Dynamic Pixel Models for a‐Si TFT‐LCD and Their Implementation in SPICE

A dynamic analysis of an amorphous silicon (a‐Si) thin film transistor liquid crystal display (TFT‐LCD) pixel is presented using new a‐Si TFT and liquid crystal (LC) capacitance models for a Simulation Program with Integrated Circuit Emphasis (SPICE) simulator. This dynamic analysis will be useful when predicting the performance of LCDs. The a‐Si TFT model is developed to accurately estimate a‐Si TFT characteristics of a bias‐dependent gate to source and gate to drain capacitance. Moreover, the LC capacitance model is developed using a simplified diode circuit model. It is possible to accurately predict TFT‐LCD characteristics such as flicker phenomena when implementing the proposed simulation model.     

Stretchable Active Matrix Inorganic Light‐Emitting Diode Display Enabled by Overlay‐Aligned Roll‐Transfer Printing

An active matrix‐type stretchable display is realized by overlay‐aligned transfer of inorganic light‐emitting diode (LED) and single‐crystal Si thin film transistor (TFT) with roll processes. The roll‐based transfer enables integration of heterogeneous thin film devices on a rubber substrate while preserving excellent electrical and optical properties of these devices, comparable to their bulk properties. The electron mobility of the integrated Si‐TFT is over 700 cm² V^?1 s^?1, and this is attributed to the good interface between the Si channel and the thermally grown SiO₂ insulator. The light emission properties of the LED are of wafer quality. The resulting display stably operates under tensile strains up to 40%, over 200 cycles, demonstrating the potential of stretchable displays based on inorganic materials.     

Effects of Interfacial Dielectric Layers on the Electrical Performance of Top‐Gate In‐Ga‐Zn‐Oxide Thin‐Film Transistors

We investigate the effects of interfacial dielectric layers (IDLs) on the electrical properties of top‐gate In‐Ga‐Zn‐oxide (IGZO) thin film transistors (TFTs) fabricated at low temperatures below 200°C, using a target composition of In:Ga:Zn = 2:1:2 (atomic ratio). Using four types of TFT structures combined with such dielectric materials as Si₃N₄ and Al₂O₃, the electrical properties are analyzed. After post‐annealing at 200°C for 1 hour in an O₂ ambient, the sub‐threshold swing is improved in all TFT types, which indicates a reduction of the interfacial trap sites. During negative‐bias stress tests on TFTs with a Si3N4 IDL, the degradation sources are closely related to unstable bond states, such as Si‐based broken bonds and hydrogen‐based bonds. From constant‐current stress tests of Id = 3 µA, an IGZO‐TFT with heat‐treated Si₃N₄ IDL shows a good stability performance, which is attributed to the compensation effect of the original charge‐injection and electron‐trapping behavior.     

Active‐Matrix Field Emission Display with Amorphous Silicon Thin‐Film Transistors and Mo‐Tip Field Emitter Arrays

We present, for the first time, a prototype active‐matrix field emission display (AMFED) in which an amorphous silicon thin‐film transistor (a‐Si TFT) and a molybdenum‐tip field emitter array (Mo‐tip FEA) were monolithically integrated on a glass substrate for a novel active‐matrix cathode (AMC) plate. The fabricated AMFED showed good display images with a low‐voltage scan and data signals irrespective of a high voltage for field emissions. We introduced a light shield layer of metal into our AMC to reduce the photo leakage and back channel currents of the a‐Si TFT. We designed the light shield to act as a focusing grid to focus emitted electron beams from the AMC onto the corresponding anode pixel. The thin film depositions in the a‐Si TFTs were performed at a high temperature of above 360°C to guarantee the vacuum packaging of the AMC and anode plates. We also developed a novel wet etching process for n⁺‐doped a‐Si etching with high etch selectivity to intrinsic a‐Si and used it in the fabrication of an inverted stagger TFT with a very thin active layer. The developed a‐Si TFTs performed well enough to be used as control devices for AMCs. The gate bias of the a‐Si TFTs well controlled the field emission currents of the AMC plates. The AMFED with these AMC plates showed low‐voltage matrix addressing, good stability and reliability of field emission, and good light emissions from the anode plate with phosphors.     

Si‐core/SiGe‐shell channel nanowire FET for sub‐10‐nm logic technology in the THz regime

The p‐type nanowire field‐effect transistor (FET) with a SiGe shell channel on a Si core is optimally designed and characterized using in‐depth technology computer‐aided design (TCAD) with quantum models for sub‐10‐nm advanced logic technology. SiGe is adopted as the material for the ultrathin shell channel owing to its two primary merits of high hole mobility and strong Si compatibility. The SiGe shell can effectively confine the hole because of the large valence‐band offset (VBO) between the Si core and the SiGe channel arranged in the radial direction. The proposed device is optimized in terms of the Ge shell channel thickness, Ge fraction in the SiGe channel, and the channel length (L_g) by examining a set of primary DC and AC parameters. The cutoff frequency (f_T) and maximum oscillation frequency (f_max) of the proposed device were determined to be 440.0 and 753.9 GHz when L_g is 5 nm, respectively, with an intrinsic delay time (τ) of 3.14 ps. The proposed SiGe‐shell channel p‐type nanowire FET has demonstrated a strong potential for low‐power and high‐speed applications in 10‐nm‐and‐beyond complementary metal‐oxide‐semiconductor (CMOS) technology.     

Effect of Mesoscale Crystalline Structure on the Field‐Effect Mobility of Regioregular Poly(3‐hexyl thiophene) in Thin‐Film Transistors

Regioregular poly(3‐hexyl thiophene) (RR P3HT) is drop‐cast to fabricate field‐effect transistor (FET) devices from different solvents with different boiling points and solubilities for RR P3HT, such as methylene chloride, toluene, tetrahydrofuran, and chloroform. A Petri dish is used to cover the solution, and it takes less than 30 min for the solvents to evaporate at room temperature. The mesoscale crystalline morphology of RR P3HT thin films can be manipulated from well‐dispersed nanofibrils to well‐developed spherulites by changing solution processing conditions. The morphological correlation with the charge‐carrier mobility in RR P3HT thin‐film transistor (TFT) devices is investigated. The TFT devices show charge‐carrier mobilities in the range of 10^–4 ～ 10^–2 cm² V^–1 s^–1 depending on the solvent used, although grazing‐incidence X‐ray diffraction (GIXD) reveals that all films develop the same π–π‐stacking orientation, where the <100>‐axis is normal to the polymer films. By combining results from atomic force microscopy (AFM) and GIXD, it is found that the morphological connectivity of crystalline nanofibrils and the <100>‐axis orientation distribution of the π–π‐stacking plane with respect to the film normal play important roles on the charge‐carrier mobility of RR P3HT for TFT applications.     

Soft‐output MMSE V‐BLAST receiver with MMSE channel estimation under correlated Rician fading MIMO channels

For wireless multiple‐input multiple‐output (MIMO) communications systems, both channel estimation error and spatial channel correlation should be considered when designing an effective signal detection system. In this paper, we propose a new soft‐output MMSE based Vertical Bell Laboratories Layered Space‐Time (V‐BLAST) receiver for spatially‐correlated Rician fading MIMO channels. In this novel receiver, not only the channel estimation errors and channel correlation but also the residual interference cancellation errors are taken into consideration in the computation of the MMSE filter and the log‐likelihood ratio (LLR) of each coded bit. More importantly, our proposed receiver generalizes all existing soft‐output MMSE V‐BLAST receivers, in the sense that, previously proposed soft‐output MMSE V‐BLAST receivers can be derived as the reduced forms of our receiver when the above three considered factors are partially or fully simplified. Simulation results show that the proposed soft‐output MMSE V‐BLAST receiver outperforms the existing receivers with a considerable gain in terms of bit‐error‐rate (BER) performance. Copyright © 2011 John Wiley & Sons, Ltd.     

Colorimetric Logic Gates Based on Poly(2‐alkyl‐2‐oxazoline)‐Coated Gold Nanoparticles

A straightforward end‐capping strategy is applied to synthesize xanthate‐functional poly(2‐alkyl‐2‐oxazoline)s (PAOx) that enable gold nanoparticle functionalization by a direct “grafting to” approach with citrate‐stabilized gold nanoparticles (AuNPs). Owing to the presence of remaining citrate groups, the obtained PAOx@AuNPs exhibit dual stabilization by repulsive electrostatic and steric interactions giving access to water soluble molecular AND logic gates, wherein environmental temperature and ionic strength constitute the input signals, and the solution color the output signal. The temperature input value could be tuned by variation of the PAOx polymer composition, from 22 °C for poly(2‐ⁿpropyl‐2‐oxazoline)@AuNPs to 85 °C for poly(2‐ethyl‐2‐oxazoline)@AuNPs. Besides, advancing the fascinating field of molecular logic gates, the present research offers a facile strategy for the synthesis of PAOx@AuNPs of interest in fields spanning nanotechnology and biomedical sciences. In addition, the functionalization of PAOx with xanthate offers straightforward access to thiol‐functional PAOx of high interest in polymer science.     

Design of high speed LVDS transceiver ICs

The design of low-power LVDS(low voltage differential signaling) transceiver ICs is presented.The LVDS transmitter integrates a common-mode feedback control on chip,while a specially designed pre-charge circuit is proposed to improve the speed of the circuit,making the highest data rate up to 622 Mb/s.For the LVDS receiver design, the performance degradation issues are solved when handling the large input common mode voltages of the conventional LVDS receivers.In addition,the LVDS receiver also supports ...     

A 6 Gbps/pin Low‐Power Half‐Duplex Active Cross‐Coupled LVDS Transceiver with Switched Termination

A novel linear switched termination active cross‐coupled low‐voltage differential signaling (LVDS) transceiver operating at 1.5 GHz clock frequency is presented. On the transmitter side, an active cross‐coupled linear output driver and a switched termination scheme are applied to achieve high speed with low current. On the receiver side, a shared preamplifier scheme is employed to reduce power consumption. The proposed LVDS transceiver implemented in an 80 nm CMOS process is successfully demonstrated to provide a data rate of 6 Gbps/pin, an output data window of 147 ps peak‐to‐peak, and a data swing of 196 mV. The power consumption is measured to be 4.2 mW/pin at 1.2 V.     

Low‐Temperature,Nontoxic Water‐Induced Metal‐Oxide Thin Films and Their Application in Thin‐Film Transistors

Here, a simple, nontoxic, and inexpensive “water‐inducement” technique for the fabrication of oxide thin films at low annealing temperatures is reported. For water‐induced (WI) precursor solution, the solvent is composed of water without additional organic additives and catalysts. The thermogravimetric analysis indicates that the annealing temperature can be lowered by prolonging the annealing time. A systematic study is carried out to reveal the annealing condition dependence on the performance of the thin‐film transistors (TFTs). The WI indium‐zinc oxide (IZO) TFT integrated on SiO₂ dielectric, annealed at 300 °C for 2 h, exhibits a saturation mobility of 3.35 cm² V^?1 s^?1 and an on‐to‐off current ratio of ≈10⁸. Interestingly, through prolonging the annealing time to 4 h, the electrical parameters of IZO TFTs annealed at 230 °C are comparable with the TFTs annealed at 300 °C. Finally, fully WI IZO TFT based on YO_x dielectric is integrated and investigated. This TFT device can be regarded as “green electronics” in a true sense, because no organic‐related additives are used during the whole device fabrication process. The as‐fabricated IZO/YO_x TFT exhibits excellent electron transport characteristics with low operating voltage (≈1.5 V), small subthreshold swing voltage of 65 mV dec^?1 and the mobility in excess of 25 cm² V^?1 s^?1.     

Highly Sensitive Non‐Classical Strain Gauge Using Organic Heptazole Thin‐Film Transistor Circuit on a Flexible Substrate

A non‐classical organic strain gauge as a voltage signal sensor is reported, using an inverter‐type thin‐film transistor (TFT) circuit, which is able to sensitively measure a large quantity of elastic strain (up to ≈2.48%), which approaches an almost folding state. Novel heptazole‐based organic TFTs are chosen to be incorporated in this gauge circuit; organic solid heptazole has small domain size in general. While large crystal domain‐pentacene TFTs seldom show sufficient current variation upon mechanical bending for tensile strain, these heptazole TFTs demonstrate a significant variation for the same strain condition as applied to pentacene devices. In addition, the pentacene channel does not recover to its original electric state after bending but heptazole channels are very elastic and reversible, even after going through serious bending. More interesting is that the heptazole TFTs show only a little variation of signal current under horizontal direction strain, while they make a significant amount of current decrease under vertical direction strain. Utilizing the anisotropic response to the tensile bending strain, an ultrasensitive voltage output strain gauge composed of a horizontally and vertically oriented TFT couple is demonstrated.     

A Solution‐Processed UV‐Sensitive Photodiode Produced Using a New Silicon Nanocrystal Ink

This article presents a simple and effective method of functionalizing hydrogen‐terminated silicon (Si) nanocrystals (NCs) to form a high‐quality colloidal Si NC ink with short ligands that allow charge transport in nanocrystal solid films. Si NCs fabricated by laser‐pyrolysis and acid etching are passivated with allyl disulfide via ultraviolet (UV)‐initiated hydrosilylation to form a stable colloidal Si NC ink. Then a Si NC‐based photodiode is directly fabricated in air from this ink. Only a solution‐processed poly(3,4‐ethylenedioxy‐thiophene):poly(styrene sulfonate) (PEDOT: PSS) electron blocking layer and top‐ and bottom‐contacts are needed along with the Si NC layer to construct the device. A Schottky‐junction at the interface between the Si NC absorber layer and aluminum (Al) back electrode drives charge separation in the device under illumination. The unpackaged Si NC‐based photodiode exhibites a peak photoresponse of 0.02 A W^?1 to UV light in air, within an order of magnitude of the response of commercially available gallium phosphide (GaP), gallium nitride (GaN), and silicon carbide (SiC) based photodetectors. This provides a new pathway to large‐area, low‐cost solution‐processed UV photodetectors on flexible substrates and demonstrates the potential of this new silicon nanocrystal ink for broader applications in solution‐processed optoelectronics.     

Adaptive antennas for MIMO OFDM‐CDMA communication systems

In this paper, we propose symbol‐based receivers for orthogonal frequency division multiplexing (OFDM) code‐division multiple‐access (CDMA) multiple‐input‐multiple‐output (MIMO) communications in multipath fading channels. For multiuser and multipath fading environments, both intersymbol interference and multiple‐access interference must be considered. We propose narrowband and wideband antennas and Wiener code filter for MIMO OFDM‐CDMA systems. The proposed receivers are updated symbol‐by‐symbol to achieve low computational complexity. Simulation results show that the proposed Wiener code filter can improve the system performance for the proposed adaptive antennas. The wideband antenna can achieve better error‐rate performance than that of the narrowband antenna when multipath effect exists. The convergence rate of the recursive least squares antennas is faster than that of the least mean square antennas. Copyright © 2013 John Wiley & Sons, Ltd.     

A universal roll‐to‐roll slot‐die coating approach towards high‐efficiency organic photovoltaics

This work develops a combinational use of solvent additive and in‐line drying oven on the flexible organic photovoltaics to improve large‐area roll‐to‐roll (R2R) slot‐die coating process. Herein, addition of 1,8‐diiodooctane (DIO) in the photoactive layer is conducted to yield a performance of 3.05% based on the blending of poly(3‐hexylthiophene) (P3HT) and [6,6]‐phenyl C₆₁‐butyric acid methyl ester (PC₆₁BM), and a very promising device performance of 7.32% based on the blending of poly[[4,8‐bis[(2‐ethylhexyl)oxy] benzo[1,2‐b:4,5‐b’] dithiophene‐2,6‐diyl] [3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]thieno[3,4‐b]thiophenediyl]] (PTB7) and [6,6]‐phenyl C₇₁‐butyric acid methyl ester (PC₇₁BM). Based on this R2R slot‐die coating approach for various polymers, we demonstrate the high‐performance result with respect to the up‐scaling from small high‐PCE cell to large‐area module. This present study provides a route for fabricating a low‐cost, large‐area, and environmental‐friendly flexible organic photovoltaics.     

High‐Resolution Monolithic Integrated Tribotronic InGaZnO Thin‐Film Transistor Array for Tactile Detection

Tactile detection is a crucial technology in many fields, such as electronic skin, touch screen control, human prostheses, and screen fingerprint identification. Tribotronics has demonstrated active mechanosensation from external mechanical stimuli, which greatly enriches the sensing mechanisms of tactile detection. In this work, a monolithic integrated indium‐gallium‐zinc‐oxide (InGaZnO or IGZO) thin‐film transistor (TFT) array is developed for high‐resolution tactile detection. By using the conventional semiconductor fabrication processes, each IGZO TFT cell in the array shows uniform electrical performance. In addition, the drain–source current can be individually tuned by the electrostatic potential generated by the contact electrification between a movable gate and the gate dielectric. The monolithic integrated array displays a relatively high resolution of 12 pixels per inch and can realize a millimeter‐level tactile perception and motion tracking. This work presents a facile and viable strategy toward micro/nano‐scale tribotronics, which can realize high‐resolution and large‐scale tactile detection.     

Effect of Oxygen Binding Energy on the Stability of Indium‐Gallium‐Zinc‐Oxide Thin‐Film Transistors

From a practical viewpoint, the topic of electrical stability in oxide thin‐film transistors (TFTs) has attracted strong interest from researchers. Positive bias stress and constant current stress tests on indium‐gallium‐zinc‐oxide (IGZO)‐TFTs have revealed that an IGZO‐TFT with a larger Ga portion has stronger stability, which is closely related with the strong binding of O atoms, as determined from an X‐ray photoelectron spectroscopy analysis.     

Influence of Thiol Self‐Assembled Monolayer Processing on Bottom‐Contact Thin‐Film Transistors Based on n‐Type Organic Semiconductors

The performance of bottom‐contact thin‐film transistor (TFT) structures lags behind that of top‐contact structures owing to the far greater contact resistance. The major sources of the contact resistance in bottom‐contact TFTs are believed to reflect a combination of non‐optimal semiconductor growth morphology on the metallic contact surface and the limited available charge injection area versus top‐contact geometries. As a part of an effort to understand the sources of high charge injection barriers in n‐channel TFTs, the influence of thiol metal contact treatment on the molecular‐level structures of such interfaces is investigated using hexamethyldisilazane (HMDS)‐treated SiO₂ gate dielectrics. The focus is on the self‐assembled monolayer (SAM) contact surface treatment methods for bottom‐contact TFTs based on two archetypical n‐type semiconductors, α,ω‐diperfluorohexylquarterthiophene (DFH‐4T) and N,N′bis(n‐octyl)‐dicyanoperylene‐3,4:9,10‐bis(dicarboximide) (PDI‐8CN₂). TFT performance can be greatly enhanced, to the level of the top contact device performance in terms of mobility, on/off ratio, and contact resistance. To analyze the molecular‐level film structural changes arising from the contact surface treatment, surface morphologies are characterized by atomic force microscopy (AFM) and scanning tunneling microscopy (STM). The high‐resolution STM images show that the growth orientation of the semiconductor molecules at the gold/SAM/semiconductor interface preserves the molecular long axis orientation along the substrate normal. As a result, the film microstructure is well‐organized for charge transport in the interfacial region.     

低温多晶Si TFT-LCD技术

介绍了大面积低温多晶Si薄膜晶体管液晶显示技术的发展水平。最近，低温多晶Si薄膜晶体管业已取得很大进展，比如高质量多晶Si薄膜的受激准分子激光退火(激光再结晶）工艺，大面积掺杂用离子掺杂工艺，以及低温原子团簇射式化学汽相沉积工艺。     

Bandwidth‐Efficient Selective Retransmission for MIMO‐OFDM Systems

In this work, we propose an efficient selective retransmission method for multiple‐input and multiple‐output (MIMO) wireless systems under orthogonal frequency‐division multiplexing (OFDM) signaling. A typical received OFDM frame may have some symbols in error, which results in a retransmission of the entire frame. Such a retransmission is often unnecessary, and to avoid this, we propose a method to selectively retransmit symbols that correspond to poor‐quality subcarriers. We use the condition numbers of the subcarrier channel matrices of the MIMO‐OFDM system as a quality measure. The proposed scheme is embedded in the modulation layer and is independent of conventional hybrid automatic repeat request (HARQ) methods. The receiver integrates the original OFDM and the punctured retransmitted OFDM signals for more reliable detection. The targeted retransmission results in fewer negative acknowledgements from conventional HARQ algorithms, which results in increasing bandwidth and power efficiency. We investigate the efficacy of the proposed method for optimal and suboptimal receivers. The simulation results demonstrate the efficacy of the proposed method on throughput for MIMO‐OFDM systems.