A low-temperature Langmuir evaporation regime was detected via the scanning tunnelling microscopy of (110) surfaces. It was characterized by the formation of positively charged anion mono-vacancies; even at room temperature. The vacancy formation was studied as a function of time on InP at temperatures of between 293 and 480K, and on GaAs at room temperature. In the case of InP, the maximum vacancy concentration was found at 435K. At this temperature, 1.2% of the P surface sites were vacant. At higher temperatures, the concentration decreased. The observations were explained in terms of a competition between P-vacancy plus adatom pair production, followed by P2 molecule formation and adsorption, and P out-diffusion from the bulk.

P.Ebert, M.Heinrich, M.Simon, K.Urban, M.G.Lagally: Physical Review B, 1995, 51[15], 9696-701