Hybrid La2O3-cPVP Dielectric for Organic Thin Film Transistor Applications

In this work, we have studied the electrical performance of cross-linked polyvinyl phenol (cPVP) modified lanthanum oxide (La2O3) bilayer dielectric film in pentacene thin film transistors (TFT). A simple spin-coating and room temperature operated cross-linking reaction of the hydroxyl moieties of PVP and the nitrogen groups of PMF were carried out to form the cross-linked PVP. The deposition of a thin 30 nm cPVP layer over the La2O3 layer provided a low leakage current (<10−7A/cm2), causing a reduction in the interface trap density. Besides, the modified surface properties of the La2O3 layer were favorable for the growth of pentacene organic semiconductors. As a result, the current on-off ratio and the sub-threshold slope was improved from 104 and 1.0 V/decade to 105 and 0.67 V/decade. The La2O3∕cPVP pentacene TFT operated at −10 V also exhibited improvement in the field-effect mobility to 0.71 cm2/Vs from 0.48 cm2/Vs for the single-layer La2O3 (130 nm) device. Thus, our work demonstrates that the rare earth oxide La2O3 with cPVP is an excellent dielectric system in the context of emerging transistors with hybrid polymer gate dielectrics.

Electrical and Optical Characteristics of SSI-LED Made from Capacitor Containing Tri-Layer WOx Embedded Zr-Doped HfOx Gate Dielectric

Solid-state incandescent light emitting devices made from MOS capacitors with the WOx embedded Zr-doped HfOx gate dielectric were characterized for electrical and optical characteristics. Devices made from capacitors containing Zr-doped HfOx and WOx, gate dielectrics were also fabricated for comparison. The device with the WOx embedded gate dielectric layer had electrical and light emitting characteristics between that with WOx gate dielectric layer and that with the Zr-doped HfOx but no WOx embedded gate dielectric layer. The difference can be explained by the nano-resistor formation process and the content of the high emissivity W in the nano-resistor. The device made from the WOx embedded Zr-doped HfOx gate dielectric MOS capacitor is applicable to areas where uniform emission of warm white light is required.

Mnemonic-Opto-Synaptic Transistor for In-Sensor Vision System

A mnemonic-opto-synaptic transistor (MOST) that has triple functions is demonstrated for an in-sensor vision system. It memorizes a photoresponsivity that corresponds to a synaptic weight as a memory cell, senses light as a photodetector, and performs weight updates as a synapse for machine vision with an artificial neural network (ANN). Herein the memory function added to a previous photodetecting device combined with a photodetector and a synapse provides a technical breakthrough for realizing in-sensor processing that is able to perform image sensing and signal processing in a sensor. A charge trap layer (CTL) was intercalated to gate dielectrics of a vertical pillar-shaped transistor for the memory function. Weight memorized in the CTL makes photoresponsivity tunable for real-time multiplication of the image with a memorized photoresponsivity matrix. Therefore, these multi-faceted features can allow in-sensor processing without external memory for the in-sensor vision system. In particular, the in-sensor vision system can enhance speed and energy efficiency compared to a conventional vision system due to the simultaneous preprocessing of massive data at sensor nodes prior to ANN nodes. Recognition of a simple pattern was demonstrated with full sets of the fabricated MOSTs. Furthermore, recognition of complex hand-written digits in the MNIST database was also demonstrated with software simulations.

DNA hydrogel to improve solution-gate graphene field effect transistor in all-solid-state

The solution-gate graphene field effect transistor (Sg-GFET), as a popular sensing platform, its applications are still hindered by the deficiency in all-solid-state, due to the dependence on liquid-state gate-dielectric. Inspired by DNA hydrogel which can provide microporous architecture to accommodate the fluidic analyte, moreover, its combination with graphene is believed to foster electron transport in the field of electrochemistry. We are interested to take advantage of DNA hydrogel's solid-state and capability for holding solution, and investigate whether it can replace the traditional solution. So pure DNA hydrogel, their complexes with GO (GO/DNA hydrogel) and RGO (RGO/DNA hydrogel) are studied herein. Their micro-porous 3D morphologies are demonstrated, their influences on the electrical characteristics of GFETs are carefully examined and proved to be able to maintain the typical bipolarity of Sg-GFET, firstly. Then, pure DNA hydrogel and GO/DNA hydrogel are selected as the optimized gate-dielectrics, because of their renewability after dehydration. Furthermore, by using aptamer-based heavy metal ions (Pb2+ and Hg2+) detections as proof-of-concept, the strategies for building the sensing platform based on the optimized hydrogel dielectric-gated GFETs are studied. It is found, for the purpose of substituting fluidic dielectric in traditional Sg-GFET, the scheme of directly mounting aptamer on graphene channel and coating pure DNA hydrogel on it is demonstrated to be better than the strategies of using GO/DNA hydrogel and hybriding aptamer probes in hydrogel scaffold. It is explained according to surface charge sensing mechanism. At last, the performances of the sensing platform based on the proposed DNA hydrogel gated GFETs are testified by the detections and selectivity examinations for Pb2+ and Hg2+. Conclusively, pure DNA hydrogel is expected to be a promising candidate in the future all-solid-state Sg-GFET.

Interface scattering dominated carrier transport in hysteresis-free amorphous InGaZnO thin film transistors with high-k HfAlO gate dielectrics by atom layer deposition

In this work, we systematically investigated the carrier transport of hysteresis-free amorphous InGaZnO (a-IGZO) thin film transistors (TFTs) incorporating high-k (HfO2)x(Al2O3)y gate dielectrics with different composition and permittivity by atomic layer deposition (ALD). A dielectric surface morphology dominated interface scattering carrier transport mechanism is demonstrated, and the effect of the dielectric polarization and the interface states on the carrier mobility is discovered in TFT devices gated by high quality dielectrics with negligible charge trap effect. Accordingly, an a-IGZO TFT gated by (HfO2)0.5(Al2O3)0.5 dielectric with the smoothest surface exhibits the best performance in terms of a preferable field-effect mobility of 18.35 cm2 V-1 s-1, a small subthreshold swing of 0.105 V decade-1, a high on/off current ratio of 4.6× 106, and excellent stability under positive bias stress.

Self-powered bifunctional sensor based on tribotronic planar graphene transistors

With the development of material science, micro-nano-fabrication and microelectronics, the higher level requirements are posed on the electronic skins (E-skin). The lower energy consumption and multiple functions are the imperative requirements to spurred scientists and mechanists to make joint efforts to meet. To achieve lower energy consumption, a promising energy-harvesting style of triboelectric nanogenerators (TENG) is incorporated into the field effect transistors (FETs) to play the important role for sensor. For bifunctional sensor, to harness the difficult for reflecting the magnitude of frequency, we resorted to synaptic transistors to achieve more intelligentization. Furthermore, with regards to the configuration of FET, we continued previous work: using the electrolyte gate dielectrics of FET—ion gel as the electrification layer to achieve high efficient, compact and extensively adoption for mechanosensation. The working principle of the GFET was based on the coupling effects of the FET and the TENG. This newly emerged self-powered sensor would offer a new platform for lower power consumption sensor for human–machine interface and intelligent robot.