共查询到20条相似文献,搜索用时 15 毫秒
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L. Wang X. Huang Z. Ma Z. Li J. Shi L. Zhang Y. Bao X. Wang W. Li J. Xu K. Chen 《Applied Physics A: Materials Science & Processing》2002,74(6):783-786
The crystallinity of Si/SiNx multilayers annealed by a rapid thermal process and furnace annealing is investigated by a Raman-scattering technique and
transmission electron microscopy. It is found that the crystallization temperature varies from 900 °C to 1000 °C when the
thickness of a-Si:H decreases from 4.0 nm to 2.0 nm. Raman measurements imply that the high crystallization temperature for
the a-Si:H sublayers originates from the confinement modulated by the interfaces between a-Si:H and a-SiNx:H. In addition to the annealing temperature, the thermal process also plays an important role in crystallization of a-Si
sublayers. The a-Si:H sublayers thinner than 4.0 nm can not be crystallized by furnace annealing for 30 min, even when the
annealing temperature is as high as 1000 °C. In contrast, rapid thermal annealing is advantageous for nucleation and crystallization.
The origin of process-dependent crystallization in constrained a-Si:H is briefly discussed.
Received: 11 April 2001 / Accepted: 20 June 2001 / Published online: 30 August 2001 相似文献
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本文从a-Si:H体材料的缺陷态模型出发,考虑在a-Si:H/a-SiNx:H超晶格中由于空间电荷转移掺杂效应,以及界面不对称引起的a-Si:H阱层的能带下降和弯曲,严格求解空间电势分布和电荷分布,发现a-Si:H阱层中能带的下降值远大于由界面电荷不对称所引起的两端电势能差,且随转移到阱层中的电荷总量的变化非常敏感。空间电荷分布比较平缓,当不对称参数K=0.9时,空间电荷浓度的最大差值不到两倍。在此基础上,计算了超晶格中光电导的温度曲线,发现引起超晶格中暗电导和光电导相对于单层膜增大的主要原因是转移电荷量的多少,而界面电荷不对称的影响则小得多。计算中对带尾态采用Simmons-Taylor理论,考虑a-Si:H中悬挂键的相关性,并用巨正则分布讨论其在复合过程中的行为。
关键词: 相似文献
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We report a determination of the density of singly-occupied dangling bonds at the a-Si:H/a-SiNx:H interface obtained from ESR measurements of superlattice structures. The surprisingly low result of 1.3 × 1010 cm?2 calls for a reexamination of previous transport and optical measurements. The ESR data do not preclude a high interface density of charged dangling bonds. 相似文献
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In this study the electron diffusion length L
n is determined from the relative spectral response of the photocurrent characteristics of the p/i/n sandwich structure ITO/a-SiC:H(p-type)/a-Si:H/a-Si:H(n-type)/Pd. The techniques used for the preparation of the a-Sic:H and a-Si:H amorphous films were glow-discharge and rf magnetron sputtering, respectively. The thickness of the p-type, intrinsic and n-type layer were 400 Å, 7000 Å and 600 Å, respectively. The response of the short-circuit current density J
sc was measured versus the photon energy hv at both constant light intensity and constant temperature. The electron diffusion length was found to be 0.31 m by means of the method of Agarwala and Tewary. Although, in the case of single crystals many diffusion length measurements have been made, there are only few papers for amorphous silicon this films [1]. As it is well-known, the diffusion length of the charge carriers is the most important parameter from the point of view of solar cell applications [2]. In order to obtain a high efficiency in a solar cell all carriers created under illumination in the intrinsic layer should reach the electrodes [3]. In the case that the thickness of the intrinsic layer is much larger than the diffusion length, not all carriers can reach the electrodes and, accordingly, a low efficiency results [4]. On the other hand, carriers which reach the electrodes without thermalizing do not contribute to the photocurrent and finally the efficiency of the solar cell is negatively affected. In order to avoid such an effect to a large extent, the thickness of the amorphous layers in a p/i/n solar cell must be conveniently chosen compared to the diffusion length of the carriers.Here it is aimed to determine the electron diffusion length. In order to achieve this goal, the photocurrent characteristics of an ITO/a-SiC:H(p-type)/a-Si:H/a-Si:H(n-type)/Pd structure was measured versus the photon energy at constant light intensity and constant temperature. In order to determine the electron diffusion length, the method of Agarwala and Tewary [5] was utilized. 相似文献
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《Superlattices and Microstructures》1995,17(1):1-4
Surface Rayleigh acoustic waves and related elastic properties of quasiperiodic and periodic modulated a-Si:H/a-SiNx:H superlattices have been studied by means of a light-scattering technique. Changes in the phase velocity of the surface Rayleigh acoustic waves as a function of sublayer (a-Si:H) thickness are interpreted using an effective medium model. Despite the existence of structural mismatch in the bond-length and coordination number and of structural disorder in the bond-angle for Si-N and Si-Si, no appreciable discrepancy between the measured results and the theoretical predictions has been found. 相似文献
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《Superlattices and Microstructures》1998,23(5):991-997
The induced defects and their distribution in a-Si:H/a-SiNx:H multilayers are determined using an electromagnetic technique (EMT) and positron annihilation technique (PAT). It is found that the distributions of the induced defects in the interface regions on both sides of the a-Si:H sublayer are asymmetric and related to the growth direction of the film; a large number of induced defects are found only in the interface region away from the substrate. 相似文献
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本文报道了a-Si:H/a-SiNx:H超晶格薄膜光致发光某些性质的研究。实验发现,这种超晶格薄膜光致发光的强度和峰值能量随交替层a-Si:H厚度,测量温度及光照时间等而变化。同时还发现,在阴、阳两极上,利用GD法沉积的样品,发光强度和峰值能量也有所不同。文中对这些实验结果作了初步解释。 相似文献
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R. Schwarz T. Fischer P. Hanesch T. Muschik J. Kolodzey
H. Cerva
H. L. Meyerheim
B. M. U. Scherzer
《Applied Surface Science》1991,50(1-4):456-461The goal of this work is to study the sharpness of interfaces in amorphous silicon based compositional multilayers (superlattices) by a number of different techniques and to discuss their limitations. From monitoring plasma transients during glow discharge deposition of a-Si:H/a-SiC:H multilayers, a lower limit of 3 Å for interface sharpness is estimated. Transmission electron microscopy (TEM) images yield an upper limit of 5–10 Å. These images directly show the increase in undulation from the substrate towards the film surface. From the comparison of simulated X-ray diffraction (XRD) spectra with measurements the interface sharpness is found to be between 5 and 8 Å. Using a series of multilayers with increasing number of interfaces, structural characteristics of the interfacial region can be extracted. For example, infrared absorption spectroscopy (FTIR) and elastic recoil detection (ERD) lead to an estimate of 1.1 × 1014 cm-2 additional hydrogen atoms per single interface. 相似文献
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《Solid State Communications》1986,58(6):379-381
A new type of amorphous semiconductor superlattices consisting of alternating layers of a-Si: H and a-C: H has been synthesized by r.f. plasma deposition in a single-chamber plasma reactor. The existence of well-defined layers are demonstrated by TEM studies and the in-depth profiles of the compositions obtained by Auger electron spectroscopy. In some cases, growth imperfections can be observed in the thinner layers. The changes in optical absorption gap of a-Si: H as a function of its layer thickness in the superlattices are interpreted as quantum size effects. 相似文献
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The a-C:H and a-C:NX:H films were deposited onto silicon wafers using radio frequency (rf) plasma enhanced chemical vapor deposition (PECVD) and pulsed-dc glow discharge plasma CVD, respectively. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to characterize chemical nature and bond types of the films. The results demonstrated that the a-C:H film prepared by rf-CVD (rf C:H) has lower ID/IG ratio, indicating smaller sp2 cluster size in an amorphous carbon matrix. The nitrogen concentrations of 2.9 at.% and 7.9 at.% correspond to carbon nitride films prepared with rf and pulse power, respectively.Electrochemical corrosion performances of the carbon films were investigated by potentiodynamic polarization test. The electrolyte used in this work was a 0.89% NaCl solution. The corrosion test showed that the rf C:H film exhibited excellent anti-corrosion performance with a corrosion rate of 2 nA cm−2, while the carbon nitride films prepared by rf technique and pulse technique showed a corrosion rate of 6 nA cm−2 and 235 nA cm−2, respectively. It is reasonable to conclude that the smaller sp2 cluster size of rf C:H film restrained the electron transfer velocity and then avoids detriment from the exchange of electrons. 相似文献
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利用等离子体增强化学气相沉积技术制备了a-Si ∶H/SiO2多量子阱结构材料.对a-Si ∶H/SiO2多量子阱样品分别进行了3种不同的热处理,其中样品经1100 ℃高温退火可获得尺寸可控的nc-Si:H/SiO2量子点超晶格结构,其尺寸与非晶硅子层厚度相当.比较了a-Si ∶H/SiO2多量子阱材料与相同制备工艺条件下a-Si ∶H材料的吸收系数,在紫外/可见短波段前者的吸收系数明显增大,光学吸收边蓝移,说明该材料
关键词:
多量子阱
量子限制效应
光学吸收
能带结构 相似文献