Investigation of STM tip influence on the recorded position of the Shockley surface state on Au(1Â 1Â 1)

Current imaging tunneling spectroscopy (CITS) carried out in UHV at room temperature was used to study the electronic structure of the Au(1 1 1) surface in the range of −1.0-1.0 eV. The CITS experiment showed the existence of the Shockley surface state (SS) located in range 0.3-0.7 eV below the Fermi level. A wide range of SS locations is explained by the influence of the electronic structure of the tip on the measurement of the tunneling current. This hypothesis is supported by a simple theoretical model. Finally, a new method of CITS analysis is suggested. The method is related to counting local maxima locations on each tunneling spectroscopy curve and building a histogram. This method of data analysis allows finding statistically the most frequently appearing maxima. Using the histogram method the location of the SS is estimated to 0.47 eV below the Fermi level.