Nuclear quadrupole resonance study of the glassy AsxSe1-x system

Nuclear quadrupole resonance (NQR) of As-75 has been used to study the local bonding structure of glassy arsenic-selenium systems. We have studied the glassy system AsxSe1-x with x = 0.08, 0.15, 0.27, 0.32, 0.36, 0.40, 0.50, and 0.60 using As-75 NQR at liquid nitrogen temperature (77 K). The As-75 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. (C) 2002 Elsevier Science B.V. All rights reserved.