Observation of Phase Transition from Dissolved Organic Semiconducting Materials to Solid Film during Drying

We studied the formation dynamics of low-molecular-weight organic semiconducting molecules of N,N′-bis[4-[bis(3-methylphenyl)amino]phenyl]-N,N′-diphenylbenzidine (DNTPD) during solvent evaporation. We dropped the DNTPD–toluene solution on a glass substrate and performed in situ measurements of mass, temperature, scattered light intensity, and photoluminescence (PL). We found that both light scattering and PL measurements were able to detect the onset of solid film formation from dissolved organic semiconducting materials. When a solid thin film forms during drying, sudden changes in scattered light and PL are observed. Furthermore, we also found that a period of time after the onset was necessary for completion of thin solid film formation. Observations and in situ PL measurement during thin-film formation by spin coating revealed that this period of time affected the optical properties of the film. This result indicates that quantitative information on the film formation process is quite important to obtain thin films with desired properties by coating and drying. Our in situ measurements were simple and practical approaches to monitor the formation dynamics of organic thin films during drying.     

Halogen bonds in 2D supramolecular self-assembly of organic semiconductors

Weak interactions between bromine, sulphur, and hydrogen are shown to stabilize 2D supramolecular monolayers at the liquid-solid interface. Three different thiophene-based semiconducting organic molecules assemble into close-packed ultrathin ordered layers. A combination of scanning tunneling microscopy (STM) and density functional theory (DFT) elucidates the interactions within the monolayer. Electrostatic interactions are identified as the driving force for intermolecular BrBr and BrH bonding. We find that the SS interactions of the 2D supramolecular layers correlate with the hole mobilities of thin film transistors of the same materials.     

Electronic properties of thermally formed thin iron oxide films

The oxide layer, present between an organic coating and the substrate, guarantees adhesion of the coating and plays a determinating role in the delamination rate of the organic coating. The purpose of this study is to compare the resistive and semiconducting properties of thermal oxides formed on steel in two different atmospheres at 250 °C: an oxygen rich atmosphere, air, and an oxygen deficient atmosphere, N₂. In N₂, a magnetite layer grows while in air a duplex oxide film forms composed by an inner magnetite layer and a thin outer hematite scale. The heat treatment for different amounts of time at high temperature was used as method to sample the thickness variation and change in electronic and semiconducting properties of the thermal oxide layers. Firstly, linear voltammetric measurements were performed to have a first insight in the electrochemical behavior of the thermal oxides in a borate buffer solution. Electrochemical impedance spectroscopy in the same buffer combined with the Mott-Schottky analysis were used to determine the semiconducting properties of the thermal oxides. By spectroscopic ellipsometry (SE) and atomic force microscopy (AFM), respectively, the thickness and roughness of the oxide layers were determined supporting the physical interpretation of the voltammetric and EIS data. These measurements clearly showed that oxide layers with different constitution, oxide resistance, flatband potential and doping concentration can be grown by changing the atmosphere.     

Barrier Layers in Semiconducting Barium Titanate Glass-Ceramics

Methods were developed for the reduction and subsequent oxidation of glass-crystallized barium titanate for obtaining surface and grain-boundary barrier-layer dielectrics, together with the solid state chemistry compatible with glassmelting, crystallization, and the diffusion processes involved. The material obtained can be described as an interconnected dispersion of semiconducting BaTiO₃ crystallites sealed in a mostly glassy silicate matrix. Oxidation of this semiconductor leads to surface layers with very high dielectric strength, up to 10⁶ V/cm, and resistivity of the order of 10¹⁴ω·cm. The properties of compound barriers consisting of a space charge layer and a thin insulating film are also described and conditions leading to glass-ceramic materials having a positive temperature coefficient of resistance (PTCR) by the use of an anionic dopant are discussed.     

基于金属浮栅层有机薄膜非易失性存储器的制备与表征

以聚甲基丙烯酸甲酯(PMMA)为栅介质,以并五苯为有机薄膜制备了有机薄膜非易失性存储器,研究基于热蒸发金属金浮栅层的存储行为。在2 s脉冲的偏压下,浮栅层通过充放电过程可导致明显的阈值电压偏移。在1 V的脉冲电压下可实现电荷的写入/擦除操作,在6 V的脉冲电压下可获得30.0 V的存储窗口。实验结果表明,基于金属浮栅层并以并五苯作为有机薄膜来制备非易失性存储器具有一定的研究价值和应用前景。     

Hot-rolling nanowire transparent electrodes for surface roughness minimization

Silver nanowire transparent electrodes are a promising alternative to transparent conductive oxides. However, their surface roughness presents a problem for their integration into devices with thin layers such as organic electronic devices. In this paper, hot rollers are used to soften plastic substrates with heat and mechanically press the nanowires into the substrate surface. By doing so, the root-mean-square surface roughness is reduced to 7 nm and the maximum peak-to-valley value is 30 nm, making the electrodes suitable for typical organic devices. This simple process requires no additional materials, which results in a higher transparency, and is compatible with roll-to-roll fabrication processes. In addition, the adhesion of the nanowires to the substrate significantly increases.     

Organic materials for organic electronic devices

In recent years, organic electronic devices which use organic materials as an active layer have gained considerable interest as light-emitting devices, energy converting devices and switching devices in many applications. In these organic electronic devices, the organic materials play a key role of managing the device performances and various organic materials have been developed to improve the device performances of organic electronic devices. In this paper, recent developments of organic electronic materials for organic light-emitting diodes and organic solar cells were reviewed.     

Interface morphology snapshots of vertically segregated thin films of semiconducting polymer/polystyrene blends

We present atomic force microscopic images of the interphase morphology of vertically segregated thin films spin coated from two-component mixtures of poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene-vinylene] (MEH-PPV) and polystyrene (PS). We investigate the mechanism leading to the formation of wetting layers and lateral structures during spin coating using different PS molecular weights, solvents and blend compositions. Spinodal decomposition competes with the formation of surface enrichment layers. The spinodal wavelength as a function of PS molecular weight follows a power-law similar to bulk-like spinodal decomposition. Our experimental results indicate that length scales of interface topographical features can be adjusted from the nanometer to micrometer range. The importance of controlled arrangement of semiconducting polymers in thin film geometries for organic optoelectronic device applications is discussed.     

Printed organic transistors and molded plastic lasers

We describe the use of microcontact printing and elastomeric molding for fabricating two types of devices that incorporate thin films of active organic materials: thin film transistors and plastic lasers. The simplicity of these techniques and the good performance of devices formed with them suggest their potential utility for emerging applications of organic materials in electronic and optical systems.     

High performance EMI shielding applications of Co0.5Ni0.5CexSmyFe2-x-yO4 nanocomposite thin films

The fast development in the compact and wearable opto-electronics devices need a high-performance electromagnetic (EM) shielding materials that are shows a unique feature like lightweight and flexible in characteristics that increase the problems of electromagnetic pollution. At present technological aspects, the absorption predominant microwave shielding materials are gain the huge demand for preventing the major problems of electromagnetic interference over the modern electronic devices as well as environment. In the report we presents synthesis of multifunctional composite thin film material that adequately includes the exceptional EMI shielding, mechanical flexibility and magnetic properties of composite thin film for portable and wearable electronic devices which could be operated at GHz frequencies. The Co_0.5Ni_0.5Ce_xSm_yFe_2-x-yO₄ (denoted as CNCSF) its scanning electron microscopy (SEM) micrographs revel the fact that the samples highly agglomerated characteristics features of the prepared thin film samples, this agglomerated structure of the composite film will enhance the EMI shielding performances and strain sensing responses. Further, the prepared thin films were subjected to characterized XRD and Raman spectroscopic techniques to analyse the crystallinity and different functional groups present in the prepared thin films. By doping of samarium and cesium nanoparticles into the Co_0.5Ni_0.5Fe_2-x-yO₄ forms the superior conducting islands and enhances the dielectric and magnetic properties of the composite thin films. Owing to the improved dielectric and magnetic properties this x,y = 0.02 ferrites based thin film nanocomposite with the 0.4 mm thickness exhibit the absorption predominated outstanding electromagnetic shielding responses in the order of ?23 dB which is almost equal to 99.67% of shielding efficiency in broad band microwave frequencies. Furthermore, these material-based nanocomposite shields show exceptional stability in EMI shielding efficiency under the different mechanical stretching strains. In addition to superior excellent shielding material, this material-based nanocomposite thin film shows an exceptional strain sensing behaviour, which evident that multifunctional applications of this ferrites based thin material. Owing to the all-unique properties like light weight, flexibility, outstanding EMI-SE and excellent strain sensing behaviour, these ferrites-based material thin film could be employed in flexible and fortable electronic devices as crafty jacket on shield.     

Bismuth Zinc Niobate Thin Film Multilayer Capacitors with Cu Electrodes Fabricated at Low Temperature by RF Magnetron Sputtering

Thin film multilayer capacitors (MLCs) composed of amorphous Bi_1.5Zn_1.0Nb_1.5O₇ (BZN) dielectric layers with Cu internal electrodes were fabricated by radio‐frequency magnetron sputtering at a temperature below 150°C. Both BZN thin films and Cu internal electrodes were deposited in situ through a set of steel shadow masks at room temperature and postannealed at 150°C. The BZN dielectric layers used in the MLCs are amorphous and the thickness for each BZN layer is approximately 220 nm. Metallic Cu layer used as the internal electrode is about 50 nm thick. Auger electron spectroscopy analysis indicates that there are no diffusion between BZN films and Cu electrodes, as well as no oxidation of Cu electrodes during the fabrication process owing to room‐temperature deposition and low‐temperature postannealing (150°C). The thin film MLCs with different number of BZN layers were fabricated. The thin film MLCs with five BZN layers exhibit promising properties with dielectric constant of 72, capacitance density of 1600 nF/cm², and loss tangent of 5.4% at 10 kHz. These results suggest that the BZN thin film MLCs have potential applications for the embedded PCBs.     

Synthesis and characterization of novel fulleropyrrolidine in P3HT blended bulk heterojunction solar cells

Synthesis of novel fullerene derived electron acceptors and characterization of their organic photovoltaic (OPV) properties is important for advancing fundamental knowledge towards developing next generation organic solar cells. We report the synthesis of a novel fulleropyrrolidine derivative C60-fused N-(3-methoxypropyl)-2-(carboxyethyl)-5-(4-cyanophenyl)fulleropyrrolidine (NCPF) by 1,3-dipolar cycloaddition reaction and characterization of NCPF by ¹H NMR, ¹³C NMR, MALDI-TOFMS, FT-IR, UV–Vis and CV. The synthesized NCPF fullerene derivative showed good solubility in common organic solvents such as chlorobenzene and 1,2 dichlorobenzene important for film formation, with optical absorbance and electronic properties comparable to PCBM. Optical micrographs of P3HT:PCBM thin films reveal formation of sparse, phase segregated needle shape PCBM micro-crystalline aggregates after 1 h of annealing at 150 °C whose length follows nucleation and growth kinetics over 24 h. In contrast, the P3HT:NCPF thin films exhibit homogeneity over 24 h, possibly due to weaker interparticle vanderWaals forces and/or stronger interactions with P3HT. This long term morphological stability of P3HT:NCPF is important for extended use in OPV applications. At an order of magnitude smaller scale, AFM of as cast and 10 min annealed at 150 °C P3HT:PCBM and P3HT:NCPF films reveal mostly smooth surfaces, with some NCPF cluster formation. Grazing incidence wide angle X-ray scattering (GIWAXS) measurements of P3HT:NCPF films indicate an increase of P3HT crystallinity with thermal annealing, leading to improvement in device performance. Photovoltaic devices fabricated with the active layer of P3HT:NCPF and P3HT:PCBM sandwiched between ITO/PEDOT:PSS and Al layer showed comparable performance upon short term annealing.     

YBa2Cu3O7-x薄膜的制备与半导体性能的研究

采用高温固相反应制备φ60mmYBa2Cu3O7-x－（YBCO）靶材;通过直流磁控溅射后退火制备具有不同过滤层（SiO2/Si,ZrO2/SiO2/Si)的薄膜,对于Si为衬底的YBa2Cu3O7-x薄膜,当x＞0．5时,薄膜的导电性由超导态转向半导体状态,进行了X射每衍射（XRD）分析,电阻温度系数（TRC）和Hall系数测试,并进行Raman散射的微观分析实验,认为半导体薄膜可用作室温工作的红外测辐射热计（Bolometer)灵敏元。     

Effect of seeding layer on orientation control of potassium niobate thin film by CSD

This paper focuses on the orientation control of the KN thin film on Si wafer by chemical solution deposition (CSD). We selected the PbO layer and PZT layers as the seeding layer in order to control the crystal orientation of the resulting KN thin film. Crystalline phase in KN thin film was identified by XRD, and the degree of c-axis orientation was calculated from XRD analysis. The resultant KN thin film was orthorhombic perovskite single phase. As a result, highly c-axis oriented thin film (about 90%) was deposited by using PbO seeding layer. The dielectric constant of the resultant KN thin film was measured by impedance analyzer. The dielectric constant of highly c-axis oriented KN thin film was compared with that of the c-axis of KN single crystal.     

Interfacial polarization and layer thickness effect on electrical insulation in multilayered polysulfone/poly(vinylidene fluoride) films

In this study, we report layer thickness effect on the electrical insulation property of polysulfone (PSF)/poly(vinylidene fluoride) (PVDF) multilayer films having a fixed composition of PSF/PVDF = 30/70 (vol./vol.). Breakdown strength, dielectric lifetime, and electrical conductivity were studied for 32- and 256-layer films having various total film thicknesses. Among these films, those having thinner PVDF and PSF layers exhibited lower breakdown strength, shorter lifetime, and higher electrical conductivity than those having thicker layers. These experimental results were explained by Maxwell–Wagner–Sillars interfacial polarization due to contrasts in dielectric constant and electronic conductivity for PVDF and PSF, respectively. When both PVDF and PSF layers were thick (ca. > 100–200 nm), more space charges were available in PVDF and no electronic conduction was allowed for PSF. These accumulated interfacial charges could serve as effective traps for injected electrons from metal electrodes under high electric fields. As a result, reduced electrical conductivity and enhanced breakdown strength/dielectric lifetime properties were obtained. When both layers were thin (ca. < 100 nm), fewer space charges were available in PVDF and significant electronic conduction through PSF resulted in low interfacial polarization. Consequently, higher electrical conductivity, lower breakdown strength, and shorter lifetime were observed. These results provide us insights into potential physics to enhance electrical insulation property of polymer films using a multilayered structure having large dielectric constant contrast.     

Preparation and characterization of thin films of the poly(p‐phenylene vinylene) semiconducting polymer

Conjugated polymers have been the subject of many studies because of their widespread applications in electronic and optoelectronic devices. Poly(p‐phenylene vinylene) is a leading semiconducting polymer in optical applications. This work is focused on the development of thin films of poly(p‐phenylene vinylene) by spin coating and their characterization with Fourier transform infrared spectroscopy, X‐ray diffraction, and scanning electron microscopy to understand their changes. An empirical model has been developed to show the effect of the variables—the spin speed, polymer concentration, and spin time—on the film thickness. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

All-organic Poly(butyl methacrylate)/Poly(vinylidenefluoride-trifluoroethylene) Dielectric Composites with Higher Permittivity and Low Dielectric Loss for Energy Storage Application

With the rapid development of electronic industry and technology, there are increasingly stringent requirements on dielectric materials with higher permittivity, lower loss, and enhanced breakdown field. Since single dielectric material cannot meet the demands of industrialization, polymer-based dielectric materials with better quality have been widely applied. This study focused on a poly(butyl methacrylate/poly(vinylidene fluoride-trifluoroethylene) dielectric composite thin film, which were prepared by solution casting method. X-ray diffraction and differential scanning calorimetry data indicated that introducing poly(butyl methacrylate) led to increase in the crystallinity. The result of scanning electron microscopy showed the good compatibility between poly(vinylidene fluoride-trifluoroethylene) and poly(butyl methacrylate). Besides, the dielectric film remained good mechanical property. The dielectric properties were studied as a function of filler content and frequency. The results showed that the permittivity was as high as 13.3, while the breakdown field was 322?MV m^?1 when the fraction of poly(butyl methacrylate) was 10%. Blending poly(butyl methacrylate) improved the dielectric performance of the poly(vinylidene fluoride-trifluoroethylene).     

High-temperature polyimide nanofoams for microelectronic applications

Foamed polyimides have been developed in order to obtain thin film dielectric layers with very low dielectric constants for use in microelectronic devices. In these systems the pore sizes are in the nanometer range, thus, the term ‘nanofoam’. The polyimide foams are prepared from block copolymers consisting of thermally stable and thermally labile blocks, the latter being the dispersed phase. Foam formation is effected by thermolysis of the thermally labile block, leaving pores of the size and shape corresponding to the initial copolymer morphology. Nanofoams prepared from a number of polyimides as matrix materials were investigated as well as from a number of thermally labile polymers. The foams were characterized by a variety of experiments including TEM, SAXS, WAXD, DMTA, density measurements, refractive index measurements and dielectric constant measurements. Thin film foams, with high thermal stability and low dielectric constants approaching 2.0, can be prepared using the copolymer/nanofoam approach.     

Low dielectric loss and enhanced tunability of Ba(Zr0.3Ti0.7)O3-based thin film by sol–gel method

In this work, dopants and buffer layers were employed to simultaneously lower the dielectric loss and enhance the dielectric tunability of Ba(Zr_0.3Ti_0.7)O₃ (BZT) thin films. The BZT, 1 mol% La doping BZT (BZTL) with and without La_0.5Sr_0.5CoO₃ (LSCO) buffer layers were prepared by sol–gel technique. The dielectric properties of the thin films were investigated as a function of frequency and current bias field. As a result, the BZTL thin film with LSCO buffer layer showed lower dielectric loss and higher tunability simultaneously, which can be a promising candidate for tunable microwave device applications.     

Monolayer-Mediated Deposition of Tantalum(V) Oxide Thin Film Structures from Solution Precursors

Integration of oxide thin films with semiconductor substrates is a critical technology for a variety of microelectronic memory and circuit applications. Patterned oxide thin film devices are typically formed by uniform deposition followed by postdeposition ion-beam or chemical etching in a controlled environment. This paper reports details of an ambient atmosphere technique which allows selective deposition of dielectric oxide thin layers without postdeposition etching. In this method, substrate surfaces are selectively functionalized with hydrophobic self-assembled monolayers of octadecyltrichlorosilane by microcontact printing (μ-CP). Sol-gel deposition of ceramic oxides on these functionalized substrates, followed by mild, nonabrasive polishing, yields high-quality, patterned oxide thin layers only on the unfunctionalized regions. A variety of micrometer-scale dielectric oxide devices have been fabricated by this process, with lateral resolutions as fine as 4 μm. In this paper, we describe the solution chemistry, evolution of microstructure, and electrical properties of Ta₂O₅ thin films, as well as the stress-related mechanism which enables selective de-adhesion and resultant patterning. Selectively deposited, 80-120 nm thick Ta₂O₅ thin film capacitors were crystallized on platinized silicon at 700-800°C, and had dielectric constants of 18-25 depending upon the processing conditions, with 1 V leakage current densities as low as 2 × 10⁻⁸ A/cm². The ability to selectively deposit Ta₂O₅ and other electrical ceramics (such as LiNbO₃ and PbTiO₃) on a variety of technologically important substrate materials suggests broad potential for integrated circuit and hybrid microelectronics applications.