Study on Dynamic Processes of Adsorption and Desorption by means of Time-Resolved Reflectance Spectroscopy

用实时多道反射光谱研究了气体在固体表面的吸附和脱附的动态过程，根据光谱结构确定了气体的吸附状态：(1)在氮气在W(001)表面吸附的情况下，3.8 eV和2.1 eV的光谱结构分别与β_2和β_1态相关。β_1态的发展首先是通过在2.1 eV的结构增强而得到的，氮素对体相的穿透是可能的解释。(2)室温下氯在Si(111)面上吸附的新发现如下：1)主要过程是原子的吸附而不迁移。对悬挂键的初始粘着概率和背向键的初始断裂概率分别为0.48和0.14。2)重掺杂的硅单晶的初始断裂概率和断裂背向键的总数较大。3)在3.6 eV附近发现了SiCI的体态到反键态之间的光学跃迁结构。(3)在740K下对氯饱和的Si(111)表面进行热处理，形成了覆盖有*SiCI的静止原子表面。在880-940K，氯从静止原子表面脱附的新发现如下：1)主要过程是背键的恢复。活化能为2.7 eV，相当于反应的势垒能，SiCl+SiCl2+Si2)只有在脱附初期才能观察到悬挂键的恢复。

Dynamic processes of adsorption and desorption of gases on solid state surfaces have been studied by real-time multichannel reflectance spectroscopy, in which adsorption states are specified from spectral structures.(1) In the case of nitrogen adsorption on W(001) surface, spectral structures at 3.8 and 2.1 eV are found to be correlated with the beta_2 and beta_1 states, respectively. Development of the beta_1 state is firstly obtained by the enhancement of the structure at 2.1eV.Penetration of nitrogens into the bulk is a possible explanation for this state(2) New findings about chlorine adsorption on Si(111) at room temperature are as follows.1) Main process is found to be adsorption of atoms without migration. Initial sticking probability to dangling bonds and initial breaking probability of back bonds are determined as 0.48 and 0.14, respectively.2) The initial breaking probability and the total number of the broken back bonds are larger for heavyly doped silicon. Holes probably weaken the back bonds.3) A structure originating from optical transitions between the bulk states to the antibonding states of SiCI is found aroud 3.6eV.(3) A rest-atom surface covered with * SiCI is formed by annealing the chlorine-saturated Si(111) surface at 740K.New findings about chlorine desorption from the rest-atom surface at 880-940K are as follows.1) Main process is found to be restoration of back bonds. Activation energy is determined as 2.7 eV and this corresponds to the barrier energy for the reaction, SiCl +SiCl *** SiCI_2 + Si.2) Restoration of dangling bonds are observed only at the initial stage of the desorption.It has been shown that dynamic processes of adsorption and desorption can be real-time studied by specifying chemical bonds from the structures of reflectance spectra.