22.18 Methods of constructing stimulus-response curves for motor evoked potentials induced by transcranial magnetic stimulation

Abstract

Surface supersaturation in microchannel epitaxy (MCE) by liquid-phase epitaxy is a key parameter to control the width-to-thickness ratio (aspect ratio), which determines the dimensions of the dislocation-free area. The interstep distance of a spiral step at a screw-dislocation and curve-fitting of screw-like steps at stacking faults (SFs) are employed to estimate the surface supersaturation during MCE. The dependence of the vertical growth rate on the surface supersaturation was experimentally studied in GaAs(001) MCE. As a result, 2D nucleation at SFs was determined to act as a strong step source, which is stronger than a typical spiral step at a screw-dislocation over a wide range of surface supersaturation. Precise control of the surface supersaturation is important to optimize the growth conditions for MCE. An MCE layer with a large aspect ratio can thus be reproducibly obtained using appropriately controlled surface supersaturation.