The d.c. resistance of amorphous red phosphorus has been measured up to pressures of 90 kbar. At 70 kbar, a transition to orthorhombic black phosphorus was observed. The effect of an initially inhomogeneous microstructure is discussed. At a fixed pressure, a time dependence of the resistance was observed, and this is considered to be due to a relaxation of the glass structure. The temperature dependence of the resistance at constant pressure suggests that variable-range hopping becomes the dominant conductivity mechanism as pressure is increased and an increase in the number of defect sites is responsible for the decrease of resistance. Comparison is made with the chalcogenide glasses, the tetrahedral amorphous materials and with preliminary data for phosphorus produced by chemical transport in a low-pressure hydrogen plasma. © 1981 Taylor & Francis Ltd.
