Etching Kinetics of Si(111) Surface by Selenium Molecular Beam

Using in situ ultrahigh vacuum reflection electron microscopy, three modes of the etching kinetics of the Si(111) surface with a selenium molecular beam are revealed. In the low temperature region ( $$\lesssim$$ 650 $${}^{\circ}$$ C depending on the Se deposition rate), the etching kinetics is limited by the energy of formation and desorption of SiSe $${}_{2}$$ molecules and the surface is completely covered by an impurity-induced silicon selenide phase ‘‘1 $$\times$$ 1’’-Se. In the temperature range $${\sim}700{-}1100^{\circ}$$ C the etching rate is limited by the amount of Se deposition flow and does not depend on the temperature, surface structure, and etching mechanism (step-layer or two dimensional-island). At high temperatures ( $${\gtrsim}1150^{\circ}$$ C), the sublimation of Si atoms begins to make the main contribution to the silicon flux from the surface. A theoretical model describing the temperature and kinetics of transitions between etching modes is formulated.