SCANNING TUNNELING MICROSCOPY OF THERMALLY CLEANED INP SURFACES IN AN ARSENIC FLUX

Thermally cleaned InP surfaces in an arsenic flux have been observed using an ultra-high-vacuum scanning tunneling microscope (UHV-STM). The STM image of the reconstructed In-stabilized surface showed 1.6 nm periodic lines in the [110] direction. The width of these lines was about 0.8 nm, each line comprising two rows when the sample was heated at 510-degrees-C for about one minute in an arsenic flux. On the other hand, the lines were about 0.4 nm wide and comprised a single row when the sample was heated at a higher temperature for a longer time. This result suggest that the In-stabilized surface comprises one or two In-In dimers and missing dimers per 4 x 2 cell, and that the dimer density depends on the cleaning conditions. For samples annealed at 480-degrees-C in a vacuum of 10(-5) Pa for about ten minutes after cleaning, the surface image showed 4 x 2 In-stabilized domains and 2 x 4 As-stabilized domains. This structure is thought to be formed by a desorption of surface atoms during annealing.