Citation: Prosolov, K.A.; Lastovka,V.V.; Khimich, M.A.; Chebodaeva, V.V.; Khlusov, I.A.; Sharkeev, Y.P. RF Magnetron Sputtering of Substituted Hydroxyapatite for Deposition of Biocoatings. Materials 2022, 15, 6828. https://doi.org/10.3390/ma15196828 Academic Editor: Csaba Balázsi Received: 31 August 2022 Accepted: 28 September 2022 Published: 1 October 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). materials Article RF Magnetron Sputtering of Substituted Hydroxyapatite for Deposition of Biocoatings Konstantin A. Prosolov 1, * , Vladimir V. Lastovka 1 , Margarita A. Khimich 1 , Valentina V. Chebodaeva 1,2 , Igor A. Khlusov 2 and Yurii P. Sharkeev 1,3, * 1 Laboratory of Physics of Nanostructured Biocomposites, Institute of Strength Physics and Materials Science, Siberian Branch of Russian Academy of Sciences, 634055 Tomsk, Russia 2 Laboratory of Cellular and Microfluidic Technologies, Siberian State Medical University, 634050 Tomsk, Russia 3 Research School of High-Energy Physics, National Research Tomsk Polytechnic University, Lenin Avenue 30, 634050 Tomsk, Russia * Correspondence: konstprosolov@gmail.com (K.A.P.); sharkeev@ispms.ru (Y.P.S.); Tel.: +7-961-888-58-33 (K.A.P.) Abstract: Functionalization of titanium (Ti)-based alloy implant surfaces by deposition of calcium phosphates (CaP) has been widely recognized. Substituted hydroxyapatites (HA) allow the coating properties to be tailored based on the use of different Ca substitutes. The formation of antibacterial CaP coatings with the incorporation of Zn or Cu by an RF magnetron sputtering is proposed. The influence of RF magnetron targets elemental composition and structure in the case of Zn-HA and Cu-HA, and the influence of substrate’s grain size, the substrate’s temperature during the deposition, and post-deposition heat treatment (HT) on the resulting coatings are represented. Sintering the targets at 1150 ◦ C resulted in a noticeable structural change with an increase in cell volume and lattice parameters for substituted HA. The deposition rate of Cu-HA and Zn-HA was notably higher compared to stochiometric HA (10.5 and 10) nm/min vs. 9 ± 0.5 nm/min, respectively. At the substrate temperature below 100 ◦ C, all deposited coatings were found to be amorphous with an atomic short-range order corresponding to the {300} plane of crystalline HA. All deposited coatings were found to be hyper-stochiometric with Ca/P ratios varying from 1.9 to 2.5. An increase in the substrate temperature to 200 ◦ C resulted in the formation of equiaxed grain structure on both coarse-grained (CG) and nanostructured (NS) Ti. The use of NS Ti notably increased the scratch resistance of the deposited coatings from18 ± 1 N to 22 ± 2 N. Influence of HT in air or Ar atmosphere is also discussed. Thus, the deposition of Zn- or Cu-containing CaP is a complex process that could be fine-tuned using the obtained research results. Keywords: antibacterial effect; biocompatibility; calcium phosphate; ion substitution; physical vapor deposition; thin films 1. Introduction New materials for regenerative medicine are in high demand due to the aging of the ever-increasing population [1]. The most important parameter among others for newly developed materials ready to be introduced into clinical practice is their biocompatibil- ity [2]. Biocompatible materials can be divided into three groups: biotolerant, bioinert, and bioactive [3]. Bioinert alloys, a striking representative of which are titanium (Ti)-based alloys, are characterized by osteoconductive property, which means that these materials are not included into the metabolic process, are not dissolved in the body, but their surface can provide a physical and mechanical connection to body tissues, and their oxide film promotes the adhesion of various proteins that trigger the osseointegration process [4]. On the other hand, it is known that the wear of the metal surface of implants occurs during their service life, e.g., the cobalt-chrome-molybdenum alloy wears at an average rate of 0.02–0.06 mm over 10 years. The metal chips or particles that appear during wear are Materials 2022, 15, 6828. https://doi.org/10.3390/ma15196828 https://www.mdpi.com/journal/materials