The Relationship between Contact Resistance and Contact Force on Au coated Carbon Nanotube surfaces

Carbon-nanotube (CNT) coated surfaces are investigated to determine the electrical contact performance under low force conditions. The surfaces under investigation are multi-walled CNTs formed on a silicon substrate and coated with an Au film. These planar surfaces are mated with a hemispherical Au plated probe mounted in a nano-indentation apparatus. The maximum contact force used is 1 mN. The contact resistance of these surfaces is investigated as a function of the applied force and is also studied under repeated loading cycles. The surfaces are compared with a reference Au-Au contact under the same experimental conditions and the results compared to established contact theory. The results show that the multi-walled CNT surface provides a stable contact resistance, but that the performance could be improved further with the application of single-walled CNT coatings. This initial study shows the potential for the application of CNT surfaces as an interface in low force electrical contact applications.

I. INTRODUCTION

The paper presents a study of electrical contact surfaces under low force conditions, typically below lmN. Such condition are relevant to micro-contact applications, for example MEMS relay devices. There are a number of potential materials for such applications and Gold, Palladium or Platinum are commonly used [1]. The disadvantage of such materials are that they are relatively soft and easily wear. Other materials which are of interest for MEMS devices are silicon carbide and diamond. Both have high moduli but a low electrical conductivity. This makes them unsuitable for electrical contact applications. When SiC film is doped with the resistivity drops to [2] and DLC is doped with ruthenium the resistivity drops to [3] but both materials have higher resistivity compared to gold and its alloys (for example Au-6.3% Pt has a resistivity of [1].