Flexible, Transparent and Conductive Metal Mesh Films with Ultra‑High FoM for Stretchable Heating and Electromagnetic Interference Shielding

Despite the growing demand for transparent conductive films in smart and wearable electronics for electromagnetic interference(EMI)shielding,achieving a flexible EMI shielding film,while maintaining a high transmittance remains a significant challenge.Herein,a flexible,transparent,and conductive copper(Cu)metal mesh film for EMI shielding is fabricated by self-forming crackle template method and electroplating technique.The Cu mesh film shows an ultra-low sheet resistance(0.18Ω□^(-1)),high transmittance(85.8%@550 nm),and ultra-high figure of merit(>13,000).It also has satisfactory stretchability and mechanical stability,with a resistance increases of only 1.3%after 1,000 bending cycles.As a stretchable heater(ε>30%),the saturation temperature of the film can reach over 110°C within 60 s at 1.00 V applied voltage.Moreover,the metal mesh film exhibits outstanding average EMI shielding effectiveness of 40.4 dB in the X-band at the thickness of 2.5μm.As a demonstration,it is used as a transparent window for shielding the wireless communication electromagnetic waves.Therefore,the flexible and transparent conductive Cu mesh film proposed in this work provides a promising candidate for the next-generation EMI shielding applications.

Local thermal conductivity of inhomogeneous nano-fluidic films:A density functional theory perspective

Combining the mean field Pozhar-Gubbins(PG)theory and the weighted density approximation,a novel method for local thermal conductivity of inhomogeneous fluids is proposed.The correlation effect that is beyond the mean field treatment is taken into account by the simulation-based empirical correlations.The application of this method to confined argon in slit pore shows that its prediction agrees well with the simulation results,and that it performs better than the original PG theory as well as the local averaged density model(LADM).In its further application to the nano-fluidic films,the influences of fluid parameters and pore parameters on the thermal conductivity are calculated and investigated.It is found that both the local thermal conductivity and the overall thermal conductivity can be significantly modulated by these parameters.Specifically,in the supercritical states,the thermal conductivity of the confined fluid shows positive correlation to the bulk density as well as the temperature.However,when the bulk density is small,the thermal conductivity exhibits a decrease-increase transition as the temperature is increased.This is also the case in which the temperature is low.In fact,the decrease-increase transition in both the small-bulk-density and low-temperature cases arises from the capillary condensation in the pore.Furthermore,smaller pore width and/or stronger adsorption potential can raise the critical temperature for condensation,and then are beneficial to the enhancement of the thermal conductivity.These modulation behaviors of the local thermal conductivity lead immediately to the significant difference of the overall thermal conductivity in different phase regions.

Highly Thermally Conductive and Structurally Ultra‑Stable Graphitic Films with Seamless Heterointerfaces for Extreme Thermal Management

Highly thermally conductive graphitic film(GF)materials have become a competitive solution for the thermal management of high-power electronic devices.However,their catastrophic structural failure under extreme alternating thermal/cold shock poses a significant challenge to reliability and safety.Here,we present the first investigation into the structural failure mechanism of GF during cyclic liquid nitrogen shocks(LNS),which reveals a bubbling process characterized by“permeation-diffusion-deformation”phenomenon.To overcome this long-standing structural weakness,a novel metal-nanoarmor strategy is proposed to construct a Cu-modified graphitic film(GF@Cu)with seamless heterointerface.This well-designed interface ensures superior structural stability for GF@Cu after hundreds of LNS cycles from 77 to 300 K.Moreover,GF@Cu maintains high thermal conductivity up to 1088 W m^(−1)K^(−1)with degradation of less than 5%even after 150 LNS cycles,superior to that of pure GF(50%degradation).Our work not only offers an opportunity to improve the robustness of graphitic films by the rational structural design but also facilitates the applications of thermally conductive carbon-based materials for future extreme thermal management in complex aerospace electronics.

Large-Area Preparation of Flexible Carbon Nanofilms with Synergistically Enhanced Transmittance and Conductivity

Large-area flexible transparent conductive films(TCFs)are urgently in great demand for future electronics,optoelectronics,energy devices,and applications in other fields.Indium tin oxide(ITO)TCF,which is widely used in modern technology,is difficult to meet the needs of scientific and technological development(especially the need for a new generation of flexible electronic devices),because indium is a non-renewable resource and expensive,and ITO is inherently brittle.

Disorder effects in NbTiN superconducting resonators

Disordered superconducting materials like NbTiN possess a high kinetic inductance fraction and an adjustable critical temperature, making them a good choice for low-temperature detectors. Their energy gap(D), critical temperature(T_(c)),and quasiparticle density of states(QDOS) distribution, however, deviate from the classical BCS theory due to the disorder effects. The Usadel equation, which takes account of elastic scattering, non-elastic scattering, and electro–phonon coupling,can be applied to explain and describe these deviations. This paper presents numerical simulations of the disorder effects based on the Usadel equation to investigate their effects on the △, Tc, QDOS distribution, and complex conductivity of the NbTiN film. Furthermore, NbTiN superconducting resonators with coplanar waveguide(CPW) structures are fabricated and characterized at different temperatures to validate our numerical simulations. The pair-breaking parameter α and the critical temperature in the pure state T_(c)^(P) of our NbTiN film are determined from the experimental results and numerical simulations. This study has significant implications for the development of low-temperature detectors made of disordered superconducting materials.

Ultrafast Laser-Induced Excellent Thermoelectric Performance of PEDOT:PSS Films

Because poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT:PSS)is water processable,thermally stable,and highly conductive,PEDOT:PSS and its composites have been considered to be one of the most promising flexible thermoelectric materials.However,the PEDOT:PSS film prepared from its commercial aqueous dispersion usually has very low conductivity,thus cannot be directly utilized for TE applications.Here,a simple environmental friendly strategy via femtosecond laser irradiation without any chemical dopants and treatments was demonstrated.Under optimal conditions,the electrical conductivity of the treated film is increased to 803.1 S cm^(-1)from 1.2 S cm^(-1)around three order of magnitude higher,and the power factor is improved to 19.0μW m^(-1)K^(-2),which is enhanced more than 200 times.The mechanism for such remarkable enhancement was attributed to the transition of the PEDOT chains from a coil to a linear or expanded coil conformation,reduction of the interplanar stacking distance,and the removal of insulating PSS with increasing the oxidation level of PEDOT,facilitating the charge transportation.This work presents an effective route for fabricating high-performance flexible conductive polymer films and wearable thermoelectric devices.

Temperature-mediated structural evolution of vapor–phase deposited cyclosiloxane polymer thin films for enhanced mechanical properties and thermal conductivity

Polymer-derived ceramic(PDC) thin films are promising wear-resistant coatings for protecting metals and carbon-carbon composites from corrosion and oxidation.However,the high pyrolysis temperature hinders the applications on substrate materials with low melting points.We report a new synthesis route for PDC coatings using initiated chemical vapor deposited poly(1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane)(pV_3D_3) as the precurs or.We investigated the changes in siloxane moieties and the network topology,and proposed a three-stage mechanism for the thermal annealing process.The rise of the connectivity number for the structures obtained at increased annealing temperatures was found with strong correlation to the enhanced mechanical properties and thermal conductivity.Our PDC films obtained via annealing at 850℃ exhibit at least 14.6% higher hardness than prior reports for PDCs synthesized below 1100℃.Furthermore,thermal conductivity up to 1.02 W(mK)^(-1) was achieved at the annealing temperature as low as 700℃,which is on the same order of magnitude as PDCs obtained above 1100℃.Using minimum thermal conductivity models,we found that the thermal transport is dominated by diffusons in the films below the percolation of rigidity,while ultra-short mean-free path phonons contribute to the thermal conductivity of the films above the percolation threshold.The findings of this work provide new insights for the development of wear-resistant and thermally conductive PDC thin films for durable protection coatings.

Optical and electrical properties of BaSnO_(3) and In_2O_(3) mixed transparent conductive films deposited by filtered cathodic vacuum arc technique at room temperature

For the crystalline temperature of BaSnO_(3)(BTO)was above 650℃,the transparent conductive BTO-based films were always deposited above this temperature on epitaxy substrates by pulsed laser deposition or molecular beam epitaxy till now which limited there application in low temperature device process.In the article,the microstructure,optical and electrical of BTO and In_(2)O_(3) mixed transparent conductive BaInSnO_(x)(BITO)film deposited by filtered cathodic vacuum arc technique(FCVA)on glass substrate at room temperature were firstly reported.The BITO film with thickness of 300 nm had mainly In_(2)O_(3) polycrystalline phase,and minor polycrystalline BTO phase with(001),(011),(111),(002),(222)crystal faces which were first deposited at room temperature on amorphous glass.The transmittance was 70%–80%in the visible light region with linear refractive index of 1.94 and extinction coefficient of 0.004 at 550-nm wavelength.The basic optical properties included the real and imaginary parts,high frequency dielectric constants,the absorption coefficient,the Urbach energy,the indirect and direct band gaps,the oscillator and dispersion energies,the static refractive index and dielectric constant,the average oscillator wavelength,oscillator length strength,the linear and the third-order nonlinear optical susceptibilities,and the nonlinear refractive index were all calculated.The film was the n-type conductor with sheet resistance of 704.7Ω/□,resistivity of 0.02Ω⋅cm,mobility of 18.9 cm2/V⋅s,and carrier electron concentration of 1.6×10^(19) cm^(−3) at room temperature.The results suggested that the BITO film deposited by FCVA had potential application in transparent conductive films-based low temperature device process.

Effect of RF power on the properties of transparent conducting zirconium-doped zinc oxide films prepared by RF magnetron sputtering

Transparent and conducting zirconium-doped zinc oxide films with high transparency and relatively low resistivity have been successfully prepared by radio frequency （RF） msgnetron sputtering at room temperature, The RF power is varied from 75 to 150 W. At first the crystallinity and conductivity of the film are improved and then both of them show deterioration with the increase of the RF power, The lowest resistivity achieved is 2.07 × 10^-3Ωcm at an RF power of 100W with a Hall mobility of 16cm^2V^-1s^-1 and a carrier concentration of 1.95 × 10^20 cm^-3. The films obtained are polycryetalline with a hexagonal structure and a preferred orientation along the c-axis, All the films have a high transmittance of approximately 92% in the visible range. The optical band gap is about 3.33 eV for the films deposited at different RF powers.

Fabrication of nanoporous TiO_2 films with novel surface morphology on conducting glass(FTO) substrate

The crystalline structure and surface morphology of TiO2 semiconductor coating play an important role in the conversion efficiency of dye-sensitized solar cells. In order to obtain TiO2 coating with controllable morphology and high porosity, nanoporous TiO2 films were fabricated on conducting glass （FTO） substrates, Ti thin films （1.5-2 gin） were deposited on conducting glass （FTO） substrates via the DC sputtering method, and then electrochemically anodized in NH4F/ethylene glycol solution. The crystalline structure and surface morphology of the samples were characterized by X-ray diffraction （XRD） and field emission scanning electron microscopy （FESEM）, respectively. The influences of anodizing potential, electrolyte composition, and pH value on the surface morphology of nanoporous TiO2 films were extensively studied. The growth mechanism of nanoporous TiO2 films was discussed by current density variations with anodizing time. The results demonstrate that nanoporous TiO2 films with high porosity and three-dimensional （3D） networks are observed at 30 V, when the NH4F concentration in ethylene glycol solution is 0.3% （mass fraction） and the electrolyte pH value is 5.0.

Conduction Properties and Scattering Mechanisms in F-doped Textured Transparent Conducting SnO_2 Films Deposited by APCVD

Transparent conducting F-doped texture SnO2 films with resistivity as low as 5× 10-4 Ω ·cm,with carrier concentrations between 3.5 × 1020 and 7× 1020 cm-3 and Hall mobilities from 15.7 to 20.1 cm2/(V/s) have been prepared by atmosphere pressure chemical vapour deposition (APCVD). These polycrystalline films possess a variable preferred orientation, the polycrystallite sizes and orientations vary with substrate temperature. The substrate temperature and fluorine flow rate dependence of conductivity, Hall mobility and carrier conentration fOr the resultingfilms have been obtained. The temperature dependence of the mobiity and carrier concentrationhave been measured over a temperature range 16～400 K. A systematically theoretical analysis on scattering mechanisms for the highly conductive SnO2 films has been given. Both theoretical analysis and experimental results indicate that for these degenerate, polycrystalline SnO2 ：F films in the low temperature range (below 100 K), ionized impurity scattering is main scattering mechanism. However, when the temperature is higher than 100 K, the lattice vibration scattering becomes dominant. The grain boundary scattering makes a small contribution to limit the mobility of the films.

THE BAND STRUCTURE AND WORK FUNCTION OF TRANSPARENT CONDUCTING ALUMINUM AND MANGANESE CO-DOPED ZINC OXIDE FILMS

Al and Mn co-doped-ZnO films have been prepared at room temperature by DC reacti ve magnetron sputtering technique. The optical absorption coefficient, apparent and fundamental band gap, and work function of the films have been investigated using optical spectroscopy, band structure analyses and ultraviolet photoelectro n spectroscopy (UPS). ZnO films have direct allowed transition band structure, w hich has been confirmed by the character of the optical absorption coefficient. The apparent band gap has been found directly proportional to N2/3, showing that the effect of Burstein-Moss shift on the band gap variations dominates over the many-body effect. With only standard cleaning protocols, the work function of ZnO: (Al, Mn) and ZnO: Al films have been measured to be 4.26 and 4.21eV, respec tively. The incorporation of Mn element into the matrix of ZnO, as a relatively deep donor, can remove some electrons from the conduction band and deplete the d ensity of occupied states at the Fermi energy, which causes a loss in measured p hotoemission intensity and an increase in the surface work function. Based on th e band gap and work function results, the energy band diagram of the ZnO: (Al, M n) film near its surface is also given.

Dependence of Thermal Annealing on Transparent Conducting Properties of HoF_3-Doped ZnO Thin Films

A kind of n-type HoF_3-doped zinc oxide-based transparent conductive film has been developed by electron beam evaporation and studied under thermal annealing in air and vacuum at temperatures 100–500℃.Effective substitutional dopings of F to O and Ho to Zn are realized for the films with smooth surface morphology and average grain size of about 50 nm.The hall mobility,electron concentration,resistivity and work function for the asdeposited films are 47.89 cm^2/Vs,1.39×10^(20)cm^(-3),9.37×10^(-4)Ω·cm and 5.069 eV,respectively.In addition,the average transmittance in the visible region(400–700 nm)approximates to 87%.The HoF_3:ZnO films annealed in air and vacuum can retain good optoelectronic properties under 300℃,thereinto,more stable electrical properties can be found in the air-annealed films than in the vacuum-annealed films,which is assumed to be a result of improved nano-crystalline lattice quality.The optimized films for most parameters can be obtained at 200℃ for the air-annealing case and at room temperature for the vacuum annealing case.The advisable optoelectronic properties imply that HoF_3:ZnO can facilitate carrier injection and has promising applications in energy and light sources as transparent electrodes.

Preparation and Characterization of Reduced Graphene-P3HT Composite Thin Films for Use as Transparent Conducting Electrodes

With the aim of producing simple and effective transparent conducting electrodes, the conducting polymer poly(3-hexylthiophene) (P3HT) incorporated with reduced graphene oxide film (rGO) (called rGO-P3HT) was prepared by spin-coating method. Structural, electrical and optical characterization showed that rGO-P3HT films 9.0 wt% P3HT exhibited good stability when exposed to the ambient atmosphere. These composite films of 200 nm thickness possess a sheet resistance and transparency of R□~ 17Ω and T ~ 72%, respectively. Owing to containing conducting polymer, rGO-P3HT-coated glass could be efficiently used in photovoltaic applications, in organic solar cells in particular, with the replacement of the indium tin oxide (ITO) and fluorine tin oxide (FTO) electrodes.

Optical-Electronic Properties of Carbon-Nanotubes Based Transparent Conducting Films

Three coating methods (slot, dip and blade coatings) were used separately to coat a well-dispersed single-wall carbonnanotube (SWCNT) solution on polyethylene terephthalate (PET) film, and the resulting optical and electronic properties were measured and compared. It was found that the sheet resistance and the transparency of the SWCNT coated film decreased as the coating speed increased for dip and blade coatings, but were independent of the coating speed for slot coating. All three coating methods were able to produce transparent conductive film with transparency above 85% and sheet resistance close to 1000 ohm/sq. For industrial production, the slot die coating method appears to be more suitable in terms of high coating speed and uniformity of optical and electronic properties.

Microwave measurement of the conductivity of conducting thin films

A new method to measure the conductivity of conducting thin films in a contactle s s fashion was demonstrated. A microwave compact equipment working at 94 GHz was used to measure the amplitude of the reflection coefficient of the microwave sig na l. Indium Tin Oxide films having conductivity of 8.20×10 4～8.02×10 5 S/m on the glass substrates were used as the samples. An evaluation equation was bui lt to determine the conductivity from the measured amplitude of the reflection c oefficient. The evaluated conductivity of conducting thin films agrees well with their actual value.

Preparation of YBa_2Cu_3O_(7-δ) superconducting thick film on Ni-W tapes via electrophoretic deposition

The preparation of La0.4Sr0.6TiO3 （LSTO） buffer layer and YBa2Cu3O7-δ（YBCO） superconducting thick film by a low cost technology was studied. The crystal orientation of LSTO and YBCO films was detected by X-ray diffraction, the conductivity of LSTO film and superconductivity of YBCO coating were investigated by standard four-probe method. Excellent in-plane alignment, smooth and dense LSTO buffer layer was successfully prepared on textured Ni-W taps by metal organic deposition （MOD）. YBCO thick film was fabricated by electrophoretic deposition （EPD）. The effects of applied voltage and deposition time on the YBCO coatings properties were studied. The results show that the critical current density of the YBCO coating deposited under 138 V for 35 min was about 600 A/cm2 （0 T, 77 K）.

Effects of Atomic Oxygen Irradiation on Transparent Conductive Oxide Thin Films

Transparent conductive oxide （TCO） thin film is a kind of functional material which has potential applications in solar cells and atomic oxygen （AO） resisting systems in spacecrafts. Of TCO, ZnO：Al （ZAO） and In2O3：Sn （ITO） thin films have been widely used and investigated. In this study, ZAO and ITO thin films were irradiated by AO with different amounts of fluence. The as-deposited samples and irradiated ones were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and Hall-effect measurement to investigate the dependence of the structure, morphology and electrical properties of ZAO or ITO on the amount of fluence of AO irradiation. It is noticed that AO has erosion effects on the surface of ZAO without evident influences upon its structure and conductive properties. Moreover, as the amount of AO fluence rises, the carrier concentration of ITO decreases causing the resistivity to increase by at most 21.7%.

Hierarchically Multifunctional Polyimide Composite Films with Strongly Enhanced Thermal Conductivity

The development of lightweight and integration for electronics requires flexible films with high thermal conductivity and electromagnetic interference(EMI) shielding to overcome heat accumulation and electromagnetic radiation pollution.Herein,the hierarchical design and assembly strategy was adopted to fabricate hierarchically multifunctional polyimide composite films,with graphene oxide/expanded graphite(GO/EG) as the top thermally conductive and EMI shielding layer,Fe_(3)O_(4)/polyimide(Fe_(3)O_(4)/PI) as the middle EMI shielding enhancement layer and electrospun PI fibers as the substrate layer for mechanical improvement.PI composite films with 61.0 wt% of GO/EG and 23.8 wt% of Fe_(3)O_(4)/PI exhibits high in-plane thermal conductivity coefficient(95.40 W(m K)^(-1)),excellent EMI shielding effectiveness(34.0 dB),good tensile strength(93.6 MPa) and fast electric-heating response(5 s).The test in the central processing unit verifies PI composite films present broad application prospects in electronics fields.

Emerging Flexible Thermally Conductive Films:Mechanism,Fabrication,Application

Effective thermal management is quite urgent for electronics owing to their ever-growing integration degree,operation frequency and power density,and the main strategy of thermal management is to remove excess energy from electronics to outside by thermal conductive materials.Compared to the conventional thermal management materials,flexible thermally conductive films with high in-plane thermal conductivity,as emerging candidates,have aroused greater interest in the last decade,which show great potential in thermal management applications of next-generation devices.However,a comprehensive review of flexible thermally conductive films is rarely reported.Thus,we review recent advances of both intrinsic polymer films and polymer-based composite films with ultrahigh in-plane thermal conductivity,with deep understandings of heat transfer mechanism,processing methods to enhance thermal conductivity,optimization strategies to reduce interface thermal resistance and their potential applications.Lastly,challenges and opportunities for the future development of flexible thermally conductive films are also discussed.