TIPS FOR SCANNING TUNNELING MICROSCOPY PRODUCED BY ELECTRON-BEAM-INDUCED DEPOSITION

Using contamination writing, we produced tips for scanning tunneling microscopy employing a JEOL 840F field emission scanning electron microscope at various acceleration voltages. Single-spot deposition experiments rendered fine tips of aspect ratios up to 90 at a growth rate of 0.1-1-mu-m per minute. Tip shank diameters below 200 nm were obtained. Full cone angles and cone length of the tips varied with the acceleration voltage. Experiments using a fine focused beam of 2 to 7 nm diameter, having a power density of 2 to 60 MW/cm2 at electron energies of 2 to 30 kV, rendered full cone angles of 50-degrees to 9-degrees and cone lengths of 100 to 1200 nm, respectively. The most important parameter of the tip, its radius, was found to be independent of the electron energy and amounted to 10 nm. Our method is well suited for routinely producing tips of the geometry required to image deep depressions and high steps at a higher resolution than can be obtained with electrochemically etched tips. STM tunneling experiments revealed sufficient conductivity of the deposited tips.