Study on the magnetic and the structural properties of Co/InP and Co/Sb/InP systems

Abstract

Ferromagnetic metal/semiconductor (FM/SC) heterostructures have attracted great interest because their novel magnetic and structural properties provide fundamental studies in magnetism and offer possibilities for spintronic applications. In FM/SC systems, it is significant to understand the physical and the chemical properties of the interface regions between the ferromagnetic metal and the semiconductor because these properties play critical roles in determining the characteristics of spintronic devices, such as the efficiency of spin injection through a FM/SC interface. In this thesis, the magnetic and the structural properties in the interface of Co/InP system have been investigated. We have investigated magnetic properties of Co film deposited on InP(2×4) reconstructed surface using in situ surface magneto-optical Kerr effects (SMOKE) measurement system. InP(2×4) reconstructed surface, obtained by several cycles of ion bombardment and annealing (IBA) process, was confirmed by reflection high energy electron diffraction (RHEED) and scanning tunneling microscopy (STM) measurements. Co film grown on InP(2×4) reconstructed surface shows three distinguishable thickness regions which have different magnetic properties, depending on Co film thickness. In the Co film thickness region smaller than 14 $\AA$, no SMOKE signal was detected. In the thickness region between 16 $\AA$ and 30 $\AA$, both longitudinal and polar Kerr hysteresis loops were observed. In the film thickness larger than 32 $\AA$, only longitudinal SMOKE signal without polar signal was detected. To understand the elastic properties of Co/InP, we have investigated the stress evolution of a Co/InP(001) by a highly sensitive optical deflection-detecting system in ultra high vacuum (UHV) chamber. Stress results are analyzed and discussed by correlating to the growth morphology by STM measurements and high resolution transmission electron microscopy (HRTEM). Abrupt compressive stress, which is sho...