title: Nonlinear femtosecond laser induced scanning tunneling microscopy.
abstract: We demonstrate ultrafast laser driven nonlinear scanning tunneling microscopy (STM), under ambient conditions. The design is an adaptation of the recently introduced cross-polarized double beat method, whereby z-polarized phase modulated fields are tightly focused at a tunneling junction consisting of a sharp tungsten tip and an optically transparent gold film as substrate. We demonstrate the prerequisites for ultrafast time-resolved STM through an operative mechanism of nonlinear laser field-driven tunneling. The spatial resolution of the nonlinear laser driven STM is determined by the local field intensity. Resolution of 0.3 nm-10 nm is demonstrated for the intensity dependent, exponential tunneling range. The demonstration is carried out on a junction consisting of tungsten tip and gold substrate. Nano-structured gold is used for imaging purposes, to highlight junction plasmon controlled tunneling in the conductivity limit.
authors.affiliation: Department of Chemistry, University of California, Irvine, California 92697-2025, USA.
authors.forename: Shirshendu
authors.initials: S
authors.lastname: Dey
authors.forename: Daniel
authors.initials: D
authors.lastname: Mirell
authors.forename: Alejandro Rodriguez
authors.initials: AR
authors.lastname: Perez
authors.forename: Joonhee
authors.initials: J
authors.lastname: Lee
authors.forename: V Ara
authors.initials: VA
authors.lastname: Apkarian