Earnshaw Medal
Earnshaw 2008 Nominees: Irene Mencke
Potential-Dependent Phtoluminescence Spectroscopy and Capacitance-Voltage Measurements on Indium Phosphide Nanostructures
This thesis describes a study carried out to investigate the potential dependence of photoluminescence from Indium Phosphide using photoexcitation. Nanoporous InP was prepared by anodic etching, the photoluminescence spectrum of which was then studies as a function of wavelength and later potential. The characteristics of the in-situ photoluminescence (PL) from InP/electrolyte junctions have been studied as a function of potential and wavelength and the ex-situ (in air) characteristics as a function of wavelength. The results obtained were correlated with capacitance-voltage measurements. In particular quantum confinement effects in nanostructures were investigated by experimenting, using photoluminescence techniques, with nanostructures of different dimensions. The photoluminescence signal intensity and also peak positions from the porous samples were compared to that of the bulk samples and the variance in these with applied potential was identified. In addition, scanning electron microscopy was used to characterize the InP nanostructures.
Two difference sets of apparatus were used in the project; the PL setup was constructed to obtain photoluminescence results. This setup was already in use within the department, but being an optical system, it was sensitive and needed regular calibration and adjustment. For in-situ measurements the setup had to be adjusted accordingly to accommodate an electrochemical cell. An electrochemical cell was used to etch the samples and also to obtain the capacitance-voltage date for Mott-Schottsky plots.
InP samples were prepared using a standard technique: 3mm x 3mm pieces were cleaved from the same InP wafer, the (100) face was isolated at the end of a wire fixed in a small pipette.
Supervisor: Prof. Noel Buckley
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