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 chemica l vapor deposition (CVD). Our STM is coupled to a commercial scanning electron microscope (SEM), which allows us to align the tip with pre-e xisting contact pads for electrical measurements of the nanowires. Thu s 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 t emperature. 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. T his indicates that the nickel deposits are fairly pure, and is consist ent with Auger analysis made on micron-size deposits: there is at leas t 95% nickel in these deposits. This is a substantial improvement ov e r 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 thick ness is estimated at 5 nm. It has substantially higher resistivity: 1. 1 +/- 0.45 mOMEGA cm, which is attributed to minute near discontinuiti es in the wire. Finally, lines have been written 4 nm thick, 35 nm wid e, and 2 mum long, which are unfortunately not long enough to allow re sistivity measurements. Reliability problems of this complex STM/SEM s ystem are discussed and new designs for a more dependable system are d escribed. A new technique for rapid imaging of large areas (10-20 mum square) with the STM is being developed and preliminary results are pr esented here.