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1.
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
2.
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
3.
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
4.
A fabrication process of silicon field-emission arrays is reported, in which thin films of amorphous hydrogenated carbon (a-C:H) are employed as masks in a two-step plasma-etching process, using pure SF6 and a mixture of SF6 and O2. In comparison with processes that involve SiO2 masks, the use of a-C:H improved the selectivity of the plasma etching, particularly in the case of pure SF6. An estimation of Utsumi's figure of merit showed that a significant enhancement in electric field can be achieved, as a result of the sharp tips fabricated through this process. 相似文献
5.
Wet oxidations of (100) silicon implanted with an arsenic dose of 2 × 1016 cm−2 and an energy of 30 keV were carried out in the temperature range between 600 and 900° C. The oxidation rate is increased
on the arsenic implanted samples up to a factor of 2000 as compared to undoped samples. During these oxidations the arsenic
suicide phase AsSi is precipitated at the oxide/silicon interface. After short oxidation times at 600° C, a continuous AsSi
layer is found. It is dissolved during extended oxidation times and finally almost all As is incorporated in the oxide. After
900° C oxidations, substantial AsSi crystallites remain at the Si/SiO2 interface. They are still observed up to the larg-est oxide thickness grown (2.3 μm). The AsSi phase and the distribution
of the im-planted arsenic were analyzed by TEM, SIMS and XRF measurements. 相似文献
6.
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
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.
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
9.
Solar cells based on hydrogenated amorphous silicon are now made from a variety of materials including alloys and microcrystalline
films. Research aimed at improving cell efficiency should emphasize studies of alloys and metastable defects. We discuss several
research topics related to the growth, structure, and electronic properties of these materials, which should lead to improved
photovoltaic devices. 相似文献
10.
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
11.
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
12.
13.
14.
A. E. Delahoy R. W. Griffith F. J. Kampas P. E. Vanier 《Journal of Electronic Materials》1982,11(5):869-882
Concentrations of monochlorosilane (SiH3Cl) of the order of 2500 ppm have been detected in some commercial tanks of silane by mass spectrometry and optical emission
spectroscopy (OES). This impurity is shown to depress the position of the Fermi level in a-Si:H, resulting in lower photoconductivity
and solar cell efficiency.
This research was performed under the auspices of the U.S. Department of Energy under Contract No. DE-AC0276CH00016. 相似文献
15.
Amorphous silicon (a-Si) thin films were prepared on glass substrates by plasma enhanced chemical vapor deposition (PECVD). Influence of annealing temperature on the microstructure, surface morphology, and defects evolution of the films were studied by X-ray diffraction (XRD), atomic force microscope (AFM) and positron annihilation Doppler broadening spectroscopy (DBS) based on a slow positron beam, respectively. The S parameter of the as-deposited a-Si thin film is high, indicative of amorphous state of Si film with many defects. The a-Si gradually grows into polycrystalline silicon with increasing temperature to 650 °C. For the films annealed below ~450 °C, positron diffusion lengths are rather small because most positrons are trapped in the defects of the a-Si films and annihilated there. With further rising the temperature to 600 °C, the diffusion length of positrons increases significantly due to the removal of vacancy-type defects upon annealing at a high temperature. The results indicate that the coalescence of small vacancy-type defects in a-Si thin film and the crystallization of a-Si occur around 450 °C and 650 °C, respectively. 相似文献
16.
非晶硅薄膜(a-Si)是目前重要的光敏材料,在很多领域得到广泛应用。直流磁控溅射具有工艺简单.沉积温度低等优点,是制备薄膜的一种重要技术。采用直流磁控溅射工艺在玻璃基板上沉积薄膜,并对样品进行了退火处理。研究了沉积速率与溅射功率的关系。结果表明薄膜的沉积速率与溅射功率近似有线性关系。利用X射线衍射(XRD)对薄膜进行了分析鉴定,结果表明溅射的薄膜是非晶硅薄膜。利用扫描电子显微镜(SEM)对非晶硅薄膜的表面形貌进行了观察和分析,与X射线衍射测试的结果一致。所以.利用直流磁控溅射工艺能在常温下能快速制备出良好的非晶硅薄膜。 相似文献
17.
Maruf Hossain Husam H. Abu-Safe Hameed Naseem William D. Brown 《Journal of Electronic Materials》2006,35(1):113-117
The effects of hydrogen on aluminum-induced crystallization (AIC) of sputtered hydrogenated amorphous silicon (a-Si:H) were
investigated by controlling the hydrogen content of a-SiH films. Nonhydrogenated (a-Si) and hydrogenated (a-Si:H) samples
were deposited by sputtering and plasma-enhanced chemical vapor deposition (PECVD). All aluminum films were deposited by sputtering.
Hydrogen was introduced into the sputter-deposited a-Si films during the deposition. After deposition, the samples were annealed
at temperatures from 200°C to 400°C for different periods of time. X-ray diffraction (XRD) patterns were used to confirm the
presence and degree of crystallization in the a-Si:H films. For nonhydrogenated films, crystallization initiates at a temperature
of 350°C. The crystallization of sputter-deposited a-Si:H initiates at 225°C when 14% hydrogen is present in the film. As
the hydrogen content is decreased, the crystallization temperature increases. On the other hand, the crystallization initiation
temperature for PECVD a-Si:H containing 11at.%H is 200°C. Further study revealed that the crystallization initiation temperature
is a function, not only of the total atomic percent hydrogen in the film, but also a function of the way in which the hydrogen
is bonded in the film. Models are developed for crystallization initiation temperature dependence on hydrogen concentration
in a-Si:H thin films. 相似文献
18.
The diffusion of a chromium bottom contact has been studied through thin 10-nm amorphous silicon film. The concentration of the diffused impurity has been analyzed by an X-ray photon spectroscopy technique and the diffusion coefficient was estimated. Diffusion annealing was carried out in vacuum (10?6 mTorr), the temperature was kept at 400°C, and the annealing time was varied from 0 to 300 min. The authors propose that diffusion of chromium in thin hydrogenated amorphous film is limited by silicide formation at the metal-silicon interface. 相似文献
19.
Ni金属诱导晶化非晶硅(a-Si:H)薄膜 总被引:1,自引:1,他引:0
对在氢化非晶硅薄膜(a-Si:H)上溅射金属Ni的样品进行金属诱导晶化(MIC)/金属诱导横向晶化(MILC),制备多晶硅薄膜(p-Si)的上艺及薄膜特性进行了研究。XRD测最结果表明非晶硅在500℃退火1h后就已经全部晶化。金属诱导晶化的优选晶向为(220).而且晶粒随退火时间的延长而长大。非晶硅薄膜样品500℃下退火6h后的扫描电镜照片显示,原金属镍覆盖区非晶硅全部晶化.晶粒均匀.平均晶粒大小约为0.3μm,而且已经发生横向晶化。EDS测试Ni在晶化的非晶硅薄膜中的原子百分含量分析表明,金属Ni在MILC过程中的作用只是催化晶化.除了少量残留在MILC多晶硅中外.其余的Ni原子都迁移至晶化的前沿。500℃下退火20h后样品的Raman测试结果也表明.金属离子向周边薄膜扩散.横向晶化了非晶硅薄膜。 相似文献
20.
T. Zimmermann A. J. Flikweert T. Merdzhanova J. Woerdenweber A. Gordijn U. Rau F. Stahr K. Dybek J. W. Bartha 《Progress in Photovoltaics: Research and Applications》2014,22(2):198-207
Hydrogenated amorphous silicon (a‐Si:H) is conventionally deposited using static plasma‐enhanced chemical vapor deposition (PECVD) processes. In this work, a very high frequency (VHF) dynamic deposition technique is presented, on the basis of linear plasma sources. This configuration deploys a simple reactor design and enables continuous deposition processes, leading to a high throughput. Hence, this technique may facilitate the use of flexible substrates. As a result, the production costs of thin‐film silicon solar cells could be reduced significantly. We found a suitable regime for the homogeneous deposition of a‐Si:H layers for growth rates from 0.35–1.1 nm/s. The single layer properties as well as the performance of corresponding a‐Si:H solar cells are investigated and compared with a state‐of‐the‐art radio frequency (RF) PECVD regime. By analyzing the Fourier transform infrared spectroscopy spectra of single layers, we found an increasing hydrogen concentration with deposition rate for both techniques, which is in agreement with earlier findings. At a given growth rate, the hydrogen concentration was at the same level for intrinsic layers deposited by RF‐PECVD and VHF‐PECVD. The initial efficiency of the corresponding p–i–n solar cells ranged from 9.6% at a deposition rate of 0.2 nm/s (RF regime) to 8.9% at 1.1 nm/s (VHF regime). After degradation, the solar cell efficiency stabilized between 7.8% and 5.9%, respectively. The solar cells incorporating intrinsic layers grown dynamically using the linear plasma sources and very high frequencies showed a higher stabilized efficiency and lower degradation loss than solar cells with intrinsic layers grown statically by RF‐PECVD at the same deposition rate. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献