Abstract
The electrical properties of self-assembled organic crystalline nanofibers are studied by integrating these on field-effect transistor platforms using both top and bottom contact configurations. In the staggered geometries, where the nanofibers are sandwiched between the gate and the source-drain electrodes, a better electrical conduction is observed when compared to the coplanar geometry where the nanofibers are placed over the gate and the source-drain electrodes. Qualitatively different output characteristics were observed for top and bottom contact devices reflecting the significantly different contact resistances. Bottom contact devices are dominated by contact effects, while the top contact device characteristics are determined by the nanofiber bulk properties. It is found that the contact resistance is lower for crystalline nanofibers when compared to amorphous thin films. These results shed light on the charge injection and transport properties for such organic nanostructures and thus constitute a significant step forward toward a nanofiber-based light-emitting device.
Highlights
In the last decade, much attention has been given to one-dimensional nanostructures due to their intriguing physics and in particular their application potential within for example electronics and optoelectronics [1,2,3]
Since the electrical characteristics of organic field-effect transistor (FET) are known to depend on the exact transistor geometry [26], we have studied three transistor geometries: bottom contact/bottom gate (BC/BG), bottom contact/top gate (BC/TG), and top contact/bottom gate (TC/BG) [26,27]
The TC/BG configuration exhibits the highest output current. We propose that this is due to the smaller contact resistance between the nanofibers and the electrodes due to deposition of the electrodes under vacuum, which prevents water residues in the nanofiber-electrode interface in contrast to the bottom contact devices where the nanofiber-electrode interface is created under humid conditions during the transfer
Summary
Much attention has been given to one-dimensional nanostructures due to their intriguing physics and in particular their application potential within for example electronics and optoelectronics [1,2,3]. Inorganic semiconducting crystalline nanowires made from, e.g., Si or III-V materials have been the focus of much research due to the ability to synthesize these in large numbers with well-defined properties, which has led to the demonstration of nanowire field-effect transistors [4,5], multicolor light sources [6], lasers [7], photo detectors [8,9], and solar cells [10,11]. One example is organic materials based on small molecules, which can be self-assembled into crystalline nanostructures. This can be done either from solution [12,13] or by vapor deposition [14,15].
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