Some properties of metal-free amorphous phthalocyanine vacuum deposited films

Abstract

Amorphous metal free phthalocyanine films have been prepared by vacuum deposition of the powder onto quartz substrates cooled to liquid nitrogen temperatures. X-ray diffraction and differential thermal analysis have been used to study the crystallization (occurring between 325 and 410 K) to the α-phase and the subsequent irreversible phase change from the α- to the β-phase, near 480 K. Silver ohmic contacts with sandwich samples were used to study the I–V characteristics of amorphous phthalocyanine and the temperature dependence of the conductivity. Space charge limited currents with carrier densities of ~109 cm−3 and trap densities of ~1016 cm−3 are observed and the conductivity activation energy in the bulk is ~1.24 eV. Surface currents and surface traps were observed in planar samples and these dominate the bulk properties, for this geometry.