Nuclear magnetic resonance chemical shifts in CdS, CdSe, and CdTe

Abstract

Recent nuclear magnetic resonance (NMR) chemical shift measurements in111-V semiconducting compounds (1,2) have proved difficult to interpret because in a given sequence the cation shift becomes less paramagnetic with g r e a t e r covalency . For example, for the Ga7I resonance, 10 U = -3.8, -2.7, and 0 for G a p , GaAs, and GaSb, respectively, arbitrarily setting u(GaSb) = 0 (2). This i s in contrast to the situation in the rubidium and cesium halides (3,4) for which the cation shift becomes m o r e paramagnetic with g r e a t e r covalency, a s , f o r example, i s found (3) in the sequence RbF, RbCl, RbBr, and RbI for which the Rb87 shifts a r e given by 10 d = -0.6, -0.89, -1.29, and -1.49, with respect to aqueous RbC1. magnetic-field regulator and a crystal-controlled oscillator. Conduction-electron concentrations w e r e measured and frequency dependences checked to make s u r e that t r u e chemical shifts w e r e being observed. (Actuallly , slight temperature dependences w e r e found but these have not yet been studied in detail.) A cadmium nitrate solution was chosen as the reference because this salt is almost completely ionized in saturated solution.(Note that the commonly used reference salt, CdC12, has severe metal complexing in saturated solution and, in f a c t , has a paramagnetic shift of 2. I x~O -~ with respect to Cd(N0 ) . ) The Cd113 shifts, normalized to unit 3 2 field, are as follows:

77Se and125Te nuclear magnetic resonance investigations in II?VI and IV?VI compounds

“…But from all of these nuclei only a few NMR investigations with low signal-to-noise ratios are published for 113Cd (Ref. [3][4][5], 125Te (Ref. [5][6][7], 199Hg (Ref.…”