Band gap determination using absorption spectrum fitting procedure

Comprehensive modeling of the band gap and absorption spectrum of BiVO4

We present first-principles calculations of the electronic structure of BiVO4 at various levels of theory. In the calculations, we take into account a series of effects that affect the band gap, i.e., spin-orbit coupling, electron-hole interaction, nuclear quantum motions, and thermal vibrations. All these effects lead to a significant renormalization of the band gap. After including the releva...

Band gap reduction in InNxSb1-x alloys: Optical absorption, k

Energy band-gap dependence of two-photon absorption.

We present measurements of the two-photon absorption coefficients beta(2) of 10 different semiconductors having band-gap energies between 1.4 and 3.7 eV. We find that beta(2) varies as E(g)(-3), as predicted by theory. In addition, the absolute values of beta(2) agree with theory, which includes the effect of nonparabolic bands, the average difference being less than 26%. This agreement permits...

Measurement of Orthopositronium Decay Rate Using SiO2 Powder: Integration of Thermalization into Time Spectrum Fitting Procedure

The intrinsic decay rate of orthopositronium (o-Ps) formed in SiO2 powder was measured using a modified method which determined the time dependence of the pick-off annihilation rate using high-energyresolution germanium detectors. That is, the main systematic error due to thermalization was accounted for and integrated into the time spectrum fitting procedure. The averaged value was found to be...

Band-Gap Structure of the Spectrum of Periodic Maxwell Operators

We investigate the band-gap structure of some second-order differential operators associated with the propagation of waves in periodic two-component media. Particularly, the operator associated with the Maxwell equations with position-dependent dielectric constant e(x), x e R 3, is considered. The medium is assumed to consist of two components: the background, where e(x)= eh, and the embedded c...