Peculiarities of Electric and Dielectric Behavior of Ni- or Fe-Doped ZnO Thin Films Deposited by Atomic Layer Deposition.

The physical properties of ZnO can be tuned efficiently and controllably by doping with the proper element. Doping of ZnO thin films with 3D transition metals that have unpaired electron spins (e.g., Fe, Co, Ni, etc.) is of particular interest as it may enable magnetic phenomena in the layers. Atomic layer deposition (ALD) is the most advanced technique, which ensures high accuracy throughout the deposition process, producing uniform films with controllable composition and thickness, forming smooth and sharp interfaces. In this work, ALD was used to prepare Ni- or Fe-doped ZnO thin films. The dielectric and electrical properties of the films were studied by measuring the standard current-voltage (I-V), capacitance-voltage (C-V), and capacitance-frequency (C-f) characteristics at different temperatures. Spectral ellipsometry was used to assess the optical bandgap of the layers. We established that the dopant strongly affects the electric and dielectric behavior of the layers. The results provide evidence that different polarization mechanisms dominate the dielectric response of Ni- and Fe-doped films.