Ultrafast scanning tunneling microscopy with 1 nm resolution

Abstract

We present data demonstrating that junction-mixing scanning tunneling microscopy (JM–STM) can provide simultaneous picosecond time resolution and nanometer spatial resolution. Experiments were performed on an Au surface with a patterned Ti overlayer. Our measurements under ultrahigh vacuum conditions achieve a spatial resolution of 1 nm using the tunneling currents generated by 20 ps voltage transients. The observed contrast in a JM–STM signal is demonstrated to arise entirely from the difference in electronic structure between the Au and Ti surfaces. These results confirm that JM–STM signals originate in the tunnel junction and maintain the atomic-scale spatial resolution inherent in STM.

Colloquium: Time-resolved scanning tunneling microscopy

“…It should be mentioned here that the name timeresolved scanning tunneling microscopy was first used for the combination of STM with ͑quantum͒ optical techniques ͑Hamers and Cahill, 1991; Weiss et al, 1995;Feldstein et al, 1996;Groeneveld and van Kempen, 1996;Freeman et al, 1997;Gerstner et al, 2000;Khusnatdinov et al, 2000;Takeuchi et al, 2002;Terada et al, 2007͒. The high spatial resolution of the STM and the high temporal resolution offered by ultrashort laser pulses enable high bandwidth measurements based on the pump-probe technique.…”

Real-space imaging of transient carrier dynamics by nanoscale pump–probe microscopy

“…Hamers et al determined the recombination lifetime of photoexcited carriers in Si, in their pioneering work, by analyzing the observed surface photovoltage (SPV) by simulation [10], and a method that involves the combined use of an optical pulse pair and STM was proposed as photoconductive-gate STM (PG-STM) [11][12][13][14][15][16][17][18]. However, the spatial and temporal resolutions of the former method were limited to the 1 µm scale and laser-pulse repetition rate, respectively, and the PG-STM probes dI/dV or the quantity mediating the signal rather than the transient effect itself [18].…”

Laser-Combined Scanning Tunneling Microscopy on the Carrier Dynamics in Low-Temperature-Grown GaAs/AlGaAs/GaAs

“…Laser-combined scanning tunneling microscopy (STM) is a promising candidate, because the tunneling junction itself responds on a time scale of a few femtoseconds and thereby ultrafast dynamics can principally be studied by STM with ultrashort pulse laser techniques [4][5][6][7][8][9][10][11][12]. Recently, we have reported a novel microscopy technique that enables the visualization of subpicosecond carrier dynamics in nanometer-scale structures [13], that is, shakenpulse-pair-excited scanning tunneling microscopy (SPPX-STM) with a novel delay-time modulation method based on a pulse-picking technique [14][15][16][17][18][19][20][21].…”