The work reported here deals with studying the defects induced by heavy ion implantation as well as the degree of crystalline lattice recovery after annealing in a high purity argon environment between 600 and 1600 °C. We implanted 6H, n-type silicon carbide with Pd and Au ions at 1015 ions/cm2, and used Micro-Raman (MR) and optical absorption (OA) spectroscopy techniques for investigating the lattice properties and damage evolution at various stages during the fabrication process.

Glassy Polymeric Carbon (GPC), made from cured phenolic resins, is sufficiently chemically inert and biocompatible that it is suitable for medical applications, such as heart valves and other prosthetic devices. We have used energetic ion bombardment of the partially and fully cured precursor phenolic resins to enhance biological cell/tissue growth on, and to increase tissue adhesion to, prosthetic devices made from GPC. GPC samples were bombarded with energetic ions to 10 MeV. The surface topography and increased surface roughness was observed using optical microscopy and atomic force microscopy (AFM). The increased porosity was measured by introducing lithium from a molten LiCl salt into the GPC and using (p, α) nuclear reaction analysis (NRA) to measure the concentration of Li retention in the modified GPC. The NRA measurements of increased pore availability were correlated with the observations of increased surface roughness.

Silica samples were implanted at multiple energies with Se and Ge ionsproducing implanted layers ~ 2.4 µm in depth starting at ~ 0.5 µm below thesurface. In each case, the concentration of implanted species was ~ 0.05atomic %. The optical absorption of the samples was measured from 2.7 to 6.5eV. In all spectra, local maxima at 5.0 eV with shoulders at 5.9 eV wereobserved. The spectra have been assumed to be describable as a superpositionof Gaussian absorption bands with mean energies taken from the literature of4.8, 5.01, 5.17, 5.88, and 7.15 eV. The relative strengths of each of thesebands have been obtained by linear regression. These fits show thatadditional bands at 3.7 and 6.4 eV are required to fit the data for the Sesamples, while bands at 5.54 and 6.4 eV are needed to fit the data for theGe samples.

We have produced silicon carbide sensors by two techniques: palladium coating and low energy palladium implantation. The palladium implantation was done at 550°C into the Si face of 6H, n-type SiC at various energies and at various fluences. The sensitivity of each sensor was measured at temperatures between 20°C to 400°C. The response of the SiC sensors produced by Pd implantation has revealed a completely different behavior than the SiC sensors produced by Pd deposition. In the Pd deposited SiC sensors, as well as in the ones reported in the literature [1, 2], the current rises in the presence of hydrogen at room temperature as well as at elevated temperatures. In the case of Pd implanted SiC sensors, the current decreases in the presence of hydrogen whenever the temperature is raised above 100°C [3].

Palladium ion implantation was performed at energies of 35 keV, 50 keV and100 keV, at both room temperature (RT) and 500 °C, on two identical sets of6H, n-type silicon carbide samples. Then, one set of samples was subjectedto a post-implantation sputtering process, in order to eliminate thesubstrate layer damaged by the palladium ions during implantation.Electrical and micro-Raman measurements have been performed on both sets ofsamples, aiming for a better understanding of the chemical processes thattake place in the presence of hydrogen atmosphere in the chemical sensorsprepared this way.

We present the results of our investigation of producing nanoclusters of gold, silver, copper and tin in 6H-SiC. This is accomplished by implanting 1.0 MeV Au, 2.0 MeV Ag, 2.0 MeV Cu, and 160 keV Sn into the Si face of SiC at room or elevated temperature followed by annealing at various temperatures. Using optical absorption spectrophotometry, we determined the location of the absorption band for each metal nanocluster in SiC. Elevated temperature implantation reduces optical absorption due to ion implantation induced defects. Using the Mie theory, we determined the index of refraction in the implanted volume.

Silicon carbide, a wide-bandgap semiconductor, is currently used to fabricate an efficient high temperature hydrogen sensor. When a palladium coating is applied on the exposed surface of silicon carbide, the chemical reaction between palladium and hydrogen produces a detectable change in the surface chemical potential. Rather than applying a palladium film, we have implanted palladium ions into the silicon face of 6H, n-type SiC samples. The implantation energies and fluences, as well as the results obtained by monitoring the current through the sample in the presence of hydrogen are included below. The exposure to hydrogen of this kind of sensor while monitoring the current flow with respect to time, has revealed a completely different behavior than the samples that have Pd deposited as a surface layer.

We present the preliminary results of our investigation of producing nanoclusters of gold and tin in 6H-SiC. In this work we study the changes in the linear optical properties as a function of ion fluence and post-implantation heat treatment. The optical absorption is complemented by micro-Raman spectroscopy to investigate lattice damage and recovery. We implanted 1.0 MeV Au and 120 and 160 keV Sn into the Si face of SiC at 30 or 500°C followed by annealing at various temperatures. Using optical absorption spectrophotometry, we determined the location of the absorption band for each metal nanocluster in SiC. Elevated temperature implantation greatly reduced optical absorption due to ion implantation induced defects. Using Mie theory, we determined the index of refraction in the implanted volume and estimated the size of the Au nanoclusters as 5 nm in diameter. Rutherford backscattering analysis of the oxide layer grown during annealing showed an increase of 20 percent in on the implanted side. It was found that the Au clusters occurred only in the oxide layer.

In this paper, we present the results of our investigation of producing nanoclusters of gold in silica at fluences of two orders of magnitude less than what is traditionally used This is accomplished by implanting 2.0 MeV Au into silica followed by MeV bombardment by MeV Si ions. The size of the nanoclusters, ranging from one to 10 nanometers, is controlled by the implantation dose and by the total electronic energy deposited by each post bombarding ion in the implanted layer. By both indirect measurement methods, such as optical absorption spectrophotometry (non-destructive), and direct methods, such as transmission electron microscopy (destructive) we show how and at what concentrations gold nucleates to form nanoparticles by radiation-enhanced nucleation at a dose below that needed for spontaneous nanoparticle formation.

We report the results of characterization of linear and nonlinear optical properties of a light guide structure produced by MeV Ag ion implantation of LiNbO3 crystal (z-cut) in relation to the mechanisms of formation.

We present the results of our investigation of the change in the optical properties of silica, "suprasil", after keV through MeV implantation of copper, tin, silver and gold and after annealing. Suprasil, name brand of silica glass produced by Hereaus Amersil, which is chemically highly pure with well known optical properties. Both linear and nonlinear optical properties of the implanted silica were investigated before and after thermal annealing. All implants showed strong optical absorption bands in agreement with Mie theory. For implants with a measurable optical absorption band we used Doyle's theory and the full width half maximum of the absorption band to calculate the predicted size of the formed nanoclusters at various heat treatment temperatures. These results are compared with those obtained from direct observation using transmission electron microscopic techniques.

The electronic and nuclear stopping effects produced by MeV ion bombardment in polyethylene (PE) and polyvinylidene chloride (PVDC) have been previously studied and reported. We have subsequently selected two other insulators: polystyrene (PS) and polyethersulfone (PES) which contains sulfur as a crosslinking agent, and irradiated them with MeV alpha particles. The electronic and nuclear effects of the incident ions were separated by stacking thin films of the polymers. A layered system was selected such that the first layers experienced most of the effects of the electronic energy deposited and the last layers received most of the effects of the nuclear stopping. The changes in the chemical structure were measured by residual gas analysis (RGA), Raman microprobe analysis, RBS and FTIR. The post-irradiation characterization resolved the effects of the stopping powers on the PS and PES and the results were compared with those from PE and PVDC.

We have studied the formation of nano-crystals, after implantation of 2.0 MeV gold, 1.5 MeV silver, 160 keV copper and 160 keV tin into single crystal of A12O3. We also studied the change in the linear optical properties of the implanted Al2O3 before and after subsequent annealing by measuring the increase in resonance optical absorption. Applying Doyle's theory and the results obtained from Rutherford backscattering spectrometry (RBS) as well as the full width half maximum of the absorption band from Optical Absorption Photospectrometry (OAP), we measured the average size of the metallic clusters for each sample after heat treatment. The formation and crystallinity of the nanoclusters were also confirmed using transmission electron microscopy (TEM) technique.

We have implanted ions of Sn, Au and Cu at energies between 160 keV and 2.0 MeV into single crystals of MgO (100) at room temperature. The formation of nanoclusters was confirmed using photospectrometry, in combination with Mie's theory, which was indirect but nondestructive. Using Doyle's theory, as well as Rutherford Backscattering Spectrometry (RBS), we correlated the full width half maximum of the absorption bands to the estimated size of the metallic nanoclusters between 1–10 nm. These clusters were formed both by over implantation and by a combination of threshold fluence of the implanted species and post thermal annealing. The changes in the estimated size of the nanoclusters, after annealing at temperatures ranging from 500°C to 1000°C, were observed using photospectrometry.

We present the results of characterization of linear absorption and nonlinear refractive index of Au, Ag, Cu and Sn ion implantation into LiNbO3. Silver was implanted at 1.5 MeV to fluences of 2 to 17 × 1016/cm2 at room temperature. Gold and copper were implanted to fluences of 5 to 20 × 1016/cm2 at an energy of 2.0 MeV. Tin was implanted to a fluence of 1.6 × 1017/cm2 at 160 kV. After heat treatment at 1000°C a strong optical absorption peak for the Au implanted samples appeared at ∼620 nm. The absorption peaks of the Ag implanted samples shifted from ∼450 nm before heat treatment to 550 nm after 500°C for lh. Heat treatment at 800°C returned the Ag implanted crystals to a clear state. Cu nanocluster absorption peaks disappears at 500°C. No Sn clusters were observed by optical absorption or XRD. The size of the Ag and Au clusters as a function of heat treatment were determined from the absorption peaks. The Ag clusters did not appreciably change in size with heat treatment. The Au clusters increased from 3 to 9 nm in diameter upon heat treatment at 1000°C. TEM analysis performed on a Au implanted crystal indicated the formation of Au nanocrystals with facets normal to the c-axis. Measurements of the nonlinear refractive indices made using the Z-scan method showed that Ag implantation changed the sign of the nonlinear index of LiNbO3 from negative to positive.

The effect of the ion implantation (Fe) on LiNbO3, MgO, and A12O3 crystals is studied using electron paramagnetic resonance (EPR). EPR measurements on these crystals were performed as a function of fluence at room temperature. The fluence was 1 × 1014 and 1 × 1016 ions/cm2. The unpaired carrier concentration increases with increasing fluence. The photosensitivity of these crystals was determined by observing in situ the effect of the laser illumination on the EPR signal and measuring the decay and the growth of the EPR signal. The EPR signal of Fe3+ was found to decrease in both MgO, and Al2O3; and was found to increase in LiNbO3. This indicated that in case of MgO, and A12O3 Fe3+ will transfer into Fe2+/Fe4+, but in case of LiNbO3 Fe2+/ Fe4+ will transfer into Fe3+; increasing the EPR signal. This was found primary due to some Fe2+ and Fe4+ ions, which is not intentionally doped on the LiNbO3 crystal but exist as a defect on the crystal.

The electronic (εe) and nuclear (εa) stopping effects produced by 3.5 MeV and 5.0 MeV ion bombardment in polyvinylidine chloride (PVDC), polyethylene (PE) and polyethylene sulfide were studied and compared. To separate these effects we chose two bombardment energies and a thin film polymer stacking technique developed in house. The resulting stacked layered system consisting of each polymer was bombarded with 3.5 MeV and 5.0 MeV alpha particles. The layered system was selected such that the first few layers experience most of the effects of the electronic energy deposited and the last layer receives the effects of the nuclear stopping. The electrical conductance and the changes in the chemical structure were measured by direct resistivity measurements, Raman microprobe analysis, RBS, and FTIR. The post-irradiation characterization resolved the effects of the stopping powers on the polymer films.

The implantation of metal ions into photorefractive materials followed by thermal annealing leads to an increase in resonance optical absorption as well as an enhancement of the nonlinear optical properties. We have implanted ions of Au (3.6 MeV), Ag (1.5 MeV) and Cu (2.0 MeV) into pure silica followed by careful heat treatment. Using optical absorption spectrophotometry and rutherford backscattering spectrometry we have measured the cluster size for each heat treatment temperature and determined the activation energies for their formation. The third order electric susceptibility for silica with 2 nm gold clusters has been determined by Z-scan to be 65×10−8 esu.

Nanoclusters of Ag metal in MgO(100) single crystals was formed by implantation of 1.5 MeV silver ions at fluences of 6 x 1016 ion/cm2 and at 1.2 x 1017 ion/cm2, and subsequent annealing at temperatures between 600°C to 1100°C. The formation of the Ag metallic clusters was confirmed using optical absorption spectrophotometry by the absorption band at 430 nm. This is in agreement with the theoretical prediction using Mie's theory, with calculated average nanocluster size about 3 nm. Using ion channeling we confirmed that the orientation of the Ag nanoclusters was in the same direction of the host crystal. Using Z-scan we found the nonlinear refractive index of Ag implanted MgO to be 4.9 x 10-8 esu.

Al was deposited on the both sides of p-type Si by the sputtering, and the pulsed KrF excimer laser was irradiated on the one side and both sides of Al dot contacts. Due to the thin-high doping recrystallized layer, the transitions from the Schottky diodes to the ohmic contacts via backward diodes were observed in I-V measurement. Good N-shape negative resistances and notches were observed in the diodes, and ohmic contacts. Possible interpretations of the orgin of these phenomena are discussed. And, the simple model of the effective barrier height reduction under the thermionic field emission was developed using WKB approximation, and tunneling theory. By the depth Auger analysis, Al, and Si profiles near Al-Si interface after the laser irradiation were observed.