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The (004) X-ray rocking curves of undoped and boron doped homoepitaxial diamond films have been recorded up to 8 × 10 20 [ B ] cm −3 . Up to this concentration the films grew coherently, i.e. the in-plane lattice constant of the doped film is the same as that of the substrate. The lattice constants of the boron doped diamond films in their relaxed state have been determined. Boron incorporation induces a large expansion of the lattice constants, especially above the semiconductor-metal transition. We suggest a contribution of both the different size of boron and carbon atoms (Vegard's law) and of hole concentration in the impurity band of boron [with a positive deformation potential of the impurity band of boron of 16 (± 0.3) eV] to describe the experimental results.

Electrochem. and phys. properties of polycryst. B-doped diamond electrodes with a metallic conduction grown by MPCVD and HFCVD were studied with the goal to use them as cathodes, for the electrochem. redn. of nitrate in neutral solns. All electrodes contain a mean B concn. [B] >3 * 1020/cm3 and show a significant redn. of nitrate. However, the higher efficiency is obtained for the electrode having the highest [B] (1.5 * 1021/cm3) and the lowest concn. of parasitic phases. The anal. of the Raman spectrum proved to be a valuable tool to probe these characteristics. Quant. anal. of the solns. showed that the relative concns. of the nitrogenous species formed during the redn. of nitrates at -2 V do not depend on the B doping level. [on SciFinder (R)]

CVD diamond shows promising properties for use as a position sensitive detector for experiments in the highest radiation areas at the Large Hadron Collider. In order to study the radiation hardn ess of diamond we exposed CVD diamond detector samples to 24~GeV/$c$ and 500~MeV protons up to a fluence of $5\times 10^{15}~p/{\rm cm^2}$. We measured the charge collection distance, the ave rage distance electron hole pairs move apart in an external electric field, and leakage currents before, during, and after irradiation. The charge collection distance remains unchanged up to $1\ times 10^{15}~p/{\rm cm^2}$ and decreases by $\approx$40~\% at $5\times 10^{15}~p/{\rm cm^2}$. Leakage currents of diamond samples were below 1~pA before and after irradiation. The particle indu ced currents during irradiation correlate well with the proton flux. In contrast to diamond, a silicon diode, which was irradiated for comparison, shows the known large increase in leakage curren t. We conclude that CVD diamond detectors are radiation hard to 24~GeV/$c$ and 500~MeV protons up to at least $1\times 10^{15}~p/{\rm cm^2}$ without signal loss.

Though no boron signal is identified, with respect to their boron content the narrow and broad components of the electron spin resonance signal in boron doped polycrystalline film decrease from 1018 to 1016 cm−3. This is ascribed to two different structural defects with concentration decreasing with the boron content, in agreement with theoretical predictions. Finally, we suggest a spatial location for these defects.

The relationship between variable range hopping (VRH) below 300 K and the defects created during 1013–1016 cm−2 boron ion implantation at 77 K in as-implanted diamond films and films annealed at 800 °C is investigated with the help of electron spin resonance (ESR) and optical measurements. The onset Dp = 2 × 1015 cm−2 of the VRH conduction is attributed to a percolation threshold, and is lower than the amorphization dose Da = 4 × 1015 cm−2. From ESR and optical absorption, implantation creates sp3 carbon dangling bonds (paramagnetic and which act as hopping centres) below Dp and sp2 bonds (which cause metallic conduction and optical absorption) above Da. The hopping conduction takes place between localized levels from sp3 carbon dangling bonds, but only a small proportion of the sp3 defects participates in this conduction.

We present experimental investigations of the structural and electrical properties of carbide contacts on homoepitaxial p-type diamond films in order to achieve Schottky diodes working at high temperatures with highly adhesive ohmic and Schottky contacts on diamond. For ohmic contacts, the reaction of molybdenum deposited by magnetron sputtering on homoepitaxial diamond layer is studied through X-ray diffraction and Rutherford backscattering. The formation of hexagonal α-Mo2C begins at 700 °C. However, the residual oxygen is exodiffused only at 900 °C and for undoped diamond. Nevertheless, ohmic contacts are achieved after annealing at 900 °C, with a low contact resistivity at a boron concentration of 1.6×1021 cm−3. For Schottky contacts, the in-situ reaction under ultra-high vacuum between Er and a non-oxidized diamond surface begins at 700 °C. A potential barrier height of 1.9 eV and a rectification ratio larger than 103 at 4 V at least up to 500 °C are obtained. In each case, coating layers intended to protect carbides against oxidation are assessed.

We report on the optical properties of a‐Si : H prepared by cathodic sputtering of a Si target in an 80% argon/20% hydrogen reactive gas at ∼9×10−3 Torr. The deposition rate φ (by means of the rf voltage) and the substrate temperature were varied. The total hydrogen content [H] and the concentration of hydrogen involved in SiH bonds [H1] or in SiH2 bonds [H2] were measured. We find [H]≳[H1]+[H2], two times higher in some preparation ranges (ν?15 A/min or ν=100 A/min), which implies the occurrence of hydrogen atoms H′ not bonded in the usual SiH or SiH2 forms. The optical absorption coefficient, the optical energy gap E0, and the refractive index ns were measured. E0 decreases as v increases, is independent of Ts for φ≳30 A/min, and decreases as Ts increases for v≳30 A/min. ns increases toward the crystalline value as φ increases and Ts decreases. The similarity of the properties of the layers obtained by sputtering and glow discharge is emphasized. We suggest equilibrium between hydrogen bonds as SiH and ...