화학공학소재연구정보센터
Journal of Vacuum Science & Technology A, Vol.17, No.4, 1596-1601, 1999
Intermediate structures appearing in the phase transition of Si(111)-7 x 7 to (root 3x root 3)R30 degrees induced by HBO2 molecular irradiation
We have investigated the breakdown process of the 7x7 structure during its transition to the (root 3X root 3)R30 degrees phase induced by HBO2 irradiation. The 7x7 structure was destroyed over the wide area before the nucleation of the (root 3X root 3)R30 degrees phase. Even when the (root 3X root 3)R30 degrees structure nucleated in the disordered area, disordered structure existed between the domains of the 7x7 and (root 3x root 3)R30 degrees structural phases. The observed results are completely different from the (root 3x root 3)R30 degrees formation processes induced by other group III atoms, where (root 3X root 3)R30 degrees phases are formed as adjacent to the 7x7 structural domains. The surface B atom concentration in the 7x7, disordered, and (root 3x root 3)R30 degrees regions were estimated to be about one, three, and six per 7x7 unit cell. The disordered structure remained on the surface even after annealing the sample at 750 and 900 degrees C. And the B concentration in the disordered region did not change. These results indicate that the disordered structure is an intrinsic nature of the B-induced reconstruction, and suggest the existence of the relationship between the B atom concentration and the stability of the 7x7 structure.