Investigations of Local Electrical Characteristics of a Pentacene Thin Film by Point-Contact Current Imaging Atomic Force Microscopy

Abstract

We performed local electrical property measurements on a pentacene semiconducting thin film, which was connected to a Pt electrode, using point-contact current imaging atomic force microscopy (PCI-AFM). The measurements were conducted not only under ambient conditions, but also in a vacuum on the same film by employing the Q-control method to reduce the settling time of the cantilever oscillation amplitude. In both environments, the obtained current images showed that the current in the film gradually decreased with the increasing distance from the electrode. We also found differences in the threshold voltage among the grains and discontinuities in the apparent resistance at the grain boundaries, which suggest that the conductance of the thin film is limited by the grain boundaries. Moreover, by comparison of the measurement results on the same grains in air and in a vacuum, an increase in the current and a shift in the threshold voltage to a positive value in air were observed, which can be attributed to the exposure of the film to atmospheric oxygen.

Direct investigations of the interface impedance of organic field-effect transistors with self-assembled-monolayer-modified electrodes

“…These images indicate that the SAM modification process had little influence on the surface properties of the SiO 2 layer, which agrees with the fact that the thiol group of PFBT molecule links to metal surfaces. In addition, it is also consistent with the previous studies reporting the correlation between the grain size and the threshold voltage of the OFETs [19,20]. Therefore, the improvement in the device mobility is attributed to the change in the local electrical properties at the electrodeechannel interfaces.…”

Imaging prototypical aromatic molecules on insulating surfaces: a review

“…Charges injected into a single pentacene island remain localized if the island is disordered while it is delocalized over the whole island for ordered islands [48]. Varying the distance of the resistance measurement with respect to an in-plane electrode, the resistance across a grain boundary was found to be large compared to the resistance of a grain for both sexithiophene [16] and pentacene [143]. Similar results were found using two SFM probes also for sexithiophene [15].…”

Employing spatial, hybrid and amplitude roughness parameters for unveiling the surface roughness features of mineral and organic admixtures

“…All the methods employed were developed and implemented in the contexts of evaluating surface roughness properties of the specimens under simulation approaches. Such approaches can be conducted fundamentally and distinct methodologies employed during the evaluation procedures are documented elsewhere [ 34 , [46] , [47] , [48] , [49] ].…”