Self-organized Si Nanowires with Room-Temperature Photo-Emission
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Self-organized Si Nanowires with Room-Temperature Photo-Emission Chunhai Ji, Elena A. Guliants1, Don Abeysinghe1 and Wayne A. Anderson University at Buffalo, State University of New York, Dept of Electrical Engineering, Buffalo, NY, U.S.A. 1 Taitech, Inc. AMC PO BOX 33630 WPAFB, OH, U.S.A.
ABSTRACT Two-dimensional arrays of self-organized Si nanowires were synthesized using the metal induced growth (MIG) method. In MIG processing, the thermally evaporated 25~100 nm thick Ni films serve as prelayers for magnetron sputtered Si. When sputtering at 550 °C, the Si crystallization occurs via the formation of nickel disilicide followed by subsequent epitaxial growth of Si crystals on nickel disilicide due to an extremely small lattice mismatch. Scanning electron microscopy study showed that the nanowires originated from the Si thin film and grew upwards in bundles. The diameter of the nanowires was 20 ~ 50 nm. The length of the nanowires was typically 1 µm. Transmission electron microscopy and electron diffraction analysis revealed the single crystal structure of nanowires. Quantum-size effects in the produced wires were investigated by measuring the photoluminescence spectra at both low and room temperature. An intense room temperature PL peak centered around 690 nm with FWHM of 180 nm showed the promise of MIG-Si nanowires for red light-emitting diode applications. In addition, self-aligned silicide film on the bottom provides an ultimate back Ohmic contact, which significantly simplifies the fabrication of optoelectronic devices. INTRODUCTION In this work, we present a method to make self-aligned Si nanowires by using metal-inducedgrowth. In 1964 Wagner and Ellis proposed the vapor-liquid-solid model for Si whisker growth using Au as a growth catalyst [1]. Since then, Si-based nanostructures have attracted much attention because of their fascinating quantum properties [2,3] with potential use in onedimensional quantum wire high-speed field effect transistors [4] and light-emitting devices with extremely low power consumption [5]. Most of the approaches for making one-dimensional Si nanowires used the expensive excimer laser as an ablating beam source [6,7], and only a few simple physical deposition methods were reported to date [8], which makes this particular observation even more important. Our method for growing Si nanowires is the so called metalinduced-growth (MIG) method. In MIG processing, the thermally evaporated Ni films serve as prelayers for magnetron sputtered Si. When sputtering at 550 °C, the Si crystallization occurs via the formation of nickel disilicide followed by subsequent epitaxial growth of Si crystals on nickel disilicide due to an extremely small lattice mismatch. MIG is used to grow a polycrystalline Si thin film with larger grain structures at lower temperatures [9]. In the experiments, with a lower magnetron sputtering power, bundles of single crystalline Si nanowires were grown on the surface.
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