Photoluminescence and cathodoluminescence studies of diatoms - nature’s own nano-porous silica structures.

Photoluminescence (PL) and cathodoluminescence (CL) data are presented for the silica frustules of some fresh water diatoms. The diatom frustules consist of a nano-porous silica structure that may possibly be exploited for optoelectronic or photonic applications. This work represents what we believe to be the first report of the CL and PL properties of this naturally occurring source of nano-porous silica.Australian and New Zealand Institutes of Physic

Long-term oxidization and phase transition of InN nanotextures

The long-term (6 months) oxidization of hcp-InN (wurtzite, InN-w) nanostructures (crystalline/amorphous) synthesized on Si [100] substrates is analyzed. The densely packed layers of InN-w nanostructures (5-40 nm) are shown to be oxidized by atmospheric oxygen via the formation of an intermediate amorphous In-Ox-Ny (indium oxynitride) phase to a final bi-phase hcp-InN/bcc-In2O3 nanotexture. High-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy and selected area electron diffraction are used to identify amorphous In-Ox-Ny oxynitride phase. When the oxidized area exceeds the critical size of 5 nm, the amorphous In-Ox-Ny phase eventually undergoes phase transition via a slow chemical reaction of atomic oxygen with the indium atoms, forming a single bcc In2O3 phase

High purity liquid phase epitaxial gallium arsenide nuclear radiation detector.

Surface barrier radiation detector made from high purity liquid phase epitaxial gallium arsenide wafers have been operated as χ- and γ-ray detectors at various operating temperatures. Low energy isotopes are resolved including 241Am at 40°C. and the higher gamma energies of 235U at - 80°C

Effect of crucible materials on impurities in LPE-GaAs.

LPE-GaAs grown in carbon, boron nitride and alumina crucibles has been examined using standard characterisation techniques including capacitance-voltage (C-V) measurements and deep level transient spectroscopy (DLTS). The epitaxial layers have net carrier concentration ranging from 5 × 1014 to 8 × 1015 carriers per cm3. DLTS data has shown that all epitaxial layers have deep level traps. © 1996, Elsevier Ltd

Etch rates for (100) gallium arsenide using aqueous h2so4h2o and aqua regia based etchants.

Etch rate experiments were carried out for (100) GaAs using etching solutions of H2SO4 :H2O2 :H2O (3:1:1 3:1:15) HCl:HNO3 (3:1) HCl:HNO3 :H2O (1: 1:1) and HCl:HNO3 :glycerol (with various dilutions of glycerol). Several differences were seen for the (100) plane compared to previous results for other crystal orientations. The sulphuric acid solutions showed much lower activation energies for etching the (100) plane. The HCl:HNO3 :glycerol solutions showed considerably lower etch rates for the (100) plane probably indicating that they etch GaAs anisotropically. For a 1:1:2 solution of HCl:HNO3 :glycerol a decrease in the etch rate of (100) GaAs was observed in the presence of stirring. This is the opposite result to what is commonly assumed for this polishing etchant. It indicates that the main polishing process attributed to this etchant is not present and in fact the polishing quality of the etchant is probably limited by the etching process which is present

Growth of high purity liquid phase epitaxial GaAs in a silica growth system.

Liquid phase epitaxial gallium arsenide layers, greater than 200 μm thickness and with a low net carrier concentration (NA,D ≈ 1013 cm−3) have been grown in a silicia growth system with silica crucibles. Analysis of electrical and chemical defects was carried out using capacitance-voltage (C---V) measurements, deep level transient spectroscopy (DLTS) and secondary ion mass spectroscopy (SIMS). Details of the growth procedure are given and it is shown that silicon incorporation in the growth layer is not suppressed by the addition of ppm levels of oxygen to the main hydrogen flow. © 1995, Elsevier Ltd

High-resolution X-ray photoelectron spectroscopy of AlxGa1-xSb

Surface oxidation and growth-derived oxygen contamination for Al 0.05Ga0.95Sb films, grown by metalorganic chemical vapour deposition (MOCVD), were systematically investigated using an X-ray photoelectron spectroscopy (XPS) system with high energy resolution. The Sb 3d5/2 and O 1s peaks were well resolved, as were the Ga 3d peaks. All samples investigated show oxide layers (Al2O3, Sb 2O3 and Ga2O5) on their surfaces. In particular, the percentage of aluminium oxide was very high at the sample surface compared to AlSb. Carbon incorporation was also examined. Adventitious surface carbon was high; however, in the bulk material carbon was below the detection limit of XPS and secondary ion mass spectroscopy (SIMS). These results indicate extremely low carbon content for the MOCVD growth of Al 0.05Ga0.95Sb epilayers.5 page(s

Surface passivation of liquid phase epitaxial GaAS.

Passivation of the liquid phase epitaxial GaAs surface was attempted using aqueous P2S5 -NH4OH (NH4)2Sx and plasma nitrogenation and hydrogenation. Results indicate that plasma nitrogenation with pretreatment of plasma hydrogenation produced consistent reduction in reverse leakage current at room temperature for all p and n type Schottky diodes. Some diodes showed an order of magnitude improvement in current density. (NH4)2Sx passivation also results in improved I-V characteristics though the long term stability of this passivation is questionable