The spectra of the zone-centered phonons in five compounds of the AIB1%, chalcopyrite (ch) family are completed by I R absorption and Raman scattering measurements. The ch extended Keating model is applied to these phonons. The experiments and calculations clarify the assignments of the r,-modes and the low-energy modes which originate from the transverse acoustic zincblende (zb) phonons. The central force constants between nearest neighbours CXBS of the homopolar bonds are very large corresponding t o the small bond lengths. On the other hand, the strong heteropolar A-S bonds yield very low Bas-values. The model parameters, which are determined by optical phonon fitting, also reproduce in a zb approximation the elastic moduli of AgGaS,.Die Spektren der langwelligen optischen Phononen in fiinf Verbindungen der ATBIIrS,-Chalkopyritfamilie (ch) werden durch IR-Absorptions-und Ramanmessungen vervollstandigt. Das ch-erweiterte Keating-Model1 wird auf diese Phononen angewendet. Die Experimente und Berechnungen klaren die Bestimmungen der I',-Moden und der niederenergetischen Moden, die von den transversal-akustischen Zinkblendephononen (zb) abgeleitet werden. Die zentralen Kraftkonstanten ~g s zwischen nachsten Nachbarn der homopolaren Bindungen sind sehr groB, was mit den kurzen Bindungslangen iibereinstimmt. Auf der anderen Seite liefern die stark heteropolaren A-S-Bindungen sehr niedrige aAS-Werte. Die Modellparameter, die durch Anpassung der optischen Phononen bestimmt werden, geben die Elastizitatskoeffizienten von AgGaS, in der zb-Naherung richtig wieder.
Rhumb.-Les phonons optiques (k-0) de CuInS2, AgInS2 et CuFeS, ont ete analyses par des mesures d'absorption et de reflexion dans la region de 1 000 jusqu'a 50 cm-1. La determination des frequences des phonons optiques transversaux et longitudinaux a et6 effectuk B I'aide dqCquations Kramers-Kronig ainsi que de modtles classiques d'oscillateurs. Les rksultats sont cornparks aux spectres connus de CuAIS,, CuGaS2 et AgGaS2. Une comparaison systematique des frequences des modes montre quc les constantcs de force des differents coniposes 1-111-S2 sont presque egales. Les differences des frequences des modes correspondants paraissent dependre principalement des differentes masses des cations.
The electronic properties of thin CdSe films prepared through physical vapor transport were investigated using photoluminescence (PL) and electronic measurements. The films were studied at each of the main preparation steps, i.e., evaporation, annealing, etching, and finally photoetching. At 3 K two distinct donor-acceptor (DA) transitions at 1.75 and 1.70 eV were found in the photoluminescence spectra in addition to deep states at about 1.55 eV at 20 K. These DA transitions which are produced mainly during the evaporation might be associated with group VII and with alkali metal impurities. After each preparation step the DA transitions change their intensities. It is shown that photoetching of the films leads to a removal of the deep centers, while the 1.75 eV transition is blue shifted. In contrast with single-crystal CdSe the intensity of the PL increases after photoetching. The results of the PL are consistent with the electronic measurements. They are explained in terms of a previously published model.
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