Abstract
Cadmium selenide nanowires in the wurtzite bulk phase, connected to gold electrodes are studied using local density approximation. The short wire is fully metalized by metal-induced gap states. For longer wires, a gap similar to that in bare cadmium selenide nanowires is observed near the center while sub-gap structure emerges near the metal-semiconductor nanocontact. This behavior is attributed to the formation of sub-gap interface states that vanish rapidly towards the center of the wire, consistent with experimental results. For the longer wires Schottky barriers develop with heights larger than the corresponding bulk value. Our study thus indicates that the length of the naonowire sandwitched between gold electrodes should be greater than 8.76 Å to get characteristics of bare CdSe nanowire. Key Words: Metal-induced gap states, Schottky barrier, Nanodumbell, Nanocontact, Gold electrodes, CdSe nanowire
Highlights
Understanding electron transport through nanoscale junctions or molecular devices connected to metallic electrodes may be the basis of future molecular electronics technology (Nitzan, 2001)
COMPUTATIONAL DETAILS The calculations are based on a plane wave expansion method employing relativistic ultrasoft pseudopotentials (USPP) (Vanderbilt, 1990; and Kress and Furthmuller, 1996) and the local density approximation (LDA) for exchange and correlation term approximated by the CeperleyAlder functional (Ceperley et al, 1980) and parametrized by Vosko-Wilk-Nusair (Vosko et al, 1980)
CdSe nanowires etched from the bulk wurtzite structures connected to gold electrodes are studied using LDA-DFT
Summary
Understanding electron transport through nanoscale junctions or molecular devices connected to metallic electrodes may be the basis of future molecular electronics technology (Nitzan, 2001). The metal-SC nanojunction was treated theoretically by Landman et al (2000) who studied the nanocontacts formed between Si-nanowires and Al nanoelectrodes These authors predicted the induction of sub-gap states near the Si-Al interface, which rapidly decay into the Si, and the development of relatively large Schottky barrier. A gap similar to that in bare CdSe nanorods (Katz et al, 2002) is observed near the nanodumbell (NDB) center, while sub-gap structure emerges near the metalSC nanocontact They have demonstrated that the NDBs provide a unique model system to study the physical properties of metal-SC nanojunctions, a fundamental problem of significant importance in the quest for reliable nanoelectronic devices. The systems studied in this work are of the form Au13-CdnSen-Au13 nanocontacts, placed the CdnSen nanowire between two Au13 electrodes
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