Electrical Conductivity Of Films Research Articles

Ultrahigh Electrical Conductivity in p-Type CsPbI2Br Perovskite Thin Films by Modulation Doping.

The widespread adoption of halide perovskites for application in thermoelectric devices, DC power generators, and lasers is hindered by their low charge carrier concentration. In particular, increasing their charge carrier concentration is considered the main challenge to serve as a promising room-temperature thermoelectric material. Efforts have been devoted to enhancing the charge carrier concentration by doping and composition engineering. However, the coupling between charge carrier concentration and mobility, along with the poor stability of these materials, impedes their development for thermoelectric applications. Herein, we demonstrate the successful increase in the charge carrier concentration of CsPbI2Br by forming a heterojunction structure with Cu2S via a facile spin-coating method. The excellent band alignment between two materials combined with a charge-transfer mechanism realizes the modulation doping, resulting in 8 orders of magnitude increase in carrier concentration from 1012 to 1020 cm-3 without detrimental effect on the carrier mobility of CsPbI2Br. The thermoelectric power factor of the heterostructured CsPbI2Br reached 6.6 μW/m·K2, which is 330 times higher than that of pristine CsPbI2Br. Furthermore, these films showed higher humidity stability than the control films. This study offers a promising avenue for increasing the charge carrier concentration of halide perovskites, thereby enhancing their potential for various applications.

Flexible, Stable, and Efficient Counter Electrode for Quantum-Dot-Sensitized Solar Cells Based on Carbon Nanotube Films.

With the rapid development in information, communication, energy, medical care, and other fields, the demand for light, strong, flexible, and stable materials continues to grow. Carbon nanotube (CNT) films possess outstanding properties, such as flexibility, good tensile properties, low density, and high electrical conductivity, making them promising materials for a wide range of applications. This paper reports an effective strategy that combines stretching treatment, laser etching, and electron beam deposition to fabricate an iron-deposited CNT film, which can serve as a counter electrode (CE) of quantum-dot-sensitized solar cells. The study also investigates the influences of processing parameters, such as stretching ratio and iron-depositing thickness on the film's stacking structure, electrical conductivity, and catalytic activity. Under optimized stretching ratios and depositing thicknesses, the catalytic activity of the reacted deposited layer and the high electrical conductivity of the flexible film basis can be fully utilized, allowing the photoelectric conversion efficiency (PCE) of the solar cells to reach approximately 4.58%. Additionally, the CE exhibits flexibility, light transmission, and good stability, with its primary properties remaining above 97% after nearly 50 days. Thus, this research provides innovative material options and development strategies for the development of electrode materials.

Surface treatment of TaN for sub-2 nm, smooth, and conducting atomic layer deposition Ru films

Atomic layer deposition (ALD) of ruthenium (Ru) is being investigated for next generation interconnects and conducting liners for copper metallization. However, integration of ALD Ru with diffusion barrier refractory metal nitrides, such as tantalum nitride (TaN), continues to be a challenge due to its slow nucleation rates. Here, we demonstrate that an ultraviolet-ozone (UV-O3) pretreatment of TaN leads to an oxidized surface that favorably alters the deposition characteristics of ALD Ru from islandlike to layer-by-layer growth. The film morphology and properties are evaluated via spectroscopic ellipsometry, atomic force microscopy, electrical sheet resistance measurements, and thermoreflectance. We report a 1.83 nm continuous Ru film with a roughness of 0.19 nm and a sheet resistance of 10.8 KΩ/□. The interface chemistry between TaN and Ru is studied by x-ray photoelectron spectroscopy. It is shown that UV-O3 pretreatment, while oxidizing TaN, enhances Ru film nucleation and limits further oxidation of the underlying TaN during ALD. An oxygen “gettering” mechanism by TaN is proposed to explain reduced oxygen content in the Ru film and higher electrical conductivity compared to Ru deposited on native-TaN. This work provides a simple and effective approach using UV-O3 pretreatment for obtaining sub-2 nm, smooth, and conducting Ru films on TaN surfaces.

Electrostatic-driven self-assembled chitin nanocrystals (ChNCs)/MXene films for triboelectric nanogenerator

With the rapid development of smart wearable electronics, self-powered devices are urgently needed to overcome the limitations of conventional power sources. The single electrode triboelectric nanogenerator (TENG) attracts much attention owing to its simple fabrication, carrying convenience, and easy use as a power source for wearable electronic devices. Herein, a flexible, responsive, and multifunctional single electrode TENG based on renewable chitin nanocrystals (ChNCs) and MXene composite film (CM-TENG) is developed. ChNCs act as interfacial adhesives to facilitate the assembly of the MXene nanosheets, which significantly improves the composite film's mechanical properties and electrical conductivity. Positively charged ChNCs neutralize the negative charges of MXene nanosheet surfaces, enabling the composite film to rapidly transfer charges during the electrostatic induction process. The output performance of the CM-TENG can achieve 99.5 mW m−2 power density so it can be utilized for self-powered strain and tactile sensors. This work presents a new strategy for constructing stable and flexible power sources and self-powered sensors via electrostatic-driven self-assembled of ChNCs and MXene, which shows promising application in low frequency mechanical energy harvesting and self-powered wearable electronics.

The effects of humidity on the electrical properties and carrier mobility of semiconducting polymers anion-exchange doped with hygroscopic salts

To improve their electrical conductivity for various applications, semiconducting polymer films are often chemically doped to increase their equilibrium charge carrier density. Recently, a novel doping method involving anion exchange has provided control over the identity of the counterions that reside in such films, leading to increased stability under ambient conditions. In this work, however, we show that by ion-exchanging 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane-doped poly(3-hexylthiophene-2,5-diyl) films with hygroscopic salts like bis(trifluoromethane)sulfonimide lithium or LiPF6, the doped film's electrical conductivity drops significantly when exposed to ambient humidity. The change in electrical conductivity depends directly on the degree of hygroscopicity of the counterion and can be over 50% with relatively modest changes in relative humidity (RH), and up to a factor of four between ambient and completely dry conditions. The film's humidity response is entirely reversible when adsorbed water is removed, potentially allowing the doped semiconducting polymer films to function as humidity sensors. Hall effect measurements show that the cause of the drop in conductivity with increasing RH is due to a decrease in carrier mobility and not due to de-doping. Our results emphasize that it is important to control the sample environment when making electrical measurements on anion-exchange doped semiconducting polymer films.

Stable Ultra-thin Silver Films Grown by Soft Ion Beam-Enhanced Sputtering with an Aluminum Cap Layer.

Ultra-thin silver films are susceptible to ambient environments and form grayish layers in the silver mirroring process. The poor wettability together with the high diffusivity of surface atoms in the presence of oxygen accounts for the thermal instability of ultra-thin silver films in the air and at elevated temperatures. This work demonstrates an atomic-scale aluminum cap layer on the silver to enhance the thermal and environmental stabilities of ultra-thin silver films deposited by sputtering with the assistance of a soft ion beam reported in our previous work. The resulted film consists of an ion-beam-treated seed silver layer of ∼1 nm nominal thickness, a subsequent silver layer of ∼6 nm thickness produced by sputtering alone, and an aluminum cap layer of ∼0.2 nm nominal thickness. Although the aluminum cap is only one to two atomic layers and likely non-continuous, it significantly improved the thermal and ambient environmental stability of the ultra-thin silver films (∼7 nm thick) without affecting the film's optical and electrical properties. The improved environmental stability is attributed to the cathodic protection mechanism and reduced diffusivity of surface atoms. The improved thermal stability is attributed to the reduced mobility of surface atoms in the presence of aluminum atoms. Thermal treatment of the duplex film also improves the film's electrical conductivity and optical transmittance by enhancing its crystallinity. The annealed aluminum/silver duplex structure has exhibited the lowest electric resistivity among the reported ultra-thin silver films and high optical transmittance similar to the simulated theoretical results.

Step-by-Step Guide for Synthesis and Delamination of Ti3 C2 Tx MXene.

To advance the MXene field, it is crucial to optimize each step of the synthesis process and create a detailed, systematic guide for synthesizing high-quality MXene that can be consistently reproduced. In this study, a detailed guide is provided for an optimized synthesis of titanium carbide (Ti3 C2 Tx ) MXene using a mixture of hydrofluoric and hydrochloric acids for the selective etching of the stoichimetric-Ti3 AlC2 MAX phase and delamination of the etched multilayered Ti3 C2 Tx MXene using lithium chloride at 65 °C for 1 h with argon bubbling. The effect of different synthesis variables is investigated, including the stoichiometry of the mixed powders to synthesize Ti3 AlC2 , pre-etch impurity removal conditions, selective etching, storage, and drying of MXene multilayer powder, and the subsequent delamination conditions. The synthesis yield and the MXene film electrical conductivity are used as the two parameters to evaluate the MXene quality. Also the MXenes are characterized with scanning electron microscopy, x-ray diffraction, atomic force microscopy, and ellipsometry. The Ti3 C2 Tx film made via the optimized method shows electrical conductivity as high as ≈21,000 S/cm with a synthesis yield of up to 38 %. A detailed protocol is also provided for the Ti3 C2 Tx MXene synthesis as the supporting information for this study.

Anti-High-Power Microwave RFID Tag Based on Highly Thermal Conductive Graphene Films.

In this paper, a radio frequency identification (RFID) tag is designed and fabricated based on highly electrical and thermal conductive graphene films. The tag operates in the ultrahigh-frequency (UHF) band, which is suitable for high-power microwave environments of at least 800 W. We designed the protection structure to avoid charge accumulation at the antenna's critical positions. In the initial state, the read range of the anti-high-power microwave graphene film tag (AMGFT) is 10.43 m at 915 MHz. During the microwave heating experiment, the aluminum tag causes a visible electric spark phenomenon, which ablates the aluminum tag and its attachment, resulting in tag failure and serious safety issues. In contrast, the AMGFT is intact, with its entire read range curve growing and returning to its initial position as its temperature steadily decreases back to room temperature. In addition, the proposed dual-frequency tag further confirms the anti-high-power microwave performance of graphene film tags and provides a multi-scenario interactive application.

Ti3C2Tx MXene/polyimide composites film with excellent mechanical properties and electromagnetic interference shielding properties

With the development of electronic products to miniaturization and high frequency, high-performance flexible electromagnetic interference (EMI) shielding materials are urgently needed to deal with electromagnetic pollution. Two-dimensional transition metal carbide/polyimide (Ti3C2Tx MXene/PI) films were synthesized by in situ polymerization and a simple scratch method in this paper. The Ti3C2Tx MXene nanosheets give the films good EMI shielding effectiveness (SE) and electrical conductivity. Specifically, the film with a thickness of 0.11 mm (Ti3C2Tx content of 30 wt%) exhibits an EMI SE of 34.73 dB and a specific EMI SE (SE/thickness) of 315.73 dB/mm in the frequency range of 8.2–12.4 GHz (X-band). In addition, the films have a tensile strength of 67.58 MPa, and a high decomposition temperature of 510 ℃ in N2 atmosphere. Therefore, we believe that the prepared Ti3C2Tx/PI films with good comprehensive performance have enormous potential in the field of lightweight and flexible EMI shielding materials.

Gram-scale polymer-based thermoelectric module for charging Li-ion batteries

Organic thermoelectric devices are promising for charging Li-ion batteries in state-of-art sensors and communication devices. Herein, we report the design and fabrication of a gram-scale polymer-based thermoelectric module prepared by lamination of ultrathin half-dried poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) films with Ni foils. The hot pressing of a half-dried PEDOT/PSS film increases the film electrical conductivity and decreases its contact resistance. Such devices exhibit a power density of 72 μW/cm2 at 100 °C under natural cooling conditions in the absence of a heat sink. A 5 g device is capable of fully charging a commercial Li-ion battery (Nichicon SLB03070LR35) within 2 days. The manufactured organic thermoelectric device can be used instead of a CR2032 coin cell to power commercial sensors of acceleration, geomagnetism, temperature, humidity, atmospheric pressure, and illuminance. The manufactured devices exhibit excellent stability for over 2 months under continuous operation conditions. This work highlights the potential of organic thermoelectric devices for energy harvesting.

A simple doping strategy to improve PEDOT:PSS charge extraction capability in polymer solar cells

Black Phosphorus (BP) has shown great potential in optoelectronic devices due to its remarkable semiconductor properties. Herein, liquid-exfoliated BP nanosheets is doped into poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) to form a hybrid hole transport layers (HTLs). The incorporation of BP nanosheets in PEDOT:PSS dramatically changes the nanostructure and electrical conductivity of film. The BP doped PEDOT:PSS HTLs possess excellent charge selectivity and transport capability, which are proved in non-fullerene and fullerene blend system based polymer solar cells (PSCs). Furthermore, the nanostructure of PM6:Y6 light absorber changes a lot after introduction of BP nanosheets. Thus, weak charge recombination loss, high exciton generation rate and dissociation probability, and low transport resistance are observed in BP nanosheets doped PEDOT:PSS HTLs based cells, which result in improved power conversion efficiency (PCE). As a result, significant improvement of PCE (>18%) is observed in both non-fullerene and fullerene blend systems based cells. This result demonstrates a simple and effective strategy to form efficient HTLs in high-efficiency PSCs.

Morphological & Structural Control of Electrodeposited Sb Anodes through Solution Additives and Their Influence on Electrochemical Performance in Na-Ion Batteries

Alloy-based materials such as antimony (Sb) are of interest for both Li/Na-ion batteries due to their theoretical capacity and electronic conductivity. Of the various ways to fabricate Sb films (slurry casting, sputtering, etc.) one promising route is through the use of electrodeposition. Electrodeposition is an industrially relevant synthetic technique that allows for the use of solution additives to control different characteristics such as film uniformity, morphology, and electrical conductivity. Solution additives such as cetyltrimethylammonium bromide (CTAB) and bis-(3-sulfopropyl) disulfide (SPS) have been used to control characteristics such as particle morphology, and electrical conductivity in various applications but have not been applied to the electrodeposition of Sb for battery applications. In this study, Sb films were electrodeposited with various concentrations of CTAB and SPS and the structure, morphology, composition, and electrochemical performance in Na-ion batteries were compared. We report that CTAB and SPS additives can significantly influence electrodeposited Sb films by altering the morphology and reducing the crystallinity of the Sb films, affecting the electrochemical performance. These studies provide valuable insight into the tunability of alloy-based films through electrodeposition and solution additives.

Self-Limited ultraviolet laser sintering of liquid metal particles for μm-Thick flexible electronics devices

Lightweight, deformable and highly conductive conductors are rather appealing in flexible electronics devices such as electromagnetic interference (EMI) shielding films; however, the most commonly used metallic foils or carbon nanomaterials suffer from critical limitation of either film thickness or electrical conductivity. Herein, we present a facile approach to rapidly fabricate sintered liquid metal submicron particles (LMSPs) films in combination spray-coating with direct nanosecond ultraviolet (UV) laser sintering. High conductive, μm-thick sintered LMSPs films were prepared owing to the self-limited penetration depth of UV laser, and their sheet resistances are easily tuned at least seven orders of magnitude by the laser processing parameters. A calculated parametric map upon particle diameter and laser fluence whether or not a liquid metal particle is ruptured has been obtained and it is quite well in accordance to the experiment results. Such laser-sintered LMSPs films are finally utilized to fabricate shielding films with superior EMI shielding effectiveness (SE) of ∼33 dB and specific EMI SE over thickness (SSE/t) of ∼27500 dB•cm2•g−1, and flexible electromagnetic metamaterials with a high absorption above 99.9 % at resonance frequency of 12.9 GHz and 14.3 GHz, showing their high potential for flexible EMI shielding and electromagnetic wave absorption applications.

3D Printing of Largescale Functional Nanofilm using Electrically assisted Direct Ink Deposition

Functional nanofilms show significant importance for various applications in different fields, such as sustainable energy, biomedicine, electronics, and optics. However, there are still many challenges in the fabrication of nanostructured films with tailored properties using traditional manufacturing technologies. A novel 3D printing approach called electrical field-assisted direct ink deposition (EF-DID) was developed to produce large-scale nanofilms with controllable nanostructures and patternable features. In the proposed method, the formation of nanodroplets in the direct ink deposition was investigated under an electrostatic field with high voltage. Critical printing parameters, including solution concentration, deposition height, applied voltage, and ink flow rate, were studied systematically to understand fundamental mechanisms of the nanostructures generation during the printing. In addition, the scientific relationship between deposition parameters and nanofilm properties, including film thickness, electrical conductivity, and contact angle, were explored. Finally, patterned nanofilms with well-organized nanostructures were fabricated to demonstrate potential application prospects in the field of nanotechnology.

Liquid deposition modelling 3D printing of semiconductor tin sulphide (SnS) thin film for application in optoelectronic and electronic devices

This study is focused on the investigation of three-dimensional (3D) printed SnS thin film and the optimisation of SnS thin film thickness by additive layer deposition of the film using three-dimensional printing system based on liquid deposition modelling (LDM). Voids in separate island-like state and traps associated with certain film thickness affect charge carriers due to the presence of large grain boundaries associated with small grains which acts as electron trap thus affecting SnS thin film's optical band gap energy and electrical conductivity among others. SnS thin films were printed on glass substrate using LDM-3D printing. Surface Profilometer, Energy dispersive X-ray spectroscopy, X-ray diffractometer, Scanning electron microscope, Uv-vis spectrophotometer and four point probe were used to characterise the SnS thin films. The conductivity of 0.002987 (Ωm)-1 and optical energy band gap of 1.37 eV of 0.6 μm 3D printed SnS thin film was optimum and favours the attainment of the threshold voltage for optoelectronic and electronic application. The results demonstrate the potential of the LDM-3D printing of thin film for materials deposition and application which provides a new way of layer thickness variation and levelling of semiconductor thin film.

Multi-Layered Sol–Gel Spin-Coated CuO Nanofilm Characteristic Enhancement by Sn Doping Concentration

CuO films, with their many features, attract special attention for applications in various optoelectronics. In their pristine form, CuO films suffer from low conductivity, which limits their application. Modification, especially by doping, is thus needed. The effects of tin (Sn) doping on the structure, morphology, and optical and, more importantly, electrical properties of multi-layered copper oxide (CuO) films deposited onto tin-doped indium oxide (ITO)/glass substrates by sol–gel spin coating are examined here. The multi-layered films were characterized with X-ray diffraction (XRD), atomic force microscopy (AFM), electronic absorption (UV-Visible) spectra, and four probe methods. The results confirmed the substitution of Cu2+ ions by Sn4+ ions in the CuO crystallites without altering their monoclinic structure. The measured crystallite size values decreased with increased doping concentration, indicating increased imperfection. This applies to both 5- and 10-layered CuO films. The doping concentration affected other film characteristics, namely, surface morphology and electrical conductivity, in each layered film. Among various systems, the 10-layered film, with 1.5 at% Sn, exhibited optimal properties in terms of higher uniformity (mean square root surface roughness 41 nm) and higher conductivity (50.3 × 10−3·Ω−1·cm−1).

Ultrathin TiN Epitaxial Films as Transparent Conductive Electrodes.

Titanium nitride (TiN), a transition-metal compound with tight covalent Ti-N bonding, has a high melting temperature and superior mechanical and chemical stabilities compared to noble metals. With a reduction in thickness, the optical transmittance of TiN films can be drastically increased, and in combination with its excellent electrical conductivity, the ultrathin and continuous TiN film can be considered as an ideal alternative of the metal oxide electrodes. However, the deposition of ultrathin and continuous metallic layer with a smooth surface morphology is a major challenge for typical deposition methods such as thermal evaporation or reactive sputtering. In particular, defects mainly related with oxygen contents and surface scattering can significantly limit the performance of ultrathin TiN films. In this work, ultrathin TiN films with 2-10 nm in thickness are grown by using the nitrogen plasma-assisted molecular-beam epitaxy (MBE) method in an ultrahigh vacuum environment. Excellent surface morphology with a root-mean-square roughness of ≤0.12 nm and a high optical transparency of 75% over the whole visible regime are achieved for ultrathin TiN epitaxial films. The dielectric properties determined by the spectroscopic ellipsometry and the electrical properties measured by the terahertz spectroscopy and the Hall effect method reveal that the percolation thickness of the TiN epitaxial film is less than 2.4 nm and its electrical conductivity is higher than 1.1 × 104 Ω-1 cm-1. These features make MBE-grown ultrathin TiN epitaxial films a good candidate for robust, low cost, and large-area transparent conductive electrodes.

Physicomechanical, thermal and dielectric properties of eco‐friendly starch‐microcrystalline cellulose‐clay nanocomposite films for food packaging and electrical applications

AbstractPotato starch (PS) films reinforced with microcrystalline cellulose (MCC) were prepared with casting solution, and the effect of montmorillonite (MMT) clay in different proportions (1, 3, 5 and 10 wt%) using nanofiller was established. The films were investigated by Fourier transform ınfrared (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), tensile strength, opacity, colour, water vapour permeability and solubility. Tensile strength for nanocomposite films depending on the clay content was increased significantly from 0.64 to 1.89 MPa. The water vapour permeability of nanocomposite films was improved compared to the PSMCC blend without MMT. Also, dielectric properties and electrical conductivity of films were studied. The dielectric permittivity (έ), the dielectric loss (ε˝) and the electrical conductivity (σ) increased with increasing MMT content at frequencies between 100 Hz to 10 kHz. This nanocomposite with improved functional properties could be used in potential food packaging materials and electrical applications.

Influence of molecular weight of polycation polydimethyldiallylammonium and carbon nanotube content on electric conductivity of layer-by-layer films

For biological and engineering applications, nm-thin films with high electrical conductivity and tunable sheet resistance are desirable. Multilayers of polydimethyldiallylammonium chloride (PDADMA) with two different molecular weights (322 and 44.3 kDa) and oxidized carbon nanotubes (CNTs) were constructed using the layer-by-layer technique. The surface coverage of the CNTs was monitored with a selected visible near infrared absorption peak. Both the film thickness and the surface coverage of the CNTs increased linearly with the number of CNT/PDADMA bilayers deposited (film thickness up to 80 nm). Atomic force microscopy images showed a predominantly surface-parallel orientation of CNTs. Ohmic behavior with constant electrical conductivity of each CNT/PDADMA film and conductivity up to 4 · 103 S/m was found. A change in PDADMA molecular weight by almost a factor of ten has no effect on the film thickness and electrical conductivity, only the film/air roughness is reduced. However, increasing CNT concentration in the deposition dispersion from 0.15 up to 0.25 mg/ml results in an increased thickness of a CNT/PDADMA bilayer (by a factor of three). The increased bilayer thickness is accompanied by a decreased electrical conductivity (by a factor of four). The decreased conductivity is attributed to the increased monomer/CNT ratio.

Systematic Investigation of Solution-State Aggregation Effect on Electrical Conductivity in Doped Conjugated Polymers

Systematic Investigation of Solution-State Aggregation Effect on Electrical Conductivity in Doped Conjugated Polymers