Investigation of Si(001) stable surfaces in alternating current heating

Abstract

The topography of a Si(001) vicinal surface is investigated using reflection electron microscopy (REM) during alternating current (AC) heating of the surface in ultra-high vacuum. The normal direction of the surface is slightly tilted from the [001] direction at θx or θy on the x or y axis (they are orthogonal 〈110〉 directions in the Si(001) surface), and the average widths of the terraces (a or b in x or y axis) are determined by θx or θy; the direction perpendicular to the incidence electron beam on the surface is selected as the x (horizontal) axis in each REM image. Alternating current heating changes each initial surface from stable to double-domain (DD), in which 2×1 and 1×2 terraces are arranged regularly with approximately equal width, at its transition temperature Tc; the dimer rows are parallel to the x or y axis in the 1×2 or 2×1 terraces. There are two types of stable surfaces in the vicinal surface. At temperatures below its Tc, the surface with horizontally (vertically) long terraces, where b<a (b>a), changes to a 2×1 (1×2) surface with wide 2×1 (1×2) and narrow 1×2 (2×1) terraces. The terrace, the short side of which is parallel to its dimer row direction, grows to create a stable surface by thermal diffusion of Si atoms at temperatures below Tc. During AC heating, thermal diffusion plays a key role in analyzing the kinetics of the atoms on the surface because the thermal effect acts as the driving force for the atoms that have not yet evaporated from the surface. Then, by evaporating atoms from the vicinal surface, AC heating creates a DD surface at temperatures between its Tc and 1100°C and a rugged surface consisting of small 2×1 and 1×2 terraces at temperatures above 1100°C.