Effects of Thickness and Indenter Geometry in Nanoindentation of Nickel Thin Films
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Effects of Thickness and Indenter Geometry in Nanoindentation of Nickel Thin Films Padma Parakala, Reza A. Mirshams, Seifollah Nasrazadani, and *Kun Lian Department of Engineering Technology, University of North Texas, Denton, TX 76203 *Center for Advanced Microstructure and Devices (CAMD), Louisiana State University, Baton Rouge, LA 70803 ABSTRACT Effects of thickness and tip geometry on Ni thin films deposited on Cu substrate were studied using nanoindenter. The deformation mechanisms in correlation to hardness measurements were discussed at various loads and depths of penetration. The Berkovich, Cube corner and Conical tips have been used in this study. Initially, the hardness and modulus of elasticity were measured at a depth of 10% of film thickness. The depth of penetration was increased to 20% to observe the depth effects. Analysis of data showed that there is an Indentation Size Effect (ISE) irrespective of indenter tip geometries. INTRODUCTION The measurement of mechanical properties of microelectronic thin films and coatings are necessary in many electronic and mechanical systems such as integrated circuits, microprocessors, data storage technologies, and Micro Electro Mechanical Systems (MEMS) [13]. Measuring mechanical properties like hardness and modulus of elasticity will help to evaluate the reliability of the materials in parts and components and to understand the strengthening and deformation mechanisms in small scales [4]. Silicon and silicon-based materials like silicon carbide are commonly used for structural components [5]. However, research efforts are in progress to replace silicon with metallic and other non-metallic materials. Nickel and nickel-based alloys have received more interests for this purpose. Nickel being a low cost material has high strength, stiffness, fracture toughness, hardness and modulus of elasticity [6]. Several studies have pointed out that the indentation size could significantly effect on the measured hardness values. Measured mechanical properties like hardness and modulus of elasticity are always overestimated because of the ISE. This trend is seen more in thin films whose thicknesses are less than 10 µm [7]. Several theories and models were proposed to explain ISE phenomena [8]. Nix and Gao model, based on the dislocation mechanisms, has been attracted many investigations in recent years [8,9]. Nanoindentation techniques have been extensively used for characterization of materials properties like hardness and modulus of elasticity on small-scales [10-14]. The effects of indenter tip geometry and substrate have been studied and reported in several papers [9,15-18]. This paper emphasizes the effect of tip geometry (Berkovich, Cubecorner and, Conical) on mechanical properties like hardness and modulus of elasticity of nickel thin films deposited on soft copper. EXPERIMENTAL PROCEDURE Materials used The electro deposited nickel thin films on copper substrate with different thicknesses used in this research were received from the Center for Advanced Mic rostruc
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