Current sustainability and electromigration of Pd, Sc and Y thin-films as potential interconnects

The progress on novel interconnects for carbon nanotube (CNT)-based electronic circuit is by far behind the remarkable development of CNT-field effect transistors. The Cu interconnect material used in current integrated circuits seems not applicable for the novel interconnects, as it requires electrochemical deposition followed by chemical-mechanical polishing. We report our experimental results on the failure current density, resistivity, electromigration effect and failure mechanism of patterned stripes of Pd, Sc and Y thin-films, regarding them as the potential novel interconnects. The Pd stripes have a failure current density of (8 similar to 10)x10(6) A/cm(2) (MA/cm(2)), and they are stable when the working current density is as much as 90% of the failure current density. However, they show a resistivity around 210 mu O.cm, which is 20 times of the bulk value and leaving room for improvement. Compared to Pd, the Sc stripes have a similar resistivity but smaller failure current density of 4 similar to 5 MA/cm(2). Y stripes seem not suitable for interconnects by showing even lower failure current density than that of Sc and evidence of oxidation. For comparison, Au stripes of the same dimensions show a failure current density of 30 MA/cm(2) and a resistivity around 4 mu O.cm, making them also a good material as novel interconnects.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000208414400008&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Nanoscience & NanotechnologyMaterials Science, MultidisciplinaryPhysics, AppliedSCI(E)2ARTICLE3184-189

Direct observation of Si-related and Ge-related ring clusters on Si(1 1 1)-(7 Â 7) surface

Abstract In a scanning tunnelling microscope (STM) study of Si(1 1 1)-(7 Â 7) surfaces, we observed the Si-related ring cluster and one new type of Ge-related ring cluster. For both clusters there is an electron transfer between them and the nearby Si centre atoms and their local density of states near the Fermi level is obviously reduced. Moreover, by differences in their electron transfer, the Si-related ring cluster and Ge-related ring cluster can be easily distinguished from each other.

Probing Quantum Confinement of Single-Walled Carbon Nanotubes by Resonant Soft-X-Ray Emission Spectroscopy

[[abstract]]We report the band-structure changes near Fermi level for single-walled carbon nanotubes (SWNTs) with diameters down to 1 nm from the study of soft-x-ray absorption and resonant emission spectroscopy. The observed quantum confinement of SWNTs affects both pi and sigma bands and bandgap through the rehybridization of pi and sigma orbitals. The significant changes of electronic structure are proved to be a measure for the mean diameter of the macroscopic amounts of SWNTs. (C) 2008 American Institute of Physics.[[notice]]補正完畢[[booktype]]紙

Carbon Nanotubes Enhance Cytotoxicity Mediated by Human Lymphocytes In Vitro

With the expansion of the potential applications of carbon nanotubes (CNT) in biomedical fields, the toxicity and biocompatibility of CNT have become issues of growing concern. Since the immune system often mediates tissue damage during pathogenesis, it is important to explore whether CNT can trigger cytotoxicity through affecting the immune functions. In the current study, we evaluated the influence of CNT on the cytotoxicity mediated by human lymphocytes in vitro. The results showed that while CNT at low concentrations (0.001 to 0.1 µg/ml) did not cause obvious cell death or apoptosis directly, it enhanced lymphocyte-mediated cytotoxicity against multiple human cell lines. In addition, CNT increased the secretion of IFN-γ and TNF-α by the lymphocytes. CNT also upregulated the NF-κB expression in lymphocytes, and the blockage of the NF-κB pathway reduced the lymphocyte-mediated cytotoxicity triggered by CNT. These results suggest that CNT at lower concentrations may prospectively initiate an indirect cytotoxicity through affecting the function of lymphocytes