Development of Laser-Induced Material Transfer in Nanometer Regions

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Functional organic molecules have been manipulated into fluorescent features as small as 450 nm on a polymer film using a method derived from laser ablation and laser implantation. The technique utilizes a piezodriver to position a pipette, having a 100 nm aperture and doped at the tip with organic molecules, tens of nanometers above a polymer film. The pipette is subsequently irradiated using 3 ns full width at half maximum laser pulses guided down to the tip by a fiber optic. This method of ablation confinement gives fine spatial control for placing functional organic molecules in a designated region and will have applications in optoelectronics. It could also be applied to drug delivery or biotechnology, because in principle, different molecules of diverse function can be manipulated in the same way for various purposes.A nanometer-scale surface modification of tin-doped indium oxide ITO in organic solvent was performed using a scanning tunneling microscope STM. The surface modification was attributed to localized field evaporation upon applying 10 V between the tunneling gap. White light sparking beneath the STM tip nanospark was observed during and after the surface modification. The addition of ionic species into the otherwise pure solvent also induced a nanospark even when applying lower voltages, but in this case, surface modification did not occur. It is considered that a part of the ITO becomes dissolved in solution as ions, which results in electron avalanche in the presence of these induced ions.Thus, fundamental knowledge was obtained for controlling laser-induced transfer of molecules, electrons, and ionic species at air/solid or liquid/solid surfaces.