Keithley 2481 Zyvex App Note free download

File name 2481 Zyvex App Note.pdf

Number 2481 I-V Measurements of Nanoscale Wires and Application Note Tubes with the Model 4200-SCS and Zyvex Series S100 Nanomanipulator Introduction Methods and Techniques It is difficult to characterize very small circuit elements electrically in Unlike general-purpose measurements and I-V curve generation on current-generation semiconductors, as well as in next-generation macro- and micro-scale components and materials, measurements on nanoscale electronics and materials such as Single Wall Carbon molecular wires and carbon nanotubes require special care and tech- Nanotubes (SWNT). Many prober systems can have unacceptably large niques. General-purpose resistance measurements and I-V curve genera- metal pad requirements, and manual mechanical probe stations with tion are often performed using a two-point electrical measurement tech- optical microscopes can't resolve fine features. With standard gate nique. However, when the resistance to be measured is relatively low (as dimensions of less than 90nm and space budgets shrinking continuously, may be the case with molecular wires, semiconducting nanowires, and the smallest probe pad dimensions required for most prober systems carbon nanotubes) or when the resistance of the probes or the contacts remain fixed at about 50 microns. This limitation is largely the result of is relatively high, a four-point probe will yield more accurate results. the inaccuracy of probe movements and the size of the probe tips. These difficulties can be eliminated by combining a Keithley Model Theory of Two-Point Measurements 4200-SCS Semiconductor Characterization System with an advanced In order to determine a resistance, Ohm's law is used: R = V/I. A nanomanipulation system, such as the Zyvex S100 Nanomanipulation known current is sourced and flows through the unknown resistance. System (shown in Figure 1). This combination offers 5nm movement The voltage that develops across the resistance is measured and then precision with probe tip diameters of less than 20nm and current- the resistance is determined by dividing the measured voltage by the measuring capability better than 1pA. sourced current. A problem that occurs when using a two-wire setup is that the voltage is measured not only across the resistance in question, but includes the resistance of the leads and contacts as well (see Figure 2). When using an ohmmete