Pt(100) quasihexagonal reconstruction: A comparison between scanning tunneling microscopy data and effective medium theory simulation calculations

The interpretation of scanning tunneling microscopy (STM) data is usually limited to first-layer effects, but with increasing resolution of the STM images deeper-layer effects may also become visible in the top-layer corrugations. We have investigated the clean Pt(100) surface, which is known to be pseudohexagonally reconstructed and for which there is some evidence for a second-layer reconstruction. The big unit cell makes it difficult to investigate the deeper layers by traditional methods like low-energy-electron diffraction (LEED), We have, therefore, used a ''fingerprint'' technique to compare highly resolved STM data of the clean Pt(100) surface to effective-medium-theory simulation calculations in order to determine the geometric structure of the second atomic layer. We were able to show that STM can be sensitive to deeper layer effects and that excellent agreement could only be achieved for an unreconstructed second layer. The simulation results also agree well with the corrugations determined by LEED whereas the maximum corrugation amplitude is higher than previously derived from helium-diffraction measurements. [S0163-1829(97)05739-1].