Porous Thin Films Research Articles

Periodic Nanoslot Patterns as an Effective Approach to Improving the Thermoelectric Performance of Thin Films

For thermoelectric applications, thermoelectric $\mathrm{Si}$ thin films with periodic circular pores have been intensively studied because of the low price and earth abundance of $\mathrm{Si}$. In this work, a different periodic nanoporous pattern is investigated for its potential thermoelectric benefit, i.e., a $\mathrm{Si}$ thin film with periodic nanoslots. Inside such structures, the neck between adjacent nanoslots functions as the nanorestriction to suppress the phonon transport, leading to a dramatically reduced lattice thermal conductivity. When the neck width is still longer than the mean free paths of majority charge carriers, bulklike electron transport can be maintained so that the thermoelectric ZT can be enhanced. For the thermal designs of these porous thin films, a simple but accurate analytical model based on the mean-free-path modification with a characteristic length is derived and is used to predict their thermoelectric properties. For heavily doped $\mathrm{Si}$ films with the neck width reduced to 5 nm, the computed ZT can reach 0.58 at 1100 K. The proposed nanoslot pattern can be extended to general thin films and atomic thick materials to tune their transport properties.

Hexagonal Boron Nitride-Enhanced Optically Transparent Polymer Dielectric Inks for Printable Electronics.

Solution‐processable thin‐film dielectrics represent an important material family for large‐area, fully‐printed electronics. Yet, in recent years, it has seen only limited development, and has mostly remained confined to pure polymers. Although it is possible to achieve excellent printability, these polymers have low (≈2–5) dielectric constants (εr). There have been recent attempts to use solution‐processed 2D hexagonal boron nitride (h‐BN) as an alternative. However, the deposited h‐BN flakes create porous thin‐films, compromising their mechanical integrity, substrate adhesion, and susceptibility to moisture. These challenges are addressed by developing a “one‐pot” formulation of polyurethane (PU)‐based inks with h‐BN nano‐fillers. The approach enables coating of pinhole‐free, flexible PU+h‐BN dielectric thin‐films. The h‐BN dispersion concentration is optimized with respect to exfoliation yield, optical transparency, and thin‐film uniformity. A maximum εr ≈ 7.57 is achieved, a two‐fold increase over pure PU, with only 0.7 vol% h‐BN in the dielectric thin‐film. A high optical transparency of ≈78.0% (≈0.65% variation) is measured across a 25 cm2 area for a 10 μm thick dielectric. The dielectric property of the composite is also consistent, with a measured areal capacitance variation of <8% across 64 printed capacitors. The formulation represents an optically transparent, flexible thin‐film, with enhanced dielectric constant for printed electronics.

Fabrication and characterization of porous WO3 thin film as a high accuracy cyclohexene sensor

In the last decade, an increase of attention to monitoring the hazardous gases and vapors in industry, laboratories, and homes has attracted extensive interest in developing gas sensors. This research investigates the use of porous WO3 thin film as a high accuracy cyclohexene sensor. Oblique deposition and subsequently the post-annealing process were employed to produce the mentioned device. X-ray diffraction (XRD), atomic force microscopy (AFM), and physical adsorption isotherm were used to investigate the crystallographic structure, surface morphology, and porosity of the sample, respectively. Sensing parameters including response amplitude, operating temperature, response and recovery times, detection limit, selectivity, reproducibility, and stability were also studied to find a deep-perception of the device sensing performance. The results disclose that the prepared device in this research shows a decent and fast response to the object and can be introduced as a reliable cyclohexene sensor.

Combined Modeling of the Optical Anisotropy of Porous Thin Films

In this article, a combined approach for studying the optical anisotropy of porous thin films obtained by the glancing angle deposition is presented. This approach combines modeling on the atomistic and continuum levels. First, thin films clusters are obtained using the full-atomistic molecular dynamics simulation of the deposition process. Then, these clusters are represented as a medium with anisotropic pores, the shapes parameters of which are determined using the Monte Carlo based method. The difference in the main components of the refractive index is calculated in the framework of the anisotropic Bruggeman effective medium theory. The presented approach is tested and validated by comparing the analytical and simulation results for the model problems, and then is applied to silicon dioxide thin films. It is found that the maximum difference between the main components of the refractive index is 0.035 in a film deposited at an angle of 80°. The simulation results agree with the experimental data reported in the literature.

Evolution of Temperature-Driven Interfacial Wettability and Surface Energy Properties on Hierarchically Structured Porous Superhydrophobic Pseudoboehmite Thin Films.

Interaction of water on heterogeneous nonwetting interfaces has fascinated researchers' attention for wider applications. Herein, we report the evolution of hierarchical micro-/nanostructures on superhydrophobic pseudoboehmite surfaces created from amorphous Al2O3 films and unraveled their temperature-driven wettability and surface energy properties. The influence of hot water immersion temperature on the dissolution-reprecipitation mechanism and the surface geometry of the Al2O3 film have been extensively analyzed, which helped in attaining the optimal Cassie-Baxter state. The evolution of pseudoboehmite films has been structurally characterized using grazing incidence X-ray diffraction, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy and atomic force microscopy. Interfacial surface energy components on the structured superhydrophobic surface exhibited a very low surface energy of ∼4.6 mN/m at room temperature and ultrahigh water contact angle >175°. The interaction between water droplets on the nonwetting surface was comprehended and correlated to the temperature-dependent surface energy properties. The surface energy and wettability of the structured pseudoboehmite superhydrophobic surface exhibited an inverse behavior as a function of temperature. Interestingly, the superhydrophobic surface exhibited "Leidenfrost effect" below the boiling point of water (67 °C), which is further correlated with the intermolecular forces, interfacial water molecules and surface-terminated groups. These high-temperature wetting transition studies could be potentially valuable for solid-liquid systems working at nonambient temperatures, and also this approach can pave new pathways for better understanding of the solid/liquid interfacial interactions on nanoengineered superhydrophobic surfaces.

Graphitic Nanoporous Carbon Thin Films: Fabrication Method, Structural, Electrical and Gas Sensor Properties

Carbon nanoporous thin films are very attractive for application in fields of supercapacitors, fuel cells, gas sensors and others. However due to it very high resistance an employment of this material for resistance gas sensor is problematic. At the same time graphene based materials are very sensitive to different gas ambient and have a resistivity suitable for testing. In this work the new method of formation of high porous graphite-like thin films by RF magnetron plasma enhanced chemical vapor deposition (MPECVD) from argon-methane/argon-acetylene gas mixture followed by annealing at 650ºC, is suggested. A comparative study of transformation of nanoporous carbon film produced in different carbon-hydrogen atmosphere into graphitic one, their structural and electrical properties are presented. The films of nanoporous carbon were fabricated on silicon or SiO2/Si wafers. To clarify chemical structure of the film FTIR spectroscopy and XPS were used. Micro-Raman spectroscopy and AFM were applied to determine of structure and surface morphology correspondingly. X-ray refraction (XRR) method allows us to determine a density and a thickness of the films. Four point probe method and transmittance line (TSL) technique were used for the analysis of electrical properties. Additionally, electrical conductivity at different temperature and frequency was examined by measurement of resistance between two nearest Ni contacts. The same contacts were used to estimate of the gas sensitivity.It was shown that initial deposited films have mainly sp3 C-H bonds without appearance of silicon bonds. AFM demonstrates nanostructured surface morphology with size of the surface fluctuation about 3 nm; a density of the films is about 1.3 g/cm3 for both carbon films, that corresponds to nanoporous carbon; resistivity is about 108 Ohm×cm. After thermal annealing at 650°C for 30 min in N2 atmosphere the sp3 C-H bonds are disappeared, and C=C sp2 bonds are formed. Besides the resistivity the films synthesized in argon-methane gas mixture decreases to 104 Ohm×cm whereas the films synthesized in argon-acetylene gas mixture decreases their resistivity up to 102 Ohm×cm. The density of the C films synthesized in in argon-methane gas mixture reaches about 1.5 g/cm3 that corresponds to 34% of porosity, and material shows layered structure. The density of the C films synthesized in in argon-acetylene gas mixture falls to 1.01 g/cm3 that corresponds to 55% of porosity. Graphitized films synthesized in argon-methane gas mixture appears sensory sensitivity to moisture and ammonia whereas the films synthesized in argon-acetylene gas mixture show low sensitivity to these gases. The nature of the gas sensor resistor sensitivity is discussed.

Graphene-Coated Porous PDMS As a Gas Sensor for Potential Epidermal Electronics Applications

Introduction Epidermal electronics that can intimately integrate with human skin are getting much attention due to ultrathin, soft, and light-weight [1]. These capabilities create interesting opportunities for diverse wearable sensor applications such as sweat monitoring, multiple electrophysiological signal monitoring, subtle motion sensing, ultraviolet sensing, gas monitoring, etc [2]. The authors have been developed graphene-based gas sensors having various forms including electrospun fiber [3], commercially-available yarn [4], stretchable yarn [5], and fabric [6]. In this paper, we present the stretchable porous e-skin based gas sensor comprising of porous polydimethysiloxane (PDMS) as a stretchable substrate and reduced graphene oxide (RGO) as gas sensing materials showed high NO2 sensitivity under 30% strain at room temperature. Method Porous PDMS thin films with the average pore size of 10 um were achieved by breath figure method [7]. The porous PDMS film were functionalized with 3-aminopropyltriethoxysilane (APTES) via chemical vapor treatment, which induced positive charges on the surface of porous PDMS film. Spray coating was performed with a commercial spray coater system (Jinsung, Korea). GO dispersed solution of 1.0 mg/mL was deposited onto the amine functionalized periodic porous PDMS films. The prepared GO deposited porous PDMS films were chemically reduced by immersing them in a reduction agent of hydriodic acid solution at 50 °C for 20 min. To neutralize and remove any residual on the RGO porous PDMS films, the samples were repeatedly rinsed with a sodium bicarbonate solution and deionized water, and then dried in a chemical hood. The stretchable gas sensors were fabricated by deposition silver paste onto the tops of the RGO films to make electrodes by silk screening method. Results and Conclusions The RGO porous PDMS films exhibited distinctive wrinkles and ripples with high density on its surface, which was attributed to the successful coating of RGO sheets on the surface of porous PDMS film. We believe that numerous wrinkles make the RGO porous PDMS films more stable against several deformations. The Raman spectrum of RGO porous PDMS films exhibited typical RGO spectral features, such as the D peak at 1340 cm-1 (defects in graphene) and the G peak at 1580 cm-1 (a stretching mode of C-C bond of the sp2 structure of graphene).We also studied the electrical properties of porous PDMS films coated with RGO sheets using four probe method. A GO coated porous PDMS film yielded an electrical conductivity of about 10-8 S/cm. After chemical reduction, the conductivity of RGO porous PDMS increased by approximately seven orders of magnitude. Our RGO porous PDMS films could maintain stable electrical conductivity values upon about 30% strain deformation. The mechanical stability of the RGO porous PDMS films was evaluated by measuring the electrical conductivity under repeated stretching and releasing. The electrical resistance of the samples remains unchanged even after 5000 cycles. The as-prepared RGO porous films are mechanically robust and can be deformed without device performance degradation, making them very attractive candidates for epidermal electronic devices.Porous PDMS coated with reduced graphene oxide responded to NO2 gas with sensitive and selective manner. When we compare the response (Ra/Rg) of porous PDMS with that of non-porous PDMS, porous PDMS shows 20% stronger response to NO2 compared to non-porous PDMS. The porous nature is considered to contribute to strong response due to increase of reaction possibility with reduced graphene oxide and NO2 gas. We found that the response of gas sensor was increased around 20% upon elongation. We believe that the hidden area of pores in the PDMS matrix can be exposed to the gas molecules upon elongation. Finally, we found that the sensor shows reliability in terms of the response up to 5,000 times elongation-relaxation cycles. In the future, we expect that the thin porous PDMS can be attached to the skin and find the applications in healthcare by sensing gas molecules emitted from skin. Acknowledgement This research was supported the R&D Program (Development of a mobile diet-monitoring technology based on multiple biomarkers by the National Research Foundation of Korea under research projects, NRF-2017M3A9F1033056).

Sintering-resistant platinum electrode achieved through atomic layer deposition for thin-film solid oxide fuel cells

Abstract Thin-film solid oxide fuel cells (TF-SOFCs) using a dense and thin electrolyte have attracted much attention as a promising portable power generator because they can lower the operating temperature of devices, which is a key issue related to conventional SOFCs, to below 500 °C and are compatible with several microfabrication processes. Highly porous interconnected Pt thin films are now widely used as oxygen electrodes, but their poor thermal stability seriously hampers the sustainable operation of TF-SOFCs. Here, we demonstrate how Al2O3 layers coated through atomic layer deposition effectively suppress the degradation of nanoporous Pt thin-film electrodes. Although Al2O3 is an electrical insulator, the selection of an appropriate overcoat thickness ensures stable electrochemical reaction sites of the Pt electrode at high temperatures even without serious current collection or gas flow issues. As a result, a 3.6-nm-thick Al2O3 layer maintains the high specific surface area morphology of Pt thin films at 450 °C and improves the electrode activity by more than twofold compared to an uncoated sample. These results suggest that a simple and scalable coating strategy enables the implementation of TF-SOFCs with ideal performance and durability outcomes.

Controlling anisotropic electrical conductivity in porous graphene-nanotube thin films

We suggest an idea of a new method for controlling the electrical conductivity of graphene-nanotube films using the physical effect that arises from the seamless contact of vertically oriented single-walled carbon nanotubes (SWCNTs) with graphene layers. When increasing the nanotube length by atomic layers in a graphene nanohole, the electrical conductivity of the graphene layer oscillates. This effect is based on the natural feature of armchair nanotubes, whose electronic properties and energy critically depend on the atomic framework length. The results of in silico studies show that the appearance of this effect leads to an increase in the electrical conductivity of graphene layers by 3–10 times. Besides, there is anisotropy: the electrical conductivity is 3–7 times greater in the armchair direction than in the zigzag direction. By adjusting the nanotube length, one can control the magnitude of the electrical conductivity and anisotropy. The amplitude of the oscillations is determined by the nanotube diameter, the symmetry of the transition zone of the seamless contact between graphene and nanotube, and the distance between nanotubes. To conduct in silico studies, an original approach is developed to identify energetically favorable SWCNT-graphene junctions during the formation of SWCNT of various diameters in a graphene nanohole.

Self-powered microfluidic pump using evaporation from diatom biosilica thin films

In recent years, researchers have successfully applied diatom biosilica to molecular detection platforms including Surface-Enhanced Raman Scattering (SERS) optofluidic sensors that are currently capable of detecting a variety of biological and chemical molecules at concentrations as low as 10−10 M. This study investigates the feasibility of an SERS device that couples the sensing and pumping capabilities of diatom biosilica thin films by determining flow rate limitations and stability. In this paper, we quantify the ability of porous diatom biosilica thin films to continuously pump deionized (DI) water from a reservoir via wicking flow by utilizing the strong capillary forces of the porous film coupled with evaporation. Our microfluidic device is comprised of a narrow horizontal reservoir fixed to a horizontal capillary whose end contacts a diatom biosilica film. Flow rates were controlled by altering the size and/or temperature of the biosilica porous film, determined by tracking the liquid meniscus displacement in the reservoir, and correlated with a modified laminar boundary-layer model. System stability was observed by tracking flow rates over the course of a given experiment, image analysis of the meniscus contacting the film, and a flow duration study. We found that for untreated DI water bubbles begin to form in the capillary tube at temperatures above 40 °C, but degassed water remains stable at temperatures of 90 °C and below. The pumping capabilities of the films ranged from 0.11 to 10.46 µL/min, matched theoretical predictions, demonstrated stable flow trends, and maintained flow for over 48 h.

Oxygen Vacancies Enabled Porous SnO2 Thin Films for Highly Sensitive Detection of Triethylamine at Room Temperature.

Detection of volatile organic compounds (VOCs) at room temperature (RT) currently remains a challenge for metal oxide semiconductor (MOS) gas sensors. Herein, for the first time, we report on the utilization of porous SnO2 thin films for RT detection of VOCs by defect engineering of oxygen vacancies. The oxygen vacancies in the three-dimensional-ordered SnO2 thin films, prepared by a colloidal template method, can be readily manipulated by thermal annealing at different temperatures. It is found that oxygen vacancies play an important role in the RT sensing performances, which successfully enables the sensor to respond to triethylamine (TEA) with an ultrahigh response, for example, 150.5-10 ppm TEA in a highly selective manner. In addition, the sensor based on oxygen vacancy-rich SnO2 thin films delivers a fast response and recovery speed (53 and 120 s), which can be further shortened to 10 and 36 s by elevating the working temperature to 120 °C. Notably, a low detection limit of 110 ppb has been obtained at RT. The overall performances surpass most previous reports on TEA detection at RT. The outstanding sensing properties can be attributed to the porous structure with abundant oxygen vacancies, which can improve the adsorption of molecules. The oxygen vacancy engineering strategy and the on-chip fabrication of porous MOS thin film sensing layers deliver great potential for creating high-performance RT sensors.

Investigation of Grain Radius Dependence of Sensitivity for Porous Thin Film Semiconducting Metal Oxide Gas Sensor

In this paper, a new diffusion-reaction equation was formulated to research the influences of grain radius on the transients of gas transport and gas sensitivity for porous thin film medium semiconducting metal oxide gas sensor, based on the phenomenon that a target gas diffuses in the sensing film via Knudsen diffusion and reacts with adsorbed oxygen on the pore surfaces following Langmuir adsorption. In order to describe gas transport inside the sensing film, the equation has been solved numerically under unsteady-state conditions. When the gas concentration reached a steady state, the relationship between gas concentration and film depth was formulated using data fitting method to investigate the influences of grain radius on gas sensitivity, according to the linear relation between the sheet conductance of the sensing film and the gas concentration at the corresponding depth, and the reality that the conductance of the entire film is an integration of sheet conductance over the whole range of the film from the surface to the substrate.

Electrochemical behavior of hydrothermally synthesized porous groundnuts-like samarium oxide thin films

One pot hydrothermal method is used for synthesis of groundnuts-like samarium oxide (Sm2O3) thin film on stainless steel substrate. The Sm2O3 film is characterized by X-ray diffraction, water contact angle, UV–visible spectrophotometer, photoluminescence, and field emission scanning electron microscopy techniques. The hydrothermal method allows the formation of cubic Sm2O3 film with porous groundnuts-like morphology. The Sm2O3 film is hydrophilic with the optical band gap of 3.70 eV. Electrochemical capacitive behavior of Sm2O3 film is studied using cyclic voltammetry, galvanostatic charge–discharge measurement and electrochemical impedance spectroscopy. The Sm2O3 film exhibits maximum specific capacitance of 155 Fg−1 at 5 mVs−1 scan rate in 1 M KOH electrolyte.

Nanomechanical characterization and modeling of anodized porous aluminum oxide thin films with photografted anti-biofouling polymer brushes on their pore walls

Nanocomposites are known for their unique properties with many potential applications. In the present work, porous anodic aluminum oxide (AAO) thin films were processed on glass substrates and subsequently photo-grafted with a zwitterionic anti-biofouling polymer. This allows to fabricate scratch-resistant, transparent anti-biofouling films. The microstructure and how it is affected by nanomechanical testing are investigated by scanning electron microscopy and atomic force microscopy. It is shown that the polymer forms a thin layer on the pore walls and in deionized water, the pore diameter changes due to swelling of the polymer. The nanomechanical and scratch resistance properties are studied using a nanoindenter testing system. The experimental results are validated via numerical calculations. The values of the elastic modulus and hardness are shown to be in good agreement with the numerical ones, and under dry conditions, higher values were obtained in comparison to wet films. There is also a large agreement between modeling and microscopic deformation behavior of the films. Finally, the critical loads in dry and wet conditions for the non-coated AAO samples are approximately the same, while for the coated samples, the critical load is reached rapidly in wet condition in comparison to the dry one.

Porous Silica Nanotube Thin Films as Thermally Insulating Barrier Coatings

The fabrication and examination of a porous silica thin film, potentially for use as an insulating thin film, were investigated. A vertically aligned carbon nanotube (CNT) forest, created by chemical vapor deposition (CVD), was used as scaffolding to construct the porous film. Silicon was deposited on the CNT forest using low-pressure CVD (LPCVD) and then oxidized to remove the CNTs and convert the silicon to silica for electrical or thermal passivation (e.g., thermal barrier). Thermal conductivity was determined using a 1D heat-transfer analysis that equated radiative heat loss in a vacuum with conduction through the substrate and thin film stack. A comparison of the surface temperature differences between a sample film and a reference of comparable thermal resistance enabled determination of the increase in the thermal resistance and of the thermal conductivity of the films. For film thicknesses of approximately 55 μm, the cross-plane thermal conductivity was found to be 0.054–0.071 W m–1 K–1 over 378–422 K. This thermal conductivity value is in the range of other silica aerogels and consistent with the low gravimetric density of 0.15 g cm–3 for the samples. The film is also relatively smooth and flat, with an average arithmetic mean roughness of 1.04 μm.

Fractional parabolic two-step model and its accurate numerical scheme for nanoscale heat conduction

Simulation of nanoscale heat transfer phenomena has attracted great attention, particularly the nanoscale heat conduction induced by ultrashort-pulsed laser heating. In this article, we present a nanoscale fractional parabolic two-step model and obtain an accurate numerical scheme for nanoscale heat conduction in metals. The model is obtained by introducing the Knudsen number (Kn) and the fractional-order derivative in time to the original parabolic two-step energy transport, and then coupling them with the Kn dependent and temperature-jump boundary condition. The numerical scheme is developed based on the fourth-order compact finite difference method and the L1 approximation for fractional derivatives. The well-posedness of the model, and the stability and convergence of the scheme are analyzed theoretically. We finally test the accuracy and applicability of the new model and the obtained numerical method by two examples. By changing values of the Knudsen number and fractional-order derivative as well as the parameter in the boundary condition, the simulation could be a tool for analyzing the nanoscale heat conduction in porous media such as porous thin metal film exposed to ultrashort-pulsed lasers.

Thickness determination of porous Pt cathode thin film capped by atomic layer-deposited alumina for low-temperature solid oxide fuel cells

This study investigated the effects of the apparent thickness of porous Pt cathode thin films thermo-mechanically stabilized by an atomic layer-deposited (ALD) alumina capping agent on effective electrical conductivity and electrochemical performance. Four-point probe resistance measurements revealed that a 120 nm-thick porous Pt film exhibits a relatively high electrical conductivity of 9.2 × 103 S/cm. Cathode reaction resistance measurements by means of alternating current impedance spectroscopy (ACIS) analysis show that ALD alumina can act as a thermo-mechanical stabilizer for a 120 nm-thick porous Pt cathode film. The ACIS analysis results for solid oxide fuel cells (SOFCs) with porous Pt cathode thin films of various thicknesses showed that a 120 nm-thick porous Pt cathode film is thermo-mechanically stabilized by the conformal coating of an ALD alumina capping agent. The iR-free polarization curves show that an ALD alumina-capped 120 nm porous Pt cathode film-embedded SOFC delivers ~65% higher power density than an ALD alumina-capped 480 nm-thick porous Pt cathode film-embedded SOFC.

Nanocrystalline cellulose as a biotemplate for preparation of porous titania thin film as a sorbent for thin film microextraction of ketorolac, meloxicam, diclofenac and mefenamic acid

The present study included the procedure of preparing porous titania thin film using a direct nanocrystalline cellulose templating (NCC) as a bio-template. The microextraction applicability of the porous film was investigated by thin film microextraction (TFME) of the nonsteroidal anti-inflammatory drugs (NSAIDs) including ketorolac, meloxicam, diclofenac and mefenamic acid from different types of urine sample. The extracted NSAIDs were analyzed by HPLC-UV. Under optimum conditions, the calibration curves were linear within the range of 1.0–500 µg L−1 (2.0–200 µg L−1 for ketorolac, 2.0–500 µg L−1 for meloxicam, 1.0–200 µg L−1 for diclofenac and 1.0–200 µg L−1 for mefenamic acid). The limit of detection was found to be between 0.2 and 0.5 µg L−1. The calculated intra- and inter-day relative standard deviations RSDs% (n = 3) at concentration level of 10 µg L−1 were less than 6.3% and 6.0%, respectively. Finally, the method was successfully applied to determine selected NSAIDs in urine samples from different human individuals.

Epitaxial Growth and Structural Characterization of Ceria Deposited by Atomic Layer Deposition on High-Surface Porous Yttria-Stabilized Zirconia Thin Films

Yttria-stabilized zirconia (YSZ) is a well-known solid electrolyte material in high-temperature applications that involve the conduction of oxygen ions. One possible way of enhancing the performanc...

Method for manufacturing metal or metal oxide porous thin films having a three-dimensional open network structure through pore size adjustment in a dry process, and films manufactured by said method

Thickness and specific surface area of the film electrode are critical parameters for supercapacitors. The relationship between the thickness and the specific surface area of the film directly affects the capacitance and electrochemical stability performance of super supercapacitors, which virtually affects the contact chance of ion in the electrolyte on the surface of electrode and the ion transport path of electrode. In this paper, the CrN thin films with a thickness of 200–3500 nm are prepared using direct current magnetron sputtering. Atomic force microscopy (AFM) technique is introduced to investigate the relationship between thickness and the specific surface area of the CrN films. The electrochemical performances of CrN electrode with the nanoporousper structure is analyzed in different electrolytes H2SO4, Na2SO4 and NaCl aquous solutions. The specific surface area of the film increases linearly with the film thickness increases. The areal capacitance is also linearly related to the specific surface area. The spurtted CrN film with a thickness of 3370 nm has a specific surface of up to 43.59 cm2 per cm2 footprint area. Its areal and volume capacitances reache to 53.92 mF cm−2 and 650 F cm−3 at 5 mV s−1, respectively. In addition, the areal capacitance of CrN film electrode with 655 nm possesses reaches to 40.53 mF cm−2 for 0.5 M H2SO4 solution, 32.69 mF cm−2 for 0.5 M Na2SO4 solution and 9.17 mF cm−2 for NaCl solution at a scan rate of 5 mV s−1. Furthermore, the CrN film electrode exhibits excellent capacitance retention of 95.3%, 93.8% and 89.9% in H2SO4, Na2SO4 and NaCl electrolytes, respectively, after 2000 cycles. Therefore, the sputtered CrN thin film is an potential electrode material for electrochemical supercapacitors.