Theory of scanning tunneling microscopy/spectroscopy for adsorbed surfaces and layer crystal surfaces

A method for theoretical simulation of the sccanning tunneling microscopy (STM) image and scanning tunneling spectroscopy (STS) spectra based on the LDA (local density functional approach) is applied for some chemisorption surfaces. For the Si(111)√3×√3-Ag surface, it is demonstrated that the modified HCT model results in a honeycomb-like distribution of the bright spots in the STM image. Effects of the microscopic geometry of the tip on the STM image are discussed for this surface. A strange transparent feature of the STM image for chemisorbed molecues or outermost layers is investigated both by analytical consideration and by theoretical simulation. The unique structure of the Ag(110)-O added row model is determined by optimization calculation and its experimental STM/STS data are reproduced by first-principles calculations.