Monthly Archives: March 2015

Unified drain-current model of complementary p- and n-type OTFTs

Publication date: July 2015 Source:Organic Electronics, Volume 22 Author(s): Fabrizio Torricelli , Matteo Ghittorelli , Matteo Rapisarda , Antonio Valletta , Luigi Mariucci , Stephanie Jacob , Romain Coppard , Eugenio Cantatore , Zsolt Miklós Kovács-Vajna , Luigi Colalongo A unified drain current model of complementary (p- and n-type) organic thin film transistors (OTFTs) is presented. The model is physically based and takes into account the detailed properties of the organic semiconductor through the density of states (DOS). The drain current depends on the geometrical and physical parameters of the transistor, on the applied gate, drain and source voltages, and on the surface potential at the source and drain contacts. An analytical expression of the surface potential is derived. The proposed model is validated with the numerical calculations and the measurements of both p- and n-type OTFTs fabricated in a printed complementary technology. The provided analyses show that the model is continuous, accurate, and includes the main physical effects taking place in complementary organic transistors. Thanks to its analytical and symmetric formulation, it is suitable for the design of organic integrated circuits. Moreover, the unified physical picture provided by the model enables the extraction of the OTFTs physical parameters, thus it is a very powerful tool for the technology characterization. Graphical abstract

(3Z,3’Z)-3,3′-(Hydrazine-1,2-diylidene)bis(indolin-2-one) as a new electron-acceptor building block for donor-acceptor [small pi]-conjugated polymers for organic thin film transistors

J. Mater. Chem. C, 2015, Accepted ManuscriptDOI: 10.1039/C5TC00447K, PaperWei Hong, Chang Guo, Bin Sun, Yuning Li(3Z,3'Z)-3,3'-(Hydrazine-1,2-diylidene)bis(indolin-2-one) (HBI) was found to be a promising new electron-acceptor building block for constructing donor-acceptor (D-A) [small pi]-conjugated polymers for organic thin film transistors. Ambipolar charge transport performance with hole and...The content of this RSS Feed (c) The Royal Society of Chemistry

Back Channel Anodization Amorphous Indium Gallium Zinc Oxide Thin-Film Transistors Process

A back channel anodization (BCA) process for fabrication of amorphous indium gallium zinc oxide thin-flim transistors (a-IGZO TFTs) is proposed and demonstrated for the first time. In the BCA process, a localized anodic oxidization (anodization) is successfully implemented to convert the metal layer on back channel into insulator for channel passivation, with the metal layer on source/drain regions intact. As a result, source/drain electrodes and the back channel passivation layer are formed simultaneously in the process step of the BCA. The characterization results show that the fabricated a-IGZO TFTs utilizing BCA process have comparable electrical performances and superior gate-bias stress stability to the conventional a-IGZO TFTs with source/drain electrodes patterned by liftoff.

Effect of Surrounded-Channel Structure on Electrical Characteristics of $c$ -Axis Aligned Crystalline In–Ga–Zn–O Field-Effect Transistor

In this letter, we report the electrical characteristics of a crystalline oxide semiconductor, especially $boldsymbol {c}$ -axis aligned crystalline In–Ga–Zn–O (CAAC-IGZO) field-effect transistors (FETs) having a surrounded-channel structure with 51-nm channel lengths, 11-nm equivalent oxide thicknesses of the gate insulating films, and various channel widths. The results show that the influence of the gate electrode on the sides of the channel increases as the channel width is reduced, which leads to excellent OFF-state and ON-state current characteristics of the FET with a 51-nm channel length and a 50-nm channel width. By exploiting these characteristics, low-power large-scale integration (LSI) applications become possible that would not be possible with conventional Si-LSI techniques.

A robust ionic liquid-polymer gate insulator for high-performance flexible thin film transistors

J. Mater. Chem. C, 2015, Advance ArticleDOI: 10.1039/C5TC00067J, CommunicationJieun Ko, Su Jeong Lee, Kyongjun Kim, EungKyu Lee, Keon-Hee Lim, Jae-Min Myoung, Jeeyoung Yoo, Youn Sang KimAn ionic liquid-polymer (IL-PVP) dielectric layer with robust mechanical strength and flexibility was fabricated by a chemical interaction between the ionic liquid and polymer. This dielectric layer allowed operation of flexible thin film transistors with high performance.To cite this article before page numbers are assigned, use the DOI form of citation above.The content of this RSS Feed (c) The Royal Society of Chemistry

Preparation and characterization of molybdenum-doped indium-zinc-oxide thin film transistors

In this study, amorphous molybdenum-doped indium zinc oxide (a-IZMO) thin film transistors (TFTs) were prepared by radio frequency magnetron sputtering at room temperature. It was found that molybdenum doping increased the optical bandgap of the a-IZMO films, improved the current on/off ratio and subthreshold swing value of the a-IZMO-TFTs. X-ray photoelectron spectroscopy analysis shows that Mo-doping can efficiently suppress the formation of oxygen vacancies. When an appropriate Mo content at molar ratio of 2.9% was doped into the IZO active layer, the TFTs with field effect mobility of 2.62 cm 2 V −1 s −1 , and current on/off ratio of larger than 10 6 was obtained.

Rapid wide-field heterodyne interferometry with custom 2D CMOS camera

A wide-field pseudo-heterodyne interference contrast microscope is described, which employs a complementary metal–oxide semiconductor (CMOS) phase-sensitive camera. The use of multiple wells in the camera enables extremely rapid measurement of a full phase field at high resolution and the modulation frequency is not limited by the camera frame rate. The high data acquisition frequency allows the effects of microphonics to be frozen to mitigate the effect of low-frequency disturbance.

Enhanced locking range technique for divide-by-3 differential injection-locked frequency divider

A new circuit technique is proposed to enhance the locking range of divide-by-3 injection-locked frequency dividers (ILFDs) implemented using a standard 0.18 μm CMOS process. The ILFD uses a transformer feedback to increase the second harmonic and enhances the conversion efficiency of injection metal–oxide semiconductor field-effect transistor mixers. The ILFD core consumes 10.8 mW power at the supply voltage of 0.9 V and with a circuit core current of 12 mA. At the incident power of 0 dBm, the measured locking range is 4.2 GHz (37.17%), from the incident frequency 9.2–13.4 GHz.

Wurtzite-derived ternary I–III–O 2 semiconductors

Ternary zincblende-derived I–III–VI 2 chalcogenide and II–IV–V 2 pnictide semiconductors have been widely studied and some have been put to practical use. In contrast to the extensive research on these semiconductors, previous studies into ternary I–III–O 2 oxide semiconductors with a wurtzite-derived β -NaFeO 2 structure are limited. Wurtzite-derived β -LiGaO 2 and β -AgGaO 2 form alloys with ZnO and the band gap of ZnO can be controlled to include the visible and ultraviolet regions. β -CuGaO 2 , which has a direct band gap of 1.47 eV, has been proposed for use as a light absorber in thin film solar cells. These ternary oxides may thus allow new applications for oxide semiconductors. However, information about wurtzite-derived ternary I–III–O 2 semiconductors is still limited. In this paper we review previous studies on β -LiGaO 2 , β -AgGaO 2 an...

Nano-needle structured, ambipolar high electrical conductivity SnOx (x ≤ 1) thin films for infrared optoelectronics

SnO has become an important earth-abundant transparent conductive oxide (TCO) with applications not only in photovoltaics but also in electrodes for energy storage. For optoelectronic applications, low fabrication temperature, high electrical conductivity, and low optical losses are highly desirable. This study presents self-assembled, ambipolar (i.e., n and p-type) nano-needle structured SnOx (x ≤ 1) thin films with high electrical conductivity, low infrared (IR) optical losses, and potentials for effective light trapping. These nano-needle structured SnOx films are fabricated through non-reactive co-sputtering of Sn and SnO2 followed by crystallization annealing at low temperatures crystallization of SnOx thin films occurred rapidly above 210 °C, resulting in SnO nano-needles with average dimensions of 1 μm long, 0.1 μm wide, and 0.15 μm thick that are interspersed with Sn nanocrystals. The optical scattering from these nanostructures can be utilized for light trapping in thin film absorbers. We also found that laser pre-patterning enabled control over nano-needle crystal size and growth directions. The electrical conductivity of 1500–2000 S/cm is comparable to state-of-the-art SnO2:F TCOs while the fabrication temperature is reduced by ∼200 °C, enabling a broader range of applications, such as optoelectronics on flexible substrates. Hall effect measurements show an intriguing ambipolar behavior depending on the annealing ambient. Especially, a strong p-type conductivity with a hole concentration of p ∼ 5 × 1021 cm−3 and mobility μp ∼ 2 cm2 V−1 s−1 is obtained in a weak oxidizing ambient. Such a high p-type conductivity is particularly rare in TCOs, and it offers potential applications in bipolar oxide semiconductor devices. Optical measurements showed a low absorption loss of x, suggesting that these nano-needle structured SnOx TCOs can be engineered to enhance low-loss optical scattering/light trapping in thin film thermophotovoltaic cells and IR photodetectors.