Reconstruction of the local density of states in Ag(111) surfaces using scanning tunneling potentiometry

Abstract

We present scanning tunneling microscopy data on clean Ag͑111͒ surfaces in UHV. Standing-wave patterns of the surface state are investigated to study the influence of a thermal step across the tunnel junction on constant current topographies. When constant current topographies are measured at bias voltages below 10 mV with temperature differences of more than a few kelvins between tip and sample, the apparent corrugation is drastically increased. Constant current topographies at low bias voltages and finite temperature differences do not reveal the true local density of states of the surface. The apparent corrugation is caused by a spatial varying thermovoltage superimposed to the bias voltage while scanning the sample's local density of states. With the help of scanning tunneling potentiometry, the correct local density of states of the sample can be reconstructed.

Distance dependence of tunneling thermovoltage on metal surfaces

“…Many examples of tunneling thermoelectric studies followed, including chemical imaging of metal nanoparticles 2 and molecular adlayers, 3 quantitative analysis of surface state electron scattering from steps and defects, 4,5 and even an atomically resolved thermoelectronic imaging of Si(111)-7Â7. Applied voltage that nullifies this thermoelectric current is termed tunneling thermovoltage.…”

Surface-State Enhancement of Tunneling Thermopower on the Ag(111) Surface

“…5 Thermovoltage in tunnel junctions is also the basis for scanning thermovoltage microscopy, a technique based on scanning tunneling microscopy introduced by Williams and Wickramasinghe nearly three decades ago. 6 Scanning thermovoltage is capable of attaining chemical information 7,8 and enhancing the sensitivity of quasiparticle interference imaging, 9,10 both of which valuably complement more traditional tunneling spectroscopy. 11 Although thermovoltage itself is relatively straightforward to measure in a nanoscale junction, establishing its relation to the transport properties of this junction is much more ambiguous.…”

Confined Friedel oscillations on Au(111) terraces probed by thermovoltage scanning tunneling microscopy

“…A spatial dependent expression is derived in Ref. [26] for V th (x) based on the following approximations [26,27]…”