Highly uniform 2d growth, substrate transfer, and electrical characterization of electrodeposited ZNO thin films

Highly uniform and truly 2D ZnO thin films have been obtained in an electrochemical process by simply adding methanol to the standard aqueous zinc nitrate electrolyte. Cyclic voltammetry analysis indicates methanol modifies the electrochemistry and enhances the nitrate reduction electrochemical reaction as well as the initial nucleation process. The improved electrochemistry alters the dominant crystal formation by allowing the spaces in between ZnO structures to more readily utilize Zn²⁺ and OH^- ions, increasing their lateral growth - i.e. 2D rather than 3D formation. The well-formed ZnO thin films were then transferred to a secondary substrate, enabling isolated electrical characterization via resistivity and Hall effect measurements. These electrical measurements were combined with and compared toMott-Schottky analysis of films remaining on their conductive growth substrate. All of the electrical characterization indicates the as grown, undoped ZnO films are n-type with high resistivities and low carrier concentrations under most growth conditions. This work helps to open up avenues toward device applications with electrodeposited ZnO materials by showing they can be readily obtained on a large scale at low cost, while their electrical properties can be accurately investigated for desired tunability in advanced devices.