Near-Field Nanomodification of Metallic Thin Films Using Femtosecond Laser and Atomic Force Microscope
A. Chimmalgi, T. Y. Choi, C. P. Grigoropoulos, D. Wan and K. Komvopoulos
Keywords: Surface nanomodification/nanostructuring, femtosecond laser, AFM
Nanostructures, which have characteristic dimensions that are difficult to achieve by conventional optical lithography techniques, are finding ever-increasing applications in a variety of fields. For applications incorporating nanodevices to gain widespread acceptance, high resolution, reliability and throughput fabrication of these nanostructures is essential. Owing to the minimal thermal and mechanical damage, ultra-short pulsed laser radiation has been shown to be effective for precision material processing and surface micro-modification. In the present work, nanostructuring based on local field enhancement in the near-field of a surface probe microscope (SPM) sharp tip irradiated with femtosecond laser pulses has been studied. Results of nanostructuring of gold thin films utilizing an 800 nm Ti-Sapphire femtosecond laser system in conjunction with a commercial SPM in ambient air are presented. Figure 1 shows the dependence of the lateral feature size and depth on laser fluence. This method offers great flexibility in nanostructuring materials, as is shown in Fig. 2. High spatial resolution (~10-12 nm), flexibility in the choice of the substrate material and possibility of massive integration of the tips make this method an effective nanofabrication tool. Finite Difference Time Domain (FDTD) simulation results are presented for the spatial distribution of the laser field intensity beneath the tip (Fig. 3). The lateral resolution of the features from the experimental results and those predicted by the simulation results are in close agreement, clearly augmenting the proposition that field enhancement is the major factor responsible for the observed high lateral-resolution nanostructures. Potential applications of this method include nanolithography, nanodeposition, high-density data storage, and various biotechnology related applications.
NSTI Nanotech 2003 Conference Technical Program Abstract