Nanostructure fabrication and characterization on crystal silicon substrates using a laser-assisted scanning tunneling microscope

As a promising approach to meet the critical requirement of shrinking feature size down to nanoscales for future electronic industry, laser-assisted scanning tunneling microscope (STM) demonstrates its capabilities of nanostructure fabrication by means of extremely localized heating induced by highly concentrated and greatly enhanced optical field underneath the tips. In this study, nanostructures (dots and lines) were fabricated on heavily doped p-type silicon (110) substrates (0.01-0.09 Ω.cm) using the laser-assisted STM method. A 532 nm Nd-YAG pulsed laser with a pulse duration of 7 ns and a maximum peak power of 30 mJ was used. Electrochemically etched tungsten tips which play the roles of carrying tunneling current and generating highly concentrated optical field were utilized. An STM was employed to characterize the morphology and local density of state (LDOS) of the as-fabricated nanostructures. As such, band gaps inside and in the vicinity of nanostructures were derived. The impact of optical intensity and pulse number on geometrical and electronic properties of the nanostructures will be presented.