Crystalline germanium substrates were amorphised to a depth of one micron by ion implantation of germanium ions at a series of relatively high energies and dose. Using the ion implantation modeling software TRIM, this paper compares the amorphisation results from the ion implantation simulations and experimental results from transmission electron microscopy (TEM) analysis of cross-sections of implanted samples. TEM cross-section micrographs show a clear boundary between amorphous and crystalline germanium. The effect of amorphisation of Ge on the subsequent formation of Nickel germanide is demonstrated and one significant issue is the increased depth of NiGe grains formed on a-Ge compared with c-Ge.
Vanadium Dioxide is an optically dense phase change material that has been applied to modulating the resonances of plasmonic structures resonant in the THz, infrared and optical ranges. It has been shown previously that fabrication of optical antennas on thin films of Vanadium Dioxide can result in a resonance shift of more than 10% across the phase change. This post-fabrication, dynamic tuning mechanism has the potential to significantly increase the possible applications of plasmonic devices.
Here, we show that optical antenna arrays fabricated on differing thicknesses of Vanadium Dioxide supported by a silicon substrate show a dependence of their resonant wavelengths on this thickness. Along with the geometry of the antennas in the arrays this constitutes an additional degree of freedom in the design of the tuning range of these devices, offering further potential for optimisation of this mechanism. The potential extra blue-shift provided by optimising this thickness may be used, for example, in lieu of reducing antenna dimensions to avoid increasing antenna absorption and the additional plasmonic heating that can result.
In the last decade, the synthesis and characterization of nanometer sized carbon clusters have attracted growing interest within the scientific community. This is due to both scientific interest in the process of diamond nucleation and growth, and to the promising technological applications in nanoelectronics and quantum communications and computing. Our research group has demonstrated that MeV carbon ion implantation in fused silica followed by thermal annealing in the presence of hydrogen leads to the formation of nanocrystalline diamond, with cluster size ranging from 5 to 40 nm. In the present paper, we report the synthesis of carbon nanoclusters by the implantation into fused silica of keV carbon ions using the Plasma Immersion Ion Implantation (PIII) technique, followed by thermal annealing in forming gas (4% <sup>2</sup>H in Ar). The present study is aimed at evaluating this implantation technique that has the advantage of allowing high fluence-rates on large substrates. The carbon nanostructures have been characterized with optical absorption and Raman spectroscopies, cross sectional Transmission Electron Microscopy (TEM), and Parallel Electron Energy Loss Spectroscopy (PEELS). Nuclear Reaction Analysis (NRA) has been employed to evaluate the deuterium incorporation during the annealing process, as a key mechanism to stabilize the formation of the clusters.
Implantation of Ti at MeV energies has been investigated as a means of locally doping sapphire with Ti to form Ti:sapphire: a highly valued laser material. Previous investigations of this approach to synthesis of Ti:sapphire have shown that the Ti<sup>3+</sup> luminescence yield continuously increases with increasing annealing temperature up to 1500°C when a reducing ambient of 96% Ar + 4% H is used in an alumina tube furnace. Here we present preliminary results for anneals performed in the high temperature regime of 1500-1700°C in either an Ar or 96% Ar + 4% H ambient in a graphite furnace. Optical characterisation using photoluminescence (PL) has been combined with structural analysis using Rutherford backscattering spectrometry and ion channeling to study the annealing behavior of the ion implanted layers, the evolution of the Ti profile and the dependence of formation of Ti<sup>3+</sup> on the implantation conditions, annealing ambient and temperature in this regime. At these annealing temperatures the Ti diffuses substantially. For anneals up to 1500°C, the reducing ambient produces the higher PL yields. At 1700°C, annealing in Ar results in higher PL yields whilst the reducing ambient leads to oxygen loss from the near-surface region and a concurrent reduction in PL yield. Annealing at 1700°C in Ar allows higher concentrations of Ti to be incorporated into sapphire in the 3+ oxidation state.