Controlling the electronic properties of Er$_{\mathrm{2}}$O$_{\mathrm{3}}$ thin film by oxygen vacancies

With a high dielectric constant and wide bandgap, Er$_{\mathrm{2}}$O$_{\mathrm{3}}$ is suitable for applications in electronic and optical devices. It is known that in many oxide materials, oxygen vacancy concentration plays a decisive role in engineering the properties of the oxides. To address the oxygen vacancy concentration effects on the properties of Er$_{\mathrm{2}}$O$_{\mathrm{3}}$, here we present Scanning Tunneling Microscopy and Spectroscopy (STM/S) and X-Ray Diffraction (XRD) studies of the Er$_{\mathrm{2}}$O$_{\mathrm{3}}$ thin film made by Pulsed Laser Deposition (PLD). XRD shows Er$_{\mathrm{2}}$O$_{\mathrm{3}}$ thin film deposited at 700$^{\mathrm{o}}$C in high vacuum (HV) (sample 1) has broader peaks compared to that of the one deposited at room temperature (RT) in HV followed by 400$^{\mathrm{o}}$C annealing in air (sample 2). This indicates that, for sample 1, the loss of long range periodicity in crystal structure is mainly due to oxygen vacancies. Moreover, a relatively rough surface with 2 to 5 nm nanoclusters were observed in sample 1 by STM; while sample 2 is too resistive for STM measurements. In addition, Scanning Tunneling Spectroscopy (STS) analysis for sample 1 revealed the bandgap as well as features in the conduction band which may be related to the oxygen vacancies.