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Carbon ions of MeV energy were implanted into sapphire to fluences of 1×1017 or 2×1017 cm-2 and thermally annealed in forming gas (4% H in Ar) for 1 h. Secondary ion mass spectroscopy results obtained from the lower dose implant showed retention of implanted carbon and accumulation of H near the end of range in the C implanted and annealed sample. Three distinct regions were identified by transmission electron microscopy of the implanted region in the higher dose implant. First, in the near surface region, was a low damage region (L1) composed of crystalline sapphire and a high density of plateletlike defects. Underneath this was a thin, highly damaged and amorphized region (L2) near the end of range in which a mixture of i-carbon and nanodiamond phases are present. Finally, there was a pristine, undamaged sapphire region (L3) beyond the end of range. In the annealed sample some evidence of the presence of diamond nanoclusters was found deep within the implanted layer near the projected range of the C ions. These results are compared with our previous work on carbon implanted quartz in which nanodiamond phases were formed only a few tens of nanometers from the surface, a considerable distance from the projected range of the ions, suggesting that significant out diffusion of the implanted carbon had occurred. [ABSTRACT FROM AUTHOR]

We report a detailed investigation of the trapping and release of charge carriers from grain boundaries in polycrystalline diamond grown by chemical vapor deposition (poly-CVD). A model for charge trapping and release is presented for samples which display very different bulk characteristics as determined by photoluminescence, dark conductivity, and thermally stimulated current measurements. Experimental studies were performed as a function of temperature and applied electric field using ion beam induced charge to map the charge collection efficiency of charge induced by a scanned, focused, 2 MeV He+ microprobe. Even though the carrier velocity and charge collection efficiency should begin to saturate at electric fields above 1×104 V/cm, the efficiency was found to increase by a factor of 3 when the electric field is increased to greater than 1×105 V/cm. A model based on the localized enhancement of the electric field caused by trapped charge at grain boundaries is found to account for this unexpected result. Further, we find that this localized variation in electric field strongly affects charge transport in poly-CVD diamond and is therefore an important consideration for optimizing detector performance. [ABSTRACT FROM AUTHOR]

A unique detection system has been developed which allows for the counted implantation of individual low-energy heavy ions into silicon. This system can ensure the placement of individual ions at precise locations within a wafer using an EBL-machined resist mask, and utilizes the generation of ionization within the silicon substrate to allow for the reliable detection of 31 P + implants down to 14 keV. Due to the necessity for low-noise operation, it is important that both the capacitance of the detectors and their leakage current be reduced as much as possible. To this end, we have now created a detector architecture with a measured capacitance of 0.6 pF and sub-pA leakage current at liquid nitrogen temperature, which has allowed us to achieve a resolution of 410 eV (44.2 electrons RMS) when coupled to low-noise signal-processing electronics and operated at 90 K. [ABSTRACT FROM AUTHOR]

Refractive index changes induced by ion beam implantation can be used to produce photonic devices such as waveguides. Here, we relate the measured three-dimensional changes in refractive index produced by ion beam implantation to modeling of the implantation process. We use a quantitative phase microscopic method in conjunction with a tomographic reconstruction process to determine the change in the refractive index distribution within a silica optical fiber that has been selectively implanted with 2.4 MeV H+ ions. The index profile is compared with numerical simulations of the ion vacancy and ionization using the stopping range of ions in matter program. [ABSTRACT FROM AUTHOR]

Nitrogen-vacancy (NV-) color centers in diamond were created by implantation of 7 keV 15N(I=1/2) ions into type IIa diamond. Optically detected magnetic resonance was employed to measure the hyperfine coupling of single NV- centers. The hyperfine spectrum from 15NV- arising from implanted 15N can be distinguished from 14NV- centers created by native 14N(I=1) sites. Analysis indicates 1 in 40 implanted 15N atoms give rise to an optically observable 15NV- center. This report ultimately demonstrates a mechanism by which the yield of NV- center formation by nitrogen implantation can be measured. [ABSTRACT FROM AUTHOR]

We demonstrate a method for the controlled implantation of single ions into a silicon substrate with energy of sub-20-keV. The method is based on the collection of electron-hole pairs generated in the substrate by the impact of a single ion. We have used the method to implant single 14-keV 31P ions through nanoscale masks into silicon as a route to the fabrication of devices based on single donors in silicon. [ABSTRACT FROM AUTHOR]

Ion-beam-damaged diamond surfaces subjected to electron irradiation are observed to develop a pronounced negative surface charge. In this study, this effect is shown to be associated with the capture of electrons into traps created by the ion irradiation process. The trapped charge increases with ion dose and incident electron current, and decreases with increasing sample temperature and laser illumination as the traps are depleted of charge. An activation energy for detrapping of about 1.5 eV is deduced from the temperature dependence of the charging. [ABSTRACT FROM AUTHOR]

We have used the technique of ion beam induced charge with a 2 MeV He+ microprobe to image particle detectors fabricated from polycrystalline chemical vapor deposited diamond as a function of temperature. We find that detectors which display a thermally stimulated current peak at 190 °C display increased charge collection efficiency when heated above that temperature. The probability of detecting the impact of a single ion at room temperature was less than 2%, but this probability rises to over 80% at 170 °C. We model this effect by showing that charge trapped at grain boundaries is liberated at elevated temperatures and this results in an increased electric field within the detector volume and hence a raised charge collection efficiency. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]