Paper NS-TuP17
Au-catalyzed Self Assembly of Ge-Sb-Te Nanowires by Metalorganic Chemical Vapour Deposition

Tuesday, October 19, 2010, 6:00 pm, Room Southwest Exhibit Hall

The Metalorganic Chemical Vapor Deposition (MOCVD), already promising for its potentialities in the scaling down of phase change memories (PCM, PRAM), was adopted for the Au-catalyzed self assembly of NanoWires (NWs) formed by Ge-Sb-Te alloys on SiO₂/Si substrates; the employed metalorganic precursors were tetrakisdimethylaminogermanium, trisdimethylaminoantimony and diisopropyltelluride; the process gas was N₂.

The NW properties were studied by X-ray Diffraction (XRD), Total Reflection X-ray Fluorescence (TXRF) and Scanning Electron Microscopy (SEM) observations. Local measurements were carried out on single nanostructures by High Resolution and Analytical Transmission Electron Microscopy (TEM).

Ge-Sb-Te (GST) NWs exhibited a mean diameter distribution centered on 35 nm and a length up to 1 μm. Two types of GST NWs were identified: i) “big” NWs, featured by mean cross size > 50 nm and aspect ratio (AR = length/mean width) distribution centered around 5 and ii) “small” NWs, featured by mean cross size < 50 nm and AR distribution centered around 12. Measurements indicated that GST NWs are compatible with both the Ge₁Sb₂Te₄ and Ge₁Sb₄Te₇ compositions and crystallographic phases.

The typical diameter of the GeTe NWs resulted to be around 50 nm and their length up to 4 μm. The structural measurements showed that both the cubic and rhombohedral crystalline phases of GeTe are present in the obtained NWs, whereas the compositional analyses yielded a Ge₃₆Te₆₄ composition. In particular, TEM observations revealed that the fcc wires are single crystals, 110 oriented.