Abstract
We have successfully designed the geometry of the microwave cavity and the thin metal electrode, achieving resonance of the microwave cavity with the metal-insulator-semiconductor (MIS) device structure. This very simple MIS device operates in the cavity, where charge carriers are injected quantitatively by an applied bias at the insulator-semiconductor interface. The local motion of the charge carriers was clearly probed through the applied external microwave field, also giving the quantitative responses to the injected charge carrier density and charge/discharge characteristics. By means of the present measurement system named field-induced time-resolved microwave conductivity (FI-TRMC), the pentacene thin film in the MIS device allowed the evaluation of the hole and electron mobility at the insulator-semiconductor interface of 6.3 and 0.34 cm2 V−1 s−1, respectively. This is the first report on the direct, intrinsic, non-contact measurement of charge carrier mobility at interfaces that has been fully experimentally verified.
Highlights
Considering the nanometer-scale spatial motion of charge carriers in the field-induced time-resolved microwave conductivity (FI-TRMC) measurement, the range of motion of holes is assumed to be within a single domain
It should be noted that precise evaluation of hole mobility in pentacene by the flash photolysis time-resolved microwave conductivity (FP-TRMC) method has been limited so far, due to the lack of photo-induced charge carriers[37]
The present work provides the first evaluation of intrinsic hole mobility in pentacene materials
Summary
By means of the present measurement system named field-induced time-resolved microwave conductivity (FI-TRMC), the pentacene thin film in the MIS device allowed the evaluation of the hole and electron mobility at the insulator-semiconductor interface of 6.3 and 0.34 cm[2] V–1 s–1, respectively. Other studies focused on chargecarrier motion at interfaces, and used organic insulators such as poly(dimethylsiloxane) (PDMS), poly(methylmethacrylate) (PMMA) and self-assembled monolayers (SAM) to control the interfacial morphology[15,16,17] Building on this background, we report a novel technique named field-induced time-resolved microwave conductivity (FI-TRMC) for evaluating charge carrier mobility at the interface between insulators and semiconductors without grain boundary effects (Fig. 1).
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