Jul 27, 2011
Multiple-scanning-probe force microscope measures electrical transport in graphene flakes
Technology for measuring the electrical transport properties of nano- and micro-sized samples is a key factor in promoting the practical use of rapidly developed functional materials. In many cases these measurements are performed using fixed electrodes fabricated by a lithographic technique. However, the residue of resist materials introduced during lithographic processes may affect the properties of the measured object. Also, it is not always easy to place electrodes at desired positions on randomly distributed microscopic objects such as exfoliated graphene flakes on silicon dioxide (SiO2) films.
To tackle these challenges, a team from the National Institute for Materials Sciences (NIMS) and HORIBA Ltd, Japan, has developed a multiple-scanning-probe microscope (MSPM); a direct measurement tool for characterizing nano/micro conductors using two or more probes individually controlled in the manner of scanning probe microscopy.
A specially arranged tuning fork probe, which can be operated in vacuum, air and liquid environments, is used as a self-detection force sensor to operate the MSPM as an MSPFM, namely, in frequency modulation atomic force microscopy (AFM) mode.
The group demonstrated simultaneous AFM imaging with four independent probes closely positioned around the same microscopic feature on the sample surface. Four-terminal electrical measurement is performed in air by placing each probe electrode in contact with a graphene flake exfoliated on a SiO2 film. The sheet resistance of the flake is then measured by the van der Pauw method.
The MSPFM has the potential to measure the intrinsic electrical properties of microscopic materials regardless of the conductivity of the substrate without using a scanning electron microscope.
The team's results provide a new approach to probing nano/micron-scale signal transfer in a wide range of materials in various environments, such as in ultrahigh vacuum, air and liquid.
More details can be found in the journal Nanotechnology.
About the author
The study was conducted by researchers from the National Institute for Materials Science (NIMS) and HORIBA, Ltd. Seiji Higuchi developed an integrated control system for a multiple-scanning-probe microscope during a doctoral course of material science and engineering at the graduate school of pure and applied sciences, University of Tsukuba. He is currently a visiting researcher at NIMS from HORIBA, Ltd. In the company, he is developing and marketing the application of multiple-scanning-probe microscopy. Osamu Kubo and Hiromi Kuramochi are researchers from the International Center for Materials Nanoarchitectonics (MANA), NIMS. Tomonobu Nakayama and Masakazu Aono are the principal investigator and the director-general of MANA, NIMS, respectively.