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Both hexagonal wurtzite and cubic zinc blend GaN phases were synthesized in GaAs by 50 keV N+ implantation at 400 °C and subsequent annealing at 900 °C for 15 min in N2 ambient. The crystallographic structural and Raman scattering studies revealed that GaN phases were grown for fluence above 2×1017 cm-2. Temperature-dependent photoluminescence study showed a sharp direct band-to-band transition peak ∼3.32 eV at temperature ≤=200 K. The intermediate band-gap value, with respect to ∼3.4 eV for hexagonal and ∼3.27 eV for cubic phases of GaN, is indicative of the formation of mixed hexagonal and cubic phases [ABSTRACT FROM AUTHOR]

The formation of voids and bubbles during ion implantation is an important area of material research. Void and bubble formation can result in swelling and embrittlement of metallic or semiconducting materials, and increase catalytic effects in the nanopores of the bubble. Here, we report the observation of metallic nanoblister formation in GaN nanowires under self-ion implantation using a Ga+ focused ion beam. The mechanism of the blister formation was resolved using high-resolution transmission electron microscopy equipped with electron energy loss spectroscopy and plasmon imaging. [ABSTRACT FROM AUTHOR]

Hexagonal to cubic phase transformation is studied in focused ion beam assisted Ga+-implanted GaN nanowires. Optical photoluminescence and cathodoluminescence studies along with high-resolution transmission electron microscopic structural studies are performed to confirm the phase transformation. In one possibility, sufficient accumulation of Ga from the implanted source might have reduced the surface energy and simultaneously stabilized the cubic phase. Another potential reason may be that the fluctuations in the short-range order induced by enhanced dynamic annealing (defect annihilation) with the irradiation process stabilize the cubic phase and cause the phase transformation. [ABSTRACT FROM AUTHOR]

Growth of truncated hexagonal dipyramidal Au nanoislands is reported by annealing Au/ amorphous-Si/crystalline-Si at 1030 °C in oxygen and nitrogen ambient. Metastable gold silicide phase of Au[SUB7]Si is observed to form at the interface of Au and polycrystalline Si, which was transformed from amorphous Si. Oxygen, acting as an impurity, inhibits outdiffusion of Si at the interface and thus controls the growth of Si deficient metastable phase of Au[SUB7]Si in a diffusion-limited growth process. Interface energies of Au[SUB7]Si (0.623-0.672 N/m) and Au-Au[SUB7]Si (1.438-1.471 N/m) are derived from the contact angle measurements of the island structure involving Au and Au[SUB7]Si. [ABSTRACT FROM AUTHOR]

Ga[SUP+]ion implantation of chemical-vapor-deposited GaN nanowires (NWs) is studied using a 50-keV Ga[SUP+]focused ion beam. The role of dynamic annealing (defect-annihilation) is discussed with an emphasis on the fluence-dependent defect structure. Unlike heavy-ion-irradiated epitaxial GaN film, large-scale amorphization is suppressed until a very high fluence of 2 ×10[SUP16] ions cm[SUP-2]. In contrast to extended-defects as reported for heavy-ion-irradiated epitaxial GaN film, point-defect clusters are identified as major component in irradiated NWs. Enhanced dynamic annealing induced by high diffusivity of mobile point-defects in the confined geometry of NWs is identified as the probable reason for observed differences. [ABSTRACT FROM AUTHOR]

Presents a commentary on a method for the formation of gold nanowires embedded in silicon nanowire templates. Transmission electron microscopy image of the annealed sample; Analysis of interlayer spacing; Role of oxygen.