Photocurrent Characteristics for Mn-doped Barium Titanate Ferroelectric Single Crystals

Abstract

We investigated the photocurrent characteristics for ferroelectric single crystals of non-doped barium titanate (BT) and Mn-doped barium titanate (Mn-BT). The introduction of 90 ° domain structures into the BT crystals markedly raised the photocurrent, which suggests that the separation of photoinduced carriers is significantly enhanced around 90 ° domain walls (DWs). The Mn doping led to a drastic increase in the photocurrent, with photon energy less than the band gap. Density functional theory calculations show that the large photocurrent observed for the Mn-BT crystals originates from the electron excitation from the O-2p valence band to the Mn-e_g defect level followed by the carrier (hole) injection.