Laser nano-engineering with the assistance of scanning probe microscope and optical resonance in microparticles

Optical and thermal processes of an STM junction under laser irradiation were summarized. A general model for the near field of a tip, under polarised laser irradiation is presented in the case of imaging and processing by a laser-assisted scanning probe microscope (SPM). The near field of a tip was calculated using the method of moments. Our calculations show that a 3:1 silver SPM tip can achieve an optical field enhancement of /spl times/525 on a gold substrate surface. With such a large SPM tip, plasma resonance can be neglected, and the optical enhancement in this case is much less than that predicted for small conductive particle models. Field enhancement and intensity profiles strongly depend on the tip-sample geometry, laser properties and the dielectric properties of the tips and samples. The model can be used for rigorous calculations of the near field of a tip in a laser-assisted SPM. The temperature rise was analyzed in the cases of contact and non-contact occurring between the tip apex and the sample surface. Thermal expansion of the tip can be calculated and compared with the tip-sample distance of an STM junction to determine whether contact between the tip and sample surface occurs or not.