Theoretical study of GeH4 dissociative adsorption onto Ge(100) by using different incident angles

• Main Authors: Yuh-Hwan Ger, 葛玉環
• Other Authors: Jyh-Shing Lin
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/43690525271400900995

碩士 === 淡江大學 === 化學學系碩士班 === 97 === Using density functional theory (DFT) with ultrasoft pseudotentials and plane wave basis to calculate the reaction of GeH4 dissociative adsorption onto Ge(100). Through the analysis of structure, energy and density of state (DOS) to investigate the following three reaction path: single dimer mode (SDM), adjacent two dimers mode (ATDM) and nearest neighboring dimers in row mode (NNDIRM). In NNDIRM, choosing incident angles as 10˚, 20˚ and 30˚. To define the 0˚ angle that GeH4 impact the surface, choosing the direction from Ge-H bond within GeH4 to dangling bond to be 0˚. To define the incident angle, choosing the normal vector of the plane formed with the dangling bond of buckled-down Ge as the rotation axis, and the buckled-down Ge as rotation center. Using partial structural constrain path minimization (PSCPM) to find the reaction path and the information of transition state and to probe into the relation between activation energy, transition state structure and the different of incident angle and reaction path. Through DOS analysis to understand the variation of DOS of initial state (IS), transition state (TS) and final state (FS). After calculation, trend of activation energy: NNDIRM_10° > NNDIRM_20°> ATDM > NNDIRM_ 30° > SDM. The same result showed in the trend of bond length of Ge-H bond within precursor in transition state and buckled -up Ge with Ge in precursor. The better reactivity happened in SDM which has smaller incident angle. As Boltzmann distribution law, to increase the reaction probability in reaction path of higher activation energy, the more incident kinetic energy and higher substrate temperature is needed in experiment so that Ge-H bond within precursor could be distorted more and elongation of Ge=Ge dimmer could be larger, respectively. In the research, we found NNDIRM_10°, NNDIRM_20°and ATDM which have higher activation energy could make structure change more in transition state. As a result, the increasing of incident kinetic energy and substrate temperature will also increase reaction probability of those reaction paths.