Threshold Voltage Shift in Organic Field Effect Transistors by Dipole-Monolayers on the Gate Insulator

Abstract

We demonstrate controllable shift of the threshold voltage and the turn-on voltage in pentacene thin film transistors and rubrene single crystal field effect transistors (FET) by the use of nine organosilanes with different functional groups. Prior to depositing the organic semiconductors, the organosilanes were applied to the SiO2 gate insulator from solution and form a self assembled monolayer (SAM). The observed shift of the transfer characteristics range from -2 to 50 V and can be related to the surface potential of the layer next to the transistor channel. Concomitantly the mobile charge carrier concentration at zero gate bias reaches up to 4*10^12/cm^2. In the single crystal FETs the measured transfer characteristics are also shifted, while essentially maintaining the high quality of the subthreshold swing. The shift of the transfer characteristics is governed by the built-in electric field of the SAM and can be explained using a simple energy level diagram. In the thin film devices, the subthreshold region is broadened, indicating that the SAM creates additional trap states, whose density is estimated to be of order 1*10^12/cm^2.

to be published in J. Appl. Phys

References in corpus (4)

• Field-Effect Transistors on Tetracene Single Crystals
• Field-induced charge transport at the surface of pentacene single crystals: a method to study charge dynamics of 2D electron systems in organic crystals
• Hole mobility in organic single crystals measured by a "flip-crystal" field-effect technique
• Bias-Dependent Generation and Quenching of Defects in Pentacene

Cited by in corpus (5)

• Electronic functionalization of the surface of organic semiconductors with self-assembled monolayers
• Controlling charge injection in organic field-effect transistors using self-assembled monolayers
• Interface Dipole : Effects on Threshold Voltage and Mobility for both Amorphous and Poly-crystalline Organic Field Effect Transistors
• Growth mechanisms of vapor-born polymer films
• Charge trapping in polymer transistors probed by terahertz spectroscopy and scanning probe potentiometry