A simple reliable preparation method of silver tips for scanning tunneling microscopy imaging with atomic resolution is presented. The procedure is based on two-step electrochemical processing; ac electropolishing and subsequent dc electroetching. The quality of the tip is improved by applying high bias voltage pulses while the tip is within tunneling range. This indicates that the end of the tips are sharpened by field evaporation of silver ions.

The relation between the efficiency of scanning tunneling microscope light emission (STM-LE) and the radius of tip curvature has been studied using silver tips. The emission efficiency increases with decreasing radius of tip curvature ρ for ρ>80 nm. This result agrees qualitatively with the prediction of a theory that includes the effect of electromagnetic retardation.

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