Facile and rapid production of conductive flexible films by deposition of polythiophene nanoparticles on transparent poly(ethyleneterephthalate): Electrical and morphological properties

In this work, polythiophene (PTh) nanoparticles were successfully deposited on poly(ethyleneterephthalate) (PET) substrate as thin film by a facile and rapid chemical oxidative deposition method using a binary organic solvent system in the presence of N-cetyl-N,N,N-trimethylammonium bromide (CTAB) as cationic surfactant. The electrical conductivity of PTh nanoparticles deposited on PET was optimized by adjusting the surfactant/oxidant/monomer molar ratio, monomer concentration and time of polymerization. Resulted film was conductive, transparent and flexible which can be used in electronic devices such as OLEDs. Electrical conductivity for the un-doped deposited PTh nanoparticles at oxidant/monomer molar ratio of 5:1 at 0 °C polymerized for 12 min was measured to be 1.18×10⁻² S/cm. The effect of oxidant and monomer concentration on polymerization yield was also investigated. The structural confirmation and transparency of the PTh nanoparticle coated PET films were characterized by FTIR and UV–vis spectroscopy, respectively. Field emission scanning electron microscopy (FESEM), laser particle size analysis and transmission electron microscopy (TEM) were employed for surface morphology and size distribution measurements of PTh nanoparticles. The results showed that the PTh nanoparticles are deposited as globular aggregates with average size of about 50 nm on PET.     

Preparation of conductive flexible films by in situ deposition of polythiophene nanoparticles on polyethylene naphthalate

Deposition of Polythiophene (PTh) nanoparticles on the unmodified and modified polyethylene naphthalate (PEN) films via solution based in situ chemical polymerization was investigated as conducting transparent anode electrodes in order to produce transparent conducting films with applications in opto-electronic devices, such as flexible displays. The surface of PEN films were modified by different methods. Surface modification was carried out using Piranha and alkaline (KOH) solution and ultraviolet (UV) radiation as a physical method. Combination of chemical and physical treatments (Piranha and UV) was also examined. The effect of surface modification methods on the properties of the in situ deposited PTh nanoparticles was studied. It was found that electrical conductivity increases ~20 times in effect of modification of PEN by the examined methods. Highly ordered morphology of PTh nanoparticles were observed by field emission scanning electron microscope (FESEM) in the case of surface modification by UV radiation. Hydrophilicity, transparency and surface morphology of the PEN films were found to be influenced by surface modification techniques as well.     

Synthesis of Polythiophene/Poly(3,4-ethylenedioxythiophene) Nanocomposites and Their Application in Thermoelectric Devices

Polythiophene/poly(3,4-ethylenedioxythiophene) (PTh/PEDOT) nanocomposites with luminescent characteristics and high thermoelectric (TE) performance were successfully synthesized by two-step oxidative polymerization in aqueous medium. First, PTh nanoparticles (NPs) were synthesized by use of FeCl₃/H₂O₂ as catalyst/oxidant system with poly(4-styrene sulfonic acid) (PSSA) as surfactant. PTh/PEDOT nanocomposites were then synthesized by in situ oxidative polymerization of 3,4-ethylenedioxythiophene (EDOT) on the surface of PTh NPs. The composition of the nanocomposites was controlled by varying the concentration of EDOT. Electron microscopy imaging and dynamic light scattering experiments confirmed the nanocomposites had a PTh core and a PEDOT shell/matrix. Finally, the TE performance of the PTh/PEDOT nanocomposites was investigated. The electrical conductivity and power factor of the nanocomposites were found to increase from 0.0001 S/cm to 475 S/cm and from 0.001 μW/mK² to 22.9 μW/mK², respectively, at the optimum PEDOT concentration.     

A comparative assessment of surface microstructure and electrical conductivity dependence on co-solvent addition in spin coated and inkjet printed poly(3,4-ethylenedioxythiophene):polystyrene sulphonate (PEDOT:PSS)

This study focuses on the fabrication of poly(3,4-ethylenedioxythiophene):polystyrene sulphonate (PEDOT:PSS) thin films by inkjet printing and investigates the developed surface morphology and electrical conductivity of the printed films as a function of the concentration of dimethyl sulfoxide (DMSO), added as conduction enhancing co-solvent, and Surfynol, added as a surfactant. The printed films are compared with PEDOT:PSS films fabricated by the traditional spin coating technique. Measurements of the surface tension justify including surfactant as a processing additive, where addition of 1% Surfynol results in substantial decrease of the surface tension of the PEDOT:PSS solution, whilst it also increases film surface roughness by an order of magnitude for both fabrication methods. The addition of 5 wt% DMSO is shown to result in a 10³ decrease in sheet resistance for both spin coated and inkjet printed films with both processing routes demonstrating decrease in surface roughness and coarsening of PEDOT grains as a function of the co-solvent concentration, whilst X-ray photon spectroscopy showed an increase in the surface PEDOT to PSS ratio from 0.4 to 0.5. Inkjet printed films have lower sheet resistance than the corresponding spin coated films, whilst atomic force microscopy reveals a coarser surface morphology for the inkjet printed films. The findings in this work point out at the decrease of sheet resistance due to coarsening of PEDOT grains which is linked to a decrease of surface roughness for small RMS values associated with the PEDOT grains. However, the higher surface roughness generated when Surfynol surfactant was added was not detrimental to the film’s in-plane conductivity due to the fact that these higher roughness values were unrelated to the PEDOT grains.     

Moisture absorption studies of fluorocarbon films deposited from pentafluoroethane and octafluorocyclobutane plasmas

The moisture absorption and diffusion characteristics of fluorocarbon films deposited from pentafluoroethane (PFE) and octafluorocyclobutane C₄F₈ plasmas are presented. The moisture absorption studies were carried out using a quartz crystal microbalance in a controlled environment. X-ray photoelectron spectroscopy and Fourier transform infrared (IR) spectroscopy were used to monitor the changes in bulk and surface chemical structure and composition of the deposited films. The equilibrium moisture uptake at relative humidity >90% was lower than 0.13 wt.% for films deposited from PFE or C₄F₈ monomers. Humidity cycling measurements showed no moisture chemisorption in the deposited films. Attenuated total reflectance infrared spectroscopy (ATR-IR) spectra of the deposited films indicated negligible change in the bulk composition of the deposited films. The estimated diffusivities of water in the deposited fluorocarbon films were of the order of 10⁻¹⁰ cm²/sec, and films deposited from C₄F₈ monomer showed higher diffusivity as compared to films deposited from PFE monomer. The equilibrium moisture uptake is affected by the presence of polar groups, the F/C ratio, and the O/C ratio. The relatively high diffusivity of water in the fluorocarbon films is attributed to the lack of polar groups in the deposited films. Adsorption onto the surface followed by diffusion into the bulk is proposed as the mechanism for moisture absorption in the fluorocarbon films. Finally, the moisture uptake of the fluorocarbon and hydrofluorocarbon films is compared to that of a conventionally used microelectronic polymer, polyimide (PI 2611), in order to evaluate the effect of polar groups and fluorine content on diffusion and equilibrium moisture uptake.     

Flexible Polyarylene Ether Nitrile/BaTiO<Subscript>3</Subscript> Nanocomposites with High Energy Density for Film Capacitor Applications

Polyarylene ether nitrile (PEN)/barium titanate (BT) nanocomposite films were successfully prepared by a continuous ultrasonic dispersion fabrication process, and an optimized process route was established through the investigations. Scanning electron microscopy (SEM) showed that BT nanoparticles with diameters less than 100 nm were well dispersed in the polymer matrix. The PEN/BT nanocomposite films exhibited excellent dielectric properties, without sacrificing tensile strength or thermal stability, when compared with those of pristine polymer. Furthermore, the nanocomposite films were found to have good flexibility; they could be curled as easily as pure PEN films.     

Electrical and optical properties of ZnO/Si heterojunctions as a function of the Mg dopant content

Undoped and Mg-doped ZnO thin films prepared by a sol–gel process were deposited on p-Si and glass substrates via spin coating. The electrical and optical properties of the films were investigated. Atomic force microscopy images revealed that the ZnO films are formed from fibers consisting of nanoparticles. The electrical conductivity mechanism of the films was investigated. The I–V characteristics of Al/ZnO/p-Si samples showed rectification behavior with a rectification ratio that depended on the applied voltage and the Mg doping ratio. ZnO/p-Si heterojunction diodes exhibited non-ideal behavior with an ideality factor greater than unity that could be ascribed to the interfacial layer, interface states, and series resistance. The barrier height for undoped and Mg-doped ZnO/p-Si diodes was in the range 0.78–0.84 eV. The results demonstrate that the electrical properties of ZnO/p-Si heterojunction diodes are controlled by the Mg dopant content and suggest that the optical bandgap of these ZnO films can be tuned using the Mg level.     

磁控反应溅射直接生长绒面H化Ga掺杂ZnO-TCO薄膜及其特性研究

采用直流磁控溅射技术,在玻璃衬底上直接生长出了具有绒面结构的H化Ga掺杂ZnO(HGZO)薄膜。研究了H2流量对薄膜结构、表面形貌及光电特性的影响。实验表明,在溅射过程中引入H2明显改善HGZO薄膜电学性能,并且能够直接获得具有绒面结构的薄膜。在H2流量为2.0sccm时,所制备的HGZO薄膜具有特征尺寸约200nm的类金字塔状表面形貌,同时薄膜方阻为4.8Ω,电阻率达到8.77×10-4Ω.cm。H2的引入可以明显改善薄膜短波区域的光学透过,生长获得的HGZO薄膜可见光区域平均透过率优于85%,近红外区域波长到1 100nm时仍可达80%。为了进一步提高薄膜光散射能力和光学透过率,根据不同H2流量下HGZO薄膜性能的优点,提出了梯度H2技术生长HGZO薄膜;采用梯度H2工艺生长获得的HGZO薄膜长波区域透过率有了一定的提高,薄膜具有弹坑状表面形貌,并且其光散射能力有了明显提高。     

N/Al共掺ZnO透明导电薄膜的制备及光电性能研究

采用射频磁控溅射和退火处理方法在普通玻璃基底上制备了N、Al共掺的ZnO薄膜。利用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、四探针电阻测试仪和紫外-可见光光谱及X射线光电子能谱(XPS)等测试手段,分析了溅射功率对薄膜表面形貌结构及光电性能的影响。研究结果表明:不同溅射功率下所制备的薄膜均为具有c轴择优取向的六角纤锌矿结构,在可见光范围内,平均透过率都超过了85%;在溅射功率为140W条件下,N、Al共掺的ZnO薄膜显示出p型导电特性。     

Research on the piezoelectric response of cubic and hexagonal boron nitride films

Boron nitride (BN) films for high-frequency surface acoustic wave (SAW) devices are deposited on Ti/Al/Si(111) wafers by radio frequency (RF) magnetron sputtering. The structure of BN films is investigated by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) spectra, and the surface morphology and piezoelectric properties of BN films are characterized by atomic force microscopy (AFM). The results show that when the flow ratio of nitrogen and argon is 2:18, the cubic BN (c-BN) film is deposited with high purity and c-axis orientation, and when the flow ratio of nitrogen and argon is 4:20, the hexagonal BN (h-BN) film is deposited with high c-axis orientation. Both particles are uniform and compact, and the roughnesses are 1.5 nm and 2.29 nm, respectively. The h-BN films have better piezoelectric response and distribu- tion than the c-BN films.     

脉冲镀金在半导体激光器中的应用及工艺优化

为提高半导体激光器芯片的焊接成功率以及器件的性能寿命,采用脉冲电镀技术在半导体激光器芯片 P 面沉积了厚金层,详细研究了镀金液 pH 值和电流通断比对镀金层组织形貌、表面粗糙度、内应力、沉积均匀性以及粘附力的影响规律。结果表明,表面粗糙度随 pH 值的升高或通断比的提高而增大。沉积均匀性随 pH 的增大先降低后升高,而随通断比的增大而变差。pH 较大（＞10．0）或较小（＜8．5）时,镀金层粘附性均不理想。而通断比对镀金层的粘附性影响不大。不同条件下,金膜内应力均为张应力,大小为29～88 MPa。     

非晶氧化钛薄膜的电学特性研究

室温下,通过采用直流反应磁控溅射法在覆盖有氮化硅薄膜的单晶硅衬底上生长了厚度约为100nm的氧化钛薄膜。掠入射X射线衍射分析结果表明在室温下,不同氧分压下生长的氧化钛薄膜均具有非晶结构。分别采用场发射扫描电子显微镜、X射线光电子能谱对薄膜的表面和断面形貌以及薄膜的组分进行了分析和表征。对薄膜的电学特性测试发现非晶氧化钛薄膜在293～373K的温度范围内主要依靠热激发至扩展态中的电子导电。     

Novel Strategies for the Deposition of ?COOH Functionalized Conducting Copolymer Films and the Assembly of Inorganic Nanoparticles on Conducting Polymer Platforms

A method for the preparation of ? COOH functionalized conducting copolymer films; toward the ultimate goal of developing resistance‐based sensing platforms, is presented. The method involved vapor phase copolymerization of pyrrole with a monomer containing the ? COOH functionality, thiophene‐3‐acetic acid (TAA). This copolymerization strategy aided in avoiding the need to employ brittle poly(thiophene‐3‐acetic acid) (PTAA) films in sensing applications. In this strategy, variation in the gas phase feed ratio of pyrrole to TAA allowed for the variation of the composition of the copolymer film and further allowed for the variation of both the conductivity and the amount of ? COOH functionality in the films. Further, the effect of covalent attachment of silver on the conductivity of the copolymer films is performed and presented. This covalent attachment of silver served the dual purpose of verifying the presence of active ? COOH groups on the surface, and also allowed for the quantification of the change in conductivity as a result of such attachment. Use of the conjugated ring containing 4‐aminothiophenol as the linker material enhanced the conductivities of the films. In contrast, employing cysteamine to link silver nanoparticles to the copolymer films did not result in any enhancement in the conductivities. An enhancement in the conductivities, ranging from 2 to 1000 times, is observed on covalent attachment of silver nanoparticles to the copolymer films using 4‐aminothiophenol as the linker material. This increase depended on the amount of TAA in the films and increased with increasing concentrations of TAA in the films. These results clearly indicate the use of these copolymer films in resistance‐based sensing. Further, this covalent attachment could be used as a novel strategy to integrate other inorganic nanomaterials on conducting polymer platforms.     

Effect of processing parameter on structural,optical and electrical properties of photovoltaic chalcogenide nanostructured RF magnetron sputtered thin absorbing films

The aim of this work was to develop high quality of CuIn_1−xGa_xSe₂ thin absorbing films with x (Ga/In+Ga)<0.3 by sputtering without selenization process. CuIn_0.8Ga_0.2Se₂ (CIGS) thin absorbing films were deposited on soda lime glass substrate by RF magnetron sputtering using single quaternary chalcogenide (CIGS) target. The effect of substrate temperature, sputtering power & working pressure on structural, morphological, optical and electrical properties of deposited films were studied. CIGS thin films were characterised by X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM), Energy dispersive X-ray spectroscopy (EDAX), Atomic force microscopy (AFM), UV–vis–NIR spectroscopy and four probe methods. It was observed that microstructure, surface morphology, elemental composition, transmittance as well as conductivity of thin films were strongly dependent on deposition parameters. The optimum parameters for CIGS thin films were obtained at a power 100 W, pressure 5 mT and substrate temperature 500 °C. XRD revealed that thin film deposited at above said parameters was polycrystalline in nature with larger crystallite size (32 nm) and low dislocation density (0.97×10¹⁵ lines m⁻²). The deposited film also showed preferred orientation along (112) plane. The morphology of the film depicted by FE-SEM was compact and uniform without any micro cracks and pits. The deposited film exhibited good stoichiometry (Ga/In+Ga=0.19 and In/In+Ga=0.8) with desired Cu/In+Ga ratio (0.92), which is essential for high efficiency solar cells. Transmittance of deposited film was found to be very low (1.09%). The absorption coefficient of film was ~10⁵ cm⁻¹ for high energy photon. The band gap of CIGS thin film evaluated from transmission data was found to be 1.13 eV which is optimum for solar cell application. The electrical conductivity (7.87 Ω⁻¹ cm⁻¹) of deposited CIGS thin film at optimum parameters was also high enough for practical purpose.     

Properties of nanostructured Al doped ZnO thin films grown by spray pyrolysis technique

Aluminium doped zinc oxide thin films were deposited on glass substrate by using spray pyrolysis technique. The X-ray diffraction study of the films revealed that the both the undoped and Al doped ZnO thin films exhibits hexagonal wurtzite structure. The preferred orientation is (002) for undoped and up to 3 at % Al doping, further increase in the doping concentration to 5 at % changes the preferred orientation to (101) direction. The surface morphology of the films studied by scanning electron microscope, reveal marked changes on doping. Optical study indicates that both undoped and Al doped films are transparent in the visible region. The band gap of the films increased from 3.24 to 3.36 eV with increasing Al dopant concentration from 0 to 5 at % respectively. The Al doped films showed an increase in the conductivity by three orders of magnitude with increase in doping concentration. The maximum value of conductivity 106.3 S/cm is achieved for 3 at % Al doped films.     

Structural and electrical investigation of BLT films deposited at different times using electron beam evaporation technique

Thin films Bi4Ti3O12 (BLT) were deposited using electron beam evaporation on silicon substrate at several times, also on AlN/Si and SiO2/Si substrates. Thin films morphology and thickness were measured via scanning electron microscopy (SEM). The crystallography was studied using X-ray diffraction (XRD) technique for films which have a (0010) preferred orientation in all substrate types. The capacitance values were contingent on frequency value in C-V measurement. The ferroelectric characterization was investigated for BLT film deposited on isolator layer (SiO2 or AlN) for Al/Bi4Ti3O12/SiO2/Si devices. Memory effect value varied from 1 V to 3 V depending on the thin films isolator on substrate.     

Effect of Pb:S molar ratio in precursor solution on the properties of lead sulphide thin films by ultrasonic spray pyrolysis

In this work, PbS thin films were deposited onto glass substrate at 225 °C by spraying precursor solution prepared with different molar ratio of lead acetate and thiourea as a source of Pb²⁺ and S^2- respectively in order to investigate the effect of Pb:S molar ratio in the precursor solution on the physical properties of PbS thin films. Structural investigations carried out by X-ray diffractometer have shown that all films have fcc cubic structure and the average crystal size increased from 11 nm to 25 nm with the increasing the thiourea ratio in the precursor solution. In order to analyze the surface morphology of PbS thin films, AFM and SEM images were taken and elemental analysis of the films was performed by EDS. Optical transmittance and absorption spectra show that all deposited films have fairly low transmittance and high absorbance in the visible region. Additionally, it was determined that optical band gap of the deposited films were varied between 1.18 eV and 1.37 eV. As a consequence of electrical investigations, it was seen that all films have p-type conductivity and electrical resistivity decreased by increasing thiourea molar ratio in the precursor solution. All examinations have revealed that the molar ratio of lead acetate and thiourea has a significant effect on the physical properties of PbS thin films.     

Incorporation of Functionalized Palladium Nanoparticles within Ultrathin Nafion Films: A Nanostructured Composite for Electrolytic and Redox‐Mediated Hydrogen Evolution

A novel ultrathin Nafion‐palladium nanocomposite film is developed by incorporating positively charged Pd nanoparticles, stabilized with dimethylaminopyridine (DMAP), into Nafion Langmuir‐Schaefer (LS) films. The films show considerable activity for the redox‐catalyzed hydrogen‐evolution reaction, the rate of which scales with film thickness. The Nafion film can be deposited on both insulating (glass) and electrode (indium‐tin oxide) surfaces. The quantity of Pd nanoparticles immobilized can be controlled simply via the thickness of the Nafion film. The morphology of the films are investigated using AFM, which allows the number density of nanoparticles to be estimated for the thinnest (10 layers; 18 nm) films. Incorporation of nanoparticles is also determined with cyclic voltammetry and UV‐visible spectroscopy. The former method allows estimation of the electrochemically active surface area of Pd wired to the underlying electrode. A novel scanning electrochemical microscopy (SECM) approach is used to investigate the kinetics of the hydrogen evolution reaction (HER) catalyzed by Pd nanoparticles within the Nafion film, which allows the intrinsic activity to be determined. Single nanoparticle reactivities are extracted and are comparable to the activity of native nanoparticles on glass and to bulk Pd. It is found that neither Nafion encapsulation nor DMAP functionalization impair the electrocatalytic activity of these nanoparticles towards the HER. Nafion encapsulation thus provides a framework for the formation of interfaces, whose activity scales with film thickness. The creation of 3D materials opens up the possibility of carrying out redox‐mediated hydrogen evolution using solution species as the electron donor.     

Evaluation of an Nd doping effect on characteristic properties of tin oxide

In the present work, transparent and conductive Nd doped SnO₂ thin films were deposited via spray pyrolysis. Crystallographic, morphological, optical and electrical characterizations of SnO₂ were researched as a function of Nd doping. The XRD analysis indicated the films had tetragonal cassiterite tin oxide structure and (211) preferential direction for NdTO-0, NdTO-1, NdTO-2 and NdTO-3 samples changed to (110) plane for NdTO-4 and NdTO-5 samples. The crystalline size and strain analysis were made by using a Williamson–Hall method. The SEM micrographs showed that all films had homogenously scattered pyramidal and small densely nanoparticles. The optical analysis indicated optical band gap value of undoped film increased with 1 at% Nd doping and then it decreased with more Nd content. The Hall measurements indicated that the highest electrical conductivity was obtained for 2 at% Nd doping content.     

Zinc telluride films by photoenhanced metalorganic chemical vapor deposition

Polycrystalline films of zinc telluride (ZnTe) have been deposited on glass and conducting semiconductor coated glass substrates at 270°-350° C by photoenhanced metalorganic chemical vapor deposition (PECVD) using the reaction of dimethylzinc (DMZn) or diethylzinc (DEZn) and diisopropyltellurium (DIPTe) in hydrogen under atmospheric pressure. The deposited films are always ofp-type conductivity. Their properties are affected by the DMZn/DIPTe or DEZn/DIPTe molar ratio in the reaction mixture. The optimum DMZn/DIPTe ratio has been found to be approximately 0.9 on the basis of the open-circuit voltage of ZnTe/CdS heterojunctions and photoconductivity measurements. Without intentional doping, the deposited films are of high resistivity (>10⁷ ohm-cm) at room temperature, and the resistivity of these films has been controlled by using arsine as a dopant. The structural, optical, and electrical properties of ZnTe films have been characterized. Supported by the Solar Energy Institute under Subcontract XL-8-18091-1.