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SPECIAL SECTION ON NANOMATERIALS AND NANOMECHANICS

# Structure and Properties of Electrocodeposited $Cu–Al2O3$ Nanocomposite Thin Films

[+] Author and Article Information
Yong Gan, Dongyun Lee, Xi Chen, Jeffrey W. Kysar

Columbia Nanomechanics Research Center, Department of Mechanical Engineering,  Columbia University, New York, NY 10027

J. Eng. Mater. Technol 127(4), 451-456 (Feb 22, 2005) (6 pages) doi:10.1115/1.1925292 History: Received October 22, 2004; Revised February 22, 2005

## Abstract

Nanocomposite thin films which consist of $50nm$$Al2O3$ nanoparticles in a copper metal matrix were deposited on a silicon wafer. The thickness of the nanocomposite thin films was about $3microns$ and the volume density of the nanoparticles was between 3% and 5%. The films were synthesized using electrocodeposition. The grain size of the nanocomposite film was significantly smaller than the grain size of control films of pure copper. Electron backscatter diffraction (EBSD) experiments indicate that neither the nanocomposite thin films nor the control films exhibits a crystallographic texture. Nanoindentation experiments show that the hardness of the nanocomposite thin film is approximately 25% higher than the hardness of the control films of pure copper. A prototype of a microchannel array in the nanocomposite thin film was made using standard microelectromechanical (MEMS) fabrication technology. It is expected that the enhanced mechanical properties exhibited by nanocomposite thin films have the potential to improve the reliability of various MEMS devices which rely on thin metal films. The results presented herein lay the groundwork for future studies in which the size, volume density, morphology, distribution as well as type of nanoparticle in the nanocomposite will be systematically and independently varied in order to optimize mechanical properties.

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## Figures

Figure 5

Representative load-displacement curves of the nanoindentation tests on 3μm pure copper control film and the nanocomposite thin film

Figure 4

(a) Inverse pole figure which indicates that no preferred crystallographic texture exists for the 3μm thin film of pure copper. (b) Inverse pole figure which indicates that no preferred crystallographic texture exists for the 3μm nanocomposite thin film.

Figure 3

(a) Al2O3 nanoparticles interspersed in the 3μm nanocomposite thin film. The nanoparticles have an average size of 50nm. (b) At higher magnification, individual particles as well as aggregates of nanoparticles are apparent in the 3μm nanocomposite thin film.

Figure 2

(a) Grain morphology of as-deposited 3μm pure copper thin film. (b) Grain morphology of as-deposited 3μm nanocomposite thin film of copper matrix and alumina nanoparticles.

Figure 6

Ductile fracture mechanisms evident on fracture surface of Cu–Al2O3 nanocomposite thin film

Figure 7

Vertically aligned microchannels in the Cu–Al2O3 nanocomposite film

Figure 1

Installation for electrocodeposition

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