Ultra-high gain diffusion-driven organic transistor

Emerging large-area technologies based on organic transistors are enabling the fabrication of low-cost flexible circuits, smart sensors and biomedical devices. High-gain transistors are essential for the development of large-scale circuit integration, high-sensitivity sensors and signal amplification in sensing systems. Unfortunately, organic field-effect transistors show limited gain, usually of the order of tens, because of the large contact resistance and channel-length modulation. Here we show a new organic field-effect transistor architecture with a gain larger than 700. This is the highest gain ever reported for organic field-effect transistors. In the proposed organic field-effect transistor, the charge injection and extraction at the metal–semiconductor contacts are driven by the charge diffusion. The ideal conditions of ohmic contacts with negligible contact resistance and flat current saturation are demonstrated. The approach is general and can be extended to any thin-film technology opening unprecedented opportunities for the development of high-performance flexible electronics

Why PEDOT:PSS Should Not Be Used for Raman Sensing of Redox States (and How It Could Be)

Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) has been recently proposed for Raman sensing of redox-active species in solution. Here, we investigated the rationale of this approach through systematic experiments, in which the Raman spectrum of PEDOT:PSS was analyzed in the presence of either nonoxidizing or oxidizing electrolytes. The results demonstrated that Raman spectra precisely reflect the conformation of PEDOT units and their interactions with PSS. Two different responses were observed. In the case of oxidizing electrolytes, the effect of charge transfer is accurately transduced in Raman spectrum changes. On the other hand, reduction induces a progressive separation between the PEDOT and PSS chains, which decreases their mutual interaction. This stimulus determines characteristic variations in the intensity, shape, and position of the Raman spectra. However, we demonstrated that the same effects can be obtained either by increasing the concentration of nonoxidizing electrolytes or by deprotonating PSS chains. This poses severe limitations to the use of PEDOT:PSS for this type of Raman sensing. This study allows us to revise most of the Raman results reported in the literature with a clear model, setting a new basis for investigating the dynamics of mixed electronic/ionic charge transfer in conductive polymers

Correction: Printed, cost-effective and stable poly(3-hexylthiophene) electrolyte-gated field-effect transistors

Correction for 'Printed, cost-effective and stable poly(3-hexylthiophene) electrolyte-gated field-effect transistors' by Davide Blasi et al., J. Mater. Chem. C, 2020, DOI: 10.1039/d0tc03342a

Method and Device for Identifying Fingerprints

1filing date: 04.04.2001, Issued: 12.11.2002nonenoneZ. KOVACS VAJNAKOVACS VAJNA, Zsolt Miklo

Physical Modeling of Amorphous InGaZnO Thin-Film Transistors: The Role of Degenerate Conduction

none3noIn amorphous indium-gallium-zinc oxide thin-film transistors (a-IGZO TFTs), the electron mobility easily exceeds 10²/Vs and degenerate band conduction is observed. On the other hand, the field-effect mobility is gate voltage-dependent. Here, we propose a physical model for a-IGZO TFTs accounting for both the non-degenerate and degenerate conductions of trapped and free charges. The comparison between the model and the measurements shows that: 1) the shape of the drain current is almost completely defined by the localized density of states and 2) a transition from non-degenerate-to-degenerate conductions is always observed. This explains the measured gate voltage-dependent field-effect mobility and provides a simple and unified physical picture of the charge transport in a-IGZO TFTs.Ghittorelli, Matteo; Torricelli, F.; Kovacs-vajna, Z. M.Ghittorelli, M.; Torricelli, F.; Kovacs-vajna, Z. M

Analytical Physical-Based Drain-Current Model of Amorphous InGaZnO TFTs Accounting for Both Non-Degenerate and Degenerate Conduction

In this letter, we propose a physical-based analytical drain current model for amorphous indium–gallium–zinc oxide thin-film transistors (a-IGZO TFTs). As a key feature, the model accounts for both the non-degenerate and the degenerate conduction regimes, including the contributions of trapped and free charges. These two conduction regimes as well as the trapped and free charges are essential to consistently describe a-IGZO TFTs. The model is compared with both exact numerical calculations and measurements. It is continuous, symmetric, simple, and accurate. The model enables to gain physical insight on the material and device properties, and it is a valuable tool for fast process optimization and circuit design

Single-Poly-EEPROM Cell in Standard CMOS Process for Medium-Density Applications

A new single-poly-EEPROM cell compatible with standard CMOS processes is proposed. A pMOS tunneling device is used for programming and erasing, and an nMOS transistor is used for reading and selecting the memory cell when it is in an array. The pMOS device is a minimum-sized digital transistor with the gate oxide of the input/output transistors. This improves the coupling capacitance, minimizes the area consumption, and guarantees the retention. The memory cell is programmed by band-to-band hot electrons and erased by Fowler-Nordheim tunneling. Thanks to the proposed writing scheme, the memory cell requires only a single triple-well. This further reduces the area consumption, and ensures, at the same time, fast and reliable memory operations. The measurements on programming, erasing, reading, cycling endurance, and data retention are provided using a 0.18-μm standard CMOS process. The memory cell area is 5.91 μm² in an array, and it can be programmed in tP = 1 ms, erased in t = 10 ms, and cycled for >10k times with a voltage window greater than 2 V