The off-axis pyroelectric effect observed for lithium tetraborate

Abstract

We find a pyroelectric current along the 110 direction of stoichiometric Li 2 B 4 O 7 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 D 33 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.

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

“…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).…”

“…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 …”

“…It should be noted that Gd 2 O 3 is typically n-type in thin-film form and forms a heterojunction diode with p-type Si(100), but no negative differential resistance has been observed with such structures. 33 Heterostructures of Gd 2 O 3 with Si(100) show diode characteristics 19 …”

The Electronic Structure and Secondary Pyroelectric Properties of Lithium Tetraborate

“…In other words, the dispersion of the valence bands should be small compared to the expected dispersion of the conduction bands. Only recently [5,7] has there has been experimental confirmation of any of the key predictions of the calculated band structure, beyond the band gap [5,7,16,17,18] and some of the optical properties [15]. …”

“…After corrections for photovoltaic charging (as discussed later ( vide infra ) and elsewhere [5,7,16,17,18]), we place the Li 1s shallow core level binding energies at −56.7 ± 0.4 to −56.5 ± 0.4 eV depending on the surface termination (crystal orientation). These values are largely dominated by the bulk Li 1s core level binding energy contributions because of the normal photoelectron emission geometry.…”