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In this article, we compare the direct current (dc) and high-frequency performance of two different organic diode structures, a vertical diode and an organic field effect transistor (OTFT) with shorted drain-gate contact, regarding their application in a rectifying circuit. For this purpose, we fabricated both diode structures using the organic semiconductor pentacene. dc measurements were performed showing a space-charge-limited current mobility of more than 0.1 cm2/V s for the vertical diode and a field effect mobility of 0.8 cm2/V s for the OTFT with shorted source-drain. High-frequency measurements of those diode structures in a rectifier configuration show that both types of diodes are able to follow the base-carrier frequency of 13.56 MHz which is essential for viable radio-frequency-identification (rf-ID) tags. Based on those results we evaluate the performance limits and advantages of each diode configuration regarding their application in an organic rf-ID tag. [ABSTRACT FROM AUTHOR]

The authors study the use of pentacene thin-film transistors as phototransistors. The shift in turn-on voltage (Von), responsible for the high photosensitivity of these devices, is shown to be strongly dependent on illumination time and applied gate voltage. The time dependence of this process is similar to the shift in Von during bias stress experiments in the dark, and illumination can simply be accounted for as an acceleration factor for bias stress instability. By comparing the characteristics of devices with different gate dielectrics, trapping of electrons by OH groups at the gate dielectric interface is indicated as a main origin for these shifts. [ABSTRACT FROM AUTHOR]

An organic vapor phase deposition (OVPD) tool has been developed and optimized for the deposition of pentacene thin films. Pentacene is grown with a good thickness uniformity, a good material consumption efficiency, and deposition rates up to 9.5 Å/s. Top-contact transistors based on OVPD-grown pentacene show high mobilities (up to 1.35 cm2/V s) and excellent characteristics, even at high deposition rates. Elementary circuit blocks have also been produced using an OVPD-deposited pentacene film. A five-stage ring oscillator features a stage delay of 2.7 μs at a supply voltage of 22 V. [ABSTRACT FROM AUTHOR]

We propose a way of patterning organic small molecule thin films without requiring a hardmask and therefore more compatible with printing technologies. Active and passive areas for transistors are predefined by different surface chemistries. The subsequent growth takes place under conditions that cause the formation of a high mobility two-dimensional film in the active area and a disconnected three-dimensional film or no film in the passive area. This concept is founded on the basic theory of nucleation of organic small molecules on inert substrates and applied to the growth of patterned pentacene layers. [ABSTRACT FROM AUTHOR]

The properties of the dielectric strongly influence the performance of organic thin-film transistors. In this letter, we show experimental results that quantify the influence of the roughness of the dielectric on the mobility of pentacene transistors and discuss the cause of it. We consider the movement of charge carriers out of the “roughness valleys” or across those valleys at the dielectric–semiconductor interface as the limiting step for the roughness-dependent mobility in the transistor channel. [ABSTRACT FROM AUTHOR]

Abstract: In this work, a completely scalable integration process is presented for organic–inorganic complementary logic, based on low-temperature spin-coated n-type metal oxide TFTs and thermally evaporated p-type pentacene TFTs. Both transistor types are photolithographically processed side-by-side, without the use of any shadow mask. High performance n-type metal oxide TFTs, post-annealed at a maximum temperature of only 250°C, exhibit saturation mobilities exceeding 2cm2/(Vs), subthreshold swing as low as 0.19V/decade and I on/I off ratios beyond 107 after integration with p-type pentacene TFTs. Using this hybrid complementary technology, 5-stage and 19-stage ring-oscillators are demonstrated, operating at supply voltages as low as 2.5V. The ring-oscillators oscillate at a frequency of more than 110kHz, corresponding to stage delays as low as 0.74μs, at a supply bias of 20V. [Copyright &y& Elsevier]