Electrical Conduction Through Surface Superstructures Measured by Microscopic Four-Point Probes

Abstract

For in-situ measurements of the local electrical conductivity of well-defined crystal surfaces in ultrahigh vacuum, we have developed two kinds of microscopic four-point probe methods. One involves a "four-tip STM prober," in which four independently driven tips of a scanning tunneling microscope (STM) are used for measurements of four-point probe conductivity. The probe spacing can be changed from 500 nm to 1 mm. The other method involves monolithic micro-four-point probes, fabricated on silicon chips, whose probe spacing is fixed around several µm. These probes are installed in scanningelectron-microscopy/electron-diffraction chambers, in which the structures of sample surfaces and probe positions are observed in situ. The probes can be positioned precisely on aimed areas on the sample with the aid of piezoactuators. By the use of these machines, the surface sensitivity in conductivity measurements has been greatly enhanced compared with the macroscopic four-point probe method. Then the conduction through the topmost atomic layers (surface-state conductivity) and the influence of atomic steps on conductivity can be directly measured.

Plasmons in Pb nanowire arrays on Si(557): Between one and two dimensions

“…13 Therefore the study of electronic transport properties is of high interest, since this method can probe inherent electronic instabilities in these low-dimensional structures directly. [14][15][16] On an insulating substrate, the low-energy excitations necessary for electronic transport yield direct information about the electron density and electronic scattering properties within and in-between the wires. An alternative approach to get this information is the excitation of plasmons.…”

Pb nanowires on vicinal Si(111) surfaces: Effects of refacetting on transport

“…[3][4][5] Particularly, surface transport came recently in the focus of research since this method can probe inherent electronic instabilities in these low-dimensional structures directly. [6][7][8][9] The ultimate realization of an atomic wire can be done only by using well established concepts of self-assembly. While this approach works reliably on atomic length scales, long-range ordering is still demanding.…”

The conductivity of Bi(111) investigated with nanoscale four point probes

“…20 Four point probes have successfully been used to determine the surface conductance of semiconductor surfaces for cases where the conductance of the space charge layer and the bulk are negligible compared to that of the surface. [21][22][23][24] If the goal of the experiment is to determine the conductance due to the surface states of Bi, the best approach for doing this is to use a Bi single crystal as a sample, not a thin film with concomitant problems of quantum size effects and carriers induced at the film-substrate interface. We therefore performed our measurements on the ͑111͒ surface of Bi for which the electronic structure and even the lifetime of the surface states are well known.…”