Sb-Te Phase-change Nanowires by Templated Electrodeposition
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Sb-Te Phase-change Nanowires by Templated Electrodeposition C. A. Ihalawela1, R. E. Cook2, X. M. Lin3, H. H. Wang4, and G. Chen1∗ 1
Department of Physics and Astronomy, Ohio University, Athens, OH45701 2 Electron Microscopy Center, Argonne National Lab, Argonne, IL 60439 3 Center for Nanoscale Materials, Argonne National Lab, Argonne, IL 60439 4 Materials Science Division, Argonne National Lab, Argonne, IL 60439
ABSTRACT Phase-change memory materials (PCMMs) are semiconductors that exhibit rapid orderdisorder transition under electrical or optical pulse excitation. Currently thin-film-based PCMMs play a dominant role in fabrication of non-volatile memory devices. In contrast, phase-change nanowires (PCNWs) have the potential to overcome future challenges such as high data density and low power consumption. Among the various methods to synthesize PCNWs, the vaporliquid-solid method has been reported previously. In this paper, we report synthesis of Sb-Te PCNWs using a templated electrochemical method. Nanoporous anodic aluminum oxide (AAO) was used as a template for the growth of nanowires. Sb-Te PCNWs with different compositions, diameters and aspect ratios were grown inside the AAO template by electrodeposition. Composition and structure of these nanowires were characterized by energy dispersive X-ray spectroscopy, X-ray diffraction, and scanning and transmission electron microscopy. It is found that electrodeposition through nanosized channels results in materials that are quite different from those electrodeposited on unrestricted surface. The mechanism of nanowire formation inside the channels of AAO template is discussed. INTRODUCTION Rapid switching between two stable phases, crystalline and amorphous, with significant changes in optical reflectivity and electrical resistivity is the key for phase-change memory [1]. Among all the phase-change memory materials (PCMMs), Ge-Sb-Te (GST) alloys have captured a great deal of attention due to their excellent switching performance [2]. To further enhance the properties of phase-change materials, one could harness the effect of nanoscale confinement [1]. Studies of 0D (nanoparticles) [3–10], 1D (nanowires) [11–14], and 2D (thin films) [15–18] confinement of the ternary GST have been conducted by a few research groups, and changes in the phase transition (i.e., melting and crystallization) temperatures due to confinement have been reported. The low dimensional confinement has the potential to overcome challenges for future memory devices such as to achieve high storage density and low power consumption [19]. Currently phase-change thin films play a main role in data storage and random access nonvolatile memory [20-23]. Phase-change nanowires (PCNWs), on the other hand, are very promising to overcome the above mentioned challenges for next-generation non-volatile memory. Various techniques such as the vapor-liquid-solid method [11–14, 24, 25], the colloidal method [26], and the electrochemical deposition method [27-29] have been reported for the synthesis of PCNWs. In
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