Since the concept of a second phase of c(4x4)- reconstructed surface of GaAs (001) has been proposed by Ohtake et al. [1], an effort has arisen to study its structure both theoretically [2] and experimentally [3]. The new phase is characterized (in contrast to the old symmetric "three As-dimers" one) by a depleted stoichiometry and a special atomic geometry referred to as "mixed-dimers" structure. Both the c(4x4)-phases differ in MBE preparation conditions [4] but there still remains a controversy with the old results [5].
In this contribution we examine the MBE-prepared GaAs(100)-c(4x4) surfaces by angular resolved ultraviolet photoelectron spectroscopy with the synchrotron radiation and HeI line as the excitation sources. We prepared both the c(4x4) surface phases using As2 and As4 molecular beams [4]. We demonstrate that the photoelectron spectroscopy can distinguish
between both the phases. Appearance of intensive surface state of 0.5 eV below the top of the valence band is linked to the presence of one of the c(4x4) phases on the surface.
[1] A.Ohtake, J.Nakamura, S.Tsukamoto, N.Koguchi, A.Natori : Phys. Rev. Lett. 89
(2002), 206102
[2] E. Penev, P. Kratzer, M. Scheffler : Phys. Rev. Lett. 93 (2004), 146102 ;
C. Hogan, E. Placidi, and R. Del Sole, Phys. Rev. B 71 (2005), 041308(R)
[3] A. Nagashima, M. Tazima, A. Nishimura, Y. Takagi, J. Yoshino : Surface Sci. 493
(2001), 227; A.Nagashima, A.Nishimura, T.Kawakami, J.Yoshino: Surface Sci.
564 (2004), 218 ; O. Romanyuk, P.Jiøíèek, M.Cukr, I.Bartoš : Czech. J.Phys. 53
(2003), 49
[4] A. Ohtake, P. Kocán, J. Nakamura, A. Natori, and N. Koguchi : Phys. Rev. Lett.
92
(2004), 236105
[5] A.R.Avery, D.M.Holmes, J. Sudijono, T.S. Jones, B.A. Joyce : Surface Sci. 323
(1995), 91
|