KEYWORDS: Dielectrics, Thin films, Transistors, Plasma, Electronics, Thin film devices, Thin film solar cells, Solar cells, Self-assembled monolayers, Aluminum
Ultrathin hybrid gate dielectrics composed of an inorganic metal oxide and an organic self-assembled monolayer are useful for low-voltage organic thin-film transistors by providing a large gate dielectric capacitance and minimizing gate leakage. In this work, we focus on the role of the thin metal oxide in the hybrid gate dielectric, by investigating a plasma-grown aluminum oxide and the effects of the plasma power and duration on the growth of the aluminum oxide and the resulting properties of the gate dielectric in organic TFTs.
Ultrathin, oxygen-plasma-grown aluminum oxide layers form high-quality gate oxides in hybrid gate dielectrics for low-voltage organic thin-film transistors. In this work, we have investigated the materials properties of the AlOx layer, such as the thickness and the composition, using the techniques of high-resolution transmission electron microscopy and atom probe tomography to get atomic scale resolution information. We correlate these materials properties with the superior dielectric properties of the plasma-grown AlOx layer and the performance of AlOx-based hybrid gate dielectrics for organic TFTs.
Post-deposition semiconductor dewetting is the transformation of a (nearly) closed organic-semiconductor monolayer into separated individual islands of multilayer height [1]. We have recently observed this phenomenon in both ultra-thin (1-3 nm) and thin (25-40 nm) films of the small-molecule semiconductor dinaphthothienothiophene (DNTT) [2,3]. Since the gate-field-induced carrier channel is located in close vicinity to the semiconductor-dielectric interface, the accelerated pace of dewetting of ultra-thin semiconductor films is relevant to the performance and stability of organic thin-film transistors (TFTs). We have therefore fabricated bottom-gate, bottom-contact TFTs based on 2 nm and 25 nm-thick DNTT films. Compared to the relatively stable charge-carrier mobility of 1.1 cm2/Vs for the 25-nm-DNTT TFT, the 2-nm-DNTT TFTs show a sharp decrease from 0.2 cm2/Vs to 0.011 cm2/Vs over 72 hours after fabrication. To stabilize the TFT performance, we have explored strategies to prevent ultra-thin DNTT films from dewetting, including substrate cooling and semiconductor encapsulation, and fabricated stable DNTT TFTs with monolayer semiconductor thickness. Encapsulation with vacuum-deposited polytetrafluoroethene (PTFE) or titanyl phthalocyanine (TiOPc) leads to a relative decrease in mobility by only 12% and 44%, compared to 99.6% for TFTs without encapsulation over 28 hours after device fabrication. [1]T. Breuer et al., ACS Appl. Mater. Interfaces, 9, 8384, (2017). [2]K. Takimiya et al., Sci. Technol. Adv. Mater., 8, 273, (2007). [3]U. Zschieschang et al., Organic Eletronics, 12, 1370, (2011).
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.