Surface charging at the (100) surface of Cu doped and undoped Li2B4O7

Abstract

We have compared the photovoltaic charging of the (1 0 0) surface termination for Cu doped and undoped Li 2 B 4 O 7. While the surface charging at the (1 0 0) surface of Li 2 B 4 O 7 is significantly greater than observed at (1 1 0) surface, the Cu doping plays a role in reducing the surface photovoltage effects. With Cu doping of Li 2 B 4 O 7 , the surface photovoltaic charging is much diminished at the (1 0 0) 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.

EPR identification of defects responsible for thermoluminescence in Cu-doped lithium tetraborate (Li2B4O7) crystals

“…Because of their lower concentrations compared to copper, it is not likely that trace amounts of other transition-metals ions are this third defect. The release of electrons over this temperature range correlates with the previously observed increase in surface conductivity of Cu-doped Li 2 B 4 O 7 [38].…”

The Electronic Structure and Secondary Pyroelectric Properties of Lithium Tetraborate

“…While the surface charging at the (100) surface of Li 2 B 4 O 7 is significantly greater than observed at (110) surface, the Cu doping plays a role in reducing the surface photovoltage effects. With Cu doping of Li 2 B 4 O 7 , while the surface photovoltaic charging is much diminished, 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 [45]. …”

“…It is possible that the Cu atoms occupying the Li sites will act as donors [45] and a more heterogeneous distribution of donor sites would account for the more gradual increase in the conduction band edge density of state away from the Fermi level seen in the inverse photoemission [45]. If either the surface or bulk donor state density increases with Cu doping then the surface photovoltaic charging should diminish compared to the undoped Li 2 B 4 O 7 (100) surfaces, as is observed.…”

Strong Metal–Sulfur Hybridization in the Conduction Band of the Quasi-One-Dimensional Transition-Metal Trichalcogenides: TiS3 and ZrS3

“…The core level XPS spectra of Figure generally provide reference binding energies to permit alignment of the various core level XAS; i.e., absent any charging, the photon energy in XAS, minus the core level binding energies, sets the placement of the conduction band minimum and states above E F , at a particular core edge. In practice, however, it is very challenging for semiconductors and dielectrics due to the potential for sample charging issues, − final state screening effects, and configuration interactions to use the X-ray photoemission binding energies, with respect to the Fermi level, to set the position of the conduction band minimum in the same core edge data in X-ray absorption. The S 2p XPS spectra for TiS 3 and ZrS 3 both show triplet-like features with peaks at 161.1, 162.3, and 163.5 eV for TiS 3 and at 161.5, 162.7, and 163.8 eV for ZrS 3 .…”