Diffusion of boron, lithium, nitrogen, oxygen, and hydrogen into type IIa natural diamond was studied. The diffusion was performed in two steps. First, diffusion of Li and oxygen was performed in nitrogen atmosphere at 860 °C for one hour. The sample was then placed in a hot filament chemical vapor deposition (CVD) growth reactor and diffusion was performed for two hours in hydrogen atmosphere from a boron solid source placed on the surface of the sample. The condition of diffusion were those used routinely during CVD growth. After diffusion, the concentration of Li was of the order of 2×1016 cm−3 at the depth of 0.5 micrometer, and oxygen, nitrogen, and boron were found to be in the range (1–4)×1020 cm−3 at the same depth. The diffusion of hydrogen under conditions specific to CVD growth has also been studied for the first time and was found to be quite strong.
A method is proposed for the determination of the state of an impurity (donor, acceptor, or deep level) in semiconductor lattice. To demonstrate the method boron was diffused into type Ia natural diamond under a dc electric field. The concentration and diffusion profiles of boron were affected by the applied field. Boron diffuses as a negative ion since it is an acceptor shallow enough to be partially ionized at the temperature of diffusion. The drift velocity of boron ions at the temperature of diffusion was also estimated. The diffusion of lithium and oxygen from a Li,CO, source in chemical vapor deposited diamond films was performed under bias at 1000 "C in an argon atmosphere. After diffusion, the concentrations of Li, 0, and H in the diamond films were found to be around (3-4)X10*' cmm3. No dependence of these concentrations on the applied bias was observed. It was found that the diffusion of Li goes primarily through grain boundaries, which may explain why it does not depend on the applied voltage. Fluorine was present as an impurity in the dopant source. Its concentration in the films was around (1-2)X 1017 cmm3 and did depend on the applied bias, indicating that fluorine may have formed a shallow level in the diamond band gap. 0 199.5 American Institute of Physics.
10B doped diamond films grown by hot filament chemical vapor deposition were neutron irradiated at moderately high fluence levels. The as-irradiated and annealed samples, along with an unirradiated sample, were analyzed using Raman spectroscopy and x-ray diffraction. It was found that a non-diamond amorphous phase was formed on irradiation. This phase transformed back to diamond on annealing. No graphite formation was observed. A comparison with nanodiamond powder was made. A similarity between irradiated diamond films and nanocrystalline diamond powder is discussed.
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