  Citation: Heidari, P.; Salehi, M.; Ruhani, B.; Purcar, V.; C˘ apr˘ arescu, S. Inﬂuence of Thin Film Deposition on AFM Cantilever Tips in Adhesion and Young’s Modulus of MEMS Surfaces. Materials 2022, 15, 2102. https://doi.org/10.3390/ ma15062102 Academic Editors: Lukasz Skowronski and Dominique de Caro Received: 30 January 2022 Accepted: 10 March 2022 Published: 12 March 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 Inﬂuence of Thin Film Deposition on AFM Cantilever Tips in Adhesion and Young’s Modulus of MEMS Surfaces Pedram Heidari 1 , Majid Salehi 1 , Behrooz Ruhani 1 , Violeta Purcar 2, * and Simona Căprărescu 3 1 Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Najafabad 8514143131, Iran; pedram.heidari90@gmail.com (P.H.); Salehi.majid89@gmail.com (M.S.); b.ruhani55@gmail.com (B.R.) 2 National Institute for Research & Development in Chemistry and Petrochemistry—ICECHIM, Splaiul Independentei No. 202, 6th District, 060021 Bucharest, Romania 3 Faculty of Applied Chemistry and Materials Science, Department of Inorganic Chemistry, Physical Chemistry and Electrochemistry, University Politehnica of Bucharest, Ghe. Polizu Street, No. 1-7, 011061 Bucharest, Romania; simona.caprarescu@upb.ro * Correspondence: violeta.purcar@icechim.ro Abstract: Adhesion is a critical factor in microelectromechanical systems (MEMSs) and is inﬂuenced by many parameters. In important ﬁelds, such as microassembly, an improved understanding of adhesion can result in higher precision. This study examines the inﬂuence of deposition of gold and titanium onto the atomic force microscope (AFM) tips in adhesion forces and Young’s modulus, between a few MEMS substrates (silicon, gold, and silver) and the AFM tips. It was found that, except for gold substrate, an AFM tip coated with gold has the highest adhesion force of 42.67 nN for silicon substrates, whereas the titanium-coated AFM tip decreases the force for all the samples. This study suggests that such changes must be taken into account while studying the adhesion force. The ﬁnal results indicate that utilizing gold substrate with titanium AFM tip led to the lowest adhesion force, which could be useful in adhesion force measurement during microassembly. Keywords: AFM tip deposition; adhesion force; Young’s modulus; thin ﬁlm; microelectromechanical systems; coating 1. Introduction Surface forces are among the most important challenges in miniature structures’ de- sign and function. Tribological aspects such as stiction, adhesion, friction, and wear receive signiﬁcant attention in developing and manufacturing micro- and nanostructures, such as microelectromechanical systems (MEMSs). These aspects are becoming increasingly important for structures with a large surface-area-to-volume ratio [1–3]. For instance, sur- face micromachining has been widely employed to manufacture microstructures. During the release process, if the restoring force is less than the attractive force, the structure tends to adhere to the underlying substrate. This phenomenon is commonly referred to as stiction [4,5]. Since microstructures placed in vertical positions can adhere to the substrate and disturb the entire structure [6], many studies have been conducted to dominate the surface forces at micro- and nanoscale in recent years. Shui et al. [7] proposed a method to continuously regulate adhesion forces by creating mechanical microvibrations for a typical polydimethylsiloxane (PDMS) glass substrate. Their result indicated that the adhesion force could be increased or weakened 77 times using this technique. In another study, Peillon et al. [8] investigated the changes in surface forces by depositing tungsten microparticles on tungsten substrates with different degrees of roughness. Theoretical and experimen- tal methods were utilized to measure the forces, and they found that the dependence of adhesion force on particle size has a secondary effect, compared with surface roughness. Moreover, the assembly of these microdevices is greatly dependent on the existence of Materials 2022, 15, 2102. https://doi.org/10.3390/ma15062102 https://www.mdpi.com/journal/materials