Tunneling spectroscopy has been used to detect the photoexcitation of charge carriers in the wide band-gap semiconductors, ZnO and cubic SiC. Because the process is energy sensitive, valence-toconduction hand or defect charge transfer transitions may be selectively excited and detected with the scanning tunneling microscope. Two types of transitions were detected which change the tunneling resp...

The spectral properties of LaVO(4), GdVO(4) and LuVO(4) crystals doped with Ce(3+), Pr(3+), Eu(3+) or Tb(3+) have been investigated in order to determine the position of the energy levels relative to the valence and conduction bands of the hosts along the trivalent and divalent lanthanide series. Pr(3+) and Tb(3+) ground state levels are positioned based on the electron transfer energy from tho...

The electronic structure of wurtzite InN has been investigated by electron energy loss spectroscopy ~EELS!. Spectra of the nitrogen K edge and the indium M 4,5 edge have been measured and were compared with calculated partial, N 2p and In 5p conduction band density of states in InN. Excellent agreement on the relative positions of the characteristic peaks were obtained. From low-loss EELS the b...

Besides Gaxin1_xAs with compositions nearly lattice-matched to GaAs and InP substrates both In-rich and highly strained alloys become increasingly important for heterojunction transistors and emitters also for room temperature applications. Based on deformation potential theory we first express the strain induced shifts of the conduction and valence band edges under biaxial stress. Using k·p th...

We recently reported a highly active photocatalyst, ruthenium-modified zinc oxide, which was found to be able to utilise the red part of the visible light spectrum for photocatalytic reactions [Bloh et al., Environ. Sci. Pollut. Res., 2012, 19, 3688-3695]. However, the origin and mechanism of the observed activity as well as the nature of the photoactive centres are still unknown. Herein, we ex...

Introducing intermediate band(s) within the energy gap of the semiconductor could possibly increase efficiencies of solar cells. Photons with energy less than the band gap can contribute to the device output by using the intermediate band(s) as a ‘ladder’ to the conduction band. The present analysis shows the maximum efficiency an ideal solar cell containing one and two intermediate bands can a...

We report on a new type of quantum wells with the width as thin as 10 Å, which are composed of SiC only, and consequently have ideal interfaces. These quantum wells are actually stacking faults in SiC. Certain types of stacking faults in SiC polytypes create small 3C-like regions, where the stacking sequences along the c-axis become locally cubic in the hexagonal host crystals. Since the conduc...

We characterized the conduction mechanisms in thin sputtered films of three representative binary Me–O (Me = Ta, W, and Nb) systems as a function of oxygen content, by combining in situ chemical state and electronic band structure studies from X-ray photoemission with temperature-dependent transport measurements. Despite certain differences, these amorphous films all displayed Fermi glass behav...

High-energy metal oxide surfaces are considered to be promising for applications involving surface-adsorbate electron transfer, such as photocatalysis and dye-sensitised solar cells. Here, we compare the efficiency of electron injection into different TiO(2) anatase surfaces. We model the adsorption of a carboxylic acid (formic acid) on anatase (101), (001), (100), (110) and (103) surfaces usin...

In previous work, we studied the electronic structure of several molybdate and tungstate crystals having the scheelite structure. The wolframite structure is another common form for molybdate and tungstate materials. In this paper, we compare two chemically similar materials that naturally form in the scheelite and wolframite structures—CdMoO4 and CdWO4, respectively. We compare the electronic ...