Surface microchemistry associated with ion bombardment on Ni(111)

• Main Authors: Yang, Jiun-Chan, 楊竣程
• Other Authors: Che-Chen Chang
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/97341748106259940701

碩士 === 國立臺灣大學 === 化學系研究所 === 85 === The influence of ion bombardment on surface reaction is examined using the rea ction of CO with the Ni(111) surface as a model system. Thermal desorption stu dies show that a large amount of residual CO may be deposited on the surface d uring ion bombardment. Irradiation of energetic ions on Ni(111) can cause chan ges of the surface structure, enhance the surface reactivity , increase the st icking probability, and promote the formation of a new adsorption state. The a ctivation energy for CO desorption from this new state is estimated to decreas e by a magnitude of 6－7 kcal/mole as the sample evolves from a smooth to a da maged state. Comparing with results from other ion bombardment studies show th at, when the temperature of bombarded surface was increased to within the rang e of characteristic temperature(620K－700K) of the sample, the topographic transition will cause decrease of sticking probability and of C－Ni binding energy. The diffusion of carbon and oxygen atoms into the bulk is also observed by using SXPS. Isotopic studies using C18O as absorbate show that CO does not dissociate when absorbed on the bombarded surface. Instead, the atomic carbon and oxygen may be formed due to the disruption of the C－O bond by ion bombardment. The dynamic exchange of the reaction site between adsorbed C16O and C18O is also observed.