Sheet Resistance Of Films Research Articles

Tuning surface morphology of AuNPs film via thiourea as a stable SERS platform for methylene blue

Gold nanoparticles (AuNPs) have been extensively utilized in various fields such as sensors, life sciences, and catalysis. In this study, AuNPs were synthesized using a reduction method and subsequently treated with thiourea in an ethanol-water environment to prepare AuNPs film using a centrifugal deposition method for first time, resulting in the aggregation of the initial small-sized AuNPs into larger microsphere-like structures. The addition of thiourea facilitated the interconnection between AuNPs, ultimately leading to the formation of large stable gold microspheres. The sheet resistance of the AuNP films transitioned from being non-conductive to exhibiting a sheet resistance of 42.6 Ω/sq following thiourea treatment. The transformation from a flat surface to tightly connected particles resembling microspheres was observed from SEM images. The thiourea treatment not only altered the morphological characteristic of the AuNPs films but also significantly increased the number of scattering sites on their surface, leading to a substantial enhancement in the Raman scattering effect for methylene blue. This structural configuration also improved the electronic conduction and stability of the treated AuNPs films. Consequently, these findings suggest that AuNPs have promising application prospects in surface-enhanced Raman scatting (SERS), as well as in flexible electronics, catalysis, adsorption, and energy fields.

Al-Mg co-doped TiO2 thin film as a promising ETL for perovskite solar cells: An experimental and DFT investigation

Solar cells offer a potential solution to the energy crisis, and perovskite solar cells are the latest frontrunner. However, low electrical conductivity of TiO2 ETL serves as a bottleneck to its efficiency. In this study, Al-Mg co-doped anatase thin films are prepared by one-step spin coating method and then characterized to tackle this problem. XRD results show that doping leads to smaller crystallite size and decreased interplanar spacing, but increases the lattice strain and dislocation density. AFM images reveal that Al-Mg co-doping increases surface roughness. Surface morphology of the co-doped film is good, covering the whole substrate uniformly without any pinholes. XPS results ensure that the desired composition is achieved. UV–vis spectroscopy data show that optical bandgap increases with Al-Mg co-doping, leading to the highest bandgap for Ti0.87Mg0.1Al0.03O2, which also has the highest transmittance peak, reaching 90 % in the visible region. Urbach energies are also calculated to get a better estimate of the effective bandgaps. Band edge positions are calculated using Mulliken’s electronegativity, demonstrating improved band alignment due to Al-Mg co-doping. The bandgap trend is further corroborated with DFT + U simulations, which show that calculated bandgaps match the experimentally obtained optical bandgaps. Additionally, density of states reveal that Ti 3d orbital dominates the conduction band and O 2p orbital dominates the valence band, with hybridization taking place between different orbitals. Four-point probe test demonstrates that Al-Mg co-doping leads to a consistent decrease in sheet resistance of the thin film. Better band alignment and higher visible light transmittance combined with enhanced conductivity indicate that Al-Mg co-doped anatase thin film has high potential as an ETL for perovskite solar cells.

Accelerating densification of the terminal electrode with improved adhesion by sodium ions doping for MLCC copper paste

Glass frits effectively facilitate the sintering densification to produce high-density terminal electrodes, crucial for achieving high reliability of MLCC (Multilayer Ceramic Capacitors) devices. However, manufacturing terminal electrodes with high density and strong adhesion under low-temperature sintering condition still has enormous challenges. Herein, Na2O–BaO–ZnO–B2O3–SiO2 glass has been fabricated for low temperature sintering copper paste. We demonstrate that the densification degree and adhesion strength of the terminal electrode can be notably optimized by adjusting the Na2O content in the glass frit. The doping of Na+ in glass effectively improves the wettability of the melt on the copper substrate and the surface tension of the glass melt, enhancing the capillary force in the liquid phase sintering process. The rate of electrode densification is accelerated by the increase in capillary force, thus reducing the sheet resistance of copper film from 4.52 to 4.30 mΩ/□. Furthermore, with the increase in the Na+ content, the work of adhesion between glass and ceramic gradually increases, which effectively enhances the shear strength of the electrode from 19.66 MPa to 29.55 MPa. Our work provides novel insights for the design of glass compositions in the field of terminal paste.

Novel one-dimensional/two-dimensional composite films: Ag nanowires/ZnO nanowalls

We synthesized novel Ag nanowires/ZnO nanowalls composite films successfully, which integrated the beneficial characteristics of one-dimensional Ag nanowires and two-dimensional ZnO nanowalls. And the resulting Ag nanowires/ZnO nanowalls composite films exhibited outstanding photoelectric properties and enhanced light trapping abilities. The evenly distributed and interlaced Ag nanowires/ZnO nanowalls composite structures were clearly observed. By measuring the total transmittance (TT), diffuse transmittance (DT) and sheet resistance of the composite films, it can be seen that the haze value at 550 nm is 0.26, and the sheet resistance value is 42.5 Ω/sq. These indicated that the photoelectric and light trapping properties of the Ag nanowires/ZnO nanowalls composite films were enhanced significantly compared with those of the simplex films.

Effect of Sheet Resistance of Indium Tin Oxide Films on Thermal Management in Optoelectronic Devices

Effect of Sheet Resistance of Indium Tin Oxide Films on Thermal Management in Optoelectronic Devices

A study on the fabrication procedure for a high-D/Ti-ratio-deuterated-titanium film on the disk-type neutron generator target

This study aims to present thin film deposition and deuterium adsorption procedure to fabricate disk-type targets with high D/Ti values for a neutron generator and increase their lifespan. The neutron target consists of a titanium thin film with hydrogen loading, and a copper substrate for heat removal. We optimized the incident deuterium ion beam energy and thin film thickness using Geant4 simulations. Additionally, we calculated the expected neutron yield under the optimized conditions. The hydrogen adsorption conditions were optimized by comparing the H/Ti results as per hydrogen adsorption temperature and loading time using titanium foils of different thickness values. Hydrogen (or deuterium) adsorption ratio is strongly influenced by the surface condition and the deposition conditions of the thin film. A titanium film was deposited in various conditions of plasma DC power and substrate temperature. The quality of the thin film was evaluated through surface roughness evaluation and thin film sheet resistance for each deposition conditions. Subsequently, the hydrogen adsorption results were compared according to the quality of the thin titanium films, and the thin titanium film deposition conditions with the highest hydrogen adsorption ratio were confirmed. The selected conditions were applied to conduct deuterium adsorption. In conclusion, this study underscores the critical relationship between thin film quality and hydrogen (or deuterium) adsorption ratio, reinforcing the importance of optimizing thin film deposition parameters for the design of neutron generator disk-type targets with high quality of film and extended lifespan.

Multi-level phase-change behaviors of Ge2Sb2Te5/Sb7Se3 bilayer films and a design rule of multi-level phase-change films

Multi-level phase-change (MLPC) memory can not only further raise the storage density of high-density phase-change memory, but also have significant applications in neuromorphic computing. However, acquisitions of MLPC materials are very challenging. MLPC is only observed in a small number of phase-change materials and can’t be designed determinately because the mechanism of MLPC emergence has been understood incompletely. Here, we investigate phase-change behaviors of six Ge2Sb2Te5(x nm)/Sb7Se3 (60-x nm) bilayer films with x = 5, 10, 15, 20, 35, and 50. Three-level phase-change memory is observed for five bilayer films with x < 50, but not for one with x = 50, revealing the dependence of MLPC memory on the thickness ratio of two constituent layers composing bilayer films. A parallel resistance model is proposed to describe the measured sheet resistance of bilayer films and can be used to explain the thickness-ratio dependence of three-level phase-change memory very well. Subsequently, a design rule for MLPC memory films is given out unambiguously. Based on the parallel resistance model, MLPC memories are simulated for bilayer and trilayer films. Three-level memory indeed appears in bilayer films only when the design rule is met, confirming the validity of our design rule. Four-level memory is predicted in trilayer films as the design rule is obeyed.

Scalable one-step synthesis of reduced graphene oxide: Towards flexible transparent conductive films and active supercapacitor electrodes

The reduced graphene oxide (rGO) thin films have attracted much attention in flexible electronic devices and supercapacitors (SCs). However, the chemical reduction mechanism of GO needs to be clarified, and the one-step process at low temperatures for preparing high-quality rGO thin films from GO dispersions is still blank in the research field. Here, we propose a one-step operation to spray GO dispersions onto substrate or current collector under a hydroiodic acid (HI) atmosphere while simultaneously achieving the preparation of rGO thin films. This pioneering metal-free, transfer-free, fast, low-temperature, environmentally friendly, and scalable spraying technology enables large-scale production of high-quality rGO. This method realizes the preparation of highly conductive and high transmittance rGO thin films on flexible polyimide and polyethylene terephthalate substrates, as well as the preparation of rGO thin films on current collectors as SCs electrodes. Density functional theory calculations show that oxygen-containing functional groups on the surface of GO exhibit a stronger adsorption energy for HI, and have a low energy barrier during reduction by HI. Ab initio molecular dynamics simulated the possible reduction reaction path between GO and HI at 90 °C, demonstrating that HI molecules can effectively reduce GO. Furthermore, the sheet resistance of the transparent conductive film created using the method developed in this study reaches approximately 1000 Ω/sq (80 % transparency), and the specific capacitance of the SCs electrode film created in this method is 433.2 F/g (5 mV/s, 1 M H2SO4). Our study not only validates the efficacy of the one-step synthesis method for rGO thin films but also provides theoretical insights into the underlying reaction mechanism. This work holds significant promise for advancing applications in various electronics by facilitating large-scale production of high-quality rGO thin films.

Nitrogen doped single layer graphene for CZTS-based thin film solar cells

CdS thin films are commonly utilized as a buffer layer in chalcopyrite thin-film solar cells. However, due to the toxic nature of Cadmium (Cd), ongoing efforts are being directed towards exploring alternative options. In this contribution, doped graphene film with remarkable optical and electrical properties has been introduced for the first time as an alternative buffer layer, replacing CdS in CZTS thin-film solar cell application. In this study, nitrogen-doped graphene (N-doped graphene) film was utilized as a substitute buffer layer in the CZTS thin-film solar cell structure, replacing the conventional CdS thin film. For comparative analysis, CZTS/N-doped graphene and CZTS/CdS traditional solar cell structures were fabricated and separately characterized. The CZTS thin films produced were examined through EDX, XRD, SEM, Raman, optical transmission and PL spectroscopy measurements. According to performed analyses, the Cu-poor and Zn-rich kesterite CZTS thin films exhibited a uniform and dense polycrystalline microstructure as observed in surface and cross-sectional SEM images. XRD spectra of the kesterite CZTS thin film displayed predominant peaks corresponding to the (112), (220/204), and (312/116) diffraction planes of the kesterite CZTS phase. Raman spectra showed a dominant peak at ∼336 cm−1 associated with the kesterite CZTS phase. PL emission spectra indicated transitions from the conduction band to defect levels. The CVD-grown doped graphene film exhibited a 3.43 I2D/IG ratio and a 25 cm−1 FWHM of the 2D peak, indicating a single-layer graphene according to Raman analysis. Permanent nitrogen doping with a 2% atomic concentration was confirmed by XPS measurement. The optical transmission measurement of the single layer doped graphene film showed a 95% transmittance value. Nitrogen doping was contributed to decrease the sheet resistance of the graphene film. The Glass/Mo/CZTS/N-doped graphene/i-ZnO/ITO/Al solar cell displayed a VOC of 0.267 V, JSC of 24.6 mA/cm2, FF of 36.46, and η of 2.37%, showing higher FF and Jsc values but lower conversion efficiency compared to the Glass/Mo/CZTS/CdS/i-ZnO/ITO/Al traditional solar cell structure. Hence, the superior working function and transparency properties position the N-doped graphene film as a competitive buffer layer for use in CZTS-based thin-film solar cells.

Improved electrical conductivity of silver nanowire film by adding silver nanoparticles

Silver nanowire (AgNW) film is a promising transparent conductive component for optoelectronic devices such as display applications. Improving the electrical conductivity of AgNW film without scarifying optical transmittance is a technical challenge. In this work, an effective route for reducing sheet resistance of AgNW film with maintaining optical transmittance is proposed. By adding silver nanoparticles (AgNPs) around the intersections of AgNWs, sheet resistance of AgNW film is dramatically decreased more than 78.7%. Meanwhile, transparency of the as-prepared AgNW film maintains the same level. The mechanism of conductivity improvement is also discussed.

Influence of Bulk Defect Density on the Efficiency of CIGS Based Photovoltaic Cell/Solar Cell

In CIGS-based thin-films, bulk defects are believed to represent disturbances either in a regular, periodical arrangement within the atoms or within the crystalline media which influence sheet resistivity. In this study, first a resistivity measurements were carried out on CIGS thin films using the Van Der Pauw technique. Then, a comparison between two Van Der Pauw four-point measurement configurations (aligned and square) were done which showed that the square configuration was the most appropriate configuration that can be recommended to measure thin film sheet resistance of CIGS films. Finally, a numerical simulation using SCAPS-1D software was used to study the influence of bulk defect density in a CIGS films as an absorber layer in a model photocell. Using the simulated data, three operating zones for the model photocell were identified depending based on the concentration of its bulk defect density. The influence of bulk defects on thickness, band gap and doping were then analyzed. It was revealed that when the bulk defect density was less than 5×1013 cm-3 for an absorber of thickness in the order of over 3 μm, a band gap between 1.3 eV-1.4 eV and acceptor density of 1016 cm-3were the optimal operating conditions for the model photocell. It was concluded that the CICS layer used as an absorber can be improved if its bulk defect density is tuned to optimal levels.

A new electrostatic dust removal method using carbon nanotubes transparent conductive film for sustainable operation of solar photovoltaic panels

Electrostatic dust removal has the advantages of energy saving, high efficiency, and controllability, and has become the preferred dust removal solution for solar photovoltaic (PV) panels in recent years. This paper investigates a new electrostatic adsorption dust removal method for solar PV panels based on the electrostatic dust removal effect of carbon nanotubes (CNTs) transparent conductive films. In the sheet resistance range of 500–1×105 Ω/□, the electrostatic dust removal effect of CNTs transparent conductive films has little relationship with the film sheet resistance, and when the electric field strength in the dust removal area is 6 kV/cm, the final dust removal rate of different films can reach more than 98.6 %, and the power generation efficiency of the PV panels can reach 94–97 % of that of the ordinary PV panels in the surface clean state after dust removal. The influence of the environment on the dust removal effect is mainly reflected in the relative humidity. When the relative humidity of the dust removal environment is 70 %, it shows the optimal dust removal effect, and the electric field strength required for the dust particles to jump is the lowest, which is 2.46 kV/cm. The highest dust removal efficiency can be achieved by using a metal plate with a lower surface curvature of 1/9.08 cm−1, and the final dust removal rate can reach 98.92 %. The research results are of great significance for further developing electrostatic dust removal technology in the solar PV panel dust removal field.

Magnetic domain structure and magneto-transport properties of laser ablated Co40Fe40B20 thin films

We report the magnetic domain structure, and electrical and magnetoresistance properties of laser ablated Co40Fe40B20 (CoFeB) (6 to 36 nm) thin films deposited on SiO2 / Si(001) substrates. Magnetic force microscopy performed on annealed CoFeB thin films revealed larger magnetic domains, which are formed due to strong exchange coupling between the grains. The temperature-dependent sheet resistance of as-deposited thin films revealed that the observed non-metallic behavior is due to intragrain-tunneling and SiO2 inclusions in the amorphous matrix. The metallic behavior of annealed CoFeB thin films is due to electron scattering from grain boundaries and granularity correlated to the formation of nano-crystallites. Thickness and field-dependent magneto-transport studies show higher magnetoresistance values for thinner annealed CoFeB films due to more scattering events upon crystallization, which is consistent with the granular nature of the annealed thin films.

INFLUENCE OF N2 FLOW RATE ON THE PROPERTIES OF VANADIUM NITRIDE THIN FILMS DEPOSITED BY REACTIVE DC MAGNETRON SPUTTERING

Vanadium nitride (VN) thin films have been deposited on silicon wafer substrates by reactive DC magnetron sputtering with varied nitrogen (N2) flow rates from 5.0 to 8.0 sccm without substrate heating. The crystallinity, morphology, and optical properties of the prepared VN films were investigated by gracing-incidence X-ray diffraction (GIXRD), field emission scanning electron microscope (FE-SEM), and UV-Vis-NIR spectrophotometer, respectively. The GIXRD pattern shows that the crystal structure of the films is consistent with the face-centered cubic VN structure. An increase in N2 led to a decrease in film thickness and sheet resistance. On the contrary, the reflectance percentage tends to increase with the increase of N2 flow rate. [Copyright information to be updated in the production process].

Influence of Deposition Parameters of ITO Films on the Performance of HJT Solar Cells

TCO (transparent conductive oxide) films are widely used in solar cells due to the characteristics of transparency and conductivity. In this paper, ITO (indium tin oxide) transparent conductive films are prepared on common slides by DC magnetron sputtering, and the preparation process and characteristics of ITO films are studied. The target for sputtering is ITO, with the mass ratio of In203 and Sn02 was 90% : 10%. The sheet resistance, carrier concentration, and carrier mobility of ITO films are measured and analyzed by a UV-Vis spectrophotometer, four-point probe, and Hall effect measurement system. By changing the oxygen content, deposition temperature, and sputtering power to studied the effects on the light transmittance and electrical conductivity of the ITO films, further studied the effects on the HJT (heterojunction with intrinsic thin film) solar cells, and finally determined the appropriate preparation parameters. Results show that the resistance is 6 . 4 ∗ 10 − 4 Ω • cm , the light transmittance is beyond 90.6%, efficiency is 23.78%, and bifacial ratio is 84% when oxygen content is 2.2%, sputtering power is 3 kw, and deposition temperature is 190°C.

Fast, facile and thermal damage free nanowelding of Ag nanowire for flexible transparent conductive film by pressure-assisted microwave irradiation

A fast and straightforward fabrication process for producing a robust, flexible, and transparent conductive film was demonstrated using nanowelding of Ag nanowires through pressure-assisted microwave irradiation. This innovative process effectively reduces the sheet resistance of the Ag nanowire transparent conductive film without causing any thermal distortion to the PET substrate. The microwave irradiation induces nanowelding between Ag nanowires, leading to a decrease in sheet resistance by forming nanowelding junctions. This selective heating of Ag nanowires further enhances the reduction in sheet resistance. Additionally, the application of pressure-assisted microwave irradiation allows the Ag nanowires to be embedded into the PET substrate, resulting in the formation of a robust film capable of withstanding cycling bending stress. The pressure-assisted microwave irradiation process proves to be a strong fabrication method for creating Ag nanowire transparent conductive films, especially when dealing with thermally weak substrate materials.

Aluminum and Molybdenum Co-Doped Zinc Oxide Films as Dual-Functional Carrier-Selective Contact for Silicon Solar Cells.

Aluminum-doped zinc oxide (AZO) is considered as a promising candidate as transparent conductive oxide (TCO) for silicon heterojunction solar cells due to its high carrier density, nontoxic nature, and low cost. Herein, it is presented that the transparency of the AZO film can be optimized through co-sputtering of AZO and molybdenum oxide (MoOx). Furthermore, aluminum and molybdenum co-doped zinc oxide (MAZO) can be used as both the TCO layer and electron-selective contact (ESC) for silicon heterojunction solar cells. The surface morphology, cation oxidation state, and optical and electrical properties of all MAZO films are characterized. It is found that the transmittance of all MAZO films is significantly increased at a wavelength of 450-800 nm due to MAZO with a stronger Zn-O bond and a wider band gap. The conductivity of MAZO films is approximate to AZO films at a low MoOx target deposit power (50 W), and the sheet resistance of MAZO films increases significantly by increasing the deposition power up to 100 W. Finally, the optimized MAZO films are used as TCO and ESC for silicon heterojunction solar cells, showing a power conversion efficiency of 19.58%. The results show an effective stage to improve the optical properties of AZO through co-doping and the possibility of applying MAZO as a dual-functional layer for silicon solar cells.

High-Adhesion Ag Film with Enhanced Electromagnetic Shielding Performance via Post-Treatment of a Polydopamine Adhesive Layer.

Low adhesion limits the application of the conformal metal coating based on metal-organic complexing deposition (MOD) ink in electromagnetic interference shielding with an ultrathin thickness and excellent electromagnetic shielding performance. Here, the mussel-inspired polydopamine (PDA) coating with double-sided adhesive characteristic was used to modify the substrate surface, and a high-adhesion silver film was prepared by spin-coating MOD ink on the PDA-modified substrate. The surface chemical bond of the deposited PDA coating was found to change with the exposure time under air in this work, and three post-treatment methods were carried out on the PDA coatings, including exposure to air for 1 min, exposure to air for a day, and oven heat treatment. The influences of such three post-treatment methods of PDA coating on the structure of the substrate surface, the silver film adhesion property, the electrical property, and the electromagnetic shielding property were studied. The adhesion of the silver film was effectively enhanced up to 20.45 MPa by controlling the post-treatment method of the PDA coating. The PDA coating was found to increase the sheet resistance of the silver film and to absorb electromagnetic waves. By optimizing the deposition time and the post-treatment condition of the PDA coating, superior electromagnetic shielding effectiveness up to 51.18 dB was obtained with a thin silver film of 0.42 μm. The introduction of the PDA coating improves the applicability of the MOD silver ink in the field of conformal electromagnetic shielding.

Temperature-Dependent Sheet Resistance and Surface Characterization of Thin Copper Films Bonded to FR4 Composite under Mechanical Vibrations

Electrical boards, also called printed circuit boards, constitute the basis of most electronic devices. These boards are mainly fabricated of thin copper films bonded to fiber epoxy laminates, such as FR4. Being the most important functional component of these devices, they sometimes undergo mechanical stresses such as shock and vibration during transport and operation that can induce electrical failure and malfunction; hence, studies addressing the effects of vibrations on their electrical properties have important applications. In this paper, small cantilever samples made of bare copper bonded to FR4 with three isolated rectangular zones were studied to analyze, for the first time, variations in electrical properties such as sheet resistance and resistivity before and after 200 k, 500 k, and 800 k vibration cycles at three different temperatures (25, 35, and 45 °C). A significant rise in resistance equivalent to 1657% of the initial value was observed from 0 to 800 k vibration cycles. These changes were accompanied by a 95% decrease in conductivity, from 4.1 × 107 to 2.3 × 106 S/m, whereas very little change in the electrical properties was observed due to temperature rise. Surface analysis by ESEM showed cracks ~1 µm in width and several millimeters in length with a crack density of ~8 cracks per mm after 800 k cycles. The surface composition (100% copper) was not altered even upon a high number of vibration cycles, and static drop contact angle measurements of 117–119 degrees indicated an increase in the hydrophobicity of the surface attributed to increased surface roughness and the accumulation of very small air bubbles on the cracks.

Fluorine-Doped Tin Oxide Thin Films with High Surface Conductance and Low Transparency for Boosting Performance in Dye-Sensitized Solar Cell Applications

Transparent conductive oxide films, like fluorine-doped tin oxide (FTO), are needed for electrochemical devices. FTO films are attractive due to their cost-effectiveness and high-temperature tolerance. Generally, solar cell fabrication requires high transmittance and low-conductivity FTOs. However, achieving both simultaneously poses a fundamental challenge. This study investigates the impact of FTO layer thickness, sheet resistance, transparency, and film morphology on optimizing the performance of dye-sensitized solar cells. To achieve this, a precursor solution containing SnCl4·5H2O and NH4F in isopropanol is sprayed onto a soda-lime glass substrate at 500 °C to form FTO films. The film thickness is varied by repeating the spray cycles. By increasing the number of spray cycles, the sheet resistance of the FTO film improves to ∼1.20 Ω □–1 with the expense of transmittance. The achieved very low sheet resistance of ∼1 Ω □–1 (∼3.54 × 10–4) Ω cm resistivity for the FTO film confirms the promise of this sequential spray pyrolysis technique in preparing highly conductive inert electrodes for various applications. Furthermore, DSCs with low transparency and sheet resistance showed higher-energy conversion efficiencies, challenging the current prerequisite of the requirement of high transmittance. The best efficiency (5.14%) is achieved with FTO films having a 34.2% transmittance and a 3.27 Ω □–1 sheet resistance, outperforming standard FTO films (4.74%) with a 10 Ω □–1 sheet resistance and an ∼83% transmittance. The results indicate that the transparency of FTO is not a dominant factor and carefully controlled light scattering and electrical properties in translucent FTO films would lead to the realization of dye-sensitized solar cells that deliver superior efficiency.