Comprehensive Mechanical and Tribological Characterization of Ultra-Thin-Films
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1049-AA02-04
Comprehensive Mechanical and Tribological Characterization of Ultra-Thin-Films Norm Gitis, Michael Vinogradov, Ilja Hermann, and Suresh Kuiry Center for Tribology, Inc., 1715 Dell Ave, Campbell, CA, 95008 ABSTRACT Mechanical and tribological properties such as hardness, Young’s modulus, friction, and scratch adhesion strength of various coatings and ultra-thin films are reported. These results, obtained using a Universal Nano+Micro Tester UNMT-1, indicate that a substrate effect for ultra-thin films is substantial when using conventional static nanoindentation technique, while negligible with an advanced dynamic nano-indentation. Comparative results of hardness and Young’s modulus obtained from various techniques are presented. A means to evaluate friction and adhesion strength of thin films is highlighted, using DLC specimens as an example. INTRODUCTION Evaluation of mechanical and tribological properties of bulk and coating materials is of great importance for design and development of engineering components with enhanced structural and wear performance [1-3]. Traditional indentation tests of bulk materials include macro-hardness measurements at high loads of the order of kN. Micro-hardness measurements of coatings and bulk materials are usually performed under loads of the order of N. As the industrial technology advanced, the characterization technique for mechanical properties of thin films and coating shifted its range to mN and even µN. In recent years, nano-indentation has become a popular technique for evaluation of hardness and Young’s modulus of films and coatings. The nature of stress distribution in the front of a nano-indenter tip makes the indentation vulnerable to a substrate effect. Usually, the indentation depth should be restricted to 5 - 10% of the film thickness to limit the stress field within the thickness of the film and thus, to avoid the substrate influencing the results of such measurements. Such measurements at ultra-shallow depths would require an extremely high accuracy of both depth monitoring and tip calibration. Although AFM-based nano-indentation shows some potential to circumvent such problem, the use of compliant tips limits its applications to soft materials. A novel Nano-analyzer enables quantitative characterization of ultra-thin films, including hard and super-hard films, at shallow depths with a negligible substrate effect. Primary objective of the present investigation is to compare different techniques to perform mechanical and tribological tests on micro and nano-level using a single tester. EXPERIMENTAL The micro-indentation, micro-scratch, nano-indentation, nano-scratch, and nano-imaging techniques were employed for evaluation of mechanical and tribological properties of numerous bulk, coating and film specimens using the same Universal Nano+Micro Tester model UNMT-1, designed and manufactured by CETR, Inc. The photograph of its nano-head is presented in Figure 1. UNMT-1 has several easily interchangeable modules for precision tests of hardness, Young’s mod
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