UHV deposition of titanium bis-phthalocyanine on the GaAsð100Þ-b2-ð2 4Þ and on graphite surface: an STM-UHV study

An STM-UHV study of the deposition of titanium bis-phthalocyanine under high vacuum (UHV) conditions on two different substrates such as GaAs (100)-beta 2-(2X4)and highly oriented pyrolytic graphite (HOPG) has been carried out. An STM spectroscopic analysis on the local density of states has also been performed .In the case of a GaAs as substrate , the STM images show that the molecules align themselves preferentially along the dimer rows , typical of 2X4 reconstruction , thus revealing the fundamental role of the interaction between the molecule and the reconstructed substrate in orenting the adsorbed molecules . In the case of HOPG the images indicate the formation of irregular channels thus suggesting an auto assembling of the molcules between themselves rather than a strong intraction with the substrate , as in the GAs case.