UHV deposition of titanium bis-phthalocyanine on the GaAs(1 0 0)-β2-(2 × 4) 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(1 0 0)-β2-(2 × 4) and highly oriented pyrolytic graphite (HOPG) has been carried out. An STM spectroscopic analysis on the local density of states has been also performed. In the case of GaAs as substrate, the STM images show that the molecules align themselves preferentially along the dimer rows, typical of the (2 × 4) reconstruction, thus revealing the fundamental role of the interaction between the molecule and the reconstructed substrate in orienting the adsorbed molecules. In the case of HOPG, the images indicate the formation of irregular channels thus suggesting an auto-assembling of the molecules between themselves rather than a strong interaction with the substrate, as in the GaAs case.