Electrical Resistivity Of Thin Films Research Articles

Nebulizer spray pyrolysis Sm3+ doped TiO2 thin film characteristics and room temperature gas sensing

In this work, pure TiO2 and Samarium doped (1, 3, 5 wt%) TiO2 thin films was successfully deposited on the FTO substrate by Nebulizer spray pyrolysis technique. The result suggested prepared TiO2 film have tetragonal structure and an anatase phase along the (101) direction. According to the UV–Vis-NIR spectroscopic analysis, all the deposited films exhibited a high optical percentage of transmittance, surpassing 80 % in the visible region. The FESEM observation indicated that the TiO2 surface morphology is highly sensitive to the increasing of dopant concentration. The FTIR spectroscopic results confirmed the presence of functional chemical bonding in the deposited films, as evidenced by the reflectance spectra. The ethanol sensing properties of 3 % Sm doped TiO2 films found to exhibit rapid response time at 32 s and a recovery at 20 s for 200 ppm at room temperature for 200 ppm concentration. Moreover, 3 % Sm doped TiO2 thin film electrical resistance, which was measured at 0.6 × 106 O, decreased significantly compared to other materials, indicating enhanced gas sensing properties.

Composition dependent structural, electrical, and optical properties of p-type InSb thin film for homojunction device application

A key component of IR detectors and sources is the indium antimonide, having a narrow direct band gap of 0.17eV. The present paper deals with the fabrication, structural, electrical, and optical properties of p-type indium antimonide thin films of about 300 nm thickness by thermal evaporation technique on ultrasonically cleaned glass substrates with different compositions having formula InxSb1-x. Hall measurement indicates that the asfabricated films were p-type, having a carrier concentration of 0.435 x1018to 1.590 x1018 cm-3 and mobility of 3.29 – 6.62 cm2 /V-s for the film thickness of 300 nm. The activation energy (Ea) was determined and found to be in the range of 0.710 – 0.518 eV from the measurement of electrical resistivity of thin films in the temperature ranges of 313 K - 363 K. X-ray diffraction studies revealed the diffraction peaks (111), (220), and (311) confirm the bulk and thin film formation of InSb polycrystalline materials. The grain size (D), dislocation density(δ), and Strain (ε) have been calculated using XRD data. The lattice parameter (a=b=c) was found to be 6.7074Å from the X-ray diffraction method (XRD). The surface morphology study of thin film through scanning electron microscope reveals the formation of nano-grains with grain size ranging between 7.63 nm to 26.32 nm and surface area of 672-1343 nm2 .

A layer-by-layer green inkjet printing methodology for developing indium tin oxide (ITO)-based transparent and conductive nanofilms

A facile, cost-effective, and green inkjet printing methodology is proposed for the fabrication of a transparent and conductive nanostructured indium tin oxide (ITO) thin films. Unlike solution deposition methods, the ITO nanoparticles did not deposit herein on the substrate. Instead, they are formed in-situ during the inkjet printing. The layer-by-layer inkjet printing is conducted stepwise, by printing the indium acetate based ink on a glass substrate, then printing the tin acetate-based inkjet ink onto a dry previously printed layer. Next, heat treatment is carried out leading to the formation of nanostructured ITO thin film. The resulting inkjet-printed sustainable transparent three-layer thin films were characteristic of evenly dispersed ITO nanodomains taking the advantage of appropriate wettability and rheological properties of the engineered ink solution. Surprisingly, the electrical resistivity of thin film drastically dropped (874 times) from 43.72 Ω cm for one-layer (48 nm thickness) to 0.05 Ω cm for three-layer (154 nm thickness) thin films, without sensible drop in optical properties (from 88% to 84% in the same order). In view of sustainability, i.e. low-cost clean inkjet printing, green chemicals used, and water-based synthesis, this novel technique opens new avenues for developing sustainable transparent thin films with superior electrical conductivity.

Understanding the change in electrical resistance of TiO2 thin film irradiated with YVO4 third‐harmonic generation pulse laser

AbstractTo selectively control the electrical resistance, thin films of TiO2 were irradiated with a YVO4 third‐harmonic generation pulse laser in various power conditions. It was observed that when the laser power was less than 0.26 W, the electrical resistance of thin films decreased with the increase in laser power, whereas when the laser power was more than 0.26 W, the electrical resistance increased as the laser power increases. The minimum electrical resistance of the irradiated thin film was found to be four orders of magnitude lower than that of the unirradiated thin film. X‐ray absorption fine structure analysis revealed that the valence of Ti ions in the thin films was reduced after laser irradiation, indicating the formation of oxygen vacancies with electron doping. The cross‐sectional observation by a scanning electron microscope revealed that high laser power irradiation caused the thin films to become porous, and the percolation theory explains the origin of the increase in electrical resistance with developing porous structure. We propose a phase diagram to completely explain the relationship between electrical resistance and laser power, which supply a guideline on laser modification in TiO2 electrical resistance.

(Invited) One-Dimensional Features of Electron Transport in Single-Walled Carbon Nanotube Thin Films

Single-walled carbon nanotubes (SWCNTs) are excellent conductors with high flexibility, high thermal conductivity, and high transparency. Flexible and transparent SWCNT thin films and SWCNT yarns with high mechanical strength have been produced, and in particular, the improvement of electrical conduction characteristics of these SWCNT aggregates has been studied intensively. The electrical conductivity of SWCNT aggregates have improved year by year, but it is worse than those of a single SWCNT, so far. SWCNT aggregates contain complex structures such as SWCNTs with different chirality structures, many junctions, and bundle structures, which could be the cause of deterioration of transport characteristics, however, it has not been clarified.In this study, we focused on low-density SWCNT thin films and investigated their electron transport characteristics. The low-density SWCNT thin film has a simple network structure since the network consists of the bundles of a small number of long SWCNTs. Here, the magnetic field dependence, temperature dependence, and gate voltage dependence of the electrical conductivity were measured and analyzed.The SWCNT thin films were synthesized by a floating catalyst CVD method, and they were transparent (90%T), and electrically conductive [1]. The thin film consisted of a network structure of bundles, which consisted of about 10 SWCNTs. The films were mixtures with metallic and semiconducting SWCNTs. The electrical resistivity of the SWCNT thin film was measured by the four-point probes method, and the gate voltage (Vg) was applied using an ionic liquid. The direction of the magnetic field was perpendicular to the thin film surface. The areal density of SWCNT length was estimated from the light absorption cross-section of the SWCNT thin films, and then the electrical resistivity was calculated from the actual volume of SWCNTs excluding the void space.SWCNTs generally show p-type characteristics in the atmosphere in the back-gate configuration due to the dope effects of oxygen and/or water molecules. However, the Vg dependence of the electrical resistivity of the thin film showed a bipolar behavior under the ionic liquid gate. The change ratio of the resistivity in the Vg range (-3 to +3 V) was more than 10, which suggested that not only did the non-conductive semiconducting SWCNT become conductive, but the number of percolation paths increased accordingly. Raman scattering spectroscopy also exhibited that semi-conducting SWCNTs were heavily doped by the ionic liquid gating. The electrical resistivity decreased down to approximately 20 μΩcm at room temperature with Vg=-3 V. The temperature dependence in the temperature range (30-110 K) with Vg=-3 V was explained by the variable range hopping (VRH) model with the dimensionality of one, although the SWCNT thin films are two-dimensional structures. Hall resistivity of the thin film slightly changed at different Vg, however, it was almost negligible. It is probably because most of the SWCNT thin films were linear bundle parts, and the bundle diameter was a few nm, which is much smaller than the cyclotron radius [2]. Additionally, the thermoelectric measurement was performed. The Vg dependence of thermoelectrical conductivity showed one-dimensional characteristics [3]. These measurements showed one-dimensional features of electron transport properties of SWCNT thin films. A single SWCNT can be regarded as a one-dimensional system, but in general, one-dimensional features do not appear in the electron transport of SWCNTs in the form of thin films or yarns. In this study, probably because the thin film has a very low density (light transmittance 90% T) and forms a network consisting of a thin bundle structure, the one-dimensional features clearly appeared. The one-dimensionality is one of the origins of the excellent properties of SWCNTs and it is could be a useful index for improving electrical conductivity.AcknowledgmentsI would like to thank H. Date (Univ. of Tokyo) for the experiments and measurements, Prof. T. Fujii (Univ. of Tokyo) for the measurements, and Prof. E. I. Kauppinen for the sample supply.[1] A.G. Nasibulin, et al., ACS Nano, 5 (2011) 3214.[2] M. L. Roukes, et al., Phys. Rev. Lett., 59 (1987) 3011.[3] Y. Ichinose, et al., Phys. Rev. Mater., 5 (2021) 025404.

Experimental Study on Top-of-the-Line Corrosion Using Thin-Film Electrical Resistance Sensors: Study the Effects of Organic Acids and Volatile Corrosion Inhibitors

Thin-film electrical resistance (ER) sensors have been developed to monitor top-of-the-line corrosion (TLC). The objective is to address the ER measurement sensitivity and to investigate the TLC mechanism in the presence of acetic acid, monoethylene glycol (MEG), decanethiol, and diethylamine (DEA). The results showed that 1,000 ppm acetic acid increased TLC by 49%. 80 wt% MEG reduced TLC by 41%. 10 ppm decanethiol achieved TLC inhibition efficiency of 97% while 400 ppm DEA exhibited poor TLC inhibition efficiency (<15%). The ER sensors were able to record an average TLC rate of 0.03 mm/y in less than 24 h.

Development and evaluation of thin film electrical resistance sensors for monitoring CO2 top of the line corrosion

CO2 top of the line corrosion of carbon steel was studied using an in-house Electrical Resistance (ER) monitoring system. The system comprised a thin film ER sensor made of 50 μm thick carbon steel foil, and a high precision constant current circuit. Compensation for the variation in metal resistivity with temperature was achieved by the standard method of using two different circuit paths (corroding and reference). The offset-compensated ohms method using a switched relay circuit was found to effectively overcome thermoelectric junction potentials between the copper connecting wires and the steel sensor element, thus achieving reliable and reproducible top of the line corrosion rates at short time scales. The possible current short circuits by droplet or continuous thin film pathways through the condensate layer were modelled using finite element techniques and confirmed to be insignificant even for a fluid with an electrical conductivity equivalent to that of seawater, more than two orders of magnitude above that of the condensed fluid. The monitoring results successfully demonstrated the role of increasing gas temperature in accelerating top of the line corrosion. The accuracy and the reproducibility of the ER technique for the measurement of corrosion in low conductivity fluids are shown to be at least as good as other published results, and the ability to give a cumulative measurement of corrosion rather than an instantaneous rate is shown to allow the true long term total corrosion depth to be measured, unaffected by short term variations due to cyclic droplet formation.

Effect of chromium percentage doping on the optical, structural, morphological and electrical properties of ZnS:Cr thin films

Zinc sulfide (ZnS) and chromium-doped zinc sulfide (ZnS:Cr) thin films were grown on glass and Si substrates by cathodic radio-frequency (RF) sputtering. The deposition time and RF power were fixed respectively at 90 min and 200 W while chromium content was varied between 3 and 7%. The effect of Cr percentage on the structural, morphological and optical properties of the deposited thin films have been studied. X-ray diffraction analysis indicated that all the sputtered ZnS films were monophasic with a preferred growth orientation along the (111) plane of the zinc-blend (ZB) phase. The Cr-doped films, on the other hand, showed the (111), (2 2 2), and (311) peaks of the same phase that was confirmed by TEM . The crystallite size was about 17.75 nm for undoped ZnS films for RF power of 200 W and increased from 16.3 nm to 25.5 nm for ZnS:Cr. The strain was shown to decrease from 2.2 × 10 −3 to1.45 × 10 −3 . The optical properties (mainly the thicknesses, refractive index , absorption coefficient and optical band gap) were determined from optical transmission measurements in the ultraviolet–visible-near-Infrared wavelength range. Scanning electron microscopy observations revealed smooth film surfaces. Energy Dispersive Spectroscopy (EDS) revealed that the chromium sputtering rate is smaller than the Zn and S ones. UV–Visible transmission measurements revealed an average transmittance on the order 70% for the ZnS films while that of the ZnS:Cr was less than 60% in the visible wavelength region. Moreover, it was observed that the optical band-gap of the ZnS films is 3.72 eV, and slightly decreases from 3.68 to 3.44 eV as the chromium percentage increases, while the films thickness increased. The electrical resistivity of thin films has decreased from 5.2 × 10 5 Ω cm to 1.1 × 10 5 Ω cm as the chromium percentage increases from 3 to 7%. • XRD patterns showed that the particles crystallized in cubic lattice. • The crystallite size was observed to increase with increasing the chromium percentage. • It is observed that the energy band gap decreases from 3.7eV to 3.44 eV. • The resistivity decrease as Cr contents increasing.

Theoretical model for fast calculations of the electrical resistivity of thin metallic films with rough surfaces

A model of electron gas scattering at surface inhomogeneities was developed and applied to describe a surface roughness influence on the electrical resistivity of thin metallic films. The model is developed to be simple enough for fast calculations without detailed investigation of surface topology. The film’s shape is assumed to be described by the average thickness, the surface rms, and the correlation length. The scattering mechanism corresponds to electrical potential changes caused by inhomogeneities. It was found that the electrical resistivity of thin films increases with the increase of the roughness of surface for films of any thickness, whereas the law of this effect depends on film’s thickness. Basing on the developed model, formulas for the electrical resistivity as a function of the roughness rms and the correlation length in cases of thick enough, thin, and extremely thin films have been obtained and discussed with comparison to other models already in literature and experimental data.

Peculiarities of the electronic transport in topological materials of Bi2Se3 and MoxW1-xTe2 (x = 0; 0.5; 1)

The electrical resistivity of thin films of a topological insulator of Bi2Se3 with a thickness of 10 nm to 75 nm, single crystal of Bi2Se3 with thickness of 0.65 mm and single crystals of topological Weyl semimetals MoxW1-xTe2 (x = 0; 0.5; 1) in the temperature range from 4.2 to 300 K was measured. A size effect in the electrical conductivity of Bi2Se3 films was observed, i.e. linear dependence of the conductivity of the film on its reciprocal thickness. It is suggested the existence of two different conduction channels in the Mo0.5W0.5Te2 compound.

Thickness dependence of conductivity in Bi2Se3 topological insulator

The electrical resistivity of thin films of a topological insulator of Bi2Se3 with a thickness of 10 nm to 75 nm, single crystal of Bi2Se3 with thickness of 0.65 mm in the temperature range from 4.2 to 300 K was measured. A size effect in the electrical conductivity of Bi2Se3 films was observed, i.e. linear dependence of the conductivity of the sample on its inverse thickness. It was suggested that similar effects should be observed in other TIs and systems with non-uniform distribution of direct current over the cross section of the sample.

Effect of Preparation and Reduction on Specific Surface Electrical Resistance of Thin Films Obtained from Graphene Oxide Dispersion

The effect of reducing agents and reduction conditions on the electrophysical characteristics of thin transparent conductive films obtained from an alcohol dispersion of graphene oxide (GO) by spin coating at different rotation speeds of the substrate (from 5000 to 7000 rpm) is investigated. Surface morphology of the films, light transmittance, structure of chemical bonds in the films, specific surface electrical resistance, and thickness of the films are determined. Films of multilayer reduced graphene oxide (RGO) with a thickness of 10 to 60 nm and a specific surface electrical resistance of 7.7 to 26.77 kΩ/cm2 and light transmission of 74 to 88%, which can be widely used in photovoltaics and sensor electronics, are obtained. It is established that the treatment of the samples under study in saturated ammonia vapor most effectively contributes to the reduction of the specific surface electrical resistance of the films.

High temperature electrical properties and oxidation resistance of V-Nb-Mo-Ta-W high entropy alloy thin films

High entropy alloys (HEA) show outstanding thermodynamic, mechanical or thermal properties as compared with pure metals or binary alloys. Among several kinds of HEAs, the refractory element containing HEAs exhibit relatively high thermal stability and better mechanical properties at elevated temperature. In this study, the V19.2Nb19.4Mo20.3Ta19.5W21.6 high entropy alloy thin films were deposited on the AISI 304 stainless steel substrates by a magnetron sputtering process. The oxidation behavior and electrical conductivities of HEA thin films at different temperatures were evaluated. The body-centered cubic (BCC) structure of HEA thin film can be kept up to 500 °C oxidation, and it transferred to V-Nb-Mo-Ta-W based oxides and then turned to iron contained oxide phases when the oxidation temperature increased to 700 °C. The electrical resistivity of thin film increased with oxidation temperature. The electrochemical impedance spectroscope (EIS) analysis showed that the total apparent resistivity values of 304SS substrate coated with V19.2Nb19.4Mo20.3Ta19.5W21.6 high entropy alloy thin film at 600, 700 and 800 °C were 5.80, 6.91, and 7.71 Ω·cm, respectively. The electrical resistance of the HEA coated sample was contributed by the oxide resistance and interface polarization. Through the electrical property analysis at high temperatures, the HEA thin film can provide a protection layer to the 304SS substrate and kept the sample's high temperature apparent resistivity to a relatively lower value.

Size Effect in the Electrical Conductivity of Thin Films of Topological Insulator Bi2Se3

The electrical resistivity of thin films of topological insulator (TI) Bi2Se3 10 to 75 nm thick is measured in the temperature range of 4.2 to 300 K. A size effect is observed in the electrical conductivity of the Bi2Se3 films; i.e., there is a linear dependence of a film’s conductivity on its inverse thickness. It is assumed that a similar effect can be observed in other TIs and in systems with nonuniform distributions of current over the cross section of a sample.

Preparation and Influencing Factors of Molybdenum Targets and Magnetron-Sputter-Deposited Molybdenum Thin Films

Aiming to produce qualified molybdenum (Mo) target for sputter deposition, Mo targets were prepared by utilizing powder metallurgy method in this research. The influences of sintering modes, press working modes and total deformation on microstructure and properties of Mo target were studied. Furthermore, magnetron sputtering test was conducted in vacuum environment by using the prepared Mo targets to deposit Mo thin films of which the surface morphologies, electrical conductivities, and crystalline properties were analyzed. The results show that vacuum presintering followed by hydrogen sintering mode can greatly decrease the impurity contents of Mo slabs. It is favorable to obtain the Mo target with fine and uniform grains on size and distribution by using forging mode or forging cogging mode and more than 70% total deformation. With the increase of sputtering currents of Mo target, the grain size and the thickness of the Mo thin films significantly rise, while FWHM of diffraction peaks of grain orientation (110), surface roughness and electrical resistivity of thin films decrease accordingly.

High temperature sensors fabricated on Al2O3 ceramic and nickel-based superalloy substrates

The main purpose of this study is to develop resistance temperature sensors which can work at high temperature. A 2μm thick Al2O3 thin film was deposited as an electrical insulating film on Pt-coated Al2O3 ceramic substrates and nickel-based superalloy substrates by Dual Ion Beam Sputtering Deposition (DIBSD). The results of atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray photon electron spectroscopy (XPS) analyses reveal that the Al2O3 films were dense, smooth and pinholes free with roughness around 3nm. The vertical electrical resistance of thin films deposited on Pt-coated Al2O3 ceramic substrates was more than 2GΩ at room temperature and 100kΩ even at around 800°C. Both resistance temperature sensors (RTSs) fabricated on Al2O3 ceramic substrate and that on nickel-based superalloy substrates showed a linear relation up to 1000°C. The RTS on the ceramic substrates showed stable after 4 thermal cycles while RTS on the superalloy substrates showed a good repeatability of heating and cooling curves even after experiencing a high temperature environment as high as 1000°C.

Atomic layer deposition synthesized TiOx thin films and their application as microbolometer active materials

This paper demonstrates the possible usage of TiOx thin films synthesized by atomic layer deposition as a microbolometer active material. Thin film electrical resistance is investigated as a function of thermal annealing. It is found that the temperature coefficient of resistance values can be controlled by coating/annealing processes, and the value as high as −9%/K near room temperature is obtained. The noise properties of TiOx films are characterized. It is shown that TiOx films grown by atomic layer deposition technique could have a significant potential to be used as a new active material for microbolometer-based applications.

High temperature setup for measurements of Seebeck coefficient and electrical resistivity of thin films using inductive heating.

We have developed an automated setup for simultaneous measurement of Seebeck coefficient S(T) and electrical resistivity ρ(T) of thin film samples from room temperature to ∼650 °C. S and ρ are extracted from current-voltage (I-V) measurements obtained using a semiconductor parameter analyzer and temperature measurements obtained using commercial thermocouples. The slope and the x-axis intercept of the I-V characteristics represent the sample conductance G and the Seebeck voltage, respectively. The measured G(T) can be scaled to ρ(T) by the geometry factor obtained from the room temperature resistivity measurement of the film. The setup uses resistive or inductive heating to control the temperature and temperature gradient on the sample. Inductive heating is achieved with steel plates that surround the test area and a water cooled copper pipe coil underneath that generates an AC magnetic field. The measurements can be performed using resistive heating only or inductive heating only, or a combination of both depending on the desired heating ranges. Inductive heating provides a more uniform heating of the test area, does not require contacts to the sample holder, can be used up to the Curie temperature of the particular magnetic material, and the temperature gradients can be adjusted by the relative positions of the coil and sample. Example results obtained for low doped single-crystal silicon with inductive heating only and with resistive heating only are presented.

Evaluation of depletion layer width and gas-sensing properties of antimony-doped tin oxide thin film sensors

The antimony-doped tin oxide thin films for gas sensors were prepared via a sol–gel route on alumina substrates. The influence of the antimony addition amount on the electrical resistance of thin films was concluded. The relationship between them was plotted in the coordinates of logarithmic resistance against doping amount. On the basis of the Schottky barrier model, a novel method was used to evaluate the width of depletion layer of semiconductive gas sensors by using the first-order derivative of logarithmic resistance with respect to doping amount. The values of the depletion layer width were calculated for the antimony-doped thin films. The H2S gas was used to examine the sensor properties, which positively correlated to the depletion layer width. The oxygen species of O2− and O− were determined to be the adsorbates on SnO2 grains with the same proportion at the operating temperature of 300°C. The location of the Fermi level was found to be a crucial factor that dominated the calculation results.

Effect of substrate temperature on ZnS films prepared by thermal evaporation technique

The nanocrystalline ZnS semiconducting thin films of 500 nm thickness have been deposited on glass substrate at different substrate temperatures (T s) by thermal evaporation technique. The structural property of deposited thin films has been measured by X-ray diffraction, scanning electron microscopy, and Energy dispersive analysis of X-ray. The electrical and optical properties of thin films have been determined by D.C. two point probe and ultra-violet visible spectroscopy measurements. The X-ray diffraction patterns show that thin films have cubic structure. The electrical resistivity of thin films has decreased from 0.36 × 106 to 0.15 × 106 Ω cm as substrate temperature increases from 300 to 400 K. It shows that films have semiconducting in nature. The grain size and electrical conductivity of the thin films have increased as the deposition temperature increased while dislocation density, activation energy, and band gap decreased. The minimum band gap 3.43 eV has been found.