A method employing STM for the estimation of relative changes in the work function of modified metal tips

I-z spectroscopy measurements using a scanning tunnelling microscope (STM) were carried out to determine the change in the work function of a W tip following one monolayer (1 ML) deposition of Ni and subsequent annealing at 700 K. The variation in the actual gap voltage obtained from the I-z data of the clean tip was used in the calculation. The estimated values of the change in work function, 016 eV and 0.59 eV, for as-deposited and annealed tips, respectively match closely with the reported values. The method is generally applicable to chemically modified metal tips.