Fermi-Level Pinning and Barrier Height Control at epitaxially grown ferromagnet/ZnO/metal Schottky Interfaces for opto-spintronics applications

Abstract

Schottky contacts (SC) at the ferromagnet/ZnO interface are good candidates for the realization and control of several semiconductor emerging magnetic phenomena such spin injection and spin-controlled photonics. In this work, we demonstrate the epitaxial growth of single-phase and wurtzite-ZnO thin films on fcc Pt/Co$_{0.30}$Pt$_{0.70}$ (111) electrodes by MBE technique. While the magnetic properties of the Pt/Co$_{0.30}$Pt$_{0.70}$ buffer remain unchanged after the ZnO growth, the electric measurements of back-to-back Schottky diodes revealed a Schottky barrier height at the metal/ZnO interfaces in the range of 590-690 meV using Cu, Pt and Co$_{0.30}$Pt$_{0.70}$ contacts. A pinning factor S and a charge neutrality level (CNL) ${\Phi}_{CNL}$ of 0.08 and 4.94 eV, respectively, were obtained indicating a strong Fermi-level pining with a CNL level that lies 0.64 eV below the conductance band of ZnO semiconductor. These experimental findings indicate that Co$_{0.30}$Pt$_{0.70}$/ZnO interface follows the metal-induced gap states model and can open a pathway for the realization of opto-spintronics applications such spin-LEDs.