利用掃描穿隧式顯微鏡研究鐵三矽逐層成長在砷化鎵(001)及(111)A之表面形貌演化

Abstract

High-quality hetero-junction comprises magnetic materials and semiconductors plays an important role in fabrication of spintronic devices which require high efficiency of spin injection into semiconductor for manipulations. Fe3Si/GaAs provides such an optimized hetero-structure in which the lattice is nearly matched and Fe3Si was found to have a spin polarization of 43%. In this work Fe3Si has been epitaxially grown on both GaAs (001)-4×6 and GaAs (111)A-2×2 by MBE and the in-situ scanning tunneling microscopy (STM) was utilized to characterize the surface morphology. Verified by RHEED, high-quality GaAs (001)-4×6 and (111)A-2×2 surfaces were obtained after the GaAs epi-layer growth. During the deposition of Fe3Si, the surface morphology was systematically studied by STM thickness-dependently. Different growth modes were observed between the Fe3Si films grown on the two surfaces with the same growth parameters. The STM investigation on Fe3Si/GaAs(001)-4x6 reveals a surface morphology evolution which is qualitatively consistent with a previous theoretical simulation; namely, the initial growth follows the Volmer-Weber (VW) mode up to 36.7 A (13 ML), where the grains coalesced completely. Then, the two-dimensional layer-by-layer growth prevails. On the growth of Fe3Si/GaAs(111)A-2×2, the observed surface morphology follows the similar trend with the VW mode on the initial growth. However, a nearly layer-by-layer 2-dimensional growth mode was achieved in a much thinner film of 16.3 A. Also the theoretical surface energy calculation supported the different growth mode occur in (001) and (111) plane.