超純水のみによる電気化学的加工法の研究 陰極Ｓｉ（００１）表面における除去加工現象の第一原理分子動力学シミュレーション

Abstract

In order to reveal the mechanism of the electrochemical processes of cathode surface in ultrapure water, first-principles molecular-dynamics simulations of hydrogen-terminated Si(001) surfaces interacting with H atoms and H20 molecules were carried out on the basis of the Kohn-Sham local-density-functional formalism. A plane-wave basis set was used, and the cut-off energy is 327eV(24Ry). A norm-conserving pseudopotential was also used. We adopt the standard molecular-dynamics method for the optimization of the ionic system and the preconditioned conjugate-gradient (CG) method for the quenching procedure of the electronic degrees of freedom. We determined the optimized atomic configurations and electronic distributions for H and H2O chemisorbed hydrogen-terminated Si(001) surfaces. It was confirmed that an H atom reacts with H20 molecules on the hydrogen-terminated Si(001) surface to produce an OH molecule, and chemisorption of two OH molecules to the hydrogen-terminated Si(001) surface atom breaks the back-bonds and the Si surface atom is etched with forming an SiH2(OH)2 molecule. From these simulation results, we deduced that the electrochemical machining of Si(001) cathode surface in ultrapure water is possible.