Novel Nanosized Patterning Techniques Using An Electropulsed Scanning Probe Microscope

Scanning Probe Microscopes (SPM) have been used to change surfaces at nanometer scales. We report the deposition of user defined patterns in a controlled manner using an electropulsed SPM. The patterns were fabricated by applying -12 V electrical pulses in the 10 to 40 Hz range between a commercial CoCr conductive tip and a crystalline n-doped Si wafer. The tip damage during deposition is negligible as measurements on the same surface region before and after deposition show no detectable differences. Immediately after deposition the same tip is used for measuring the fabricated patterns. Applying one isolated electrical pulse results in a pixel with a typical size of the order of 30 nm. By combining the scanning ability of the SPM with the atmospheric deposition induced by electrical pulses on the tip, patterns can be fabricated. For example, by applying electrical pulses during a 25 nm x 800 nm tip scan in AFM tapping mode, at 40 Hz, lines with 65 nm width by 828 nm length were obtained (in good agreement with the expected dimensions of 55 nm x 830 nm derived from the pixel size and the scan range). The height of the deposited patterns is of the order of 2 to 3 nm, and was found to increase with the density of scan lines. The RMS roughness of the deposited material is shown to be strongly dependent on the electrical pulse frequency. The smoother pattern surface results from the 40 Hz pulse frequency. No deposition was observed at higher frequencies.