Evaluation of local electric fields on the reconstructed surfaces of semiconductor

利用二次谐波产生技术对洁净半导体表面的局部电场进行了测量。由强脉冲激光激发载流子引起的能带弯曲的变化表现为产生的SHG强度的变化超过了电场依赖的三阶非线性光学极化率。然而，它被发现，样品温度的升高也可以通过在我们的工作中澄清的温度依赖性的SHG的SHG强度的变化作出贡献。因此，观察到的SH强度对泵浦能量密度的依赖关系进行了分析，考虑到acacquisition的两个effects.In另一种尝试，以评估表面局部电场，从硅纳米晶体在低温等离子体增强化学气相沉积制备的多晶薄膜的倍频产生进行了研究。增加的SHG信号的晶粒尺寸的减小，解释由增加的局部电场。我们还研究了在室温下吸附银期间的SHG以及Si（111）-[square root]3x[square root]：在Si（111）~（-7）× ~（-7）表面上的二维吸附原子气体（2DAG）的密度决定了二次谐波的强度。Ag表面作为温度和银焊剂的函数。在室温下，银覆盖层的二次谐波的增加由表面等离子体共振解释，而在高温下，Si（111）-[square root]3x[square root]：3-Ag表面上形成的三维岛的作用也由我们的二次谐波检测方法证实。

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.