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1.
《Solid State Ionics》2006,177(33-34):2903-2909
Deposition of yttria-stabilized zirconia films on surface oxidized Ni wire substrate by chemical vapor infiltration (CVI) using ZrCl4 and YCl3 as metal sources and NiO as oxygen source were studied. The resultant films were cubic crystals of YSZ with a Y2O3 content of 1.0–3.7 mol%. The growth rate is larger than that obtained by conventional method of chemical vapor deposition (CVD), increased with the flow rate and decreased with diameter of NiO fiber. The growth rate above its thickness of 4 μm decreased with an increase in the oxidation temperature since the porosity of NiO wire might decrease with an increase in the oxidation temperature. Growth of YSZ films with the CVI method simultaneously involved CVD and electrochemical vapor deposition (EVD). 相似文献
2.
Hydrogenated nanocrystalline silicon (nc-Si:H) thin films were fabricated by plasma enhanced chemical vapor deposition under the various negative substrate bias voltages with hydrogen as a diluent of silane. The microstructure and optical properties of nc-Si:H thin films were studied by Raman scattering spectroscopy, X-ray diffraction (XRD), transmission electron microscopy, and optical transmission spectroscopy. Raman spectra and XRD pattern reveal that applying negative bias voltages at the moderate level favors the enhancement of crystalline volume fraction, increase of crystallite sizes and decrease of residual stress. We also demonstrated that the negative direct current bias can be used to modulate the volume fraction of voids, refractive index, absorption coefficient, compactness and ordered degree of nc-Si:H films. It is found that the film deposited at −80 V shows not only high crystallinity, size of crystallite, and static index n0 but also low residual stress and volume fraction of voids. Furthermore, the microstructural evolution mechanism of nc-Si:H thin films prepared at different bias voltages is tentatively explored. 相似文献
3.
The hydrogenated nanocrystalline silicon (nc-Si:H) thin films were produced by capacitively-coupled plasma enhanced chemical vapor deposition (PECVD) technique at low substrate temperatures (Ts ≈ 40–200 °C). Firstly, for particular growth parameters, the lowest stable Ts was determined to avoid temperature fluctuations during the film deposition. The influence of the Ts on the structural and optical properties of the films was investigated by the Fourier transform infrared (FTIR), UV–visible transmittance/reflectance and X-ray diffraction (XRD) spectroscopies. Also, the films deposited at the center of the PECVD electrode and those around the edge of the PECVD electrode were compared within each deposition cycle. The XRD and UV–visible reflectance analyses reveal the nanocrystalline phase for the films grown at the edge at all Ts and for the center films only at 200 °C. The crystallinity fraction and lateral dark conductivity decrease with lowered Ts. FTIR analyses were used to track the hydrogen content, void fraction and amorphous matrix volume fraction within the films. The optical constants obtained from the UV–visible transmittance spectroscopy were correlated well with the FTIR results. Finally, the optimal Ts was concluded for the application of the produced nc-Si:H in silicon-based thin film devices on plastic substrates. 相似文献
4.
5.
Transition-metal-based nitrides and carbides have been widely studied for various applications because of their excellent mechanical, electrical, and catalytic properties. Although outstanding performances of Mo nitride and carbonitride synthesized by chemical reaction methods have been reported recently for catalytic applications, a metallic phase transition method for pre-deposited MoO3 precursor films, which is suitable for application to Si or metallic substrates, has rarely been reported. Herein, we investigate Mo nitride and carbonitride thin films synthesized via nitriding and carbonitriding of MoO3 films using two types of ammonium salt precursors, urea and ammonium carbonate (AC), in the chemical vapor deposition (CVD) process. The phase-changed crystalline films of Mo carbonitride via the urea reaction and Mo nitride via the AC reaction were determined to be MoC0.5N0.5 and MoN by X-ray diffractometry, respectively. Nevertheless, amorphous states of carbons and their related compounds, unreacted residual MoO3, and incompletely reacted MoO2 remained in the films, as determined by other thin film analyses. When the residual MoO2 was minimal, the films exhibited the lowest electrical resistivity, i.e., ∼10−4 Ω·cm for Mo carbonitride and ∼10−3 Ω·cm for Mo nitride, implying an optimum metallic phase transition. Our results pave the way for the nitriding and carbonitriding of transition metal oxides using ammonium salt precursors for a one-step reaction in the CVD process. 相似文献
6.
The nanostructural and chemical features of nanocrystalline Si (nc-Si) films, which were prepared by plasma-enhanced chemical vapor deposition (PECVD), were investigated in terms of various deposition conditions such as reaction gas fractions and substrate temperature. Such features were related with the photoluminescence (PL) phenomena of the nc-Si films. The phase of the nc-Si films prepared at room temperature is somewhere between amorphous and crystalline states, containing about 2 nm size nanocrystallites, which are well passivated by hydrogen. These films exhibit significant PL intensities near blue light region; the PL peaks shift to lower wavelength with decreasing nanocrystallite size. 相似文献
7.
在等离子体增强化学气相沉积系统中利用大氢稀释逐层淀积技术制备nc-Si量子点阵列,用硅烷和氨气混合气体淀积氮化硅层,制备了a-SiNx/nc-Si/a-SiNx不对称双势垒结构,其中隧穿和控制a-SiNx层的厚度分别为3和20 nm.利用电导-电压和电容-电压测量研究结构中的载流子隧穿和存储特性.在同一样品中观测到由于电荷隧穿引起的电导峰和由于电荷存储引起的电容回滞现象.研究结果表明,合理地选择隧穿层和控制栅层的厚度,就能够实现载流子发生共振隧穿进入到nc-Si量子点中,并被保存在nc-Si量子点中.
关键词:
nc-Si量子点
电导峰
存储效应 相似文献
8.
H.T. Feng R.F. Zhuo J.T. Chen D. Yan J.J. Feng H.J. Li S. Cheng P.X. Yan 《Physica E: Low-dimensional Systems and Nanostructures》2009,41(9):1640-1644
We report the synthesis and characterization Sb-doped SnO2 nanowires by chemical vapor deposition (CVD) at 850 °C. The as-synthesized-doped nanowires showed unique periodical structures in contrast to the traditional nanowires with smooth surfaces. The fascinating structures lead to a much higher surface to volume ratio and greater changes of depletion layer volume after gas absorption, and the sensitivity of gas sensing devices may be improved by using axial periodical nanostructures, instead of ordinary one. The photoluminescence of the Sb-doped SnO2 nanostructures were measured. The doping of Sb atoms brings two new emission peaks at 561 and 670 nm. 相似文献
9.
M. Modreanu M. Gartner E. Aperathitis N. Tomozeiu M. Androulidaki D. Cristea Paul Hurley 《Physica E: Low-dimensional Systems and Nanostructures》2003,16(3-4):461
Structures containing silicon nanocrystals (nc-Si) are very promising for Si-based light-emitting devices. Using a technology compatible with that of silicon, a broader wavelength range of the emitted photoluminescence (PL) was obtained with nc-Si/SiO2 multilayer structures. The main characteristic of these structures is that both layers are light emitters. In this study we report results on a series of nc-Si/SiO2 multilayer periods deposited on 200 nm thermal oxide SiO2/Si substrate. Each period contains around 10 nm silicon thin films obtained by low-pressure chemical vapour deposition at T=625°C and 100 nmSiO2 obtained by atmospheric pressure chemical vapour deposition T=400°C. Optical and microstructural properties of the multilayer structures have been studied by spectroscopic ellipsometry (using the Bruggemann effective medium approximation model for multilayer and multicomponent films), FTIR and UV–visible reflectance spectroscopy. IR spectroscopy revealed the presence of SiOx structural entities in each nc-Si/SiO2 interface. Investigation of the PL spectra (using continuous wave-CW 325 nm and pulsed 266 nm laser excitation) has shown several peaks at 1.7, 2, 2.3, 2.7, 3.2 and 3.7 eV, associated with the PL centres in SiO2, nc-Si and Si–SiO2 interface. Their contribution to the PL spectra depends on the number of layers in the stack. 相似文献
10.
N.A. Bakr V.S. Waman R.R. Hawaldar V.G. Sathe S.R. Jadkar 《Journal of Physics and Chemistry of Solids》2011,72(6):685-691
Hydrogenated nanocrystalline silicon (nc-Si:H) thin films were deposited using HW-CVD technique at various deposition pressures. Characterisation of these films from Raman spectroscopy revealed that nc-Si:H thin films consist of a mixture of two phases, crystalline phase and amorphous phase containing small Si crystals embedded therein. We observed increase in crystallinity in the films with increase in deposition pressure whereas the size of Si nanocrystals was found ∼2 nm over the entire range of deposition pressure studied. The FTIR spectroscopic analysis showed that with increasing deposition pressure the predominant hydrogen bonding in the films shifts from, Si-H to Si-H2 and (Si-H2)n complexes and the hydrogen content in the films was found in the range 6.2-9.3 at% over the entire range of deposition pressure studied. The photo and dark conductivities results also indicate that the films deposited with increasing deposition pressure get structurally modified. It has been found that the optical energy gap range was between 1.72 and 2.1 eV with static refractive index between 2.85 and 3.24. From the present study it has been concluded that the deposition pressure is a key process parameter to induce the crystallinity in the Si:H thin films using HW-CVD. 相似文献
11.
Hydrogenated nanocrystalline silicon germanium thin films (nc-SiGe:H) is an interesting alternative material to replace hydrogenated
nanocrystalline silicon (nc-Si:H) as the narrow bandgap absorber in an a-Si/a-SiGe/nc-SiGe(nc-Si) triple-junction solar cell
due to its higher optical absorption in the wavelength range of interest. In this paper, we present results of optical, structural
investigations and electrical characterization of nc-SiGe:H thin films made by hot-wire chemical vapor deposition (HW-CVD)
with a coil-shaped tungsten filament and with a disilane/germane/hydrogen gas mixture. The optical band gaps of a-SiGe:H and
nc-SiGe:H thin-films, which are deposited with the same disilane/germane/hydrogen gas mixture ratio of 3.4 : 1.7 : 7, are
about 1.58 eV and 2.1 eV, respectively. The nc-SiGe:H thin film exhibits a larger optical absorption coefficient of about
2–4 in the 600–900 nm range when compared to nc-Si:H thin film. Therefore, a thinner nc-SiGe:H layer of ∼500 nm thickness
may be sufficient for the narrow bandgap absorber in an a-Si based multiple-junction solar cell. We enhanced the transport
properties as measured by the photoconductivity frequency mixing technique. These improved alloys do not necessarily show
an improvement in the degree of structural heterogeneity on the nanometer scale as measured by smallangle X-ray scattering.
Decreasing both the filament temperature and substrate temperature produced a film with relatively low structural heterogeneity
while photoluminescence showed an order of magnitude increase in defect density for a similar change in the process.
相似文献
12.
Nanocrystalline silicon (nc-Si) films were prepared by a plasma-enhanced chemical vapor deposition method at a deposition temperature below 220 °C with different dynamic pressures (Pg), hydrogen flow rates ([H2]), and RF powers, using SiH4/H2/SiF4 mixtures. We examined the photo-luminescence (PL) spectra and the structural properties. We observed two stronger and weaker PL spectra with a peak energies around EPL = 1.8 and 2.2-2.3 eV, respectively, suggesting that the first band was related to nanostructure in the films, and another band was associated with SiO-related bonds. The nc-Si films with rather large PL intensity was obtained for high [H2] and/or low pressure values, However, effects of [H2] are likely to be different from those of Pg. The average grain size (δ) and the crystalline volume fraction (ρ) at first rapidly increase, and then slowly increase, with increasing Pg. Other parameters exhibited opposite behaviors from those of δ or ρ. These results were discussed in connection with the changes in the PL properties with varying the deposition conditions. 相似文献
13.
14.
It is reported in this paper that the phenomenon of the saturated absorption of the exciton in hydrogenated nanocrystalline silicon (nc-Si:H) thin film fabricated by plasma enhanced chemical vapor deposition (PECVD) without any post-processing is observed at room temperature using pump-probe technology. This nonlinear optical absorption property is induced by the surface effect of the silicon nanoparticles in nc-Si:H thin films. 相似文献
15.
采用常规等离子体增强化学气相沉积工艺,以高H2稀释的SiH4作为反应气体源和PH3作为磷原子的掺杂剂,在p型(100)单晶硅((p)c-Si)衬底上, 成功地生长了施主掺杂型纳米硅膜((n)nc-Si:H),进而制备了(n)nc-Si:H/(p)c-Si异质结,并在230—420K温度范围内实验研究了该异质结的I-V特性.结果表明,(n)nc-Si:H/(p)c- Si异质结为一典型的突变异质结构,具有良好的温度稳定性和整流特性.正向偏压下
关键词:
(n)nc-Si:H/(p)c-Si异质结
能带模型
电流输运机构
温度特性 相似文献
16.
B.M. Monroy J. Aguilar-Hernández J. Fandiño G. Contreras-Puente J.C. Alonso 《Journal of luminescence》2006,121(2):349-352
Very thin (nanometric) silicon layers were grown in between silicon nitride barriers by SiH2Cl2/H2/NH3 plasma-enhanced chemical vapor deposition (PECVD). The multilayer structures were deposited onto fused silica and silicon substrates. Deposition conditions were selected to favor Si cluster formation of different sizes in between the barriers of silicon nitride. The samples were thermally treated in an inert atmosphere for 1 h at 500 °C for dehydrogenation. Room-temperature photoluminescence (RT-PL) and optical transmission in different ranges were used to evaluate the optical properties of the structures. UV-VIS absorption spectra present two band edges. These band edges are well fitted by the Tauc model typically used for amorphous materials. RT-PL spectra are characterized by strong broad bands, which have a blue shift as a function of the deposition time of the silicon layer, even for as-grown samples. The broad luminescence could be associated with the confinement effect in the silicon clusters. After annealing of the samples, the PL bands red shift. This is probably due to the thermal decomposition of N-H bonds with further effusion of hydrogen and better nitrogen passivation of the nc-Si/SiNx interfaces. 相似文献
17.
N. Fukata C. Li H. Morihiro K. Murakami M. Mitome Y. Bando 《Applied Physics A: Materials Science & Processing》2006,84(4):395-401
Significant enhancement of photoluminescence (PL) was attained for Er ions and Si nanocrystallites (nc-Si) in SiO2 films by two kinds of hydrogenation, using H2 molecules or H atoms. Er-doped SiO2 films containing Er impurities and a high density of nc-Si were fabricated by laser ablation of Er films deposited on Si substrate in an O2 gas atmosphere, followed by annealing at high temperatures in flowing Ar gas. Hydrogenation at 300–500 °C was found to effectively increase the PL intensity of Er ions as well as that of nc-Si. In particular, the hydrogen atom treatment dramatically shortens the hydrogenation time for the enhancement of Er PL compared to the hydrogen molecule treatment. Spectra of electron spin resonance showed a decrease in residual defects, namely, Pb-type defects located at the interfaces between nc-Si and SiO2 by hydrogenation. These results clearly show the effectiveness of hydrogen passivation for Si nanostructures; i.e., the increase in the Er PL and nc-Si PL due to hydrogen passivation of the nonradiative recombination centers located at the interfaces between nc-Si and SiO2. PACS 78.67.Bf; 71.20.Eh; 76.30.Mi; 81.15.Fg 相似文献
18.
L.H. Nguyen T.V. Phi P.Q. Phan H.N. Vu C. Nguyen-Duc F. Fossard 《Physica E: Low-dimensional Systems and Nanostructures》2007,37(1-2):54
It has been recently demonstrated that carbon nanotubes (CNTs) represent a new type of chemical sensor capable of detecting a small concentration of molecules such as CO, NO2, NH3.In this work, CNTs were synthesized by chemical vapor deposition (CVD) on the SiO2/Si substrate by decomposition of acetylene (C2H2) on sputtered Ni catalyst nanoparticles. Their structural properties are studied by atomic force microscopy, high-resolution scanning electron microscopy (HRSEM) and Raman spectroscopy. The CNTs grown at 700 °C exhibit a low dispersion in size, are about 1 μm long and their average diameter varies in the range 25–60 nm as a function of the deposition time. We have shown that their diameter can be reduced either by annealing in oxygen environment or by growing at lower temperature (less than 600 °C).We developed a test device with interdigital Pt electrodes on an Al2O3 substrate in order to evaluate the CNTs-based gas sensor capabilities. We performed room temperature current–voltage measurements for various gas concentrations. The CNT films are found to exhibit a fast response and a high sensitivity to NH3 gas. 相似文献
19.
S. M. M. Dufrène F. Cemin M. R. F. Soares C. Aguzzoli M. E. H. Maia da Costa I. J. R. Baumvol C. A. Figueroa 《Applied Physics A: Materials Science & Processing》2014,117(3):1217-1225
Hydrogenated amorphous carbon (a-C:H) is a state-of-the-art material with established properties such as high mechanical resistance, low friction, and chemical inertness. In this work, a-C:H thin films were deposited by plasma-assisted chemical vapor deposition. The deposition process was enhanced by electrostatic confinement that leads to decrease the working pressure achieving relative high deposition rates. The a-C:H thin films were characterized by elastic recoil detection analysis, Rutherford backscattering spectroscopy, scanning electron microscopy, Raman spectroscopy, and nanoindentation measurements. The hydrogen content and hardness of a-C:H thin films vary from 30 to 45 at% and from 5 to 15 GPa, respectively. The hardness of a-C:H thin films shows a maximum as a function of the working pressure and is linearly increased with the shifting of the G-peak position and I D/I G ratio. The structure of a-C:H thin films suffers a clustering process at low working pressures. A physical model is proposed to estimate the mean ion energy of carbonaceous species arriving at the surface of a-C:H thin films as a function of processing parameters as pressure and voltage and by considering fundamentals scattering events between ion species and neutral molecules and atoms. 相似文献