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A8.9.1

Fabrication of silicon nanowire network in aluminum thin films Vincent H. Liu1, Husam H. Abu-Safe, Hameed A. Naseem, and William D. Brown Arkansas Photovoltaic Research Center, Department of Electrical Engineering, University of Arkansas, Fayetteville, AR, 72701 1

Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA, 94709 ABSTRACT The formation of isolated silicon nanowires and silicon nanowire networks using aluminum thin film is investigated. The formation mechanism of the network mainly depends on the diffusion of silicon in the aluminum thin film. The silicon stops at the film grain boundaries. The continuous accumulations of silicon at these boundaries give raise to a continuous network of silicon nanowires. Characterization of the nanowires has been done using scanning electron microscopy and energy dispersive x-ray spectroscopy. These results are unique in the fact that the nanowires found are grown in a horizontal fashion instead of the more common vertical direction. Most of the nanowires have a diameter of about 60 nm and a length of over 10 µm. INTRODUCTION The continued scaling of silicon IC technology has produced need for a new generation of devices. Silicon nanowires have proved to be valuable both as research devices and as building blocks for nanotechnology [1]; this is proved by the recent progress of transistors and lasers built with nanowires [2]. However, fabrication of large amount of nanowires has proven to be a challenge still. Self assembly of nanostructures provides a reasonably cost efficient and easy to implement way to fabricate nanoelectronics components [3, 4]. Many different attempts to fabricate silicon nanowires have been devised, including the vapor liquid solid method (VLS) [5] and the solid liquid solid method (SLS) [6] with metal catalysts, and laser ablation of powder silicon [7]. However, the fabricated nanowires using these methods are still in need to be incorporated into devices and be tested as charge carriers. There has been a recent study [8] that reports a method to fabricate aluminum-silicon nanowire networks that actually can conduct currents. The web-like network was fabricated by de-alloying an aluminum-silicon thin film through selective chemical etching. The current that propagated through the network depends, in general, on the etch time of the alloyed film. However, lack of control over the design of these networks, reduces its appropriateness when well designed architecture is required. In this paper, we report a method of fabricating silicon nano-network using a silicon substrate. We also show that the SLS method of producing nanowires is not limited to using gold as a catalyst, but allows the use of aluminum thin films as a catalyst as well. Furthermore, we have shown that the use of aluminum as a catalyst results in a nanowire network that grows in

A8.9.2

the horizontal direction rather than the vertical direction. The effect of annealing time on the nanowire network is also investigated an