Electrical transport and optical emission of MnxZr1-xO2(≤x≤.5) thin films

Abstract

Mn x Zr 1 - x O 2 (MnZO) thin films were grown by pulsed-laser deposition on single crystalline yttria-stabilized zirconia (YSZ) and a-plane sapphire substrates with manganese contents from 0 up to about 50 at.%. A fully stabilized cubic structure occurs for Mn contents x equal or larger than 20 at. % on YSZ substrates. For x ≈0.5, phase separation of Mn-oxides occurs. Below 11 at. %, only the monoclinic phase is observed. The thin films are electrically insulating up to x = 0.3. By further increasing the Mn content or by reducing the structural quality, the resistivity ρ decreases from 3×109Ωcm down to 3×104Ωcm. For MnZO thin films on a-plane sapphire substrates, Seebeck-effect measurements verify a transition from p-type conductivity to n-type conductivity around 500 K with increasing temperature, which is probably governed by an enhanced ionic conduction. Cathodoluminescence measurements clearly show a Mn-related emission at about 2.8 eV, correlated to an Mn-induced electronic state in the bandgap of MnZO. From electron paramagnetic resonance measurements and x ray photoelectron spectroscopy, we conclude that both Mn3+ and Mn4+ is present in our MnZO thin films.