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Rutherford backscattering/channeling spectrometry and transmission electron microscopy were used to study the effects of elevated-temperature ion bombardment of wurtzite GaN films.

Wurtzite GaN epilayers bombarded at 300 K with 200 MeV 197 Au 16+ ions are studied by a combination of transmission electron microscopy (TEM) and Rutherford backscattering/channeling spectrometry (RBS/C). Results reveal the formation of near-continuous tracks propagating throughout the entire∼ 1.5-µ m-thick GaN film. These tracks,∼ 100Å in diameter, exhibit a large degree of structural disordering but do not appear to be amorphous. Throughout the bombarded epilayer, high-resolution TEM reveals planar defects which are parallel to the basal plane of the GaN film. The gross level of lattice disorder, as measured by RBS/C, gradually increases with increasing ion fluence up to∼ 10 13 cm-2. Based on these results, physical mechanisms of the formation of lattice disorder in GaN in such a high electronic stopping power regime are discussed. [ABSTRACT FROM AUTHOR]

Single crystal GaN epilayers with pre-existing surface disordered layers are bombarded at room temperature with P ions and stable lattice defects are analyzed by using Rutherford backscattering/channeling spectrometry. The studies have shown that the rate of planar surface amorphization is independent of the concentration of pre-existing defects near the amorphous/crystalline (a/c) interface

The two major contributors of roughness to plastic deformation are shown to be surface bands of the basal slip systems and thermal grooves formed on deformation-produced low-angle grain boundaries. The studies have major implications for designing strategies aimed at controlling uniformity of the hydrogen fuel layer in fusion targets.

The effects of the collision cascade density on damage accumulation are examined by studying the structural defects in ZnO bombarded at room-temperature (RT) with atomic P and cluster P[F.sub.n], where n = 2 and 4, ions. The cascade density has affected the radiation damage in the near-surface region and an intermediate defect peak is formed between the surface and bulk peaks of disorder for ion irradiation conditions with dense cascades.

Soft x-ray absorption near-edge structure (XANES) spectroscopy is used for studying the electronic structure of ultralow density nanoporous chromatin monoliths (aerogels). Thermal treatment has transformed the as-prepared amorphous aerogel into [alpha]-[Cr.sub.2][O.sub.3] nanopowder.

The structural disorder produced in tetragonal KH2PO4 (KDP) single crystals are studied at room temperature by irradiation with MeV light ions. The results show that electronic energy loss plays a major role in the production of lattice defects in KDP.

Ion-bombardment produced defects are studied. The physical processes responsible for the material resistance to ion-beam disordering and amorphization are also observed.

The evolution of sheet resistance of single-crystal ZnO is studied during irradiation with 2 MeV O ions at 20 or 350 degrees C as well as during postimplantaion annealing. Results show that an increase in the dose of 2 MeV (super 16)O ions and irradiation temperature has a relatively minor effect on the thermal stability of electrical isolation.

A model for electrical isolation of GaN by light-ion bombardment is presented. The model can adequately describe experimental data for electrical isolation in the case of MeV light-ion irradiation of n-GaN.

The structural disorder that is produced in single-crystal AlN by KeV heavy - iron bombardment is studied. It is seen that AIN shows extremely strong annealing of ion-beam-generated defects during ion bombardment.

A study was conducted, by using cathodoluminescence spectroscopy, to investigate the influence of ion-beam-produced lattice defects as well as H, B, C, N, O, and Si, introduced by ion implantation, on the luminescence properties of wurtzite GaN. The results indicate that intrinsic lattice defects produced by ion bombardment mainly act as nonradiative recombination centers, and do not give rise to the yellow luminescence (YL) of GaN.

The evolution of sheet resistance of n-type GaN epilayers irradiated with MeV 1H and 12C ions is studied. It is seen that both implantation temperature (varied from 77 up to 423 K) and ion beam flux affect the process of electrical isolation in the case of irradiation with (super 12)C ions.

A simple (contactless) method to study electrical isolation in GaN for ion does above D(sub th) when the application of conventional electrical techniques is often impossible is presented. The results presented demonstrate the utility of EDS as a powerful and simple technique to study the electrical isolation in wide band-gap semiconductors.

A study on mechanisms of blistering of wurtzite GaN films implanted with H ions was conducted. The study might have significant technological implications for ion slicing and 'etching' of GaN using high-dose implantation with H ions.

Accumulation of structural disorder in Si bombarded at - 196 degrees C with 0.5 MeV (super 209)Bi(sub 1) and 1 MeV (super 209)Bi(sub 2) ions was studied by Rutherford backscattering/channeling spectrometry. Results show that the damage buildup is sigmodal even for such heavy-ion bombardment at liquid nitrogen temperature.