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Growth of epitaxial gold silicide islands on bromine-passivated Si (111) substrates has been studied by optical and electron microscopy, electron probe micro analysis and helium ion backscattering. The islands grow in the shape of equilateral triangles up to a critical size beyond which the symmetry of the structure is broken, resulting in a shape transition from triangle to trape- Typeset using REVT E X 1

Vertically aligned TiO 2-δ and TiO 2−3yN2y nanotube array thin films were synthesized electrochemically in a single step. N-Doping at different levels was achieved by using different concentrations of urea, as nitrogen precursor, in the electrolyte. The GIXRD and Raman studies revealed that the nanotube arrays are of anatase phase. The field emission measurements showed low turn-on fields of 10, 9.21, and 6.54 V/μm at 3.88, 4.12, and 4.74 at% of N-doping, respectively, implying enhanced field emission upon N-doping as well as an increase in electron emission with increase in N-doping. The electron emission current was found to be stable for a period of 5 h. The high electron emission current and low threshold field on N-doping is due to the presence of localized donor states below the conduction band minimum, as a result of oxygen vacancies, created by N-doping, and introduction of localized N 2p states above the valence band minimum by the doped nitrogen .

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Enhanced electron field emission (EFE) properties have been observed for nitrogen implanted ultra-nanocrystalline diamond (UNCD) films grown by microwave plasma enhanced CVD. X-ray photoelectron spectroscopy (XPS) measurements show that sp2 fraction and C-N bonding increase upon N-implantation and annealing. Significant difference in current-voltage (I-V) curves at the grain and grain boundary has been observed from scanning tunneling spectroscopic (STS) measurement. From the variation of normalized conductance (dI/dV)/(I/V) versus V, bandgap is measured to be 4.8 eV at the grain and 3.8 eV at the grain boundary for as prepared UNCD. Upon nitrogen implantation and annealing, the bandgap decreases for both grain and grain boundary and density of states are introduced in the bandgap. Current imaging tunneling spectroscopy (CITS) imaging shows that the grain boundaries have higher conductivity than the grains and are the prominent electron emitters. The enhancement in EFE properties upon nitrogen implantation is accounted for by the decrease in bandgap, increase in density of states in the bandgap caused by increase in sp2 content and new bonds at the diamond grains, and increase in conductivity at the grain boundary.