Stripe patterns formed by the thermal desorption of Ga atoms on Ga-terminated Si(111) surfaces

The Si(111)-7×7 area surrounded by the Si(111)-√3×√3R30°-Ga region has been observed by scanning tunneling microscopy during the thermal desorption of Ga atoms at ∼600 °C and after the desorption. The 7×7 area exhibits triangular and strip patterns on the nanometer scale for the Si(111) substrates tilting toward the [112̄] and [1̄1̄2] directions, respectively. This is because faulted halves of the 7×7 reconstruction are adjacent to the √3×√3-Ga area on the boundary between the 7×7 and √3×√3-Ga areas during Ga desorption. It has been found that strip patterns with nanometer-scale precision are formed on the Si(111) substrates tilting toward the [1̄1̄2] direction.