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 off-axis pyroelectric effect observed for lithium tetraborate

We find a pyroelectric current along the {110} direction of stoichiometric Li2B4O7 so that the pyroelectric coefficient is nonzero but roughly 10−3 smaller than along the {001} direction of spontaneous polarization. Abrupt decreases in the pyroelectric coefficient along the {110} direction can be correlated with anomalies in the elastic stiffness C_33^D contributing to concept that the pyroelectric coefficient is not simply a vector but has qualities of a tensor, as expected. The time dependent surface photovoltaic charging suggests that an inverse piezoelectric effect occurs at the (110) surface but not the (100) surface. Both effects along the {110} direction or at the (110) surface are distinct the conventional as a bulk pyroelectric effect

The Minority Spin Surface Bands of CoS2(001)

Angle-resolved photoemission was used to study the surface electronic band structure of high quality single crystals of ferromagnetic CoS2 (below 120 K). Strongly dispersing Co t2g bands are identified along the 100 k direction, the ¯–¯X line of the surface Brillouin zone, in agreement with model calculations. The calculated surface band structure includes corrections for the previously determined surface structure of CoS2(001) and is in general agreement with the experimental photoemission spectra in the region of the Fermi level. There is evidence of the existence of several minority spin surface states, falling into a gap of the projected minority spin bulk CoS2(001) band structure

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

The bulk band structure and inner potential of layered In\u3csub\u3e4\u3c/sub\u3eSe\u3csub\u3e3\u3c/sub\u3e

The layered In4Se3 system does have a bulk band structure (i.e. discernible and significant band dispersion) perpendicular to the cleavage plane. Band widths (the extent of dispersion) of 300 meV or more are observed, for In-p and Se-p weighted bands within the valence region, and is indicative of a bulk band structure. Two-dimensionality of state is clearly not conserved, and there must exist interactions between layers sufficient to support a 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 Electronic Structure and Secondary Pyroelectric Properties of Lithium Tetraborate

We review the pyroelectric properties and electronic structure of Li2B4O7(110) and Li2B4O7(100) surfaces. There is evidence for a pyroelectric current along the [110] direction of stoichiometric Li2B4O7 so that the pyroelectric coefficient is nonzero but roughly 103 smaller than along the [001] direction of spontaneous polarization. Abrupt decreases in the pyroelectric coefficient along the [110] direction can be correlated with anomalies in the elastic stiffness contributing to the concept that the pyroelectric coefficient is not simply a vector but has qualities of a tensor, as expected. The time dependent surface photovoltaic charging suggests that surface charging is dependent on crystal orientation and doping, as well as temperature

The Surface Stability of CoS2(100)

The stability of various possible terminations of the CoS2 (1 × 1) surface have been explored and theoretical expectations are found to agree with experiment. With extensive annealing, there is a phase separation at the (100) surface of CoS2. Sulfur segregation to the surface leads to a significant change in the largely sulfur bands due to changes in the hybridized bands, with cobalt. Resonant photoemission spectra indicate clearly that the hybridized cobalt and sulfur bands, characteristic of the CoS2 bulk, lie at higher binding energies than those of segregated sulfur layers. This is discussed in terms of the stability of various surface structures