Monthly Archives: November 2014

Surface treatment on amorphous InGaZnO4 thin film for single-stranded DNA biosensing

Publication date: 1 January 2015 Source:Applied Surface Science, Volume 324 Author(s): Dali Sun , Hiroaki Matsui , Chun-Nan Wu , Hitoshi Tabata Amorphous InGaZnO4 (aIGZO) has been widely used as a transparent semiconductor. However, no research has been found yet applying aIGZO to biosensing. This paper examined the single strand DNA (ssDNA) immobilization on aIGZO by absorption with a comparison to ITO, which is the first step for many biosensing schemas. The DNA quantification by florescence intensity shows that the absorption capacity of aIGZO film to ssDNA is 6.7 times greater than that of ITO. XPS and contact angle analysis proved the high DNA absorption affinity on aIGZO film is related to its high effectiveness to OH− attachment. A feasible method to immobilized ssDNA on aIGZO thin film is evaluated in this paper, and consequently, enables a possible approach to apply aIGZO in biosensing. Graphical abstract

Flexible Organic Electronics in Biology: Materials and Devices

At the convergence of organic electronics and biology, organic bioelectronics attracts great scientific interest. The potential applications of organic semiconductors to reversibly transmit biological signals or stimulate biological tissues inspires many research groups to explore the use of organic electronics in biological systems. Considering the surfaces of movable living tissues being arbitrarily curved at physiological environments, the flexibility of organic bioelectronic devices is of paramount importance in enabling stable and reliable performances by improving the contact and interaction of the devices with biological systems. Significant advances in flexible organic bio­electronics have been achieved in the areas of flexible organic thin film transistors (OTFTs), polymer electrodes, smart textiles, organic electrochemical ion pumps (OEIPs), ion bipolar junction transistors (IBJTs) and chemiresistors. This review will firstly discuss the materials used in flexible organic bioelectronics, which is followed by an overview on various types of flexible organic bioelectronic devices. The versatility of flexible organic bioelectronics promises a bright future for this emerging area. Organic bioelectronics attracts much attention due to their unique electronic properties, biocompatibility, mechanical flexibility, easy fabrication, and low cost. Flexible devices are potentially useful in many biological applications because the surfaces of living tissues are always arbitrarily curved. This review focuses mainly on the operation and application of flexible bioelectronic devices reported in recent years.

Roll-to-roll compatible organic thin film transistor manufacturing technique by printing, lamination, and laser ablation

Publication date: 28 November 2014 Source:Thin Solid Films, Volume 571, Part 1 Author(s): Tomi Hassinen , Teemu Ruotsalainen , Petri Laakso , Raimo Penttilä , Henrik G.O. Sandberg We present roll-to-roll printing compatible techniques for manufacturing organic thin film transistors using two separately processed foils that are laminated together. The introduction of heat-assisted lamination opens up possibilities for material and processing combinations. The lamination of two separately processed substrates together will allow usage of pre-patterned electrodes on both substrates and materials with non-compatible solvents. Also, the surface microstructure is formed differently when laminating dry films together compared to film formation from liquid phase. Demonstrator transistors, inverters and ring oscillators were produced using lamination techniques. Finally, a roll-to-roll compatible lamination concept is proposed where also the source and drain electrodes are patterned by laser ablation. The demonstrator transistors have shown very good lifetime in air, which is contributed partly to the good material combination and partly to the enhanced interface formation in heat-assisted lamination process.

Low-resistivity C54-TiSi 2 as a sidewall-confinement nanoscale electrode for three-dimensional vertical resistive memory

A three-dimensional (3D) double-layer HfO2-based vertical-resistive random access memory (VRRAM) with low-resistivity C54-TiSi2 as horizontal electrodes is demonstrated using complementary metal-oxide semiconductor processing. The electrical measurements show bipolar resistive switching by using C54-TiSi2 as electrodes for resistive switching (RS) applications. The statistical analysis exhibits cycle-to-cycle and cell-to-cell stable non-volatile properties with robust endurance (100 cycles) and long term data retention (104 s), suggesting that the ultrathin sidewall of C54-TiSi2 nanoscale electrodes serve to confine and stabilize the random nature of the conducting nanofilaments. The superior RS characteristics demonstrated here highlight the applicability of C54-TiSi2 sidewall-confinement nanoscale electrodes to VRRAM.

Temperature dependence of the electrical characteristics of low-temperature processed zinc oxide thin film transistors

Publication date: 31 December 2014 Source:Thin Solid Films, Volume 573 Author(s): M. Estrada , G. Gutierrez-Heredia , A. Cerdeira , J. Alvarado , I. Garduño , J. Tinoco , I. Mejia , M. Quevedo-Lopez The impact on the electrical behavior of thin film transistors, TFTs, based on zinc oxide, ZnO-based TFTs, with temperature is analyzed. ZnO is deposited using pulsed laser deposition techniques and the temperature used during the entire fabrication process is kept below 100°C. Up to 330K, the transfer curves practically remain constant or slightly shifted toward more positive voltages. For temperatures up to 330K, they show the combined effect of the threshold voltage shifting toward more negative voltages and the increase of series resistance. The drain current shows an Arrhenius-type dependence with temperature in subthreshold regime with activation energy of around 0.53eV. In above threshold regime, for temperatures above 330K, the activation energy is around 0.15eV.

Influence of curvature on the device physics of thin film transistors on flexible substrates

Thin film transistors (TFTs) on elastomers promise flexible electronics with stretching and bending. Recently, there have been several experimental studies reporting the behavior of TFTs under bending and buckling. In the presence of stress, the insulator capacitance is influenced due to two reasons. The first is the variation in insulator thickness depending on the Poisson ratio and strain. The second is the geometric influence of the curvature of the insulator-semiconductor interface during bending or buckling. This paper models the role of curvature on TFT performance and brings to light an elegant result wherein the TFT characteristics is dependent on the area under the capacitance-distance curve. The paper compares models with simulations and explains several experimental findings reported in literature.