Exciton and Low‐Energy Interband Structures in SrO and BaO

Abstract

Optical reflectivity data are given in the energy region 3.5 to 10 eV on freshly cleaved single crystals of SrO and BaO. The main exciton structures are interpreted in terms of two different k-space excitations one a t the zone center, the other at the edge X. Also fine structure near the SrO exciton doublet is observed.On a mesir8 la reflexion optique dans I'intervaIIe spectra1 3,5 A 10 eV de SrO et BaO monocristallins. Les cristaux ont Btb clives en vide. Le principales structures excitoniques ont Bttt interpretbes en termes de deux differentes excitations dans l'espace-k, l'une au centre de la zone, l'autre au point X. On a observe aussi line structure fine prAs du doublet excitonique du SrO.

Plasma-Assisted Atomic Layer Deposition of SrTiO3: Stoichiometry and Crystallinity Study by Spectroscopic Ellipsometry

“…Also the dielectric functions of TiO 2 and SrO films are given. The optical band gaps of the two binary oxides, ~3.3 eV for TiO 2 and >5 eV for SrO, were in good agreement with the values reported in the literature (20) (21). The dielectric functions of as-deposited STO films were homogeneously distributed between the dielectric functions of TiO 2 and SrO indicating that mixtures of the two binary oxides were deposited in the amorphous phase.…”

Logarithmic derivative reflectance spectra of BaO and SrO

“…Indeed, Fano [12] has also shown that the antiresonance is smoothed out in the presence of two or more continua. The observed reflectance spectrum of BaO just below 2800 A [5] is characteristic of Mn interband transitions, and we assign the r,-X$ interband edge a t 4.28 eV (2800 A) and obtain x 252 meV for the binding energy of the r-excitons. We have found no reasonable basis to assign the small structures observed a t 3.862 eV (IT) and 3.85 eV (IV).…”

“…The initial interpretation by Whited and Walker [3] of the low-energy set of reflectivity doublets in both MgO and CaO, was in terms of the exciton-phonon complex (EPC) initially introduced by Liang and Yoffe [6] in the interpretation of ZnO spectra. Later work by Kearney et al [5] pointed out that an EPC could not account for the similar low-energy doublet observed in their work on SrO. Their main SrO exciton structure was interpreted in terms of two different transitions (one a t I' and the other a t X ) ; it was suggested that these transitions could also account for the observed CaO and MgO structures.…”

Plasma-Assisted Atomic Layer Deposition of SrTiO3: Stoichiometry and Crystallinity Studied by Spectroscopic Ellipsometry

“…The optical band gaps of the two binary oxides, ∼3.3 eV for TiO 2 and >5 eV for SrO, were in good agreement with the values reported in the literature. 34,35 Figure 4 shows that the dielectric functions of the as-deposited STO films are all distributed in a logical compositional order, and lie between the dielectric functions of TiO 2 and SrO indicating that mixtures of the two binary oxides were deposited in the amorphous phase. The values for the refractive index n (at 1.96 eV) of all STO films deposited in the FlexAL-A reactor with different [SrO]/[TiO 2 ] cycle ratios are shown in Figure 5a and were obtained from the dielectric function values through the relations:…”