Basic studies on time-dependent surface photophysics and photochemistry of molecules adsorbed on Si(111)-7x7 by monochromatic soft X-ray

• Main Authors: Shing-KuenWang, 王興焜
• Other Authors: Ching-Rong Wen
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/61256594559440150671

博士 === 國立成功大學 === 物理學系碩博士班 === 100 === Monochromatic soft x-ray-induced reactions of CF2Cl2 adsorbed on Si(111)-7×7 at 30 K near the Si(2p) and F(1s) edges were studied by using three new surface analytic techniques proposed by our research group: (1) Continuous-time photoelectron spectroscopy (PES), (2) Photon-exposure-dependent photon-stimulated desorption (PSD), and (3) Continuous-time photon-stimulated desorption spectroscopy. During the continual irradiation of 98/120 eV photons, the continuous-time photoelectron spectra showed that the adsorbed molecules are dissociated. The photolysis cross sections were deduced from these spectra and found to be ~1.4×10−18 and ~8.0×10−18 cm2, respectively. The mechanisms responsible for the dissociation of CF2Cl2 molecules by the photons near the Si(2p) edge are dissociative electron attachment (DEA) and indirect dipolar dissociation (IDD). The fluorosilyl species produced on the surface during the photon irradiation is SiF. On the other hand, the continuous-time photon-stimulated desorption spectroscopy was employed to investigate the photoreactions of CF2Cl2 adsorbed on silicon surface near the F(1s) edge. The variation of spectral shapes in the sequential F+ PSD spectra shows the consumption of the CF2Cl2 molecules and the production of surface SiF species as a function of photon exposure. The F+ PSD spectrum and total electron yield (TEY) spectrum of solid CF2Cl2 were also measured in order to study the excitation mechanisms of F(1s) core level of the adsorbed CF2Cl2. The mechanisms responsible for the dissociations of the adsorbed molecules are DEA, IDD and direct excitation of F(1s) core level. The photolysis cross section of the CF2Cl2 molecules by photons with varying energy (681–704 eV) is deduced from the sequential F+ PSD spectra and found to be ~6.0×10−18 cm2.