Fundamental Research on Observation and Control of Hydrogen Related Reaction in Semiconductor Surfaces

用MDS和TDS研究了Cs和H在Si(100)2x1上的共吸附结构和电子态。Cs/H/Si体系和H/Cs/Si体系具有相同的TDS谱，表明两种体系中Si悬空键部分被H原子终止，在Cs覆盖度约0.4 ML以上形成的CsH被解离成H和Cs，在20℃左右发生H_2解吸。另一方面，H / Cs / Si体系的MDS光谱与Cs / H / Si体系的不同，即H / Cs / Si体系可以清晰地看到Cs-H键，而Cs / H / Si体系则没有。两种体系MDS谱的差异可以解释为：Cs / H / Si体系中，包含Cs-H键的所有氢原子都位于Cs层和Si衬底之间，而H / Cs / Si体系中，部分形成Cs-H键的氢原子位于衬底最外层。采用MDS、TDS和功函数测量等方法研究了Ba包覆Si（100）表面氢的化学吸附机理。对于1ML Ba/Si(100)，入射氢原子从氢暴露的初始阶段吸附在Ba原子的顶部。另一方面，对于4ML Ba/Si(100)，氢原子在氢暴露的早期扩散到Ba覆盖层中。最后，两个体系中的Ba原子都变成了ba_2。在4ML Ba/Si（100）上形成的Ba- h键比在1ML Ba/Si（100）上形成的键强。

The coadsorption structure and electronic state of Cs and H on Si(100)2x1 were investigated by means of MDS and TDS.The both systems of Cs/H/Si and H/Cs/Si have the same TDS profiles, which indicates that Si dangling bonds are partly terminated with H atoms in both systems and CsH formed at the Cs coverages above about 0.4 ML is dissociated into H and Cs, resulting in H_2 desorption at about 20。C.On the other hand, MDS spectra for the H / Cs / Si system differs from those for Cs / H / Si one, i.e., Cs-H bonds can be clearly seen in case of the H / Cs / Si systems, while not in case of the Cs / H / Si systems. The difference for MDS spectra between both systems can be explained as follows : in case of the Cs / H / Si systems, all hydrogen atoms including Cs-H bonds are located between Cs layer and Si substrate, while in case of the H / Cs / Si systems, some of the hydrogen atoms forming Cs-H bonds are on the outermost surface.The mechanism of hydrogen chemisorption on Ba precovered Si(100) surface was investigated by means of MDS, TDS and work function measurement. For 1ML Ba/Si(100), incident hydrogen atoms adsorb on top of Ba atoms from the initial stage of hydrogen exposure. On the other hand, for 4ML Ba/Si(100), hydrogen atoms diffuse into the Ba overlayers in the early stage of hydrogen exposure. Finally, all Ba atoms for both systems turn into BaH_2. The bond of Ba-H formed on 4ML Ba/Si(100) is stronger than that formed on 1ML Ba/Si(100).