Observation and Manipulation of Semiconductor Surface Microstructure in Solution

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1. Development of Laser Spot Scanning Microscope (LSSM).Novel LSSM system for in-situ measurements has been developed. In order to improve the efficiency of the measurements, two personal computers are used in the system. Control of the system and data collection are carried out by a 8-bit machine and data are transferred and analyzed by a 32-bit machine. This system was applied to study the photo electrochemical processes at semiconductor/electrolyte interfaces. Theoretical analysis of the system was also carried out and effect of diffusion length of minority carrier in the semiconductor and rate constant at semiconductor electrode surface on resolution of the microscope were determined.2. Development of Scanning Tunneling Microscope (STM).Commercially available STM was converted to an in-situ, electrochemical STM system which can monitor and record the surface morphology change of metal and semiconductor electrodes with nm resolution. Cu deposition on Pt, photoanodic dissolution of semiconductor and surface structure change caused bypotential cycles were investigated. As an application of STM, nosel technique called tip current voltammetry (TCV) was proposed to study potential distribution at semiconducter electrolyte interfaces. Usefulness of this method was demonstrated at p-GaP and n-GaAs electrodes.