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1.
Hydrogen concentrations and bonding configurations were studied in hydrogenated amorphous silicon (a-Si:H) films deposited
at 50‡C using the magnetron mode of sputtering with partial hydrogen concentrations between 0 and 90 percent in flowing argon.
Hydrogen content within the films was determined from nuclear reaction analysis, and the chemical bonding of hydrogen was
determined from infrared absorption of as-deposited, thermally annealed, and ion-bombarded films. Hydrogen/silicon ratios
in the films increase to a maximum of 0.31 with increasing hydrogen in the deposition system. Ion backscattering shows ∼ 6
at.% argon trapped in the films, but no oxygen was detected by either ion backscattering or by sputter-Auger analysis. The
wag and bend modes for Si-H in the films are typical of sputter-deposited a-Si:H; however, the stretch mode region is atypical
with absorption near 2000 cm−l dominating even for H/Si ratio of 0.27. From results of thermal annealing and post-deposition ion bombardment, it is concluded
that argon ion bombardment during deposition produces enhanced absorption near 2000 cm-1 in these a-Si:H films deposited by magnetron sputtering.
This work was sponsored in part by the U. S. Department of Energy, under Contract DE-AC04-76-DP00789 and the U. S. Army Research
Office, Contract DAA29-79-C-0026.
U. S. Department of Energy facility. 相似文献
2.
T. D. Moustakas 《Journal of Electronic Materials》1979,8(3):391-435
Hydrogenated a-Si, whose properties can be modified by impurity doping, can be produced either by decomposition of silane
or by reactive sputtering of Si in an argon-hydrogen plasma. This article reviews advances made during the past few years
in the preparation and characterization of films produced by the second method. The basic deposition conditions are summarized.
The conclusions of analytical studies (photo-emission, infrared spectroscopy, and volumetric measurements of evolved gases),
regarding the amount of hydrogen and its bonding configuration in the network, are outlined. The optical, carrier transport,
photoconductivity and photoluminescence properties as a function of hydrogen content and doping are described. Electron drift
mobilities, deduced from steady state and transient photoconductivity are presented. The transport and recombination properties
are discussed with existing models of amorphous semiconductors, and are found to be consistent with atomic relaxations, i.e.
polaronic effects. 相似文献
3.
对采用等离子增强化学气相淀积法(PECVD)制备的氢化非晶硅(a-Si:H)薄膜进行了退火释H2实验,并对三文治结构膜层生长工艺作了改进。红外透射光谱表明:提高退火温度及增加退火时间会造成Si-H键断裂释放H2影响器件结构完整;不断改进设计,最终采用精简有效热敏面积及将退火工艺提前以扩张释H2渠道的方案,获得600℃退火后仍保持完整三文治结构的优化设计流程。 相似文献
4.
Effects of oxygen in Ni films on the Ni-induced lateral crystallization (NILC) of amorphous silicon (a-Si) films at various
temperatures have been investigated. It was found that oxygen in Ni films retarded the nucleation of polycrystalline silicon
(poly-Si) from a-Si, but had little effect on the growth rate of poly-Si. This is because that needed an incubation period
to be reduced to Ni metal for the subsequent mediated crystallization of a-Si. 相似文献
5.
为研究波长对连续激光晶化非晶硅(a-Si) 薄膜过程的影响,利用连续Ar+-Kr+激光对a-Si薄膜晶 化,在5ms固定照射时间下,改变激光波长,采用拉曼光谱测试技术和场发射扫描电子显微 镜(SEM)研究在不同 激光功率密度下薄膜晶化后的特性。结果表明,a-Si薄膜的晶化阈值随着波长的 增大而增大,当波长为 458nm时薄膜晶化阈值为13.2kW/cm2,波长 为647nm时,晶化阈值为19.2kW/cm2;在激光功率密度范 围为0~27.1kW/cm2内,薄膜的最大晶化率受波长的影响相对较小 ,但总体也随着波长的增大而呈增大 趋势,当波长为647nm时,在激光功率密度26.5kW/cm2处,晶化率达到最大值75.85%。 相似文献
6.
多晶硅薄膜比非晶硅薄膜具有更高的电子迁移率,在器件中表现出更优良的性能,脉冲激光结晶非晶硅薄膜制备多晶硅薄膜的方法具有热积存小、对衬底影响小、成本低等优点。使用532 nm固体纳秒激光器进行了非晶硅薄膜激光结晶实验,为了解决直接使用高斯光束结晶时因光斑能量分布带来的结晶效果不均匀,首先基于光束整型系统将圆形的高斯光束整型成为线性平顶光束,而后研究单脉冲能量密度、脉冲个数、非晶硅薄膜厚度对结晶效果的影响。结果表明,线性平顶光束用于非晶硅薄膜结晶具有更好的均匀性,对于100 nm非晶硅薄膜,随着能量密度的增加,晶粒逐渐变大,直到表面出现热损伤,最大晶粒尺寸约为1 μm×500 nm。随着脉冲个数的增加,表面粗糙度有减小的趋势,观察到的最小粗糙度约为2.38 nm。对于20 nm超薄非晶硅薄膜,只有当能量密度位于134 mJ/cm2和167 mJ/cm2之间、脉冲个数大于或等于八个时才能观察到明显的结晶效果。 相似文献
7.
Nagarajan Sridhar DDL Chung W. A. Anderson J. Coleman 《Journal of Electronic Materials》1995,24(10):1451-1459
Plasma Physics Corporation, P.O. Box 548, Locust Valley, NY 11650 The changes in enthalpy and entropy due to hydrogen evolution
in hydrogenated amorphous silicon films were measured by differential scanning calorimetry (DSC). Hydrogen evolution was associated
with an endothermic DSC peak, as supported by thermogravimetric analysis and evolved gas analysis. The en-thalpy and entropy
changes of hydrogen evolution increased with heating rate and hydrogen content, because the evolution involved not only Si-H
bond breaking, but also defect formation (such as Si-Si bond breaking), which was enhanced by a high flow of evolving hydrogen.
In contrast, the activation energy of hydrogen evolution was controlled by the doping rather than the hydrogen content, because
doping affected the Si-H bonding, which in turn affected the state before hydrogen evolution. Crystallization, which occurred
at tempera-tures higher than hydrogen evolution, was delayed for the amorphous silicon film in a higher disordered state after
hydrogen evolution, suggesting that hydrogen content influenced the crystallization process. 相似文献
8.
Lu Huang Jing Jin Weimin Shi Zhijun Yuan Weiguang Yang Zechun Cao Linjun Wang Jun Zhou Qihong Lou 《Materials Science in Semiconductor Processing》2013,16(6):1982-1987
The effect of laser energy density on the crystallization of hydrogenated amorphous silicon (a-Si:H) thin films was studied theoretically and experimentally. The thin films were irritated with a frequency-doubled (λ=532 nm) Nd:YAG pulsed nanosecond laser. An effective finite element model was built to predict the melting threshold and the optimized laser energy density for crystallization of intrinsic amorphous silicon. Simulation analysis revealed variations in the temperature distribution with time and melting depth. The highest crystalline fraction measured by Raman spectroscopy (84.5%) agrees well with the optimized laser energy density (1000 mJ/cm2) in the transient-state simulation. The surface morphology of the thin films observed by optical microscopy is in fairly good agreement with the temperature distribution in the steady-state simulation. 相似文献
9.
Electron-beam-induced current (EBIC) and secondary electron image (SEI) modes of a scanning electron microscope (SEM) are
utilized for characterization of charge collection inhomogeneities in hydrogenated amorphous silicon devices. These inhomogeneities
are due to such fabrication defects as substrate surface roughness, pin holes, blistering and lift-off. SEM observations are
correlated with the electrical properties of the devices. Electronirradiation-induced damage in these devices is also investigated
by measuring the EBIC time decay at continuous electron irradiation as a function of both the electron -beam energy and current.
This decay mechanism is based on the formation of electron-irradiation-induced microscopic defects that act as recombination
centers and reduce the lifetime of carriers. 相似文献
10.
Shin‐ichiro Sato Hitoshi Sai Takeshi Ohshima Mitsuru Imaizumi Kazunori Shimazaki Michio Kondo 《Progress in Photovoltaics: Research and Applications》2013,21(7):1499-1506
This paper reports temperature influence on radiation degradation of hydrogenated amorphous silicon (a‐Si : H) solar cells. Degradation behaviors of a‐Si : H solar cells irradiated with protons at 331 K are compared with that at 298 K (room temperature). Variations with time in the post‐irradiation electrical properties are also investigated. It is found that the radiation degradation of the electrical properties at 331 K is significantly smaller than that at room temperature. Also, all the electrical properties (short‐circuit current, open‐circuit voltage, output maximum, and fill factor) recover with time after irradiation even at room temperature. The characteristic time of thermal annealing of short‐circuit current is larger as the temperature is higher. These results indicate that temperature during irradiation and elapsed time from irradiation to measurement is an important parameter for radiation degradation of a‐Si : H solar cells. Therefore, these parameters should be controlled in conducting the ground radiation tests. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
11.
The aim of this paper is to provide a better understanding of hydrogenated amorphous silicon thin films (a-Si:H) in relation to their optical properties: refractive index, optical gap, absorption coefficient, thickness and surface roughness. The transmission spectrum of the films, deposited with various rf discharge power densities by an optimized plasma enhanced chemical vapor deposition (PECVD) method, at a high rate (>10 Å/sec), was measured over a range in wavelength from 500 to 1100 nm. An approximate model is utilized to describe the surface roughness. In this model, the surface roughness is modeled as a mixed layer of 50 percent of a-Si:H and 50 percent of air and the optical constant of the rough layer is derived using the Bruggemann effective medium approximation (EMA). The gradient iteration method of numerical analysis is used to solve the nonlinear equations in the study. Our results show that the potential underestimation of refractive index and resulting overestimation of film thickness can be overcome by considering the reflection of the rough surface. The method is carried out on the transmission data and the influence of rf discharge power density on the properties of the film is discussed in detail. 相似文献
12.
将具有能量92ke V、剂量1×1015/cm 2 的 B F+ 注入由 P E C V D 方法制备的a Si∶ H 薄膜中,然后用功率为 60 W 、束斑直径 02cm 的 C W C O2 激光器进行 10s 快速退火。再用扫描电子显微镜( S E M)进行显微形貌观察。分析结果指出:由于 B F+ 的注入,使a Si∶ H 薄膜中产生了多重结构缺陷,其表面轮廓是类似矩形和方形的图形;发现退火中的晶化是从这些缺陷的棱边开始。最后对晶化过程和机理进行了讨论。 相似文献
13.
14.
为了减低非晶硅薄膜太阳能电池的光致衰减效应和提高其光电转换效率,用等离子体化学气相沉积系统制备了本征非晶硅薄膜,用波长为248nm的KrF准分子激光器激光晶化了非晶硅表层,用共焦显微喇曼测试技术研究了非晶硅薄膜在不同的激光能量密度和不同的频率下的晶化状态,并用扫描电子显微镜测试晶化前后薄膜的形貌。结果表明,随着激光能量密度的增大,薄膜晶化效果越来越好,能量密度达到268.54mJ/cm2时晶化效果最好,此时结晶比约为76.34%;最佳的激光能量密度范围是204.99mJ/cm2~268.54mJ/cm2,这时薄膜表面晶化良好;在1Hz~10Hz范围内,激光频率越大晶化效果越好;晶化后薄膜明显出现微晶和多晶颗粒,从而达到了良好的晶化效果。 相似文献
15.
W. Hu Florence Y. M. Chan D. P. Webb Y. C. Chan Y. W. Lam 《Journal of Electronic Materials》1996,25(12):1837-1840
The optical properties of hydrogenated amorphous silicon thin films prepared by a new thermocatalytic plasma enhanced chemical
vapor deposition (PECVD) method are here reported for the first time. The transmission spectrum of the film, deposited at
a rate of 1.5 nm/s, was measured between 500 and 1100 nm. The envelopes of the transmission spectrum interference maxima and
minima were analyzed to reveal the absorption coefficient α(λ@#@), the refractive indexn(λ), the average thickness of the film (791 nm) and the variation of the thickness (11.4 nm), using an analysis which takes into
account film inhomogeneity. The modified Newton's method of numerical analysis was used to obtain the optical parameters.
The optical band gap ε0} was determined to be 1.69 eV from the absorption coefficient spectrum, commensurate with values quoted for lower deposition
rate PECVD films. The value for ε0}, the small variation of the film thickness, and a value for the defect density of 3.7 x 1015}cm-3} determined for similar material in other work indicate that the thermocatalytic PECVD method can produce acceptable quality
films at a high deposition rate. 相似文献
16.
17.
S. L. Wu C. L. Lee T. F. Lei T. L. Lee L. J. Chen 《Journal of Electronic Materials》1992,21(8):811-816
The structural morphology of the poly-single crystalline silicon interface of a diode formed with a stacked-amorphous-silicon (SAS) film has been investigated. Secondary ion mass spectroscopy analyses showed the existence of multi-dopant segregation peaks at each layer boundary and at the poly-single crystalline silicon interface. The break-up at the poly-single silicon interface and the epitaxial regrowth of the polysilicon realigned to the silicon substrate were found to depend not only on the polysilicon deposition and the post annealing conditions, but also on the number and the thickness of the stacked amorphous silicon layers. For the diode formed with a six-layer stacked amorphous silicon, break-up of the interface was found to occur even at an annealing temperature as low as 900°C. After an additional annealing at 1000°C for 20 min, the interface was fully broken-up and the epitaxial regrowth layer of the polysilicon could be as thick as 760Å. 相似文献
18.
19.
Kyoung-Wan Park Ki-Taek Cho Jin-Yong Ahn Duck-Kyun Choi 《Journal of Electronic Materials》2004,33(7):786-789
The crystallization of amorphous silicon (a-Si) was achieved by field-aided lateral crystallization (FALC). Under the influence
of an electric field, Cu is found to drastically enhance the lateral crystallization velocity of a-Si. When an electric field
of 30 V/cm was applied to selectively Cu-deposited a-Si films during heat treatment at 350°C, dendrite-shaped crystallization
of a-Si progressed toward the Cu-free region, and the crystallization from the negative electrode side toward the positive
electrode side was accelerated. The Cu-FALC polycrystalline-silicon (poly-Si) film has a crystalline volume fraction of 58%
with 300-nm-long, rod-shaped grains. Low-temperature crystallization of a-Si in an electric field appears to be caused by
enhanced migration of the Cu ions in the a-Si region. 相似文献
20.
The metal-induced crystallization of poly-Si and the mobility enhancement of thin film transistors fabricated on a glass substrate 总被引:1,自引:0,他引:1
In this study, we report on the fabrication of poly-crystalline silicon (poly-Si) using the metal-induced crystallization (MIC) method and its application to thin film transistors (TFTs). The top gate of the p-type TFTs, whose active layer used MIC poly-Si annealed for 1 h at 650 °C, showed a field effect mobility (μFE) of 7.5 cm2/V s. By increasing the crystallization time to 5 h, the quality of the MIC poly-Si was improved. The μFE increased from 7.5 to 15 cm2/V s. In order to enhance the channel mobility, the Si dangling bonds, which were produced during the transformation from the amorphous phase to the poly-crystalline phase of silicon (Si), were reduced by using plasma hydrogenation. Measurements show that the μFE reached 45 cm2/V s after passivation by an inductively coupled plasma chemical vapor deposition (ICPCVD) system. 相似文献