Growth of 3,4,9,10-perylenetetracarboxylic-dianhydride crystallites on noble metal surfaces

The growth of organic crystallites formed by 3,4,9,10-perylenetetracarboxylic-dianhydride (PTCDA) has been investigated by scanning tunneling microscopy on Cu(110), Cu(111) and Au(111). For the chosen parameters PTCDA exhibits Stranski-Krastanov growth. If the average coverage exceeds about 3-5 monolayers the formation of crystalline islands begins. Working at very low tunneling currents it has been possible to obtain molecular resolved images of crystallites formed by up to 100 molecular layers, while the overall coverage has a value of about 10-20 monolayers. Since the side walls typically exhibit a moderate slope in the range of 14-20degrees their structure may be as well analyzed as the flat top layer. As will be presented it is not only possible to determine the unit cell within the molecular layer but also their relative displacement between subsequent layers. A comparison between the 3D structures of several crystals will be given. (C) 2004 Elsevier B.V. All rights reserved.