Previous studies have indicated that dual implantation can efficiently introduce group IV dopant onto selected sub-lattice sites in m-V compound semiconductors, thus enhancing electrical activation. We studied this phenomenon in GaP using Rutherford Backscattering Spectroscopy (RBS) to determine the lattice location of Sn atoms. We used single crystals of GaP (100) which had been implanted at 400° C with120 Sn+ following previously implanted69 Ga+ or31P+. Energies were selected for euivalent projected ranges, and all species were implanted with doses of 1 × 1015 atoms/cm2 . Asymmetry in the angular scan of the {111} planar channel was then used to determine the sub-lattice location of the implanted Sn. RBS results indicated that for all implants Sn atoms were substituting Ga and P sites eually. However, Hall effect measurements gave p type conduction for GaP implanted with Sn alone, while those with prior implants of Ga or P resulted in n-type conduction. RBS and Hall effect results are explained by a vacancy complex model.

A technique is described for direct measurement of evaporation of Ga and As from capped GaAs during RTP. Application of this method to the study of Si, SiO2, and Si3N4 caps with thicknesses of 20 nm to 60 nm provides a direct measure of the temperature ranges for which the caps are able to prevent evaporation during RTP. In addition, kinetic studies of the evaporation at slightly higher temperatures provides information useful for establishing the predominant evaporation mechanism. For the encapsulants studied, these measurements indicate that the observed evaporation is due to formation of cracks in the film during the initial 10 sec of RTP.

We have examined the damage produced by Si-ion implantation into strained Si1-xGex epilayers. Damage accumulation in the implanted layers was monitored in situ by time-resolved reflectivity and measured by ion channelling techniques to determine the amorphization threshold in strained Si1-xGex, (x = 0.16 and 0.29) over the temperature range 30-110°C. The results are compared with previously reported measurements on unstrained Si1-xGex, and with the simple model used to describe those results. We report here data which lend support to this model and which indicate that pre-existing strain does not enhance damage accumulation in the alloy layer.

We report the successful fabrication of 6 ώm thick slices from a ferroelectric domain micro-engineered LiNbO3 wafer device using the crystal ion slicing technique. The device was created by micropatterning ferroelectric domains in a bulk 0.3 mm thick wafer of z-cut LiNbO3, followed by ion-implanting with 3.8 MeV He+ ions to a fluence 5 × 10+16 ions/cm2 to create a damage layer at a well defined depth from the surface. Etching away this damaged layer in dilute hydrofluoric acid results in a liftoff of the top slice in which the ferroelectric domain patterns are left intact. The influence of annealing conditions on liftoff time and depth of etch lines was studied. Helium-Neon laser light was successfully coupled into the device. Due to unintentional breakage of the polished input and output faces, the electro-optic scanning performance has not been characterized so far.

Recent work has demonstrated that the process of silicon thin-film separation by hydrogen implantation, as well as the more basic phenomenon of surface blistering, can occur at a much lower total dose when H and He are co-implanted than when H is implanted alone (1). Building on that work, this paper investigates the role of implantation damage in this process by separating the contributions of gas pressure from those of damage. Three different experiments using co-implantation were designed. In the first of these experiments, H and He implants were spatially separated thereby separating the damage from each implant. The second experiment involved co-implantation of H and He at a temperature of 77 K to retain a larger amount of damage for the same gas dose. In the third experiment, Li was co-implanted with H, to create additional damage without introducing additional gas. These experiments together show that increasing the implantation damage itself hampers the formation of surface blisters, and that the increased efficiency observed for He co-implantation with H is due to the supplementary source of gas provided by the He (1).

Z-scan and pump-probe measurements with ultra-fast 800 nm laser pulses were used to compare the ultrafast third-order optical nonlinearities of VO2 nanoparticles and thin films in both semiconducting and metallic states. It is found that when the samples are hold at temperatures above 67oC in their metallic state, both nanocrystals and thin films present a positive intensity-dependent nonlinear index of refraction. In this metallic state the nanocrystals exhibit a saturable optical nonlinearity and enhancement of the nonlinear effects larger than those found in thin films. Below the transition temperature, the optical nonlinearities are more complex, since they arise from alterations in the VO2 that arise both from the phase transition and from unrelated third-order nonlinear effects. Under these conditions, thin films exhibit a complete reversal to a negative nonlinear index of refraction while the nanocrystals, remarkably, show a smaller but still positive index. Pump-probe measurements on vanadium dioxide nanocrystals and thin films show they both exhibit an ultrafast response, undergoing the phase transition induced by a single laser shot in less than 120 fs. The speed of the solid-solid transformation, along with the striking reversal of the nonlinear properties across the phase transition, puts vanadium dioxide in a unique category among nonlinear materials.

We study the ultrafast insulator-to-metal transition in nanoparticles of VO2, obtained by ion implantation and self-assembly in silica. The nonmagnetic, strongly correlated compound VO2 undergoes a reversible phase transition, which can be photoinduced on an ultrafast time scale. In the nanoparticles, prompt formation of the metallic state results in the appearance of surface-plasmon resonance. We achieve large, ultrafast enhancement of optical absorption in the near-infrared spectral region that encompasses the wavelength range for optical-fiber communications. One can further tailor the response of the nanoparticles by controlling their shape.

We report on the study of the ultrafast insulator-to-metal transition in nanoparticles of strongly correlated VO2. The particles are grown by ion-implantation and self-assembly in a Silica matrix and can be switched between the insulating and metallic phase within less than 100 fs. The prompt formation of the metallic state results in the appearance of a surface-plasmon resonance that is absent in the bulk and can be further tailored by controlling the particle shape.

Vanadium dioxide undergoes a structural (monoclinic to tetragonal) insulator-to-metal transition at 70degreesC, accompanied by large changes in electrical and optical properties. By combining focused ion-beam lithography and pulsed laser deposition, patterned nanoscale arrays of vanadium dioxide nanoparticles are created that can be used for studies of linear and nonlinear optical physics, as well as demonstrating the potential for a variety of applications.

A new generation of devices where the electronic, optical or magnetic state of a system can be controlled optically on the ultrafast timescale is one of the most compelling technological ramifications of the rapidly advancing field of strongly correlated electrons. However, for real-world applications it is also necessary to incorporate these compounds in appropriate environments (e.g. optical fibers or silicon-based electronics), to ensure compatibility with existing technologies (e.g. telecom wavelengths), room temperature operation and limited power densities. Here, we report on the study of the photo-activated optical switching in nanorods of strongly correlated VO{sub 2}. The particles are grown by ion-implantation and self-assembly within a Silica matrix or an optical fiber, operate at room temperature and can be switched between the insulating and metallic phase within less than 100 fs. The energy threshold to achieve switching corresponds to approximately 500 pJ within the core of a single mode fiber and is compatible with current diode technologies. Tailoring of the spherical/cylindrical geometry results in control of the spectral response of the system, which is dominated by the impulsive formation of a surface plasmon upon the insulator-to-metal transition. The response at the technologically important 1.55 {micro}m wavelength is in this way maximized.

Controllable introduction and characterization of defects in single wall carbon nanotubes (SWNT) is the first step toward chemical functionalization of SWNTs for strong bonding and controllable properties in SWNT-polymer composites, and for other applications of SWNTs. The defects or imperfections were introduced using various techniques, including ozone treatment, Ar-ion beam irradiation (E=5kV), alpha-particle irradiation (E=5.3 MeV, Po 210 source), and electron beam irradiation of purified and raw SWNTs synthesized by laser evaporation. The defects were studied using the D-band (~1320 cm -1 for λext.= 633 nm) in Raman spectra of SWNTs and high resolution TEM. The D/G-band intensity ratio in Raman spectra of SWNTs was approximately correlated with the surface density of defects in SWNTs using Ar-ion beam irradiation of SWNTs at different well defined irradiation doses, 10 12 -10 15 1/cm 2 , and a Monte Carlo simulation of this process. It was shown that even a very small ozone concentration (~5 ppm) could produce remarkable number of defects in SWNT that have clear signatures in their Raman spectra, i.e., the increase of D/G-band ratio and the decrease of the intensity of the metallic tangential mode. It was also demonstrated that the ozone treatment considerably changes the chemical properties of SWNTs which could be useful for their chemical functionalization for different applications in SWNT-polymer composites.