Organic single-crystal field-effect transistors

Abstract

We present an overview of recent studies of the charge transport in the field effect transistors on the surface of single crystals of organic low-molecular-weight materials. We first discuss in detail the technological progress that has made these investigations possible. Particular attention is devoted to the growth and characterization of single crystals of organic materials and to different techniques that have been developed for device fabrication. We then concentrate on the measurements of the electrical characteristics. In most cases, these characteristics are highly reproducible and demonstrate the quality of the single crystal transistors. Particularly noticeable are the small sub-threshold slope, the non-monotonic temperature dependence of the mobility, and its weak dependence on the gate voltage. In the best rubrene transistors, room-temperature values of m as high as 15 cm 2 /Vs have been observed. This represents an order-of-magnitude increase with respect to the highest mobility previously reported for organic thin film transistors. In addition, the highest-quality single-crystal devices exhibit a significant anisotropy of the conduction properties with respect to the crystallographic direction. These observations indicate that the field effect transistors fabricated on single crystals are suitable for the study of the intrinsic electronic properties of organic molecular semiconductors. We conclude by indicating some directions in which near-future work should focus to progress further in this rapidly evolving area of research.

Threshold Voltage and Space Charge in Organic Transistors

“…The shift is due to space-charge transferred from the contacts, and can be modeled quantitatively without free fitting parameters, using Poisson's equation, and by assuming that the density of states in rubrene is that of a conventional inorganic semiconductor. Our results demonstrate the consistency, at the quantitative level, of a variety of recent experiments on rubrene crystals, and show how the use of FET measurements can enable the determination of microscopic parameters (e.g., the effective mass of charge carriers).Organic single-crystal field-effect transistors (FETs) are opening new possibilities for the detailed investigation of the intrinsic electronic properties of organic semiconductors and of their interfaces [1,2]. Transistors where a single-crystal was suspended on top of a gate electrode, have led to the observation of intrinsic transport properties, such as mobility anisotropy [3] and metallic-like temperature dependence [4].…”

“…Organic single-crystal field-effect transistors (FETs) are opening new possibilities for the detailed investigation of the intrinsic electronic properties of organic semiconductors and of their interfaces [1,2]. Transistors where a single-crystal was suspended on top of a gate electrode, have led to the observation of intrinsic transport properties, such as mobility anisotropy [3] and metallic-like temperature dependence [4].…”

Photoinduced Charge Transfer across the Interface between Organic Molecular Crystals and Polymers

“…In the dark, the "as-prepared" single-crystal rubrene OFETs, characterized with a high roomtemperature mobility of field-induced positive polarons (µ = 4 -20 cm 2 /Vs) [5,8], exhibit a very small field-effect threshold ( Fig. 1) [15].…”

Growth and characterization of organic layers deposited on porous-patterned Si surface

“…In such case a low temperature and even room temperature deposition of good quality layer is possible in spite of the factor of the big lattice mismatch and difference in the thermal expansion coefficient [15]. The scale of the roughness prepared by ECE is essentially less than TSK feature size.…”