Investigation of dark and light conductivities in calcium doped bismuth ferrite thin films

摘要

Electrical conductivities in dark and light were investigated in Calcium doped Bismuth Ferrite thin films. Higher dark conductivity, in the order of 10 times higher than conductivity of bismuth ferrite, was observed for Bi_(0.85)Ca_(0.15)FeO_(3-δ). Structural analyses using Rietveld refinement showed a deviation from volume reduction for Bi_(0.85)Ca_(0.15)FeO_(3-δ) which could be the reason of abnormally high conductivity for this compound. Although higher calcium doping reduced conductivity, photoconductivity was observed again. Atomic Force Microscopy investigations showed that surface roughness and grain size decreased with increasing calcium concentration. Enhanced photoconductivity is reported for Bi_(0.7)Ca_(0.3)FeO_(3-δ) with -2.8 eV direct optical band gap at 300 K with surface roughness of -2 nm.