共查询到19条相似文献,搜索用时 125 毫秒
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用脉冲激光沉积(PLD)的方法在多孔硅衬底上沉积了ZnS薄膜,并在室温下研究了ZnS/PS异质结的结构、光学和电学性质。X射线衍射仪(XRD)测量结果表明.制备的ZnS薄膜在28.5°附近有一较强的衍射峰,对应于β-ZnS(111)晶向,说明薄膜沿该方向高度择优取向生长。ZnS/PS复合体系的光致发光谱表明,ZnS的发光与PS的发光叠加在一起,在可见光区形成一个450-700nm较宽的光致发光谱带。呈现较强的白光发射。对ZnS/PS异质结I-V,特性曲线的测量结果表明,异质结呈现出与普通二极管相似的整流特性。在正向偏置下,电流密度较大.电压降较低;在反向偏置下,电流密度接近于零。异质结的理想因子的值为77。 相似文献
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采用基于原子球近似下线性Mufin-Tin轨道(LMTO-ASA)的平均键能计算方法,研究了以ZnSxSe1-x为衬底,沿(001)方向外延生长的应变层异质结ZnS/ZnSe、ZnS/ZnSxSe1-x和ZnSe/ZnSxSe1-x的价带带阶值ΔEv(x).研究表明,ΔEv(x)值随衬底合金组分x单调变化。且两者的关系是非线性的。在此计算结果与其它理论计算和实验结果符合较好。 相似文献
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利用应变SiGe/Si异质pn结电容-电压(C-V)特性确定SiGe禁带宽度的技术.该技术根据SiGe/Si异质pn结C-V实验曲线,计算出 pn结接触电势差,并得到SiGe/Si的价带偏移量和导带偏移量,进而求得SiGe禁带宽度.该技术测试方法简便,其过程物理意义清晰,既适用于分立的SiGe/Si异质pn结,也可直接分析SiGe/Si异质结器件中的SiGe 禁带宽度.实验结果与理论计算及其他相关文献报道的结果符合较好.
关键词:
SiGe/Si
异质pn结
C-V
禁带宽度 相似文献
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用linear mufin tin orbital能带方法,计算Si衬底上(ZnS)n/(ZnSe)n(001)超晶格的能带结构,计算中采用外加调整势进行带隙修正.在得到较准确的能带结构和波函数的基础上,计算该超晶格系统的光学介电函数虚部ε2(ω).结果表明,该超晶格系统的光学性质结合了ZnS和ZnSe体材料光学性质的特点,在相当宽的能量范围内有较好的光谱响应.并且该超晶格系统是直接带隙材料,在光电器件应用中有很大潜力.
关键词: 相似文献
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在200 ℃下利用激光沉积技术分别在玻璃和Si(100)上沉积制备了ZnS薄膜,并在300,400,500 ℃下退火1 h。用X射线衍射(XRD)仪、紫外/可见光/近红外分光光度计、台阶仪和原子力显微镜(AFM)分别对不同衬底上样品的特征进行了观察。结果表明,玻璃上的ZnS薄膜只在28.5°附近存在着(111)方向的高度取向生长。在可见光范围内透射率为60%~90%。计算显示薄膜的光学带隙在3.46~3.53 eV之间,其小于体材料带隙的原因在于硫元素的缺失。根据光学带隙判断薄膜是单晶立方结构的β-ZnS。Si(100)上生长的是多晶ZnS薄膜:500 ℃下退火后,表面也比未退火表面更加平整致密,变化规律与ZnS/glass的类似。说明高温下退火可以有效地促进晶粒的结合并改善薄膜质量。 相似文献
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The electronic band structures of Si and Ge low-dimensional nanostructure such as nanofilms and nanowires have been calculated using first principles based on density functional theory (DFT) with the generalized gradient approximation (GGA). The calculation results show that a direct band gap can be obtained from Si orientation [100] or in Ge orientation [111] confined low dimensional nanostructure. However, an indirect band gap is still kept in the Si orientation [111] or in the Ge orientation [110] confined low dimensional nanostructure. The calculation results are interesting and the transition mechanism from indirect to direct band gap in low dimensional nanostructures is given in the physical structures model. 相似文献
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In nanomaterials, optical anisotropies reveal a fundamental relationship between structural and optical properties, in which directional optical properties can be exploited to enhance the performance of optoelectronic devices. First principles calculation based on density functional theory(DFT) with the generalized gradient approximation(GGA) are carried out to investigate the energy band gap structure on silicon(Si) and germanium(Ge) nanofilms. Simulation results show that the band gaps in Si(100) and Ge(111) nanofilms become the direct-gap structure in the thickness range less than 7.64 nm and7.25 nm respectively, but the band gaps of Si(111) and Ge(110) nanofilms still keep in an indirect-gap structure and are independent on film thickness, and the band gaps of Si(110) and Ge(100) nanofilms could be transferred into the direct-gap structure in nanofilms with smaller thickness. It is amazing that the band gaps of Si~((1-x)/2)Ge~xSi~((1-x)/2)sandwich structure become the direct-gap structure in a certain area whether(111) or(100) surface. The band structure change of Si and Ge thin films in three orientations is not the same and the physical mechanism is very interesting, where the changes of the band gaps on the Si and Ge nanofilms follow the quantum confinement effects. 相似文献
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Reactions on Cl-adsorbed Si(111) and Si(100) surfaces—(Cl/Si(111) and Cl/Si(100))—under heating in ultrahigh vacuum (UHV) and in a Cl2 atmosphere were studied. Auger electron spectroscopy (AES) and low-energy electron energy loss spectroscopy (LEELS) were used for examination of surface changes. Heating in UHV at 820°C for 30 s successfully removed almost all Cl atoms, both on Cl/Si(111) and Cl/Si(100). Variance in LEELS spectra shows that decomposition of SiClx (x > 1), a small amount of which was present on Cl/Si(111), occurs under heating on Si(111) both in UHV and in Cl2 and desorbs reaction products, leaving the Si---Cl bonds on the surfaces. Such Si---Cl bonds specific to those on Cl/Si(111) are formed also on Cl/Si(100) heated in C12 at 820°C. On Cl/Si(100) heated in C12, there are various surface changes: relaxation of the 2 × 1 structure remaining on the Cl/Si(100), desorption of reaction products, and formation of Si---Cl bonds specific to those on Cl/Si(111). The Si---Cl bonds, both on Cl/Si(111) and Cl/Si(100), decomposed under longer heating and under heating at higher temperatures in UHV. 相似文献
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Ballabio G Profeta G de Gironcoli S Scandolo S Santoro GE Tosatti E 《Physical review letters》2002,89(12):126803
Distortions of the sqrt[3]x sqrt[3] Sn/Ge(111) and Sn/Si(111) surfaces are shown to reflect a disproportionation of an integer pseudocharge, Q, related to the surface band occupancy. A novel understanding of the (3 x 3)-1U ("1 up, 2 down") and 2U ("2 up, 1 down") distortions of Sn/Ge(111) is obtained by a theoretical study of the phase diagram under strain. Positive strain keeps the unstrained value Q=3 but removes distortions. Negative strain attracts pseudocharge from the valence band causing first a (3 x 3)-2U distortion (Q=4) on both Sn/Ge and Sn/Si, and eventually a (sqrt[3] x sqrt[3])-3U ("all up") state with Q=6. The possibility of a fluctuating phase in unstrained Sn/Si(111) is discussed. 相似文献
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External differential reflection measurements were carried out on clean Si(100) and (110) surfaces in the photon energy range of 1.0 to 3.0 eV at 300 and 80 K. The results for Si(100) at 300 K showed two peaks in the joint density of states curve, which sharpened at 80 K. One peak at 3.0 ± 0.2 eV can be attributed to optical transitions from a filled surface states band near the top of the valence band to empty bulk conduction band levels. The other peak at 1.60 ± 0.05 eV may be attributed to transitions to an empty surface states band in the energy gap. This result favours the asymmetric dimer model for the Si(100) surface. For the (110) surface at 300 K only one peak was found at 3.0 ± 0.2 eV. At 80 K the peak height diminished by a factor of two. Oxygen adsorption in the submonolayer region on the clean Si(100) surface appeared to proceed in a similar way as on the Si(111) 7 × 7 surface. For the Si(110) surface the kinetics of the adsorption process at 80 K deviated clearly. The binding state of oxygen on this surface at 80 K appeared to be different from that on the same surface at 300 K. 相似文献
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T. Kan K. Mitsukawa T. Ueyama M. Takada T. Yasue T. Koshikawa 《Surface science》2000,460(1-3):214-222
The secondary alkali ion yield vs. the work function change (Δφ) of Na, K and Cs/Si(100) and Si(111) was measured to discuss the details of secondary ion emission processes. In the case of alkali/metal systems, the secondary ion emission is explained by the electron tunneling model. In this model, the ionization of the ejected atom occurs as a result of electron resonant tunneling through the potential barrier separating an atom and a metal, and the secondary ion yield depends on exponentially the work function change of metal surface. For alkali/Si(100) systems, the secondary ion emission processes are explained in terms of the electron tunneling model since the secondary alkali ion yield vs. the work function change (Δφ) follows the exponential manner. However, it is not easy to apply the simple electron tunneling model to our experimental results for alkali/Si(111) systems. There is the essential difference in surface structures between Si(100) and Si(111). Therefore, it is suggested that the local electronic environment around the adsorbates might be taken into consideration for alkali/Si(111) systems. 相似文献