Colloquium: Time-resolved scanning tunneling microscopy

Abstract

Scanning tunneling microscopy has revolutionized our ability to image, study, and manipulate solid surfaces on the size scale of atoms. One important limitation of the scanning tunneling microscope ͑STM͒ is, however, its poor time resolution. Recording a standard image with a STM typically takes about a fraction of a second for a fast scanning STM to several tens of seconds for a standard STM. The time resolution of a STM can, however, be significantly enhanced by at least several orders of magnitude. Here various methods are reviewed that are applied in order to significantly improve the time resolution of STM. These methods include high-speed or video STM, atom-tracking STM, and monitoring of the open feedback loop current or closed feedback loop z-piezo-voltage signals as a function of time. An analysis of the time-resolved STM data allows one to map out the potential landscape of the system under study.

Quantitative mapping of fast voltage pulses in tunnel junctions by plasmonic luminescence

“…Scanning probe microscope studies focus increasingly on measuring fast time-dependent processes at atomic dimensions, such as spin [1][2][3][4] and charge 5,6 dynamics or molecular motion. [7][8][9][10] Heterodyne frequency mixing 11 and pump-probe excitation schemes 2,[12][13][14][15] have been put forward as techniques to measure repetitive variations of the tunnel current in a scanning tunneling microscope (STM). Such techniques overcome practical limitations caused by the small bandwidth of high-gain current amplifiers and circumvent shot noise problems that arise in fast measurements of small electric currents.…”

Laser and voltage manipulation of bistable Si dopants in the GaAs (110) surface

“…Furthermore, an analysis of the residence times of the Si − i and Si + d states can show that the switching process is fully random and allows the extraction of the relevant relaxation times. 22 …”

The Art of Catching and Probing Single Molecules

“…For each measurement the voltage is repeatedly ramped (ten times) from +1.5 V to -1.5 V as shown in the bottom section. During the whole measurement the feedback loop of the STM is disabled (97). In addition, after each I-V trace, the STM tip is moved 0.05 nm closer or away from the substrate as shown in the top section.…”

“…Other examples of time-resolved STM measurements include molecular rotors of butyl sulphide (142) (t-Bu) 4 -ZnPc (143), flipping dimers (37,(144)(145)(146), and flickering of single diarylethene molecules (147). All these studies target a single molecule on a surface where the dynamical and conformational events have been studied (43,97). However, there have not been any time-resolved STM studies on molecular self-assemblies yet.…”