Decrease In Resistivity Of Films Research Articles

Ultrasound-assisted facile and green preparation of Ag nanoparticle conductive ink for printing electronics

The development of low-cost, high-efficiency, and environment-friendly methods for the preparation of Ag nanoparticle (NP) conductive inks is key to promoting the application of such inks for printing flexible electronic components. This article presents an effective method for preparing a AgNP ink by reducing silver compounds in a polyol solution with ultrasonication. When the silver solution was ultrasonicated at 640 W, 21-nm AgNPs were readily produced within 5 min, and the particles grew considerably to 53 nm as the reaction was continued for 15 min. Thereafter, the NP size increased marginally with further increase in reaction time. When the reaction was conducted for a fixed duration of 15 min and the ultrasonic power was increased from 480 to 760 W, the AgNP size decreased from 63 to 48 nm. During ultrasonication, the bubble eruption in the solution generates large temperature and pressure gradients, inducing the rapid reduction of the Ag(I) to Ag(0). Printing experiments revealed that the synthesized AgNP ink has good inkjet printability. During the sintering of the printed film, the bridge connections between large particles increased and the interparticle voids decreased gradually, resulting in a decrease in film resistivity. A relatively low resistivity of 40×10−5 Ωcm was obtained when the flexible AgNP pattern was heated at 250 °C for 80 min. The facile synthesis process and the favorable conductive properties of the obtained ink render this preparation method promising for the low-cost production of flexible electronics.

Doping and precoating by Cu-metal and annealing impacts on some physical properties and applications of MnS thin films

We prepared thin films of manganese sulfide (MnS) using a thermal evaporation technique. These films were pre-coated and doped with Cu ((MnS)1-xCux, x = 0.05 g). A lot of work was done on these films using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), UV/VIS/NIR spectrophotometry, and a two-probe approach to figure out their structure, shape, optical properties, and electrical properties. We investigated various factors including the optical energy gap (Eg), refractive index (n), extinction coefficient (k), Urbach energy (Eu), dielectric constants (εr), dispersion parameters, activation energy (ΔE), mobility, photocatalytic analysis, and Seebeck coefficient. The XRD analysis showed that the thin films were amorphous. The direct optical energy gaps of the pure, Cu pre-coated layer, and Cu-doped MnS films were measured at 3.17 eV, 1.88 eV, and 2.45 eV, respectively. Annealing the films at different temperatures showed normal refractive index dispersion in the NIR region. The addition of copper, both as a pre-coating layer and as doping, resulted in a decrease in film resistivity, indicating their semiconducting nature. FE-SEM analysis provided valuable insights into the morphology of the thin films, revealing a uniform and smooth surface. The electrical characteristics showed that film resistivity decreased with copper addition, confirming enhanced conductivity. These properties hold significance in the development of absorber layers for second-generation solar cells, thermoelectric characteristics, and photocatalysis applications.

Improve physical properties of zirconium doped strontium sulphide for optoelectronic purpose

The electrochemical deposition was used to synthesize zirconium-doped strontium sulphide materials at varying dopant concentrations of 0.01 to 0.03 mol. The surface micrograph of the zirconium doped films is well structured on the surface of the FTO used for the synthesis without any crack or lattice strain. The spectrum is polycrystalline with a cubic structure and a prominent peak at (111) orientation for SrS film. At the introduction of the zirconium dopant 0.01 mol, the peak intensity increases with a prominent peak at (211) which indicate acceptance of zirconium dopant in the precursor and as the dopant concentration rises the peak intensity decreases which depicts that a higher concentration of zirconium reduces the peak intensity of the films. The Williamson-Hall plot's slope increases as the dopant concentration increases. The materials exhibit a thickness increase of 121.32 to 126.13 nm and a decrease in film resistivity from 1.12 × 109 to 1.32 × 109 O.m, which further led to an increase in conductivity from 7.57 × 108 to 8.26 × 108 S/m. The bandgap energy of SrS is 1.50 eV while SrS-doped zirconium is 1.35 eV–2.52 eV.

Photocatalytic activity of the TIO2/Ag/rGO nanocomposite

The paper presents the results of a study of the photocatalytic activity of films formed by titanium dioxide nanorods doped with silver nanoparticles and reduced graphene oxide. The obtained nanocomposite materials were studied by optical spectroscopy, scanning electron microscopy, X-ray diffractometry, and Raman spectroscopy. The photocatalytic activity of the samples was evaluated by generating a photocurrent when the surface was illuminated by a modulated light source of a xenon lamp. In addition, the photocatalytic activity of the samples was evaluated by the degradation of the methylene blue dye, which is a model. It was found that the introduction of silver nanoparticles and reduced graphene oxide into the pores of films made of titanium dioxide nanorods leads to an increase in the spectral sensitivity of the sample in the region of 400-500 nm. The increased sensitivity of the sample to visible light leads to an increase in photocurrent generation and is 2.3 times higher than that of the original sample. Degradation of the methylene blue dye after 100 minutes of irradiation in the presence of a TiO2/Ag/rGO sample was 19 %. This is 3 times higher than in TiO2 nanorods films and 2.3 times higher than TiO2/Ag films. The results of the conducted studies have shown that the improvement of photocatalytic activity is associated with a decrease in film resistance, an expansion of spectral sensitivity and an increase in the surface area of the nanorods.

Role of Ambient Hydrogen in HiPIMS-ITO Film during Annealing Process in a Large Temperature Range.

Indium tin oxide (ITO) thin films were prepared by high power impulse magnetron sputtering (HiPIMS) and annealed in hydrogen-containing forming gas to reduce the film resistivity. The film resistivity reduces by nearly an order of magnitude from 5.6 × 10−3 Ω·cm for the as-deposited film to the lowest value of 6.7 × 10−4 Ω·cm after annealed at 700 °C for 40 min. The role of hydrogen (H) in changing the film properties was explored and discussed in a large temperature range (300–800 °C). When annealed at a low temperature of 300–500 °C, the incorporated H atoms occupied the oxygen sites (Ho), acting as shallow donors that contribute to the increase of carrier concentration, leading to the decrease of film resistivity. When annealed at an intermediate temperature of 500–700 °C, the Ho defects are thermally unstable and decay upon annealing, leading to the reduction of carrier concentration. However, the film resistivity keeps decreasing due to the increase in carrier mobility. Meanwhile, some locally distributed metallic clusters formed due to the reduction effect of H2. When annealed at a high temperature of 700–800 °C, the metal oxide film is severely reduced and transforms to gaseous metal hydride, leading to the dramatic reduction of film thickness and carrier mobility at 750 °C and vanish of the film at 800 °C.

Electrical properties and spectroscopic ellipsometry studies of covellite CuS thin films deposited from non ammoniacal chemical bath

In this paper, CuS thin films with good adherence and of different thickness in the range of 450–800 nm were prepared by chemical bath deposition method without using ammonia. The precursor solution was made by mixing copper (II) chloride, sodium thiosulfate, dimethylthiourea and deionized water. The bath temperature was kept at 65 °C and deposition time was varied from 3 h to 6 h with an increment step of 1 h to obtain different film thickness. A post annealing step in N2 atmosphere at 200 °C for 30 min was employed to improve the crystallinity and grain recrystallization of the films. X-ray diffraction and Raman scattering analysis revealed a hexagonal covellite structure in the films. However, the formation of secondary phases in trace amount and lower degree of crystallinity were detected for lower deposition time. FESEM images showed the formation of elongated needle-like particles which were distributed uniformly over the surface. The average length of the particles are in the range of 450–500 nm. The effect of deposition time on the optical properties was evaluated and the optical band gap values were found to be in the range of 2.26–2.55 eV. Variable-angle spectroscopic ellipsometry studies were performed to determine the optical constants including inter-band transitions in CuS films. The dependence of deposition time on the electrical properties of the films were evaluated by Hall Effect measurement showing a systematic decrease in film resistivity with increased deposition time.

Investigation of growth characteristics, compositions, and properties of atomic layer deposited amorphous Zn-doped Ga2O3 films

Diethylzinc and H2O were used as the precursors for the thermal atomic layer deposition (TH-ALD) of ZnO deposition while the trimethylgallium and O2 plasma were used as a reactant for the plasma-enhanced atomic layer deposition (PE-ALD) of Ga2O3, respectively. The Zn-doped Ga2O3 (ZGO) films were fabricated by a combination of PE-ALD of Ga2O3 and TH-ALD of ZnO at a low temperature of 200 °C. The results show that as-deposited ZGO films were amorphous while ZnO with a crystalline structure. XPS results indicate that the Zn content in ZGO films increased from 9.70 to 24.65 at.% with the cycle ration of Ga2O3 with respect to ZnO decreasing from 7:1 to 3:1 while the oxygen vacancy increased from 27.65% to 37.93%. The rise in Zn doping contents is also accompanied by significant variations in the morphological, electrical, and optical properties of the ZGO films, including a decrease of film density and resistivity, an increase of RMS roughness, a strong transmittance in the ultraviolet-visible (UV–vis) area, and a widening of the band gap from 4.64 to 5.25 eV. These findings help deposit ZGO films with desired structure and properties for electronic device applications.

Temperature annealing effect on ITO film

In the work we investigate processing and optoelectronic properties of ITO films coated on glass and Si substrates using RF magnetron deposition. Temperature annealing modifies the properties of the ITO film that affects the final characteristics of devices where they are used. It was discovered that a great change of characteristics is observed by annealing under the temperature of 200°C: the increase of the transmission up to 90% and decrease of film resistance from 160 to 40 Ohm·□−1. The ρc is 4·10−3Ω·cm2 for Au and 2·10−3Ω·cm2 for Ag contacts.

Surface characterization of the commercially pure titanium after hydrogen charging and its electrochemical characteristics in artificial seawater

The surface film on hydrogen-charged commercially pure titanium and its influence on the electrochemical behavior in artificial seawater was studied in detail using surface characterization techniques and electrochemical measurements. The results revealed that with the increase in charging current density, the original surface film underwent three stages of evolution. When the charging current density was <20 mA/cm2, the surface film just expanded and bulged; when the current density exceeded 30 mA/cm2, the surface film was significantly destroyed and began to fall off; when the current density reached to 50 mA/cm2, the surface film fully peeled off and was replaced by a new layer of loose film. Accordingly, the composition of the surface film transformed from titanium oxides to a mixture of titanium oxides and titanium hydrides, and finally to entirely titanium hydrides. Under the influence of hydrogen charging, the corrosion resistance of the surface film in artificial seawater sharply decreased, showing a significant increase in anodic current density, decrease in surface film resistance, as well as a tendency toward early failure of the surface film at a lower potential.

Impact of Hydrogen Passivation on Electrical Properties of Polysilicon Thin Films

The effect of hydrogen passivation and heat treatments on the electronic activity at grain boundaries in thin films of polysilicon deposited by LP-CVD (Low Pressure Chemical Vapor Deposition) has been studied. The results obtained have shown that the introduction of hydrogen into polysilicon thin films doped with arsenic ions increases the concentration of free carriers, reduces the resistivity and lowers the density of trap states at the grain boundaries. Free carriers concentration improved by almost 10% at the annealing temperature of 1000 °C. In addition, it was found that the effect of hydrogen is much more pronounced for low temperature heat treatment before doping compared to the effect at the higher temperature. Moreover, the increase in free carrier concentration and the decrease in resistivity of polysilicon thin films with the increase in the annealing temperature has been observed.

Low resistivity HfNx grown by plasma-assisted ALD with external rf substrate biasing

Application of an external rf substrate bias during the H2 plasma half cycle leads to a significant decrease in film resistivity resulting from a major reduction of O content and an increase in the Hf3+ oxidation state fraction in HfNx thin films

Graphene-based humidity sensors: the origin of alternating resistance change

The response of a graphene-based humidity sensor is considered as a function of film structures. Analysis of the resistance changes due to water molecule adsorption on the graphene or multi-layer graphene (MLG) surface is performed for films with different structures and resistivities from hundreds of ohms/sq to hundreds of kilo-ohms/sq. The results revealed possible increase, decrease and non-monotonous behavior of resistance with changes in film structure. Adsorption of water molecules at grain boundary defects is assumed to lead to an increase in film resistivity due to the donor property of water and the p-type conductivity of graphene. Another type of conductive center with a higher capture cross-section is realized in the case of water molecule adsorption at edge defects in MLG films (the formation of conductive chains with ionic conductivity). If these chains form a continuous network the film resistivity decreases. The result of the competition between the opposite effects of the conductivity compensation and formation of the water-based conductive chains depends on the film structure and determines the response of humidity sensors. Sensor sensitivity is found to increase when only one type of defect determines water adsorption (edge defects or grain boundary defects).

Peculiar behavior of TiO2 tubular structure for water reduction in dark and under natural light exposure

TiO2 tubes were formed by electrochemical anodization process. The electrochemical reduction of water on TiO2 tubular structure (TiO2–TS) at various pH in dark and natural light was investigated by potentiodynamic cathodic polarization, cyclic voltammetry (CV) and impedance spectroscopy analyses. The negative shift in open circuit potential, relatively low Tafel slope and higher exchange current density presented by TiO2–TS under natural light depicted increased electrochemical activity for water reduction. Under light exposure, CV scan showed high cathodic current density with lower overpotential (0.3V) when compared to dark (>0.8V). Furthermore, under natural light, the decrease in charge transfer resistance and oxide film resistance also validated the increase in the electrochemical activity of TiO2–TS towards water dissociation.

Electroless Copper Plating on Liquid Crystal Polymer Films Using Dimethylamine Borane as Reducing Agent

AbstractDimethylamine borane (DMAB) was used in electroless copper plating on liquid crystal polymer (LCP) films. An orthogonal test was applied to optimize the plating condition. With Cu film resistivity as the evaluation index, the optimum plating condition is: 10 g/L of CuSO4 ⋅ 5H2O, 14 g/L of EDTA‐2Na, 6 g/L of DMAB, 9.5 of pH value and 50 °C. As pH value increases, the Cu film resistivity decreases and the depo‐ sition rate increases. As temperature increases, the Cu film resistivity decreases first and then increases with a minimum at 50 °C while the deposition rate increases first and then decreases with a maximum at 50 °C. The decreased Cu film resistivity can be attributed to the occurrence of CuO. The adhesive strength of copper layer to LCP film is constant at pH values lower than 8.5 and decreases slightly with the increase in pH value. As temperature increases, the adhesive strength decreases slightly. The decreased adhesive strength with both pH and temperature may be a result of an increased corrosion attack from the bath to the surface of LCP films. Low Cu film resistivity and high deposition rate as well as high adhesive strength can be obtained using DMAB reducing agent.

&amp;lt;i&amp;gt;In-Situ&amp;lt;/i&amp;gt; Corrosion Monitoring of Scratched Epoxy Coated Carbon Steel in Saturated Ca(OH)&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; with or without 3% NaCl by Scanning Electrochemical Microscopy and Electrochemical Impedance Spectroscopy

The present work is investigated the in-situ monitoring of local corrosion process of scratched epoxy coated carbon steel in saturated Ca(OH)2 with and without 3% NaCl using SECM and correlated with EIS. The results obtained from EIS analysis showed that the corrosion resistance of scratched epoxy coated carbon steel decreases in Cl- containing solution as the increase in wet/ dry corrosion cycles. This was indicated by decrease in film resistance (Rf) and charge transfer resistance (Rct), while the coated steel maintain the resistance values in saturated Ca(OH)2, most of which recovered after drying. The corrosion process was monitored using SECM by setting the tip potential at -0.70 V vs Ag/AgCl, where the consumption of dissolved oxygen occurred at the surface of test sample. The consumption of dissolved oxygen current (I’oxy-c) values was increased during the immersion in a solution with 3% NaCl. However, in wet/dry corrosion cycles, I’oxy-c was decreased due to the coverage of hydroxides/oxides at scratch area which suppressed the consumption of dissolved O2. It was found that the continuous decrease in corrosion was mainly attributed to continuous formation of corrosion products at anodic spots.

Chemical and electrical characterisation of the segregation of Al from a CuAl alloy (90%:10% wt) with thermal anneal

A copper–aluminium (CuAl) alloy (90%:10% wt) has been investigated in relation to segregation of the alloying element Al, from the alloy bulk during vacuum anneal treatments. X-ray photoelectron spectroscopy (XPS) measurements were used to track the surface enrichment of Al segregating from the alloy bulk during in situ ultra-high vacuum anneals. Secondary ion mass spectroscopy (SIMS) indicates a build-up of Al at the surface of the annealed alloy relative to the bulk composition. Metal oxide semiconductor (MOS) CuAl/SiO2/Si structures show a shift in flatband voltage upon thermal anneal consistent with the segregation of the Al to the alloy/SiO2 interface. Electrical four point probe measurements indicate that the segregation of Al from the alloy bulk following thermal annealing results in a decrease in film resistivity. X-ray diffraction data shows evidence for significant changes in crystal structure upon annealing, providing further evidence for expulsion of Al from the alloy bulk.

Influence of Substrate Temperature on the Al and Zr Co-Doped ZnO Thin Films Prepared by RF Magnetron Sputtering

ZnO doped Al2O3and ZrO2(ZAZO) thin films were deposited by the radio frequency magnetron sputtering on substrate temperature with 100°C, 150°C, 200°C, 250°C and 300°C. The surface morphology and electrical properties of the films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and four-probe tester. The results showed that the substrate temperature obviously influenced the grain size of ZAZO films. The ZnO thin film had the largest crystallization orientation for the (002) peak and the smallest FWHM value at substrate temperature of 250°C. As the temperature increasing, the resistance of films gradually decreased till reaching a minimum at 250°C and then rised. Due to the increasing of Al and Zr concentrations into ZnO lattice, the Al ions created an abundance number of free electrons in the ZnO lattice, and in turn, the electrical conductivity increased. In addition, the improvement of film in the crystalline state results in the film resistivity decreases.

Effect of interface structure on the chemical composition and electrical properties of sol–gel-derived LaNiO3 films

In the present work, lanthanum nickel oxide (LNO) thin films are prepared with the sol–gel multilayer coating method. Lattice-matched SrTiO3 (STO) buffer layer is introduced to tailor the film–substrate interface. The effect of interface structure on the electrical properties, microstructure and chemical composition of LNO films is investigated. The results show that the improvement in the interface structure minimizes the effect of interface on the electrical properties of LNO films and leads to a sharp decrease in room-temperature resistivity of LNO films to 570 μΩ cm, comparable to that of the LNO films on single-crystal STO substrate. This is ascribed to the decrease in structural disorder and the concentration of oxygen vacancies in the LNO films.

Effect of dimethyl sulfoxide on the electrical properties of PEDOT:PSS/n-Si heterojunction diodes

Effect of dimethyl sulfoxide (DMSO) on the electrical properties of PEDOT:PSS/n-Si heterojunction diodes has been studied. Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) was deposited on n-type Si wafer using facile process of spin coating. The DMSO content was varied from 0 to 8 vol%. Electrical characterization of these heterojunction diodes as performed using both current–voltage (I–V) and capacitance–voltage (C–V) measurements. All diodes showed rectifying behavior. AFM measurement revealed that the surface became more rough after the DMSO treatment of PEDOT:PSS films. The RMS values were found in the range of 4–6 nm. The resistivity of the PEDOT:PSS films decreased with increase in temperature. The addition of DMSO into PEDOT:PSS solution results in a decrease in resistivity of films by approximately two orders of magnitude. PEDOT:PSS films showed high transmission more than 85% in the entire visible region. Raman spectroscopy indicated effect of the DMSO treatment on the chemical structure of PEDOT chains, suggesting a conformational change of PEDOT chain in the film. An optimal value of DMSO was obtained with 5 vol% content, and it showed the best PEDOT:PSS films properties and good quality heterojunction diodes characteristics with ideality factor of 2.4 and barrier height 0.80 eV.

Properties of In-, Ga-, and Al-doped ZnO films grown by aerosol-assisted MOCVD: Influence of deposition temperature, doping level and annealing

In-, Ga- and Al-doped ZnO films were grown via the aerosol-assisted MOCVD technique using the following air-stable metal-organic precursors: Zn(thd)2, In(thd)3, Al(thd)3 and Ga(acac)3 (thd=2,2,6,6-tetramethyl-3,5-heptanedione, acac=acetylacetonate). Solution of a precursor mixture in 1,2-dimethoxyethane was transformed into an aerosol via ultrasound (2.56MHz), and then the aerosol was transported into the deposition zone by N2+O2 gas. The depositions were performed at 350–600°C. The influences of the substrate, the deposition temperature, the doping element and the doping level on the structural, and the electrical and optical properties of the films were investigated using various characterisation techniques: XRD, SEM, AFM, UV–Vis and FT-IR spectroscopies, and Hall measurements. Epitaxial films on sapphire-R substrates exhibited the best electrical properties. Films doped by Ga and Al had lower resistivity compared to In-doped films. The best Ga- and Al-doped ZnO films (~150–200nm thick) grown on sapphire-R at 400°C exhibited a resistivity of ≈(7–8)×10−4Ωcm, a carrier concentration of ≈1.5×1020cm−3 and a relatively high carrier mobility of ≈50–60cm2V−1s−1. Because the low resistivity of Ga- and Al-doped films was mainly determined by the high carrier mobility, the optical transmittance (T) was high in both the visible (T>90%) and the mid-IR spectral ranges (T≈90% at λ=2.5μm). High transmittance in the mid-IR spectral range makes these films suitable for use as transparent electrodes in applications of the IR optoelectronic devices. Annealing of the films for 30min at 400°C in an Ar+H2 (10%) mixture markedly increased the carrier concentration, which resulted in the increase in the optical band gap (up to ≈3.5eV) and in the decrease in film resistivity and transparency in the mid-IR spectral range. Annealed Al- and Ga-doped films exhibited a resistivity of ≈(4−6)×10−4Ωcm.