Ni-Alloyed Copper Iodide Thin Films: Microstructural Features and Functional Performance

To tailor electrical properties of often degenerate pristine CuI, Ni is introduced as alloy constituent. Cosputtering in a reactive, but also in an inert atmosphere as well as pulsed laser deposition (PLD), is used to grow NixCu1-xI$\left(\text{Ni}\right)_{x} \left(\text{Cu}\right)_{1 - x} \text{I}$ thin films. The Ni content within the alloy thin films is systematically varied for different growth techniques and growth conditions. A solubility limit is evidenced by an additional NiI2(H2O)6$\left(\text{NiI}\right)_{2} \left(\left(\text{(H}\right)_{2} \text{O)}\right)_{6}$ phase for Ni contents x >= 0.31$x \geq 0.31$, observed in X-Ray diffraction and atomic force microscopy by a change in surface morphology. Furthermore, metallic, nanoscaled nickel clusters, revealed by X-Ray photoelectron spectroscopy and high-resolution transmission electron microscopy (HRTEM), underpin a solubility limit of Ni in CuI. Although no reduction of charge carrier density is observed with increasing Ni content, a dilute magnetic behavior of the thin films is observed in vibrating sample magnetometry. Further, independent of the deposition technique, unique multilayer features are observed in HRTEM measurements for thin films of a cation composition of x approximate to 0.06$x \approx $. Opposite to previous claims, no transition to n-type behavior was observed, which was also confirmed by density functional theory calculations of the alloy system. In order to tailor electrical properties of the highly conductive p-type semiconductor CuI, Ni is introduced as alloy constituent. As a result of comprehensive growth study, using magnetron cosputtering and pulsed laser deposition, interesting structural properties, such as a multilayer feature within the alloy system, are presented.image (c) 2024 WILEY-VCH GmbH