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1.
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
2.
采用射频磁控溅射镀膜系统,在玻璃衬底上制备了非晶硅(α-Si)/铝(Al)复合薄膜,结合氮气(N2)气氛中低温快速光热退火制备了纳米晶硅(nc-Si)薄膜;利用光学显微镜、共焦光学显微仪、X射线衍射(XRD)仪、拉曼散射光谱(Raman)仪和紫外-可见光-近红外分光光度计(UV-VIS-NIR)对纳米晶硅薄膜的表面形貌、物相及光学性能进行了表征,研究了退火工艺对薄膜性能的影响。结果表明: 300 ℃,25 min光热退火可使α-Si/Al膜晶化为纳米晶硅薄膜,晶化率为15.56%,晶粒尺寸为1.75 nm;退火温度从300 ℃逐渐升高到400 ℃,纳米晶硅薄膜晶粒尺寸、晶化率、带隙逐渐增加,表面均匀性、晶格畸变量逐渐减小;退火温度从400 ℃逐渐升高到500 ℃,纳米晶硅薄膜的晶粒尺寸、晶化率继续增加,带隙则逐渐降低;采用纳米晶硅薄膜的吸光模型验证了所制备的纳米晶硅薄膜的光学特性,其光学带隙的变化趋势与吸光模型得出的结果一致。 相似文献
3.
用PECVD薄膜沉积方法,成功地制备了磷掺杂纳米硅(nc-Si:H(P))薄膜.用扫描隧道电镜(STM)、Raman散射、傅里叶变换红外吸收(FTIR)谱、电子自旋共振(ESR)、共振核反应(RNR)技术对掺磷纳米硅进行了结构分析,确认了样品的微结构为纳米相结构.掺磷后膜中纳米晶粒的平均尺寸d减小,一般在25—45nm之间,且排列更加有序.掺磷nc-Si:H膜具有较高的光吸收系数,光学带隙在173—178eV之间,和本征nc-Si:H相同.掺杂nc-Si:H薄膜电导率在10-1关键词: 相似文献
4.
Charge storage characteristics of hydrogenated nanocrystalline silicon film prepared by rapid thermal annealing
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The early stages of hydrogenated nanocrystalline silicon (nc-Si:H)
films deposited by plasma-enhanced chemical vapour deposition were
characterized by atomic force microscopy. To increase the density of
nanocrystals in the nc-Si:H films, the films were annealed by rapid
thermal annealing (RTA) at different temperatures and then analysed
by Raman spectroscopy. It was found that the recrystallization
process of the film was optimal at around 1000℃. The effects
of different RTA conditions on charge storage were characterized by
capacitance--voltage measurement. Experimental results show that
nc-Si:H films obtained by RTA have good charge storage
characteristics for nonvolatile memory. 相似文献
5.
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
6.
7.
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
8.
基于对实验和理论的分析,提出一种异质结量子点隧穿(HQD)模型,并导出了纳米硅薄膜电导率完整的表达式.其主要思想是,纳米硅薄膜中的微晶粒(几个纳米大小)具有量子点特征,在微晶粒与界面之间由于两者能隙的差异构成晶间势垒,这类似于多晶硅中经常使用的晶间势垒模型(GBT).考虑到量子点中的单电子隧穿特征,认为纳米硅薄膜中的电传导是由微晶粒中电子弹道式输运与单电子越过势垒的隧穿构成的.这就是HQD模型的主要内容,理论结果与实验相符
关键词: 相似文献
9.
M. Ghrib M. GaidiT. Ghrib N. KhedherM. Ben Salam H. Ezzaouia 《Applied Surface Science》2011,257(21):9129-9134
Photoluminescence (PL) spectroscopy was used to determine the electrical band gap of nanocrystalline silicon (nc-Si) deposited by plasma enhancement chemical vapor deposition (PECVD) on porous alumina structure by fitting the experimental spectra using a model based on the quantum confinement of electrons in Si nanocrystallites having spherical and cylindrical forms. This model permits to correlate the PL spectra to the microstructure of the porous aluminum silicon layer (PASL) structure. The microstructure of aluminum surface layer and nc-Si films was systematically studied by atomic force microscopy (AFM), transmission electron microscopy (TEM), Raman spectroscopy and X-ray diffraction (XRD). It was found that the structure of the nanocrystalline silicon layer (NSL) is dependent of the porosity (void) of the porous alumina layer (PAL) substrate. This structure was performed in two steps, namely the PAL substrate was prepared using sulfuric acid solution attack on an Al foil and then the silicon was deposited by plasma enhanced chemical vapor deposition (PECVD) on it. The optical constants (n and k as a function of wavelength) of the deposited films were obtained using variable angle spectroscopic ellipsometry (SE) in the UV-vis-NIR regions. The SE spectrum of the porous aluminum silicon layer (PASL) was modeled as a mixture of void, crystalline silicon and aluminum using the Cauchy model approximation. The specific surface area (SSA) was estimated and was found to decrease linearly when porosity increases. Based on this full characterization, it is demonstrated that the optical characteristics of the films are directly correlated to their micro-structural properties. 相似文献
10.
氢化纳米硅(nc-Si:H)薄膜由于其具有奇异的结构和独特的性质,而引起广泛的关注.本文在等离子体增强化学气相淀积(PECVD)系统中,以高纯H2高度稀释SiH4为反应气体源,在射频和直流双重功率源的激励下制备成功具有纳米结构的nc-Si:H薄膜.利用高分辨率电子显微镜(HREM)、Raman散射谱(RSS)、扫描隧道电子显微镜(STM)等实验技术对nc-Si:H薄膜样品作了研究.基于对薄膜制备过程的动力学分析,提出nc-Si:H薄膜的分形生长模型:扩散与反应限
关键词: 相似文献
11.
M. GhribM. Gaidi N. KhedherT. Ghrib M. Ben SalemH. Ezzaouia 《Applied Surface Science》2011,257(9):3998-4003
In this paper we report detail investigation and correlation between micro-structural and optical properties of nanocrystalline silicon (nc-Si) deposited by plasma enhancement chemical vapor deposition (PECVD) on porous aluminum structure. The influence of the microstructure of the nc-Si thin films on their optical properties was investigated through an extensive characterization. The effect of anodisation currents on the microstructure of aluminum surface layer and nc-Si films was systematically studied by atomic force microscopy (AFM) and transmission electron microscopy (TEM), Raman spectroscopy and X-ray diffraction (XRD). The optical constants (n and k as a function of wavelength) of the films were obtained using variable angle spectroscopic ellipsometry (SE) in the UV-vis-NIR regions. The silicon layer (SL) was modeled as a mixture of void, crystalline silicon and aluminum using the Bruggeman approximation. Based on this full characterization, it is demonstrated that the optical characteristics of the films are directly correlated to their micro-structural properties. A very bright photoluminescence (PL) was obtained and find to depend on anodisation current. 相似文献
12.
Peng Wang Xia Wang Youming Chen Guangan Zhang Junyan Zhang 《Applied Surface Science》2007,253(7):3722-3726
Ti-doped hydrogenated diamond-like carbon (DLC) films were deposited on Si(1 0 0) substrates by a filtered cathodic vacuum arc (FCVA) method using Ar and CH4 as the feedstock. The composition and microstructure of the films were investigated by Raman spectroscopy, X-ray photoelectron spectroscopy and IR spectroscopy. The internal stress was determined by the radius of curvature technique. The influence of the bias voltage on the microstructure of the as-deposited films was investigated. It was found that the graphite-like bonds was dominated in the Ti-doped DLC film deposited at 0 V bias voltage. When bias voltage was increased to −150 V, more diamond-like bond were produced and the sp3 content in film reached the maximum value, after which it decreased and more graphite-like bonds feature produced with further increase of the negative bias voltage. The compressive internal in the Ti-doped DLC films also exhibited a maximum value at −150 V bias voltage. IR results indicated that CH bonded intensity reduced, and H atoms bonded with C atoms were substituted for the Ti atoms as the negative bias voltage increasing. All the composition and microstructure change can be explained by considering the plasma conditions and the effect of negative bias voltage applied to the substrate. 相似文献
13.
Nucleation and initial growth of diamond by biased hot filament chemical vapour deposition 总被引:1,自引:0,他引:1
W.L. Wang G. Sánchez M.C. Polo R.Q. Zhang J. Esteve 《Applied Physics A: Materials Science & Processing》1997,65(3):241-249
6 cm-2 for non-scratched silicon. The maximum value of the nucleation density was over 1011 cm-2 on mirror-polished Si(100) at -300 V. The transportation process of the ion flux from the filament to the substrate is discussed
in detail for biased substrates. The nucleation enhancement by the positive bias is believed to be a result of the increased
impingement of the electrons emitted from the filament to the substrate surface. The studies have shown that electron emission
from diamond plays a key role in negative-bias-enhanced nucleation by accelerating the dissociation of molecular hydrogen
and hydrocarbon species into various free radicals and
causing a plasma to be ignited near the substrate surface. The negative bias pretreatment is also a critical step in growing
heteroepitaxial diamond films: the enlargement of the area of diamond clusters in contact with the substrate enhances the
orientated growth of the films.
Received: 18 October 1996/Accepted: 4 February 1997 相似文献
14.
Irina Gouzman 《Surface science》2006,600(4):773-781
Combining functional organic self-assembled monolayers (SAMs) with conventional semiconductor materials is a key step in the development of integrated electronics-based devices. T-BAG (Tethering by Aggregation and Growth) has been shown to be a simple and reliable method to grow SAMs of alkylphosphonates on oxide surfaces. However, distinguishing SAMs from ultra-thin multilayers is a challenge for most conventional surface characterization techniques.Self-assembled films of octadecylphosphonic acid (ODPA) were deposited on oxide-covered silicon coupons, converted to the corresponding phosphonates, and characterized by high resolution angularly resolved X-ray photoelectron spectroscopy (XPS). It was our goal to distinguish among different bonding configurations for phosphorous in the phosphonate head groups, namely, mono-dentate, bi-dentate or tri-dentate interactions with the oxide surface, as well as to assess quantitatively the near-surface layer composition.We also present an innovative method that allows us to distinguish between monolayer and multilayer films of ODPA on silicon oxide surfaces. This method is based on differential surface charging effects in XPS. It was found that variation in the ODPA film thickness causes differential responses of various spectral characteristics to an electrical bias applied to the sample during XPS measurements. Both positive and negative applied biases were found to affect the carbon core-level (C1s) line-shape and intensity in the case of the multilayer ODPA film, whereas line-shapes and intensities of all XPS lines measured for the monolayer film were unaffected by the application of a dc bias in the ±30 V range. 相似文献
15.
The excimer laser-induced crystallization technique has been
used to investigate the preparation of nanocrystalline silicon (nc-Si)
from amorphous silicon ($\al$-Si) thin films on silicon or glass
substrates. The $\al$-Si films without hydrogen grown by pulsed-laser
deposition are chosen as precursor to avoid the
problem of hydrogen effluence during annealing. Analyses
have been performed by scanning electron microscopy, atomic
force microscopy, Raman scattering spectroscopy and high-resolution
transmission--electron microscopy. Experimental results show
that silicon nanocrystals can be formed through laser annealing.
The growth characters of nc-Si are strongly dependent on the laser
energy density. It is shown that the volume of the molten silicon
predominates essentially the grain size of nc-Si, and the surface
tension of the crystallized silicon is responsible for the mechanism of nc-Si growth. 相似文献
16.
17.
大面积均匀纳米金刚石薄膜制备研究 总被引:7,自引:0,他引:7
报道了一种利用偏压恒流等离子辅助热丝化学气相沉积城硅基板上制备大面积均匀纳米金刚石薄膜的新工艺,在不同沉积条件下研究了纳米金刚石薄膜的成核和生长过程,并通过扫描电镜、拉曼光谱和表面粗糙度测试仪观察了纳米金刚石薄膜的结构特征。最后成功制备了直径100mm、平均晶粒尺寸10nm的光滑纳米金刚石薄膜。 相似文献
18.
Fabrication of nc-Si/SiO2 structure by thermal oxidation method and its luminescence characteristics
Nano-crystalline silicon/silicon oxide (nc-Si/SiO2) structures have been prepared from amorphous silicon films on both silicon and quartz substrates by using electron-beam evaporation approach and annealing at temperatures about 600 ℃ in air. As a thermal oxidation procedure, the annealing treatment is not only a crystallization process but also an oxidation process. Scanning electron microscopy is employed to characterize the surface morphology of the nc-Si/SiO2 layers. Transmission electron microscopy study shows the sizes of nc-Si grains on the two different substrates. The nc-Si/SiO2 structures exhibit visible luminescence at room temperature as confirmed by photoluminescence spectroscopy. Comparing the photoluminescence spectra of different samples, our results agree with the quantum confinement-luminescence center model. 相似文献
19.
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
20.
S. Flickyngerova K. Shtereva D. Hasko V.Tvarozek E. Vavrinsky 《Applied Surface Science》2008,254(12):3643-3647
Zinc oxide (ZnO) and aluminium-doped zinc oxide (ZnO:Al) thin films were prepared by RF diode sputtering at varying deposition conditions. The effects of negative bias voltage and RF power on structural and optical properties were investigated. X-ray diffraction measurements (XRD) confirmed that both un-doped and Al-doped ZnO films are polycrystalline and have hexagonal wurtzite structure. The preferential 〈0 0 1〉 orientation and surface roughness evaluated by AFM measurements showed dependence on applied bias voltage and RF power. The sputtered ZnO and ZnO:Al films had high optical transmittance (>90%) in the wavelength range of 400-800 nm, which was not influenced by bias voltage and RF power. ZnO:Al were conductive and highly transparent. Optical band gap of un-doped and Al-doped ZnO thin films depended on negative bias and RF power and in both cases showed tendency to narrowing. 相似文献