Role of Nucleation on the Growth of Nanocrystalline Diamond (NCD) Films: A Particular Study in the Fabrication of Micro-
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Role of Nucleation on the Growth of Nanocrystalline Diamond (NCD) Films: A Particular Study in the Fabrication of Micro-cantilevers Sathyaharish Jeedigunta1, Priscila Spagnol2, John Bumgarner2, and Ashok Kumar3 1 Department of Electrical engineering, University of South Florida, Tampa, FL, 33620 2 SRI International, St.Petersburg, FL, 33701 3 Department of Mechanical engineering, University of South Florida, Tampa, FL, 33620 ABSTRACT The effect of ultrasonic method of seeding on the growth of nanocrystalline diamond (NCD) films has been studied by investigating the nucleation densities of two nanodiamond slurries- 1) nanodiamond powder suspended in acetone 2) mixture of titanium nanopowder and nanodiamond powder suspended in acetone. The former has resulted in a lower nucleation density on the order of 108 cm-2 while the later has increased the nucleation density by over two orders (>1010 cm-2) of magnitude. NCD films were grown on Si(100) substrates in a Cyrannus I Iplas microwave plasma enhanced chemical vapor deposition (MPECVD) reactor using 0.5% CH4, 1% H2 and 98.5% Ar gas chemistry at a substrate temperature of ~ 750° C, pressure of 135 T and a microwave power of 1.8 kW. The double anchored cantilever structures with NCD as structural material have been fabricated by conventional photolithography. It was observed that the films grown after pre-treating the substrates in pure nanodiamond slurry have not provided a complete coverage at the anchor regions of the cantilevers due to the lower nucleation density. Hence during the sacrificial oxide etch, the anchor regions did not adhere well to the substrate and the entire structures got detached from the substrate. But on the other hand, the films grown by seeding the substrates in a suspension of titanium nanopowder and diamond nanopowder showed complete film coverage and consequently very good bonding to the Si substrate at the anchor pads. In this case, the cantilevers have been successfully released without any problems at the anchor pads. Further the mechanical properties of the films were conducted by evaluating the Young’s modulus and the hardness by nano-indentation technique.
INTRODUCTION
Most of the studies related to the nanocrystalline diamond (NCD) films have been limited to the growth, characterization and properties of the films. To date, there are only few NCD based microelectronic devices, or MEMS components that have been successfully fabricated. This limitation is due to some of the inherent challenges involved in the microfabrication procedures using NCD [1-3]. One such problem that could be a hindrance to the NCD devices is the nucleation. In spite of the recent advances in the diamond science and technology and several successful reports on the growth and nucleation of diamond on non diamond substrates and other carbide forming metals such as Titanium, Hafnium and Tungsten, the method of nucleation of diamond on non diamond substrates still needs further investigation [4]. Several methods of nucleation such as ultrasonic polishi
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