Papers by Keyword: Heavy Water

Abstract: The IR absorption spectra of hexagonal crystals of lithium iodate α-LiIO₃, used in laser shutters for ship wiring, where the quality, transparency and power of laser radiation are of great importance, are studied. The transmission spectra allowed us to determine the width of the crystal band gap 4.37 eV along the Z-axis (C₆ [0001]) and 4.46 eV along the axis perpendicular to the Z axis. The activation energies and the wavelength of the vibrational centers associated with the vibrations of the H₃O⁺, OH^-, H₂O groups, heavy D₂O and semi-heavy molecules HDO are determined. It is established that the band 1450-1650 cm^-1 is a superposition of at least two broad absorption maxima centered at ~1550 and ~1600 cm^-1. It was experimentally established that the ratio of the absorption coefficients of these bands was ~1:1 (75:74 cm^-1) for crystals grown in H₂O, and ~2:1 (161:84 cm^-1) – for crystals grown in D₂O. This allows us to assume that in a lithium iodate crystal grown in D₂O, the bands 1550 cm^-1 and 1600 cm^-1 correspond to the vibrations of the bound HDO and H₂O molecules, the band 1150 cm^-1 corresponds to the vibrations of heavy water molecules. The results of the study allowed us to propose a mechanism of transport and translational diffusion of protons and to determine the presence of heavy water molecules in crystalline materials, as well as to diagnose the quality of laser crystals.

Abstract: The well known wet chemical treatments of the silicon surface and its native oxidation in air cause a high density of interface states, which predominantly originate from dangling bonds strained bonds or from bonds, between adsorbates and silicon surface atoms. Therefore, a number of wet-chemical treatments have been developed for ultraclean processing in order to produce chemically and electronically passivated surfaces [1]. The saturation of dangling bonds by hydrogen removes the surface states and replaces them by adsorbate-induced states, which influence the surface band-bending [2]. The first thermal hydrogen desorption peak from a hydrogen passivated Si surface in vacuum or inert gas ambient can be detected at around 380°C [3,4]. Simultaneously the combination of the hydrogen atoms of neighboring dihydrides generates a pair of dangling bonds. At around 480-500°C dangling bonds are generated on the silicon surface by desorption of the remaining hydrogen [5]. At that moment the silicon surface becomes extremely reactive.

Abstract: The high reactivity of the free silicon surface and its consequence: the “omnipresent” native silicon dioxide hinders the interface engineering in many processing steps of IC technology on atomic level. Methods known to eliminate the native oxide need in most cases vacuum processing. They frequently deteriorate the atomic flatness of the silicon. Hydrogen passivation by a proper DHF (diluted HF) treatment removes the native silicon oxide without roughening the surface while simultaneously maintains a “quasi oxide free” surface in a neutral or vacuum ambient for short time. Under such circumstances the last thermal desorption peak of hydrogen is activated at around 480-500°C where the free silicon surface suddenly becomes extremely reactive. In this study we show that deuterium passivation is a promising technology. Due to the fact that deuterium adsorbs more strongly on Si surface than hydrogen even at room temperature, deuterium passivation does not need vacuum processing and it ensures a robust process flow.