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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。
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F. Falk G. Mollekopf H. Stafast 《Applied Physics A: Materials Science & Processing》1998,67(5):507-512
4 and disilane Si2H6 induced by continuous wave CO2 laser irradiation has been investigated under the conditions of chemical vapor deposition (CVD) of amorphous hydrogenated
silicon a-Si:H. At the very position of depositing the thin film the stationary chemical composition of the processing gas
is probed in situ by an effusive molecular beam which passes through a differential pumping stage into a quadrupole mass spectrometer
(QMS).
With SiH4 as educt and SF6 as a sensitizer, SiH4 and Si2H6 are found in the processing gas while Si3H8 or higher silanes are lacking. Si2H6 and SF6 lead to SiH4, Si2H6, and Si3H8, but higher silanes are missing. The experimentally determined composition of the processing gas is semi-quantitatively reproduced
by model calculations based on the assumption of stationary local equilibrium conditions and applying thermodynamic and spectroscopic
data (molecular statistics).
The mass balance of the processing gas entering and leaving the CVD chamber states an atomic ratio Si:H of 1:2 for the gas
phase species forming the solid deposit on the reactor walls. This finding together with theoretical considerations indicates
the intermediate Si2H4 to be the dominating gas phase species forming the a-Si:H thin films.
Received: 17 July 1998/Accepted: 20 July 1998 相似文献
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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