Electrical Resistivity Of 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.

Influence of the Gas Preheating Temperature on the Microstructure and Electrical Resistivity of Copper Thin Films Prepared via Vacuum Cold Spraying

Vacuum cold spraying (VCS) has emerged as an environmentally sustainable method for fabricating ceramic and metal films. A high particle impact velocity is a critical factor in the deposition of metal particles during the VCS process, which can be significantly enhanced through gas preheating. This study employs Computational Fluid Dynamics (CFD) simulations to investigate the substantial impact of gas preheating temperature on particle impact velocity and temperature. Elevating the gas temperature leads to higher particle impact velocity, resulting in severe deformation and the formation of dense copper films. The experimental results indicate improvements in both film compactness and electrical properties with gas preheating. Remarkably, the electrical resistivity of the copper film deposited at a gas preheating temperature of 350 °C was measured at 4.4 × 10−8 Ω·m. This study also examines the evolution of cone-shaped pits on the surface of copper films prepared on rough substrates. VCS demonstrates a self-adaptive repair mechanism when depositing metal films onto rough ceramic substrates, making it a promising method for ceramic surface metallization.

Highly conductive copper films prepared by multilayer sintering of nanoparticles synthesized via arc discharge

The major challenges in producing highly electrically conductive copper films are the oxide content and the porosity of the sintered films. This study developed a multilayer sintering method to remove the copper oxides and reduce copper film porosity. We used a self-built arc discharge reactor to produce copper nanoparticles. Copper nanoparticles produced by arc discharge synthesis have many advantages, such as low cost and a high production rate. Conductive inks were prepared from copper nanoparticles to obtain thin copper films on glass substrates. As demonstrated by scanning electron microscopy analyses and electrical resistivity measurements, the copper film porosity and electrical resistivity cannot be significantly reduced by prolonged sintering time or increasing single film thickness. Instead, by applying the multilayer sintering method, where the coating and sintering process was repeated up to four times in this study, the porosity of copper films could be effectively reduced from 33.6% after one-layer sintering to 3.7% after four-layer sintering. Copper films with an electrical resistivity of 3.49 ± 0.35 μΩ·cm (two times of the bulk copper) have been achieved after four-layer sintering, while one-layer sintered copper films were measured to possess resistivity of 11.17 ± 2.17 μΩ·cm.

Electromechanical Behavior of Al/Al2O3Multilayers on Flexible Substrates: Insights from In Situ Film Stress and Resistance Measurements

A series of Al and Al/Al2O3thin‐film multilayer structures on flexible polymer substrates are fabricated with a unique deposition chamber combining magnetron sputtering (Al) and atomic layer deposition (ALD, Al2O3, nominal thickness 2.4–9.4 nm) without breaking vacuum and thoroughly characterized using transmission electron microscopy (TEM). The electromechanical behavior of the multilayers and Al reference films is investigated in tension with in situ X‐ray diffraction (XRD) and four‐point probe resistance measurements. All films exhibit excellent interfacial adhesion, with no delamination in the investigated strain range (12%). For the first time, an adhesion‐promoting naturally forming amorphous interlayer is confirmed for thin films sputter deposited onto polymers under laboratory conditions. The evolution of Al film stresses and electrical resistance reveal changes in the deformation behavior as a function of oxide thickness. Strengthening of Al is observed with increasing oxide thickness. Significant embrittlement can be avoided for oxide layer thicknesses ≤2.4 nm.

Reactive co-sputtering of ternary Au–Ta–O films with tunable electrical resistivity

Heavy-metal-based films with high electrical resistivity are needed for hohlraums for magnetically assisted inertial confinement fusion. Here, we study ternary Au–Ta–O films deposited by reactive direct-current magnetron co-sputtering from elemental Au and Ta targets in an oxygen containing atmosphere. By varying the O content, the electrical resistivity of films can be tuned in a wide range of ∼100–40 000 μΩ cm. With increasing O content, a drastic increase in resistivity occurs at ∼45 at. % of O, separating regimes with two different dominant conduction mechanisms attributed to metallic conduction through the Au–Ta alloy matrix (for ≲45 at. % of O) and tunneling across insulating Ta2O5 layers separating conducting islands (for ≳45 at. % of O). Post-deposition annealing at 300 °C leads to the segregation of Au into ∼50-nm islands, sharply decreasing the resistivity for films with ≳45 at. % of O but not for the metal-like films with lower O content.

Film thickness in miniature ball bearing grease lubricated

In this paper the authors theoretically evaluated the film thickness in a miniature angular contact ball bearing in grease and oil lubricated conditions and correlated with the variation of the electrical resistance experimentally determined by using tribometer CETR UMT-2. For grease the authors determined the film thickness considering base oil viscosity. The rotational speed of the inner race varied between 1 and 500 rpm and the axial load applied on a 7000C angular contact ball bearing was 8.1 N. The IVR and EHD lubrication regimes were analytically evaluated depending on the rotational speed and lubricants for both inner and outer race. Based of the dependence between film thickness and electrical resistance obtained for oil was evaluated the real film thickness obtained by using the grease. In case of oil lubricated condition, the experimental results showed an increase of electrical resistance with the rotational speed caused by increasing of the film thickness according to the theoretical model. For grease lubricated condition, ”a V-shaped pattern” was obtained. High values of electrical resistance at very low rotational speeds were observed. By increasing the rotational speed the electrical resistance for grease decreases until a limit speed and increase continuum over this limit. This behaviour was also reported in literature by ball-disc interferometry that showed at very low speeds that the thickener is dominant and over a speed limit the base oil is dominant in generating the film thickness.

Oblique angle co-deposition of nanocolumnar tungsten thin films with two W sources: Effect of pressure and target current

Two series of tungsten thin films are sputtered on silicon and glass substrates by oblique angle co-deposition technique with an original configuration. Two opposite distinct tungsten targets are simultaneously used, both tilted with an oblique angle of 80°. The growth is performed at low (0.33 Pa) and high (1.5 Pa) argon sputtering pressure and the current intensity applied to the targets varies between 50 and 250 mA. The effect of these deposition parameters on the films microstructure and electrical properties is investigated by scanning and transmission electron microscopy, X-ray diffraction and pole figures, and van der Pauw method. Due to self-shadowing effect, all tungsten sputtered thin films are porous and columnar. At low pressure, the columnar tilt angle β can be tuned with the target current intensity until obtaining vertical columns. X-ray diffraction and pole figure analyses point out a A15 crystal structure (β-W) and a uniaxial fiber texture with a <100> growth direction. In contrast, tungsten thin films deposited at high pressure present a cauliflower structure and are poorly crystallized. Both deposition parameters also affect the films electrical resistivity and anisotropy. These behaviors are discussed and linked to the microstructure and crystallography.

Synthesis, structural, optical, and electrical properties of continuous wave and pulse laser sintered semiconductor Ge films

The crystallization process of Ge films by a continuous wave (CW) and a pulsed laser is very effective for producing smooth, homogeneous, and crack-free polycrystalline films to use in transistors, photodetectors, and photovoltaic applications. However, little progress has been made to directly crystallize Ge films based on micro/nanoparticles (NPs) using the laser sintering (LS) process. In this paper, a simultaneous LS and crystallization process of Ge micro/NPs to develop thick polycrystalline films on silicon substrates is demonstrated. Silicon substrates with a SiO2 insulating layer on top were considered for compatibility with complementary metal–oxide–semiconductor (CMOS) technology. The LS process was applied to solution deposited micro/NPs, 5 µm thick Ge films using both CW mode (infrared laser of wavelength 1070 nm) and pulse mode (UV laser of wavelength 355 nm) laser. After the LS process, around 2–2.5 µm thick film of polycrystalline Ge (pc-Ge) was achieved with optical and electrical properties comparable to traditionally developed chemical vapor deposited films. The crystallinity of the pc-Ge films was evaluated by Raman spectroscopy and x-ray diffraction (XRD). The laser-sintered films exhibited a Raman peak at 300 cm−1 and XRD 2θ peak at 27.35, which indicated the poly-crystalline structure. The fabricated film showed high hole mobility of 203 cm2 V−1 s−1, without any doping and film electrical resistivity value of 6.24 × 105 Ω-cm. The developed LS process allows the quick deposition of polycrystalline thick films, removing surface porosity and voids, increasing films adhesion with the substrate, and faster thermal annealing.

Role of substrate and annealing on microstructural, optoelectronic and luminescence properties of RF magnetron sputtered AZO thin films in confocal configuration

In this investigation, RF magnetron sputtering technique in confocal configuration was used to fabricate AZO thin films with a deposition time of 1 h 30 min on glass, and quartz substrates. The effects of substrate and air-annealing at 400 °C for 60 min on the structural, morphology and surface topography, optical, electrical and luminescence properties are studied by X-ray diffraction, scanning electron microscopy, atomic force microscopy, Ultraviolet–Visible-Near Infrared spectrophotometry, Hall Effect measurements and photoluminescence spectroscopy. X-ray diffraction patterns show that all AZO films are polycristalline and have a hexagonal wurtzite structure with a preferential orientation along the (002) plane. The crystallinity, (002) peak intensity, grain size and surface roughness of the films are found to be dependent on substrate and annealing. According to Ultraviolet–visible measurements, as-deposited and annealed AZO thin films grown on glass substrates demonstrate a better average transparency in the visible region. Moreover, for both substrates, the annealing in air causes an enhancement in the optical transmittance and a reduction in the band gap of AZO films. Hall Effect measurements confirm the n-type conductivity of AZO films and their electrical properties are substrate dependent and highly affected by air-annealing. In fact, as the temperature increases from RT to 400 °C, the electrical resistivity of films on glass and quartz substrates increases strongly by approximately 80 times from 1.25 × 10−3 and 1.05 × 10−3 Ω cm to 9.09 × 10−2 and 8.82 × 10−2 Ω cm, respectively. Room temperature photoluminescence investigations put into evidence that emission spectra are depending on the substrate nature and annealing. In particular an intense violet emission is observed for the AZO film deposited on quartz substrate at room temperature. The annealing at 400 °C leads to the enhancement of the UV emission, the quenching of the violet emission and the improvement of the green and yellow-red bands.

A comparison of pad metallization in miniaturized microfabricated silicon microcantilever-based wafer probes for low contact force low skate on-wafer measurements

Miniaturized, microfabricated microelectromechanical systems-based wafer probes are used here to evaluate different contact pad metallization at low tip forces (<mN) and low skate on the on-wafer pads. The target application is low force RF probes for on-wafer measurements which cause minimal damage to both probes and pads. Low force enables the use of softer, more conductive metallisation. We have studied four different thin film contact pad metals based on their thin film electrical resistivity and micro-hardness: gold, nickel, molybdenum, and chromium. The contact pads sizes were micrometre (1.9 × 1.9 µm2) and sub-micrometre (0.6 × 0.6 µm2). The contact resistance of Au–Au, Ni–Au, Mo–Au, and Cr–Au was measured as a function of tip deflection. The tip force (loading) of the contacts was evaluated from the deflection of the cantilever. It was observed that an overtravel of 300 nm resulting in a contact force of ∼400 µN was sufficient to achieve a contact resistance <1 Ω for a sub-micrometre gold contact pad. Our results are compared with an analytical model of contact resistance in loaded metal-metal contacts—a reasonable fit was found. A larger contact resistance was observed for the other metals—but their hardness may be advantageous when probing other materials. Using a combination of a rigid silicon cantilever (>1000 Nm−1) and small contact pads enabled us to show that it is the length of the pad (in contact with the surface) which determines the contact resistivity rather than the total contact pad area.

Study of vanadium pentoxide thin film prepared by spin coating method

Attraction towards V2O5 thin film is due to its wide range of applications in the field of opto-electric device, electro-chromic device, as an excellent catalyst, gas sensor etc. Here, we report the deposition of V2O5 thin film using spin coating method. To study the effect of annealing, the prepared films were annealed at 250° C, 350° C and 450° C. To study the structural and optical properties of the prepared films, X-Ray Diffraction (XRD) and UV– Visible spectroscopy were used. XRD reveals the increase in the crystallinity of film with increase in temperature. The film annealed at 450° C has pure β- V2O5 tetragonal phase. The decrease in band gap of the films was also observed with increase in annealing temperature. Moreover, the electrical resistance of films was also measured.

Features in low-temperature electrical resistivity of amorphous Cd3As2 films due to hopping conductivity with changing activation energy

Amorphous Cd3As2 films were deposited on single-crystalline SrTiO3 substrate by high-frequency non-reactive magnetron sputtering. Electrical resistivity of the film, measured within 3-75 K range, increases at cooling. Below ∼70 K, negative transverse magnetoresistance observed. Features in electrical resistivity and magnertoresistance can be attributed to variable-range hopping conductivity of the Mott type with local activation energy, which is temperature-dependent. Two temperature ranges in the hopping conductivity observed. Appearing two ranges is in qualitative accordance with the Mott-Davis energy-band model developed for amorphous semiconductors. High temperature range of the hopping conductivity is attributed to electron hops between localized states, positioned inside band tails, whereas electron hops between localized states, positioned inside Fermi-peak, can be responsible for low-temperature range. At taking into account temperature dependences of local activation energy, universal expression for various mechanisms of the hopping conductivity could be successfully applied to analyze the experimental data.

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 Oxygen Flow Rate on the Characteristics of RF Sputtered ZnO Thin Films

Zinc Oxide (ZnO) thin films were deposited on glass substrate by radio frequency (RF)reactive magnetron sputtering technique at variable Oxygen flow rates while Argon flow rates waskept constant. The effect of oxygen flow rate on structural, electrical, optical properties of nanostructured ZnO thin films were investigated by X-ray diffractometer, scanning eletron microscopy(SEM), Hall effect measurements and UV-Visible spectrophotometer. X-ray diffraction (XRD) datareveals films are polycrystalline hexagonal structure with (002) peak as a preferred orientation andcrystallite size was found to be in range12 nm-16 nm.The electrical resistivity of films decreasesfrom 10-1 Ω-cm to 10-2 Ω-cm. All deposited ZnO thin films shows high transmittance above 95% inthe visible range 360 nm-800 nm. The optical band gap and refractive indices have been calculatedusing UV-Vis transmission spectra. Oxygen gas flow rates found to have large impact onoptoelectronic properties of ZnO films.

Piezoresistive behaviors of carbon nanotube film under complex loading states

This paper was devoted to investigating the effects of unloading and coupled shear load on tensile electrical resistance variation of CNT (Carbon Nanotube) film. Two kinds of experiments were designed to create different loading states. The variation of CNT film electrical resistance with deformation under loading–unloading and tension–shear conditions were recorded and analyzed. A 3D CNT network model was constructed to describe the morphologies of CNT films subjected to mechanical load. Combined with tunnel theory, the 3D CNT network model was used to simulate the electrical resistance variation of CNT film after deformation. The feasibility of the model was discussed. The effect of unloading and coupled shear load on electrical resistance variation was compared and analyzed via the experimental and numerical results.

Structural, electrical and gas-sensitive properties of Cr2O3 thin films

Abstract Cr2O3 thin films were synthesized by RF magnetron sputtering of a Cr target in an oxygen-argon plasma. The effect of annealing temperature on the structural, electrical, and gas-sensitive properties of the Cr2O3 thin films was studied. According to AFM, SEM, XRD, EDX, XPS, optical spectroscopy and electrical measurements the annealed films were characterized by a polycrystalline structure, high stoichiometry, p-type conductivity and a band gap energy of 3.3 ± 0.2 eV. An increase in the annealing temperature from 350 to 450 °C leads to formation of Cr2O3 grains with a diameter from 30 to 130 nm and to a significant increase in the film electrical resistance. Cr2O3 demonstrated sensitivity to NO2, H2, NH3, vapors of acetone and toluene in the heating temperature range of 25–200 °C. Changing the annealing temperature allows to control the sensitivity of the films to certain gases. Thus, Cr2O3 thin films subjected to annealing at a temperature of 450 °C were characterized by a high response to NH3, while those annealed at a temperature of 400 °C – to toluene vapors and that annealed at 350 °C – to NO2 and acetone vapors. A qualitative model of the sensory effect was proposed.

Electroless Deposition of Pure Cobalt Film for Realizing Low Resistivity LSI Interconnection

With a scaling trend of LSI interconnection, effective resistivity of Cu/barrier metal interconnect is expected to increase due to increasing electron scattering due to ultrafine dimension smaller than electron mean free path. Therefore, the trend is to substitute Co metal liner for Cu when the line width of LSI interconnect is 10 nm or less. While Chemical Vapor Deposition (CVD) or electrodeposition are discussed as formation method of Co mainly, we introduced electroless deposition (ELD) method. In electroless deposition of Co using Dimethylamine Borane (DMAB), B was incorporated in Co film, and the electric resistivity of the film after heat treatment (400℃ in vacuum, 30 minutes) was 68 µΩ∙cm. In this report, we introduced hydrazine monohydrate as a reducing agent for the purpose of forming ELD pure Co film.ELD Co bath contains cobalt chloride hexahydrate (CoCl2∙6H2O) as metal ion source and hydrazine monohydrate (N2H4∙H2O) as a reducing agent. In addition, some complexing agents were added to prevent Co hydroxide precipitation. Plating bath pH was adjusted to about 12.3 and the CVD-Co film (thickness: 20 nm) on SiO2 and Si was used as substrate for Co deposition. Obtained Co plated film were observed and analyzed by Scanning Electron Microscope (SEM), X-ray Photoelectron Spectroscopy (XPS) and X-Ray Diffraction (XRD). Furthermore, Co plating film was heat-treated at 400℃ in vacuum, and the electrical resistivity of Co film before and after the heat-treatment was measured by four-terminal method.The deposition rate of ELD cobalt bath was about 19 nm/min, and this cobalt film consisted of columnar crystals (Figure 1). If the film surface is rough, it may cause void formation during electroless Co plating in fine via. Regarding the properties of Co film, impurities derived from the reducing agent were not detected from XPS spectral analysis. Co film with few impurities leads to low resistivity because the probability of electron impurity scattering decrease. However, the resistivity of obtained and heat-treated Co film is 53 µΩ∙cm. It is necessary to form the smooth Co film to reduce the electrical resistivity. Figure 1

Physical properties of Al-doped ZnS thin films prepared by ultrasonic spray technique

The objective of this work is study the effect of Al doping on physical properties of ZnS thin films. Undoped and Al-doped ZnS films were deposited by ultrasonic spray method using atomizer on glass substrates at 500°C. The films were synthesized with different Al doping ratio ranged from 0 to 6 %. The films structure and morphology were studied by means of X-ray diffraction (XRD), scanning electron microscopy. The films optical and electrical properties were studied by UV-VIS spectrophotometer and four probes method. The structural analysis indicated that the doped ZnS films have a hexagonal structure with strong preferred orientation (002) direction for all Al concentration. The (SEM) images revealed a dense surface, highly homogeneous and better adherent to the substrate surface. The average crystallites size increases from 32 nm to 43.8 nm with increasing of Al concentrations. UV–vis–NIR spectro-photometric measurements showed that the films were good transparent (60–73%) in the visible region. The films band gap is ranged from 3.7 eV to 3.9 eV. The performed electrical measurements indicate that the films electrical resistivity depends on the doping ratio. The latter was decreases with increasing the Al concentration from 8 × 104 to 3.35 × 104Ω.cm.

Enhancement of Adhesion Force and Surface Conductivity of Graphene Oxide Films Using Different Solvents

In this work, the nanotechnology procedure was utilized to improve both the adhesion force and surface properties of graphene oxide (GO) films. GO has been obtained in a powder form by oxidation purified graphite using the modified Hummer’s technique. Different films of GO nanoparticles (NPs) were deposited using several types of solvents distilled water, acetone, ethanol, dimethyl formamide (DMF) or ethylene glycol. Examination of structural and optical properties of GO films were studied by XRD and UV–vis absorption spectroscopy. Moreover, electrical properties, surface roughness, contact angle, adhesion force, wetting energy and spreading coefficient were investigated. It was observed that the properties of the prepared films are influenced by the solvent type. The electrical resistivity of films is highly dependent on the solvent type which exhibited the lowest value with distilled water. Furthermore, GO film synthesized with distilled water has the best values of adhesion force and average surface roughness (Ra) 143.4 mN/m and ∼ 7.83 μm, respectively. These results are mostly attributed to hydrophilic cites and GO NPs agglomeration in the surface of films and the effects of their size leading to an expansion in the surface roughness.

Physical properties of Pb doped ZnS thin films prepared by ultrasonic spray technique

In the present work, high quality Pb doped ZnS thin films were deposited on glass substrates at 450°C using spray ultrasonic technique. The dependence of the structural, morphological and optical properties of the films on the lead (Pb) doping amount was investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis–NIR spectrophotometry, and four-point method. The improvement of the obtained Pb:ZnS thin films properties were discussed as a function of Pb concentration (0.5 to 2 at.%). The average crystallite size of Pb:ZnS was found in the range of 25–37 nm. The scanning electron microscopy (SEM) reveals that the films are continuous, homogeneous and dense. The UV–vis–NIR spectroscopy characterizations demonstrated that all the films exhibit good transmittance (60–70%) in the visible region and their optical band gap energy (Eg) changes from 3.92 to 3.6 eV. The films electrical resistivity showed an apparent dependence on Pb content.