| The design, fabrication and use of a near field scanning optical microscope to investigate the structure-property relationships of porous gallium arsenide is reported. Novel porous gallium arsenide (GaAs) surfaces containing crystalline features were formed through an electrochemical corrosion process. Surface characterization techniques including XPS, AES and EDAX were utilized to identify the crystalline features as arsenic oxide species. From the surface analysis data, as well as observations of crystalline thermal sublimation and decomposition, it is hypothesized that the GaAs pores contained large (∼40 mum x ∼30 mum) surface As2O3 crystals and smaller (1--5 mum 2) As2O5 micro-crystals within the porous features. The composition and morphology of the porous surfaces was shown to vary with corrosion time. Fluorescence microscopy of individual GaAs pores reveals that the porous as well as the arsenic oxide crystals photoluminesce in the visible region (lambdaexcitation = 488nm, lambdaemission = 540nm). Spatially localized near field photoluminescence spectroscopy of the crystalline and porous features was performed to elucidate the source of the observed visible photoluminescence. The near field spectroscopic analysis of the surfaces indicates that the visible photoluminescence is not due quantum confinement effects, but due to the arsenic oxide crystals on the porous surface. |
