[en] The effects of scanned 2 MeV He⁺ and 1.4 MeV H⁺ microbeam irradiation on unimplanted and P implanted diamond are discussed. Although diamond was found to be resistant to lattice defect production, it was found to swell very rapidly in comparison with other materials, giving rise to serious swelling induced dechanneling at scan edges at relatively low doses (10¹⁷/cm² for 2 MeV He⁺). Microbeams annealed the damage due to a 1.5 μm deep Phosphorus implantation at a dose of 10¹⁵P⁺/cm². The implantation damage was reduced at a dose of (1.6 x 10¹⁷/cm²) by up to 21 % for 2 MeV He⁺ irradiation, up to 16% for high flux 1.4 MeV H⁺ irradiation and 12% for low flux H⁺ irradiation. For the choice of analysis beam, all these beam effects were found to be most significant for He⁺ microbeams, so H⁺ microbeams should be used for analysis of diamond unless high depth resolution is required. 13 refs., 10 figs

[en] A simple quantitative model is derived to describe the change in X_min of crystal irradiated by MeV energy light ions in a channelling orientation. This model treats the buildup of crystal damage as a simple competition between interstitial/hole creation by the beam and annealing of these defects, and implies that an equilibrium damage condition will be reached. This equilibrium point is dependent on the flux. Fits to microprobe damage data show that the qualitative features of this model are observed in GaAs. One of the implications of this model is that microprobe analysis at low incident fluxes may cause far less damage than the results of damage studies performed with small scans at high incident fluxes suggest. 5 refs., 2 figs

[en] Beam induced swelling was found to be the most significant cause of dechannelling for H^e+ and H⁺ microprobe measurements of the crystallinity of single crystals for irradiated regions of sizes typical of microprobe scans (∼ 100 x 100 μm²). Swelling causes tilting the crystal axis at the edge of the irradiated region, as the surface layers must be tilted to accomodate the height difference. Dechannelling is due to point defect creation, but swelling induced misalignment is an additional mechanism. The tilting of the axis causes significant dechannelling when the tilt reaches a few tenths of a degree. The results of this study show that the dechannelling produced by the surface swelling had a significant effect on the results of previous MeV energy He⁺ ion beam damage studies on silicon carried out with high doses. All previous studies were carried out with small regions of irradiation (size < 100 μm) where the present study shows that swelling induced misalignment is the dominant dechannelling mechanism. It is concluded that the effect of dechannelling due to swelling at the edge of the irradiated region is not significant for large scans or low doses used in routine analysis. Also the use of lower beam current and target heating increase the relative rate of annealing of point defects. Such strategies allows higher doses to be used than those suggested from a simple extrapolation of the results of damage studies carried out with high fluxes on regions of a few tens of microns. 7 refs., 4 figs

[en] Raman spectroscopy was found to be sensitive to the presence of these specific defects and also to the overall level of damage produced in the sample when diamond was implanted with doses in the range of 10¹⁶-10^l8 ions/cm² H or He with energies greater than 1 MeV. The main series of experiments discussed herein used 1x10¹⁶ -3x10¹⁷ ions/cm² of 3.5 MeV He⁺. Use of a geometry in which ions were implanted into the edge of a diamond slab allowed the damage to be measured as a function of distance along the ion track by both Channeling Contrast Microscopy (CCM) and Raman spectroscopy. 1 refs., 1 fig

[en] Raman microprobe measurements of ion implanted diamond and silicon have shown significant shifts in the Raman line due to stresses in the materials. The Raman line shifts to higher energy if the stress is compressive and to lower energy for tensile stress¹. The silicon sample was implanted in a 60 μm square with 2.56 x 10¹⁷ ions per square centimeter of 2 MeV Helium. This led to the formation of raised squares with the top 370mm above the original surface. In Raman studies of silicon using visible light, the depth of penetration of the laser beam into the sample is much less than one micron. It was found that the Raman line is due to the silicon overlying the damage region. The diamond sample was implanted with 2 x 10¹⁵ ions per square centimeter of 2.8 MeV carbon. It was concluded that the Raman spectrum could provide information concerning both the magnitude and the direction of stress in an ion implanted sample. It was possible in some cases to determine whether the stress direction is parallel or perpendicular to the sample surface. 1 refs., 2 figs

[en] Short communication. 1 fig

[en] High energy ion implants in semiconductor materials have been analyzed by Channeling Contrast Microscopy (CCM) perpendicular to the implant direction, allowing imaging of the entire ion track. The damage produced by Channeled and Random 1.4 MeV H⁺ implants into the edge of a <100> type IIa diamond wafer were analyzed by channeling into the face of the crystal. The results showed negligible damage in the surface region of the implants, and swelling induced misalignment at the end of range of the implants. Channeled 1.4 MeV H⁺ implants in diamond had a range only 9% deeper than Random implants, which could be accounted for by dechanneling of the beam. The channeling of H⁺₂ ions has been previously found to be identical to that of protons of half energy, however the current experiment has shown a 1% increase in χ_min for H⁺₂ in diamond compared to H⁺ at 1,2 MeV per proton. This is due to repulsion between protons within the same channel. 5 refs., 2 figs

[en] Beam induced swelling can be the most significant cause of dechannelling for He⁺ and H⁺ microprobe measurements of the crystallinity of single crystals for irradiated regions of sizes typical of microprobe scans (∝100x100 μm²). Swelling causes dechannelling by tilting the crystal axis at the edge of the irradiated region. The present work shows that this effect only becomes significant, relative to dechannelling from beam induced point defects, above a threshold dose, D_s, For 2 MeV He⁺ incident along the <100> axis of Si, D_s is ∝2x10¹⁷/cm² and D_s is ∝4x10¹⁷/cm² for GaAs. Since swelling induced dechannelling is confined to the edge of the irradiated area, increasing the beam scan size is a useful means of minimizing its effect on χ_min measurements of small regions of crystal. (orig.)

[en] Short communication

[en] The dose and flux dependence of H⁺ and He⁺ ion beam damage on Hg_0.5Cd_0.5Te (MCT) grown on a GaAs substrate by Metal Organic Chemical Vapour Deposition has been examined using a nuclear microprobe at the University of Melbourne. For this study the accumulation and measurement of damage was performed in the <100> channeled orientation. Ion beam characterization in the channeled orientation provides quantitative information on crystalline materials, therefore it is the damage buildup in this alignment which is most important. The measurements presented are expected to provide a basis for guidelines for the appropriate dose and flux to be used in the channeling analysis of MCT. 9 refs., 5 figs