin coating technique is adopted to prepare nanoparticles titanium dioxide (TiO2) thin films. The prepared TiO2 sol was synthesized using titanium butoxide act as a precursor and subjected to deposited on the p-type silicon oxide (p-SiO2) and glass slide substrates under room temperature. The effect of different alcoholic solvents of methanol and ethanol on the structural, morphological, optical and electrical properties were systematically investigated. The coated TiO2 thin films were annealed in furnace at 773 K for 1 h. The structural properties of the TiO2 films were examined with X-ray Diffraction (XRD). From the XRD analysis, both solvents showing good crystallinity with anatase phase were the predominant structure. Atomic Force Microscopy (AFM) was employed to study the morphological of the thin films. The optical properties were investigated by Ultraviolet-visible (UV-Vis) spectroscopy were found that ethanol as a solvent give a higher optical transmittance if compare to the methanol solvent. The electrical properties of the nanoparticles TiO2 thin films were measured using two-point-probe technique.

  9. Giant piezoresistance of p-type nano-thick silicon induced by interface electron trapping instead of 2D quantum confinement.

    PubMed

    Yang, Yongliang; Li, Xinxin

    2011-01-01

    The p-type silicon giant piezoresistive coefficient is measured in top-down fabricated nano-thickness single-crystalline-silicon strain-gauge resistors with a macro-cantilever bending experiment. For relatively thicker samples, the variation of piezoresistive coefficient in terms of silicon thickness obeys the reported 2D quantum confinement effect. For ultra-thin samples, however, the variation deviates from the quantum-effect prediction but increases the value by at least one order of magnitude (compared to the conventional piezoresistance of bulk silicon) and the value can change its sign (e.g. from positive to negative). A stress-enhanced Si/SiO(2) interface electron-trapping effect model is proposed to explain the 'abnormal' giant piezoresistance that should be originated from the carrier-concentration change effect instead of the conventional equivalent mobility change effect for bulk silicon piezoresistors. An interface state modification experiment gives preliminary proof of our analysis. PMID:21135460

  10. XANES and IR spectroscopy study of the electronic structure and chemical composition of porous silicon on n- and p-type substrates

    SciTech Connect

    Lenshin, A. S. Kashkarov, V. M.; Seredin, P. V.; Spivak, Yu. M.; Moshnikov, V. A.

    2011-09-15

    The differences in the electronic structure and composition of porous silicon samples obtained under identical conditions of electrochemical etching on the most commonly used n- and p-type substrates with different conductivities are demonstrated by X-ray absorption near-edge spectroscopy (XANES) and Fourier transform IR spectroscopy (FTIR) methods. It is shown that significantly higher oxidation and saturation with hydrogen is observed for the porous layer on n-type substrates.

  11. Iron-boron pairing kinetics in illuminated p-type and in boron/phosphorus co-doped n-type silicon

    SciTech Connect

    Möller, Christian; Bartel, Til; Gibaja, Fabien; Lauer, Kevin

    2014-07-14

    Iron-boron (FeB) pairing is observed in the n-type region of a boron and phosphorus co-doped silicon sample which is unexpected from the FeB pair model of Kimerling and Benton. To explain the experimental data, the existing FeB pair model is extended by taking into account the electronic capture and emission rates at the interstitial iron (Fe{sub i}) trap level as a function of the charge carrier densities. According to this model, the charge state of the Fe{sub i} may be charged in n-type making FeB association possible. Further, FeB pair formation during illumination in p-type silicon is investigated. This permits the determination of the charge carrier density dependent FeB dissociation rate and in consequence allows to determine the acceptor concentration in the co-doped n-type silicon by lifetime measurement.

  12. Determination of phonon decay rate in p-type silicon under Fano resonance by measurement of coherent phonons

    NASA Astrophysics Data System (ADS)

    Kato, Keiko; Oguri, Katsuya; Sanada, Haruki; Tawara, Takehiko; Sogawa, Tetsuomi; Gotoh, Hideki

    2015-09-01

    We determine phonon decay rate by measuring the temperature dependence of coherent phonons in p-type Si under Fano resonance, where there is interference between the continuum and discrete states. As the temperature decreases, the decay rate of coherent phonons decreases, whereas that evaluated from the Raman linewidth increases. The former follows the anharmonic decay model, whereas the latter does not. The different temperature dependences of the phonon decay rate of the two methods originate from the way that the continuum state, which originates from the Fano resonance, modifies the time- and frequency-domain spectra. The observation of coherent phonons is useful for evaluating the phonon decay rate free from the interaction with the continuum state and clarifies that the anharmonic decay is dominant in p-type Si even under Fano resonance.

  13. Interface modification effect between p-type a-SiC:H and ZnO:Al in p-i-n amorphous silicon solar cells.

    PubMed

    Baek, Seungsin; Lee, Jeong Chul; Lee, Youn-Jung; Iftiquar, Sk Md; Kim, Youngkuk; Park, Jinjoo; Yi, Junsin

    2012-01-01

    Aluminum-doped zinc oxide (ZnO:Al) [AZO] is a good candidate to be used as a transparent conducting oxide [TCO]. For solar cells having a hydrogenated amorphous silicon carbide [a-SiC:H] or hydrogenated amorphous silicon [a-Si:H] window layer, the use of the AZO as TCO results in a deterioration of fill factor [FF], so fluorine-doped tin oxide (Sn02:F) [FTO] is usually preferred as a TCO. In this study, interface engineering is carried out at the AZO and p-type a-SiC:H interface to obtain a better solar cell performance without loss in the FF. The abrupt potential barrier at the interface of AZO and p-type a-SiC:H is made gradual by inserting a buffer layer. A few-nanometer-thick nanocrystalline silicon buffer layer between the AZO and a-SiC:H enhances the FF from 67% to 73% and the efficiency from 7.30% to 8.18%. Further improvements in the solar cell performance are expected through optimization of cell structures and doping levels. PMID:22257671

  14. Interface modification effect between p-type a-SiC:H and ZnO:Al in p-i-n amorphous silicon solar cells

    PubMed Central

    2012-01-01

    Aluminum-doped zinc oxide (ZnO:Al) [AZO] is a good candidate to be used as a transparent conducting oxide [TCO]. For solar cells having a hydrogenated amorphous silicon carbide [a-SiC:H] or hydrogenated amorphous silicon [a-Si:H] window layer, the use of the AZO as TCO results in a deterioration of fill factor [FF], so fluorine-doped tin oxide (Sn02:F) [FTO] is usually preferred as a TCO. In this study, interface engineering is carried out at the AZO and p-type a-SiC:H interface to obtain a better solar cell performance without loss in the FF. The abrupt potential barrier at the interface of AZO and p-type a-SiC:H is made gradual by inserting a buffer layer. A few-nanometer-thick nanocrystalline silicon buffer layer between the AZO and a-SiC:H enhances the FF from 67% to 73% and the efficiency from 7.30% to 8.18%. Further improvements in the solar cell performance are expected through optimization of cell structures and doping levels. PMID:22257671

  15. Inorganic Nano Light-Emitting Transistor: p-Type Porous Silicon Nanowire/n-Type ZnO Nanofilm.

    PubMed

    Lee, Sang Hoon; Kim, Jong Woo; Lee, Tae Il; Myoung, Jae Min

    2016-08-01

    An inorganic nano light-emitting transistor (INLET) consisting of p-type porous Si nanowires (PoSiNWs) and an n-type ZnO nanofilm was integrated on a heavily doped p-type Si substrate with a thermally grown SiO2 layer. To verify that modulation of the Fermi level of the PoSiNWs is key for switchable light emitting, I-V and electroluminescent characteristics of the INLET are investigated as a function of gate bias (V g ). As the V g is changed from 0 V to -20 V, the current level and light-emission intensity in the orange-red range increase by three and two times, respectively, with a forward bias of 20 V in the p-n junction, compared to those at a V g of 0 V. On the other hand, as the V g approaches 10 V, the current level decreases and the emission intensity is reduced and then finally switched off. This result arises from the modulation of the Fermi level of the PoSiNWs and the built-in potential at the p-n junction by the applied gate electric field. PMID:27378257

  16. Role of the buffer at the interface of intrinsic a-Si:H and p-type a-Si:H on amorphous/crystalline silicon heterojunction solar cells

    NASA Astrophysics Data System (ADS)

    Meng, Fanying; Shen, Leilei; Shi, Jianhua; Zhang, Liping; Liu, Jinning; Liu, Yucheng; Liu, Zhengxin

    2015-11-01

    We investigate the influence of the different buffer at the interface between the intrinsic a-Si:H and p-type a-Si:H layers on amorphous/crystalline silicon heterojunction (SHJ) solar cells performance. It is demonstrated that the ultrathin buffer at interface of intrinsic a-Si:H and p-type a-Si:H, obtained by H-rich plasma treatment on the initial intrinsic a-Si:H passivation layer, can significantly enhance the minority carrier lifetime and decrease the emitter saturation current density. Spectroscopic ellipsometry and Fourier transform infrared spectroscopy analyses indicate that the initial intrinsic a-Si:H films become dense and less defected as a result of the relaxation and reconstruction when they are treated during the H-rich plasma environment. Based on this finding combined with the optimization of surface texturization of the silicon wafer, this work allows us to reach very high Voc values over 730 mV without losses on fill factor, the 100 μm, 125 × 125 mm2 SHJ solar cells were fabricated with industry-compatible process, yielding the efficiency up to 22.5%.

  17. Charge states of the reactants in the hydrogen passivation of interstitial iron in P-type crystalline silicon

    NASA Astrophysics Data System (ADS)

    Sun, Chang; Liu, AnYao; Phang, Sieu Pheng; Rougieux, Fiacre E.; Macdonald, Daniel

    2015-08-01

    Significant reductions in interstitial iron (Fei) concentrations occur during annealing Fe-containing silicon wafers with silicon nitride films in the temperature range of 250 °C-700 °C. The silicon nitride films are known to release hydrogen during the annealing step. However, in co-annealed samples with silicon oxide films, which are hydrogen-lean, changes in the Fei concentrations were much less significant. The precipitation of Fei is ruled out as a possible explanation for the significant reductions. The hydrogen passivation of Fei, which is the complexing of monatomic H and isolated Fei forming a recombination-inactive hydride, is proposed as the most probable model to explain the reductions. Under the assumption that the reduction is caused by the hydrogenation of Fei, the reactants' charge states in the hydrogenation reaction are determined by two independent approaches. In the first approach, illumination is found to have a small but detectible impact on the reaction kinetics in the lower temperature range. The dominating reactants' charge states are concluded to be Fe0 + H+ as revealed by modelling the injection-dependent charge states of isolated Fei and monatomic H. In the second approach, the reaction kinetics are fitted with the Arrhenius equation over a large temperature range of 250 °C-700 °C. A reasonable fit is only obtained when assuming the reacting charge states are Fe0 + H+. This supports the conclusion on the reacting charge states and also gives a value of the activation energy of hydrogenation in the 0.7-0.8 eV range.

  18. Rectification properties of n-type nanocrystalline diamond heterojunctions to p-type silicon carbide at high temperatures

    SciTech Connect

    Goto, Masaki; Amano, Ryo; Shimoda, Naotaka; Kato, Yoshimine; Teii, Kungen

    2014-04-14

    Highly rectifying heterojunctions of n-type nanocrystalline diamond (NCD) films to p-type 4H-SiC substrates are fabricated to develop p-n junction diodes operable at high temperatures. In reverse bias condition, a potential barrier for holes at the interface prevents the injection of reverse leakage current from the NCD into the SiC and achieves the high rectification ratios of the order of 10{sup 7} at room temperature and 10{sup 4} even at 570 K. The mechanism of the forward current injection is described with the upward shift of the defect energy levels in the NCD to the conduction band of the SiC by forward biasing. The forward current shows different behavior from typical SiC Schottky diodes at high temperatures.

  19. Direct ultrasensitive electrical detection of prostate cancer biomarkers with CMOS-compatible n- and p-type silicon nanowire sensor arrays

    NASA Astrophysics Data System (ADS)

    Gao, Anran; Lu, Na; Dai, Pengfei; Fan, Chunhai; Wang, Yuelin; Li, Tie

    2014-10-01

    Sensitive and quantitative analysis of proteins is central to disease diagnosis, drug screening, and proteomic studies. Here, a label-free, real-time, simultaneous and ultrasensitive prostate-specific antigen (PSA) sensor was developed using CMOS-compatible silicon nanowire field effect transistors (SiNW FET). Highly responsive n- and p-type SiNW arrays were fabricated and integrated on a single chip with a complementary metal oxide semiconductor (CMOS) compatible anisotropic self-stop etching technique which eliminated the need for a hybrid method. The incorporated n- and p-type nanowires revealed complementary electrical response upon PSA binding, providing a unique means of internal control for sensing signal verification. The highly selective, simultaneous and multiplexed detection of PSA marker at attomolar concentrations, a level useful for clinical diagnosis of prostate cancer, was demonstrated. The detection ability was corroborated to be effective by comparing the detection results at different pH values. Furthermore, the real-time measurement was also carried out in a clinically relevant sample of blood serum, indicating the practicable development of rapid, robust, high-performance, and low-cost diagnostic systems.Sensitive and quantitative analysis of proteins is central to disease diagnosis, drug screening, and proteomic studies. Here, a label-free, real-time, simultaneous and ultrasensitive prostate-specific antigen (PSA) sensor was developed using CMOS-compatible silicon nanowire field effect transistors (SiNW FET). Highly responsive n- and p-type SiNW arrays were fabricated and integrated on a single chip with a complementary metal oxide semiconductor (CMOS) compatible anisotropic self-stop etching technique which eliminated the need for a hybrid method. The incorporated n- and p-type nanowires revealed complementary electrical response upon PSA binding, providing a unique means of internal control for sensing signal verification. The highly

  20. Electrical properties and surface morphology of electron beam evaporated p-type silicon thin films on polyethylene terephthalate for solar cells applications

    SciTech Connect

    Ang, P. C.; Ibrahim, K.; Pakhuruddin, M. Z.

    2015-04-24

    One way to realize low-cost thin film silicon (Si) solar cells fabrication is by depositing the films with high-deposition rate and manufacturing-compatible electron beam (e-beam) evaporation onto inexpensive foreign substrates such as glass or plastic. Most of the ongoing research is reported on e-beam evaporation of Si films on glass substrates to make polycrystalline solar cells but works combining both e-beam evaporation and plastic substrates are still scarce in the literature. This paper studies electrical properties and surface morphology of 1 µm electron beam evaporated Al-doped p-type silicon thin films on textured polyethylene terephthalate (PET) substrate for application as an absorber layer in solar cells. In this work, Si thin films with different doping concentrations (including an undoped reference) are prepared by e-beam evaporation. Energy dispersion X-ray (EDX) showed that the Si films are uniformly doped by Al dopant atoms. With increased Al/Si ratio, doping concentration increased while both resistivity and carrier mobility of the films showed opposite relationships. Root mean square (RMS) surface roughness increased. Overall, the Al-doped Si film with Al/Si ratio of 2% (doping concentration = 1.57×10{sup 16} atoms/cm{sup 3}) has been found to provide the optimum properties of a p-type absorber layer for fabrication of thin film Si solar cells on PET substrate.

  1. Electrical properties and surface morphology of electron beam evaporated p-type silicon thin films on polyethylene terephthalate for solar cells applications

    NASA Astrophysics Data System (ADS)

    Ang, P. C.; Ibrahim, K.; Pakhuruddin, M. Z.

    2015-04-01

    One way to realize low-cost thin film silicon (Si) solar cells fabrication is by depositing the films with high-deposition rate and manufacturing-compatible electron beam (e-beam) evaporation onto inexpensive foreign substrates such as glass or plastic. Most of the ongoing research is reported on e-beam evaporation of Si films on glass substrates to make polycrystalline solar cells but works combining both e-beam evaporation and plastic substrates are still scarce in the literature. This paper studies electrical properties and surface morphology of 1 µm electron beam evaporated Al-doped p-type silicon thin films on textured polyethylene terephthalate (PET) substrate for application as an absorber layer in solar cells. In this work, Si thin films with different doping concentrations (including an undoped reference) are prepared by e-beam evaporation. Energy dispersion X-ray (EDX) showed that the Si films are uniformly doped by Al dopant atoms. With increased Al/Si ratio, doping concentration increased while both resistivity and carrier mobility of the films showed opposite relationships. Root mean square (RMS) surface roughness increased. Overall, the Al-doped Si film with Al/Si ratio of 2% (doping concentration = 1.57×1016 atoms/cm3) has been found to provide the optimum properties of a p-type absorber layer for fabrication of thin film Si solar cells on PET substrate.

  2. Metal-insulator-semiconductor barriers with a nanometer-thick aluminum nitride insulator on p-type silicon

    SciTech Connect

    Ivanov, A. M.; Kotina, I. M.; Lasakov, M. S.; Strokan, N. B.; Tuhkonen, L. M.

    2010-08-15

    The state of the interface between p-silicon and a nanometer-thick insulator is analyzed. DLTS spectra, obtained with deep centers in the bulk of the structure and its surface states recharged, are examined. The nature of the noise as a function of the reverse bias is determined for evaluating the possibility of using the structure as a nuclear radiation detector. A conclusion is drawn that the barrier used in the structure has a higher quality when nanometer-thick aluminum nitride films are deposited by dc, rather than ac, magnetron sputtering.

  3. Development of edgeless silicon pixel sensors on p-type substrate for the ATLAS high-luminosity upgrade

    NASA Astrophysics Data System (ADS)

    Calderini, G.; Bagolini, A.; Bomben, M.; Boscardin, M.; Bosisio, L.; Chauveau, J.; Giacomini, G.; La Rosa, A.; Marchiori, G.; Zorzi, N.

    2014-11-01

    In view of the LHC upgrade for the high luminosity phase (HL-LHC), the ATLAS experiment is planning to replace the inner detector with an all-silicon system. The n-in-p bulk technology represents a valid solution for the modules of most of the layers, given the significant radiation hardness of this option and the reduced cost. The large area necessary to instrument the outer layers will demand to tile the sensors, a solution for which the inefficient region at the border of each sensor needs to be reduced to the minimum size. This paper reports on a joint R&D project by the ATLAS LPNHE Paris group and FBK Trento on a novel n-in-p edgeless planar pixel design, based on the deep-trench process available at FBK.

  4. Wide band-gap, fairly conductive p-type hydrogenated amorphous silicon carbide films prepared by direct photolysis; solar cell application

    SciTech Connect

    Yamada, A.; Kenne, J.; Konagai, M.; Takahashi, K.

    1985-02-01

    Wide optical band-gap (2.0--2.3 eV) undoped and boron-doped hydrogenated amorphous silicon carbide (a-SiC:H) films have been prepared by both direct photo and rf glow discharge (GD plasma) decomposition of pure methylsilanes or acetylene and disilane gas mixtures. The photochemically prepared p-type films showed higher dark conductivities and lower activation energies. For an optical band gap of 2.0 eV a high conductivity of 7.0 x 10/sup -5/ (S cm/sup -1/) and a low activation energy of 0.33 eV have been measured. The first trial of these wide band-gap, fairly conductive films as a window layer in a p-i-n solar cell showed the high conversion efficiency of 9.46% under AM1 insolation.

  5. Sub-band transport mechanism and switching properties for resistive switching nonvolatile memories with structure of silver/aluminum oxide/p-type silicon

    SciTech Connect

    Liu, Yanhong; Li, La; Wang, Song; Gao, Ping; Pan, Lujun; Zhang, Jialiang; Zhou, Peng; Li, Jinhua; Weng, Zhankun

    2015-02-09

    In this paper, we discuss a model of sub-band in resistive switching nonvolatile memories with a structure of silver/aluminum oxide/p-type silicon (Ag/Al{sub x}O{sub y}/p-Si), in which the sub-band is formed by overlapping of wave functions of electron-occupied oxygen vacancies in Al{sub x}O{sub y} layer deposited by atomic layer deposition technology. The switching processes exhibit the characteristics of the bipolarity, discreteness, and no need of forming process, all of which are discussed deeply based on the model of sub-band. The relationships between the SET voltages and distribution of trap levels are analyzed qualitatively. The semiconductor-like behaviors of ON-state resistance affirm the sub-band transport mechanism instead of the metal filament mechanism.

  6. Effects of trap-assisted tunneling on gate-induced drain leakage in silicon-germanium channel p-type FET for scaled supply voltages

    NASA Astrophysics Data System (ADS)

    Tiwari, Vishal A.; Divakaruni, Rama; Hook, Terence B.; Nair, Deleep R.

    2016-04-01

    Silicon-germanium is considered as an alternative channel material to silicon p-type FET (pFET) for the development of energy efficient high performance transistors for 28 nm and beyond in a high-k metal gate technology because of its lower threshold voltage and higher mobility. However, gate-induced drain leakage (GIDL) is a concern for high threshold voltage device design because of tunneling at reduced bandgap. In this work, the trap-assisted tunneling and band-to-band tunneling (BTBT) effects on GIDL is analyzed and modeled for SiGe pFETs. Experimental results and Monte Carlo simulation results reveal that the pre-halo germanium pre-amorphization implant used to contain the short channel effects contribute to GIDL at the drain sidewall in addition to GIDL due to BTBT in SiGe devices. The results are validated by comparing the experimental observations with the numerical simulation and a set of calibrated models are used to describe the GIDL mechanisms for various drain and gate bias.

  7. Fabrication and characterization of silicon nanowire p-i-n MOS gated diode for use as p-type tunnel FET

    NASA Astrophysics Data System (ADS)

    Brouzet, V.; Salem, B.; Periwal, P.; Rosaz, G.; Baron, T.; Bassani, F.; Gentile, P.; Ghibaudo, G.

    2015-11-01

    In this paper, we present the fabrication and electrical characterization of a MOS gated diode based on axially doped silicon nanowire (NW) p-i-n junctions. These nanowires are grown by chemical vapour deposition (CVD) using the vapour-liquid-solid (VLS) mechanism. NWs have a length of about 7 \\upmu {m} with 3 \\upmu {m} of doped regions (p-type and n-type) and 1 \\upmu {m} of intrinsic region. The gate stack is composed of 15 nm of hafnium dioxide ({HfO}2), 80 nm of nickel and 120 nm of aluminium. At room temperature, I_{{on}} =-52 {nA}/\\upmu {m} (V_{{DS}}=-0.5 {V}, V_{{GS}}=-4 {V}), and an I_{{on}}/I_{{off}} ratio of about 104 with a very low I_{{off}} current has been obtained. Electrical measurements are carried out between 90 and 390 K, and we show that the I on current is less temperature dependent below 250 K. We also observe that the ON current is increasing between 250 and 390 K. These transfer characteristics at low and high temperature confirm the tunnelling transport mechanisms in our devices.

  8. Reliability in Short-Channel p-Type Polycrystalline Silicon Thin-Film Transistor under High Gate and Drain Bias Stress

    NASA Astrophysics Data System (ADS)

    Choi, Sung-Hwan; Kim, Sun-Jae; Mo, Yeon-Gon; Kim, Hye-Dong; Han, Min-Koo

    2010-03-01

    We have investigated the electrical characteristics of short-channel p-type excimer laser annealed (ELA) polycrystalline silicon (poly-Si) thin-film transistors (TFTs) under high gate and drain bias stress. We found that the threshold voltage of short-channel TFTs was significantly shifted in the negative direction owing to high gate and drain bias stress (ΔVTH = -2.08 V), whereas that of long-channel TFTs was rarely shifted in the negative direction (ΔVTH = -0.10 V). This negative shift of threshold voltage in the short-channel TFT may be attributed to interface state generation near the source junction and deep trap state creation near the drain junction between the poly-Si film and the gate insulator layer. It was also found that the gate-to-drain capacitance (CGD) characteristic of the stressed TFT severely stretched for the gate voltage below the flat band voltage VFB. The effects of high gate and drain bias stress are related to hot-hole-induced donor like interface state generation. The transfer characteristics of the forward and reverse modes after the high gate and drain bias stress also indicate that the interface state generation at the gate insulator/channel interface occurred near the source junction region.

  9. Reliability in Short-Channel p-Type Polycrystalline Silicon Thin-Film Transistor under High Gate and Drain Bias Stress

    NASA Astrophysics Data System (ADS)

    Sung-Hwan Choi,; Sun-Jae Kim,; Yeon-Gon Mo,; Hye-Dong Kim,; Min-Koo Han,

    2010-03-01

    We have investigated the electrical characteristics of short-channel p-type excimer laser annealed (ELA) polycrystalline silicon (poly-Si) thin-film transistors (TFTs) under high gate and drain bias stress. We found that the threshold voltage of short-channel TFTs was significantly shifted in the negative direction owing to high gate and drain bias stress (Δ VTH = -2.08 V), whereas that of long-channel TFTs was rarely shifted in the negative direction (Δ VTH = -0.10 V). This negative shift of threshold voltage in the short-channel TFT may be attributed to interface state generation near the source junction and deep trap state creation near the drain junction between the poly-Si film and the gate insulator layer. It was also found that the gate-to-drain capacitance (CGD) characteristic of the stressed TFT severely stretched for the gate voltage below the flat band voltage VFB. The effects of high gate and drain bias stress are related to hot-hole-induced donor like interface state generation. The transfer characteristics of the forward and reverse modes after the high gate and drain bias stress also indicate that the interface state generation at the gate insulator/channel interface occurred near the source junction region.

  10. Effect of Rapid Thermal Processing on Light-Induced Degradation of Carrier Lifetime in Czochralski p-Type Silicon Bare Wafers

    NASA Astrophysics Data System (ADS)

    Kouhlane, Y.; Bouhafs, D.; Khelifati, N.; Belhousse, S.; Menari, H.; Guenda, A.; Khelfane, A.

    2016-07-01

    The electrical properties of Czochralski silicon (Cz-Si) p-type boron-doped bare wafers have been investigated after rapid thermal processing (RTP) with different peak temperatures. Treated wafers were exposed to light for various illumination times, and the effective carrier lifetime (τ eff) measured using the quasi-steady-state photoconductance (QSSPC) technique. τ eff values dropped after prolonged illumination exposure due to light-induced degradation (LID) related to electrical activation of boron-oxygen (BO) complexes, except in the sample treated with peak temperature of 785°C, for which the τ eff degradation was less pronounced. Also, a reduction was observed when using the 830°C peak temperature, an effect that was enhanced by alteration of the wafer morphology (roughness). Furthermore, the electrical resistivity presented good stability under light exposure as a function of temperature compared with reference wafers. Additionally, the optical absorption edge shifted to higher wavelength, leading to increased free-carrier absorption by treated wafers. Moreover, a theoretical model is used to understand the lifetime degradation and regeneration behavior as a function of illumination time. We conclude that RTP plays an important role in carrier lifetime regeneration for Cz-Si wafers via modification of optoelectronic and structural properties. The balance between an optimized RTP cycle and the rest of the solar cell elaboration process can overcome the negative effect of LID and contribute to achievement of higher solar cell efficiency and module performance.

  11. Silicon mitigates heavy metal stress by regulating P-type heavy metal ATPases, Oryza sativa low silicon genes, and endogenous phytohormones

    PubMed Central

    2014-01-01

    Background Silicon (Si) application has been known to enhance the tolerance of plants against abiotic stresses. However, the protective mechanism of Si under heavy metals contamination is poorly understood. The aim of this study was to assess the role of Si in counteracting toxicity due to cadmium (Cd) and copper (Cu) in rice plants (Oryza sativa). Results Si significantly improved the growth and biomass of rice plants and reduced the toxic effects of Cd/Cu after different stress periods. Si treatment ameliorated root function and structure compared with non-treated rice plants, which suffered severe root damage. In the presence of Si, the Cd/Cu concentration was significantly lower in rice plants, and there was also a reduction in lipid peroxidation and fatty acid desaturation in plant tissues. The reduced uptake of metals in the roots modulated the signaling of phytohormones involved in responses to stress and host defense, such as abscisic acid, jasmonic acid, and salicylic acid. Furthermore, the low concentration of metals significantly down regulated the mRNA expression of enzymes encoding heavy metal transporters (OsHMA2 and OsHMA3) in Si-metal-treated rice plants. Genes responsible for Si transport (OsLSi1 and OsLSi2), showed a significant up-regulation of mRNA expression with Si treatment in rice plants. Conclusion The present study supports the active role of Si in the regulation of stresses from heavy metal exposure through changes in root morphology. PMID:24405887

  12. Fabrication and characterization of n-type aluminum-boron co-doped ZnO on p-type silicon (n-AZB/p-Si) heterojunction diodes

    SciTech Connect

    Kumar, Vinod; Singh, Neetu; Kapoor, Avinashi; Ntwaeaborwa, Odireleng M.; Swart, Hendrik C.

    2013-11-15

    Graphical abstract: - Highlights: • n-AZB/p-Si heterojunction diodes were formed. • n-AZB/p-Si diode annealed at 700 °C showed best rectifying behavior. • Zn{sub 2}SiO{sub 4} was formed at 800 °C. • n and ϕ{sub b} were estimated to be 1.63 and 0.4 eV, respectively, at 700 °C. • Tailoring of BG was attributed to annealing induced stresses in the films. - Abstract: In this paper, the growth of n-type aluminum boron co-doped ZnO (n-AZB) on a p-type silicon (p-Si) substrate by sol–gel method using spin coating technique is reported. The n-AZB/p-Si heterojunctions were annealed at different temperatures ranging from 400 to 800 °C. The crystallite size of the AZB nanostructures was found to vary from 28 to 38 nm with the variation in annealing temperature. The band gap of the AZB decreased from 3.29 to 3.27 eV, with increasing annealing temperature from 400 to 700 °C and increased to 3.30 eV at 800 °C probably due to the formation of Zn{sub 2}SiO{sub 4} at the interface. The band gap variation is explained in terms of annealing induced stress in the AZB. The n-AZB/p-Si heterojunction exhibited diode behavior. The best rectifying behavior was exhibited at 700 °C.

  13. P-type ATPases.

    PubMed

    Palmgren, Michael G; Nissen, Poul

    2011-01-01

    P-type ATPases form a large superfamily of cation and lipid pumps. They are remarkably simple with only a single catalytic subunit and carry out large domain motions during transport. The atomic structure of P-type ATPases in different conformations, together with ample mutagenesis evidence, has provided detailed insights into the pumping mechanism by these biological nanomachines. Phylogenetically, P-type ATPases are divided into five subfamilies, P1-P5. These subfamilies differ with respect to transported ligands and the way they are regulated. PMID:21351879

  14. Thermodynamically uphill reduction of a surface-confined N,N'-dialkyl-4,4'-bipyridinium derivative on illuminated p-type silicon surfaces

    SciTech Connect

    Bookbinder, D.C.; Wrighton, M.S.

    1980-07-16

    Results pertaining to a chemically derivatized p-type semiconductor photocathode surface are reported. The reduced form of N,N'-dimethyl-4,4'-bipyridinium comes into rapid redox equilibrium with aqueous (pH < 6) solutions containing suspensions of Pt to evolve Hg; the H/sub 2/ evolution can also be catalyzed by hydrogenase. Included are results for derivatized Pt to establish the thermodynamics for the surface-confined reagents. Possible applications in bioelectrochemistry and in electrochronic displays with reversible electrodes functionalized with the bipyridinium reagent were noted. 2 figures. (DP)

  15. Temperature Dependent Capacitance-Voltage And Deep Level Transient Spectroscopy Study Of Self-Assembled Ge Quantum Dots Embedded In P-type Silicon

    SciTech Connect

    Rangel-Kuoppa, Victor-Tapio; Chen Gang; Jantsch, Wolfgang

    2011-12-23

    Temperature dependent Capacitance-Voltage (TCV) and Deep Level Transient Spectroscopy (DLTS) techniques were used to study how Ge Quantum Dots (QDs) embedded in Silicon trap charge. Atomic Force Microscopy (AFM) is used to obtain the density of QDs, which is in the order of 3x10{sup 11} cm{sup -2}. Three shallow levels, with activation energies of 40, 65 and 90 meV, and densities around 10{sup 16} cm{sup -3}, are found and are related to Boron. Four deep levels, with activation energies of 110, 150, 330 and 380 meV, and densities between 2x10{sup 15} cm{sup -3} and 5x10{sup 15} cm{sup -3}, are also found. TCV results suggest they are related to the Ge QDs.

  16. Ultralow Contact Resistivity for a Metal/p-Type Silicon Interface by High-Concentration Germanium and Boron Doping Combined with Low-Temperature Annealing

    NASA Astrophysics Data System (ADS)

    Murakoshi, Atsushi; Iwase, Masao; Niiyama, Hiromi; Koike, Mitsuo; Suguro, Kyoichi

    2013-07-01

    A contact resistivity of 6.9×10-9 Ω.cm2 has been obtained in an AlSi (1 wt %)-Cu (0.5 wt %) alloy/silicon system by using heavy-dose ion implantations of germanium and boron combined with low-temperature annealing. The analysis of the combined state showed that B12 cluster was incorporated and the supersaturation activation layer was formed into the region where germanium separated. Separated germanium is expected to have high interface state density. It is considered that this interface state density also has a Fermi level, and in order to reduce the difference from the Fermi level of the substrate, the charge moves to interface state density from the substrate. As a result, it is not based on a metallic material but a work function becomes small because pinning by which a Fermi level is fixed to interface state density occurs owing to the substrate/metal interface. It is considered to be attributable to the existence of a Ge-rich layer formed by low-temperature annealing, and a supersaturation activation layer that lowers contact resistance was formed.

  17. Boron-doped amorphous diamondlike carbon as a new p-type window material in amorphous silicon p-i-n solar cells

    SciTech Connect

    Lee, C.H.; Lim, K.S.

    1998-01-01

    A boron-doped hydrogenated amorphous diamondlike carbon (a-DLC:H) was prepared using a mercury-sensitized photochemical vapor deposition (photo-CVD) method. The source gases were B{sub 2}H{sub 6} and C{sub 2}H{sub 4}. By increasing the boron doping ratio (B{sub 2}H{sub 6}/C{sub 2}H{sub 4}) from 0 to 12000 ppm, the dark conductivity increased from {approximately}10{sup {minus}9} to {approximately}10{sup {minus}7} S/cm. A boron-doped a-DLC:H with an energy band gap of 3.8 eV and a dark conductivity of 1.3{times}10{sup {minus}8} S/cm was obtained at a doping ratio of 3600 ppm. By using this film, amorphous silicon (a-Si) solar cells with a novel p-a-DLC:H/p-a-SiC double p-layer structure were fabricated using the photo-CVD method and the cell photovoltaic characteristics were investigated as a function of a-DLC:H layer thickness. The open circuit voltage increased from 0.766 V for the conventional cell with a 40-{Angstrom}-thick p-a-SiC to 0.865 V for the cell with a p-a-DLC:H (15 {Angstrom})/p-a-SiC (40 {Angstrom}) double p-layer structure. The thin ({lt}15 {Angstrom}) p-a-DLC:H layer proved to be an excellent hole emitter as a wide band gap window layer. {copyright} {ital 1998 American Institute of Physics.}

  18. Simulation and study of the influence of the buffer intrinsic layer, back-surface field, densities of interface defects, resistivity of p-type silicon substrate and transparent conductive oxide on heterojunction with intrinsic thin-layer (HIT) solar cell

    SciTech Connect

    Dao, Vinh Ai; Heo, Jongkyu; Choi, Hyungwook; Kim, Yongkuk; Park, Seungman; Jung, Sungwook; Lakshminarayan, Nariangadu; Yi, Junsin

    2010-05-15

    The influence of various parameters such as buffer intrinsic layers, back-surface fields, densities of interface defects (D{sub it}), the resistivity of p-type silicon substrates ({rho}) and then work function of transparent conductive oxide ({phi}{sub TCO}) on heterojunction with intrinsic thin-layer (HIT) solar cell performance was investigated using software simulation. Automat for the simulation of heterostructures (AFORS-HET) software was used for that purpose. Our results indicate that band bending, which is determined by the band offsets at the buffer intrinsic/c-Si and/or the c-Si/back-surface field heterointerface, could be critical to solar cell performance. The effect of band bending on solar cell performance and the dependence of cell performance on {rho} and {phi}{sub TCO} were investigated in detail. Eventually, suggestive design parameters for HIT solar cell fabrication are proposed. (author)

  19. Application of Black Silicon for Nanostructure-Initiator Mass Spectrometry.

    PubMed

    Gao, Jian; de Raad, Markus; Bowen, Benjamin P; Zuckermann, Ronald N; Northen, Trent R

    2016-02-01

    Nanostructure-initiator mass spectrometry (NIMS) is a matrix-free desorption/ionization technique with high sensitivity for small molecules. Surface preparation has relied on hydrofluoric acid (HF) electrochemical etching which is undesirable given the significant safety controls required in this specialized process. In this study, we examine a conventional and widely used process for producing black silicon based on sulfur hexafluoride/oxygen (SF6/O2) inductively coupled plasma (ICP) etching at cryogenic temperatures and we find it to be suitable for NIMS. A systematic study varying parameters in the plasma etching process was performed to understand the relationship of black silicon morphology and its sensitivity as a NIMS substrate. The results suggest that a combination of higher silicon temperature and oxygen flow rate gives rise to the formation of black silicon with fine pillar structures, whose aspect ratio are ∼ 8.7 and depth are <1 μm resulting in higher NIMS sensitivity which is attributed to surface restructuring caused by their low melting point upon laser irradiation. Interestingly, we find selectivity of these black silicon substrates to different analytes depending on the etching parameters. Though, the sensitivity of the dry etching process is lower than the traditional "wet" electrochemical etching process, it is suitable for many applications and is prepared using conventional equipment without the use of HF. PMID:26741735

  20. Optical Sensing Circuit Using Low-Temperature Polycrystalline Silicon p-Type Thin-Film Transistors and p-Intrinsic-Metal Diode for Active Matrix Displays with Optical Input Functions

    NASA Astrophysics Data System (ADS)

    Lim, Han-Sin; Kwon, Oh-Kyong

    2009-03-01

    An optical sensing circuit composed of low-temperature polycrystalline silicon (LTPS) p-type thin-film transistors (TFTs) and a p-intrinsic-metal (p-i-m) diode is proposed for image scanning and touch sensing functions. Because it is a very difficult challenge to integrate both display pixels and optical sensing circuits into the restricted pixel area, the number of additional devices and control signal lines must be minimized. Therefore, two p-type TFTs, one p-i-m diode, one capacitor, and one signal line are added to display pixel for the proposed optical sensing circuit. Active matrix liquid crystal display (AMLCD) and active matrix organic light-emitting diode (AMOLED) pixels with the proposed optical sensing circuit have image scanning and touch sensing functions, respectively. Through the measurement of the proposed circuit under the condition of incident light varying from 0 to 10,000 lx, we verified that the dynamic and output ranges of the proposed circuit are 30 dB and 1.5 V, respectively.

  1. Low temperature deposition and characterization of n- and p-type silicon carbide thin films and associated ohmic and Schottky contacts. Annual report, 1 January-31 December 1992

    SciTech Connect

    Davis, R.F.; Nemanich, R.J.; Kern, R.S.; Patterson, R.; Rowland, L.B.

    1992-01-01

    Single-crystal epitaxial films of cubic Beta(3C)-SiC(111) and AlN(0001) have been deposited on alpha(6H)-SiC(OOO1) substrates oriented 3-4 deg towards 1120 at 1050 deg C via gas-source molecular beam epitaxy using disilane (Si2H6), ethylene (C2H4), thermal evaporation of Al and activated N species derived from an ECR plasma. High resolution transmission electron microscopy revealed that the nucleation and growth of the Beta(3C)-SiC regions occurred primarily on terraces between closely spaced steps. Pseudomorphic bilayer structures containing Beta(3C)-SiC and 2H-AlN have been grown under the same conditions for the first time. HREED and cross-sectional HRTEM showed all layers to be monocrystalline. Initial high temperature chemical interdiffusion studies between SiC and AIN show that all components diffuse very slowly across the interface. AHRTEM and SAS are being used to determine the concentration profiles. Thin film solid solutions of AIN and SiC have been deposited using similar techniques and conditions as the individual compounds. Metal contacts of Ti, Pt and Hf deposited at RT on n-type alpha(6H)-SiC(OOO1) exhibit rectifying behavior with ideality factors between 1.01 and 1.09. The Pt and Hf contacts had leakage currents of 5xl0-8 A/cm2 at -10V. Values of barrier heights for all contacts were within a few tenths of 1.0eV which is indicative that the Fermi level is pinned at the SiC surface.... Films, SiC, AlN, Gas source molecular beam epitaxy, Transmission electron microscopy, Chemical interdiffusion, Metal contacts, Ti, Pt, Hf, Ideality factors, Fermi level pinning.

  2. Initial stages of silicon growth on the (100) surface of silicon by localized laser CVD

    NASA Astrophysics Data System (ADS)

    Kotecki, D. E.; Herman, I. P.

    1987-12-01

    This paper reports initial results of an experimental study of the early stages of silicon thin film growth on well prepared (100) c-Si surfaces by pyrolytic deposition from silane (SiH4) during localized laser chemical vapor deposition (LLCVD). The rate of silicon thin film growth during low pressure (less than 10 Torr) deposition using tightly focussed laser beams (514.5 nm, approximately 2.5 micron FWHM) is characterized and is shown to be much slower than expected based on the previously measured silane decomposition rate. Hybrid-heating experiments, in which laser heating induces a slight temperature increase on a uniformly heated substrate in the presence of silane gas, shows that growth is inhibited within the laser irradiation region. This result suggests that a nonpyrolytic mechanism contributes to silicon growth in laser CVD. Possible explanations for this nonpyrolytic growth mechanism are discussed.

  3. Initial experience with the CDF layer 00 silicon detector

    SciTech Connect

    C. Hill

    2003-03-17

    We report on initial experience with the CDF Layer 00 Detector. Layer 00 is an innovative, low-mass, silicon detector installed in CDF during the upgrade for Run 2A of the Tevatron. Noise pickup present during operation at CDF is discussed. An event-by-event pedestal correction implemented by CDF is presented. This off-line solution prevents L00 from being used in the current incarnation of the on-line displaced track trigger. Preliminary performance of Layer 00 is described.

  4. Crystalline Silicon Short-Circuit Current Degradation Study: Initial Results

    SciTech Connect

    Osterwald, C. R.; Pruett, J.; Moriarty, T.

    2005-02-01

    Following our observation of slow degradation of short-circuit current (Isc) in crystalline silicon (x-Si) modules that was correlated with ultraviolet (UV) exposure dose, we initiated a new study of individual x-Si cells designed to determine the degradation cause. In this paper, we report the initial results of this study, which has accumulated 1056 MJ/m2 of UV dose from 1-sun metal-halide irradiance, equivalent to 3.8 years at our test site. At this time, the control samples are unchanged, the unencapsulated samples have lost about 2% of Isc, and the samples encapsulated in module-style packages have declined from 1% to 3%, depending on the cell technology.

  5. P-type gallium nitride

    DOEpatents

    Rubin, M.; Newman, N.; Fu, T.; Ross, J.; Chan, J.

    1997-08-12

    Several methods have been found to make p-type gallium nitride. P-type gallium nitride has long been sought for electronic devices. N-type gallium nitride is readily available. Discovery of p-type gallium nitride and the methods for making it will enable its use in ultraviolet and blue light-emitting diodes and lasers. pGaN will further enable blue photocathode elements to be made. Molecular beam epitaxy on substrates held at the proper temperatures, assisted by a nitrogen beam of the proper energy produced several types of p-type GaN with hole concentrations of about 5{times}10{sup 11} /cm{sup 3} and hole mobilities of about 500 cm{sup 2} /V-sec, measured at 250 K. P-type GaN can be formed of unintentionally-doped material or can be doped with magnesium by diffusion, ion implantation, or co-evaporation. When applicable, the nitrogen can be substituted with other group III elements such as Al. 9 figs.

  6. P-type gallium nitride

    DOEpatents

    Rubin, Michael; Newman, Nathan; Fu, Tracy; Ross, Jennifer; Chan, James

    1997-01-01

    Several methods have been found to make p-type gallium nitride. P-type gallium nitride has long been sought for electronic devices. N-type gallium nitride is readily available. Discovery of p-type gallium nitride and the methods for making it will enable its use in ultraviolet and blue light-emitting diodes and lasers. pGaN will further enable blue photocathode elements to be made. Molecular beam epitaxy on substrates held at the proper temperatures, assisted by a nitrogen beam of the proper energy produced several types of p-type GaN with hole concentrations of about 5.times.10.sup.11 /cm.sup.3 and hole mobilities of about 500 cm.sup.2 /V-sec, measured at 250.degree. K. P-type GaN can be formed of unintentionally-doped material or can be doped with magnesium by diffusion, ion implantation, or co-evaporation. When applicable, the nitrogen can be substituted with other group III elements such as Al.

  7. Initial Steps of Rubicene Film Growth on Silicon Dioxide

    PubMed Central

    2013-01-01

    The film growth of the conjugated organic molecule rubicene on silicon dioxide was studied in detail. Since no structural data of the condensed material were available, we first produced high quality single crystals from solution and determined the crystal structure. This high purity material was used to prepare ultrathin films under ultrahigh vacuum conditions, by physical vapor deposition. Thermal desorption spectroscopy (TDS) was applied to delineate the adsorption and desorption kinetics. It could be shown that the initial sticking coefficient is only 0.2 ± 0.05, but the sticking coefficient increases with increasing coverage. TDS further revealed that first a closed, weakly bound bilayer develops (wetting layer), which dewets after further deposition of rubicene, leading to an island-like layer. These islands are crystalline and exhibit the same structure as the solution grown crystals. The orientation of the crystallites is with the (001) plane parallel to the substrate. A dewetting of the closed bilayer was also observed when the film was exposed to air. Furthermore, Ostwald ripening of the island-like film takes place under ambient conditions, leading to films composed of few, large crystallites. From TDS, we determined the heat of evaporation from the multilayer islands to be 1.47 eV, whereas the desorption energy from the first layer is only 1.25 eV. PMID:23476720

  8. Comparative study of initial stages of copper immersion deposition on bulk and porous silicon

    PubMed Central

    2013-01-01

    Initial stages of Cu immersion deposition in the presence of hydrofluoric acid on bulk and porous silicon were studied. Cu was found to deposit both on bulk and porous silicon as a layer of nanoparticles which grew according to the Volmer-Weber mechanism. It was revealed that at the initial stages of immersion deposition, Cu nanoparticles consisted of crystals with a maximum size of 10 nm and inherited the orientation of the original silicon substrate. Deposited Cu nanoparticles were found to be partially oxidized to Cu2O while CuO was not detected for all samples. In contrast to porous silicon, the crystal orientation of the original silicon substrate significantly affected the sizes, density, and oxidation level of Cu nanoparticles deposited on bulk silicon. PMID:23414073

  9. Comparative study of initial stages of copper immersion deposition on bulk and porous silicon

    NASA Astrophysics Data System (ADS)

    Bandarenka, Hanna; Prischepa, Sergey L.; Fittipaldi, Rosalba; Vecchione, Antonio; Nenzi, Paolo; Balucani, Marco; Bondarenko, Vitaly

    2013-02-01

    Initial stages of Cu immersion deposition in the presence of hydrofluoric acid on bulk and porous silicon were studied. Cu was found to deposit both on bulk and porous silicon as a layer of nanoparticles which grew according to the Volmer-Weber mechanism. It was revealed that at the initial stages of immersion deposition, Cu nanoparticles consisted of crystals with a maximum size of 10 nm and inherited the orientation of the original silicon substrate. Deposited Cu nanoparticles were found to be partially oxidized to Cu2O while CuO was not detected for all samples. In contrast to porous silicon, the crystal orientation of the original silicon substrate significantly affected the sizes, density, and oxidation level of Cu nanoparticles deposited on bulk silicon.

  10. Plasma-initiated rehydrogenation of amorphous silicon to increase the temperature processing window of silicon heterojunction solar cells

    NASA Astrophysics Data System (ADS)

    Shi, Jianwei; Boccard, Mathieu; Holman, Zachary

    2016-07-01

    The dehydrogenation of intrinsic hydrogenated amorphous silicon (a-Si:H) at temperatures above approximately 300 °C degrades its ability to passivate silicon wafer surfaces. This limits the temperature of post-passivation processing steps during the fabrication of advanced silicon heterojunction or silicon-based tandem solar cells. We demonstrate that a hydrogen plasma can rehydrogenate intrinsic a-Si:H passivation layers that have been dehydrogenated by annealing. The hydrogen plasma treatment fully restores the effective carrier lifetime to several milliseconds in textured crystalline silicon wafers coated with 8-nm-thick intrinsic a-Si:H layers after annealing at temperatures of up to 450 °C. Plasma-initiated rehydrogenation also translates to complete solar cells: A silicon heterojunction solar cell subjected to annealing at 450 °C (following intrinsic a-Si:H deposition) had an open-circuit voltage of less than 600 mV, but an identical cell that received hydrogen plasma treatment reached a voltage of over 710 mV and an efficiency of over 19%.

  11. Initiation time of near-infrared laser-induced slip on the surface of silicon wafers

    SciTech Connect

    Choi, Sungho; Jhang, Kyung-Young

    2014-06-23

    We have determined the initiation time of laser-induced slip on a silicon wafer surface subjected to a near-infrared continuous-wave laser by numerical simulations and experiments. First, numerical analysis was performed based on the heat transfer and thermoelasticity model to calculate the resolved shear stress and the temperature-dependent yield stress. Slip initiation time was predicted by finding the time at which the resolved shear stress reached the yield stress. Experimentally, the slip initiation time was measured by using a laser scattering technique that collects scattered light from the silicon wafer surface and detects strong scattering when the surface slip is initiated. The surface morphology of the silicon wafer surface after laser irradiation was also observed using an optical microscope to confirm the occurrence of slip. The measured slip initiation times agreed well with the numerical predictions.

  12. Initiation time of near-infrared laser-induced slip on the surface of silicon wafers

    NASA Astrophysics Data System (ADS)

    Choi, Sungho; Jhang, Kyung-Young

    2014-06-01

    We have determined the initiation time of laser-induced slip on a silicon wafer surface subjected to a near-infrared continuous-wave laser by numerical simulations and experiments. First, numerical analysis was performed based on the heat transfer and thermoelasticity model to calculate the resolved shear stress and the temperature-dependent yield stress. Slip initiation time was predicted by finding the time at which the resolved shear stress reached the yield stress. Experimentally, the slip initiation time was measured by using a laser scattering technique that collects scattered light from the silicon wafer surface and detects strong scattering when the surface slip is initiated. The surface morphology of the silicon wafer surface after laser irradiation was also observed using an optical microscope to confirm the occurrence of slip. The measured slip initiation times agreed well with the numerical predictions.

  13. Initial results for the silicon monolithically interconnected solar cell product

    NASA Astrophysics Data System (ADS)

    Dinetta, L. C.; Shreve, K. P.; Cotter, J. E.; Barnett, A. M.

    1995-10-01

    This proprietary technology is based on AstroPower's electrostatic bonding and innovative silicon solar cell processing techniques. Electrostatic bonding allows silicon wafers to be permanently attached to a thermally matched glass superstrate and then thinned to final thicknesses less than 25 micron. These devices are based on the features of a thin, light-trapping silicon solar cell: high voltage, high current, light weight (high specific power) and high radiation resistance. Monolithic interconnection allows the fabrication costs on a per watt basis to be roughly independent of the array size, power or voltage, therefore, the cost effectiveness to manufacture solar cell arrays with output powers ranging from milliwatts up to four watts and output voltages ranging from 5 to 500 volts will be similar. This compares favorably to conventionally manufactured, commercial solar cell arrays, where handling of small parts is very labor intensive and costly. In this way, a wide variety of product specifications can be met using the same fabrication techniques. Prototype solar cells have demonstrated efficiencies greater than 11%. An open-circuit voltage of 5.4 volts, fill factor of 65%, and short-circuit current density of 28 mA/sq cm at AM1.5 illumination are typical. Future efforts are being directed to optimization of the solar cell operating characteristics as well as production processing. The monolithic approach has a number of inherent advantages, including reduced cost per interconnect and increased reliability of array connections. These features make this proprietary technology an excellent candidate for a large number of consumer products.

  14. Initial results for the silicon monolithically interconnected solar cell product

    NASA Technical Reports Server (NTRS)

    Dinetta, L. C.; Shreve, K. P.; Cotter, J. E.; Barnett, A. M.

    1995-01-01

    This proprietary technology is based on AstroPower's electrostatic bonding and innovative silicon solar cell processing techniques. Electrostatic bonding allows silicon wafers to be permanently attached to a thermally matched glass superstrate and then thinned to final thicknesses less than 25 micron. These devices are based on the features of a thin, light-trapping silicon solar cell: high voltage, high current, light weight (high specific power) and high radiation resistance. Monolithic interconnection allows the fabrication costs on a per watt basis to be roughly independent of the array size, power or voltage, therefore, the cost effectiveness to manufacture solar cell arrays with output powers ranging from milliwatts up to four watts and output voltages ranging from 5 to 500 volts will be similar. This compares favorably to conventionally manufactured, commercial solar cell arrays, where handling of small parts is very labor intensive and costly. In this way, a wide variety of product specifications can be met using the same fabrication techniques. Prototype solar cells have demonstrated efficiencies greater than 11%. An open-circuit voltage of 5.4 volts, fill factor of 65%, and short-circuit current density of 28 mA/sq cm at AM1.5 illumination are typical. Future efforts are being directed to optimization of the solar cell operating characteristics as well as production processing. The monolithic approach has a number of inherent advantages, including reduced cost per interconnect and increased reliability of array connections. These features make this proprietary technology an excellent candidate for a large number of consumer products.

  15. Determination of Initial Crack Strength of Silicon Die Using Acoustic Emission Technique

    NASA Astrophysics Data System (ADS)

    Chen, Pei-Chi; Su, Yen-Fu; Yang, Shin-Yueh; Liang, Steven Y.; Chiang, Kuo-Ning

    2015-07-01

    The current market demand for high-efficiency, high-performance, small-sized electronic products has focused attention on the use of three-dimensional (3D) integrated circuits (IC) in the design of electronic packaging. Silicon wafers can be ground and polished to reduce their thickness and increase the chip stacking density. However, microcracks can result from the thinning and stacking process or during use of an electronic device over time; therefore, estimation of the cracking strength is an important issue in 3D IC packaging. This research combined the ball breaker test (BBT) with an acoustic emission (AE) system to measure the allowable force on a silicon die. To estimate the initial crack strength of a silicon die, the BBT was combined with finite-element (FE) analysis. The AE system can detect the initial crack and the subsequent bulk failure of the silicon die individually, thus avoiding overestimation of the die strength. In addition, the results of the modified ball breaker test showed that edge chipping did not affect the silicon die strength. However, the failure force and silicon die strength were reduced as the surface roughness of the test specimen increased. Thus, surface roughness must be controlled in the BBT to prevent underestimation of the silicon die strength.

  16. Optical initiation of nanoporous energetic silicon for safing and arming technologies

    NASA Astrophysics Data System (ADS)

    Churaman, Wayne A.; Becker, Collin R.; Metcalfe, Grace D.; Hanrahan, Brendan M.; Currano, Luke J.; Stoldt, Conrad R.

    2010-08-01

    Nanoporous silicon, commonly recognized for its photoluminescent properties, has gained attention as a new energetic material capable of energy density more than twice that of TNT. The addition of an oxidizer solution to inert nanoporous silicon results in an exothermic reaction when heat, friction, or focused light is supplied to the system. The energetic material can be integrated alongside microelectronics and micro-electro-mechanical systems (MEMS) for on-chip applications. This integration capability, along with the potential for large energetic yield, makes nanoporous energetic silicon a viable material for developing novel MEMS Safing and Arming (S&A) technologies. While ignition of nanoporous energetic silicon has been demonstrated for the purpose of propagation velocity measurements using a YAG laser, in this paper we show optical ignition for potential integration of the energetic with a miniaturized S&A device. Ignition is demonstrated using a 514nm laser at 37.7mW and a power density of 2.7kW/cm2 at a stand-off distance of 23cm. Raman spectroscopy verifies that significant stress in porous silicon is produced by a laser operating near the power density observed to ignite porous silicon. Lastly, we integrate the nanoporous energetic silicon with a MEMS S&A, and demonstrate transfer to a firetrain consisting of one primary and one secondary explosive using a thermal initiator to ignite the nanoporous energetic silicon.

  17. Silicon microchannel plates: initial results for photon counting detectors

    NASA Astrophysics Data System (ADS)

    Siegmund, Oswald H.; Tremsin, Anton S.; Vallerga, John V.; Beetz, Charles P.; Boerstler, Robert W.; Winn, D. R.

    2000-12-01

    The emergence of Silicon based microchannel plates (MCP's) has been awaited for a number of years, with many proposed advantages over standard glass MCPs for space-based detectors. Si should have a very low inherent background (< 0.01 events sec-1 cm-2), as well as being a low Z element with low stopping power for x, gamma and cosmic rays. The surface is oxidized and can be baked to very high temperatures (> 800 degrees Celsius), and will not react with photocathodes deposited on the surface. This could potentially allow opaque photocathodes, with their higher resolution and efficiency, to be used in the near UV/optical bands. Since the microchannel positions are determined photolithographically, the pattern will be uniform and coherent, resulting in more uniform flat fields and less differential non-linearity in the spatial response. Microchannel spacing could decrease to the micron regime, while size formats could increase. The potential advantages of Si MCPs encompass increased gain, stability, longevity, event rate, and QE. However, glass MCPs have a strong and successful heritage in space-based detector systems and the advantages of Si MCP's must be demonstrated in the laboratory before being considered for flight applications. We have tested some newly developed silicon (Si) MCP's provided by Nanosciences Corp. Although these are still in the developmental stage we have achieved a number of significant results. The gain, pulse height, response and gain uniformity, and quantum detection efficiency are very similar to glass MCP's. However the Si MCP background is approximately 0.02 events sec-1 cm-2 without shielding, a significant improvement over even low noise MCP's. The small samples we have tested are 25 mm format with 8 micrometer pore spacing, but they are taken from a 75 mm substrate, which offers the possibility of large MCP's in the near future. More testing and process development are underway to probe other operational parameters and optimize the

  18. Surface-initiated hyperbranched polyglycerol as an ultralow-fouling coating on glass, silicon, and porous silicon substrates.

    PubMed

    Moore, Eli; Delalat, Bahman; Vasani, Roshan; McPhee, Gordon; Thissen, Helmut; Voelcker, Nicolas H

    2014-09-10

    Anionic ring-opening polymerization of glycidol was initiated from activated glass, silicon, and porous silicon substrates to yield thin, ultralow-fouling hyperbranched polyglycerol (HPG) graft polymer coatings. Substrates were activated by deprotonation of surface-bound silanol functionalities. HPG polymerization was initiated upon the addition of freshly distilled glycidol to yield films in the nanometer thickness range. X-ray photoelectron spectroscopy, contact angle measurements, and ellipsometry were used to characterize the resulting coatings. The antifouling properties of HPG-coated surfaces were evaluated in terms of protein adsorption and the attachment of mammalian cells. The adsorption of bovine serum albumin and collagen type I was found to be reduced by as much as 97 and 91%, respectively, in comparison to untreated surfaces. Human glioblastoma and mouse fibroblast attachment was reduced by 99 and 98%, respectively. HPG-grafted substrates outperformed polyethylene glycol (PEG) grafted substrates of comparable thickness under the same incubation conditions. Our results demonstrate the effectiveness of antifouling HPG graft polymer coatings on a selected range of substrate materials and open the door for their use in biomedical applications. PMID:25137525

  19. Effect of Indenter Elastic Modulus on Hertzian Ring Crack Initiation in Silicon Carbide

    SciTech Connect

    Wereszczak, Andrew A; Daloz, William L; Strong, Kevin T; Jadaan, Osama M.

    2011-01-01

    The effect of spherical indenter stiffness on Hertzian-contact-induced fracture initiation was examined in hot-pressed silicon carbides (SiCs). Hertzian ring crack initiation forces were measured using zirconia, steel, silicon nitride, alumina, or tungsten carbide spherical indenters (elastic moduli ranging between 213 and 630 GPa). The two (flat target) SiCs were fully dense, and had equivalent elastic moduli (~450 GPa) and fracture toughnesses; however, about 20% of the grains in one SiC were larger than the largest grains in the other. Decreasing the indenter elastic modulus consistently resulted in lower ring crack initiation forces and those differences were statistically significant. Such a decrease in Hertzian ring crack initiation force with decreased indenter elastic modulus indicates the presence of a non-zero friction coefficient. Additionally, independent of the indenter material, ring crack initiation occurred at lower Hertzian indentation forces in the SiC containing larger grains suggesting that the grains in that tail of the grain-size-distribution acted as Griffith-type flaws. Lastly, selecting a spherical indenter material that has the same or similar elastic modulus as the target material provides simpler interpretation, and estimates of ring crack initiation stresses with greater usefulness and fidelity. Such a "matched" condition serves to circumvent the complexities that a ubiquitously unknown coefficient of friction introduces in the estimation of Hertzian ring crack initiation stress.

  20. composite and p-type Si

    NASA Astrophysics Data System (ADS)

    Lin, Yow-Jon; Yang, Shih-Hung

    2014-07-01

    The present work reports the fabrication and detailed electrical properties of heterojunction diodes based on p-type Si and the reduced graphene oxide-based TiO2 (TiO2:RGO) composite. The enhanced dark conductivity was observed for TiO2:RGO composite films. The improved electrical conductivity is considered to mainly come from the mobility enhancement. The TiO2/p-type Si diode shows a poor rectifying behavior and low photoresponse. This is because of the dominance of electron traps in TiO2. However, the TiO2:RGO/p-type Si diode shows a good rectifying behavior and high photoresponse, which is attributed to high-mobility electron transport combined with the reduced number of electron traps.

  1. p-type transparent conducting oxides

    NASA Astrophysics Data System (ADS)

    Sheng, Su; Fang, Guojia; Li, Chun; Xu, Sheng; Zhao, Xingzhong

    2006-06-01

    The recent advance of p-type transparent conductive oxide thin films is reviewed. The focus is on p-type transparent oxide semiconductors CuAlO2, CuGaO2, CuInO2, SrCu2O2, and LaCuOCh (Ch = chalcogen). These materials and related device applications are then shown as examples. Room temperature operation of current injection emission from ultraviolet light-emitting diodes based on p-SCO/n-ZnO p-n junctions has been demonstrated. This changed with the discovery of p-type transparent conducting oxides, thereby opening up the possibility for all-oxide transparent electronics.

  2. Single electron transistor with P-type sidewall spacer gates.

    PubMed

    Lee, Jung Han; Li, Dong Hua; Lee, Joung-Eob; Kang, Kwon-Chil; Kim, Kyungwan; Park, Byung-Gook

    2011-07-01

    A single-electron transistor (SET) is one of the promising solutions to overcome the scaling limit of the Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET). Up to now, various kinds of SETs are being proposed and SETs with a dual gate (DG) structure using an electrical potential barrier have been demonstrated for room temperature operation. To operate DG-SETs, however, extra bias of side gates is necessary. It causes new problems that the electrode for side gates and the extra bias for electrical barrier increase the complexity in circuit design and operation power consumption, respectively. For the reason, a new mechanism using work function (WF) difference is applied to operate a SET at room temperature by three electrodes. Its structure consists of an undoped active region, a control gate, n-doped source/drain electrodes, and metal/silicide or p-type silicon side gates, and a SET with metal/silicide gates or p-type silicon gates forms tunnel barriers induced by work function between an undoped channel and grounded side gates. Via simulation, the effectiveness of the new mechanism is confirmed through various silicide materials that have different WF values. Furthermore, by considering the realistic conditions of the fabrication process, SET with p-type sidewall spacer gates was designed, and its brief fabrication process was introduced. The characteristics of its electrical barrier and the controllability of its control gate were also confirmed via simulation. Finally, a single-hole transistor with n-type sidewall spacer gates was designed. PMID:22121580

  3. Synthesis and photo-initiated polymerization of silicon-containing hybrid monomers

    NASA Astrophysics Data System (ADS)

    Fang, Yuan; Zou, Yingquan

    2011-04-01

    A series of silicon-containing hybrid monomers which contained both vinyl ether group and allyl ether group had been synthesized. The monomers' photo-polymerization kinetics was investigated with RTIR. Results showed that the hybrid monomers could photo-polymerize effectively and both free radical and cationic polymerization processes were improved. When PAG201 (a kind of cationic photo-initiator) was introduced into the monomers, the conversion of vinyl ether double bond increased sharply. The final conversion was close to 100%, and at the 6 sec, the polymerization achieved maximum. At the same time, the allyl ether double bond left. When 2-Isopropylthioxanthone (ITX, a kind of free radical photo-initiator) was introduced into hybrid system containing PAG201, the final conversion of allyl ether double bond and polymerization rate (Rp) increased obviously. It was demonstrated that the hybrid silicon-containing monomers polymerized rapidly and completely with both of the free radical and cationic photo-initiators. The property showed that the five monomers can be used in nanoimprint resist system or UV imaging materials.

  4. 3-D patterning of silicon by laser-initiated, liquid-assisted colloidal (LILAC) lithography.

    PubMed

    Ulmeanu, M; Grubb, M P; Jipa, F; Quignon, B; Ashfold, M N R

    2015-06-01

    We report a comprehensive study of laser-initiated, liquid-assisted colloidal (LILAC) lithography, and illustrate its utility in patterning silicon substrates. The method combines single shot laser irradiation (frequency doubled Ti-sapphire laser, 50fs pulse duration, 400nm wavelength) and medium-tuned optical near-field effects around arrays of silica colloidal particles to achieve 3-D surface patterning of silicon. A monolayer (or multilayers) of hexagonal close packed silica colloidal particles act as a mask and offer a route to liquid-tuned optical near field enhancement effects. The resulting patterns are shown to depend on the difference in refractive index of the colloidal particles (ncolloid) and the liquid (nliquid) in which they are immersed. Two different topographies are demonstrated experimentally: (a) arrays of bumps, centred beneath the original colloidal particles, when using liquids with nliquidncolloid - and explained with the aid of complementary Mie scattering simulations. The LILAC lithography technique has potential for rapid, large area, organized 3-D patterning of silicon (and related) substrates. PMID:25465198

  5. Characterisation of porous silicon/poly(L-lactide) composites prepared using surface initiated ring opening polymerisation

    NASA Astrophysics Data System (ADS)

    McInnes, Steven; Thissen, Helmut; Choudhury, Namita R.; Voelcker, Nicolas H.

    2006-01-01

    Inorganic/organic hybrid or composite materials have in the past shown novel and interesting properties, which are not observed for the individual components. In this context, the preparation of inorganic/polymeric composites from biodegradable and biocompatible constituents is a new concept, which may be of interest particularly for tissue engineering and drug delivery applications. We describe here the synthesis of nanostructured porous silicon (pSi) and poly(L-lactide) (PLLA) composites. The composites were produced using tin(II) 2-ethylhexanoate catalysed surface initiated ring opening polymerisation of L-lactide onto silanised porous silicon films and microparticles. The subsequent chemical, physiochemical and morphological characterisation was performed using Diffuse Reflectance Infrared Spectroscopy (DRIFTS), X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM), Differential Scanning Calorimetery (DSC), Thermogravimetric Analysis (TGA) and Contact Angle measurements. DRIFT spectra of the composites showed the presence of bands corresponding to ester carbonyl stretching vibrations as well as hydrocarbon stretching vibrations. XPS analysis confirmed that a layer of PLLA had been grafted onto pSi judging by the low Si content (ca. 3%) and O/C ratio close to that found for PLLA homopolymers. Comparison of the sessile drop contact angle produced by silanised pSi and PLLA grafted onto pSi showed an increase of ca. 40°. This is comparable to the increase in contact angle seen between blank silicon and spin-coated PLLA of ca. 44°. The AFM surface roughness after surface initiated polymerisation increased significantly and AFM images showed the formation of PLLA nanobrushes.

  6. Initial growth on microcrystalline silicon on atomically flat hetero-substrate

    SciTech Connect

    Saitoh, K.; Kondo, M.; Matsuda, A.

    1997-07-01

    Initial growth of microcrystalline silicon ({micro}c-Si:H) deposited on an atomically flat GaAs (001) wafer using a RF glow-discharge decomposition of hydrogen diluted monosilane gas mixture has been studied by means of atomic force microscope (AFM), Auger electron spectroscopy (AES), and cross-sectional transmission electron microscopy (XTEM). It is shown that the initial growth of {micro}c-Si:H deposited at a substrate temperature of 50--250 C consists of four successive stages, i.e., (1) a layer-by-layer growth of a-Si:H up to d {approximately}5 {angstrom}, (2) island formation of a-Si:H, (3) the coalescence of the islands and the nucleation of microcrystalline at d{approximately}10{approximately}40 {angstrom} depending on the growth temperature, and (4) a rapid roughening with microcrystalline growth.

  7. Computational Classification of P-Type ATPases.

    PubMed

    Søndergaard, Dan; Knudsen, Michael; Pedersen, Christian Nørgaard Storm

    2016-01-01

    Analysis of sequence data is inevitable in modern molecular biology, and important information about for example proteins can be inferred efficiently using computational methods. Here, we explain how to use the information in freely available databases together with computational methods for classification and motif detection to assess whether a protein sequence corresponds to a P-type ATPase (and if so, which subtype) or not. PMID:26695056

  8. Evolution of Plant P-Type ATPases

    PubMed Central

    Pedersen, Christian N. S.; Axelsen, Kristian B.; Harper, Jeffrey F.; Palmgren, Michael G.

    2012-01-01

    Five organisms having completely sequenced genomes and belonging to all major branches of green plants (Viridiplantae) were analyzed with respect to their content of P-type ATPases encoding genes. These were the chlorophytes Ostreococcus tauri and Chlamydomonas reinhardtii, and the streptophytes Physcomitrella patens (a non-vascular moss), Selaginella moellendorffii (a primitive vascular plant), and Arabidopsis thaliana (a model flowering plant). Each organism contained sequences for all five subfamilies of P-type ATPases. Whereas Na+ and H+ pumps seem to mutually exclude each other in flowering plants and animals, they co-exist in chlorophytes, which show representatives for two kinds of Na+ pumps (P2C and P2D ATPases) as well as a primitive H+-ATPase. Both Na+ and H+ pumps also co-exist in the moss P. patens, which has a P2D Na+-ATPase. In contrast to the primitive H+-ATPases in chlorophytes and P. patens, the H+-ATPases from vascular plants all have a large C-terminal regulatory domain as well as a conserved Arg in transmembrane segment 5 that is predicted to function as part of a backflow protection mechanism. Together these features are predicted to enable H+ pumps in vascular plants to create large electrochemical gradients that can be modulated in response to diverse physiological cues. The complete inventory of P-type ATPases in the major branches of Viridiplantae is an important starting point for elucidating the evolution in plants of these important pumps. PMID:22629273

  9. Synthesis of Poly-Silicon Thin Films on Glass Substrate Using Laser Initiated Metal Induced Crystallization of Amorphous Silicon for Space Power Application

    NASA Technical Reports Server (NTRS)

    Abu-Safe, Husam H.; Naseem, Hameed A.; Brown, William D.

    2007-01-01

    Poly-silicon thin films on glass substrates are synthesized using laser initiated metal induced crystallization of hydrogenated amorphous silicon films. These films can be used to fabricate solar cells on low cost glass and flexible substrates. The process starts by depositing 200 nm amorphous silicon films on the glass substrates. Following this, 200 nm of sputtered aluminum films were deposited on top of the silicon layers. The samples are irradiated with an argon ion cw laser beam for annealing. Laser power densities ranging from 4 to 9 W/cm2 were used in the annealing process. Each area on the sample is irradiated for a different exposure time. Optical microscopy was used to examine any cracks in the films and loss of adhesion to the substrates. X-Ray diffraction patterns from the initial results indicated the crystallization in the films. Scanning electron microscopy shows dendritic growth. The composition analysis of the crystallized films was conducted using Energy Dispersive x-ray Spectroscopy. The results of poly-silicon films synthesis on space qualified flexible substrates such as Kapton are also presented.

  10. Gradient Poly(styrene-co-polyglycidol) Grafts via Silicon Surface-Initiated AGET ATRP.

    PubMed

    Gosecka, Monika; Pietrasik, Joanna; Decorse, Philippe; Glebocki, Bartosz; Chehimi, Mohamed M; Slomkowski, Stanislaw; Basinska, Teresa

    2015-05-01

    Gradient copolymer grafts of styrene and α-tert-butoxy-ω-vinylbenzyl-poly(glycidol ethoxyethyl ether) (PGLet), a precursor of α-tert-butoxy-ω-vinylbenzyl-polyglycidol macromonomer (PGL), were prepared on silicon wafers via a surface-initiated activator generated by electron transfer radical polymerization (AGET ATRP). Silicon plates with previously attached 2-bromoisobutyrate served as a macroinitiator for the AGET ATRP (activator generated by electron transfer) of styrene and PGLet. The copolymers' gradient P(S-co-PPGL) of composition and thickness was obtained by a simple method where the plates were slowly removed from reaction mixture using a step motor. PGLet was added continuously (dropwise) into the reactor during withdrawal of the plates from solution in order to increase the relative concentration of PGLet in polymerization mixture. A range of strategies of making grafts was tested. The plates with copolymers grafts were analyzed by various techniques, like XPS, ellipsometry, and FTIR spectroscopy. The results indicate that the AGET ATRP process is dependent on the styrene/PGLet macromonomer ratio in the polymerization mixture. Under optimal conditions, the addition of PGLet during polymerization and subsequent deprotection of hydroxyl groups of PGLet permit to obtain plates with a novel copolymer layer with composition, thickness, and wettability gradient. Plates with chemical composition of copolymer grafts gradient served as versatile supports with controlled hydrophilic/hydrophobic area and were suitable for tailored deposition of particles. PMID:25871942

  11. All-Optical Initialization, Readout, and Coherent Preparation of Single Silicon-Vacancy Spins in Diamond

    NASA Astrophysics Data System (ADS)

    Rogers, Lachlan J.; Jahnke, Kay D.; Metsch, Mathias H.; Sipahigil, Alp; Binder, Jan M.; Teraji, Tokuyuki; Sumiya, Hitoshi; Isoya, Junichi; Lukin, Mikhail D.; Hemmer, Philip; Jelezko, Fedor

    2014-12-01

    The silicon-vacancy (SiV- ) color center in diamond has attracted attention because of its unique optical properties. It exhibits spectral stability and indistinguishability that facilitate efficient generation of photons capable of demonstrating quantum interference. Here we show optical initialization and readout of electronic spin in a single SiV- center with a spin relaxation time of T1=2.4 ±0.2 ms . Coherent population trapping (CPT) is used to demonstrate coherent preparation of dark superposition states with a spin coherence time of T2⋆=35 ±3 ns . This is fundamentally limited by orbital relaxation, and an understanding of this process opens the way to extend coherence by engineering interactions with phonons. Hyperfine structure is observed in CPT measurements with the Si 29 isotope which allows access to nuclear spin. These results establish the SiV- center as a solid-state spin-photon interface.

  12. Neutron-irradiation creep of silicon carbide materials beyond the initial transient

    NASA Astrophysics Data System (ADS)

    Koyanagi, Takaaki; Katoh, Yutai; Ozawa, Kazumi; Shimoda, Kazuya; Hinoki, Tatsuya; Snead, Lance L.

    2016-09-01

    Irradiation creep beyond the transient regime was investigated for various silicon carbide (SiC) materials. The materials examined included polycrystalline or monocrystalline high-purity SiC, nanopowder sintered SiC, highly crystalline and near-stoichiometric SiC fibers (including Hi-Nicalon Type S, Tyranno SA3, isotopically-controlled Sylramic and Sylramic-iBN fibers), and a Tyranno SA3 fiber-reinforced SiC matrix composite fabricated through a nano-infiltration transient eutectic phase process. Neutron irradiation experiments for bend stress relaxation tests were conducted at irradiation temperatures ranging from 430 to 1180 °C up to 30 dpa with initial bend stresses of up to ∼1 GPa for the fibers and ∼300 MPa for the other materials. Initial bend stress in the specimens continued to decrease from 1 to 30 dpa. Analysis revealed that (1) the stress exponent of irradiation creep above 1 dpa is approximately unity, (2) the stress normalized creep rate is ∼1 × 10-7 [dpa-1 MPa-1] at 430-750 °C for the range of 1-30 dpa for most polycrystalline SiC materials, and (3) the effects on irradiation creep of initial microstructures-such as grain boundary, crystal orientation, and secondary phases-increase with increasing irradiation temperature.

  13. Neutron-irradiation creep of silicon carbide materials beyond the initial transient

    DOE PAGESBeta

    Katoh, Yutai; Ozawa, Kazumi; Shimoda, Kazuya; Hinoki, Tatsuya; Snead, Lance Lewis; Koyanagi, Takaaki

    2016-06-04

    Irradiation creep beyond the transient regime was investigated for various silicon carbide (SiC) materials. Here, the materials examined included polycrystalline or monocrystalline high-purity SiC, nanopowder sintered SiC, highly crystalline and near-stoichiometric SiC fibers (including Hi-Nicalon Type S, Tyranno SA3, isotopically-controlled Sylramic and Sylramic-iBN fibers), and a Tyranno SA3 fiber–reinforced SiC matrix composite fabricated through a nano-infiltration transient eutectic phase process. Neutron irradiation experiments for bend stress relaxation tests were conducted at irradiation temperatures ranging from 430 to 1180 °C up to 30 dpa with initial bend stresses of up to ~1 GPa for the fibers and ~300 MPa for themore » other materials. Initial bend stress in the specimens continued to decrease from 1 to 30 dpa. Analysis revealed that (1) the stress exponent of irradiation creep above 1 dpa is approximately unity, (2) the stress normalized creep rate is ~1 × 10–7 [dpa–1 MPa–1] at 430–750 °C for the range of 1–30 dpa for most polycrystalline SiC materials, and (3) the effects on irradiation creep of initial microstructures—such as grain boundary, crystal orientation, and secondary phases—increase with increasing irradiation temperature.« less

  14. P-type transparent conducting oxides

    NASA Astrophysics Data System (ADS)

    Zhang, Kelvin H. L.; Xi, Kai; Blamire, Mark G.; Egdell, Russell G.

    2016-09-01

    Transparent conducting oxides constitute a unique class of materials combining properties of electrical conductivity and optical transparency in a single material. They are needed for a wide range of applications including solar cells, flat panel displays, touch screens, light emitting diodes and transparent electronics. Most of the commercially available TCOs are n-type, such as Sn doped In2O3, Al doped ZnO, and F doped SnO2. However, the development of efficient p-type TCOs remains an outstanding challenge. This challenge is thought to be due to the localized nature of the O 2p derived valence band which leads to difficulty in introducing shallow acceptors and large hole effective masses. In 1997 Hosono and co-workers (1997 Nature 389 939) proposed the concept of ‘chemical modulation of the valence band’ to mitigate this problem using hybridization of O 2p orbitals with close-shell Cu 3d 10 orbitals. This work has sparked tremendous interest in designing p-TCO materials together with deep understanding the underlying materials physics. In this article, we will provide a comprehensive review on traditional and recently emergent p-TCOs, including Cu+-based delafossites, layered oxychalcogenides, nd 6 spinel oxides, Cr3+-based oxides (3d 3) and post-transition metal oxides with lone pair state (ns 2). We will focus our discussions on the basic materials physics of these materials in terms of electronic structures, doping and defect properties for p-type conductivity and optical properties. Device applications based on p-TCOs for transparent p–n junctions will also be briefly discussed.

  15. P-type transparent conducting oxides.

    PubMed

    Zhang, Kelvin H L; Xi, Kai; Blamire, Mark G; Egdell, Russell G

    2016-09-28

    Transparent conducting oxides constitute a unique class of materials combining properties of electrical conductivity and optical transparency in a single material. They are needed for a wide range of applications including solar cells, flat panel displays, touch screens, light emitting diodes and transparent electronics. Most of the commercially available TCOs are n-type, such as Sn doped In2O3, Al doped ZnO, and F doped SnO2. However, the development of efficient p-type TCOs remains an outstanding challenge. This challenge is thought to be due to the localized nature of the O 2p derived valence band which leads to difficulty in introducing shallow acceptors and large hole effective masses. In 1997 Hosono and co-workers (1997 Nature 389 939) proposed the concept of 'chemical modulation of the valence band' to mitigate this problem using hybridization of O 2p orbitals with close-shell Cu 3d (10) orbitals. This work has sparked tremendous interest in designing p-TCO materials together with deep understanding the underlying materials physics. In this article, we will provide a comprehensive review on traditional and recently emergent p-TCOs, including Cu(+)-based delafossites, layered oxychalcogenides, nd (6) spinel oxides, Cr(3+)-based oxides (3d (3)) and post-transition metal oxides with lone pair state (ns (2)). We will focus our discussions on the basic materials physics of these materials in terms of electronic structures, doping and defect properties for p-type conductivity and optical properties. Device applications based on p-TCOs for transparent p-n junctions will also be briefly discussed. PMID:27459942

  16. Development of n+-in-p large-area silicon microstrip sensors for very high radiation environments - ATLAS12 design and initial results

    NASA Astrophysics Data System (ADS)

    Unno, Y.; Edwards, S. O.; Pyatt, S.; Thomas, J. P.; Wilson, J. A.; Kierstead, J.; Lynn, D.; Carter, J. R.; Hommels, L. B. A.; Robinson, D.; Bloch, I.; Gregor, I. M.; Tackmann, K.; Betancourt, C.; Jakobs, K.; Kuehn, S.; Mori, R.; Parzefall, U.; Wiik-Fucks, L.; Clark, A.; Ferrere, D.; Gonzalez Sevilla, S.; Ashby, J.; Blue, A.; Bates, R.; Buttar, C.; Doherty, F.; Eklund, L.; McMullen, T.; McEwan, F.; O`Shea, V.; Kamada, S.; Yamamura, K.; Ikegami, Y.; Nakamura, K.; Takubo, Y.; Nishimura, R.; Takashima, R.; Chilingarov, A.; Fox, H.; Affolder, A. A.; Allport, P. P.; Casse, G.; Dervan, P.; Forshaw, D.; Greenall, A.; Wonsak, S.; Wormald, M.; Cindro, V.; Kramberger, G.; Mandic, I.; Mikuz, M.; Gorelov, I.; Hoeferkamp, M.; Palni, P.; Seidel, S.; Taylor, A.; Toms, K.; Wang, R.; Hessey, N. P.; Valencic, N.; Arai, Y.; Hanagaki, K.; Dolezal, Z.; Kodys, P.; Bohm, J.; Mikestikova, M.; Bevan, A.; Beck, G.; Ely, S.; Fadeyev, V.; Galloway, Z.; Grillo, A. A.; Martinez-McKinney, F.; Ngo, J.; Parker, C.; Sadrozinski, H. F.-W.; Schumacher, D.; Seiden, A.; French, R.; Hodgson, P.; Marin-Reyes, H.; Parker, K.; Paganis, S.; Jinnouchi, O.; Motohashi, K.; Todome, K.; Yamaguchi, D.; Hara, K.; Hagihara, M.; Garcia, C.; Jimenez, J.; Lacasta, C.; Marti i Garcia, S.; Soldevila, U.

    2014-11-01

    We have been developing a novel radiation-tolerant n+-in-p silicon microstrip sensor for very high radiation environments, aiming for application in the high luminosity large hadron collider. The sensors are fabricated in 6 in., p-type, float-zone wafers, where large-area strip sensor designs are laid out together with a number of miniature sensors. Radiation tolerance has been studied with ATLAS07 sensors and with independent structures. The ATLAS07 design was developed into new ATLAS12 designs. The ATLAS12A large-area sensor is made towards an axial strip sensor and the ATLAS12M towards a stereo strip sensor. New features to the ATLAS12 sensors are two dicing lines: standard edge space of 910 μm and slim edge space of 450 μm, a gated punch-through protection structure, and connection of orphan strips in a triangular corner of stereo strips. We report the design of the ATLAS12 layouts and initial measurements of the leakage current after dicing and the resistivity of the wafers.

  17. Molecular dynamics simulation on the initial stage of 1 eV carbon deposition on silicon

    NASA Astrophysics Data System (ADS)

    Philipp, Patrick; Jana, Arindam; Briquet, Ludovic G. V.; Wirtz, Tom; Henrion, Gérard

    2015-07-01

    The deposition process of 1 eV carbon on silicon has been investigated by molecular dynamics (MD) simulations up to a fluence of 5.3   ×   1014 atoms cm-2 which corresponds more or less to monolayer coverage. At such low impact energies, atoms are expected to stay on the sample surface, which is also observed up to a fluence of 2   ×   1014 atoms cm-2. For higher fluence, carbon atoms start mixing into the silicon substrate. This process seems to get initiated by the increasing strain caused by the carbon atoms deposited on the silicon surface, and which leads to some gradual distortions. The latter are important for the migration of carbon atoms into the silicon lattice. During the whole process the top part of the silicon sample gets amorphized and the coordination of the carbon atoms increases from 1 or 2 to mostly 4-fold coordinated carbon atoms. The process can be considered as the starting point of silicon carbide formation and allows to explain how nm thick films can be formed from 1 eV deposition energies. The low carbon concentration of about 7% in the modified layer is, however, too low to observe a transition towards the latter.

  18. All-optical initialization, readout, and coherent preparation of single silicon-vacancy spins in diamond.

    PubMed

    Rogers, Lachlan J; Jahnke, Kay D; Metsch, Mathias H; Sipahigil, Alp; Binder, Jan M; Teraji, Tokuyuki; Sumiya, Hitoshi; Isoya, Junichi; Lukin, Mikhail D; Hemmer, Philip; Jelezko, Fedor

    2014-12-31

    The silicon-vacancy (SiV-) color center in diamond has attracted attention because of its unique optical properties. It exhibits spectral stability and indistinguishability that facilitate efficient generation of photons capable of demonstrating quantum interference. Here we show optical initialization and readout of electronic spin in a single SiV- center with a spin relaxation time of T1=2.4±0.2  ms. Coherent population trapping (CPT) is used to demonstrate coherent preparation of dark superposition states with a spin coherence time of T2⋆=35±3  ns. This is fundamentally limited by orbital relaxation, and an understanding of this process opens the way to extend coherence by engineering interactions with phonons. Hyperfine structure is observed in CPT measurements with the 29Si isotope which allows access to nuclear spin. These results establish the SiV- center as a solid-state spin-photon interface. PMID:25615330

  19. Three-point bending analysis of doubly clamped silicon nanowire beams; Young's modulus, initial stress, and crystal orientation

    SciTech Connect

    Yaish, Y. E. Calahorra, Y.; Shtempluck, O.; Kotchetkov, V.

    2015-04-28

    A non-linear model is introduced describing the force-deflection relation of doubly clamped beams, including initial stress. Several approximations for the exact model are developed and compared, revealing the importance of considering the initial stress during 3-point bending measurements analysis. A novel approximation is found to be better than others, and both the exact model and this approximation are in perfect agreement with finite element simulations. A brief experimental example of silicon nanowires is presented in which the Young's modulus, the initial stress, and the crystallographic growth orientation are extracted by 3-point bending analysis.

  20. Towards High Performance p-Type Transparent Conducting Oxides

    SciTech Connect

    Roy, B.; Ode, A.; Readey, D.; Perkins, J.; Parilla, P.; Teplin, C.; Kaydanova, T.; Miedaner, A.; Curtis, C.; Martinson, A.; Coutts, T.; Ginley, D.; Hosono, H.

    2003-05-01

    P-type transparent conductive oxides would have potential applications in photovoltaics, transparent electronics and organic opto-electronics. In this paper we present results on the synthesis of Cu2SrO2, a p-type transparent conducting oxide, by a chemical solution route as well as the conventional pulse laser deposition (PLD) method. For Cu2SrO2 by the chemical solution route, samples were made by spraying deposition on quartz substrates using an aqueous solution of Copper formate and Strontium acetate. Phase pure materials were obtained by an optimum two stage annealing sequence. This initial work led to the development of good quality homogeneous films by a related sol-gel approach. We have also used pulsed laser depostion (PLD) to deposit Cu2SrO2 and CuInO2 thin films on quartz substrates. We have obtained improved conductivities in the CuInO2 thin films over previously published work. We present details on the nature of the relationship of process parameters to the opto-electronic properties of the films.

  1. Preparation of High Silicon Electrical Steel Sheets with Strong {100} Recrystallization Texture by the Texture Inheritance of Initial Columnar Grains

    NASA Astrophysics Data System (ADS)

    Pan, Hongjiang; Zhang, Zhihao; Xie, Jianxin

    2016-05-01

    Texture evolutions and recrystallization texture features in warm- and cold-rolled sheets of high silicon electrical steel with two different initial microstructures (columnar-grained and equiaxed-grained microstructures) were investigated. The relationships between the recrystallization textures and the initial textures (the textures before rolling) of the samples were analyzed. The results showed that after annealing at 1073 K (800 °C) for 1 hour, strong {100} recrystallization textures with volume fractions of more than 47 pct were obtained in the columnar-grained samples fabricated by warm and cold rolling along the growing direction of the columnar grains. While after rolling and annealing in the same processes, only 12.8 pct volume fractions of {100} recrystallization texture were revealed in the equiaxed-grained samples. The formation of strong {100} recrystallization texture in the annealed sheets of high silicon electrical steel with initial columnar grains was attributed to the favorable texture inheritance of the initial texture during rolling and annealing. The columnar grains of strong near {100}<001> ({100}<001> {310}<001>) orientation in the samples before rolling were transferred into deformed grains with orientations such as {100}<011> and {100}<012>. after rolling. Afterwards, these deformed grains were further transferred into {100} oriented recrystallized grains, which formed strong {100} recrystallization texture in the annealed sheets and exhibited preferable soft magnetic properties.

  2. Initial steps toward the realization of large area arrays of single photon counting pixels based on polycrystalline silicon TFTs

    NASA Astrophysics Data System (ADS)

    Liang, Albert K.; Koniczek, Martin; Antonuk, Larry E.; El-Mohri, Youcef; Zhao, Qihua; Jiang, Hao; Street, Robert A.; Lu, Jeng Ping

    2014-03-01

    The thin-film semiconductor processing methods that enabled creation of inexpensive liquid crystal displays based on amorphous silicon transistors for cell phones and televisions, as well as desktop, laptop and mobile computers, also facilitated the development of devices that have become ubiquitous in medical x-ray imaging environments. These devices, called active matrix flat-panel imagers (AMFPIs), measure the integrated signal generated by incident X rays and offer detection areas as large as ~43×43 cm2. In recent years, there has been growing interest in medical x-ray imagers that record information from X ray photons on an individual basis. However, such photon counting devices have generally been based on crystalline silicon, a material not inherently suited to the cost-effective manufacture of monolithic devices of a size comparable to that of AMFPIs. Motivated by these considerations, we have developed an initial set of small area prototype arrays using thin-film processing methods and polycrystalline silicon transistors. These prototypes were developed in the spirit of exploring the possibility of creating large area arrays offering single photon counting capabilities and, to our knowledge, are the first photon counting arrays fabricated using thin film techniques. In this paper, the architecture of the prototype pixels is presented and considerations that influenced the design of the pixel circuits, including amplifier noise, TFT performance variations, and minimum feature size, are discussed.

  3. Initial stem cell adhesion on porous silicon surface: molecular architecture of actin cytoskeleton and filopodial growth

    NASA Astrophysics Data System (ADS)

    Collart-Dutilleul, Pierre-Yves; Panayotov, Ivan; Secret, Emilie; Cunin, Frédérique; Gergely, Csilla; Cuisinier, Frédéric; Martin, Marta

    2014-10-01

    The way cells explore their surrounding extracellular matrix (ECM) during development and migration is mediated by lamellipodia at their leading edge, acting as an actual motor pulling the cell forward. Lamellipodia are the primary area within the cell of actin microfilaments (filopodia) formation. In this work, we report on the use of porous silicon (pSi) scaffolds to mimic the ECM of mesenchymal stem cells from the dental pulp (DPSC) and breast cancer (MCF-7) cells. Our atomic force microscopy (AFM), fluorescence microscopy, and scanning electron microscopy (SEM) results show that pSi promoted the appearance of lateral filopodia protruding from the DPSC cell body and not only in the lamellipodia area. The formation of elongated lateral actin filaments suggests that pores provided the necessary anchorage points for protrusion growth. Although MCF-7 cells displayed a lower presence of organized actin network on both pSi and nonporous silicon, pSi stimulated the formation of extended cell protrusions.

  4. Cell adhesion response on femtosecond laser initiated liquid assisted silicon surface.

    PubMed

    Ulmeanu, M; Sima, L E; Ursescu, D; Enculescu, M; Bazan, X; Quintana, I

    2014-03-01

    Silicon substrates were irradiated at normal incidence with a femtosecond Ti:sapphire laser (Quatronix, 90 fs pulse duration, 1 kHz repetition rate, M(2) ~ 1.2, maximum energy peak 350 mJ ) operating at a wavelength of 400 nm and focused via a microscope objective (Newport; UV Objective Model, 37x 0.11 N.A.). The laser scanning was assisted by liquids precursors media such as methanol and 1,1,2-trichlorotrifluoroethane. By altering the processing parameters, such as incident laser energy, scanning speed, and different irradiation media, various surface structures were produced on areas with 1 mm(2) dimensions. We analyzed the dependence of the surface morphology on laser pulse energy, scanning speed and irradiation media. Well ordered areas are developed without imposing any boundary conditions for the capillary waves that coarsens the ripple pattern. To assess biomaterial-driven cell adhesion response we investigated actin filaments organization and cell morphological changes following growth onto processed silicon substrates. Our study of bone cell progenitor interaction with laser nanoprocessed silicon lines has shown that cells anchor mainly to contact points along the nanostructured surface. Consequently, actin filaments are stretched towards the 15 µm wide parallel lines increasing lateral cell spreading and changing the bipolar shape of mesenchymal stem cells. PMID:24444164

  5. Photoinduced p-Type Conductivity in n-Type ZnO

    NASA Astrophysics Data System (ADS)

    Zhao, W. X.; Sun, B.; Shen, Z.; Liu, Y. H.; Chen, P.

    2015-03-01

    Ag/[BaTiO3/γ-Fe2O3]/ZnO composite films were grown on an n-type silicon (100) single-crystal substrate by magnetron sputtering, and annealed at various temperatures. Capacitance-voltage ( C- V) curves show that the capacitance gradually increases with increasing annealed temperature. In addition, ZnO exhibits n-type conductivity in the dark but p-type conductivity under incandescent lamp illumination. The photoinduced p-type conductivity in n-type ZnO should be related to a special n-type ZnO layer originating from high-temperature annealing. The current-voltage ( I- V) curves of the [BaTiO3/γ-Fe2O3]/ZnO thin films display a strong photoconductivity effect.

  6. Computational Study of Field Initiated Surface Reactions for Synthesis of Diamond and Silicon

    NASA Technical Reports Server (NTRS)

    Musgrave, Charles Bruce

    1999-01-01

    This project involves using quantum chemistry to simulate surface chemical reactions in the presence of an electric field for nanofabrication of diamond and silicon. A field delivered by a scanning tunneling microscope (STM) to a nanometer scale region of a surface affects chemical reaction potential energy surfaces (PES) to direct atomic scale surface modification to fabricate sub-nanometer structures. Our original hypothesis is that the applied voltage polarizes the charge distribution of the valence electrons and that these distorted molecular orbitals can be manipulated with the STM so as to change the relative stabilities of the electronic configurations over the reaction coordinates and thus the topology of the PES and reaction kinetics. Our objective is to investigate the effect of applied bias on surface reactions and the extent to which STM delivered fields can be used to direct surface chemical reactions on an atomic scale on diamond and silicon. To analyze the fundamentals of field induced chemistry and to investigate the application of this technique for the fabrication of nanostructures, we have employed methods capable of accurately describing molecular electronic structure. The methods we employ are density functional theory (DFT) quantum chemical (QC) methods. To determine the effect of applied bias on surface reactions we have calculated the QC PESs in various applied external fields for various reaction steps for depositing or etching diamond and silicon. We have chosen reactions which are thought to play a role in etching and the chemical vapor deposition growth of Si and diamond. The PESs of the elementary reaction steps involved are then calculated under the applied fields, which we vary in magnitude and configuration. We pay special attention to the change in the reaction barriers, and transition state locations, and search for low energy reaction channels which were inaccessible without the applied bias.

  7. Initial stem cell adhesion on porous silicon surface: molecular architecture of actin cytoskeleton and filopodial growth

    PubMed Central

    2014-01-01

    The way cells explore their surrounding extracellular matrix (ECM) during development and migration is mediated by lamellipodia at their leading edge, acting as an actual motor pulling the cell forward. Lamellipodia are the primary area within the cell of actin microfilaments (filopodia) formation. In this work, we report on the use of porous silicon (pSi) scaffolds to mimic the ECM of mesenchymal stem cells from the dental pulp (DPSC) and breast cancer (MCF-7) cells. Our atomic force microscopy (AFM), fluorescence microscopy, and scanning electron microscopy (SEM) results show that pSi promoted the appearance of lateral filopodia protruding from the DPSC cell body and not only in the lamellipodia area. The formation of elongated lateral actin filaments suggests that pores provided the necessary anchorage points for protrusion growth. Although MCF-7 cells displayed a lower presence of organized actin network on both pSi and nonporous silicon, pSi stimulated the formation of extended cell protrusions. PMID:25386101

  8. Photovoltaic properties of ZnO nanorods/p-type Si heterojunction structures.

    PubMed

    Pietruszka, Rafal; Witkowski, Bartlomiej Slawomir; Luka, Grzegorz; Wachnicki, Lukasz; Gieraltowska, Sylwia; Kopalko, Krzysztof; Zielony, Eunika; Bieganski, Piotr; Placzek-Popko, Ewa; Godlewski, Marek

    2014-01-01

    Selected properties of photovoltaic (PV) structures based on n-type zinc oxide nanorods grown by a low temperature hydrothermal method on p-type silicon substrates (100) are investigated. PV structures were covered with thin films of Al doped ZnO grown by atomic layer deposition acting as transparent electrodes. The investigated PV structures differ in terms of the shapes and densities of their nanorods. The best response is observed for the structure containing closely-spaced nanorods, which show light conversion efficiency of 3.6%. PMID:24605282

  9. Fabrication and morphology of porous p-type SiC

    NASA Astrophysics Data System (ADS)

    Shishkin, Y.; Ke, Y.; Devaty, R. P.; Choyke, W. J.

    2005-02-01

    Porous silicon carbide fabricated from p-type 4H and 6H SiC wafers by electrochemical etching in hydrofluoric electrolyte is studied. An investigation of the dependence on wafer polarity reveals that pore formation is favored on the C face while complete dissolution occurs on the Si face. When the etching is done on the C face, the pore wall thickness decreases with increasing current density. The morphology of the front surface of the sample depends on the prior treatment of the workpiece surface. The porosity is estimated based on the analysis of scanning electron microscope images, charge-transfer calculations, and gravimetric analysis.

  10. Ensemble Monte Carlo calculation of the hole initiated impact ionization rate in bulk GaAs and silicon using a k-dependent, numerical transition rate formulation

    NASA Technical Reports Server (NTRS)

    Oguzman, Ismail H.; Wang, Yang; Kolnik, Jan; Brennan, Kevin F.

    1995-01-01

    The hole initiated impact ionization rate in bulk silicon and GaAs is calculated using a numerical formulation of the impact ionization transition rate incorporated into an ensemble Monte Carlo simulation. The transition rate is calculated from Fermi's golden rule using a two-body screened Coulomb interaction including a wavevector dependent dielectric function. It is found that the effective threshold for hole initiated ionization is relatively soft in both materials, that the split-off band dominates the ionization process in GaAs. and that no clear dominance by any one band is observed in silicon, though the rate out of the light hole band is greatest.

  11. Development of improved p-type Si-20 at. % Ge by addition of fullerite

    NASA Astrophysics Data System (ADS)

    Cook, B. A.; Harringa, J. L.

    1994-08-01

    In a series of experiments designed to evaluate the possibility of lowering the lattice thermal conductivity of silicon-germanium alloys through the formation of an inert, intragranular nanophase, a number of p-type Si-20 at. % Ge alloys, with a nominal doping level of 0.5 at. % boron, were prepared with varying amounts of fullerite, a mixture of 90% C60+10% C70 with a particle size of 0.7 nm. The alloys were synthesized by mechanical alloying (MA) and the fullerite was added at various stages of the preparation sequence. Compacts consolidated by hot pressing at temperatures of 1200 °C to 1265 °C were found to be fully dense and homogeneous. Each compact was characterized by Hall effect at room temperature and also by electrical resistivity, Seebeck coefficient, and thermal diffusivity measurements to 1000 °C. A reduction in thermal conductivity of up to 22% compared to standard p-type alloys was observed in samples containing 0.8 weight percent additions. In this study, a maximum integrated average figure of merit, Z, between 300 and 1000 °C of 0.65×10-3 °C-1 was obtained, corresponding to 0.4 weight percent addition of fullerite. Observation of selected samples by transmission electron microscopy revealed that the fullerite reacted with silicon to form nanophase SiC inclusions.

  12. Angular sensitivity of modeled scientific silicon charge-coupled devices to initial electron direction

    NASA Astrophysics Data System (ADS)

    Plimley, Brian; Coffer, Amy; Zhang, Yigong; Vetter, Kai

    2016-08-01

    Previously, scientific silicon charge-coupled devices (CCDs) with 10.5-μm pixel pitch and a thick (650 μm), fully depleted bulk have been used to measure gamma-ray-induced fast electrons and demonstrate electron track Compton imaging. A model of the response of this CCD was also developed and benchmarked to experiment using Monte Carlo electron tracks. We now examine the trade-off in pixel pitch and electronic noise. We extend our CCD response model to different pixel pitch and readout noise per pixel, including pixel pitch of 2.5 μm, 5 μm, 10.5 μm, 20 μm, and 40 μm, and readout noise from 0 eV/pixel to 2 keV/pixel for 10.5 μm pixel pitch. The CCD images generated by this model using simulated electron tracks are processed by our trajectory reconstruction algorithm. The performance of the reconstruction algorithm defines the expected angular sensitivity as a function of electron energy, CCD pixel pitch, and readout noise per pixel. Results show that our existing pixel pitch of 10.5 μm is near optimal for our approach, because smaller pixels add little new information but are subject to greater statistical noise. In addition, we measured the readout noise per pixel for two different device temperatures in order to estimate the effect of temperature on the reconstruction algorithm performance, although the readout is not optimized for higher temperatures. The noise in our device at 240 K increases the FWHM of angular measurement error by no more than a factor of 2, from 26° to 49° FWHM for electrons between 425 keV and 480 keV. Therefore, a CCD could be used for electron-track-based imaging in a Peltier-cooled device.

  13. Soft error rate simulation and initial design considerations of neutron intercepting silicon chip (NISC)

    NASA Astrophysics Data System (ADS)

    Celik, Cihangir

    -scale technologies. Prevention of SEEs has been studied and applied in the semiconductor industry by including radiation protection precautions in the system architecture or by using corrective algorithms in the system operation. Decreasing 10B content (20%of natural boron) in the natural boron of Borophosphosilicate glass (BPSG) layers that are conventionally used in the fabrication of semiconductor devices was one of the major radiation protection approaches for the system architecture. Neutron interaction in the BPSG layer was the origin of the SEEs because of the 10B (n,alpha) 7Li reaction products. Both of the particles produced have the capability of ionization in the silicon substrate region, whose thickness is comparable to the ranges of these particles. Using the soft error phenomenon in exactly the opposite manner of the semiconductor industry can provide a new neutron detection system based on the SERs in the semiconductor memories. By investigating the soft error mechanisms in the available semiconductor memories and enhancing the soft error occurrences in these devices, one can convert all memory using intelligent systems into portable, power efficient, directiondependent neutron detectors. The Neutron Intercepting Silicon Chip (NISC) project aims to achieve this goal by introducing 10B-enriched BPSG layers to the semiconductor memory architectures. This research addresses the development of a simulation tool, the NISC Soft Error Analysis Tool (NISCSAT), for soft error modeling and analysis in the semiconductor memories to provide basic design considerations for the NISC. NISCSAT performs particle transport and calculates the soft error probabilities, or SER, depending on energy depositions of the particles in a given memory node model of the NISC. Soft error measurements were performed with commercially available, off-the-shelf semiconductor memories and microprocessors to observe soft error variations with the neutron flux and memory supply voltage. Measurement

  14. p-type conduction in sputtered indium oxide films

    SciTech Connect

    Stankiewicz, Jolanta; Alcala, Rafael; Villuendas, Francisco

    2010-05-10

    We report p-type conductivity in intrinsic indium oxide (IO) films deposited by magnetron sputtering on fused quartz substrates under oxygen-rich ambient. Highly oriented (111) films were studied by x-ray diffraction, optical absorption, and Hall effect measurements. We fabricated p-n homojunctions on these films.

  15. High carrier concentration p-type transparent conducting oxide films

    DOEpatents

    Yan, Yanfa; Zhang, Shengbai

    2005-06-21

    A p-type transparent conducting oxide film is provided which is consisting essentially of, the transparent conducting oxide and a molecular doping source, the oxide and doping source grown under conditions sufficient to deliver the doping source intact onto the oxide.

  16. Synthesis of p-type GaN nanowires

    NASA Astrophysics Data System (ADS)

    Kim, Sung Wook; Park, Youn Ho; Kim, Ilsoo; Park, Tae-Eon; Kwon, Byoung Wook; Choi, Won Kook; Choi, Heon-Jin

    2013-08-01

    GaN has been utilized in optoelectronics for two decades. However, p-type doping still remains crucial for realization of high performance GaN optoelectronics. Though Mg has been used as a p-dopant, its efficiency is low due to the formation of Mg-H complexes and/or structural defects in the course of doping. As a potential alternative p-type dopant, Cu has been recognized as an acceptor impurity for GaN. Herein, we report the fabrication of Cu-doped GaN nanowires (Cu:GaN NWs) and their p-type characteristics. The NWs were grown vertically via a vapor-liquid-solid (VLS) mechanism using a Au/Ni catalyst. Electrical characterization using a nanowire-field effect transistor (NW-FET) showed that the NWs exhibited n-type characteristics. However, with further annealing, the NWs showed p-type characteristics. A homo-junction structure (consisting of annealed Cu:GaN NW/n-type GaN thin film) exhibited p-n junction characteristics. A hybrid organic light emitting diode (OLED) employing the annealed Cu:GaN NWs as a hole injection layer (HIL) also demonstrated current injected luminescence. These results suggest that Cu can be used as a p-type dopant for GaN NWs.GaN has been utilized in optoelectronics for two decades. However, p-type doping still remains crucial for realization of high performance GaN optoelectronics. Though Mg has been used as a p-dopant, its efficiency is low due to the formation of Mg-H complexes and/or structural defects in the course of doping. As a potential alternative p-type dopant, Cu has been recognized as an acceptor impurity for GaN. Herein, we report the fabrication of Cu-doped GaN nanowires (Cu:GaN NWs) and their p-type characteristics. The NWs were grown vertically via a vapor-liquid-solid (VLS) mechanism using a Au/Ni catalyst. Electrical characterization using a nanowire-field effect transistor (NW-FET) showed that the NWs exhibited n-type characteristics. However, with further annealing, the NWs showed p-type characteristics. A homo

  17. Investigating photoluminescence quantum yield of silicon nanocrystals formed in SiOx with different initial Si excess

    NASA Astrophysics Data System (ADS)

    Chung, Nguyen Xuan; Limpens, Rens; Gregorkiewicz, Tom

    2015-09-01

    Optical properties of silicon nanocrystals dispersed in SiO2 matrix were investigated in terms of photoluminescence quantum yield at room temperature. Two multilayer samples, prepared from substoichiometric silicon oxide layers by annealing at 1150°C were used to investigate the influence of Si concentration. Significant reduction of photoluminescence quantum yield and a very specific change of its excitation energy dependence upon variation of silicon excess are concluded from the experimental data. Possible mechanisms leading to these changes are discussed.

  18. Triple-junction amorphous silicon alloy solar cell with 14.6{percent} initial and 13.0{percent} stable conversion efficiencies

    SciTech Connect

    Yang, J.; Banerjee, A.; Guha, S.

    1997-06-01

    We have achieved 14.6{percent} initial and 13.0{percent} stable conversion efficiencies using an amorphous silicon-based alloy in a spectrum-splitting, triple-junction structure. These efficiencies have been confirmed independently by the National Renewable Energy Laboratory. Key factors leading to this major advance include improvements made in the low band-gap amorphous silicon{endash}germanium alloy cell, the pn tunnel junction between the component cells, and the top conducting oxide. {copyright} {ital 1997 American Institute of Physics.}

  19. P-type Oxides and the Growth of Heterostructure Oxide Devices

    NASA Astrophysics Data System (ADS)

    Hosono, Hideo

    2002-03-01

    Transparent conductive oxides (TCOs) are widely used as transparent metallic electrodes for various displays and solar cells. However, even though TCO is an n-type semiconductor, there is almost no application based on the active function as a compound semiconductor. The primary reason is because most active functions in semiconductors come from the characteristic properties of p-n junction but TCOs do not have a p-type. We anticipate that new frontier of transparent oxide semiconductors (TOSs) utilizing both optical transparency and electron activity in semiconductors will be opened if a p-type TCO is realized. In 1997, we reported on CuAlO2 (thin films) as the first p-type TCO along with a chemical design concept to explore the candidate materials. After that, a series of p-type TCOs based on a Cu+ -based system have been reported following the design concept, i.e., CuGaO2, CuInO2, and SrCu2O2. In 1999, a transparent p-n heterojunction diode exhibiting a rectifying I-V characteristic was fabricated using a combination of p-SrCu2O2 (SCO) and n-ZnO. Ultraviolet-emitting diode (UV-LED) is a typical active device, which can use the features of TOSs. Thus, since the initiation of our project (October, 1999), we concentrated our effort on the fabrication of UV-LED based on transparent p-n junction composed of TOSs. The fabrication was realized(APL,77,475,2000) by the formation of p-n heterojunction composed of heteroepitaxially grown p-SCO and n-ZnO. In this talk I will review our approach to P-type TCOs and UV-LED based on PN heterojuction utilizing TCOs along with recent advances.

  20. Simultaneous Formation of Ni/Al Ohmic Contacts to Both n- and p-Type 4H-SiC

    NASA Astrophysics Data System (ADS)

    Ito, Kazuhiro; Onishi, Toshitake; Takeda, Hidehisa; Kohama, Kazuyuki; Tsukimoto, Susumu; Konno, Mitsuru; Suzuki, Yuya; Murakami, Masanori

    2008-11-01

    The fabrication procedure for silicon carbide power metal oxide semiconductor field-effect transistors can be improved through simultaneous formation (i.e., using the same contact materials and a one-step annealing process) of ohmic contacts on both the n-source and p-well regions. We have succeeded in the simultaneous formation of Ni/Al ohmic contacts to n- and p-type SiC after annealing at 1000°C for 5 min in an ultrahigh vacuum. Ohmic contacts to n-type SiC were found when the Al-layer thickness was less than about 6 nm, while ohmic contacts to p-type SiC were observed for an Al-layer thickness greater than about 5 nm. Only the contacts with an Al-layer thickness in the range of 5 nm to 6 nm exhibited ohmic behavior to both n- and p-type SiC, with a specific contact resistance of 1.8 × 10-4 Ω cm2 and 1.2 × 10-2 Ω cm2 for n- and p-type SiC, respectively. An about 100-nm-thick contact layer was uniformly formed on the SiC substrate, and polycrystalline δ-Ni2Si(Al) grains were formed at the contact/SiC interface. In the samples that exhibited ohmic behavior to both n- and p-type SiC, the distribution of the Al/Ni ratios in the δ-Ni2Si(Al) grains was larger than that observed for any of the samples that showed ohmic behavior to either n- or p-type SiC. Furthermore, the grain size of the δ-Ni2Si(Al) grains in the samples showing ohmic behavior to both n- and p-type SiC was smaller than the grains in any of the samples that showed ohmic behavior to either n- or p-type SiC. Thus, the large distribution in the Al/Ni ratios and a fine microstructure were found to be characteristic of the ohmic contacts to both n- and p-type SiC. Grains with a low Al concentration correspond to ohmic contacts to n-type SiC, while grains with a high Al concentration correspond to ohmic contacts to p-type SiC.

  1. Thermoelectric properties of gallium-doped p-type germanium

    NASA Astrophysics Data System (ADS)

    Ohishi, Yuji; Takarada, Sho; Aikebaier, Yusufu; Muta, Hiroaki; Kurosaki, Ken; Yamanaka, Shinsuke; Miyazaki, Yoshinobu; Uchida, Noriyuki; Tada, Tetsuya

    2016-05-01

    In this study, the temperature-dependent thermoelectric properties of p-type single-crystal Ge, which is a useful material for thermoelectric applications owing to its significantly high carrier mobility, were investigated. The thermoelectric properties of Ga-doped (5.7 × 1016, 3.4 × 1018, and 1.0 × 1019 cm-3) p-type single-crystal Ge were measured from room temperature to 770 K. The sample with a carrier concentration of 1.0 × 1019 cm-3 showed the highest thermoelectric figure of merit, ZT, over the entire measured temperature range. The maximum ZT value was 0.06 at 650 K. A theoretical model based on the Boltzmann transport equation with relaxation-time approximation was developed and quantitatively reproduced the experimentally observed data. The optimal impurity concentration predicted by this model was 3 × 1019 cm-3 at 300 K and increased with temperature.

  2. p type doping of zinc oxide by arsenic ion implantation

    SciTech Connect

    Braunstein, G.; Muraviev, A.; Saxena, H.; Dhere, N.; Richter, V.; Kalish, R.

    2005-11-07

    p type doping of polycrystalline ZnO thin films, by implantation of arsenic ions, is demonstrated. The approach consisted of carrying out the implantations at liquid-nitrogen temperature ({approx}-196 deg. C), followed by a rapid in situ heating of the sample, at 560 deg. C for 10 min, and ex situ annealing at 900 deg. C for 45 min in flowing oxygen. p type conductivity with a hole concentration of 2.5x10{sup 13} cm{sup -2} was obtained using this approach, following implantation of 150 keV 5x10{sup 14} As/cm{sup 2}. A conventional room-temperature implantation of 1x10{sup 15} As/cm{sup 2}, followed by the same ex situ annealing, resulted in n type conductivity with a carrier concentration of 1.7x10{sup 12} cm{sup -2}.

  3. Effect of Particle Morphology on Critical Conditions for Shock-Initiated Reactions in Titanium-Silicon Powder Mixtures

    NASA Astrophysics Data System (ADS)

    Frost, David; Jette, Francois; Goroshin, Samuel; Higgins, Andrew; Lee, Julian

    2009-06-01

    The effect of titanium particle morphology on the shock sensitivity of titanium-silicon powder mixtures has been investigated experimentally. The powder mixtures were tested in a planar recovery capsule, with the shock loading produced by a high explosive Tetryl booster charge placed on top of the capsule and a PMMA attenuator. Reactions were not observed for stoichiometric mixtures of large (75 -- 106 μm), spherical Ti particles with fine (< 44 μm) Si particles for incident peak shock pressures of up to 23 GPa, estimated with LS-DYNA. In contrast, mixtures with fine (< 45 μm) spherical Ti particles or irregularly-shaped fine (< 20 μm) Ti particles had critical shock pressures for reaction initiation of 7±3 GPa and 5±2 GPa, respectively. Microscopy and spectroscopy were used to identify the degree of intermixing between the particles for shock loading just below the reaction threshold. For the largest spherical Ti particles, little particle intermixing was evident. However, differential thermal analysis carried out demonstrated that even for the large Ti particles, shock loading of the samples generated microstructural effects which lowered the temperature for the onset of exothermic reaction of the shocked sample by about 80^oC.

  4. P-type conductivity in annealed strontium titanate

    DOE PAGESBeta

    Poole, Violet M.; Corolewski, Caleb D.; McCluskey, Matthew D.

    2015-12-17

    In this study, Hall-effect measurements indicate p-type conductivity in bulk, single-crystal strontium titanate (SrTiO3, or STO) samples that were annealed at 1200°C. Room temperature mobilities above 100 cm2/Vs were measured, an order of magnitude higher than those for electrons (5-10 cm2/Vs). Average hole densities were in the 109-1010 cm-3 range, consistent with a deep acceptor.

  5. Anomalous Oxide Charge Variation Identified by Alternating Current Surface Photovoltage Method in Cr-Aqueous-Solution-Rinsed p-Type Si(001) Wafers Exposed to Air

    NASA Astrophysics Data System (ADS)

    Shimizu, Hirofumi; Sanada, Yuji

    2011-11-01

    Chromium (Cr)-aqueous-solution-rinsed and/or hydrofluoric acid (HF)-solution-dipped p-type silicon (Si) (001) wafer surfaces are investigated by the frequency-dependent alternating current (AC) surface photovoltage (SPV) method. At the Cr(OH)3/p-type Si interface, in principle, a Schottky barrier could not possibly be generated. The Cr ion (Cr3+) is considered to forcibly deprive a p-type Si substrate of electrons during metallization (Cr3++3e-→Cr). Thus, at an early stage of air exposure, a positive fixed oxide charge may be compensated for by electrons, indicating the disappearance of AC SPV. With air exposure time, AC SPV emerges again and increases gradually in a Cr-deposited p-type Si(001) surface. This is because the native oxide between the Cr atom layer and the p-type Si substrate grows with time. As a result, a positive fixed oxide charge exceeds the overall charge state of the Cr-deposited p-type Si surface. Thus, AC SPV appears again and gradually increases with the fixed oxide charge in p-type Si. The saturated value is in a good agreement with that of the HF aqueous-solution-dipped p-type Si surface.

  6. X, E, M, and P-Type Asteroid Spectral Observations

    NASA Astrophysics Data System (ADS)

    Clark, B. E.; Rivkin, A. S.; Bus, S. J.; Sanders, J.

    2003-05-01

    What are the X-types made of? How would knowledge of their composition change our picture of the geological structure of the asteroid regions? X-types are important in the main belt, yet we do not understand their composition or meteorite linkage. This is an outstanding problem in asteroid-meteorite studies, because X-types comprise approximately 20% of the inner main belt (Tholen and Barucci 1989; Bus 1999). We have conducted a program of infrared (0.8-2.5microns) observations aimed at determining mineralogy without albedo information. Because X-types are spectrally like E, M, and P-type asteroids, we observed 18 X-types, 5 E-types, 8 M-types, and 4 P-types. This is the first focused study of XEMP asteroids. In this paper, we present a compositional analysis of the new spectral data. What we call XEMPs are asteroids identified as ambiguous on the basis of their visible spectral properties only (Zellner et al. 1985; Tholen 1984; Bus and Binzel 2002). By convention (Bowell et al. 1978; Tholen and Barucci 1989), X-types with measured geometric albedos are classified into E, M, or P-types, where E-types (designated ``E" based on their possible link with enstatite meteorites) are high-albedo objects, P-types are low-albedo objects (there are no meteorite analogs for these objects), and M-types (designated ``M" based on their possible link with metallic meteorites) are intermediate. Bus and Binzel (2002) found subtle features in X-class spectra in a high resolution survey. We have regrouped XEMP spectra for a reanalysis of the extended wavelength coverage now available (0.3-2.5 microns). When continuum slope is removed, we find distinct 0.9 micron bands at the level of 2-5% in many of our XEMP objects. We also find consistent wavelength maxima near 1.5 microns, and hints of 2.0 micron bands in some objects. Our preliminary findings suggest that new mineralogy-based groupings may be called for, breaking down the old albedo-based E, M, and P-type designations. We

  7. Piezoresistivity of polycrystalline p-type diamond films of various doping levels at different temperatures

    SciTech Connect

    Wang, W.L.; Jiang, X.; Taube, K.; Klages, C.

    1997-07-01

    The piezoresistivity of polycrystalline p-type diamond films has been studied. The films were grown by microwave plasma assisted chemical vapor deposition and {ital in situ} doped with different concentrations of boron. A four-point electrical measurement was performed to evaluate the film resistivity change upon straining in a four-point bending beam setup. Films were glued directly onto a stainless steel beam and the silicon substrates were selectively removed. A gauge factor (relative change of the resistivity divided by the elastic strain) of about 690 under 100 microstrains was obtained at room temperature for a film doped with 32 ppm boron. With increasing temperature and dopant concentration the gauge factor increases. The experimental results obtained are discussed. {copyright} {ital 1997 American Institute of Physics.}

  8. Quasi-perpetual discharge behaviour in p-type Ge-air batteries.

    PubMed

    Ocon, Joey D; Kim, Jin Won; Abrenica, Graniel Harne A; Lee, Jae Kwang; Lee, Jaeyoung

    2014-11-01

    Metal-air batteries continue to become attractive energy storage and conversion systems due to their high energy and power densities, safer chemistries, and economic viability. Semiconductor-air batteries - a term we first define here as metal-air batteries that use semiconductor anodes such as silicon (Si) and germanium (Ge) - have been introduced in recent years as new high-energy battery chemistries. In this paper, we describe the excellent doping-dependent discharge kinetics of p-type Ge anodes in a semiconductor-air cell employing a gelled KOH electrolyte. Owing to its Fermi level, n-type Ge is expected to have lower redox potential and better electronic conductivity, which could potentially lead to a higher operating voltage and better discharge kinetics. Nonetheless, discharge measurements demonstrated that this prediction is only valid at the low current regime and breaks down at the high current density region. The p-type Ge behaves extremely better at elevated currents, evident from the higher voltage, more power available, and larger practical energy density from a very long discharge time, possibly arising from the high overpotential for surface passivation. A primary semiconductor-air battery, powered by a flat p-type Ge as a multi-electron anode, exhibited an unprecedented full discharge capacity of 1302.5 mA h gGe(-1) (88% anode utilization efficiency), the highest among semiconductor-air cells, notably better than new metal-air cells with three-dimensional and nanostructured anodes, and at least two folds higher than commercial Zn-air and Al-air cells. We therefore suggest that this study be extended to doped-Si anodes, in order to pave the way for a deeper understanding on the discharge phenomena in alkaline metal-air conversion cells with semiconductor anodes for specific niche applications in the future. PMID:24975009

  9. Reduced thermal conductivity due to scattering centers in p-type SiGe alloys

    NASA Technical Reports Server (NTRS)

    Beaty, John S.; Rolfe, Jonathon L.; Vandersande, Jan; Fleurial, Jean-Pierre

    1992-01-01

    Spark erosion was used to produce ultra-fine particles of SiGe thermoelectric material and boron nitride, an inert phonon-scattering material. A homogeneous powder was made by mixing the two powders. The mixture was hot pressed to produce a thermoelectric material with uniformity dispersed, ultra-fine, inert, phonon-scattering centers. It is shown that, in samples with inert boron nitride or silicon nitride, thermal conductivity of a SiGe alloy can be reduced by about 25 percent while maintaining the electrical properties of the samples. Annealing of all the samples at 1525 K caused grain growth to over a micron, eliminating the detrimental effect attributable to small grains. Only in the sample with boron nitride the thermal conductivity did remain well below that for standard p-type SiGe (about 25 percent), while the electrical resistivity and Seebeck coefficient were very close to the values for standard p-type 80/20 SiGe.

  10. Quantum mechanical simulation of hole transport in p-type Si Schottky barrier MOSFETs.

    PubMed

    Choi, Wonchul; Shin, Mincheol

    2011-07-01

    A full quantum-mechanical simulation of p-type nanowire Schottky barrier metal oxide silicon field effect transistors (SB-MOSFETs) is performed by solving the three-dimensional Schrödinger and Poisson's equations self-consistently. The non-equilibrium Green's function (NEGF) approach is adopted to treat hole transport, especially quantum tunneling through SB. In this work, p-type nanowire SB-MOSFETs are simulated based on the 3-band k.p method, using the k.p parameters that were tuned by benchmarking against the tight-binding method with sp3s* orbitals. The device shows a strong dependence on the transport direction, due to the orientation-sensitive tunneling effective mass and the confinement energy. With regard to the subthreshold slope, the [110] and [111] oriented devices with long channel show better performance, but they are more vulnerable to the short channel effects than the [100] oriented device. The threshold voltage also shows a greater variation in the [110] and [111] oriented devices with the decrease of the channel length. PMID:22121621

  11. Initial and long-term frequency degradation of ring oscillators caused by plasma-induced damage in 65 nm bulk and fully depleted silicon-on-insulator processes

    NASA Astrophysics Data System (ADS)

    Kishida, Ryo; Oshima, Azusa; Yabuuchi, Michitarou; Kobayashi, Kazutoshi

    2015-04-01

    The degradation of reliability caused by plasma-induced damage (PID) has become a significant concern with the miniaturization of device size. In particular, it is difficult to relieve PID in silicon-on-insulator (SOI) because it contains buried oxide (BOX) layers. In this work, we compare PID between a bulk and a silicon on thin BOX (SOTB), which has BOX layers of less than 10 nm. We measure frequencies of ring oscillators with an antenna structure on a single stage. In the bulk, PID is relieved by first connecting an antenna to a drain because electric charge flows to a substrate. The difference in initial frequency is 0.79% between structures, which cause and relieve PID. SOTB also relieves the same amount of PID. Initial frequencies are affected by PID, but there is no effect of PID on the long-term degradation mainly caused by bias temperature instability (BTI).

  12. Bi-Se doped with Cu, p-type semiconductor

    SciTech Connect

    Bhattacharya, Raghu Nath; Phok, Sovannary; Parilla, Philip Anthony

    2013-08-20

    A Bi--Se doped with Cu, p-type semiconductor, preferably used as an absorber material in a photovoltaic device. Preferably the semiconductor has at least 20 molar percent Cu. In a preferred embodiment, the semiconductor comprises at least 28 molar percent of Cu. In one embodiment, the semiconductor comprises a molar percentage of Cu and Bi whereby the molar percentage of Cu divided by the molar percentage of Bi is greater than 1.2. In a preferred embodiment, the semiconductor is manufactured as a thin film having a thickness less than 600 nm.

  13. P-type conductivity in annealed strontium titanate

    SciTech Connect

    Poole, Violet M.; Corolewski, Caleb D.; McCluskey, Matthew D.

    2015-12-17

    In this study, Hall-effect measurements indicate p-type conductivity in bulk, single-crystal strontium titanate (SrTiO3, or STO) samples that were annealed at 1200°C. Room temperature mobilities above 100 cm2/Vs were measured, an order of magnitude higher than those for electrons (5-10 cm2/Vs). Average hole densities were in the 109-1010 cm-3 range, consistent with a deep acceptor.

  14. P-type conductivity in annealed strontium titanate

    SciTech Connect

    Poole, Violet M.; Corolewski, Caleb D.; McCluskey, Matthew D.

    2015-12-15

    Hall-effect measurements indicate p-type conductivity in bulk, single-crystal strontium titanate (SrTiO{sub 3}, or STO) samples that were annealed at 1200°C. Room-temperature mobilities above 100 cm{sup 2}/V s were measured, an order of magnitude higher than those for electrons (5-10 cm{sup 2}/V s). Average hole densities were in the 10{sup 9}-10{sup 10} cm{sup −3} range, consistent with a deep acceptor.

  15. Surface photovoltage studies of n-type and p-type InP

    NASA Astrophysics Data System (ADS)

    Thurgate, S. M.; Blight, K.; Laceusta, T. D.

    1994-05-01

    Surface photovoltage spectroscopy (SPV) was used to study the initial stages of oxidation of single crystal InP(110) in an attempt to understand the nature and origin of the surface states that develop. Distinct surface states were seen to develop on n-type as the surface was exposed to oxygen. A surface state, associated with cleavage damage, was also observed on p-type. A detailed fit to the experimental data was made by using a model of the dependence of surface charge on photon energy. This was used to unfold the position and intensity of the states. States trailing into the band gap from the bulk bands were seen on both n- and p-types. The analysis also indicated that pairs of isolated states, a donor and an acceptor state, were produced. On p-type, these were present on the clean, cleaved surface while they developed with oxygen exposure on n-type. These states are consistent with the point defect states proposed by the unified defect model. The time response of the SPV signal was also recorded for these surfaces. They were analysed by careful fitting to a model describing the charging and discharging characteristics. This revealed that the midgap state on n-type had a fast and a slow component.

  16. STRENGTH OF N- AND P-TYPE SKUTTERUDITES

    SciTech Connect

    Wereszczak, Andrew A; Ragan, Meredith E; Strong, Kevin T; Ritt, Patrick J; Wang, Hsin; Salvador, James R.; Yang, Jihui

    2010-01-01

    The failure stress distributions of developmental Yb0.27Co4Sb12.08 (n-type) and Ce0.86Co1.02Fe2.98Sb11.97 (p type) skutterudites were measured as a function of temperature. These thermoelectric materials are attractive candidates for use in devices under consideration for power generation sourced from intermediate to high-temperature waste heat recovery. A self-aligning, high-temperature-capable, three-point-bend fixture was developed and used to test specimens whose cross-sectional dimensions were equivalent to those typically used in thermoelectric device legs. The strength of the n-type skutterudite was approximately 115 MPa and independent of temperature to 500 C. The strength of the p-type skutterudite was equivalent to that of the n type material and independent of temperature to at least 200 C, but its strength dropped by ~20% at 400 C. Compared to other skutterudites, the herein tested compositions have equivalent or even superior strength.

  17. Light-induced anodisation of silicon for solar cell passivation

    NASA Astrophysics Data System (ADS)

    Cui, J.; Wang, X.; Opila, R.; Lennon, A.

    2013-11-01

    This paper reports a new method for forming anodic oxides on silicon surfaces using the light-induced current of pn-junction solar cells to make p-type silicon surfaces anodic. The light-induced anodisation process enables anodic oxide layers as thick as 79 nm to be formed at room temperature in a faster, more uniform, and controllable manner compared to previously reported clip-based anodisation methods. Although the effective minority carrier lifetime decreased immediately after light-induced anodisation from initial values measured with an 17 nm thermally grown oxide on both wafer surfaces, the 1-sun implied open circuit voltage of wafers on which the thermally grown oxide on the p-type surface was replaced by an anodic oxide of the same thickness could be returned to its initial value of ˜635 mV (for 3-5 Ω-cm Cz silicon wafers) after a 400 °C anneal in oxygen and then forming gas. The passivation of the formed anodic oxide layers was stable for a period of 50 days providing the oxide was protected by a 75 nm thick silicon nitride capping layer.

  18. p-Type NiO Hybrid Visible Photodetector.

    PubMed

    Mallows, John; Planells, Miquel; Thakare, Vishal; Bhosale, Reshma; Ogale, Satishchandra; Robertson, Neil

    2015-12-23

    A novel hybrid visible-light photodetector was created using a planar p-type inorganic NiO layer in a junction with an organic electron acceptor layer. The effect of different oxygen pressures on formation of the NiO layer by pulsed laser deposition shows that higher pressure increases the charge carrier density of the film and lowers the dark current in the device. The addition of a monolayer of small molecules containing conjugated π systems and carboxyl groups at the device interface was also investigated and with correct alignment of the energy levels improves the device performance with respect to the quantum efficiency, responsivity, and photogeneration. The thickness of the organic layer was also optimized for the device, giving a responsivity of 1.54 × 10(-2) A W(-1) in 460 nm light. PMID:26654105

  19. Contributions to the initial development of a microelectromechanical loop heat pipe, which is based on coherent porous silicon

    NASA Astrophysics Data System (ADS)

    Cytrynowicz, Debra G.

    The research project itself was the initiation of the development of a planar miniature loop heat pipe based on a capillary wick structure made of coherent porous silicon. Work on this project fell into four main categories, which were component fabrication, test system construction, characterization testing and test data collection, performance analysis and thermal modeling. Component fabrication involved the production of various components for the evaporator. When applicable, these components were to be produced by microelectronic and MEMS or microelectromechanical fabrication techniques. Required work involved analyses and, where necessary, modifications to the wafer processing sequence, the photo-electrochemical etching process, system and controlling computer program to make it more reliable, flexible and efficient. The development of more than one wick production process was also extremely necessary in the event of equipment failure. Work on developing this alternative also involved investigations into various details of the photo-electrochemical etching process itself. Test system construction involved the actual assembly of open and closed loop test systems. Characterization involved developing and administering a series of tests to evaluate the performance of the wicks and test systems. Although there were some indications that the devices were operating according to loop heat pipe theory, they were transient and unstable. Performance analysis involved the construction of a transparent evaporator, which enabled the visual observation of the phenomena, which occurred in the evaporator during operation. It also involved investigating the effect of the quartz wool secondary wick on the operation of the device. Observations made during the visualization study indicated that the capillary and boiling limits were being reached at extremely low values of input power. The work was performed in a collaborative effort between the Biomedical Nanotechnology Research

  20. Fabrication and Characterization of a Porous Silicon Drug Delivery System with an Initiated Chemical Vapor Deposition Temperature-Responsive Coating.

    PubMed

    McInnes, Steven J P; Szili, Endre J; Al-Bataineh, Sameer A; Vasani, Roshan B; Xu, Jingjing; Alf, Mahriah E; Gleason, Karen K; Short, Robert D; Voelcker, Nicolas H

    2016-01-12

    This paper reports on the fabrication of a pSi-based drug delivery system, functionalized with an initiated chemical vapor deposition (iCVD) polymer film, for the sustainable and temperature-dependent delivery of drugs. The devices were prepared by loading biodegradable porous silicon (pSi) with a fluorescent anticancer drug camptothecin (CPT) and coating the surface with temperature-responsive poly(N-isopropylacrylamide-co-diethylene glycol divinyl ether) (pNIPAM-co-DEGDVE) or non-stimulus-responsive poly(aminostyrene) (pAS) via iCVD. CPT released from the uncoated oxidized pSi control with a burst release fashion (∼21 nmol/(cm(2) h)), and this was almost identical at temperatures both above (37 °C) and below (25 °C) the lower critical solution temperature (LCST) of the switchable polymer used, pNIPAM-co-DEGDVE (28.5 °C). In comparison, the burst release rate from the pSi-pNIPAM-co-DEGDVE sample was substantially slower at 6.12 and 9.19 nmol/(cm(2) h) at 25 and 37 °C, respectively. The final amount of CPT released over 16 h was 10% higher at 37 °C compared to 25 °C for pSi coated with pNIPAM-co-DEGDVE (46.29% vs 35.67%), indicating that this material can be used to deliver drugs on-demand at elevated temperatures. pSi coated with pAS also displayed sustainable drug delivery profiles, but these were independent of the release temperature. These data show that sustainable and temperature-responsive delivery systems can be produced by functionalization of pSi with iCVD polymer films. Benefits of the iCVD approach include the application of the iCVD coating after drug loading without causing degradation of the drug commonly caused by exposure to factors such as solvents or high temperatures. Importantly, the iCVD process is applicable to a wide array of surfaces as the process is independent of the surface chemistry and pore size of the nanoporous matrix being coated. PMID:26654169

  1. Thermal and electromechanical characterization of top-down fabricated p-type silicon nanowires

    NASA Astrophysics Data System (ADS)

    Bosseboeuf, Alain; Allain, Pierre Etienne; Parrain, Fabien; Le Roux, Xavier; Isac, Nathalie; Jacob, Serge; Poizat, Alexis; Coste, Philippe; Maaroufi, Seiffedine; Walther, Arnaud

    2015-01-01

    In this paper we report thermal conductivity and piezoresistivity measurements of top-down fabricated highly boron doped (NA = 1.5 × 1019 cm-3) suspended Si nanowires. These measurements were performed in a cryogenic probe station respectively by using the 3 omega method and by in situ application of a longitudinal tensile stress to the nanowire under test with a direct four point bending of the Si nanowire die. Nanowires investigated have a thickness of 160 nm, a width in the 80-260 nm range and a length in the 2.5-5.2 μm range. We found that for these geometries, thermal conduction still obeys Fourier’s law and that, as expected, the thermal conductivity is largely reduced when the nanowires width is shrunk, but, to a lower extent than published values for nanowires grown by vapor-liquid-solid (VLS) processes. While a large giant piezoresistance effect was evidenced by various authors when a static stress is applied, we only observed a limited nanowire size dependence of the piezoresistivity in our experiments where a dynamical mechanical loading is applied. This confirms that the giant piezoresistance effect in unbiased Si nanowires is not an intrinsic bulk effect but is dominated by surface related effects in agreement with the piezopinch effect model. Invited talk at the 7th International Workshop on Advanced Materials Science and Nanotechnology IWAMSN2014, 2-6 November, 2014, Ha Long, Vietnam

  2. Process for forming retrograde profiles in silicon

    DOEpatents

    Weiner, Kurt H.; Sigmon, Thomas W.

    1996-01-01

    A process for forming retrograde and oscillatory profiles in crystalline and polycrystalline silicon. The process consisting of introducing an n- or p-type dopant into the silicon, or using prior doped silicon, then exposing the silicon to multiple pulses of a high-intensity laser or other appropriate energy source that melts the silicon for short time duration. Depending on the number of laser pulses directed at the silicon, retrograde profiles with peak/surface dopant concentrations which vary from 1-1e4 are produced. The laser treatment can be performed in air or in vacuum, with the silicon at room temperature or heated to a selected temperature.

  3. Process for forming retrograde profiles in silicon

    DOEpatents

    Weiner, K.H.; Sigmon, T.W.

    1996-10-15

    A process is disclosed for forming retrograde and oscillatory profiles in crystalline and polycrystalline silicon. The process consisting of introducing an n- or p-type dopant into the silicon, or using prior doped silicon, then exposing the silicon to multiple pulses of a high-intensity laser or other appropriate energy source that melts the silicon for short time duration. Depending on the number of laser pulses directed at the silicon, retrograde profiles with peak/surface dopant concentrations which vary are produced. The laser treatment can be performed in air or in vacuum, with the silicon at room temperature or heated to a selected temperature.

  4. Microstructure and initial growth characteristics of nanocrystalline silicon films fabricated by very high frequency plasma enhanced chemical vapor deposition with highly H{sub 2} dilution of SiH{sub 4}

    SciTech Connect

    Wang Xiang; Huang Rui; Song Jie; Guo Yanqing; Ding Honglin

    2010-06-15

    Nanocrystalline silicon (nc-Si:H) film deposited on silicon oxide in a very high frequency plasma enhanced chemical vapor deposition with highly H{sub 2} dilution of SiH{sub 4} has been investigated by Raman spectroscopy and high resolution transmission electron microscopy. It is found that at early growth stage the initial amorphous incubation layer in nc-Si:H growth on silicon oxide can be almost eliminated and crystallites with diameter of about 6 to 10 nm are directly formed on the silicon oxide. Nearly parallel columnar structures with complex microstructure are found from cross-sectional transmission electron microscopy images of the film. It is considered that highly H{sub 2} dilution and higher excitation frequency are the main reason for eliminating the initial amorphous incubation layer in nc-Si:H growth on silicon oxide.

  5. Microwave Induced Direct Bonding of Single Crystal Silicon Wafers

    NASA Technical Reports Server (NTRS)

    Budraa, N. K.; Jackson, H. W.; Barmatz, M.

    1999-01-01

    We have heated polished doped single-crystal silicon wafers in a single mode microwave cavity to temperatures where surface to surface bonding occurred. The absorption of microwaves and heating of the wafers is attributed to the inclusion of n-type or p-type impurities into these substrates. A cylindrical cavity TM (sub 010) standing wave mode was used to irradiate samples of various geometry's at positions of high magnetic field. This process was conducted in vacuum to exclude plasma effects. This initial study suggests that the inclusion of impurities in single crystal silicon significantly improved its microwave absorption (loss factor) to a point where heating silicon wafers directly can be accomplished in minimal time. Bonding of these substrates, however, occurs only at points of intimate surface to surface contact. The inclusion of a thin metallic layer on the surfaces enhances the bonding process.

  6. (Ga,Fe)Sb: A p-type ferromagnetic semiconductor

    SciTech Connect

    Tu, Nguyen Thanh; Anh, Le Duc; Tanaka, Masaaki; Hai, Pham Nam

    2014-09-29

    A p-type ferromagnetic semiconductor (Ga{sub 1−x},Fe{sub x})Sb (x = 3.9%–13.7%) has been grown by low-temperature molecular beam epitaxy (MBE) on GaAs(001) substrates. Reflection high energy electron diffraction patterns during the MBE growth and X-ray diffraction spectra indicate that (Ga,Fe)Sb layers have the zinc-blende crystal structure without any other crystallographic phase of precipitates. Magnetic circular dichroism (MCD) spectroscopy characterizations indicate that (Ga,Fe)Sb has the zinc-blende band structure with spin-splitting induced by s,p-d exchange interactions. The magnetic field dependence of the MCD intensity and anomalous Hall resistance of (Ga,Fe)Sb show clear hysteresis, demonstrating the presence of ferromagnetic order. The Curie temperature (T{sub C}) increases with increasing x and reaches 140 K at x = 13.7%. The crystal structure analyses, magneto-transport, and magneto-optical properties indicate that (Ga,Fe)Sb is an intrinsic ferromagnetic semiconductor.

  7. Challenges in p-type Doping of CdTe

    NASA Astrophysics Data System (ADS)

    McCoy, Jedidiah; Swain, Santosh; Lynn, Kelvin

    We have made progress in defect identification of arsenic and phosphorous doped CdTe to understand the self-compensation mechanism which will help improve minority bulk carrier lifetime and net acceptor density. Combining previous measurements of un-doped CdTe, we performed a systematic comparison of defects between different types of crystals and confirmed the defects impacting the doping efficiency. CdTe bulk crystals have been grown via vertical Bridgman based melt growth technique with varying arsenic and phosphorous dopant schemes to attain p-type material. Furnace temperature profiles were varied to influence dopant solubility. Large carrier densities have been reproducibly obtained from these boules indicating successful incorporation of dopants into the lattice. However, these values are orders of magnitude lower than theoretical solubility values. Infrared Microscopy has revealed a plethora of geometrically abnormal second phase defects and X-ray Fluorescence has been used to identify the elemental composition of these defects. We believe that dopants become incorporated into these second phase defects as Cd compounds which act to inhibit dopant solubility in the lattice.

  8. Greyscale proton beam writing in p-type Gallium Arsenide

    NASA Astrophysics Data System (ADS)

    Diering, D.; Spemann, D.; Lenzner, J.; Müller, St.; Böntgen, T.; von Wenckstern, H.

    2013-07-01

    Proton beam writing (PBW) is a well known method for micromachining, e.g. of semiconductors. Up to now, only few indication is given on how the resulting structure height in micromachined semiconductors can be controlled by means of fluence variation. This approach for 3D-microstructuring, called Greyscale PBW, was already successfully demonstrated for negative photoresists. In this study (1 0 0) p-type Gallium Arsenide (GaAs) was irradiated with 2.28 MeV protons and fluences in the range from 1.2×1014 H+ cm-2 to 1.0×1018 H+ cm-2 at the ion beam laboratory LIPSION and subsequently electrochemically etched with 10%-KOH. A linear dependency of structure height on ion fluence was established. In this way, pyramid-like structures as well as concave-shaped structures could be created. GaAs showed a lateral anisotropic etch behaviour during the development step with preferential etching along the [0 1 1] directions. On some structures the surface roughness and the change of conductivity were investigated by atomic force and scanning capacitance microscopy, respectively. The rms roughness of the surface of the structures was 5.4 nm and 10.6 nm for a fluence of 7.8×1015 H+ cm-2 and 1.2×1017 H+ cm-2, respectively. We observed an increasing etching rate for fluences larger than 1016 H+ cm-2.

  9. Electronic processes in uniaxially stressed p-type germanium

    SciTech Connect

    Dubon, O.D. Jr.

    1996-02-01

    Effect of uniaxial stress on acceptor-related electronic processes in Ge single crystals doped with Ga, Be, and Cu were studied by Hall and photo-Hall effect measurements in conjunction with infrared spectroscopy. Stress dependence of hole lifetime in p-type Ge single crystals is used as a test for competing models of non-radiative capture of holes by acceptors. Photo-Hall effect shows that hole lifetime in Ga- and Be-doped Ge increases by over one order of magnitude with uniaxial stress at liq. He temps. Photo-Hall of Ge:Be shows a stress-induced change in the temperature dependence of hole lifetime. This is consistent with observed increase of responsivity of Ge:Ga detectors with uniaxial stress. Electronic properties of Ge:Cu are shown to change dramatically with uniaxial stress; the results provide a first explanation for the performance of uniaxially stressed, Cu-diffused Ge:Ga detectors which display a high conductivity in absence of photon signal and therefore have poor sensitivity.

  10. Membrane Targeting of P-type ATPases in Plant Cells

    SciTech Connect

    Jeffrey F. Harper, Ph.D.

    2004-06-30

    How membrane proteins are targeted to specific subcellular locations is a very complex and poorly understood area of research. Our long-term goal is to use P-type ATPases (ion pumps), in a model plant system Arabidopsis, as a paradigm to understand how members of a family of closely related membrane proteins can be targeted to different subcellular locations. The research is divided into two specific aims. The first aim is focused on determining the targeting destination of all 10 ACA-type calcium pumps (Arabidopsis Calcium ATPase) in Arabidopsis. ACAs represent a plant specific-subfamily of plasma membrane-type calcium pumps. In contrast to animals, the plant homologs have been found in multiple membrane systems, including the ER (ACA2), tonoplast (ACA4) and plasma membrane (ACA8). Their high degree of similarity provides a unique opportunity to use a comparative approach to delineate the membrane specific targeting information for each pump. One hypothesis to be tested is that an endomembrane located ACA can be re-directed to the plasma membrane by including targeting information from a plasma membrane isoform, ACA8. Our approach is to engineer domain swaps between pumps and monitor the targeting of chimeric proteins in plant cells using a Green Fluorescence Protein (GFP) as a tag. The second aim is to test the hypothesis that heterologous transporters can be engineered into plants and targeted to the plasma membrane by fusing them to a plasma membrane proton pump. As a test case we are evaluating the targeting properties of fusions made between a yeast sodium/proton exchanger (Sod2) and a proton pump (AHA2). This fusion may potentially lead to a new strategy for engineering salt resistant plants. Together these aims are designed to provide fundamental insights into the biogenesis and function of plant cell membrane systems.

  11. Piezoresistive effect in p-type 3C-SiC at high temperatures characterized using Joule heating

    NASA Astrophysics Data System (ADS)

    Phan, Hoang-Phuong; Dinh, Toan; Kozeki, Takahiro; Qamar, Afzaal; Namazu, Takahiro; Dimitrijev, Sima; Nguyen, Nam-Trung; Dao, Dzung Viet

    2016-06-01

    Cubic silicon carbide is a promising material for Micro Electro Mechanical Systems (MEMS) applications in harsh environ-ments and bioapplications thanks to its large band gap, chemical inertness, excellent corrosion tolerance and capability of growth on a Si substrate. This paper reports the piezoresistive effect of p-type single crystalline 3C-SiC characterized at high temperatures, using an in situ measurement method. The experimental results show that the highly doped p-type 3C-SiC possesses a relatively stable gauge factor of approximately 25 to 28 at temperatures varying from 300 K to 573 K. The in situ method proposed in this study also demonstrated that, the combination of the piezoresistive and thermoresistive effects can increase the gauge factor of p-type 3C-SiC to approximately 20% at 573 K. The increase in gauge factor based on the combination of these phenomena could enhance the sensitivity of SiC based MEMS mechanical sensors.

  12. Piezoresistive effect in p-type 3C-SiC at high temperatures characterized using Joule heating.

    PubMed

    Phan, Hoang-Phuong; Dinh, Toan; Kozeki, Takahiro; Qamar, Afzaal; Namazu, Takahiro; Dimitrijev, Sima; Nguyen, Nam-Trung; Dao, Dzung Viet

    2016-01-01

    Cubic silicon carbide is a promising material for Micro Electro Mechanical Systems (MEMS) applications in harsh environ-ments and bioapplications thanks to its large band gap, chemical inertness, excellent corrosion tolerance and capability of growth on a Si substrate. This paper reports the piezoresistive effect of p-type single crystalline 3C-SiC characterized at high temperatures, using an in situ measurement method. The experimental results show that the highly doped p-type 3C-SiC possesses a relatively stable gauge factor of approximately 25 to 28 at temperatures varying from 300 K to 573 K. The in situ method proposed in this study also demonstrated that, the combination of the piezoresistive and thermoresistive effects can increase the gauge factor of p-type 3C-SiC to approximately 20% at 573 K. The increase in gauge factor based on the combination of these phenomena could enhance the sensitivity of SiC based MEMS mechanical sensors. PMID:27349378

  13. Piezoresistive effect in p-type 3C-SiC at high temperatures characterized using Joule heating

    PubMed Central

    Phan, Hoang-Phuong; Dinh, Toan; Kozeki, Takahiro; Qamar, Afzaal; Namazu, Takahiro; Dimitrijev, Sima; Nguyen, Nam-Trung; Dao, Dzung Viet

    2016-01-01

    Cubic silicon carbide is a promising material for Micro Electro Mechanical Systems (MEMS) applications in harsh environ-ments and bioapplications thanks to its large band gap, chemical inertness, excellent corrosion tolerance and capability of growth on a Si substrate. This paper reports the piezoresistive effect of p-type single crystalline 3C-SiC characterized at high temperatures, using an in situ measurement method. The experimental results show that the highly doped p-type 3C-SiC possesses a relatively stable gauge factor of approximately 25 to 28 at temperatures varying from 300 K to 573 K. The in situ method proposed in this study also demonstrated that, the combination of the piezoresistive and thermoresistive effects can increase the gauge factor of p-type 3C-SiC to approximately 20% at 573 K. The increase in gauge factor based on the combination of these phenomena could enhance the sensitivity of SiC based MEMS mechanical sensors. PMID:27349378

  14. A record setting amorphous silicon alloy triple-junction solar cell with 14.6{percent} initial and 12.8{percent} stable efficiencies

    SciTech Connect

    Yang, J.; Banerjee, A.; Guha, S.

    1997-02-01

    World record 14.6{percent} initial and 12.8{percent} stable conversion efficiencies have been achieved using amorphous silicon based alloy in a spectrum-splitting, triple-junction structure. This performance exceeds our previous record of 13.2{percent} initial and 11.8{percent} stable efficiencies and establishes a new milestone toward reaching the 15{percent} stable module goal. Key factors leading to this major advance include: (a) Improvement in the low bandgap amorphous silicon-germanium component cell that resulted in enhanced red response and provided desired current mismatching, (b) improvement in the pn tunnel junction between component cells by incorporating microcrystalline p and n layers in a multilayered structure that resulted in reduced optical and electrical losses, and (c) improvement in the top conducting oxide that resulted in reduced absorption and enhanced blue response without increasing the top cell thickness. Details of these advances along with light-soaking data for high efficiency cells will be discussed. {copyright} {ital 1997 American Institute of Physics.}

  15. Ti/Al/W Ohmic contacts to p-type implanted 4H-SiC

    NASA Astrophysics Data System (ADS)

    Vivona, M.; Greco, G.; Lo Nigro, R.; Bongiorno, C.; Roccaforte, F.

    2015-07-01

    In this work, the morphological, structural, and electrical properties of Ti/Al/W contacts to p-type implanted silicon carbide (4H-SiC) have been monitored as a function of the annealing temperature (800-1100 °C). The increase of the annealing temperature induces a transition from a rectifying to an Ohmic behavior, with a specific contact resistance of 5.8 × 10-4 Ωcm2. The electrical behavior has been correlated with the morphological and structural analyses. In particular, the transition to an Ohmic behavior was accompanied by a gradual increase of the surface roughness and by the occurrence of a reaction leading to the formation of new phases in the stack and at the interface (TiAl3, W(SiAl)2, and TiC). The presence of Al-rich protrusions penetrating in the SiC substrate was also observed. From the temperature dependence of the electrical parameters, a barrier height of 0.69 eV for this system was determined. The thermal stability of the contacts has been demonstrated for long-term (up to 100 h) thermal cycling at 400 °C.

  16. Picosecond intersubband hole relaxation in p-type quantum wells

    SciTech Connect

    Xu, Z.; Fauchet, P.M.; Rella, C.W.; Schwettman, H.A.

    1995-12-31

    We report the first direct measurement of the relaxation time of holes in p-type quantum wells using tunable, subpicosecond mid-infrared laser pulses in a pump-probe arrangement. The QW layers consisted of 50 In{sub 0.5}Ga{sub 0.5}As/Al{sub 0.5}Ga{sub 0.5}As periods. The In{sub 0.5}Ga{sub 0.5}As well was 4 nm wide and the Al{sub 0.5}Ga{sub 0.5}As barrier was 8 nm wide. The dopant concentration was 10{sup 19} CM{sup -3} which corresponds to a sheet density of 1.2 x 10{sup 13} CM{sup -2}. The room temperature IR spectrum showed a 50 meV wide absorption peak at 5.25 {mu}m (220 meV). This energy agrees with the calculated n=1 heavy hole to n=1 light hole transition energy of 240 meV (150 meV for strain and 90 meV for confinement). The large absorption width results from hole-hole scattering and the difference in dispersion relations between the two subbands. The equal-wavelength pump-probe transmission measurements were performed using the Stanford free electron laser (FEL). The FEL pulses were tuned between 4 and 6 {mu} m and their duration was less than 1 ps. The measurements were performed as a function of temperature, pump wavelength and intensity (from 0.3 to 10 GW/cm{sup 2}). In all our experiments, we find an increase of transmission (decrease of absorption or bleaching) following photopumping, which recovers as a single exponential with a time constant (relaxation time) of the order of 1 picosecond. The maximum change in transmission is linear with pump 2 intensity below 1 GW/cm{sup 2} and saturates to {approximately}3% with a saturation intensity I{sub sat} of 3 GW/cm{sup 2}. As the saturation regime is entered, the relaxation time increases from 0.8 ps to 1.8 ps. This relaxation time depends on the temperature T: it increases from 0.8 ps to 1.3 ps as T decreases from 300 K to 77 K. Finally, when we tune the laser through the absorption band, the magnitude of the signal changes but its temporal behavior does not change, within the accuracy of the measurements.

  17. Modeling of thin, back-wall silicon solar cells

    NASA Technical Reports Server (NTRS)

    Baraona, C. R.

    1979-01-01

    The performance of silicon solar cells with p-n junctions on the nonilluminated surface (i.e., upside-down or back-wall cells) was calculated. These structures consisted of a uniformly shaped p-type substrate layer, a p(+)-type field layer on the front (illuminated) surface, and a shallow, n-type junction on the back (nonilluminated) surface. A four-layer solar cell model was used to calculate efficiency, open-circuit voltage, and short-circuit current. The effect on performance of p-layer thickness and resistivity was determined. The diffusion length was varied to simulate the effect of radiation damage. The results show that peak initial efficiencies greater than 15 percent are possible for cell thicknesses or 100 micrometers or less. After 10 years of radiation damage in geosynchronous orbit, thin (25 to 50 micrometers thick) cells made from 10 to 100 ohm cm material show the smallest decrease (approximately 10 percent) in performance.

  18. Ultraviolet light-emitting diodes with polarization-doped p-type layer

    NASA Astrophysics Data System (ADS)

    Hu, Wenxiao; Qin, Ping; Song, Weidong; Zhang, Chongzhen; Wang, Rupeng; Zhao, Liangliang; Xia, Chao; Yuan, Songyang; Yin, Yian; Li, Shuti

    2016-09-01

    We report ultraviolet light emitting diode (LEDs) with polarization doped p-type layer. Fabricated LEDs with polarization doped p-type layer exhibited reduced forward voltage and enhanced light output power, compared to those with traditional p-type AlGaN layer. The improvement is attributed to improved hole concentration and the smooth valence band by the polarization enhanced p-type doping. Our simulated results reveal that this p-type layer can further enhance the performance of ultraviolet LEDs by removing the electron blocking layer (EBL).

  19. Ultrafast hole carrier relaxation dynamics in p-type CuO nanowires

    PubMed Central

    2011-01-01

    Ultrafast hole carrier relaxation dynamics in CuO nanowires have been investigated using transient absorption spectroscopy. Following femtosecond pulse excitation in a non-collinear pump-probe configuration, a combination of non-degenerate transmission and reflection measurements reveal initial ultrafast state filling dynamics independent of the probing photon energy. This behavior is attributed to the occupation of states by photo-generated carriers in the intrinsic hole region of the p-type CuO nanowires located near the top of the valence band. Intensity measurements indicate an upper fluence threshold of 40 μJ/cm2 where carrier relaxation is mainly governed by the hole dynamics. The fast relaxation of the photo-generated carriers was determined to follow a double exponential decay with time constants of 0.4 ps and 2.1 ps. Furthermore, time-correlated single photon counting measurements provide evidence of three exponential relaxation channels on the nanosecond timescale. PMID:22151927

  20. Purified silicon production system

    DOEpatents

    Wang, Tihu; Ciszek, Theodore F.

    2004-03-30

    Method and apparatus for producing purified bulk silicon from highly impure metallurgical-grade silicon source material at atmospheric pressure. Method involves: (1) initially reacting iodine and metallurgical-grade silicon to create silicon tetraiodide and impurity iodide byproducts in a cold-wall reactor chamber; (2) isolating silicon tetraiodide from the impurity iodide byproducts and purifying it by distillation in a distillation chamber; and (3) transferring the purified silicon tetraiodide back to the cold-wall reactor chamber, reacting it with additional iodine and metallurgical-grade silicon to produce silicon diiodide and depositing the silicon diiodide onto a substrate within the cold-wall reactor chamber. The two chambers are at atmospheric pressure and the system is open to allow the introduction of additional source material and to remove and replace finished substrates.

  1. Synthesis of poly(silanes) and poly(silane)-modified silicones for use as novel initiator systems

    NASA Astrophysics Data System (ADS)

    Goldslager, Barry Andrew

    The development of new methods for the synthesis of polymeric silanes represents an exciting new field in organosilicon chemistry. The synthetic methods developed in this research were used to produce reactive polymeric silanes which in turn were used in applications as photoinitiators/modifiers or as self curing resins. This thesis describes investigations of the synthesis of a variety of reactive polymeric silanes, modification of the polymeric silanes and their use as photoinitiators and self curing resins. The silanes were synthesized by either Wurtz type coupling, which uses a sodium dispersion to couple halogenated silanes together, or by metallocene catalysis, which uses transition metal catalysts to couple silicon hydrides together through dehydrogenative coupling. The resulting materials were demonstrated to be useful as photoinitiators for acrylic/methacrylic systems and that they can be modified for use in other systems. The modification of the polymeric silanes where carried out using a either a hydrosilylation reaction which involves the coupling of an active silicon hydride with an active vinyl group, or a condensation reaction between an active chlorosilane with an active hydroxyl group. Several unique materials were synthesized using these two methods and consist of the following: (1) Linear poly(phenylsdane)-graft-vinyl terminated poly(dimethylsiloxane); (2) Networked poly(phenylisdane)-graft-vinyl terminated poly(dimethylsiloxane); (3) Oligo(methylphenyisilane)-alt-vinyl terminated poly(dimethylsiloxane); (4) Various polymeric silanes. These materials where successfully used as photoinitators for acrylate and methacrylate systems such as isobornyl acrylate, 2-hydroxypropyl acrylate, vinyl terminated polydimethylsiloxane, and self curing resins which showed excellent properties such as nontacky surfaces, high glass transition temperatures, Tgs, and crosslinked materials for use as potting agents. The modified silanes showed good solubility in many

  2. Method and apparatus for stable silicon dioxide layers on silicon grown in silicon nitride ambient

    NASA Technical Reports Server (NTRS)

    Cohen, R. A.; Wheeler, R. K. (Inventor)

    1974-01-01

    A method and apparatus for thermally growing stable silicon dioxide layers on silicon is disclosed. A previously etched and baked silicon nitride tube placed in a furnace is used to grow the silicon dioxide. First, pure oxygen is allowed to flow through the tube to initially coat the inside surface of the tube with a thin layer of silicon dioxide. After the tube is coated with the thin layer of silicon dioxide, the silicon is oxidized thermally in a normal fashion. If the tube becomes contaminated, the silicon dioxide is etched off thereby exposing clean silicon nitride and then the inside of the tube is recoated with silicon dioxide. As is disclosed, the silicon nitride tube can also be used as the ambient for the pyrolytic decomposition of silane and ammonia to form thin layers of clean silicon nitride.

  3. Photovoltaic Cell Having A P-Type Polycrystalline Layer With Large Crystals

    DOEpatents

    Albright, Scot P.; Chamberlin, Rhodes R.

    1996-03-26

    A photovoltaic cell has an n-type polycrystalline layer and a p-type polycrystalline layer adjoining the n-type polycrystalline layer to form a photovoltaic junction. The p-type polycrystalline layer comprises a substantially planar layer portion having relatively large crystals adjoining the n-type polycrystalline layer. The planar layer portion includes oxidized impurities which contribute to obtainment of p-type electrical properties in the planar layer portion.

  4. Stress effects on the initial lithiation of crystalline silicon nanowires: Reactive molecular dynamics simulations using ReaxFF

    DOE PAGESBeta

    Ostadhossein, Alireza; Cubuk, Ekin D.; Tritsaris, Georgios A.; Kaxiras, Efthimios; Zhang, Sulin; Adri C. T. van Duin

    2014-12-18

    Silicon (Si) has been recognized as a promising anode material for the next-generation high-capacity lithium (Li)-ion batteries because of its high theoretical energy density. Recent in situ transmission electron microscopy (TEM) revealed that the electrochemical lithiation of crystalline Si nanowires (c-SiNWs) proceeds by the migration of the interface between the lithiated Si (LixSi) shell and the pristine unlithiated core, accompanied by solid-state amorphization. The underlying atomic mechanisms of Li insertion into c-Si remain poorly understood. In this research, we perform molecular dynamics (MD) simulations using the reactive force field (ReaxFF) to characterize the lithiation process of c-SiNWs. Our calculations showmore » that ReaxFF can accurately reproduce the energy barriers of Li migration from DFT calculations in both crystalline (c-Si) and amorphous Si (a-Si). The ReaxFF-based MD simulations reveal that Li insertion into interlayer spacing between two adjacent (111) planes results in the peeling-off of the (111) facets and subsequent amorphization, in agreement with experimental observations. We find that breaking of the Si–Si bonds between (111)-bilayers requires a rather high local Li concentration, which explains the atomically sharp amorphous–crystalline interface (ACI). Our stress analysis shows that lithiation induces compressive stress at the ACI layer, causing retardation or even the stagnation of the reaction front, also in good agreement with TEM observations. Lithiation at high temperatures (e.g. 1200 K) shows that Li insertion into c-SiNW results in an amorphous to crystalline phase transformation at Li : Si composition of ~4.2:1. In conclusion, our modeling results provide a comprehensive picture of the effects of reaction and diffusion-induced stress on the interfacial dynamics and mechanical degradation of SiNW anodes under chemo-mechanical lithiation.« less

  5. Stress effects on the initial lithiation of crystalline silicon nanowires: reactive molecular dynamics simulations using ReaxFF.

    PubMed

    Ostadhossein, Alireza; Cubuk, Ekin D; Tritsaris, Georgios A; Kaxiras, Efthimios; Zhang, Sulin; van Duin, Adri C T

    2015-02-01

    Silicon (Si) has been recognized as a promising anode material for the next-generation high-capacity lithium (Li)-ion batteries because of its high theoretical energy density. Recent in situ transmission electron microscopy (TEM) revealed that the electrochemical lithiation of crystalline Si nanowires (c-SiNWs) proceeds by the migration of the interface between the lithiated Si (LixSi) shell and the pristine unlithiated core, accompanied by solid-state amorphization. The underlying atomic mechanisms of Li insertion into c-Si remain poorly understood. Herein, we perform molecular dynamics (MD) simulations using the reactive force field (ReaxFF) to characterize the lithiation process of c-SiNWs. Our calculations show that ReaxFF can accurately reproduce the energy barriers of Li migration from DFT calculations in both crystalline (c-Si) and amorphous Si (a-Si). The ReaxFF-based MD simulations reveal that Li insertion into interlayer spacing between two adjacent (111) planes results in the peeling-off of the (111) facets and subsequent amorphization, in agreement with experimental observations. We find that breaking of the Si-Si bonds between (111)-bilayers requires a rather high local Li concentration, which explains the atomically sharp amorphous-crystalline interface (ACI). Our stress analysis shows that lithiation induces compressive stress at the ACI layer, causing retardation or even the stagnation of the reaction front, also in good agreement with TEM observations. Lithiation at high temperatures (e.g. 1200 K) shows that Li insertion into c-SiNW results in an amorphous to crystalline phase transformation at Li : Si composition of ∼4.2 : 1. Our modeling results provide a comprehensive picture of the effects of reaction and diffusion-induced stress on the interfacial dynamics and mechanical degradation of SiNW anodes under chemo-mechanical lithiation. PMID:25559797

  6. Stress effects on the initial lithiation of crystalline silicon nanowires: Reactive molecular dynamics simulations using ReaxFF

    SciTech Connect

    Ostadhossein, Alireza; Cubuk, Ekin D.; Tritsaris, Georgios A.; Kaxiras, Efthimios; Zhang, Sulin; Adri C. T. van Duin

    2014-12-18

    Silicon (Si) has been recognized as a promising anode material for the next-generation high-capacity lithium (Li)-ion batteries because of its high theoretical energy density. Recent in situ transmission electron microscopy (TEM) revealed that the electrochemical lithiation of crystalline Si nanowires (c-SiNWs) proceeds by the migration of the interface between the lithiated Si (LixSi) shell and the pristine unlithiated core, accompanied by solid-state amorphization. The underlying atomic mechanisms of Li insertion into c-Si remain poorly understood. In this research, we perform molecular dynamics (MD) simulations using the reactive force field (ReaxFF) to characterize the lithiation process of c-SiNWs. Our calculations show that ReaxFF can accurately reproduce the energy barriers of Li migration from DFT calculations in both crystalline (c-Si) and amorphous Si (a-Si). The ReaxFF-based MD simulations reveal that Li insertion into interlayer spacing between two adjacent (111) planes results in the peeling-off of the (111) facets and subsequent amorphization, in agreement with experimental observations. We find that breaking of the Si–Si bonds between (111)-bilayers requires a rather high local Li concentration, which explains the atomically sharp amorphous–crystalline interface (ACI). Our stress analysis shows that lithiation induces compressive stress at the ACI layer, causing retardation or even the stagnation of the reaction front, also in good agreement with TEM observations. Lithiation at high temperatures (e.g. 1200 K) shows that Li insertion into c-SiNW results in an amorphous to crystalline phase transformation at Li : Si composition of ~4.2:1. In conclusion, our modeling results provide a comprehensive picture of the effects of reaction and diffusion-induced stress on the interfacial dynamics and mechanical degradation of SiNW anodes under chemo-mechanical lithiation.

  7. Diffusion of hydrogen in perfect, p -type doped, and radiation-damaged 4H-SiC

    NASA Astrophysics Data System (ADS)

    Aradi, B.; Deák, P.; Gali, A.; Son, N. T.; Janzén, E.

    2004-06-01

    The diffusion of interstitial atomic hydrogen in 4H-SiC was investigated theoretically, using the local density approximation of density functional theory. We have found that the diffusion barrier in the perfect crystal is ⩽0.6 eV . Comparing this value with the calculated zero point vibration energy of interstitial hydrogen indicates that hydrogen diffuses very rapidly in perfect portions of the SiC lattice, until it gets trapped. In p -doped (B, Al) material the dissociation of the hydrogen-acceptor complexes is the limiting step in diffusion, with a calculated dissociation energy of 2.5 and 1.6 eV for B+H and Al+H , respectively. In irradiated material the trapping and detrapping of hydrogen by silicon vacancies determines the effective diffusion barrier, which lies between 4.0 and 5.3 eV depending on the Fermi level in p -type and weakly n -type material.

  8. Capacitance transients in p-type GaAs MOS structures and application to lifetime mapping during solar cell fabrication

    NASA Technical Reports Server (NTRS)

    Vitale, G.; Loferski, J. J.; Ercil, Y.

    1979-01-01

    Fabrication on p-type GaAs of MOS structures in which the quality of the oxide is such that the surface can be driven into deep inversion by a voltage pulse is reported. The capacitance transients in such MOS capacitors as a function of step amplitude and temperature were measured and the transients were analyzed by an extension of a method for silicon. The oxides were produced by plasma oxidation on an LPE-grown p-type GaAs specimen with N sub A of 3x10 to the 17th power/cu cm. The capacitors were produced by depositing 50 microns-diameter gold dots over the native oxide and, therefore, the lifetime is localized to the area under the dot. The method permits extraction of both the bulk lifetime and the interface recombination velocity. These parameters on samples with different N sub A were measured and a correlation between tau sub g and N sub A was found.

  9. Schottky barrier amorphous silicon solar cell with thin doped region adjacent metal Schottky barrier

    DOEpatents

    Carlson, David E.; Wronski, Christopher R.

    1979-01-01

    A Schottky barrier amorphous silicon solar cell incorporating a thin highly doped p-type region of hydrogenated amorphous silicon disposed between a Schottky barrier high work function metal and the intrinsic region of hydrogenated amorphous silicon wherein said high work function metal and said thin highly doped p-type region forms a surface barrier junction with the intrinsic amorphous silicon layer. The thickness and concentration of p-type dopants in said p-type region are selected so that said p-type region is fully ionized by the Schottky barrier high work function metal. The thin highly doped p-type region has been found to increase the open circuit voltage and current of the photovoltaic device.

  10. Aluminum-silicon eutectic alloy improves electrical and mechanical contact to silicon carbide

    NASA Technical Reports Server (NTRS)

    Shier, J. S.

    1970-01-01

    Alloy contact layer is made at relatively low temperature and has good wetting characteristics. Contacts adhere well to silicon carbide surface, penetrating about 300 to 500 angstroms into it. Contacts are ohmic on p-type silicon carbide and blocking on n-type.

  11. Ultra-thin ohmic contacts for p-type nitride light emitting devices

    DOEpatents

    Raffetto, Mark; Bharathan, Jayesh; Haberern, Kevin; Bergmann, Michael; Emerson, David; Ibbetson, James; Li, Ting

    2012-01-03

    A semiconductor based Light Emitting Device (LED) can include a p-type nitride layer and a metal ohmic contact, on the p-type nitride layer. The metal ohmic contact can have an average thickness of less than about 25 .ANG. and a specific contact resistivity less than about 10.sup.-3 ohm-cm.sup.2.

  12. Piezoresistance behaviors of p-type 6H-SiC nanowires.

    PubMed

    Gao, Fengmei; Zheng, Jinju; Wang, Mingfang; Wei, Guodong; Yang, Weiyou

    2011-11-21

    We reported, for the first time, the piezoresistance behaviors of single p-type 6H-SiC nanowires. The results suggest that present p-type 6H-SiC nanowires could be an excellent candidate for the fabrication of robust and reliable stress sensors. PMID:21959148

  13. Luminance behavior of lithium-doped ZnO nanowires with p-type conduction characteristics.

    PubMed

    Ko, Won Bae; Lee, Jun Seok; Lee, Sang Hyo; Cha, Seung Nam; Sohn, Jung Inn; Kim, Jong Min; Park, Young Jun; Kim, Hyun Jung; Hong, Jin Pyo

    2013-09-01

    The present study describes the room-temperature cathodeluminescence (CL) and temperature-dependent photoluminescence (PL) properties of p-type lithium (Li)-doped zinc oxide (ZnO) nanowires (NWs) grown by hydrothermal doping and post-annealing processes. A ZnO thin film was used as a seed layer in NW growth. The emission wavelengths and intensities of undoped ZnO NWs and p-type Li-doped ZnO NWs were analyzed for comparison. CL and PL observations of post-annealed p-type Li-doped ZnO NWs clearly exhibited a dominant sharp band-edge emission. Finally, a n-type ZnO thin film/p-type annealed Li-doped ZnO NW homojunction diode was prepared to confirm the p-type conduction of annealed Li-doped ZnO NWs as well as the structural properties measured by transmission electron microscopy. PMID:24205635

  14. Piezoresistance and hole transport in beryllium-doped silicon.

    NASA Technical Reports Server (NTRS)

    Littlejohn, M. A.; Robertson, J. B.

    1972-01-01

    The resistivity and piezoresistance of p-type silicon doped with beryllium have been studied as a function of temperature, crystal orientation, and beryllium doping concentration. It is shown that the temperature coefficient of resistance can be varied and reduced to zero near room temperature by varying the beryllium doping level. Similarly, the magnitude of the piezoresistance gauge factor for beryllium-doped silicon is slightly larger than for silicon doped with a shallow acceptor impurity such as boron, while the temperature coefficient of piezoresistance is about the same for material containing these two dopants. These results are discussed in terms of a model for the piezoresistance of compensated p-type silicon.

  15. Palladium contamination in silicon

    NASA Astrophysics Data System (ADS)

    Polignano, M. L.; Mica, I.; Ceresoli, M.; Codegoni, D.; Somaini, F.; Bianchi, I.; Volonghi, D.

    2015-04-01

    In this work palladium is characterized as a silicon contaminant by recombination lifetime, DLTS, C-V and C-t measurements of palladium-implanted wafers. Palladium introduced by ion implantation is found to remain in the solid solution in silicon after rapid thermal treatments, and to be a very effective recombination center. For this reason recombination lifetime measurements are the most sensitive method to detect palladium in silicon. Two palladium-related levels were found by DLTS in p-type material. One of these levels corresponds to a level reported in the literature as the single donor level of substitutional palladium. For what concerns MOS capacitors, palladium is responsible for negative oxide charge and for degradation of the generation lifetime. In addition, palladium is confirmed to be a very fast diffuser, which segregates at the wafer surface even with low temperature treatments (250 °C). Microscopy inspections showed that palladium precipitates and surface defects were formed upon segregation.

  16. Unipolar p-type single-walled carbon nanotube field-effect transistors using TTF-TCNQ as the contact material.

    PubMed

    Xian, Xiaojun; Yan, Kai; Zhou, Wei; Jiao, Liying; Wu, Zhongyun; Liu, Zhongfan

    2009-12-16

    We demonstrate herein that organic metal tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) can serve as an ideal material for source and drain electrodes to build unipolar p-type single-walled carbon nanotube (SWNTs) field-effect transistors (FETs). SWNTs were synthesized by the chemical vapor deposition (CVD) method on silicon wafer and then TTF-TCNQ was deposited by thermal evaporation through a shadow mask to form the source and drain contacts. An SiO2 layer served as the gate dielectric and Si was used as the backgate. Transfer characteristics show that these TTF-TCNQ contacted devices are Schottky barrier transistors just like conventional metal contacted SWNT-FETs. The most interesting characteristic of these SWNT transistors is that all devices demonstrate the unipolar p-type transport behavior. This behavior originates from the unique crystal structure and physical properties of TTF-TCNQ and this device may have potential applications in carbon nanotube electronics. PMID:19923654

  17. Unipolar p-type single-walled carbon nanotube field-effect transistors using TTF-TCNQ as the contact material

    NASA Astrophysics Data System (ADS)

    Xian, Xiaojun; Yan, Kai; Zhou, Wei; Jiao, Liying; Wu, Zhongyun; Liu, Zhongfan

    2009-12-01

    We demonstrate herein that organic metal tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) can serve as an ideal material for source and drain electrodes to build unipolar p-type single-walled carbon nanotube (SWNTs) field-effect transistors (FETs). SWNTs were synthesized by the chemical vapor deposition (CVD) method on silicon wafer and then TTF-TCNQ was deposited by thermal evaporation through a shadow mask to form the source and drain contacts. An SiO2 layer served as the gate dielectric and Si was used as the backgate. Transfer characteristics show that these TTF-TCNQ contacted devices are Schottky barrier transistors just like conventional metal contacted SWNT-FETs. The most interesting characteristic of these SWNT transistors is that all devices demonstrate the unipolar p-type transport behavior. This behavior originates from the unique crystal structure and physical properties of TTF-TCNQ and this device may have potential applications in carbon nanotube electronics.

  18. High performance p-type thermoelectric materials and methods of preparation

    NASA Technical Reports Server (NTRS)

    Caillat, Thierry (Inventor); Borshchevsky, Alexander (Inventor); Fleurial, Jean-Pierre (Inventor)

    2005-01-01

    The present invention is embodied in high performance p-type thermoelectric materials having enhanced thermoelectric properties and the methods of preparing such materials. In one aspect of the invention, p-type semiconductors of formula Zn4-xAxSb3-yBy wherein 0?x?4, A is a transition metal, B is a pnicogen, and 0?y?3 are formed for use in manufacturing thermoelectric devices with substantially enhanced operating characteristics and improved efficiency. Two methods of preparing p-type Zn4Sb3 and related alloys of the present invention include a crystal growth method and a powder metallurgy method.

  19. Design of Shallow p-type Dopants in ZnO (Presentation)

    SciTech Connect

    Wei, S.H.; Li, J.; Yan. Y.

    2008-05-01

    ZnO is a promising material for short wave-length opto-electronic devices such as UV lasers and LEDs due to its large exciton binding energy and low material cost. ZnO can be doped easily n-type, but the realization of stable p-type ZnO is rather difficult. Using first-principles band structure methods the authors address what causes the p-type doping difficulty in ZnO and how to overcome the p-type doping difficulty in ZnO.

  20. Gamma Radiation Damage in Silicon

    NASA Astrophysics Data System (ADS)

    Chang, Chensen

    A theory for interpreting carrier removal in terms of trap production has been derived from the carrier distribution function, which provides a relationship between the carrier removal rate and trap production rates due to the radiation damage. The carrier removal rate is a function of trap production as well as Fermi level position. Also, the carrier removal rate depends on many parameters, which are the density of states of the valance band as well as the conduction band, density of doping impurities, temperature, location of donor and acceptor energy levels and location of trap energy levels. P-type and n-type silicon Schottky diodes are irradiated by cobalt 60 gamma rays. The experimental results show that the carrier removal rate is dependent on the initial carrier concentration. Carrier concentrations are determined by room temperature C-V measurements while the trap production rates are determined by DLTS from measurements from 50 K to room temperature. A model presented by Williams, et al. for the carrier concentration vs. fluence, has been rederived from simple semiconductor carrier statistical mechanics. This model has then been extended to yield an expression for the initial carrier removal rate which depends on the production rate of each defect trap level in the band gap. We have tested these models thoroughly for the first time by measuring the trap production rates by DLTS, and then, using this information to calculate carrier removal rate and carrier concentration vs. fluence, we have verified that the results of the model can explain these same relationships obtained experimentally by C-V measurements. We believe that this is the first time that DLTS results have been linked directly to such simple and useful measurements as carrier removal rate and carrier concentration vs. fluence in a convincing manner. The success of this procedure also suggests that there are no "hidden" levels or traps which contribute to carrier removal rate but which do not

  1. PRECISE THROUGHPUT DETERMINATION OF THE PanSTARRS TELESCOPE AND THE GIGAPIXEL IMAGER USING A CALIBRATED SILICON PHOTODIODE AND A TUNABLE LASER: INITIAL RESULTS

    SciTech Connect

    Stubbs, Christopher W.; Doherty, Peter; Cramer, Claire; Narayan, Gautham; Brown, Yorke J.; Lykke, Keith R.; Woodward, John T.; Tonry, John L.

    2010-12-15

    We have used a precision-calibrated photodiode as the fundamental metrology reference in order to determine the relative throughput of the PanSTARRS telescope and the Gigapixel imager, from 400 nm to 1050 nm. Our technique uses a tunable laser as a source of illumination on a transmissive flat-field screen. We determine the full-aperture system throughput as a function of wavelength, including (in a single integral measurement) the mirror reflectivity, the transmission functions of the filters and the corrector optics, and the detector quantum efficiency, by comparing the light seen by each pixel in the CCD array to that measured by a precision-calibrated silicon photodiode. This method allows us to determine the relative throughput of the entire system as a function of wavelength, for each pixel in the instrument, without observations of celestial standards. We present promising initial results from this characterization of the PanSTARRS system, and we use synthetic photometry to assess the photometric perturbations due to throughput variation across the field of view.

  2. Sol-gel method of p-type zinc oxide films preparation

    NASA Astrophysics Data System (ADS)

    Poghosyan, Armen R.; Li, XiaoNan; Manukyan, Alexandr L.; Grigoryan, Stepan G.; Vardanyan, Eduard S.

    2007-09-01

    Both n-type and p-type ZnO will be required for development of homojunction light-emitting diodes and laser diodes. It is easy to obtain strong n-type ZnO, but very difficult to create consistent, reliable, high-conductivity p-type material. Here we present our investigations of p-type ZnO thin film preparation by sol-gel method using single Li doping and Ga(Al)+N codoping technique. ZnO thin films with c-axis orientation have been prepared on glass substrates. Zn acetate dihydrate, gallium nitrate and acetamide were used as zinc, gallium and nitrogen precursors respectively. SEM, X-ray diffraction, electric conductivity and Hall effect measurements were carried out. The results show that p-type conducting ZnO films with hole concentrations as high as 5x10 17 cm -3 were obtained by this method.

  3. Opto-electrical properties of Sb-doped p-type ZnO nanowires

    SciTech Connect

    Kao, Tzu-Hsuan; Chen, Jui-Yuan; Chiu, Chung-Hua; Huang, Chun-Wei; Wu, Wen-Wei

    2014-03-17

    P-type ZnO nanowires (NWs) have attracted much attention in the past years due to the potential applications for optoelectronics and piezotronics. In this study, we have synthesized Sb-doped p-type ZnO NWs on Si (100) substrates by chemical vapor deposition with Aucatalyst. The Sb-doped ZnO NWs are single crystalline with high density, grown along [1-1-2] direction. The doping percentage of Sb is about 2.49%, which has been confirmed by X-ray photoelectron spectroscopy. The ZnO NW field effect transistor demonstrated its p-type characteristics. A high responsivity to ultraviolet photodetection was also observed. In addition, compared to intrinsic ZnO NWs, the conductivity of the Sb-doped ZnO NWs exhibited ∼2 orders of magnitude higher. These properties make the p-type ZnO NWs a promising candidate for electronic and optoelectronic devices.

  4. Comparison of junctionless and inversion-mode p-type metal-oxide-semiconductor field-effect transistors in presence of hole-phonon interactions

    NASA Astrophysics Data System (ADS)

    Dib, E.; Carrillo-Nuñez, H.; Cavassilas, N.; Bescond, M.

    2016-01-01

    Junctionless transistors are being considered as one of the alternatives to conventional metal-oxide field-effect transistors. In this work, it is then presented a simulation study of silicon double-gated p-type junctionless transistors compared with its inversion-mode counterpart. The quantum transport problem is solved within the non-equilibrium Green's function formalism, whereas hole-phonon interactions are tackled by means of the self-consistent Born approximation. Our findings show that junctionless transistors should perform as good as a conventional transistor only for ultra-thin channels, with the disadvantage of requiring higher supply voltages in thicker channel configurations.

  5. Microgravity silicon zoning investigation

    NASA Technical Reports Server (NTRS)

    Kern, E. L.; Gill, G. L., Jr.

    1983-01-01

    A resistance heated zoner, suitable for early zoning experiments with silicon, was designed and put into operation. The initial power usage and size was designed for an shown to be compatible with payload carriers contemplated for the Shuttle. This equipment will be used in the definition and development of flight experiments and apparatus for float zoning silicon and other materials in microgravity.

  6. Effect of p-type multi-walled carbon nanotubes for improving hydrogen storage behaviors

    SciTech Connect

    Lee, Seul-Yi; Yop Rhee, Kyong; Nahm, Seung-Hoon; Park, Soo-Jin

    2014-02-15

    In this study, the hydrogen storage behaviors of p-type multi-walled carbon nanotubes (MWNTs) were investigated through the surface modification of MWNTs by immersing them in sulfuric acid (H{sub 2}SO{sub 4}) and hydrogen peroxide (H{sub 2}O{sub 2}) at various ratios. The presence of acceptor-functional groups on the p-type MWNT surfaces was confirmed by X-ray photoelectron spectroscopy. Measurement of the zeta-potential determined the surface charge transfer and dispersion of the p-type MWMTs, and the hydrogen storage capacity was evaluated at 77 K and 1 bar. From the results obtained, it was found that acceptor-functional groups were introduced onto the MWNT surfaces, and the dispersion of MWNTs could be improved depending on the acid-mixed treatment conditions. The hydrogen storage was increased by acid-mixed treatments of up to 0.36 wt% in the p-type MWNTs, compared with 0.18 wt% in the As-received MWNTs. Consequently, the hydrogen storage capacities were greatly influenced by the acceptor-functional groups of p-type MWNT surfaces, resulting in increased electron acceptor–donor interaction at the interfaces. - Graphical abstract: Hydrogen storage behaviors of the p-type MWNTs with the acid-mixed treatments are described. Display Omitted Display Omitted.

  7. Convergence of valence bands for high thermoelectric performance for p-type InN

    NASA Astrophysics Data System (ADS)

    Li, Hai-Zhu; Li, Ruo-Ping; Liu, Jun-Hui; Huang, Ming-Ju

    2015-12-01

    Band engineering to converge the bands to achieve high valley degeneracy is one of effective approaches for designing ideal thermoelectric materials. Convergence of many valleys in the valence band may lead to a high Seebeck coefficient, and induce promising thermoelectric performance of p-type InN. In the current work, we have systematically investigated the electronic structure and thermoelectric performance of wurtzite InN by using the density functional theory combined with semiclassical Boltzmann transport theory. Form the results, it can be found that intrinsic InN has a large Seebeck coefficient (254 μV/K) and the largest value of ZeT is 0.77. The transport properties of p-type InN are better than that of n-type one at the optimum carrier concentration, which mainly due to the large Seebeck coefficient for p-type InN, although the electrical conductivity of n-type InN is larger than that of p-type one. We found that the larger Seebeck coefficient for p-type InN may originate from the large valley degeneracy in the valence band. Moreover, the low minimum lattice thermal conductivity for InN is one key factor to become a good thermoelectric material. Therefore, p-type InN could be a potential material for further applications in the thermoelectric area.

  8. Atomic scale investigation of silicon nanowires and nanoclusters

    PubMed Central

    2011-01-01

    In this study, we have performed nanoscale characterization of Si-clusters and Si-nanowires with a laser-assisted tomographic atom probe. Intrinsic and p-type silicon nanowires (SiNWs) are elaborated by chemical vapor deposition method using gold as catalyst, silane as silicon precursor, and diborane as dopant reactant. The concentration and distribution of impurity (gold) and dopant (boron) in SiNW are investigated and discussed. Silicon nanoclusters are produced by thermal annealing of silicon-rich silicon oxide and silica multilayers. In this process, atom probe tomography (APT) provides accurate information on the silicon nanoparticles and the chemistry of the nanolayers. PMID:21711788

  9. Electronic transport properties of silicon clusters

    NASA Astrophysics Data System (ADS)

    Matsuura, Yukihito

    2016-02-01

    The electronic transport properties of silicon clusters were examined via theoretical calculations using the first-principles method. Additionally, p-type doping and n-type doping were analyzed by calculating conductance and current of boron- and phosphorus-doped silicon clusters. The p-type doping and n-type doping provided a new transmission peak at an energy level around the Fermi level to increase conductance. Furthermore, simultaneous boron and phosphorus doping resulted in noticeable rectifying characteristics, with the current drive in forward bias being three times higher than that in the reverse bias. A p-n junction was achieved even on a molecular scale.

  10. Crystallization of amorphous silicon thin films deposited by PECVD on nickel-metalized porous silicon

    PubMed Central

    2012-01-01

    Porous silicon layers were elaborated by electrochemical etching of heavily doped p-type silicon substrates. Metallization of porous silicon was carried out by immersion of substrates in diluted aqueous solution of nickel. Amorphous silicon thin films were deposited by plasma-enhanced chemical vapor deposition on metalized porous layers. Deposited amorphous thin films were crystallized under vacuum at 750°C. Obtained results from structural, optical, and electrical characterizations show that thermal annealing of amorphous silicon deposited on Ni-metalized porous silicon leads to an enhancement in the crystalline quality and physical properties of the silicon thin films. The improvement in the quality of the film is due to the crystallization of the amorphous film during annealing. This simple and easy method can be used to produce silicon thin films with high quality suitable for thin film solar cell applications. PMID:22901341

  11. Crystallization of amorphous silicon thin films deposited by PECVD on nickel-metalized porous silicon.

    PubMed

    Ben Slama, Sonia; Hajji, Messaoud; Ezzaouia, Hatem

    2012-01-01

    Porous silicon layers were elaborated by electrochemical etching of heavily doped p-type silicon substrates. Metallization of porous silicon was carried out by immersion of substrates in diluted aqueous solution of nickel. Amorphous silicon thin films were deposited by plasma-enhanced chemical vapor deposition on metalized porous layers. Deposited amorphous thin films were crystallized under vacuum at 750°C. Obtained results from structural, optical, and electrical characterizations show that thermal annealing of amorphous silicon deposited on Ni-metalized porous silicon leads to an enhancement in the crystalline quality and physical properties of the silicon thin films. The improvement in the quality of the film is due to the crystallization of the amorphous film during annealing. This simple and easy method can be used to produce silicon thin films with high quality suitable for thin film solar cell applications. PMID:22901341

  12. Electrical property comparison and charge transmission in p-type double gate and single gate junctionless accumulation transistor fabricated by AFM nanolithography.

    PubMed

    Dehzangi, Arash; Abdullah, A Makarimi; Larki, Farhad; Hutagalung, Sabar D; Saion, Elias B; Hamidon, Mohd N; Hassan, Jumiah; Gharayebi, Yadollah

    2012-01-01

    The junctionless nanowire transistor is a promising alternative for a new generation of nanotransistors. In this letter the atomic force microscopy nanolithography with two wet etching processes was implemented to fabricate simple structures as double gate and single gate junctionless silicon nanowire transistor on low doped p-type silicon-on-insulator wafer. The etching process was developed and optimized in the present work compared to our previous works. The output, transfer characteristics and drain conductance of both structures were compared. The trend for both devices found to be the same but differences in subthreshold swing, 'on/off' ratio, and threshold voltage were observed. The devices are 'on' state when performing as the pinch off devices. The positive gate voltage shows pinch off effect, while the negative gate voltage was unable to make a significant effect on drain current. The charge transmission in devices is also investigated in simple model according to a junctionless transistor principal. PMID:22781031

  13. Controllable nondegenerate p-type doping of tungsten diselenide by octadecyltrichlorosilane.

    PubMed

    Kang, Dong-Ho; Shim, Jaewoo; Jang, Sung Kyu; Jeon, Jeaho; Jeon, Min Hwan; Yeom, Geun Young; Jung, Woo-Shik; Jang, Yun Hee; Lee, Sungjoo; Park, Jin-Hong

    2015-02-24

    Despite heightened interest in 2D transition-metal dichalcogenide (TMD) doping methods for future layered semiconductor devices, most doping research is currently limited to molybdenum disulfide (MoS2), which is generally used for n-channel 2D transistors. In addition, previously reported TMD doping techniques result in only high-level doping concentrations (degenerate) in which TMD materials behave as near-metallic layers. Here, we demonstrate a controllable nondegenerate p-type doping (p-doping) technique on tungsten diselenide (WSe2) for p-channel 2D transistors by adjusting the concentration of octadecyltrichlorosilane (OTS). This p-doping phenomenon originates from the methyl (-CH3) functional groups in OTS, which exhibit a positive pole and consequently reduce the electron carrier density in WSe2. The controlled p-doping levels are between 2.1 × 10(11) and 5.2 × 10(11) cm(-2) in the nondegenerate regime, where the performance parameters of WSe2-based electronic and optoelectronic devices can be properly designed or optimized (threshold voltage↑, on-/off-currents↑, field-effect mobility↑, photoresponsivity↓, and detectivity↓ as the doping level increases). The p-doping effect provided by OTS is sustained in ambient air for a long time showing small changes in the device performance (18-34% loss of ΔVTH initially achieved by OTS doping for 60 h). Furthermore, performance degradation is almost completely recovered by additional thermal annealing at 120 °C. Through Raman spectroscopy and electrical/optical measurements, we have also confirmed that the OTS doping phenomenon is independent of the thickness of the WSe2 films. We expect that our controllable p-doping method will make it possible to successfully integrate future layered semiconductor devices. PMID:25629805

  14. Segmentation of the Outer Contact on P-Type Coaxial Germanium Detectors

    SciTech Connect

    Hull, Ethan L.; Pehl, Richard H.; Lathrop, James R.; Martin, Gregory N.; Mashburn, R. B.; Miley, Harry S.; Aalseth, Craig E.; Hossbach, Todd W.

    2006-09-21

    Germanium detector arrays are needed for low-level counting facilities. The practical applications of such user facilities include characterization of low-level radioactive samples. In addition, the same detector arrays can also perform important fundamental physics measurements including the search for rare events like neutrino-less double-beta decay. Coaxial germanium detectors having segmented outer contacts will provide the next level of sensitivity improvement in low background measurements. The segmented outer detector contact allows performance of advanced pulse shape analysis measurements that provide additional background reduction. Currently, n-type (reverse electrode) germanium coaxial detectors are used whenever a segmented coaxial detector is needed because the outer boron (electron barrier) contact is thin and can be segmented. Coaxial detectors fabricated from p-type germanium cost less, have better resolution, and are larger than n-type coaxial detectors. However, it is difficult to reliably segment p-type coaxial detectors because thick (~1 mm) lithium-diffused (hole barrier) contacts are the standard outside contact for p-type coaxial detectors. During this Phase 1 Small Business Innovation Research (SBIR) we have researched the possibility of using amorphous germanium contacts as a thin outer contact of p-type coaxial detectors that can be segmented. We have developed amorphous germanium contacts that provide a very high hole barrier on small planar detectors. These easily segmented amorphous germanium contacts have been demonstrated to withstand several thousand volts/cm electric fields with no measurable leakage current (<1 pA) from charge injection over the hole barrier. We have also demonstrated that the contact can be sputter deposited around and over the curved outside surface of a small p-type coaxial detector. The amorphous contact has shown good rectification properties on the outside of a small p-type coaxial detector. These encouraging

  15. Silicone metalization

    DOEpatents

    Maghribi, Mariam N.; Krulevitch, Peter; Hamilton, Julie

    2006-12-05

    A system for providing metal features on silicone comprising providing a silicone layer on a matrix and providing a metal layer on the silicone layer. An electronic apparatus can be produced by the system. The electronic apparatus comprises a silicone body and metal features on the silicone body that provide an electronic device.

  16. Silicone metalization

    DOEpatents

    Maghribi, Mariam N.; Krulevitch, Peter; Hamilton, Julie

    2008-12-09

    A system for providing metal features on silicone comprising providing a silicone layer on a matrix and providing a metal layer on the silicone layer. An electronic apparatus can be produced by the system. The electronic apparatus comprises a silicone body and metal features on the silicone body that provide an electronic device.

  17. p-type Mesoscopic Nickel Oxide/Organometallic Perovskite Heterojunction Solar Cells

    PubMed Central

    Wang, Kuo-Chin; Jeng, Jun-Yuan; Shen, Po-Shen; Chang, Yu-Cheng; Diau, Eric Wei-Guang; Tsai, Cheng-Hung; Chao, Tzu-Yang; Hsu, Hsu-Cheng; Lin, Pei-Ying; Chen, Peter; Guo, Tzung-Fang; Wen, Ten-Chin

    2014-01-01

    In this article, we present a new paradigm for organometallic hybrid perovskite solar cell using NiO inorganic metal oxide nanocrystalline as p-type electrode material and realized the first mesoscopic NiO/perovskite/[6,6]-phenyl C61-butyric acid methyl ester (PC61BM) heterojunction photovoltaic device. The photo-induced transient absorption spectroscopy results verified that the architecture is an effective p-type sensitized junction, which is the first inorganic p-type, metal oxide contact material for perovskite-based solar cell. Power conversion efficiency of 9.51% was achieved under AM 1.5 G illumination, which significantly surpassed the reported conventional p-type dye-sensitized solar cells. The replacement of the organic hole transport materials by a p-type metal oxide has the advantages to provide robust device architecture for further development of all-inorganic perovskite-based thin-film solar cells and tandem photovoltaics. PMID:24755642

  18. Chemical-free n-type and p-type multilayer-graphene transistors

    NASA Astrophysics Data System (ADS)

    Dissanayake, D. M. N. M.; Eisaman, M. D.

    2016-08-01

    A single-step doping method to fabricate n- and p-type multilayer graphene (MG) top-gate field effect transistors (GFETs) is demonstrated. The transistors are fabricated on soda-lime glass substrates, with the n-type doping of MG caused by the sodium in the substrate without the addition of external chemicals. Placing a hydrogen silsesquioxane (HSQ) barrier layer between the MG and the substrate blocks the n-doping, resulting in p-type doping of the MG above regions patterned with HSQ. The HSQ is deposited in a single fabrication step using electron beam lithography, allowing the patterning of arbitrary sub-micron spatial patterns of n- and p-type doping. When a MG channel is deposited partially on the barrier and partially on the glass substrate, a p-type and n-type doping profile is created, which is used for fabricating complementary transistors pairs. Unlike chemically doped GFETs in which the external dopants are typically introduced from the top, these substrate doped GFETs allow for a top gate which gives a stronger electrostatic coupling to the channel, reducing the operating gate bias. Overall, this method enables scalable fabrication of n- and p-type complementary top-gated GFETs with high spatial resolution for graphene microelectronic applications.

  19. PATBox: A Toolbox for Classification and Analysis of P-Type ATPases

    PubMed Central

    Søndergaard, Dan; Pedersen, Christian Nørgaard Storm

    2015-01-01

    P-Type ATPases are part of the regulatory system of the cell where they are responsible for transporting ions and lipids through the cell membrane. These pumps are found in all eukaryotes and their malfunction has been found to cause several severe diseases. Knowing which substrate is pumped by a certain P-Type ATPase is therefore vital. The P-Type ATPases can be divided into 11 subtypes based on their specificity, that is, the substrate that they pump. Determining the subtype experimentally is time-consuming. Thus it is of great interest to be able to accurately predict the subtype based on the amino acid sequence only. We present an approach to P-Type ATPase sequence classification based on the k-nearest neighbors, similar to a homology search, and show that this method provides performs very well and, to the best of our knowledge, better than any existing method despite its simplicity. The classifier is made available as a web service at http://services.birc.au.dk/patbox/ which also provides access to a database of potential P-Type ATPases and their predicted subtypes. PMID:26422234

  20. Piezotronic effect in solution-grown p-type ZnO nanowires and films.

    PubMed

    Pradel, Ken C; Wu, Wenzhuo; Zhou, Yusheng; Wen, Xiaonan; Ding, Yong; Wang, Zhong Lin

    2013-06-12

    Investigating the piezotronic effect in p-type piezoelectric semiconductor is critical for developing a complete piezotronic theory and designing/fabricating novel piezotronic applications with more complex functionality. Using a low temperature solution method, we were able to produce ultralong (up to 60 μm in length) Sb doped p-type ZnO nanowires on both rigid and flexible substrates. For the p-type nanowire field effect transistor, the on/off ratio, threshold voltage, mobility, and carrier concentration of 0.2% Sb-doped sample are found to be 10(5), 2.1 V, 0.82 cm(2)·V(-1)·s(-1), and 2.6 × 10(17) cm(-3), respectively, and the corresponding values for 1% Sb doped samples are 10(4), 2.0 V, 1.24 cm(2)·V(-1)·s(-1), and 3.8 × 10(17) cm(-3). We further investigated the universality of piezotronic effect in the as-synthesized Sb-doped p-type ZnO NWs and reported for the first time strain-gated piezotronic transistors as well as piezopotential-driven mechanical energy harvesting based on solution-grown p-type ZnO NWs. The results presented here broaden the scope of piezotronics and extend the framework for its potential applications in electronics, optoelectronics, smart MEMS/NEMS, and human-machine interfacing. PMID:23635319

  1. Recent Developments in p-Type Oxide Semiconductor Materials and Devices.

    PubMed

    Wang, Zhenwei; Nayak, Pradipta K; Caraveo-Frescas, Jesus A; Alshareef, Husam N

    2016-05-01

    The development of transparent p-type oxide semiconductors with good performance may be a true enabler for a variety of applications where transparency, power efficiency, and greater circuit complexity are needed. Such applications include transparent electronics, displays, sensors, photovoltaics, memristors, and electrochromics. Hence, here, recent developments in materials and devices based on p-type oxide semiconductors are reviewed, including ternary Cu-bearing oxides, binary copper oxides, tin monoxide, spinel oxides, and nickel oxides. The crystal and electronic structures of these materials are discussed, along with approaches to enhance valence-band dispersion to reduce effective mass and increase mobility. Strategies to reduce interfacial defects, off-state current, and material instability are suggested. Furthermore, it is shown that promising progress has been made in the performance of various types of devices based on p-type oxides. Several innovative approaches exist to fabricate transparent complementary metal oxide semiconductor (CMOS) devices, including novel device fabrication schemes and utilization of surface chemistry effects, resulting in good inverter gains. However, despite recent developments, p-type oxides still lag in performance behind their n-type counterparts, which have entered volume production in the display market. Recent successes along with the hurdles that stand in the way of commercial success of p-type oxide semiconductors are presented. PMID:26879813

  2. Growth of p-type GaAs/AlGaAs(111) quantum well infrared photodetector using solid source molecular-beam epitaxy

    SciTech Connect

    Li, H.; Mei, T.; Karunasiri, G.; Fan, W.J.; Zhang, D.H.; Yoon, S.F.; Yuan, K.H.

    2005-09-01

    A p-type GaAs/AlGaAs multi-quantum-well infrared photodetector (QWIP) was fabricated on a GaAs (111)A substrate by molecular-beam epitaxy using silicon as dopant. The same structure was also grown on a GaAs (100) wafer simultaneously to compare the material and structural properties. It was found that Si acts as a p-type dopant in the GaAs (111)A sample while it is n-type in the GaAs (100) counterpart. The growth rate was found to be appreciably enhanced for GaAs (111)A compared with that of GaAs (100) orientation, while the Al composition in the barriers was found to be 20% smaller for a (111) orientation which results in a smaller barrier height. A peak responsivity of 1 mA/W with a relatively wide wavelength response ({delta}{lambda}/{lambda}{sub p}{approx}53%) was observed for the GaAs (111)A QWIP, mainly due to the location of the excited state far above the barrier. The photoresponse also showed a relatively strong normal incident absorption probably originating from the mixing of the conduction and valence Bloch states. The optimization of the quantum well parameters should further enhance the responsivity of this p-type QWIP with Si as dopant species.

  3. Improvement in thermoelectric power factor of mechanically alloyed p-type SiGe by incorporation of TiB2

    NASA Astrophysics Data System (ADS)

    Ahmad, Sajid; Dubey, K.; Bhattacharya, Shovit; Basu, Ranita; Bhatt, Ranu; Bohra, A. K.; Singh, Ajay; Aswal, D. K.; Gupta, S. K.

    2016-05-01

    Nearly 60% of the world's useful energy is wasted as heat and recovering a fraction of this waste heat by converting it as useful electrical power is an important area of research[1]. Thermoelectric power generators (TEG) are solid state devices which converts heat into electricity. TEG consists of n and p-type thermoelements connected electrically in series and thermally in parallel[2]. Silicon germanium (SiGe) alloy is one of the conventional high temperature thermoelectric materials and is being used in radio-isotopes based thermoelectric power generators for deep space exploration programs.Temperature (T) dependence of thermoelectric (TE) properties of p-type SiGe and p-type SiGe-x wt.%TiB2 (x=6,8,10%) nanocomposite materials has been studied with in the temperature range of 300 K to 1100 K. It is observed that there is an improvement in the power factor (α2/ρ) of SiGe alloy on addition of TiB2 upto 8 wt.% that is mainly due to increase in the Seebeck coefficient (α) and electrical conductivity (σ) of the alloy.

  4. Fabrication and Characterization of Rapidly Oxidized p-Type Cu2O Films from Cu Films and their Application to Heterojunction Thin-Film Solar Cells

    NASA Astrophysics Data System (ADS)

    Kim, Hyung Soo; Lim, Jung Wook; Yun, Sun Jin; Park, Min A.; Park, Se Yong; Lee, Seong Eui; Lee, Hee Chul

    2013-10-01

    In this study, we report that the metal Cu deposited on a glass substrate is formed into a stable p-type Cu2O film with excellent properties through rapid thermal oxidation (RTO). The pre-deposited Cu film layer went through thermal oxidation in the temperature range of 200-500 °C in O2 and air ambient, and the electrical and optical properties were intensively investigated. The optimized p-type Cu2O film heat-treated at a temperature of 200 °C in an air ambient has a carrier concentration of 1.25×1017 cm-3, mobility of 0.51 cm2 V-1 s-1, and resistivity of 9.86 Ω cm; its optical band gap reaches about 2.4 eV. Using the p-type Cu2O film with i- and n-type amorphous silicon layers, heterojunction thin-film solar cells were fabricated on glass substrates. These transparent solar cells employed Ga-doped ZnO films as top and bottom electrodes. Solar cells with Cu2O film oxidized at 200 °C in an air ambient have an open circuit voltage of 0.36 V, short-circuit current of 15.2 mA/cm2, and photoelectric conversion efficiency of 1.98%.

  5. Modeling of the Thermoelectric Properties of p-Type IrSb(sub 3)

    NASA Technical Reports Server (NTRS)

    Fleurial, J.

    1994-01-01

    IrSb(sub 3) is a compound of the skutterudite family of materials now being investigated at JPL. A combination of experimental and theoretical approaches has been recently applied at JPL to evaluate the potential of several thermoelectric materials such as n-type and p-type Si(sub 80) Ge(sub 20) alloys, n-type and p-type Bi(sub 2) Te(sub 3)-based alloys and p-type Ru(sub 2) Ge(sub 3) compound. The use of a comprehensive model for the thermal and electrical transport properties of a given material over its full temperature range of usefulness is a powerful tool for guiding experimental optimization of the composition, temperature and doping level as well as for predicting the maximum ZT value likely to be achieved.

  6. Identification and design principles of low hole effective mass p-type transparent conducting oxides

    PubMed Central

    Hautier, Geoffroy; Miglio, Anna; Ceder, Gerbrand; Rignanese, Gian-Marco; Gonze, Xavier

    2013-01-01

    The development of high-performance transparent conducting oxides is critical to many technologies from transparent electronics to solar cells. Whereas n-type transparent conducting oxides are present in many devices, their p-type counterparts are not largely commercialized, as they exhibit much lower carrier mobilities due to the large hole effective masses of most oxides. Here we conduct a high-throughput computational search on thousands of binary and ternary oxides and identify several highly promising compounds displaying exceptionally low hole effective masses (up to an order of magnitude lower than state-of-the-art p-type transparent conducting oxides), as well as wide band gaps. In addition to the discovery of specific compounds, the chemical rationalization of our findings opens new directions, beyond current Cu-based chemistries, for the design and development of future p-type transparent conducting oxides. PMID:23939205

  7. Dopant source choice for formation of p-type ZnO: Li acceptor

    NASA Astrophysics Data System (ADS)

    Zeng, Y. J.; Ye, Z. Z.; Xu, W. Z.; Li, D. Y.; Lu, J. G.; Zhu, L. P.; Zhao, B. H.

    2006-02-01

    Li-doped, p-type ZnO thin films have been realized via dc reactive magnetron sputtering. An optimized result with a resistivity of 16.4Ωcm, Hall mobility of 2.65cm2/Vs, and hole concentration of 1.44×1017cm-3 was achieved, and electrically stable over a month. Hall-effect measurements supported by secondary ion mass spectroscopy indicated that the substrate temperature played a key role in optimizing the p-type conduction of Li-doped ZnO thin films. Furthermore, ZnO-based p-n homojunction was fabricated by deposition of a Li-doped p-type ZnO layer on an Al-doped n-type ZnO layer.

  8. Realization of p-type ZnO films via monodoping of Li acceptor

    NASA Astrophysics Data System (ADS)

    Zeng, Yu-Jia; Ye, Zhi-Zhen; Xu, Wei-Zhong; Chen, Lan-Lan; Li, Dan-Ying; Zhu, Li-Ping; Zhao, Bing-Hui; Hu, Ying-Lin

    2005-09-01

    p-Type ZnO thin films have been realized via monodoping of Li acceptor by adopting DC reactive magnetron sputtering. The lowest room-temperature resistivity was found to be 17.6 Ω cm with a Hall mobility of 3.47 cm2 V-1 s-1 and carrier concentration of 1.01×1017 cm-3 for Li-doped p-type ZnO film deposited on glass substrate. The Li-doped ZnO film possessed a good crystallinity with c-axis orientation and a high transmittance (90%) in the visible region. Moreover, the effects of Li content on the crystallinity, electrical and optical properties of p-type ZnO films were discussed.

  9. High performance P-type thermoelectric materials and methods of preparation

    NASA Technical Reports Server (NTRS)

    Caillat, Thierry (Inventor); Borshchevsky, Alexander (Inventor); Fleurial, Jean-Pierre (Inventor)

    2002-01-01

    The present invention is embodied in high performance p-type thermoelectric materials having enhanced thermoelectric properties and the methods of preparing such materials. In one aspect of the invention, p-type semiconductors of formula Zn.sub.4-x A.sub.x Sb.sub.3-y B.sub.y wherein 0.ltoreq.x.ltoreq.4, A is a transition metal, B is a pnicogen, and 0.ltoreq.y.ltoreq.3 are formed for use in manufacturing thermoelectric devices with substantially enhanced operating characteristics and improved efficiency. Two methods of preparing p-type Zn.sub.4 Sb.sub.3 and related alloys of the present invention include a crystal growth method and a powder metallurgy method.

  10. Electrical and optical properties of p-type InN

    SciTech Connect

    Mayer, Marie A.; Choi, Soojeong; Bierwagen, Oliver; Smith, Holland M.; Haller, Eugene E.; Speck, James S.; Walukiewicz, Wladek

    2011-01-01

    We have performed comprehensive studies of optical, thermoelectric and electrical properties of Mg doped InN with varying Mg doping levels and sample thicknesses. Room temperature photoluminescence spectra show a Mg acceptor related emission and the thermopower provides clear evidence for the presence of mobile holes. Although the effects of the hole transport are clearly observed in the temperature dependent electrical properties, the sign of the apparent Hall coefficient remains negative in all samples. We show that the standard model of two electrically well connected layers (n-type surface electron accumulation and p-type bulk) does not properly describe Hall effect in p-type InN.

  11. Tunable electronic structures of p-type Mg doping in AlN nanosheet

    SciTech Connect

    Peng, Yuting; Xia, Congxin Zhang, Heng; Wang, Tianxing; Wei, Shuyi; Jia, Yu

    2014-07-28

    The p-type impurity properties are investigated in the Mg-doped AlN nanosheet by means of first-principles calculations. Numerical results show that the transition energy levels reduce monotonously with the increase in Mg doping concentration in the Mg-doped AlN nanosheet systems, and are lower than that of the Mg-doped bulk AlN case for the cases with larger doping concentration. Moreover, Mg substituting Al atom is energy favorably under N-rich growth experimental conditions. These results are new and interesting to further improve p-type doping efficiency in the AlN nanostructures.

  12. Spectral sensitivity of graphene/silicon heterojunction photodetectors

    NASA Astrophysics Data System (ADS)

    Riazimehr, Sarah; Bablich, Andreas; Schneider, Daniel; Kataria, Satender; Passi, Vikram; Yim, Chanyoung; Duesberg, Georg S.; Lemme, Max C.

    2016-01-01

    We have studied the optical properties of two-dimensional (2D) Schottky photodiode heterojunctions made of chemical vapor deposited (CVD) graphene on n- and p-type silicon (Si) substrates. Much better rectification behavior is observed from the diodes fabricated on n-Si substrates in comparison with the devices on p-Si substrates in dark condition. Also, graphene - n-Si photodiodes show a considerable responsivity of 270 mA W-1 within the silicon spectral range in DC reverse bias condition. The present results are furthermore compared with that of a molybdenum disulfide (MoS2) - p-type silicon photodiode.

  13. Silicon radiation detectors with oxide charge state compensation

    NASA Technical Reports Server (NTRS)

    Walton, J. T.; Goulding, F. S.

    1987-01-01

    This paper discusses the use of boron implantation on high resistivity P type silicon before oxide growth to compensate for the presence of charge states in the oxide and oxide/silicon interface. The presence of these charge states on high resistivity P type silicon produces an inversion layer which causes high leakage currents on N(+)P junctions and high surface conductance. Compensating the surface region by boron implantation is shown to result in oxide passivated N(+)P junctions with very low leakage currents and with low surface conductance.

  14. P-type doping of hydrogenated amorphous silicon films with boron by reactive radio-frequency co-sputtering

    NASA Astrophysics Data System (ADS)

    Ohmura, Y.; Takahashi, M.; Suzuki, M.; Sakamoto, N.; Meguro, T.

    2001-12-01

    B has been successfully doped into the hydrogenated amorphous Si films without using explosive and/or toxic gases SiH 4 or B 2H 6 by reactive radio-frequency co-sputtering. The target used for co-sputtering was a composite target composed of a B-doped Si wafer and B chips attached on the Si wafer with silver powder bond. The maximum area fraction of B chips used was 0.11. Argon and hydrogen pressures were 5×10 -3 and 5×10 -4 Torr, respectively. Substrates were kept at 200°C or 250°C during sputtering. The maximum B concentration in the film obtained was 2×10 19 cm -3 from secondary ion mass spectroscopy measurement. Films with resistivity of 10 4-10 5 Ω cm were obtained, which was low for the above acceptor concentration, compared with other group III impurities doping, indicating the high doping efficiency of B. A heterostructure, which was prepared by co-sputtering these B-doped films on an n-type crystalline Si, shows a good rectification characteristic. A small photovoltaic effect is also observed.

  15. Synthesis and characterization of a photosensitive interface for hydrogen generation: Chemically modified p-type semiconducting silicon photocathodes

    PubMed Central

    Bookbinder, Dana C.; Bruce, James A.; Dominey, Raymond N.; Lewis, Nathan S.; Wrighton, Mark S.

    1980-01-01

    p-Si photocathodes functionalized first with an N,N′-dialkyl-4,4′-bipyridinium redox reagent, (PQ2+/+-)surf, and then with a Pt precursor, PtCl62-, give significant efficiency (up to 5%) for photoelectrochemical H2 generation with 632.8-nm light. Naked p-Si photocathodes give nearly zero efficiency, owing to poor H2 evolution kinetics that are improved by the (PQ2+/+-)surf/Pt modification. The mechanism of H2 evolution from p-Si/(PQ2+/+-)surf/Pt is first photoexcitation of electrons to the conduction band of Si followed by (PQ2+)surf → (PQ+-)surf reduction. The dispersion of Pt then catalyzes H2O reduction to give H2 and regeneration of (PQ2+)surf. The overall energy conversion efficiency rivals the best direct optical to chemical conversion systems reported to date. PMID:16592907

  16. Synthesis and characterization of a photosensitive interface for hydrogen generation: chemically modified p-type semiconducting silicon photocathodes

    SciTech Connect

    Bookbinder, D.C.; Bruce, J.A.; Dominey, R.N.; Lewis, N.S.; Wrighton, M.S.

    1980-11-01

    p-Si photocathodes functionalized first with an N,N'-dialkyl-4,4'-bipyridinium redox reagent, (PQ/sup 2+/+./)/sub surf/, and then with a Pt precursor, PtCl/sub 6//sup 2 -/, give significant efficiency (up to 5%) for photoelectrochemical H/sub 2/ generation with 632.8-nm light. Naked p-Si photocathodes give nearly zero efficiency, owing to poor H/sub 2/ evolution kinetics that are improved by the (PQ/sup 2+/+.//sub surf)/Pt modification. The mechanism of H/sub 2/ evolution from p-Si/(PQ/sup 2+/+./)/sub surf/Pt is first photoexcitation of electrons to the conduction band of Si followed by (PQ/sup 2 +/)/sub surf/ ..-->.. (PQ/sup +.//sub surf/ reduction. The dispersion of Pt then catalyzes H/sub 2/O reduction to give H/sub 2/ and regeneration of (PQ/sup 2/)/sub surf/. The overall energy conversion efficiency rivals the best direct optical to chemical conversion systems reported to date.

  17. A structural and functional perspective of DyP-type peroxidase family.

    PubMed

    Yoshida, Toru; Sugano, Yasushi

    2015-05-15

    Dye-decolorizing peroxidase from the basidiomycete Bjerkandera adusta Dec 1 (DyP) is a heme peroxidase. This name reflects its ability to degrade several anthraquinone dyes. The substrate specificity, the amino acid sequence, and the tertiary structure of DyP are different from those of the other heme peroxidase (super)families. Therefore, many proteins showing the similar amino acid sequences to that of DyP are called DyP-type peroxidase which is a new family of heme peroxidase identified in 2007. In fact, all structures of this family show a similar structure fold. However, this family includes many proteins whose amino acid sequence identity to DyP is lower than 15% and/or whose catalytic efficiency (kcat/Km) is a few orders of magnitude less than that of DyP. A protein showing an activity different from peroxidase activity (dechelatase activity) has been also reported. In addition, the precise physiological roles of DyP-type peroxidases are unknown. These facts raise a question of whether calling this family DyP-type peroxidase is suitable. Here, we review the differences and similarities of structure and function among this family and propose the reasonable new classification of DyP-type peroxidase family, that is, class P, I and V. In this contribution, we discuss the adequacy of this family name. PMID:25655348

  18. Diffusion, Uptake and Release of Hydrogen in p-type Gallium Nitride: Theory and Experiment

    SciTech Connect

    MYERS JR.,SAMUEL M.; WRIGHT,ALAN F.; PETERSEN,GARY A.; WAMPLER,WILLIAM R.; SEAGER,CARLETON H.; CRAWFORD,MARY H.; HAN,JUNG

    2000-06-27

    The diffusion, uptake, and release of H in p-type GaN are modeled employing state energies from density-function theory and compared with measurements of deuterium uptake and release using nuclear-reaction analysis. Good semiquantitative agreement is found when account is taken of a surface permeation barrier.

  19. p -type Bi2Se3 for topological insulator and low-temperature thermoelectric applications

    NASA Astrophysics Data System (ADS)

    Hor, Y. S.; Richardella, A.; Roushan, P.; Xia, Y.; Checkelsky, J. G.; Yazdani, A.; Hasan, M. Z.; Ong, N. P.; Cava, R. J.

    2009-05-01

    The growth and elementary properties of p -type Bi2Se3 single crystals are reported. Based on a hypothesis about the defect chemistry of Bi2Se3 , the p -type behavior has been induced through low-level substitutions (1% or less) of Ca for Bi. Scanning tunneling microscopy is employed to image the defects and establish their charge. Tunneling and angle-resolved photoemission spectra show that the Fermi level has been lowered into the valence band by about 400 meV in Bi1.98Ca0.02Se3 relative to the n -type material. p -type single crystals with ab -plane Seebeck coefficients of +180μV/K at room temperature are reported. These crystals show an anomalous peak in the Seebeck coefficient at low temperatures, reaching +120μVK-1 at 7 K, giving them a high thermoelectric power factor at low temperatures. In addition to its interesting thermoelectric properties, p -type Bi2Se3 is of substantial interest for studies of technologies and phenomena proposed for topological insulators.

  20. Pure silver ohmic contacts to N- and P- type gallium arsenide materials

    DOEpatents

    Hogan, Stephen J.

    1986-01-01

    Disclosed is an improved process for manufacturing gallium arsenide semiconductor devices having as its components an n-type gallium arsenide substrate layer and a p-type gallium arsenide diffused layer. The improved process comprises forming a pure silver ohmic contact to both the diffused layer and the substrate layer, wherein the n-type layer comprises a substantially low doping carrier concentration.

  1. Process for forming pure silver ohmic contacts to N- and P-type gallium arsenide materials

    DOEpatents

    Hogan, S.J.

    1983-03-13

    Disclosed is an improved process for manufacturing gallium arsenide semiconductor devices having as its components a n-type gallium arsenide substrate layer and a p-type gallium arsenide diffused layer. The improved process comprises forming a pure silver ohmic contact to both the diffuse layer and the substrate layer wherein the n-type layer comprises a substantially low doping carrier concentration.

  2. Origin and evolution of metal P-type ATPases in Plantae (Archaeplastida)

    PubMed Central

    Hanikenne, Marc; Baurain, Denis

    2013-01-01

    Metal ATPases are a subfamily of P-type ATPases involved in the transport of metal cations across biological membranes. They all share an architecture featuring eight transmembrane domains in pairs of two and are found in prokaryotes as well as in a variety of Eukaryotes. In Arabidopsis thaliana, eight metal P-type ATPases have been described, four being specific to copper transport and four displaying a broader metal specificity, including zinc, cadmium, and possibly copper and calcium. So far, few efforts have been devoted to elucidating the origin and evolution of these proteins in Eukaryotes. In this work, we use large-scale phylogenetics to show that metal P-type ATPases form a homogenous group among P-type ATPases and that their specialization into either monovalent (Cu) or divalent (Zn, Cd…) metal transport stems from a gene duplication that took place early in the evolution of Life. Then, we demonstrate that the four subgroups of plant metal ATPases all have a different evolutionary origin and a specific taxonomic distribution, only one tracing back to the cyanobacterial progenitor of the chloroplast. Finally, we examine the subsequent evolution of these proteins in green plants and conclude that the genes thoroughly characterized in model organisms are often the result of lineage-specific gene duplications, which calls for caution when attempting to infer function from sequence similarity alone in non-model organisms. PMID:24575101

  3. Amorphous silicon/polycrystalline thin film solar cells

    SciTech Connect

    Ullal, H.S.

    1991-03-13

    An improved photovoltaic solar cell is described including a p-type amorphous silicon layer, intrinsic amorphous silicon, and an n-type polycrystalline semiconductor such as cadmium sulfide, cadmium zinc sulfide, zinc selenide, gallium phosphide, and gallium nitride. The polycrystalline semiconductor has an energy bandgap greater than that of the amorphous silicon. The solar cell can be provided as a single-junction device or a multijunction device.

  4. Theoretical study of hole initiated impact ionization in bulk silicon and GaAs using a wave-vector-dependent numerical transition rate formulation within an ensemble Monte Carlo calculation

    NASA Technical Reports Server (NTRS)

    Oguzman, Ismail H.; Wang, Yang; Kolnik, Jan; Brennan, Kevin F.

    1995-01-01

    In this paper, calculations of the hole initiated interband impact ionization rate in bulk silicon and GaAs are presented based on an ensemble Monte Carlo simulation with the inclusion of a wave-vector-dependent numerical transition rate formulation. The ionization transition rate is determined for each of the three valence bands, heavy, light, and split-off, using Fermi's golden rule with a two-body, screened Coulomb interaction. The dielectric function used within the calculation is assumed to be wave-vector-dependent. Calculations of the field-dependent impact ionization rate as well as the quantum yield are presented. It is found from both the quantum yield results and examination of the hole distribution function that the effective threshold energy for hole initiated impact ionization is relatively soft, similar to that predicted for the corresponding electron initiated ionization events occur more frequently than either heavy or split-offf initiated ionization events in bulk silicon over the applied electric field strengths examined here, 250-500 kV/cm. Conversely,in GaAs, the vast majority of hole initated ionization events originate from holes within the split-off band.

  5. The p-type conduction mechanism in Cu2O: a first principles study.

    PubMed

    Nolan, Michael; Elliott, Simon D

    2006-12-01

    Materials based on Cu2O are potential p-type transparent semiconducting oxides. Developing an understanding of the mechanism leading to p-type behaviour is important. An accepted origin is the formation of Cu vacancies. However, the way in which this mechanism leads to p-type properties needs to be investigated. This paper presents a first principles analysis of the origin of p-type semiconducting behaviour in Cu2O with 1.5 and 3% Cu vacancy concentrations. Plane wave density functional theory (DFT) with the Perdew-Burke Ernzerhof (PBE) exchange-correlation functional is applied. In order to investigate the applicability of DFT, we firstly show that CuO, with 50% Cu vacancies cannot be described with DFT and in order to obtain a consistent description of CuO, the DFT + U approach is applied. The resulting electronic structure is consistent with experiment, with a spin moment of 0.64 mu(B) and an indirect band gap of 1.48 eV for U = 7 eV. However, for a 3% Cu vacancy concentration in Cu2O, the DFT and DFT + U descriptions of Cu vacancies are similar, indicating that DFT is suitable for a small concentration of Cu vacancies; the formation energy of a Cu vacancy is no larger than 1.7 eV. Formation of Cu vacancies produces delocalised hole states with hole effective masses consistent with the semiconducting nature of Cu2O. These results demonstrate that the p-type semiconducting properties observed for Cu2O are explained by a small concentration of Cu vacancies. PMID:19810413

  6. Ternary chalcogenides Cs2Zn3Se4 and Cs2Zn3Te4 : Potential p -type transparent conducting materials

    DOE PAGESBeta

    Shi, Hongliang; Saparov, Bayrammurad; Singh, David J.; Sefat, Athena S.; Du, Mao-Hua

    2014-11-11

    Here we report prediction of two new ternary chalcogenides that can potentially be used as p-type transparent conductors along with experimental synthesis and initial characterization of these previously unknown compounds, Cs2Zn3Ch4 (Ch = Se, Te). In particular, the structures are predicted based on density functional calculations and confirmed by experiments. Phase diagrams, electronic structure, optical properties, and defect properties of Cs2Zn3Se4 and Cs2Zn3Te4 are calculated to assess the viability of these materials as p-type TCMs. Cs2Zn3Se4 and Cs2Zn3Te4, which are stable under ambient air, display large optical band gaps (calculated to be 3.61 and 2.83 eV, respectively) and have smallmore » hole effective masses (0.5-0.77 me) that compare favorably with other proposed p-type TCMs. Defect calculations show that undoped Cs2Zn3Se4 and Cs2Zn3Te4 are p-type materials. However, the free hole concentration may be limited by low-energy native donor defects, e.g., Zn interstitials. Lastly, non-equilibrium growth techniques should be useful for suppressing the formation of native donor defects, thereby increasing the hole concentration.« less

  7. [Biological function of some elements and their compounds. IV. Silicon, silicon acids, silicones].

    PubMed

    Puzanowska-Tarasiewicz, Helena; Kuźmicka, Ludmiła; Tarasiewicz, Mirosław

    2009-11-01

    The review is devoted for the occurance, meaning of silicon and their compounds, especially silicon acids and silicones. Silicon participates in biosynthesis of collagen, the basic component of connective tissue. It strengthens and makes the walls of blood vessels more flexible, diminishes capillaries permeability, accelerates healing processes, has a sebostatic activity, strengthens hair and nails. This element has a beneficial effect on phosphorylation of proteins saccharides, and nucleotides. It is also essential for the formation of cytoskeleton and other cellular structures of mechanical or supportive function. Silicon is an initial substrate for obtaining silicones. These are synthetic polymers, in which silicon atoms are bound by oxygen bridges. They are used in almost all kinds of products due to their most convenient physical and chemical properties: moistening and film-forming, giving liquid form increasing solubility. Silicon acids form colloid gel, silica gel, with absorptive abilities, like active carbon. PMID:19999810

  8. Enhancing the far-ultraviolet sensitivity of silicon complementary metal oxide semiconductor imaging arrays

    NASA Astrophysics Data System (ADS)

    Retherford, Kurt D.; Bai, Yibin; Ryu, Kevin K.; Gregory, James A.; Welander, Paul B.; Davis, Michael W.; Greathouse, Thomas K.; Winters, Gregory S.; Suntharalingam, Vyshnavi; Beletic, James W.

    2015-10-01

    We report our progress toward optimizing backside-illuminated silicon P-type intrinsic N-type complementary metal oxide semiconductor devices developed by Teledyne Imaging Sensors (TIS) for far-ultraviolet (UV) planetary science applications. This project was motivated by initial measurements at Southwest Research Institute of the far-UV responsivity of backside-illuminated silicon PIN photodiode test structures, which revealed a promising QE in the 100 to 200 nm range. Our effort to advance the capabilities of thinned silicon wafers capitalizes on recent innovations in molecular beam epitaxy (MBE) doping processes. Key achievements to date include the following: (1) representative silicon test wafers were fabricated by TIS, and set up for MBE processing at MIT Lincoln Laboratory; (2) preliminary far-UV detector QE simulation runs were completed to aid MBE layer design; (3) detector fabrication was completed through the pre-MBE step; and (4) initial testing of the MBE doping process was performed on monitoring wafers, with detailed quality assessments.

  9. Silicon production process evaluations

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Engineering design of the third distillation column in the process was accomplished. The initial design is based on a 94.35% recovery of dichlorosilane in the distillate and a 99.9% recovery of trichlorosilane in the bottoms. The specified separation is achieved at a reflux ratio of 15 with 20 trays (equilibrium stages). Additional specifications and results are reported including equipment size, temperatures and pressure. Specific raw material requirements necessary to produce the silicon in the process are presented. The primary raw materials include metallurgical grade silicon, silicon tetrachloride, hydrogen, copper (catalyst) and lime (waste treatment). Hydrogen chloride is produced as by product in the silicon deposition. Cost analysis of the process was initiated during this reporting period.

  10. Indentation plasticity and fracture in silicon

    NASA Technical Reports Server (NTRS)

    Rybicki, George C.; Pirouz, P.

    1988-01-01

    Measurements of the ductile-brittle transition temperature of heavily doped silicon were carried out using indentation techniques. Diamond pyramid hardness tests were performed on the (100) face of heavily doped N-type and P-type and intrinsic silicon single crystals. Tests were performed over the range 200 C to 850 C and loads of 100 to 500 g were used. Samples were subsequently etched to reveal dislocation rosettes produced by indentation. Intrinsic silicon underwent a ductile-brittle transition at 660 C, P-type at 645 C and N-type at 625 C. Hardness values varied from 1.1 GPa at 700 C to 11.7 GPa at 200 C. Significant effects of hardness on doping were present only at the highest temperatures. Lower loads generally produced higher hardness but load did not affect the Ductile-Brittle Transition Temperature (DBTT). Fracture toughness values ranged from 0.9 MPa m(1/2) at 200 C to 2.75 MPa m(1/2) near the DBTT. Doping did not affect the fracture toughness of silicon. P-type doping increased the size of dislocation rosettes observed after indentation, but N-type did not, in contradiction of the expected results. Results are discussed in terms of the effect of doping on the dislocation mobility in silicon.