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IR absorption study of natural single-crystalline anatase TiO2 has been performed. It was found that as-received material reveals absorption lines at 3357.8, 3359.3, 3372.5, and 3389.3 cm−1, whose intensity grows if the sample is hydrogenated from the H2 ambient at 450 °C. In addition, hydrogenation results in the appearance of two lines at 3412.4 and 3416.9 cm−1. Isotope substitution experiments have shown that all six lines are due to the stretch local vibrational modes (LVMs) of O-H bonds, which are preferentially aligned parallel to the c-axis of TiO2. The group of LVMs at 3357.8, 3359.3, 3372.5, and 3389.3 cm−1 retains the same relative intensities and is stable against thermal treatments up to 450 °C, whereas the hydrogen-related complex(es) responsible for the 3412.4 and 3416.9 cm−1 lines disappear(s) after annealing at 250 °C. The nature of the defects resulting in these vibrational modes is discussed. [ABSTRACT FROM AUTHOR]

IR absorption study of natural single-crystalline anatase TiO2 has been performed. It was found that as-received material reveals absorption lines at 3357.8, 3359.3, 3372.5, and 3389.3 cm−1, whose intensity grows if the sample is hydrogenated from the H2 ambient at 450 °C. In addition, hydrogenation results in the appearance of two lines at 3412.4 and 3416.9 cm−1. Isotope substitution experiments have shown that all six lines are due to the stretch local vibrational modes (LVMs) of O-H bonds, which are preferentially aligned parallel to the c-axis of TiO2. The group of LVMs at 3357.8, 3359.3, 3372.5, and 3389.3 cm−1 retains the same relative intensities and is stable against thermal treatments up to 450 °C, whereas the hydrogen-related complex(es) responsible for the 3412.4 and 3416.9 cm−1 lines disappear(s) after annealing at 250 °C. The nature of the defects resulting in these vibrational modes is discussed. [ABSTRACT FROM AUTHOR]

An IR absorption study of single-crystal CdTe annealed in CdSO4 vapor at 850 °C is presented. It is shown that such a treatment results in the appearance of two absorption lines v1 and v2 at 1096.8 and 1108.4 cm-1, respectively [G. Chen et al., Phys. Rev. Lett. 96, 035508 (2006); Phys. Rev. B 75, 125204 (2007)]. Each of these features is accompanied by weaker lines. The intensities of each set of lines match the natural abundance of the sulfur isotopes. The v1 and v2 modes are assigned to the stretch vibrations of a sulfur-oxygen complex, Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed.. The number of oxygen atoms involved in Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. was deduced from the relative intensity of an IR absorption line related to the 18O isotope. [ABSTRACT FROM AUTHOR]

Interstitial hydrogen in rutile TiO2 is studied by infrared (IR) absorption. The measurements identify this defect as a shallow donor with an ionization energy of 10 ± 1 meV. The IR absorption lines at around 3290 cm-1 include local vibrational modes (LVMs) of the neutral and the positive charge states of the donor. The neutral charge state reveals two LVMs at 3288.3 and 3292.0 cm-1, whereas the positive charge state has a vibrational mode at 3287.4 cm-1. [ABSTRACT FROM AUTHOR]

Rovibrational Q(J) transitions of the interstitial H2 molecule in Si have been investigated by Raman scattering in the temperature range 90-388 K. In accordance with an earlier suggestion [ M. Hiller, E. V. Lavrov and J. Weber Phys. Rev. B 74 235214 (2006)], it is shown that the Q(2) transition of para hydrogen couples to the TAx phonon of Si and appears in the Raman spectra at temperatures above 200 K. The results presented also indicate that the rotational J=3 state of ortho hydrogen is resonantly coupled to the OΓ phonon. [ABSTRACT FROM AUTHOR]

The Zn vacancy passivated by two hydrogen atoms in ZnO (VZnH2) was studied by IR absorption. In addition to the ground state of the defect comprising two inequivalent O—H bonds aligned parallel and perpendicular to the c axis of the crystal, there exists a metastable state of the defect (VZnH2*). VZnH2* consists of two equivalent O—H bonds oriented perpendicular to the c axis. The metastable state reveals two local vibration modes at 3329.0 and 3348.4 cm-1, which represent antisymmetric and symmetric combinations of the two separate O—H stretch modes, respectively. The energy difference between the ground and the metastable states of the complex was found to be 75±9 meV. An activation energy of 0.96±0.12 eV is needed to move the hydrogen atom from the c axis to the perpendicular position. [ABSTRACT FROM AUTHOR]

A survey of recent Raman scattering studies on the interstitial hydrogen molecule (H2) in Si and GaAs is presented. It is shown that properties of H2 strongly depend on the nuclear spin state I. In either material, para-H2 (I=0) is unstable against irradiation with band gap light. In the case of Si, para-H2 also preferentially disappears from the Raman spectra in the course of storage at room temperature in the dark. Possible explanations for this surprising behavior are discussed and compared with the latest infrared absorption studies. [ABSTRACT FROM AUTHOR]