STRUCTURAL ASPECTS OF TETRAMETHYLTHIOUREA ADSORPTION ON AU(111) ELECTRODES INVESTIGATED BY IN-SITU SCANNING-TUNNELING-MICROSCOPY

We have examined tetramethylthiourea (TMTU) adsorption on Au(lll) with capacitance measurements and in situ scanning tunnelling microscopy (STM). Capacitance measurements of the TMTU-containing solution indicate that the organic molecule is adsorbed over a wide potential range. High resolution STM images at +20 mV are totally different to those in the absence of TMTU and point to an ordered structure of the organic adsorbate. Three distinctive bright spots are seen in the STM images. A model has been developed with the molecules lying near to horizontal on the surface, forming a (3 x 3) adlayer.