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

利用实时多通道反射光谱技术研究了气体在固体表面吸附和脱附的动态过程，从光谱结构中确定吸附状态。(1)在氮吸附于W（001）表面的情况下，发现3.8和2.1eV处的光谱结构分别与β_2和β_1态相关。在2.1eV下，由于结构的增强，首次得到了β_1态的发展。氮的渗入是这种状态的一种可能的解释。（2）室温下氯在Si（111）上吸附的新发现如下：1）主要过程是原子的吸附，没有迁移。2）重掺杂硅的初始断裂概率和断裂的背键总数都较大。3）在3.6eV附近发现了一个由SiCl的体态到反键态的光学跃迁产生的结构。(3)在880- 940 K温度范围内，氯从Si（111）表面的脱附过程主要是背键的恢复。活化能确定为2.7 eV，这对应于反应SiCl +SiCl * SiCl_2 + Si.2的势垒能。）仅在脱附的初始阶段观察到悬挂键的恢复。已经表明，可以通过从反射光谱的结构中指定化学键来实时研究吸附和脱附的动态过程。

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.