Electrical Conductivity Of Films Research Articles

Development of poly (methyl methacrylate)-supported transfer technique of single-wall carbon nanotube conductive films for flexible devices

We propose a transfer technique of single-wall carbon nanotube (SWCNT) films to be applied to a wide variety of flexible electronic devices. SWCNT films were first heat-treated in advance to remove solvents and dispersants in the films on high heat-resistant Cu substrates and were then poly (methyl methacrylate)-supported transferred onto low heat-resistant polyethylene terephthalate and paper substrates. We characterized the flexibility and electrical properties of the films transferred by this technique. The transferred films showed high flexibility and high electrical conductivity (8.4 × 104 ∼ 1.1 × 105 S/m). X-ray photoelectron spectroscopy measurements revealed that the transferred films were free from Fe residues. Although a slight amount of the Cu residues existed, it was found that the residues did not contributed to the electrical conduction. By using this technique, we enabled to fabricate highly flexible and highly electrical conductive SWCNT films on flexible substrates with low heat resistance, which provide further potential for the application of these films to flexible electronic devices.

Low-Thermal-Budget Photonic Sintering of Hybrid Pastes Containing Submicron/Nano CuO/Cu2O Particles.

Copper oxide particles of various sizes and constituent phases were used to form conductive circuits by means of photonic sintering. With the assistance of extremely low-energy-density xenon flash pulses (1.34 J/cm2), a mixture of nano/submicron copper oxide particles can be reduced in several seconds to form electrical conductive copper films or circuits exhibiting an average thickness of 6 μm without damaging the underlying polymeric substrate, which is quite unique compared to commercial nano-CuO inks whose sintered structure is usually 1 μm or less. A mixture of submicron/nano copper oxide particles with a weight ratio of 3:1 and increasing the fraction of Cu2O in the copper oxide both decrease the electrical resistivity of the reduced copper. Adding copper formate further improved the continuity of interconnects and, thereby, the electrical conductance. Exposure to three-pulse low-energy-density flashes yields an electrical resistivity of 64.6 μΩ·cm. This study not only shed the possibility to use heat-vulnerate polymers as substrate materials benefiting from extremely low-energy light sources, but also achieved photonic-sintered thick copper films through the adoption of submicron copper oxide particles.

Development of novel single-source precursor of tin for deposition of tin oxide thin films for various applications

Novel single-source organometallic precursor, Triethanolamine Tin (II) (Sn-TEA), was synthesized by the reaction of SnCl2 and triethanolamine in the presence of Sodium acetate. TGA, FTIR, 1H characterize the Sn-TEA precursor, and 13C NMR was done to confirm its thermal stability and predict its molecular structure. The 1H and 13C NMR showed an organometallic molecule as TEA and acetate form a coordination sphere around the Sn atom in a stable structure. The TGA showed two thermal decomposition steps at ~206.14oC and ~750oC and residue at 800 °C. The precursor was pyrolyzed at 400oC, and the residual powder was characterized by FTIR, which indicated the formation of Tin Oxide. The precursr was then used to deposit SnO2 films by microwave-assisted solvothermal process on glass substrates. The films were characterized with XRD, FESEM and tested for conductivity. XRD confirmed the formation of SnO2 of the cubic lattice. The precursor concentration and microwave irradiation time on the film morphology, compositional analysis, and electrical conductivity were studied thoroughly. Sn-TEA complex proved to be a potential single-source precursor for SnO2 production, and it can be applied to develop highly pure/doped SnO2 films for gas sensing applications in a cost-effective manner

Physical and Electrical Studies of High Molecular Weight Poly (Methyl Methacrylate) Based Solid Polymer Electrolytes

In this work, the film contained a mixture of PMMA, salt, and plasticizers are studied. PMMA as a host polymer, ammonium trifluoromethane sulphonate or ammonium triflate (NH4CF3SO3) as a doping salt and ethylene carbonate (EC) as a plasticizer is used in this present study. PMMA salt complexes system and plasticized PMMA salt complexes system are prepared by solution cast technique at room temperature. FTIR is used to study the interaction between polymer and salt, and between polymer–salt and plasticizer. The carbonyl group C=O asymmetric stretching mode observed at 1721 cm-1 is broadened and shifted to lower wavenumber when ammonium triflate was added into PMMA. The broadening, shifting and reduction in wavenumbers of FTIR spectra show that the complexation has occurred between the polymer and salt. EIS is performed to measure the electrical conductivity of the polymer–salt system prepared at ambient temperature. The electrical conductivity of film containing 1.0 g of PMMA–35 wt% NH4CF3SO3–16 wt% EC exhibit the highest electrical conductivity with the value of 2.461 x 10-4 S/cm2. XRD is carried out to study the pattern of pure PMMA, PMMA–NH4CF3SO3 and PMMA–NH4CF3SO3–EC. The XRD analysis shows the addition of plasticizer to the polymer–salt system increase the amorphousness of the polymer electrolytes hence increases in conductivity.

Etchless Fabrication of High‐Quality Refractory Titanium Nitride Nanostructures

Nanosphere lithography has emerged as an efficient route to produce plasmonic nanostructures. Herein, the processes of nanosphere lithography and reactive magnetron sputtering that seem incompatible for a variety of reasons are reviewed and explained. However, understanding the physical obstacles of this combination enables us to identify a window of process parameters that make the deposition of well‐defined trigonal nanoislands of titanium nitride (TiN) feasible. TiN is used as a case study because it is a very good representative of refractory conductive nitrides, such as ZrN, HfN, NbN, and TaN. A UV ozone step is used to confine the triple‐junction vias of the polystyrene mask, and the reactive magnetron sputtering parameters are fine‐tuned to increase the directionality of deposited species, in particular the substrate‐to‐target distance is maximized to improve geometrical directionality, and a negative bias voltage is used to guide the ionic species deep into the vias. The proposed process produces well‐defined TiN nanoislands with low concentration of point defects that have similar structure with continuous films of high electrical conductivity and plasmonic performance.

Tailoring the physical properties of titania thin films with post deposition air and vacuum annealing

The present article carefully reports the influence of post deposition annealing on photophysical properties of titania (TiO 2 ) thin films, which are developed employing the electron-beam deposition technique. The pristine films are annealed at 100 °C, 200 °C, 300 °C in air and vacuum conditions followed by the investigation of photophysical properties employing several characterization tools viz. XRD, SEM, AFM, EDS, PL, UV Vis. spectrophotometer and source meter. The films showed amorphous nature, whereas Ti and O peaks in the EDS pattern are evident for TiO 2 films deposition. The increase in annealing temperature resulted into an increment in the transmittance (except for 100 °C) of air annealed films, whereas transmittance is decreased for vacuum annealed films. The obtained higher transmittance is suitable for TiO 2 thin films to implicate as buffer layer for solar cell devices where the band gap is observed in a range of 3.06–3.13 eV for air annealed and 2.57–3.05 eV for vacuum annealed films. The electrical conductance of films is enhanced up to 200 °C during annealing possibly due to the removal of traps present in titania thin films. AFM analysis of air annealed films demonstrates a decrement in surface roughness and grain size. Room temperature photoluminescence spectra exhibited strong peaks at 400 nm and 621 nm corresponding to the band edge and Ti 2+ , Ti 3+ , Ti 4+ surface state emissions, respectively. The higher transmittance, lower surface roughness, and ohmic nature of 300 °C air annealed films might attract kind attention for photoanode and optical window or buffer layer applications in dye-sensitized and Cd-based solar cells and charge transport layers in organic and perovskite solar cells. • An impact of air and vacuum annealing on properties of titania films is studied. • The structural analysis reveals the amorphous nature of pristine and annealed films. • Higher transmittance is observed for 300 °C air annealed titania films. • All the titania films showed conspicuous ohmic nature along with lower roughness. • The titania films air annealed at 300 °C may be applied as window or buffer layer.

High Electrochemical Performance Silicon Thin-Film Free-Standing Electrodes Based on Buckypaper for Flexible Lithium-Ion Batteries.

Recently, applications for lithium-ion batteries (LIBs) have expanded to include electric vehicles and electric energy storage systems, extending beyond power sources for portable electronic devices. The power sources of these flexible electronic devices require the creation of thin, light, and flexible power supply devices such as flexile electrolytes/insulators, electrode materials, current collectors, and batteries that play an important role in packaging. Demand will require the progress of modern electrode materials with high capacity, rate capability, cycle stability, electrical conductivity, and mechanical flexibility for the time to come. The integration of high electrical conductivity and flexible buckypaper (oxidized Multi-walled carbon nanotubes (MWCNTs) film) and high theoretical capacity silicon materials are effective for obtaining superior high-energy-density and flexible electrode materials. Therefore, this study focuses on improving the high-capacity, capability-cycling stability of the thin-film Si buckypaper free-standing electrodes for lightweight and flexible energy-supply devices. First, buckypaper (oxidized MWCNTs) was prepared by assembling a free stand-alone electrode, and electrical conductivity tests confirmed that the buckypaper has sufficient electrical conductivity (10−4(S m−1) in LIBs) to operate simultaneously with a current collector. Subsequently, silicon was deposited on the buckypaper via magnetron sputtering. Next, the thin-film Si buckypaper freestanding electrodes were heat-treated at 600 °C in a vacuum, which improved their electrochemical performance significantly. Electrochemical results demonstrated that the electrode capacity can be increased by 27/26 and 95/93 μAh in unheated and heated buckypaper current collectors, respectively. The measured discharge/charge capacities of the USi_HBP electrode were 108/106 μAh after 100 cycles, corresponding to a Coulombic efficiency of 98.1%, whereas the HSi_HBP electrode indicated a discharge/charge capacity of 193/192 μAh at the 100th cycle, corresponding to a capacity retention of 99.5%. In particular, the HSi_HBP electrode can decrease the capacity by less than 1.5% compared with the value of the first cycle after 100 cycles, demonstrating excellent electrochemical stability.

Liquid antimony pentachloride as oxidant for robust oxidative chemical vapor deposition of poly(3,4-ethylenedioxythiophene) films

The oxidative chemical vapor deposition (oCVD) process is investigated to produce poly (3,4-ethylenedioxythiophene) (PEDOT) thin films on 10 cm diameter Si wafers, involving the SbCl5 liquid oxidant. Process/structure/properties correlations are thoroughly studied, including the influence of the SbCl5/EDOT ratio, substrate temperature (Tsub), total pressure and deposition duration, on the thickness, composition, morphology, spatial uniformity of the films, and on their electrical conductivity and optical transmittance. The electrical conductivity of the films increases by decreasing the oxidant/EDOT ratio and by increasing the substrate temperature. Such increase of substrate temperature results in the decrease of the deposited mass and thickness. Films uniformity and electrical conductivity are improved by decreasing the total pressure. Operating at 75 Pa results in films of equal and uniform thickness deposited on substrates located all over the deposition chamber, proving the potential of the PEDOT-SbCl5 oCVD process to be scaled up over larger surfaces. The absence of post deposition liquid rinsing allows developing a full dry process, which is of interest to coat sensitive substrates and can thus be implemented for the processing of devices requiring durable, transparent, conductive PEDOT thin films, in particular in the field of optoelectronics.

Comparative study on the effect of annealing temperature on sol–gel-derived nickel oxide thin film as hole transport layers for inverted perovskite solar cells

Sol–gel-processed nickel oxide (NiOx) is a promising hole transport layer (HTL) for inverted perovskite solar cells (PSCs) because of its excellent carrier transport properties, low costs, and high stability. Annealing temperature plays a vital role in the sol–gel process as different temperatures can alter the physicochemical properties of the materials. In the present study, we investigated the effect of annealing temperature on NiOx thin films prepared through sol–gel processing from predominantly used precursors: (1) nickel acetate tetrahydrate (Ni-ac) and (2) nickel acetylacetonate (Ni-acac). X-ray diffraction and X-ray photoelectron spectroscopy results revealed that the crystallinity and stoichiometry of both NiOx thin films improve with an increase in annealing temperature, indicating the formation of a standard Ni–O octahedral in a cubic rock NiO structure. Higher annealing temperatures have been shown to improve film optical transparency and electrical conductivity due to the complete decomposition of precursors and improved crystallinity. The device characterization has shown both films can work as an effective HTL for PSCs and showed the best device performance for films annealed at 400 °C. It is believed that this study can provide a basic understanding and strategy for developing highly efficient NiOx HTL in PSCs.

Synthesis and Fabrication of Fluorescent Green OLEDs Based on PEDOT:PSS/Silver Nanowire Hybrid-Composite Anode and Their Performance

Transparent conducting films have attracted increasing attention for their usefulness in optoelectronic devices, such as solar cells, liquid crystal display, and LEDs. Silver nanowires (AgNWs) with a length of 20 μm and a diameter of 70 nm was synthesized using polyol process. The optimized concentration of AgNWs is 0.5 mg of Ag NWs in 1 ml of PEDOT:PSS and it was used to fabricate PEDOT:PSS/AgNWs hybrid-composite TCF electrode, resulting in 88% transmittance and good electrical conductive (30 Ω sq−1) thin film. Two types of green fluorescent OLEDs were fabricated: those made with conventional ITO anode and the anode based on PEDOT:PSS/Ag NWs hybrid-composite. The observed maximum luminous intensity was increased by 27% in OLED fabricated PEDOT:PSS/AgNWs hybrid-composite TCF electrode, compared to the conventional ITO. At a wavelength of 530 nm, the maximum luminous intensities for green fluorescent OLEDs fabricated on PEDOT:PSS/AgNWs hybrid-composite TCF and ITO anode were 1610 counts per second and 1260 counts per second, respectively. The observed maximum current density increased by 28% as compared to the conventional ITO. The observed current densities were 370 mA cm−2 for OLEDs fabricated on PEDOT:PSS/AgNWs hybrid-composite TCF-based anode, and 293 mA cm−2 for conventional ITO anode. The proposed hybrid-composite electrode is a suitable material to replace conventional ITO.

Electrical conductivity of a thin film in the case of an arbitrarily oriented ellipsoidal isoenergetic surface of a conductor

The static electrical conductivity of a thin conducting film is calculated using the kinetic approach. The model of diffuse boundary conditions is used as boundary conditions for the charge carrier distribution function. The isoenergetic surface of the conducting film material is an ellipsoid of rotation that is arbitrarily oriented in the pulse space. The volume of the conductor is dominated by scattering on impurity atoms and on dislocations of electrons (holes). The electrical conductivity of the film is analyzed depending on the angles that determine the direction of the ellipsoid axis of rotation, and a comparison with the results for the case of a macroscopic sample is presented. A comparison is made with experimental data for the electrical conductivity of Bi and Si thin films.

Traps energy distribution in Kapton HN polyimide films through surface potential decay model under humidity conditions

In this paper, an experimental study and analysis of the effects of environmental relative humidity (RH %) on the transport mechanisms of electrical charges in 50 μm thick Kapton HN polyimide (PI) films have been presented. The evolution of the surface potential decay with time after negative corona charge deposition have been investigated and analyzed by examining the tdV/dt characteristics to straightly obtain information about trap energy distribution in PI films for different relative humidity levels (35, 50, 70 and 90%). The calculating method of trap energy distribution is based on the double exponential fitting analysis of surface potential decay measurements. Two peaks were observed in the trap charge density distribution curve with trap levels, which is agreed with the presence of the shallow and deep traps. The results indicate that for different charging voltage levels, the surface potential decays faster in humid air (RH = 90%) than in relatively dry ones (RH = 35%). The recorded corona charging current confirms the interpretation of surface potential decay measurements. In addition, the density and depths of both shallow and deep traps change with charging voltage and relative humidity levels. Both shallow and deep trap distribution moves towards lower energy levels, indicating an increase in the film's electrical conductivity.

Controlling pore structure and conductivity in graphene nanosheet films through partial thermal exfoliation

Thermal exfoliation is an efficient and scalable method for the production of graphene nanosheets or nanoplatelets, which are typically re-assembled or blended to form new macroscopic “graphene-based materials”. Thermal exfoliation can be applied to these macroscopic graphene-based materials after casting to create internal porosity, but this process variant has not been widely studied, and can easily lead to destruction of the physical form of the original cast body. Here we explore how the partial thermal exfoliation of graphene oxide (GO) multilayer nanosheet films can be used to control pore structure and electrical conductivity of planar, textured, and confined GO films. The GO films are shown to exfoliate explosively when the instrument-set heating rates are 100 K/min and above leading to complete destruction of the film geometry. Textured films with engineered micro-wrinkling and crumpling show similar thermal behavior to planar films. Here, we also demonstrate a novel method to produce fairly large size intact rGO films of high electrical conductivity and microporosity based on confinement. Sandwiching GO precursor films between inert plates during partial exfoliation at 250 °C produces high conductivity and porosity material in the form of a flexible film that preserves the macroscopic structure of the original cast body.

Mechanism of the Electrical Conductivity of a Film Consisting of Dielectric Nanoparticles with Surface Donor Centers

Restrictions imposed on the characteristics of a semiconductor by the condition that ohmic losses in it are zero are established using equations of the thermodynamics of irreversible processes. A consequence of the negative value of the static permittivity of a semiconductor consisting of nanogranules or microgranules is that the intensity Е of the external electric field in its volume is zero. Because of the action of thermodynamic forces, the ohmic losses in the semiconductor are zero (jЕ = 0, where Е = 0) or nonzero depending on the direction of the constant electric current in a closed circuit. Theoretical explanation of the experimental data for the electrical conductivity of films consisting of Al2O3 and/ or NiO nanoparticles with chemisorbed hydrogen atoms is obtained.

Impedance analysis of oil conductivity and pixel non-uniformity in electrowetting displays

The electrical conductivity of the oil film is a key property of electrowetting displays (EWD) and its evolution probably correlates to the device lifetime. In this report, we fabricate an EWD device and measure its electrical impedance spectrum. The experimental results inform on the electrical resistivity of the oil film, as revealed by comparison with numerical simulations based on an equivalent electrical circuit model. Wide distribution in the oil-film resistance has to be incorporated into the model to reproduce the measured impedance spectrum precisely, which supports previous work indicative of pixel-to-pixel variation in the oil film electrical conductivity. Our work demonstrates that one can conveniently characterize the oil film resistance and its non-uniformity using electrical impedance spectroscopy.

An out of the box vision over oxidative chemical vapor deposition of PEDOT involving sublimed iron trichloride

Oxidative chemical vapor deposition (oCVD) is an efficient technique to produce highly conductive films of Poly (3,4-ethylenedioxythiophene) (PEDOT). Despite numerous studies on the oCVD of PEDOT films, there is limited information on the stability of the sublimation of solid oxidants and on their impact on the polymerization reactions. In this work, we use an in situ Quartz Crystal Microbalance to monitor film formation over time. Through a series of deposition experiments between 20 °C and 100 °C and for FeCl3/EDOT molar gas ratios between 17.3 and 75.3, we analyze in detail the correlations between process parameters and film morphology, composition, surface topography and electrical conductivity on 10 cm silicon wafers. By using multiple substrates at different positions into the reactor, we demonstrate that the formation of PEDOT occurs uniformly through purely surface reactions, following step growth polymerization principles. These results pave the way towards highly conductive oCVD PEDOT films processed from convenient solid oxidants.

Effect of Al concentration on optical parameters of ZnO thin film derived by Sol-Gel dip coating technique

Pure and Aluminum doped zinc oxide (Al:ZnO) film samples were deposited by the sol–gel dip-coating technique for understand influence of Al concentration on the films crystallization, electrical conductivity and optical transparency. Surface morphology of the film with hexagonal wurtize crystalline structure and high c-axis orientation (in XRD analysis) displayed nanospherical particals (in SEM images). The surface roughness and average grain size increased with Al amount rise in the Al/Zn ratio. The film displayed high transparency (~90%) between 300 and 800 nm for pure and 1, 3 at.% Al concentration levels. The energy band gap, refractive index, and extinction coefficient were affected slightly due to the increasing Al concentration and optical parameters attain gently a maximum value at 3 at.% Al content.

Al doping for bipolarity induction in transparent conducting CuInO2 and its application in diode fabrication

Al doping is used in transparent conducting CuInO2 (CIO:Al) thin films for producing bipolar electrical conductivity. The doped thin films of electrical conductivity ~2 to 4 S/cm and mobility 100 to 101 V/cm2 are deposited by oxygen plasma assisted reactive evaporation technique. The change in conductivity from n-to p-type with the variation in doping atomic percentage is confirmed by multiple techniques like hot probe, hall and Seebeck measurements. The as deposited amorphous films are found to assume 3R poly type delafossite structure after post air annealing at 673 K. The suitability of the doped films in transparent device fabrication is verified by construction and characterization of a diode with configuration FTO/n-CIO:Sn/p-CIO:Al/Ag.

Corrosion behavior of lithium silicate-based Zn-5.5Al-4.5Mg-0.3Ce coating

The effects of Ce on the microstructure of Zn-5.5Al-4.5Mg alloy and the corrosion mechanism of Zn-5.5Al-4.5Mg-0.3Ce alloy and its coatings were investigated in this research. The results show that the structure of Zn-5.5Al-4.5Mg-0.3Ce alloy is composed of hcp-Zn, fcc-Al and ternary eutectic structure (Zn/Al/MgZn2/Mg2Zn11), without dendritic tissue and MgZn2. The salt spray corrosion performance of Zn-5.5Al-4.5Mg-0.5CMC-2C coating was significantly better than that of Zn-5.5Al-4.5Mg-0.3Ce coating and Zn-5.5Al-4.5Mg-0.5CMC coating. The corrosion current density of Zn-5.5Al-4.5Mg-0.5CMC-2C coating was 3.217 μA cm−2, which was significantly lower than 3.96 μA cm−2 of Zn-5.5Al-4.5Mg-0.3Ce alloy and 5.879 μA cm−2 of Zn-5.5Al-4.5Mg alloy. Sodium carboxymethylcellulose and graphene improve the film formation and electrical conductivity of water-based lithium silicate resin. During corrosion of Zn-5.5Al-4.5Mg-0.3 Ce series alloy and coatings, Zn and Mg2Zn11 dissolved preferentially to form corrosion products of Zn5(OH)6(CO3)2 and Zn5(OH)8Cl2·H2O. Mg6Al2(OH)16CO3·4H2O and Zn4Al2(OH)12CO3·3H2O bimetallic hydroxide colloidal membranes were formed, which attached and wrapped on the surface of early corrosion products. Mg6Al2(OH)16CO3·4H2O and Zn4Al2(OH)12CO3·3H2O, preventing the dissolution of soluble corrosion products, improved the corrosion resistance of Zn-5.5Al-4.5Mg-0.3Ce alloy.

Polyvinylpyrrolidone with ammonium iodide and 1-hexyl-3-methylimidazolium iodide ionic liquid-doped solid polymer electrolyte for efficient dye sensitized solar cell

Polymer electrolytes were prepared by doping polyvinylpyrrolidone and ammonium iodide ion with an ionic liquid (IL) 1-hexyl-3-methylimidazolium iodide. Polymer electrolytes were prepared by solution cast technique. Ionic conductivity was improved by the addition of IL which is studied using complex impedance spectroscopy by evaluating ionic conductivity. Using maximum electrical conductivity film, laboratory-scale dye-sensitized solar cell has been fabricated which shows stable performance.