Although organic thin film transistors (OTFTs) have significantly improved during the last years, the basic physical principles governing charge transport are still a challenge [1-2]. In this report correlations between pentacene OTFT growth conditions, morphology and electrical response were investigated by in-situ electrical characterization technique. This technique allows us to monitor the evolution of the channel current (drain-source current) during the deposition of the organic semiconductor. Deposition rate was changed systematically, whereas substrate temperature was held constant. The deposition time scales as the nominal thickness. Pentacene was thermally evaporated on Si/SiO2 substrates with gold electrodes in a bottomcontact architecture. During each deposition, drain-source current was measured every second while fixed gate-source and drain-source voltages were applied (Fig. 1a). After deposition an ex-situ morphological study was performed by using atomic force microscopy (AFM) (Fig. 1b), showing that the correlation length scales from 1.0 mm to 0.35 mm when the deposition rate increases from 0.1 to 2.5 ML/min. Following the analysis in ref.[3], we have devised an effective method to analyze the contribution of every layer to the total drainsource current. The derivative with respect to the thickness is shown to scale as the density of carriers. We find that the decay length scales of the derivative vary for the different deposition rates, indicating that the effective Debye length increases with the deposition rate. In detail, the calculated effective Debye length varies between 0.33 nm and 2.64 nm when the deposition rate varies between 0.1 and 2.5 ML/min, respectively.

In situ and real-time electrical monitoring of pentacene field-effect transistors

SCORZONI, Andrea;
2009

Abstract

Although organic thin film transistors (OTFTs) have significantly improved during the last years, the basic physical principles governing charge transport are still a challenge [1-2]. In this report correlations between pentacene OTFT growth conditions, morphology and electrical response were investigated by in-situ electrical characterization technique. This technique allows us to monitor the evolution of the channel current (drain-source current) during the deposition of the organic semiconductor. Deposition rate was changed systematically, whereas substrate temperature was held constant. The deposition time scales as the nominal thickness. Pentacene was thermally evaporated on Si/SiO2 substrates with gold electrodes in a bottomcontact architecture. During each deposition, drain-source current was measured every second while fixed gate-source and drain-source voltages were applied (Fig. 1a). After deposition an ex-situ morphological study was performed by using atomic force microscopy (AFM) (Fig. 1b), showing that the correlation length scales from 1.0 mm to 0.35 mm when the deposition rate increases from 0.1 to 2.5 ML/min. Following the analysis in ref.[3], we have devised an effective method to analyze the contribution of every layer to the total drainsource current. The derivative with respect to the thickness is shown to scale as the density of carriers. We find that the decay length scales of the derivative vary for the different deposition rates, indicating that the effective Debye length increases with the deposition rate. In detail, the calculated effective Debye length varies between 0.33 nm and 2.64 nm when the deposition rate varies between 0.1 and 2.5 ML/min, respectively.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11391/134873
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