Observation of Electron-Wave Diffraction with Scanning Probe based on Reciprocity Principle

点击翻译按钮获取中文摘要

In order to observe diffraction phenomena of hot electrons in solids using scanning probes based on the reciprocity principle, theoretical simulations have been performed to find required current sensitivity pico-ampere(pA) level. Experimentally, the Ballistic Electron Emission Microscopy(BEEM) technique has been improved to obtain uniform current signal in pA level over sample surfaces.Three-dimensional Schroedinger equation was numerically analyzed using the finite-difference time-domain(FDTD) method with absorbing boundaries. Appling this analysis to phase-shifter structures, followings have been clarified ; conditions of the energy width of the injected electron to obtain the diffraction fringe with pA variation, conditions for spherical wave generation in semiconductors. It has been found that the diffraction caused by constriction of the electron beam reduces the transmission efficiency by factor 5. We have proposed to take this diffraction effect into account in BEEM analyses.A … More BEEM apparatus has been constructed based on existing scanning tunnel microscope by installing the control system bought newly. Using GaAs/Au Schottky samples, current sensitivity of pA has been achieved by eliminating noises. Strategy for the probe scanning has been developed to obtain two-dimensional image of BEEM signal ; the probe stays at one point for a period required to eliminate the noise.In order to obtain uniform BEEM signal over the surface, intact and clean Schottky interfaces have been created by devising a novel self-alignment process. Finally it has been revealed that grain formations in 10 nm-thick Au films limit uniformity in BEEM signal in the sample surface.In summary, we have clarified possibilities and conditions to observe the electron wave diffraction in the solid by probes based on the reciprocity principle and established the BEEM technique as foundations to achieve the observation. We have approached to the target leaving a final step to form the conductive surface layer by epitaxy. Less