Low-energy electron diffraction study of the phase transition of Si(001) surface below 40 K.

The phase transition of Si(001) surface below 40 K was studied by low-energy electron diffraction (LEED). The temperature dependence of the intensities and widths of the quarter order diffraction spots and LEED intensity versus electron energy curves (I-V curves) were obtained in the temperature region from 20 to 300 K. While the spot intensities of the quarter order spots decrease and the widths broaden, the I-V curves do not change so much below 40 K. This clearly shows that a phase transition occurs from an ordered phase above 40 K to a disordered phase below 40 K.