Nanogrooved silicon dioxide (SiO2) was used to fabricate organic field-effect transistors (OFETs) with a mobility approaching 50 cm2 V-1s-1. We expect similar, if not better, results using organic dielectric layers, which are also useful for flexible OFETs. We have fabricated nanogrooved organic dielectric layers for high-performance flexible OFETs. Poly(4-vinylphenol) (PVP) and 4,4’-(hexafluoroisopropylidene)diphthalic anhydride (HDA) are used as dielectric and crosslinker materials, respectively. The molecular structures are shown below.

Nanogrooved PVP:HDA (n-PVP:HDA) films are prepared by nanoimprinting with a ceramic stamp fabricated on nanogrooved SiO2 master mold. Nanostructure on the n-PVP:HDA film is investigated by using a atomic force microscopy (AFM), and compared with those of the SiO2 master mold and pristine PVP:HDA films. Nanoimprinting at the glass transition temperature of PVP (approximately 150°C) yields nanogrooves with a depth of 3-6 nm comparable to those on SiO2. Nanoimprinting and AFM imaging carried out by B. H. Lee, postdoctoral researcher in Physics supported by NSF-DMR-0856060. Nanoimprint was performed in the UCSB nanofabrication facility, part of the NSF funded NNIN network. Manuscript is in preparation.

High-mobility organic field-effect transistors fabricated on flexible substrates

Alan J. Heeger, University of California-Santa Barbara, DMR 0856060

Figure: AFM topography images of (a) nanogrooved SiO2 master mold, (b) ceramic stamp with positive polarity, (c) pristine PVP:HDA, and (d) n-PVP:HDA replica. These images demonstrate that the shallow nanogrooves comparable to those on SiO2 were successfully fabricated by using nanoimprint lithography.

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High-mobility organic field-effect transistors fabricated on flexible substrates

Alan J. Heeger, University of California-Santa Barbara, DMR 0856060

Education

The study of flexible OFETs is a good example of interdisciplinary science involving a combination of nanoscience, chemistry, materials science, and device physics. B. H. Lee, a postdoctoral researcher, used nanoimprint lithography, an approach generally important to making nanostructures on nanometer length scales. These length scales are difficult to achieve by using other conventional lithographic technologies. The device fabrication, optimization, and transistor measurements also done by B. H. Lee required him to develop skills in device physics and film preparation which are important in developing emerging microelectronics technologies. For example, a separate but related project, was conducted in collaboration with the Mitsubishi Chemical company.

Broader Involvement

Flexible organic field-effect transistors fabricated by low-cost printing technology continue to be of interest• They offer unique flexible circuits;• They enable thin, wearable, light-weight

and rugged products; • They can be manufactured by high

throughput roll to roll processes. • Professor Heeger has served as Board

Member on CBRITE Inc, Cynvenio Inc. and Cytomyx Inc.

• Professor Heeger recently established a new research center in China with collaborator Prof. Jiang; Jiang’s expertise in in the area of superhydrophobic and superhydrofillic syrfaces. This unique processing on conjugated polymers offers promise for improved device performance

• Professor Heeger regularly gives invited (Keynote and Plenary) lectures at conferences in the U.S., Europe and Asia.