NANOFABRICATION AND RAPID IMAGING WITH A SCANNING TUNNELING MICROSCOPE

Nanowires have been made by decomposing organometallic gases in a UHV scanning tunneling microscope (STM); this process is a form of chemical vapor deposition (CVD). Our STM is coupled to a commercial scanning electron microscope (SEM), which allows us to align the tip with pre-existing contact pads for electrical measurements of the nanowires. Thus four-contact measurements on two wires have been performed, a first for STM-fabricated structures. The resistivity of the first wire made from a nickel carbonyl precursor gas is 34 +/- 10 muOMEGA cm at room temperature. This is remarkably close to the bulk value of 7.8 muOMEGA cm, since the wire is only 5 nm thick, 190 nm wide and 3.7 mum long. This indicates that the nickel deposits are fairly pure, and is consistent with Auger analysis made on micron-size deposits: there is at least 95% nickel in these deposits. This is a substantial improvement ov er previous results from our group and the few other groups using this technique. The second wire is 1.45 mum long and 100 nm wide; its thickness is estimated at 5 nm. It has substantially higher resistivity: 1.1 +/- 0.45 mOMEGA cm, which is attributed to minute near discontinuities in the wire. Finally, lines have been written 4 nm thick, 35 nm wide, and 2 mum long, which are unfortunately not long enough to allow resistivity measurements. Reliability problems of this complex STM/SEM system are discussed and new designs for a more dependable system are described. A new technique for rapid imaging of large areas (10-20 mum square) with the STM is being developed and preliminary results are presented here.