Interface properties of OFETs based on an air‐stable n‐channel perylene tetracarboxylic diimide semiconductor

Abstract

In this study, several experimental techniques were employed to gain insights into the molecular interactions at the interfaces in organic field-effect transistors (OFETs). A self-assembled monolayer (SAM) was applied to the gate insulator to influence the interactions at the interface. Macroscopic electrical measurements, microscopic potentiometry, absorption/luminescence spectroscopy, and ellipsometry are combined to study top-contact OFETs based on an air-stable n-channel perylene derivative. They show clearly the advantage and capability of local electrical investigations compared to DC electrical characterization. The DC electrical measurements provide an improvement of the electron mobilities within the channel and unchanged contact resistances (within the error bars). Only the potentiometry allowed a deeper insight: It reveals a small decrease of the source contact resistance and a drain bias dependence of the mobility, which decreases due to prior hydrophobization of the SiO 2 gate insulator. This is attributed to different charge carrier trap concentrations and injection barriers in the organic semiconductor near the dielectric interface caused by diffused water which is discussed in detail. The optical absorption/luminescence spectroscopy and ellipsometry indicate an unchanged ordered molecular arrangement with a molecular tilt angle of (33 AE 4)8 with respect to the dielectric surface and rather weak intermolecular interaction for the devices with treated and untreated SiO 2 .

Nondestructive Method for Mapping Metal Contact Diffusion in In2O3 Thin-Film Transistors

“…In Figure 6 measured and simulated potential profiles are shown for the single-spin device at V DS = 3 V and at the various gate biases: V GS = 0 V and V GS = 5 V. It has been suggested in the literature that a lower surface potential through the channel for organic field-effect transistors indicates a lower mobility in the device. 39 Applying a gate bias introduces more carriers into the channel, thus increasing the conductivity of the In 2 O 3 channel.…”

Impact of the Gate Dielectric on Contact Resistance in High‐Mobility Organic Transistors

“…[22,25,26,38,39] Furthermore, all of these studies utilize bottom-gate top-contact (BG-TC) OTFT architectures and, therefore, may not completely eliminate the influence of OSC ordering and morphology on R C . Worldwide research has led to remarkable improvements in OTFT operating parameters, with dielectric and R C is rarely considered.…”

“…However, the relationship between the dielectric and R C is rarely considered. At the time of writing, there are only a few studies that either mention or explore how the dielectric impacts R C in OTFTs . Furthermore, all of these studies utilize bottom‐gate top‐contact (BG‐TC) OTFT architectures and, therefore, may not completely eliminate the influence of OSC ordering and morphology on R C .…”

Development of an improved Kelvin probe force microscope for accurate local potential measurements on biased electronic devices

“…As the electrical potential distribution is of particular interest for applications such as organic solar cells and organic field effect transistors (OFETs) (Palermo et al ., ), KPFM‐AM has also been extensively applied to characterise organic semiconductor‐based devices (Bürgi et al ., ; Nichols et al ., ; Puntambekar et al ., ; Bürgi et al ., ; Tal et al ., ) in order to investigate transport mechanisms and injection issues in OFETs. As the bottom‐contact structure is suited for potential measurements related to the channel charge distribution, KPFM‐AM imaging has been performed on various types of organic thin film devices based on pentacene (Hallam et al ., ; Nakamura et al ., ; Yogev et al ., ; Yogev et al ., ; Li et al ., ,b; Celle et al ., ; Wu et al ., ; Yogev & Rosenwaks, ), poly(3‐hexylthiophene) (P3HT) (Bürgi et al ., ; Liscio et al ., ; Kehrer et al ., ; Musumeci et al ., ), perylene (Luttich et al ., ) or oligothiopene (Afsharimani & Nysten, ). KPFM also facilitates the characterisation of the carrier injection process at electrode/organic semiconductor interfaces by measuring an injection potential drop (Bürgi et al ., ; Simonetti et al ., ).…”