The effective surface Debye temperature of Yb:GaN

The effective Debye temperature of ytterbium and gallium in Yb:GaN thin films has been obtained using X-ray photoemission spectroscopy. The vibrational motion normal to the surface results in a dimunition of photoemission intensities from which we have estimated the effective Debye temperatures of 221±30 K and 308±30 K for Yb and Ga, respectively. The difference between the measured values for Yb and Ga suggests that the Debye temperatures are influenced by the local environment. The smaller effective surface Debye temperature for Yb correlates to a soft, strained surface, possibly due to an increased Yb―N bond length as compared to the Ga―N bond length

The surface core level shift for lithium at the surface of lithium borate

The shallow Li 1s core level exhibits a surface-to-bulk core level shift for the stoichiometric Li2B4O7(110) surface. Angle-resolved photoemission spectroscopy was used to indentify Li 1s bulk and surface core level components at binding energies -56.5 ± 0.4 and -53.7 ± 0.5 eV, respectively.We find photoemission evidence for surface states of Li2B4O7(110) that exist in the gap of the projected bulk density of states. The existence of surface states is consistent with the large surface-to-bulk core level shift for the Li 1s core

The electronic structure of Li2B4O7(110) and Li2B4O7(100)

The band structure of Li2B4O7(100) and Li2B4O7(110) was experimentally determined using a combination of angle-resolved photoemission and angle-resolved inverse photoemission spectroscopies. The experimental band gap depends on crystallographic direction but exceeds 8.8 eV, while the bulk band gap is believed to be in the vicinity of 9.8 eV, in qualitative agreement with expectations. The occupied bulk band structure indicates relatively large values for the hole mass; with the hole mass as significantly larger than that of the electron mass derived from the unoccupied band structure. The Li2B4O7(110) surface is characterized by a very light mass image potential state and a surface state that falls within the band gap of the projected bulk band structure

Surface charging at the (1 0 0) surface of Cu doped and undoped Li2B4O7

Wehave compared the photovoltaic charging of the (100) surface termination for Cu doped and undoped Li2B4O7. While the surface charging at the (100) surface of Li2B4O7 is significantly greater than observed at (110) surface, the Cu doping plays a role in reducing the surface photovoltage effects. With Cu doping of Li2B4O7, the surface photovoltaic charging is much diminished at the (100) surface. The density of states observed with combined photoemission and inverse photoemission remains similar to that observed for the undoped material, except in the vicinity of the conduction band edge

The gold and oxygen (3 × 1) structures on W(1 1 2)

The adsorption of two very different adsorbates, gold and oxygen, induce the formation of a (3 × 1) surface structure on both W(1 1 2) and Mo(1 1 2). In spite of similar adsorbate unit cells, the surface electronic structure, derived from photoemission, exhibits pronounced differences for the two adsorbates. Indeed, both experiment and simulations indicate substantial changes in electronic structures of (1 × 1) and (3 × 1) gold overlayers supported by highly anisotropic (1 1 2) plane. We speculate that (3 × 1) is a favored periodicity in the atomic rearrangement of the (1 1 2) surfaces of molybdenum and tungsten due in part as a result of the initial state band structure of these surfaces

The effective surface Debye temperature of Yb:GaN

The effective Debye temperature of ytterbium and gallium in Yb:GaN thin films has been obtained using X-ray photoemission spectroscopy. The vibrational motion normal to the surface results in a dimunition of photoemission intensities from which we have estimated the effective Debye temperatures of 221±30 K and 308±30 K for Yb and Ga, respectively. The difference between the measured values for Yb and Ga suggests that the Debye temperatures are influenced by the local environment. The smaller effective surface Debye temperature for Yb correlates to a soft, strained surface, possibly due to an increased Yb―N bond length as compared to the Ga―N bond length

Gd-doping of HfO\u3csub\u3e2\u3c/sub\u3e

An increase in the density of states between the oxygen 2p bands and the Fermi level is seen with increasing Gd concentrations. In addition, for the Gd-doped HfO2 films, the Gd 4f photoexcitation peak at 5.5 eV below the valence band maximum was identified using resonant photoemission. Electrical measurements show pronounced rectification properties for lightly-doped Gd:HfO2 films on p-Si and for heavily-doped Gd:HfO2 films on n-Si, suggesting a crossover from n-type to p-type behavior with increasing doping level. In addition, there is an increase in the reverse bias current with neutron irradiation

The surface core level shift for lithium at the surface of lithium borate

The shallow Li 1s core level exhibits a surface-to-bulk core level shift for the stoichiometric Li2B4O7(110) surface. Angle-resolved photoemission spectroscopy was used to indentify Li 1s bulk and surface core level components at binding energies -56.5 ± 0.4 and -53.7 ± 0.5 eV, respectively.We find photoemission evidence for surface states of Li2B4O7(110) that exist in the gap of the projected bulk density of states. The existence of surface states is consistent with the large surface-to-bulk core level shift for the Li 1s core