Study of successive phase transitions of the Si(001)-Bi surface by RHEED

Successive phase transitions of the 2 × n surface structures have been observed on a Si(001) surface with Bi overlayer. These structures are formed with about one monolayer of Bi. The coverage of Bi slightly decreases with increasing temperature. Since these phase transitions are accompanied by the desorption of Bi, transitions are irreversible. The dependence of n on the temperature has been measured using reflection high-energy electron diffraction (RHEED). It is revealed that nth order spots move away from fundamental spots continuously over the range from 113 to 15 as the temperature is elevated from 530 K to 820 K.