The Electronic Structure and Secondary Pyroelectric Properties of Lithium Tetraborate

Abstract

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 C33D 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.

Effect of gadolinium doping on the electronic band structure of europium oxide

“…For the undoped EuO the spectra were acquired at elevated temperatures (∼400 K) to suppress residual charging, as is common in the study of dielectric oxide materials of any appreciable thin-film thickness. [19][20][21] Segregation and formation of a "surface" Gd 2 O 3 layer at the surface of the Gd-doped EuO films can be excluded as the combined photoemission and inverse photoemission are inconsistent with such an insulating (almost certainly n-type) surface oxide. 33 …”

“…Combined ultraviolet photoemission (UPS) and inverse photoemission (IPES) spectroscopies were carried out, as has been done elsewhere for both main group element compound semiconductors [19][20][21] and other rare-earth oxides. 22 Some UPS and IPES spectra were taken in a single ultrahigh vacuum chamber to study the placement of both occupied and unoccupied states under the same conditions.…”

“…The IPES spectra were obtained using variable kinetic-energy incident electrons while detecting the emitted photons at a fixed energy (9.7 eV) with a Geiger-Müller detector. [19][20][21][22][23][24] The IPES resolution was limited by an instrumental linewidth of ∼400 meV, as described elsewhere. 23,24 The angle-resolved photoemission spectroscopy (ARPES) measurements employed plane-polarized synchrotron radiation dispersed by a 3-m toroidal grating monochromator 25,26 at the Center for Advanced Microstructures and Devices (CAMD).…”

Electron and hole traps in Ag-doped lithium tetraborate (Li2B4O7) crystals

“…Upon warming, the radiation-induced trapped electrons and holes seen with EPR recombine between 100 and 200 C, in agreement with a single strong TL peak observed near 160 C. [1][2][3][4][5][6] Large high-quality single crystals with controlled doping can be readily grown and their impurity-related radiative processes can be extremely efficient. [7][8][9][10][11][12][13] Another important feature of Li 2 B 4 O 7 crystals is the presence of two isotopes ( 6 Li and 10 B) with large cross-sections for thermal neutron capture. [14][15][16][17] Crystals enriched with these isotopes may be used in applications involving neutron detection.…”

Gamma and X-ray sensitivity of Gd2O3 heterojunctions

“…The heterojunction of Gd 2 O 3 with p-type silicon forms excellent diodes, as described elsewhere ). Undoped Li 2 B 4 O 7 (001) is pyroelectric and an excellent dielectric with a wide band gap of 9.8 eV and must be doped to make it semiconducting (Adamiv et al, 2010). Here we used microcrystalline or glassy Mn doped Li 2 B 4 O 7 substrates.…”