Inverse opal photonic crystal of chalcogenide glass by solution processing

Chalcogenide opal and inverse opal photonic crystals were successfully fabricated by low-cost and low-temperature solution-based process, which is well developed in polymer films processing. Highly ordered silica colloidal crystal films were successfully infilled with nano-colloidal solution of the high refractive index As(30)S(70) chalcogenide glass by using spin-coating method. The silica/As-S opal film was etched in HF acid to dissolve the silica opal template and fabricate the inverse opal As-S photonic crystal. Both, the infilled silica/As-S opal film (Δn ~ 0.84 near λ=770 nm) and the inverse opal As-S photonic structure (Δn ~ 1.26 near λ=660 nm) had significantly enhanced reflectivity values and wider photonic bandgaps in comparison with the silica opal film template (Δn ~ 0.434 near λ=600 nm). The key aspects of opal film preparation by spin-coating of nano-colloidal chalcogenide glass solution are discussed. The solution fabricated "inorganic polymer" opal and the inverse opal structures exceed photonic properties of silica or any organic polymer opal film. The fabricated photonic structures are proposed for designing novel flexible colloidal crystal laser devices, photonic waveguides and chemical sensors.     

Layer-by-Layer Assembly of Monolayer Films Precisely Controlled by LB Technology to Realize Low-Energy Consumption and High-Stability Ternary Data-Storage Devices

Organic semiconductor devices with low energy consumption and excellent stability are highly desirable. Controlling the intermolecular alignment orientation by designing the molecular structure or optimization of the film preparation process is an alternative way to achieve this goal. In this paper, a new idea was proposed to realize the formation of an aligned monomolecular layer and multimolecular layer thin films on the electrode substrate by controlling the surface pressure of molecular layer on the liquid surface by LB technology. An amphiphilic π-conjugated D−A molecule was synthesized, and the influence of spin coating and LB technology on intermolecular ordered stacking in the film and the electrical memory performance were investigated. The results demonstrated that the film fabricated by LB technology has some advantages compared with that fabricated by spin-coating method, such as higher crystallinity, lower surface roughness and better-organized monomolecular and multimolecular layer, which significantly promoted the performance of the electrical memory device with lower power consumption and longer stability.     

High performance organic thin film transistors with solution processed TTF-TCNQ charge transfer salt as electrodes

Fabrication of high-performance organic thin film transistors (OTFTs) with solution processed organic charge transfer complex (TTF-TCNQ) film as bottom contact source-drain electrodes is reported. A novel capillary based method was used to deposit the source-drain electrodes from solution and to create the channel between the electrodes. Both p- and n-type OTFTs have been fabricated with solution deposited organic charge transfer film as contact electrodes. Comparison of the device performances between OTFTs with TTF-TCNQ as source-drain electrodes and those with Au electrodes (both top and bottom contact) indicate that better results have been obtained in organic complex film contacted OTFT. The high mobility, low threshold voltage, and efficient carrier injection in both types of OTFTs implies the potential use of the TTF-TCNQ based complex material as low-cost contact electrodes. The lower work function of the TTF-TCNQ electrode and better contact of the complex film with the organic thin film owing to the organic-organic interface results in efficient charge transfer into the semiconductor yielding high device performance. The present method having organic metal as contact materials promises great potential for the fabrication of all-organics and plastic electronics devices with high throughput and low-cost processing.     

吲哚方酸菁半导体在场效应晶体管中的应用

研究了2,3,3-三甲基-1-H-吲哚方酸菁的场效应性质, 通过X射线衍射证实了方酸菁分子内电荷分离结构以及分子间面面堆积模式, 并在Si/SiO₂基片上通过真空蒸镀和旋涂的方法制备了p型晶体管器件. 通过对器件性能与沟道形态的研究, 我们发现退火处理能促进方酸菁薄膜由无定形态向多晶态转变, 从而使薄膜晶体管的迁移率从10^-5 cm²?V^-1?s^-1量级提高到10^-3 cm²?V^-1?s^-1量级. 顶接触结构单晶器件获得了7.8×10^-2 cm²?V^-1?s^-1的迁移率. 未封装的方酸菁晶体管在大气中也表现出较好的稳定性.     

The highly conducting carbon electrodes derived from spin-coated polyacrylonitrile films

Carbon films prepared from pyrolyzation of spin-casted polyacrylonitrile (PAN) thin films display high electrical conductivity (600 S/cm, at 1000 °C carbonization), low sheet resistance (about 100 Ω/square at the PAN film thickness of 70 nm) and partial transmittance. These pyrolyzed PAN (PPAN) films were patterned as bottom electrodes by photolithography, and utilized as drain and source electrodes to fabricate organic field-effect transistor (OFET) devices with a p-type semiconductor (P3HT) and an n-type semiconductor (DPP-containing quinoidal small molecule) through a spin-coating procedure. The results showed that the devices with the PAN electrodes exhibited almost the same excellent performance without any further modification compared to those devices with traditional Au electrodes. Since these PPAN films had the advantages of low-cost, high performance, easier for large-area fabrication, thermal and chemical stability, it should be a promising electrode material for organic electrodes.     

High-performance,solution-processed organic thin film transistors from a novel pentacene precursor

The Lewis acid-catalyzed Diels-Alder reaction of the organic semiconductor pentacene with N-sulfinylacetamide yields a soluble adduct. Spin-coated thin films of this adduct undergo solid-phase conversion to form thin films of pentacene at moderate temperatures. Organic thin film transistors fabricated by spin-coating this adduct, followed by thermal conversion to pentacene, exhibit the highest mobility reported to date for a solution-processed organic semiconductor.     

Fabrication of flexible thin organic transistors by trace water assisted transfer method

In this paper, we develop a facile peel-off method to transfer organic thin film to various substrates. Remarkably, the method uses only micro volume water as an assist to peel off PAN film, which reduces the risk of contamination by solvent and greatly contributes to the performance maintenance.     

旋涂法制备功能薄膜的研究进展

作为众多的薄膜制备方法之一,旋涂法具备薄膜厚度精确可控、高性价比、节能、低污染等优势,在微电子技术、纳米光子学、生物学、医学等领域中有着广阔的应用前景.本文简单介绍了旋涂法的模型、机理及其主要参数的估算方法,并总结了近几年来用旋涂法制备光学、微电子学等功能薄膜的新进展,最后对旋涂法的发展前景进行了展望.     

Controlled one-dimensional nanostructures in poly(3-hexylthiophene) thin film for high-performance organic field-effect transistors

With the aim of improving the field-effect mobilities in poly(3-hexylthiophene) (P3HT) thin film transistors, we controlled the nanostructures of P3HT thin film by changing the solvent vapor pressure in a spin-coating chamber during solidification. The transistors with P3HT thin films spin-coated under a high solvent vapor pressure (56.5 KPa), showing the one-dimensional nanowire morphologies, resulted in the relatively high field-effect mobilities (0.02 cm2/(V.s)) that are typically more than 1 order of magnitude higher than those prepared under ambient conditions, showing the featureless morphologies. This can be attributed to the higher solvent vapor pressure during film formation, providing the solvent is allowed to evaporate slowly and the degree of ordering within the P3HT crystalline domains is dramatically improved.     

Autonomic self-healing lipid monolayer: a new class of ultrathin dielectric

The electrical performance of stabilized lipid monolayers on H-terminated silicon is reported for the first time. We show that these 2.7 nm thick only ultrathin layers present extremely low current leakage at high electric field and high breakdown voltage that both compare favorably with the best data reported on organic thin film dielectrics. We demonstrate a very unique property of autonomic self-healing of the layer at room temperature with the total recovery of its performance after electrical breakdown. The mechanisms involved in breakdown and self-healing are described.     

An asymmetric oligomer based on thienoacene for solution processed crystal organic thin-film transistors

A novel thienoacene-based conjugated oligomer, i.e.BTTT-T-C12, was designed and synthesized. Its highly asymmetric structural feature enables the preparation of two-dimensional single-crystalline thin films in millimetre size and ~100 nm thick by a solution processing method directly on the Si/SiO(2) substrate. Single crystal organic thin film transistors exhibit a mobility of 0.70 cm(2) V(-1) s(-1) and an on/off ratio of 5.7 × 10(4).     

Plasma enhanced aerosol–gel method: a new way of preparing ceramic coatings

The sol–gel process is widely used for the production of powders, coatings and bulk materials. However, being a wet-chemical technique, it has certain limitations related to properties of aqueous colloidal solution, especially when applied as a coating. The most frequently used methods, such as dip- and spin-coating, are difficult to apply onto more complex substrates. In these cases, the aerosol–gel deposition method can be regarded as the solution of this problem. In the present article, a novel plasma enhanced aerosol–gel method of coatings production is presented. A novelty of this method is based on an integration of the aerosol–gel deposition of thin films and their low temperature plasma treatment. Owing to the above, all stages of the coatings production process—substrate preparation, film deposition, and its plasma treatment, can be carried out in a single reactor. The design and operational scheme of such device is presented in this work. Using this device, thin coatings were first deposited on substrates and then plasma treated. The effect of deposition and plasma discharge conditions on morphology and chemical structure of the films has been studied. It was found that plasma treatment had a substantial influence on all the examined properties of the aerosol–gel deposited coatings.     

Synergistic Effects of Solvent Vapor Assisted Spin-coating and Thermal Annealing on Enhancing the Carrier Mobility of Poly(3-hexylthiophene) Field-effect Transistors

Poly(3-hexylthiophene)(P3 HT) thin films, obtained by normal spin-coating and solvent vapor assisted spin-coating(SVASP) before and after thermal annealing(TA), and the corresponding devices were prepared to unravel the microstructure-property relationship, which is of great importance for the development of organic electronics. When SVASP-TA films were used as the active layers of the organic field-effect transistors,a hole mobility up to 0.38 cm~2·V~(–1)·s~(–1) was achieved. This mobility was one of the highest values and one order of magnitude higher than that of the normal spin-coating films based transistors. The relationship between the microstructure and the device performance was fully investigated by UV-Vis absorption spectra, grazing incident X-ray diffraction(GIXD), and atomic force microscopy(AFM). The impressive mobility was attributed to the high crystallinity and ordered molecule packing, which stem from the synergistic effects of SVASP and thermal annealing.     

Synthesis and thermolysis of a Diels-Alder adduct of pentacene and thiophosgene

Pentacene has excellent semi-conducting properties but its practical use in organic thin film transistors (OTFTs) gives rise to a lot of problems caused by its sensitivity to oxygen and its very low solubility. In order to solve the problems involved in the use of pentacene, we have synthesized a Diels-Alder adduct of pentacene with thiophosgene.     

ELECTRICALLY CONDUCTIVE COMPOSITE PREPARED BY ELECTROCHEMICAL POLYMERIZATION OF PYRROLE IN POLY-(p- PHENYLENE TEREPHTHALAMIDE) MATRIX

The preparation of PPy/PPTA conductive composite films by electrochemical method is presented.The first step is to cast a thin layer of poly (p-phenylene-terephthalamide) (PPTA) on a slice of Pt working electrode. The second step is to electrochemically polymerize pyrrole on the PPTA/Pt working electrode. Both of the electrical conductivity and the mechanical properties of the PPy/PPTA composite film are better than those of the pure PPy film, and the film has excellent flexibility at low temperature, even in liquid nitrogen.The SEM picture of the cross-section of PPy,/PPTA composite film showed that the two components were well mixed.Cyclic voltammograms of PPy,/PPTA film in aqueous solution showed that the conductive films could be reduced and reoxidized.     

Ordered Mesostructured Silica Films: Effect of Pore Surface on its Sensing Properties

An electrochemical resistive-type sensor device, with a mesoporous silica thin film as sensitive membrane, has been developed and characterised. The silica film has been obtained via evaporation-induced self-assembly (EISA) using a tri-block copolymer (Pluronic F-127) as templating agent. It has been deposited by dip-coating on a silicon substrate with metallic interdigitated electrodes. Fast, reversible and reproducible electrical responses to relative humidity changes have been observed for the sensor device. The conduction mechanism has been related to chemical properties, structural order and surface morphology of the porosity in the silica film, confirming the dependence on the film preparation method and overall the importance of calcination temperature.     

New strategy for enhancing performance of P3HT-based organic field-effect transistor via regulating the precipitated speed of solute in volatile solvents

In this work, a new strategy is proposed to improve the performance of poly (3-hexylthiophene-2,5-diyl) (P3HT) based organic field-effect transistor (OFET). The high orientation of P3HT chain is obtained via utilizing precipitation characteristics of P3HT in volatile CH₂Cl₂ with the temperature decrease of solution in the hot spin-coating process. Meanwhile, a small amount of 1,2-dichlorobenzene (ODCB) with high boiling point is introduced into CH₂Cl₂ to make the inner part of the film stay in liquid state for a long time, and prolong the self-organization time of P3HT chain. Compared with control device prepared in pure CH₂Cl₂, the mobility of optimized device obtained by using blended solvent increases about 20-fold, the on/off ratio enhances about three orders of magnitude, and the operation time window of spin-coating up to 30 min (control device < 30 s). With this new strategy, the film quality can be easily controlled, which provides a new method for preparation of high-performance polymer optoelectronic devices.     

Boron(III)‐Containing Donor–Acceptor Compound with Goldlike Reflective Behavior for Organic Resistive Memory Devices

A small‐molecule‐based boron(III)‐containing donor–acceptor compound has been designed and synthesized. Interesting goldlike reflective behavior was observed in the neat thin‐film sample from simple spin‐coating preparation, which can serve as a potential organic thin‐film optical reflector. The small thickness in nanometer range and the relatively smooth surface morphology, together with simple preparation and easy solution processability, are attractive features for opening up new avenues for the fabrication of reflective coatings. Moreover, this donor–acceptor compound has been employed in the fabrication of organic resistive memory device, which exhibited good performance with low turn‐on voltage, small operating bias, large ON/OFF ratio, and long retention time.     

Air-stable, solution-processable n-channel and ambipolar semiconductors for thin-film transistors based on the indenofluorenebis(dicyanovinylene) core

We present here the synthesis, characterization, and field-effect performance of a novel n-channel semiconducting molecule TIFDMT and of the corresponding thiophene-based copolymer P-IFDMT4 based on the indenofluorenebis(dicyanovinylene) core. TIFDMT-based field-effect transistors fabricated by spin-coating exhibit high electron mobilities of 0.10-0.16 cm2/V s in air, low turn-on voltages (0 to +5 V), and high on/off ratios of 10(7)-10(8). These devices also exhibit excellent air stability over a prolonged time of storage in ambient conditions. P-IFDMT4-based devices exhibit the first example of an air-stable ambipolar polymer processable from solution     

Smooth model surfaces from lignin derivatives. I. Preparation and characterization

Lignin model surfaces were prepared from aqueous alkaline solutions by spin-coating on silica wafers. Films of thicknesses between 20 and 140 nm were easily made by variations in the spinning rate or in the lignin concentration. The roughnesses of the lignin surfaces were relatively low, approximately 1.1 nm (rms) on an area of 25 microm2, as determined by atomic force microscopy imaging. The stability of the lignin films in aqueous solutions was found to be excellent. No changes in the thickness of model surfaces immersed in slightly alkaline solutions (pH 9.2) could be detected even after 5 h soaking. A 10 percent reduction in the thickness of the lignin film was observed after 5 h of exposure to a solution containing 0.1 M NaCl. This novel preparation method opens great possibilities for further fundamental studies, where interactions between lignin and other substances are of interest to investigate.