Radiation tolerance of GaN: the balance between radiation-stimulated defect annealing and defect stabilization by implanted atoms

Realization of radiation-hard electronic devices able to work in harsh environments requires deep understanding the processes of defect formation/evolution occurring in semiconductors bombarded by energetic particles. In the present work we address such intriguing radiation phenomenon as high radiation tolerance of GaN and analyze structural disorder employing advanced co-irradiation schemes where low and high energy implants with different ions have been used. Channeling analysis revealed that the interplay between radiation-stimulated defect annealing and defect stabilization by implanted atoms dominates defect formation in the crystal bulk. Furthermore, the balance between these two processes depends on implanted species. In particular, strong damage enhancement leading to the complete GaN bulk amorphization observed for the samples pre-implanted with fluorine ions, whereas the co-irradiation of the samples pre-implanted with such elements as neon, phosphorus, and argon ions leads to a decrease of the damage.

Anomalous evolution of the ion-induced surface relief of highly oriented pyrolytic graphite

The modification of the surface of highly oriented pyrolytic graphite (HOPG) under 10, 20 and 30 keV Ar+ ions irradiation with fluence 1018 cm−2 at the irradiation temperature of 250°C has been studied experimentally. An anomalous growth of the ion-induced surface relief of HOPG have been found. This effect, like the well-known effect of anomalous deep embedded argon ions in HOPG, is analyzed within the framework of plastic deformation mechanisms in graphite.

Sputtering rate of lead, tin and germanium tellurides with low energy argon ions

Sputtering of PbTe, SnTe, and GeTe crystal samples by low-energy Ar+ ions are investigated, and the sputtering rate vsp of the studied compounds, as well as its dependence on both the composition of crystal matrix and the sputtering energy are determined. It is found that under the same conditions the sputtering rate in the sequence of GeTe-SnTe-PbTe telluride compounds increases when their average atomic weight increases. This phenomenon is explained by changes in the surface binding energy of metal atoms in lead, tin and germanium tellurides. It is shown that for all compounds the sputtering rate also increases with the increase in the sputtering energy. In the energy range from 160 to 550 eV,this increase is almost linear. The coefficients of change in the sputtering rate with energy dvsp/dE are calculated. The surface density of Ar+ ion-induced structures and the relative area of the sputtered surface covered by these structures are determined for the natural lateral surfaces of a PbTe crystal grown from melt by the Bridgman method as a function of sputtering energy. It is shown that both studied parameters decrease exponentially with increasing the sputtering energy.

THE INFLUENCE OF INTERSTITIAL IMPURITIES IN THE Zr–Y TARGET ALLOYS ON THE HEAT RESISTING CERAMIC COATING QUALITY

The influence of interstitial impurities in the Zr–Y target alloys (manufactured by two different techniques) on the quality of thermal barrier ceramic layers of heat resisting coating are studied in this work. The heat resisting ceramic coating manufactured in the UOKS-2 devices by magnetron medium-feculence plasma–chemical deposition on the surface of components that are used at the high temperatures (above 1150 °C). It was found that when the content of interstitial impurities in the target alloy is more than 0,1% (1000 ppm), the rate of the coating process decreases and has to be maintained by increasing the energy of argon ions. This leads to overheating of the target alloy and the surface of the parts (substrate) which impairs the adhesion of the deposited atoms.