A Study of Alkanethiol Film on Au by STM-Induced Luminescence

Abstract

Alkanethiol films on Au(111) surface have been studied by means of STM-induced luminescence in UHV. The spectra of STM-induced luminescence have been recorded at the same time as STM topography measurements with a spectrograph and a CCD detector. The spectrally resolved STM-induced photon map shows a similar contrast to the topography of alkanethiol film which has many etch pit structures created during the monolayer-film formation. The spectra for the etch pit region are compared with those for the top layer of the film. Those spectra shapes are nearly identical except for the difference of the emission intensity. The results indicate that the etch pit is also covered with an alkanethiol film in a similar way to the top layer of the film. The bias-voltage dependence of emission spectra has also been recorded in the range from 2.0 to 2.5 V. The results show that the spectra do not change their shape due to adsorption in this range of bias voltage within the experimental accuracy. The density of states due to adsorption has been discussed.