Nanolithography by enhanced laser irradiation

A general model for the near-field optical intensity induced by a conductive tip under polarized laser irradiation is developed for the laser-assisted SPM. The calculations show that a 3:1 silver SPM tip can induce an optical field enhancement of 525 times on a gold substrate surface. Field enhancement and intensity profiles strongly depend on the tip-sample geometry, laser parameters and the dielectric properties of the tip and sample. The temperature rise was analyzed for the cases with and without tip-surface contact. Thermal expansion of the tip is calculated and compared with the tip-sample distance of an SPM junction to determine whether contact between the tip and sample surface occurred.