Active-matrix Thin-film Transistor Research Articles

Review of Integrated Gate Driver Circuits in Active Matrix Thin-Film Transistor Display Panels.

Many advanced technologies have been employed in high-performance active matrix displays, including liquid crystal displays, organic light-emitting diode displays, and micro-light-emitting diode displays. On the other side, there exists a strong demand for cost reduction, and it is one of the low-cost schemes for integrating the driver circuit in a panel based on thin-film transistor technologies. This paper reviews the overall concept, operation principles, and various circuit approaches in shift registers for scanning pulse generation. In addition, it deals with the implementation of additional functionalities in gate drivers to support pixel compensation, multi-line driving, in-cell capacitive touch screen, pixel sensing, and adaptive scanning region control.

Active-matrix digital microfluidics design for field programmable high-throughput digitalized liquid handling

Digital liquid sample handling is an enabling tool for cutting-edge life-sciences research. We present here an active-matrix thin-film transistor (TFT) based digital microfluidics system, referred to as Field Programmable Droplet Array (FPDA). The system contains 256×256 pixels in an active area of 10.65cm2, which can manipulate thousands of addressable liquid droplets simultaneously. By leveraging a novel TFT device and circuits design solution, we manage to programmatically manipulate droplets at single-pixel level. The minimum achievable droplet volume is around 0.5 nL, which is two orders of magnitude smaller than the smallest droplet ever reported on active-matrix digital microfluidics. The movement of droplets can be either pre-programmed or controlled in real-time. The FPDA system shows great potential of the ubiquitous thin-film electronics technology in digital liquid handling. These efforts will make it possible to create a true programmable lab-on-a-chip device to enable great advances in life science research.

Optoelectronics Inspection of Amorphous In–Ga–Zn–O-based Active-matrix Thin-film Transistor Array for Foldable Substrate Applications

Optoelectronics Inspection of Amorphous In–Ga–Zn–O-based Active-matrix Thin-film Transistor Array for Foldable Substrate Applications

Direct integration of piezoactuator array with active-matrix oxide thin-film transistors using a low-temperature solution process

The integration of a thin-film piezoelectric actuator with standard CMOS (Complementary Metal-Oxide-Semiconductor) technology has attracted many practical interests for totally integrated smart devices such as electronics, microfluidics, sensors and actuators. However, the major obstacle of the integration lies in high annealing temperature required for crystallization of piezoelectric thin-films (600–750 °C), which leads to degradation of back circuitry. This paper reports, for the first time, a successful direct integration of lead-zirconium-titanate (PZT) thin-film, the piezoelectric with the greatest commercial applicability, with an active-matrix oxide thin-film transistor (TFT) using a low-temperature (450 °C) solution-processable PZT thin-film. The actuation of the PZT actuator array, electrically driven by the active-matrix TFT, was confirmed. The proposed device can be used in various applications such as micropumps/valves, microfluidic control, energy harvesting, sensors and the like.

Numerical analysis of delamination and cracking phenomena in multi-layered flexible electronics

The first part of this paper deals with the analysis of layer buckling and delamination of thin film multi-layer structures that are used in flexible display applications. To this end, 250 nm thick indium tin oxide (ITO) layers have been deposited on a 200 μ m thick high temperature aromatic polyester substrate (Arylite ™ ) with a 3 μ m silica–acrylate hybrid hard coat (HC). Typical buckle morphologies are determined from two-point bending experiments, in which buckle geometries are measured after straightening of the sample. Finite element simulations have been performed to estimate the corresponding interface properties and compressive strains in the layers, and to illustrate the effect of sample straightening on the buckle geometry. The second part considers the fracture sensitivity analysis of an active matrix Thin Film Transistor (TFT) display containing 512 × 256 pixels, with a typical pixel dimension of 160 × 160 μ m . Due to the large scale differences between the display and the TFT patterning a multi-scale modelling framework has been developed, which allows to include realistic material stacks and a detailed pixel geometry. The resulting patterning effect shows an anisotropic behaviour at both the pixel level and the global display level due to the multi-scale approach. Using the Area Release Energy (ARE) method an energy-based failure criterion has been utilised to analyse cohesive failure at several (critical) locations in the pixel geometry. Specifically, the sensitivity to tunnelling cracks in the dielectric layers is considered, which have been experimentally observed in comparable TFT samples that are subjected to tension. This local failure analysis allows for the identification of critical regions within the pixel geometry, which strongly depend on the location within a pixel.

Active-Matrix Microelectrode Arrays Integrated With Vertically Aligned Carbon Nanofibers

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In this letter, we have successfully integrated vertically aligned carbon nanofibers (VACNFs) onto active matrix thin-film transistor (TFT) and demonstrate a new microelectrode array (MEA) platform. The materials and processes of the bottom gate inverted staggered TFT structure were designed to be compatible with the requisite high-temperature <formula formulatype="inline"><tex Notation="TeX">$(\sim\! \hbox{700}\ ^{\circ}\hbox{C})$</tex></formula> and direct current plasma-enhanced chemical vapor deposition VACNF growth process. The critical device integration issues are elaborated, and initial device characteristics are reported. This device platform provides great potential as an advanced MEA for direct cell sensing, probing, and recording with a high electrode density and active addressability. </para>

Defect Identification in Large Area Electronic Backplanes

We describe a rapid testing system for active matrix thin-film transistor (TFT) backplanes which enables the identification of many common processing defects. The technique spatially maps the charge feedthrough from TFTs in the pixel and is suited for pixels with switched-capacitor architecture.

Printing Methods and Materials for Large-Area Electronic Devices

Two digital printing methods for the fabrication of active matrix thin-film transistor (AM-TFT) backplanes for displays are described. A process using printed resists layers, referred to as digital lithography, was used to fabricate arrays of hydrogenated amorphous silicon TFTs. TFTs were also fabricated using a combination of digital lithography to pattern metals and inkjet printing to pattern and deposit a polymeric semiconducting layer. The relative performance of amorphous silicon and polymer TFTs were evaluated. The utility of digital lithographic processing was demonstrated by the fabrication of prototype reflective displays using electrophoretic media.

Fabrication and Characterization of an Active Matrix Thin Film Transistor Array for Intracellular Probing

AbstractIn order to achieve multiple intracellular stimulation and recording devices with high electrode density and low manufacturing cost, we have fabricated and characterized an active matrix thin film transistor array with integrated vertically aligned carbon nanofibers. This device has the potential for cell probing and screening that provides great potential to execute direct cell sensing/probing and recording with a high electrode density. Each unit pixel in the array is individually addressed by a thin film transistor (TFT) and the vertically aligned carbon nanofibers (VACNF) used to impale the cell are fabricated on the drain electrode of the TFT. The VACNF is grown by direct current plasma enhanced chemical vapor deposition (DCPECVD) using a nickel catalyst. Electroanalysis or impedance differences between the cell probing site and a reference electrode are recorded with a potentiostat or a semiconductor analyzer connected to the output terminals. Additionally, the impedance change with frequency of the intracellular probe can be measured by applying a frame signal input and the signal can be recorded in storage capacitors after the frame scan of the TFTs. Consequently, actively addressed nanofiber arrays enable bidirectional interfacing with tissue matrices in a format that provides intercellular positioning of electrode elements as well as the potential for intracellular residence of probes within individual cells. In our research, we exploit these non-planar electrode systems for efficient coupling with excitable cell matrices as well as for intracellular biochemical manipulation and sensing of and delivery to single cells. In this paper, we will discuss the fabrication sequence of the inverted metal-oxide-semiconductor (MOS) TFT, and will elaborate the materials issues related to integrating the carbon nanofibers with the TFT.

Electro-Optical Bistability in Ferroelectric Liquid Crystal Switching Devices for Use in Displays and Real-Time Holography

Liquid crystalline (LC) materials which exhibit the ferroelectric Sc* phase showed early promise for device applications because of their fast electro-optic response and potential long-term electro-optical bistability. In combination these features should allow fast line at a time addressing and therefore potentially large passive matrix displays. Bistability should also facilitate DC balancing without the need for inverse frame or blanking procedures used in active matrix addressed liquid crystal over silicon devices. Such a feature is very valuable in the application of these materials to telecom devices where signal interruption for DC balancing purposes is very problematic. Long term bistability is also important in realising active tiling based displays. However the realisation of acceptable bistability has not been straightforward. Partly as a result, commercial passive matrix displays have been dominated by super twisted nematic (STN) devices, which have a limited voltage selection ratio that decreases with the number of pixel rows addressed. High quality flat panel LC displays for laptop computers, computer monitors and television has been delivered using active matrix thin film transistor twisted nematic (TFT TN) technology. The first generation of commercially important ferroelectric liquid crystal displays (for near-eye and projection applications) have in fact utilised active matrix liquid crystal over silicon (LCoS) device structures, where the speed of the FLC electro-optic response permits the use of frame sequential methods for generating colour and greyscales in images. Here we discuss the problems encountered in achieving useful bistability within FLC devices, the new applications that would greatly benefit from true FLC bistability and some interesting new results from some siloxane oligomers which suggest new possibilities in achieving true bistability. We hope to highlight the need for a deeper understanding of this problem.