Nanostructure fabrication using laser field enhancement in the near field of a scanning tunneling microscope tip

Abstract

The scanning tunneling microscope (STM) has been combined with laser excitation and was used for modification of metal surfaces in air. This technique enables processing of structures with a lateral resolution of approximately 10 nm. The form of the created features ranges from craters and ditches to hillocks. The process has been demonstrated on gold and gold/palladium substrates by utilization of tungsten, silver, and platin/iridium tips. Using pure silver tips or silver-coated tungsten tips, a transfer of tip atoms to the substrate occurred. In the case of uncoated tungsten tips, we observed substrate evaporation and surface grain reorganization at low laser intensities, respectively. No distortion of the employed tips during the structuring process was observed. Several future oriented applications are conceivable, such as, for example, high density data storage and fresnel optics for x rays.

Time-resolved measurements of the response of a STM tip upon illumination with a nanosecond laser pulse

“…The physical reasons for these possibilities are not clear. On one hand it is proposed that the metallic tip produces a local enhancement of the optical radiation similar to the well-known surface-enhanced Raman effect [2][3][4]6]. On the other hand the possibility of thermal expansion and therefore of mechanical contact is also discussed [5].…”

Controlling and tuning strong optical field gradients at a local probe microscope tip apex

“…In fact, this interaction does not only play a central role in apertureless SNOM, [1][2][3][4][5][6][7] but has also been implemented in local probe assisted nanoengineering, as for example in STM assisted nano-lithography. 8 A typical geometry for this problem is depicted in Fig. 1.…”

Optical near-field effects in surface nanostructuring and laser cleaning

“…One approach in this respect consisted of the illumination of the tip of a scanning tunnelling microscope (STM) with a pulsed laser. Structures with lateral dimensions below 30 nm and therefore well below λ/2 could be produced underneath the tip [ 1,2]. It was proposed that the strong enhancement of the electromagnetic field in the vicinity of a tip, suggested e. g. by the calculations in [3], is responsible for this.…”