Contents lists available at ScienceDirect Surface & Coatings Technology journal homepage: www.elsevier.com/locate/surfcoat Infuence of oblique angle deposition on Cu-substituted hydroxyapatite nano-roughness and morphology Konstantin A. Prosolov a,b, ⁎ , Margarita A. Khimich a,c , Julietta V. Rau d,e , Dmitry V. Lychagin c , Yurii P. Sharkeev a,b a Institute of Strength Physics and Materials Science of SB RAS, Akademicheskii pr. 2/4, 634055 Tomsk, Russia b National Research Tomsk Polytechnic University, Lenin Avenue 30, 634050 Tomsk, Russia c National Research Tomsk State University, Lenin Avenue 36, 634050 Tomsk, Russia d Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche (ISM-CNR), Via del Fosso del Cavaliere 100, 00133 Rome, Italy e Sechenov First Moscow State Medical University, Trubetskaya 8, build. 2, 119991 Moscow, Russia ARTICLEINFO Keywords: Glancing angle deposition Calcium phosphate coatings Physical vapor deposition Nano-roughness Copper-substituted apatite ABSTRACT Inthiswork,westudytheefectofRFmagnetronobliqueangledeposition(OAD)onmorphology,structure,and elemental composition of as-deposited and heat-treated Cu containing calcium phosphates. The control over the surface morphology and nano roughness provided by OAD is of great interest as both Mesenchymal Stem Cells and various types of bacteria respond strongly to nanoscale topography. A Cu substituted hydroxyapatite target was used to deposit coatings on the surface of titanium (Ti) and silicon (Si) substrates. The samples were placed atanobliqueangleof80°relativetothesurfaceofthesampleholderandinanormalconfguration with respect tothefuxdirectionand,therefore,paralleltothetarget.Thedensehomogeneouscoatingswithglobularsurface features deposited at normal fux incidence (NFI) confguration changed to elliptical, highly oriented structures withthedirectiondictatedbytheatomicshadowingefectwhenthesubstratewasdepositedatanobliqueangle. As-deposited thin flms were subjected to post-deposition-heat-treatment at 700 °C in an Ar atmosphere. This led to a drastic change in the surface morphology and, namely, lost the directionality of the nanostructures. AccordingtotheX-raydifractiondata,thesamplesdepositedobliquelyshowedpreferentialgrowthinthe(002) plane and lower internal stress, than samples coated at NFI for both the Si and Ti substrates. The RMS roughness of the flms deposited obliquely on Si was twice that of the flms deposited at NFI (860 ± 80 pm and 408 ± 60 pm, respectively). However, it was not the case for the Ti substrate, the RMS roughness decreased from42 ± 4nmforcoatingsdepositedatnormal fuxgeometryto33 ± 2nm forcoatingsdepositedobliquely. The heat-treatment of the samples deposited at 80° resulted in a signifcant increase in the surface roughness: 8 ± 0.7 nm for Si and 71 ± 4 nm for Ti substrates. The obtained results demonstrate that the oblique angle deposition can be used to fabricate nano-rough surface morphologies. 1. Introduction Fabrication of nanoscale surface topography for biomedical im- plants is a powerful tool to modulate protein expression and cellular functions, such as diferentiation, proliferation, and survival of Mesenchymal Stem Cells (MSC) [1–4]. In the feld of biomedical en- gineering, the formation of nanostructures is believed to be an alter- native route for improving the osteointegration and osteoinduction properties of the implant's surface. According to the work of Ha et al. [5] osteoinduction generally refers to the process by which pluri- or multipotent MSCs are recruited to a given site, often for repair, and are stimulated towards early-stage preosteoblasts. The MSC guidance can be performed through inductive proteins that could be governed by the nanoscale surface. Anderson et al. [1] recently demonstrated that many diferent cell types, including fbroblasts, osteoblasts, osteoclasts, en- dothelial, smooth muscle, epithelial, epitenon, neural, and MSCs, re- spond strongly to nanoscale topography and are infuenced in a similar way by microtopography with changes in morphology and adhesion. Given that diferent cell types show diferent responses to diferent surface topographies, there is a continuous need for the development of “next-generation” biomaterials and medical implants. Additionally to the strive for better osteointegration, there is an unmet demand for https://doi.org/10.1016/j.surfcoat.2020.125883 Received 8 December 2019; Received in revised form 4 April 2020; Accepted 4 May 2020 ⁎ Corresponding author at: Institute of Strength Physics and Materials Science of SB RAS, 2/4, Akademicheskii pr., Tomsk 634055, Russia. E-mail addresses: konstprosolov@gmail.com (K.A. Prosolov), khimich@ispms.ru (M.A. Khimich), giulietta.rau@ism.cnr.it (J.V. Rau), dvl-tomsk@mail.ru (D.V. Lychagin), sharkeev@ispms.ru (Y.P. Sharkeev). Surface & Coatings Technology 394 (2020) 125883 Available online 07 May 2020 0257-8972/ © 2020 Elsevier B.V. All rights reserved. T