Investigating the impact of SEM chamber conditions and imaging parameters on contact resistance ofin situnanoprobing

Abstract

In this paper, we investigate the impact of vacuum chamber conditions (cleanliness level and vacuum pressure) and imaging parameters (magnification and acceleration voltage) of scanning electron microscopy (SEM) on the contact resistance of two-point in situ nanoprobing of nanomaterials. Using two typical types of conductive nanoprobe, two-point nanoprobing is performed on silicon nanowires, during which changing trends of the nanoprobing contact resistance with the SEM chamber conditions and imaging parameters are quantified. The mechanisms underlying the experimental observations are also explained. Through systematically adjusting the experimental parameters, the probe-sample contact resistance is significantly reduced from the mega-ohm level to the kilo-ohm level. The experimental results can serve as a guideline to evaluate electrical contacts of nanoprobing and instruct how to reduce the contact resistance in SEM-based, two-point nanoprobing.

Effect of Applied Pressure on the Electrical Resistance of Carbon Nanotube Fibers

“…Based upon our prior work [16], this suggests that there is no change in the band gap of the CNTs, which is certainly not sufficient to result in the 2 order of magnitude increase in electrical resistance observed with a probe displacement of 200 nm (cf., Figure 3). For a fiber prepared from individual filaments (in this case CNTs) it would be expected that the electrical resistance would decrease with increased pressure due to the improved contact between the probe and the fiber as well as between the individual filaments [21]. Surprisingly, for CNT fiber, we have observed the opposite.…”

“…Although it is known that strain can increase the measured resistance of a material due to lattice stretching [22], this is unlikely to cause a 6-order magnitude increase in electrical resistance that is observed here (cf., Figure 4). It is known that pressure-induced strain can cause an opening on the electronic band gap in individual carbon nanotubes [23][24][25][26]; however, we do not believe that this is the case here as the opening of the band gap would not cause as big For a fiber prepared from individual filaments (in this case CNTs) it would be expected that the electrical resistance would decrease with increased pressure due to the improved contact between the probe and the fiber as well as between the individual filaments [21]. Surprisingly, for CNT fiber, we have observed the opposite.…”

“…For a fiber prepared from individual filaments (in this case CNTs) it would be expected that the electrical resistance would decrease with increased pressure due to the improved contact between the probe and the fiber as well as between the individual filaments [ 21 ]. Surprisingly, for CNT fiber, we have observed the opposite.…”

Optically and electrically invariant multi-color single InGaN/GaN nanowire light-emitting diodes on a silicon substrate under mechanical compression

“…During in-situ optoelectronic characterization of nanomaterials, the contact resistance issue (between the nanomaterial and the contact electrode/probe) could significantly affect the measured optoelectronic properties. 27 Besides, conventional nanolithography methods for patterning electrodes on a sample involve a chemical or physical treatment of the sample that may alter its optoelectronic properties. 28,29 By integrating a scanning tunneling microscopy (STM) probe inside an SEM chamber, the effect of mechanical strain on the photocurrent and the electrical properties of single GaA nanowires was investigated.…”

Characterizing the electrical breakdown properties of single n-i-n-n+:GaN nanowires

“…We performed two-point electrical in-situ nanoprobing of the as-grown single n-i-n-n þ :GaN NWs inside a SEM by following a previously developed protocol. 19 Compared with the conventional nanolithography based techniques for establishing electrical contacts with a single NW, 20 in-situ nanoprobing is relatively easy to perform, is more rapid, and allows the testing of many NWs with less experimental efforts for examining the effect of different growth parameters on the material's electrical properties. More importantly, nanolithography for patterning electrodes on a NW involves chemical treatment of the NW that may alter the NW's electrical properties, 20,21 but this is avoided in in-situ nanoprobing.…”