Evaluation of local electric fields on the reconstructed surfaces of semiconductor

通过二次谐波产生技术评估清洁半导体表面上的局部电场。强脉冲激光载流子激发引起的能带弯曲的变化表现为通过与电场相关的三阶非线性光学磁化率产生的倍频强度的变化。然而，通过我们工作中阐明的温度依赖性二次谐波发现，样品温度的增加也会导致二次谐波强度的变化。因此，通过考虑这两种效应，分析了观察到的SH强度对泵浦注量的依赖性。在评估表面局域电场的另一项尝试中，研究了通过低温等离子体增强化学气相沉积制备的多晶薄膜中硅纳米微晶的二次谐波产生SHG。微晶尺寸的减小导致二次谐波信号的增加，这可以通过局部电场的增加来解释。我们还研究了室温下银吸附过程中的二次谐波以及高温下Si(111)-7x7上Si(111)-【平方根】3x【平方根】:3-Ag表面的形成。发现二次谐波强度取决于Si(111)-【平方根】3x【平方根】3-Ag表面上二维吸附原子气体（2DAG）的密度，作为温度和银通量的函数。室温下银覆盖度的倍频增加可以通过表面等离子体共振来解释，而在高温下则显示了在 Si(111)-【平方根】3x【平方根】：3-Ag 旁边形成的 3D 岛的作用。Si(111)-7x7 表面上的局域电子自旋也通过我们的倍频检测方法得到了证明。

Local electric fields on the clean semiconductor surface is evaluated by means of second-harmonic generation technique. The changes in the band-bending induced by carrier excitation by an intense pulsed laser has manifested as a change in the generated SHG intensity througil the third order nonlinear optical susceptibility which is electric-field dependent. However, it is found that the sample temperature increase can also contribute to the change in the SHG intensity through the temperature dependent SHG clarified in our work. Thus, the observed dependence of the SH intensity on the pump fluence was analysed by taking into accont the both effects.In another attempt to evaluate the surface local electric field, the seeond-harmonic generation SHG from silicon nanocrystallites in polycrystalline films prepared by low-temperature plasma-enhanced chemical-vapor deposition has been studied. An increase in the SHG signal by decrease in the sizes of crystallites is, interpreted by the increased local electric filed. We also studied SHG during the adsorption of silver at room temperature as well as the formation of the Si(111)-【square root】3x【square root】 : 3-Ag surface at elevated temperatures on Si(111)-7x7.The SHG intensity is found to depend on the density of the two-dimensional adatom gas (2DAG) on the Si(111)-【square root】3x【square root】3-Ag surface as a function of temperature and silver flux. The increase of SHG with silver coverage at room temperature is interpreted by a surface plasmon resonance, while that at elevated temperatures show the role of 3D islands formed beside the Si(111)-【square root】3x【square root】 : 3-Ag.Local electron spins on the Si(111)-7x7 surface are also evidenced by our SHG detection method.