NER: Direct Electron Beam Writing for Fabrication of Functional Nano-Scale Architectures

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This proposal was recieved in response to NSE, NSF-0019. Focused electron beam decomposition of molecules adsorbed on surfaces will be investigated as a means for fabricating electrical contacts to individual or small arrays of nanostructures. This direct write technique offers a convenient, flexible and practical method for bridging the gap between mesoscopic lithography and the nanoscale. Of primary importance is the purity and resistivity of the deposited film. Resistivity will be correlated with process parameters by depositing between predefined metallic contact pads. Contamination of deposited metallic features will be avoided by using inorganic precursor molecules such as TaF5, TiCl4 and WF6 . Film purity will be determined in situ ,using standard surface science techniques. Preliminary estimates of write speeds achievable in environmental electron microscopes indicate that 1:1 aspect ratio,nm-scale wires can be written at rates of 0.1 um /sec. Additionally, use of environmental electron microscopy will allow simultaneous identification and contacting features of interest. The flexibility of this technique will allow tailoring the deposited structures for different applications. Examples are nanowires for electrical contacts, metal nanodot arrays for attachment of functionalized organic molecules or specially shaped metal gates deposited on semiconductor surfaces to allow charge confinement and manipulation in nanoscale regions. Thus,success of this technique will enable rapid prototyping of diverse concepts cutting across several nanoscience and technology subfields. Longer term, the capability for e-beam writing of entire nanodevices is envisioned. Electron-beam decomposition of inorganic species leading to growth of semiconductors and insulators will also be investigated. Novel precursor chemistries will be developed for e-beam growth of insulating and semiconducting phases compatible with Si-based nanoelectronics. Essentially,this is an athermal method for depositing nanoscale features at temperatures below that for which the features 'melt' via surface diffusion of deposited atoms.