Electronic band structure of SnSe

Abstract

R. CAR et al.: Electronic Band Structure of SnSe 471 phys. stat. sol. (b) 86, 471 (1978) Subject classification: 13.1 ; 22 htitWt0 d i Fi8ic.a del Politecnico (a) and Gmppo Nazionale d i 8tmttura dells Materia del C.N.R. (a), Milano Electronic Band Structure of SnSe BY R. CAR (a), G. CIUCCI (b), and L. QUARTAPELLE (a)The electronic bands of SnSe are calculated along all high symmetry lines of the Brillouin zone using the local empirical pseudopotential method. Spectralization of the involved large matrices is performed by means of a new approximate folding-down method which locates the s-states of valence bands much better than the Lowdin-Brust perturbative technique. The parameters of the analytical form used to interpolate the pseudopotentials are roughly adjusted to obtain a band structure consistent with optical and photoelectric data. Satisfactory results for the general features are obtained, a better agreement requiring a more cautious tuning of pseudopotential values in the region of small wave vectors.Die elektronischen SnSe-Biinder werden liings der Hochsymmetrie-Linien der Brillouin-Zone nach dem ortlichen empirischen Pseudopotentialverfahren berechnet. Die Eigenwerte der betreffenden groBen Matrizen werden mit einem neuen Niiherungsverfahren berechnet, wodurch die Energiewerte der s-Zustinde der Biinder vie1 besser als mit der Lowdin-Brust-Technik ermittelt werden. Die Parameter der Pseudopotentiale werden SO gewiihlt, daB eine zu den optischen und photoelektrischen Angaben passende Bandstruktur entsteht. Es werden befriedigende Ergebnisse in dem wesentlichen Verlauf erreicht, wobei fur eine bessere Ubereinstimmung eine vorsichtigere Einstellung der Pseudopotentialwerte im Gebiet der kleinen Wellenvektoren erforderlich ist.

Reflectance and thermoreflectance spectra and energy band structure of GeSe crystals

“…However, these points are not, critical ones according to the group-theoretical analysis [23] and therefore cannot give a subst,antial contribution to t,he observed optical structures.…”

“…These structures were assumed to be caused by the direct optical transitions a t the critical points (r, U, T) and on high symmetry lines in the Brillouin zone where there are parallel segments of the valence and conduction bands. Only the lines A, V, A, B', and C' were considered, since according to the grouptheoretical analysis [23] bhey are characterized by the vanishing of the energy gradient in the perpendicular directions. The results of this analysis are given in Table 1.…”

On the band gap location and core spectra of orthorhombic IV–VI compounds SnS and SnSe

“…Parke and Srivastava [15] and Car et al [38] calculated the band structure of SnS and SnSe, respectively using a variation of the pseudopotential method, adjusting their potentials to fit experimental results; and Gashimzade [16] calculated the band structure of SnS and SnSe (and also GeS and GeSe) with a LCAO method. While all these previous calculations show rather decoupled bands, ours show a thorough mixing of bands near E F , indicating that hybridization is not to be disregarded in these systems.…”

Far ultraviolet photoelectric study of thin SnSe evaporated films

“…The discrepancies of our interpretation of structures A, and B with the position of the corresponding bands in the calculated band scheme are probably due to the inherent error of the folding down method used by the authors and to the variation of band position on account of the experimental incertitude of X-rays determination of crystal parameters used for this band calculation [26].…”

“…5 we can see the good agreement with Kemeny's [lo] UPS measurements a t 21.2 eV OR SnSe crystals. To interpret the structures appearing in the experimental valence band [lo] Braicovich (111 et al 1221 Car et al [26] ~_ _ _ _ _ When exciting with this line, the intensity ratio of valence band structures to the peak of scattered electron is high enough to make the first ones appear clearly on the spectrum, therefore, secondaries and valence band are far enough in energy to prevent superposit,ion and strong final states effects. I n our curves (Fig.…”