Lateral Ordering of Self-Assembled Ge Islands

Abstract

AbstractTwo-dimensionally ordered arrays of Ge islands are realized by molecular beam epitaxy on vicinal Si(001) surfaces with regular ripples. Deposition of a 2.5 nm Si0.55Ge0.45/10 nm Si multilayer on vicinal Si(001) surfaces gives rise to the formation of regular ripples with a typical period of 100 nm, due to step-bunching. The ripples lead to the long-range line-up of the Ge islands along their direction, while the strong repulsive interaction between the dense Ge islands determines their relative arrangement on different step bunches of a ripple. The ordering pattern can be controlled by the Ge coverage as well as the direction of the ripples. The Ge islands show a narrow size distribution with the lateral size limited by the ripple periodIn contrast, when deposited directly on well-prepared biatomic-stepped vicinal Si(001) surfaces under the same growth conditions, only weak ordering of Ge islands along the step direction is achieved. No ordering of Ge islands has been observed, when a flat Si(001) surface is employed, where no obvious step-bunching occurs.The results promise efficient control on the position and size of self-assembled and selfordered Ge islands by the steps prepared on vicinal surfaces.