HOPPING CONDUCTION IN NANOCRYSTALLINE ZNSE FILMS DEPOSITED BY HIGH-PRESSURE DC MAGNETRON SPUTTERING

Electrical properties of nanostructured ZnSe films deposited onto quar tz substrates by high pressure (similar to 20 Pa) d.c. magnetron sputt ering technique were studied. The grain size varied within 4 to 4.4 nm with variation of deposition temperature (T-s) from 233 to 273 K. The variation oft he electrical conductivity (sigma) with temperature was measured in the temperature range of 120-240 K. The conductivity show ed (T-0/T)(p) dependence with variation of p within 0.4 to 0.6 indicat ing the presence of a Coulomb gap (similar to 0.03 eV) near the Fermi level. Efros-Shklovskii hopping (with average p=0.5) was predominant a t low temperature which changed to Mott's hopping with increasing temp erature. The existing theoretical models were used to determine the ra nge of hopping energy (0.027 to 0.037 eV) and hopping distance (4.2 to 5.8 nm) in nanocrystalline ZnSe films. Applicability of the percolati on model was tested. The effective potential barrier offered by the in tergrannular insulating region was found to increase from 0.004 to 0.0 94 eV with the decrease of grain size from 4.43 to 3.98 nm. (C) 1998 A cta Metallurgica Inc.