Nuclear quadrupole resonance study of the glassy As xSe 1− x system

Abstract

Nuclear quadrupole resonance (NQR) of 75 As has been used to study the local bonding structure of glassy arsenic–selenium systems. We have studied the glassy system As x Se 1− x with x=0.08, 0.15, 0.27, 0.32, 0.36, 0.40, 0.50, and 0.60 using 75 As NQR at liquid nitrogen temperature (77 K). The 75 As NQR spin-echo spectra from x=0.08 up to x=0.40 each consist of a single broad line. As the concentration of arsenic increases, the positions of the peaks decrease approximately linearly from 63 MHz at x=0.08 to 58 MHz at x=0.40. For x=0.50, the spectrum, consists of a very broad asymmetric peak near 81 MHz. The spectrum for x=0.60 consists of three well-resolved, narrow peaks, but otherwise extends over a similar frequency range as that of x=0.50. By comparison with NQR spectra that occur in crystalline arsenic–selenium compounds, these three peaks have been interpreted as due to three fold co-ordinated, pyramidal arsenic sites with, varying numbers of arsenic–arsenic bonds.