Epitaxially grown GaN by metal organic chemical vapor deposition (MOCVD) on SiC were implanted with 100 keV Si+ (for n-type) and 80 keV Mg+ (for p-type) with various fluences from 1×1012 to 7×1015 ions/cm2 at liquid nitrogen temperature (LT), room temperature (RT), and 700 °C (HT). High temperature (1200 °C and 1500 °C) annealing was carried out after capping the GaN with epitaxial AIN by MOCVD to study damage recovery. Samples were capped by a layer of AIN in order to protect the GaN surface during annealing. Effects of implant temperature, damage and dopant activation are critically studied to evaluate a role of ion implantation in doping of GaN. The damage was studied by Rutherford Backscattering/Channeling, spectroscopic ellipsometry and photoluminescence. Results show dependence of radiation damage level on temperature of the substrate during implantation: implantations at elevated temperatures up to 550 °C decrease the lattice disorder; “hot implants” above 550 °C can not be useful in doping of GaN due to nitrogen loss from the surface. SE measurements have indicated very high sensitivity to the implantation damage. PL measurements at LT of 80 keV Mg+ (5×1014 cm-2) implanted and annealed GaN showed two peaks : one ∼100 meV and another ∼140 meV away from the band edge.

Radiation damage and its removal have been studied in ion implanted 6H-SiC by Rutherford backscattering/Channeling (RBS). We have implanted Ga and Ti at 800°C using doses of 1 × 1016 to 2× 1017 cm−2. The implanted samples have been subsequently annealed at 1050°C, and then at 1400°C for 30 sec to study the removal of damage produced during implantation. The energies of implanted species have been chosen to obtain 20 – 40 nmn projected ranges to form a buried metallic or graphitic layer. No significant damage removal has been observed after 1050°C anneal, however 1400°C annealing of 40 and 120 keV Ga implanted samples (fluence 2 × 1016 cm−2) resulted in significantly less damage as can be observed from RBS/Channeling data. In the case of Ti implanted samples annealing led to an appreciable increase in the channeled backscattering yield, which might be due to the formation of some new phase (e.g. TiSi or TiSi2 ) and may be related to distortions of the existing lattice.

Nanocomposites of iron in sapphire (α-A12 O3) prepared by ion implantation have been studied as a model to investigate the potential of such materials for applications in high technology areas. The implantation was performed with 160 keV ions at several doses; the nanocomposites were then annealed at selected temperatures between 700 and 1400°C in an Ar-4&H2 atmosphere for 1 hour. Rutherford backscattering spectroscopy and high resolution transmission electron microscopy (TEM) were used to characterize the structure of these nanocomposites. Measurements showed that damage depth extended to about 300 nm and the embedded iron extended to about 200 nm. This region became amorphous when the fluence reaches 2x1017 Fe/cm2 at this energy. At this dose, oriented precipitates with diameters of 2 to 3 nm were identified by TEM techniques as α-Fe which had the following orientation relationship with the sapphire matrix: <111>Fe||<310>Sapphire and (011)Fe||{006}sapphire. Thermal annealing could be used to restore the crystallinity to the damaged near-surface region, to form the metallic colloids, and also to coarsen the precipitates. The optical density and luminescence spectra were also measured. The predominant defects were oxygen vacancies with two electrons (F center) at the known absorption peak of 200 nm.

Single crystal, type IIa natural diamond substrates have been implanted with 4 MeV carbon ions to doses ranging from 0.5–130×1016 cm-2. The accumulation of implantation damage is studied by Raman and RBS/channeling. Similar effects are observed for crystals of [100], [110], and [111] orientation but with different rates of damage accumulation. With increasing implantation damage, the triply degenerate Raman mode at 1332 cm-1 broadens and shifts down to around 1300 cm-1. This corresponds to a peak in the one-phonon density of states as predicted for Raman from an amorphous sp3 network. There is no evidence for the existence of sp2 carbon in the implanted area. Additional non-graphite Raman peaks appear at 1451, 1494, and 1635 cm-1. At the higher doses, the 1332 cm-1 Raman mode is no longer observed; however, RBS/channeling still shows the surface region to be crystalline and it is possible to grow high quality homoepitaxial diamond films on these substrates.

In the present study epitaxial Ni(001) films have been grown on natural C(001) substrates (type la and Ha) and homoepitaxial C(001) films. Two deposition techniques including electron-beam evaporation of Ni in a molecular beam epitaxy (MBE) system and evaporation of Ni from a resistively heated tungsten filament have been employed. As evidenced by scanning electron microscopy (SEM), the Ni films deposited by electron-beam evaporation were found to replicate the very fine, unidirectional scratches present on the as polished C(001) substrates. Indeed, the coverage and uniformity of the deposited films would imply a two-dimensional (2-D) growth mode. In comparison, the thermal evaporation of Ni on C(001) substrates results in a highly textured and faceted surface morphology indicative of three-dimensional (3–D) nucleation and growth. Moreover, Rutherford backscattering/channeling measurements have demonstrated that the Ni(001) films deposited by electron-beam evaporation are of superior crystalline quality. Differences in the observed microstructure and apparent growth modes of the epitaxial Ni(001) films have been attributed to the presence of oxygen incorporation in those layers deposited by thermal evaporation.

We have used RBS/Channeling, perturbed angular correlation (PAC) and optical absorption to study the regrowth of disordered layers in diamond produced by implantation with carbon, or with carbon plus boron or indium ions. For C or C plus B implantation doses of 2 ×1015 cm−2 or less, complete recovery of channeling damage occurred after RTA at 1100°C or furnace annealing at 900°C. Optical measurements on samples implanted with high energy carbon ions show better recovery compared to the shallower implantations. PAC results showed that co-implantation with C and In caused a considerable fraction (∼15%) of the In-atoms to occupy well-defined lattice sites characterized by an electric field gradient having its major component along <111>, and a frequency of 116 MHz.