High voltage surface potential measurements in ambient conditions: Application to organic thin-film transistor injection and transport characterization

Journal Article · Mon Mar 28 04:00:00 EDT 2016 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4944884· OSTI ID:22594536

Reisdorffer, Frédéric; Simonetti, Olivier; Giraudet, Louis ^[1]; Rödel, Reinhold; Klauk, Hagen ^[2]

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1. Université de Reims Champagne Ardenne, Moulin de la Housse, 51100 Reims (France)
2. Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany)

A scanning surface potential measurement technique suited for thin-film devices operating under high voltages is reported. A commercial atomic force microscope has been customized to enable a feedback-controlled and secure surface potential measurement based on phase-shift detection under ambient conditions. Measurements of the local potential profile along the channel of bottom-gate organic thin-film transistors (TFTs) are shown to be useful to disentangle the contributions from the channel and contacts to the device performance. Intrinsic contact current-voltage characteristics have been measured on bottom-gate, top-contact (staggered) TFTs based on the small-molecule semiconductor dinaphtho[2,3-b:2′,3-f]thieno[3,2-b]thiophene (DNTT) and on bottom-gate, bottom-contact (coplanar) TFTs based on the semiconducting polymer polytriarylamine (PTAA). Injection has been found to be linear in the staggered DNTT TFTs and nonlinear in the coplanar PTAA TFTs. In both types of TFT, the injection efficiency has been found to improve with increasing gate bias in the accumulation regime. Contact resistances as low as 130 Ω cm have been measured in the DNTT TFTs. A method that eliminates the influence of bias-stress-induced threshold-voltage shifts when measuring the local charge-carrier mobility in the channel is also introduced, and intrinsic channel mobilities of 1.5 cm{sup 2} V{sup −1} s{sup −1} and 1.1 × 10{sup −3} cm{sup 2} V{sup −1} s{sup −1} have been determined for DNTT and PTAA. In both semiconductors, the mobility has been found to be constant with respect to the gate bias. Despite its simplicity, the Kelvin probe force microscopy method reported here provides robust and accurate surface potential measurements on thin-film devices under operation and thus paves the way towards more extensive studies of particular interest in emerging fields of solid-state electronics.

• OSTI ID: 22594536
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 12 Vol. 119; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ATOMIC FORCE MICROSCOPY
BUILDUP
CARRIER MOBILITY
CHARGE CARRIERS
DETECTION
EFFICIENCY
ELECTRIC POTENTIAL
EQUIPMENT
FEEDBACK
INJECTION
NONLINEAR PROBLEMS
PHASE SHIFT
POLYMERS
SEMICONDUCTOR MATERIALS
SURFACE POTENTIAL
SURFACES
THIN FILMS
THIOPHENE
TRANSISTORS
TRANSPORT THEORY