In this paper, an experimental measurement of the diffusion constant of hydrogen in ruthenium is presented. By using a hydrogen indicative Y layer, placed under the Ru layer, the hydrogen flux through Ru was obtained by measuring the optical changes in the Y layer. We use optical transmission measurements to obtain the hydrogenation rate of Y in a temperature range from room temperature to 100 °C. We show that the measured hydrogenation rate is limited mainly by the hydrogen diffusion in Ru. These measurements were used to estimate the diffusion coefficient, D, and activation energy of hydrogen diffusion in Ru thin films to be D = 5.9 × 10⁻¹⁴ m²/s ∙ exp (-0.33 eV/k_Bτ), with k_B the Boltzmann constant and τ the temperature.

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This paper presents our latest results from the investigation of the surface oxide content in boron capped layers used as the entrance window in ultraviolet silicon (UV-Si) photodetectors. These photodetectors have been studied electrically and optically to define the correlation between oxide content and performance, i.e. the direct relationship between the amount of undesired surface oxide in the active region where the boron layer is deposited, and the detector stability to high UV exposure levels. The boron capping layers were deposited by either chemical or physical vapor based deposition techniques (CVD or PVD). Although these techniques provide photodetectors that are highly sensitive to UV radiation [1], the formation of surface oxide during deposition is a major concern, especially for stability. To analyze the oxide content, an XPS (X-ray photoelectron spectroscopy) analysis was performed on high-temperature (HT-CVD: 700 °C), low-temperature (LT-CVD: 400 °C), and room-temperature (RT-CVD: 25 °C) based pure boron (PureB) photodetectors. An inverse relationship between deposition temperature and oxide content was noticed. While the HT-CVD based photodetectors were found to contain 30% of oxide in its active region, this amount drops to less than 10% for LT-CVD, and to a few percent for RT-PVD based process.@en