A series of gettering experiments have been carried out for a better understanding of gettering mechanism(s) in silicon. We find that oxidation and oxynitridation, which are known to inject silicon interstitials, do not getter metallic impurities such as Au, Cu, Fe, and Ni while phosphorus (P) diffusion does produce effective gettering of these metals. We also find from P diffusion, Ar ion implantation, and Ni film gettering performed as a function of temperature, there exists an optimum gettering temperature. From a comprehensive discussion of the existing models, we conclude that neither the enhanced metal solubility nor the silicon interstitial model explains our experimental results. Furthermore, it is shown that generation of dislocations is not a prerequisite for effective gettering. A model, based on the segregation of impurities at high temperatures and on the release/diffusion of metallic impurities at lower temperatures, is proposed to explain all of our results. A general form of the segregation coefficient has been developed using an extended concept of solid solubility.
The purpose of this study was to compare the bone formation around commercial sandblasted, large-grit, acid-etched (SLA)–treated titanium implants with or without a neodymium magnet in a rabbit tibia through histomorphometric analysis. Commercial SLA-treated implants with or without neodymium magnets were placed in 10 rabbits. After incising the flat part of the rabbit's tibia and installation of the specimens of titanium implants, the nonmagnet group was stitched without magnet insertion. On the other hand, the magnet group was inserted with neodymium magnet, fixed with pattern resin, and stitched. At 3 and 6 weeks after surgery, the animals were sacrificed, and the specimens were obtained. Undecalcified specimens were prepared for histomorphometric analysis of the bone-to-implant contact ratio (BIC) and bone volume (BV). The histomorphometric findings of the cortical bone showed that the mean BVs of the magnet group (3 weeks, 75.99%; 6 weeks, 82.94%) were higher than those of the nonmagnet group (3 weeks, 74.58%; 6 weeks, 78.75%), but there were no significant differences between the 2 groups (P > .05). In the marrow bone, the mean BICs of the magnet group (3 weeks, 10.36%; 6 weeks, 10.41%) were higher than those of the nonmagnet group (3 weeks, 6.41%; 6 weeks, 7.36%). After 3 weeks of installation, there was a significant difference between the 2 groups (P < .05). In rabbit tibia, the SLA-treated titanium implants with a neodymium magnet can trigger faster early peri-implant bone formation than those without a magnet.
Deep-ultraviolet (UV) light is widely used in many industries including medicine because it has sufficient energy to kill viruses and bacteria. However, deep UV with a wavelength of 254 nm can damage human cells, so it is necessary to develop a deep-UV light source with a shorter wavelength to minimize the damage to human cells while still killing viruses. The authors used a carbon nanotube-based cold-cathode electron beam (C-beam) and wide-bandgap anode to fabricate a deep-UV light source with an emission wavelength below 250 nm. The anode was fabricated by annealing ZnO ink on a Si wafer; deep UV with a wavelength of 247 nm and full width at half maximum of 23 nm was obtained. In the case of C-beam irradiation of an anode fabricated on a quartz substrate, deep UV with wavelengths of 208, 226, and 244 nm was generated through excitation with a beam energy of 7 kV and beam currents of 0.3 and 0.5 mA.
The carbon nanotube field emitter array was grown on silicon substrate through a resist-assisted patterning (RAP) process. The shape of the carbon nanotube array is elliptical with 2.0 × 0.5 mm2 for an isotropic focal spot size at anode target. The field emission properties with triode electrodes show a gate turn-on field of 3 V/µm at an anode emission current of 0.1 mA. The author demonstrated the X-ray source with triode electrode structure utilizing the carbon nanotube emitter, and the transmitted X-ray image was of high resolution.
The effect of an electron extraction electrode on electron emission for a high-performance electron beam was studied using vertically aligned carbon nanotube emitters as a cold cathode. For the lower electron emission regime (anode current less than 1 mA), the gate electrode structure and materials used had little effect on the electron emission current. However, at the higher electron emission regime (anode current higher than 1 mA), the gate electrode materials and structure do begin to deviate from an ideal Fowler–Nordheim plot by the thermal and electrostatic load on the gate electrode, especially for the small cathode area. The gate mesh bends upward under a higher current load, which then increases the gate leakage current. The upward bending in the gate mesh electrode could reduce the effective electric field by increasing the gate to cathode distance, resulting in saturation of the electron emission current. For higher electron emission currents on the anode, a gate electrode comprising a lower thermal expansion coefficient material is suitable for small cathode area electron beams.
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