EFFECT OF SUBSTRATE-TEMPERATURE IN CHLOROALUMINUM PHTHALOCYANINE THIN-FILMS DEPOSITION STUDIED BY SCANNING-TUNNELING-MICROSCOPY AND TUNNELING SPECTROSCOPY

The AlPcCl films deposited on a KCl substrate at two different substra te temperatures(T-s -120 degrees C and 180 degrees C) with the average film thickness of 100 nm were investigated using scanning tunneling m icroscopy (STM) and tunneling spectroscopy (TS). The films were transf erred onto HOPG in order to make STM and TS measurements possible. The STM as well as the electron diffraction measurement exhibited the amo rphous and crystalline structures for T-s of - 120 degrees C and 180 d egrees C, respectively. The potential region with low conductance (con ductance well) in the dI/dV curve was smaller (T-s, - 120 degrees C) a nd larger (T-s, 180 degrees C) when compared with the band gap value o f the AlPcCl film (T-s, 180 degrees C) which we previously evaluated f rom the optical absorption measurement. We estimated the band bending with the assistance of the carrier concentration obtained from the ESR measurement, it is supposed that the electronic states created within the band gap caused the vanishing of band bending change for T-s of - 120 degrees C, leading to the decrease of conductance well. On the ot her hand, the band bending was found to be crucial for T-s of 180 degr ees C, which possibly resulted in the widening of conductance well. (C ) 1998 Elsevier Science S.A.