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The optical and electrical properties of n-type chlorine-doped Sb2Se3 single crystals, with free carrier concentrations above 1016 cm−3 at room temperature, have been studied. The experiments reveal a strongly polarized temperature-dependent long-wavelength infrared absorption attributable to conduction band electrons within the material. For wavelengths between 1.6 and 6 μm, the room temperature absorption varies as λ 2.5 ± 0.3 , suggesting that longitudinal optical mode scattering is the dominant electron scattering mechanism. The results are most consistent with the hypothesis that electron transport in Sb2Se3 is band-like and not intrinsically limited by small-polaron self-trapping. [ABSTRACT FROM AUTHOR]

The optical and electrical properties of n-type chlorine-doped Sb2Se3 single crystals, with free carrier concentrations above 1016 cm−3 at room temperature, have been studied. The experiments reveal a strongly polarized temperature-dependent long-wavelength infrared absorption attributable to conduction band electrons within the material. For wavelengths between 1.6 and 6 μm, the room temperature absorption varies as λ 2.5 ± 0.3 , suggesting that longitudinal optical mode scattering is the dominant electron scattering mechanism. The results are most consistent with the hypothesis that electron transport in Sb2Se3 is band-like and not intrinsically limited by small-polaron self-trapping. [ABSTRACT FROM AUTHOR]

This study introduces a method for creating Ohmic contacts to tin oxide (SnO2) by subjecting the sample surface to hydrogen plasma treatment at moderate temperatures of about 300 °C. This process generates a surface layer of metallic tin droplets, forming suitable electrical contacts. The contacts exhibit remarkable durability and demonstrate Ohmic behavior down to liquid helium temperatures. [ABSTRACT FROM AUTHOR]

Titanium dioxide ( TiO 2 , also known as titania) has attracted a great deal of attention since the discovery of photocatalytic splitting of water under ultraviolet light exposure by Fujishima and Honda. Three modifications of TiO 2 are known to occur in nature: rutile, brookite, and anatase, of which only the first is a stable polymorph of bulk titania. The contribution of the surface free energy, however, makes anatase a stable polymorph at the nanometer scale. Compared to rutile, anatase has a longer carrier lifetime and exciton diffusion length, higher electron mobility, and is an order of magnitude more efficient in photocatalysis, which makes it a material of choice for a variety of applications. Hydrogen is a common impurity in TiO 2 with a strong impact on its electrical and optical properties. In this Perspective, we discuss the application of IR absorption, Raman scattering, electron paramagnetic resonance, and ab initio theory to get insight into the properties of hydrogen in bulk single-crystalline anatase. In particular, interstitial hydrogen, hydrogen substituting for oxygen, the nature of "hidden" species, as well as complexes formed by hydrogen with acceptors are considered. [ABSTRACT FROM AUTHOR]

Titanium dioxide ( TiO 2 , also known as titania) has attracted a great deal of attention since the discovery of photocatalytic splitting of water under ultraviolet light exposure by Fujishima and Honda. Three modifications of TiO 2 are known to occur in nature: rutile, brookite, and anatase, of which only the first is a stable polymorph of bulk titania. The contribution of the surface free energy, however, makes anatase a stable polymorph at the nanometer scale. Compared to rutile, anatase has a longer carrier lifetime and exciton diffusion length, higher electron mobility, and is an order of magnitude more efficient in photocatalysis, which makes it a material of choice for a variety of applications. Hydrogen is a common impurity in TiO 2 with a strong impact on its electrical and optical properties. In this Perspective, we discuss the application of IR absorption, Raman scattering, electron paramagnetic resonance, and ab initio theory to get insight into the properties of hydrogen in bulk single-crystalline anatase. In particular, interstitial hydrogen, hydrogen substituting for oxygen, the nature of "hidden" species, as well as complexes formed by hydrogen with acceptors are considered. [ABSTRACT FROM AUTHOR]

A study combining vibrational spectroscopy and first-principles theory is presented for a hydrogen-related defect in natural anatase TiO 2 that is characterized by an O–H vibrational mode at 3373 cm − 1 (10 K). Based on complementary Raman scattering, IR absorption, electron paramagnetic resonance, and secondary ion mass spectrometry data supported also by ab initio calculations, it is tentatively proposed that the defect responsible for the 3373 cm − 1 line includes two hydroxyl units located next to a substitutional iron atom, Fe Ti H 2. The defect may exist in at least two charge states, whereby the 3373 cm − 1 line is associated with the positive charge state of the complex. [ABSTRACT FROM AUTHOR]

A study combining vibrational spectroscopy and first-principles theory is presented for a hydrogen-related defect in natural anatase TiO 2 that is characterized by an O–H vibrational mode at 3373 cm − 1 (10 K). Based on complementary Raman scattering, IR absorption, electron paramagnetic resonance, and secondary ion mass spectrometry data supported also by ab initio calculations, it is tentatively proposed that the defect responsible for the 3373 cm − 1 line includes two hydroxyl units located next to a substitutional iron atom, Fe Ti H 2. The defect may exist in at least two charge states, whereby the 3373 cm − 1 line is associated with the positive charge state of the complex. [ABSTRACT FROM AUTHOR]

The method of photoconductive detection of defect-related vibrational modes in semiconductors by Fano resonances is validated by a combined photoconductivity and infrared absorption study of the interstitial hydrogen donor in ZnO. Depth-resolved isotopic substitution experiments with varying concentrations of H and D show that the effect of vibrational mode-related absorption has to be taken into account in order to allow for an unambiguous interpretation of the experimental data. A quantitative model is presented which describes the influence of sample thickness, defect concentration, and the presence of other donors on the sign, magnitude, and shape of the Fano resonances. Implications for the photoconductive detection of defect-related vibrational modes are discussed. [ABSTRACT FROM AUTHOR]

Hydrogen donors in ZnO and rutile TiO2 are probed by means of photoconductivity and IR absorption. It is shown that the O-H bonds giving rise to the local vibrational modes (LVMs) of interstitial hydrogen at 3611 and 3290 cm-1 in the case of ZnO and TiO2, respectively, also occur in the photoconductivity spectra as Fano resonances. The effects of isotope substitution, concentration, sample thickness, influence of other donors present in both oxides are considered. Based on the shape and frequency of these resonances, it is concluded that the apparent ionization energy of interstitial hydrogen in rutile TiO2 is less than 300meV. By a direct comparison, we also demonstrate that photoconductive detection of LVMs of defects in thin semiconductor films is superior to the standard IR absorption. [ABSTRACT FROM AUTHOR]

Hydrogen donors in ZnO and rutile TiO2 are probed by means of photoconductivity and IR absorption. It is shown that the O-H bonds giving rise to the local vibrational modes (LVMs) of interstitial hydrogen at 3611 and 3290 cm-1 in the case of ZnO and TiO2, respectively, also occur in the photoconductivity spectra as Fano resonances. The effects of isotope substitution, concentration, sample thickness, influence of other donors present in both oxides are considered. Based on the shape and frequency of these resonances, it is concluded that the apparent ionization energy of interstitial hydrogen in rutile TiO2 is less than 300meV. By a direct comparison, we also demonstrate that photoconductive detection of LVMs of defects in thin semiconductor films is superior to the standard IR absorption. [ABSTRACT FROM AUTHOR]

Hydrogen defects in single-crystalline SnO2 are studied by combined photoconductivity and IR absorption spectroscopy. Our results indicate that a defect with an O–H local vibrational mode at 3272 cm−1 (10 K) is a donor with a level less than 300 meV below the conduction band. Annealing experiments demonstrate that the defect is stable up to approximately 450 °C and therefore may contribute to persistent n-type conductivity of SnO2. [ABSTRACT FROM AUTHOR]

An IR absorption study of hydrogen-related defects in natural single-crystalline anatase TiO2 has been carried out. A complex with IR absorption lines at 3412 and 3417 cm- 1 is shown to act as a donor with ionization energy of tens of meV. The two lines are identified as stretching local vibrational modes of the O-H bonds of the donor in the neutral and positive charge states, respectively. The defect is unstable against annealing at approximately 300 °C and a storage at room temperature on the time scale of a few weeks. These findings suggest that interstitial hydrogen is a plausible model of this defect. [ABSTRACT FROM AUTHOR]