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The effect of irradiation by a hyperthermal-atomic-oxygen beam on hydrogenated titanium-doped diamond-like carbon (hydrogenated Ti-DLC) films, applied as a solid lubricant for equipment used in low-earth orbit was investigated. Unlike the film thickness of hydrogenated non-doped DLC films, that of hydrogenated Ti-DLC films was found to be constant after the films were exposed to atomic oxygen. In addition, bulk composition of the hydrogenated Ti-DLC film stayed constant, and in particular, hydrogen content in the film did not decrease. These results indicate that a hydrogenated Ti-DLC film can keep its low friction properties under vacuum. Surface chemical analysis showed that a titanium-oxide layer is form on the film by exposure to atomic oxygen. The thickness of the titanium oxide layer was estimated to be about 5 nm from the element distribution in the depth direction of the hydrogenated Ti-DLC films. The titanium-oxide layer was interpreted to protect the bulk film from erosion by hyperthermal atomic oxygen.

We investigated a modification process for highly hydrogenated diamond-like carbon (H-DLC) film using exposure to synchrotron radiation (SR) in the soft X-ray region by measuring the dependence of various film properties and structural properties on the SR dose. Noticeable changes in the film volume and optical constants were observed, and the local structures of the H-DLC film changed due to SR exposure. These changes are ascribable to the desorption of hydrogen from the film, which is much faster than when the film is etched. [ABSTRACT FROM AUTHOR]

The authors have investigated the electrical characteristics of hydride vapor-phase epitaxy GaN films exposed to Arþ irradiation, employing Schottky barrier diodes. The Ar+ irradiation tends to largely increase the effective carrier concentration in the near surface region of GaN up to ~25 nm, due to the generation of donor-type N vacancy defects, compared to the original value before the irradiation. More interestingly, acceptor-type deep-level defects are found to be formed at ~2.1, ~2.9, and ~3.2 eV below the conduction band in the subsequently deeper region, in which Ga vacancies introduced by the Ar+ irradiation are considered to be in-diffused and immediately combined with hydrogen. These N vacancies and hydrogenated Ga vacancies formed are dominantly responsible for changing the depth profiles of the effective carrier concentration via the carrier generation, the carrier trapping, and/or carrier compensation. [ABSTRACT FROM AUTHOR]

Near edge x-ray absorption fine structure (NEXAFS) spectra of plasma-etched TiO2 thin films were observed using the total fluorescence yield method involving visible emission. The disrupted spectrum recovered its as-grown (nonetched) profile, upon soft x-ray (SX) irradiation. This recovery was investigated by ultraviolet (UV) irradiation, spatial distribution measurements, exposing recovered samples to air, and NEXAFS measurements of ultrafine TiO2 particles. The spectral profile recovered upon UV irradiation, and at sample positions outside of the SX irradiation site. The recovered spectral profiles were disrupted again, upon exposure to air. Nonetched ultrafine TiO2 particles also exhibited a disrupted spectral profile, which was recovered upon SX irradiation. The spectral recovery is explained by a model involving electrons trapped in oxygen vacancies generated by etching. [ABSTRACT FROM AUTHOR]

We have investigated the generation of electrical damage in n-GaN films following treatment in a CF4 plasma, employing capacitance–voltage and steady-state photocapacitance spectroscopy techniques. The effective carrier concentration at depths of 50–150 nm from the GaN surface decreases, probably owing to Ga vacancies (VGa) diffusing into the bulk after being introduced at the surface by ion bombardment. These vacancies consequently form acceptor-type hydrogenated VGa with optical onsets at ∼1.79 and ∼3.23 eV below the conduction band. In particular, the dominant 3.23 eV level is most likely attributed to (VGa–H2)− species, because the VGa concentration at depth is very low. [ABSTRACT FROM AUTHOR]

Hydrogenated amorphous silicon carbide films have been fabricated by the decomposition of hexamethyldisilane with a microwave discharge flow of Ar. Mechanically hard films were obtained by applying radio-frequency (RF) bias voltages to the substrate. The atomic compositions of the films were analyzed by a combination of Rutherford backscattering and elastic recoil detection, X-ray photoelectron spectroscopy (XPS), and glow discharge optical emission spectroscopy. The chemical structure was analyzed by carbon-K near-edge X-ray absorption fine structure spectroscopy, high-resolution XPS, and Fourier transform infrared absorption spectroscopy. The structural changes upon the application of RF bias were investigated, and the concentration of O atoms near the film surface was found to play a key role in the mechanical hardness of the present films. [ABSTRACT FROM AUTHOR]

The generation behavior of deep-level defects in Ar+-irradiated GaN has been investigated by photoluminescence, capacitance–voltage, and photocapacitance techniques. Ar+ irradiation induces a significant increase in near-band edge emission peak intensity due to donor-bound excitons, in agreement with the largely increased effective carrier concentration in a shallow-lying region near the surface. More interestingly, with increasing irradiation time, the carrier concentration tends to decrease in a deep-lying region, compared with that in the inner bulk region, which is considered to stem from carrier trapping and/or carrier compensation via the diffusion and formation of acceptor-type deep-level defects, such as Ga vacancies and residual C. [ABSTRACT FROM AUTHOR]