Scanning tunneling microscopy investigation of leucine and asparagine adsorbed on Cu(1 1 1)

Adsorption of leucine and asparagine on Cu(1 1 1) surface has been studied by means of scanning tunneling microscopy (STM) in ultra-high vacuum (UHV) conditions. It has been found that leucine can form (3 × 2) superstructure on Cu(1 1 1) and copper steps facet to 〈1 1 0〉 directions. On the basis of our STM images, model has been proposed for the Cu(1 1 1)(3 × 2)-leucine superstructure. The model explains quite naturally the motivation behind the step faceting process. On the other hand, asparagine cannot form any ordered superstructure on Cu(1 1 1) and no copper step faceting can be observed either. The role of amino group in the side chain played in asparagine adsorption geometry is discussed in this paper.