ELECTRICAL AND OPTICAL PROPERTIES OF UHV SUBLIMED a-As

Abstract
Thin films of amorphous arsenic have been prepared by sublimation on to substrates held at ~ 100 K in ultra high vacuum. Annealed films show an optical bandgap of ~1.0 eV. Low temperature ion bombardment greatly enhances the de conductivity, which after bombardment follows the T^-¼ law. Interpretation in terms of variable range hopping leads to a Fermi level density of states after bombardment of ~5 x 10¹⁷ eV^-1 cm^-3, which falls to ≤ 10¹⁷ eV^-1 cm^-3 after annealing at 295 K. Comparison with similar experiments on amorphous r.f. sputtered phosphorus lends support to those models of defect states which suggest that charged defects are more stable in a-P than in a-As.