Research of hydrogen reaction dynamics at semiconductor surfaces by multiple-internal-reflection infrared spectroscopy

本研究的目的是利用多重内反射几何中的红外吸收光谱来阐明氢原子在半导体表面的行为。本研究的主要结论如下：1.氢在硅表面的脱附强烈地受表面的微观粗糙度的影响。我们发现，在Si（100）（2x 1）表面的台阶和缺陷处的氢脱附活化能比二聚体处的低.我们证实，即使在超高真空条件下，水分子也容易吸附在清洁的Si表面上。我们发现，所谓的“C-缺陷”，已观察到的STM图像中的“干净”的Si表面，是由于吸附到Si表面上的水。我们还提出了水在Si（100）（2x 1）上的解离吸附模型.本文研究了SiH_4在Si（001）（2x 1）面上的吸附。通过比较红外光谱数据和密度泛函簇计算，我们发现在低氢覆盖度下，硅烷分子解离吸附在Si（001）（2x 1）上，在相邻的二聚体和单氢化物物种之间的桥位上形成一个二氢化物（SiH_2）.我们认为，在高氢覆盖率下，硅烷吸附到一个单一的二聚体上，生成单氢化物和硅烷基（-SiH_3）。我们还证明了最初由硅烷吸附产生的二氢化物物种即使在室温下也会分解为一氢化物物种。本文研究了苯在Si（001）（2x 1）表面的吸附。我们发现，吸附过程强烈依赖于苯的表面覆盖度：在低覆盖度，苯分子分子吸附在两个相邻的二聚体之间的桥位，并在高覆盖度，分子优先粘到一个单一的二聚体。

The aim of this research is to elucidate the behavior of hydrogen atoms at semiconductor surfaces using infrared absorption spectroscopy in the multiple internal reflection geometry. The main conclusions of this research are as follows :1. The desorption of hydrogen on Si surface is strongly influenced by the microscopic roughness of the surface. We found that the hydrogen desorption at step and defects sites has a lower activation energy than that at dimer sites of the Si(100)(2x1) surface.2. We confirmed that the water molecules readily adsorbs on the clean Si surface even under ultra-high vacuum conditions. We found that the so-called "C-defects" that have been observed in STM images of the "clean" Si surface, is due to the adsorption of water onto the Si surface. We also proposed a model for the dissociative adsorption of water on Si(100)(2x1).3. We have investigated the adsorption of SiH_4 on the Si(001)(2x1) surface. Comparing infrared data with the density functional cluster calculation, we showed that at low hydrogen coverage the silane molecule dissociatively adsorbs on Si(001)(2x1) to populate a dihydride (SiH_2) at the bridge site between two adjacent dimers and monohydride species. We suggested that at high hydrogen coverage, silane adsorbs onto a single dimer to generate monohydride and sylil groups (-SiH_3). We also demonstrated that the dihydride species that was initially generated by silane adsorption, decomposes to monohydride species even at room temperature.4. We have investigated the adsorption of benzene on the Si(001)(2x1) surface. We showed that the adsorption process strongly depends on the surface coverage of benzene : At low coverage, the benzene molecule molecularly adsorbs at the bridge site between two adjacent dimmers, and at high coverage, the molecules preferentially sticks onto a single dimer.