First-principles molecular dynamics study of NO adsorption on Si(001)

Si(001)에 흡착되는 NO에 대한 제일원리 분자동역학 연구

  • Jeong Sukmin (Department of Physics, Chonbuk National University)
  • Published : 2005.06.01

Abstract

NO adsorption can be used in synthesizing oxynitride thin films which have potential application in nanodevices. However, it is very difficult to understand the oxynitridation Process since too many factors are involved in it. In this paper, we present our first-principles molecular dynamics calculation of the NO molecule adsorption on the Si(001) surface as the initial stage of the oxynitridation process. The previous first-principles calculation has argued the NO molecule is dissociated with a very small activation barrier, 0.07eV, which acutally corresponds to 1.60eV considering thermodynamics. This is in clear contrast to the observation that NO is dissociated at temperatures as low as 20K From extensive searches of NO on the Si(001) surface, we have found the new dissociation processes that have the much lower activation energies, less than 0.01 eV. We also present the dissociation and penetration processes with the corresponding activation energies and discuss their experimental implications.

제일원리 분자동역학 방법을 이용하여 Si(001) 표면에 NO 분자 흡착을 연구하였다. NO 분자가 Si(001)의 dimer축과 나란히 흡착될 경우에 50K에서도 분해가 일어났다. 이를 에너지 장벽으로 환산해 보면 0.006eV로서 거의 무시해도 좋을 정도이다 만일 NO 분자가 표면에 수직으로 들어오면 이웃에 있는 dimer에 걸쳐서 분해가 일어났다. 이 경우는 에너지 장벽은 0.08eV 정도였으며 여전히 낮은 수준이다. 분해가 된 산소분자는 dimer와 기판 사이의 backbend로 파고들어서 (에너지 장벽 0.007eV) 안정된 구조를 만들었다. 또 dimer에 나란히 흡착된 분자 상태의 경우는 N=Si_3$를 만들기도 하는데 속전자준위분광학(core level spectroscopy) 실험 결과와 일치한다.

Keywords

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