Temperature Coefficient Of The Resistance Research Articles

Aerosol jet printed resistive temperature sensors with high sensitivity

Aerosol jet printing provides a facile, cost-efficient, and environmentally friendly approach to pattern thin films with nanomaterial inks. Printed flexible resistive thin-film temperature sensors play an important role in human body temperature monitoring, soft robotics, prosthetics, and real-time temperature monitoring of large area curved surfaces due to their linear response to temperature, low-cost, scalability, and flexibility. However, the temperature coefficient of the resistance of the printed resistive temperature sensors reported in the literature is much less than that of their bulk metals. In this work, we demonstrate aerosol jet printed resistive temperature sensors with silver nanoparticle ink that have a temperature coefficient of resistance close to that of bulk silver. We report a temperature coefficient of resistance of 3.7 × 10−3 ◦C−1 for the aerosol jet printed resistive temperature sensors, the highest value yet reported in literature for resistive temperature detectors composed of thermally sintered silver nanoparticle thin films. The mechanisms for the increased performance are investigated using metrological and thermal techniques with regard to the source ink and traces. Additionally, we show that the overall sensitivity of the printed sensors can be modulated by controlling the thickness of the printed thin films. Finally, we evaluate the response of the printed resistive sensors to bending strain and humidity, including an investigation into the effects of organic passivation. Overall, this work presents printed sensors with performance on par with vacuum deposited resistive temperature detectors, enabling the fabrication technique to make an industrial impact.

The effect of microstructures on the electrical properties of Cr–Si–C thin film resistors

The resistivity and temperature coefficient of the resistance (TCR) of Cr–Si–C films are investigated with various microstructures changed by annealing up to 1000 °C. The resistivity shows an abrupt change when the annealing temperature is between 450 °C and 600 °C, reaching its peak at 540 °C. In contrast, the TCR increases continuously and shifts from negative to positive values at around 510 °C. The crystal phase, microstructure and composition of the Cr–Si–C films are analyzed using X-ray diffraction, scanning transmission electron microscopy, and energy dispersive X-ray spectroscopy, respectively. The abrupt change in resistivity and TCR values above 450 °C annealing are attributed to the growth of Cr silicide crystals inside the amorphous Cr–Si–C film. The relationship between electrical properties and microstructures of Cr–Si–C film is discussed with the electrical current path model based on physical analysis.

Investigation of x‐ray response for flexible nanocomposite membranes of metal oxides and poly(vinyl alcohol)

AbstractIn this work, flexible composite membranes of nanoparticles (CuO, ZnO, or both), poly(vinyl alcohol) (PVA), and glycerol (GL) plasticizer are fabricated of for X‐ray detector applications. The nanoparticles are synthesized by a modified solvothermal technique and introduced to PVA + GL solution to fabricate the membranes. The mean sizes of nanoparticles are and , for CuO and ZnO in order. The composition of nanoparticles and membranes are investigated by energy dispersive x‐ray spectroscopy and x‐ray spectroscopy. Increasing nanoparticle concentration within the membranes causes their glass transition temperature to shift to low temperatures and enhances their thermal resistance. Fourier‐transform infrared spectroscopy demonstrates the formation of hydrogen bonds between nanoparticles and PVA that are generated by the intermolecular and intramolecular hydrogen bonds. Impedance spectroscopy characterization reveals that the membranes hold negative temperature coefficient of the resistance. The activation energy decreases with increasing nanoparticle concentration. The composite membranes exhibit a decent response to x‐ray that is proportional to its energy. The best x‐ray response is for the membranes with both CuO and ZnO nanoparticles, because of their different bandgaps that cause a wide range of excitation energy to be involved. The fabricated membranes have numerous advantages such as their semiconductor features, flexibility, and feasibility of fabrication on a large scale with reasonable cost.

Study of the Electrical and Dielectric behaviour of selenium doped CCTO ceramics prepared by a facile sol-gel route

A facile sol-gel technique was successfully employed to prepare CaCu3-xSexTi4O12 (x = 0, 0.1, 0.2, 0.3 mM) nanoparticles and after subsequent calcination and sintering at 950 °C and 1050 °C respectively, ceramics of these nanoparticles were obtained. The powder XRD profile reveals that samples have the perovskite phase of CaCu3Ti4O12. SEM micrograph shows the dense microstructure of the ceramics and EDX analysis illustrates the elemental composition of the products. The dielectric behaviour of these ceramics was studied as a function of frequency (1 Hz-1 MHz) with different selenium concentrations at ambient temperature. The results indicate that doping of selenium over the copper (Cu) site enhances the dissipation factor and depresses the dielectric constant (εr) of CaCu3Ti4O12 ceramics. The AC conductivity of the substance was found to decrease with an increase in selenium concentration. The magnitude of high resistivity at high concentrations was mainly caused by the rapid increase in mobility of the charge carriers in the ceramics and follows the positive temperature coefficient of the resistance (PTCR) type behaviour. Electric modulus spectrum of undoped and selenium doped CaCu3Ti4O12 samples indicate that the existence of the non-Debye type of relaxation behaviour. The results suggest that the change in dielectric properties of selenium doped CaCu3Ti4O12 samples may be associated with the lack of oxygen vacancies in the ceramic specimens.

Effect of the Substrate Surface Roughness on the Stability of the Parameters of Thin-Film Resistive Elements

In this paper, the effect of the substrate surface roughness on the stability of the parameters of thin-film resistive elements is investigated. The surface roughness of the substrates is determined by optical microscopy and atomic-force microscopy (AFM). A technology is developed to produce a smoothing surface coating based on thin Ta2O5 films with an amorphous coherent structure, the application of which reduces the microroughness of the Rz surface profile to 12 nm or less. The coating allows thin nanoscale films to be formed on its surface, while the temperature coefficient of the resistance decreases about twice and the stability of thin-film resistors is increased.

Fabrication and characterization of poly(vinyl alcohol)—Glycerol—Spinel ferrites flexible membranes

ABSTRACTPolymer membranes of ferrites nanoparticles, glycerol, and poly(vinyl alcohol) (PVA) were fabricated using a solution casting method. Spinel ferrites nanoparticles, CuFe2O4 or ZnFe2O4, and glycerol were used as dopants to control the membranes' electrical conductivity. The morphology, composition, and interaction between PVA and the dopants were investigated byscanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), differentialscanning calorimeter (DSC), and thermal gravimetric analysis (TGA). Electrical characterization of the membranes was conducted by impedance spectroscopy using frequencies between 1 and 106 Hz and variable temperatures. The results revealed a negative temperature coefficient of the resistance of the membranes. Additionally, membranes with ZnFe2O4 nanoparticles exhibit higher electrical impedance than those with CuFe2O4 nanoparticles. Therefore, electrical conductivity could be controlled using a suitable dopant's composition and concentration. The membranes presented in this study exhibit semiconducting properties, thus, they have potentials to be utilized in multiple applications including the flexible organic‐based device. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48821.

The effect of the nickel and chromium concentration ratio on the temperature coefficient of the resistance of a Ni–Cr thin film-based temperature sensor

Wearable devices have become one of the most promising modern technologies due to the rapid development of network and sensor systems. Moreover, flexible sensors were researched to be applied in wearable devices. In this paper, we show a low cost and flexible temperature sensor that has high responsivity to temperature. A cylindrical PET monofilament was used as a main substrate and a Ni–Cr thin film was deposited by RF magnetron co-sputtering without a pattern. Various Ni–Cr concentration ratios were applied in this paper by altering the sputtering power of the Cr target. Increasing the concentration of Cr resulted in the variation of several characteristics such as the thickness of the Ni–Cr thin film, crystallinity, and the surface state. In addition, depositing the Ni–Cr thin film on a PET monofilament meant that the device showed resistive behavior when the temperature increased. This was proven by measuring the Temperature Coefficient of Resistance (TCR). The TCR was also measured after both repetitive bending and washing to evaluate its suitability in wearable devices. Overall, TCR showed diverse features for different Ni–Cr concentration ratios with a maximum value of 30×10−3°C−1.

Modeling, Fabrication, and Characterization of Large Carbon Nanotube Interconnects With Negative Temperature Coefficient of the Resistance

One of the most appealing properties of carbon nanotube (CNT) interconnects is the possibility of exhibiting, under certain circumstances, a negative temperature coefficient of the electrical resistance, i.e., a resistance that decreases as temperature increases. In the past, this behavior has been theoretically predicted and experimentally observed, but only for a certain class of CNTs, with short lengths (up to some micrometers) and in a limited range of temperature. This paper demonstrates the possibility of obtaining such a desirable behavior in a larger scale (up to fractions of millimeters). An accurate electrothermal model is used to define the conditions under which a negative derivative of the resistance may be observed. Then, a novel bottom–up technique is proposed to realize the interconnect, by self-assembly of short CNTs. The experimental results of an electrothermal characterization demonstrate the possibility of obtaining a negative temperature coefficient of the resistance and confirm the validity of the theoretical model.

Effect of Different Solvents on Cu Micropatterns Formed via Femtosecond Laser Reduction Patterning

We investigated the effect of different solvents on the Cu micropatterns formed via femtosecond laser reduction patterning. Solvents such as ethylene glycol, 2-propanol, and glycerol were mixed with CuO nanoparticles and polyvinylpyrrolidone. The degree of reduction and the resistivity of the fabricated micropatterns depended on the solvent. Glycerol was the most effective reducing agent. This solution was used to fabricate Cu/Cu2O composite micro-temperature sensors. Cu-rich electrodes and Cu2O-rich sensors were selectively formed by controlling the laser scanning speed at 5 mm/s and 0.5 mm/s, respectively, when the pulse energy was 0.53 nJ. The temperature sensor exhibited a negative temperature coefficient of the resistance, which was consistent with the value for Cu2O.

Modificación de las propiedades estructurales, eléctricas y magnéticas del BiFeO3 por la incorporación de Ba y Nb

MODIFICATION OF STRUCTURAL, ELECTRICAL AND MAGNETIC PROPERTIES OF BiFeO3 BY INCORPORATING Ba AND Nb. Bismuth ferrite (BFO) and Ba-Nb-substituted BFO with compositions Bi1-xBaxFeO3 (x= 0, 0.10, 0.15 y 0.20), BiFe1-yNbyO3 (y= 0, 0.03, 0.06 y 0.09) y Bi1-xBaxFe1-yNbyO3 (x= 0.10 (y= 0, 0.03, 0.06 y 0.09) powders were synthesized using the citrate-gel method. Infrared spectroscopy indicated shifting of Bi/Ba-O and Fe/Nb-O bond vibrations and a structural transition was observed by X-ray diffraction. A Williamson-Hall (W-H) analysis revealed that Ba/Nb dopant reduces the particle size and increases the strain crystalline lattice. Impedance analysis suggests that electrical relaxation process is temperature dependent, for all compositions obtained. Furthermore, electrical conductivity increases with temperature showing a typical negative temperature coefficient of the resistance (NTCR) analogous to a semiconductor. Magnetization v magnetic field curves reveal weak ferromagnetic behaviour within the BiFeO3 doped with Ba and Nb, and co-doped with Ba-Nb, measured at room temperature.

The Film Thickness Effect on Electrical Conduction Mechanisms and Characteristics of the Ni–Cr Thin Film Resistor

The electrical conduction mechanisms of Ni–Cr thin film resistor are demonstrated by different film thickness through scattering models fitting. The resistivity and temperature coefficient of the resistance of Ni–Cr thin film are measured to investigate the influence of thickness with different annealing temperature. Finally, an oxidation and atom inter-diffusion model was proposed to explain the effects of film thickness on the electrical properties of Ni–Cr thin film resistor under different annealing temperature.

Electrical transport properties of single-crystal Al nanowires

Single-crystal Al nanowires (NWs) were fabricated by thermally induced substitution of vapor-liquid-solid grown Ge NWs by Al. The resistivity of the crystalline Al (c-Al) NWs was determined to be ρ = (131 ± 27) × 10−9 Ω m, i.e. approximately five times higher than for bulk Al, but they withstand remarkably high current densities of up to 1.78 × 1012 A m−2 before they ultimately melt due to Joule heating. The maximum current density before failure correlates with the NW diameter, with thinner NWs tolerating significantly higher current densities due to efficient heat dissipation and the reduced lattice heating in structures smaller than the electron–phonon scattering length. The outstanding current-carrying capacity of the c-Al NWs clearly exceeds those of common conductors and surpasses requirements for metallization of future high-performance devices. The linear temperature coefficient of the resistance of c-Al NWs appeared to be lower than for bulk Al and a transition to a superconducting state in c-Al NWs was observed at a temperature of 1.46 K.

Polysilicon Thin Film Developed on Flexible Polyimide for Biomedical Applications

Flexible pressure and thermal sensors are the critical parts of the functional electronic skin of prostheses and robots, as well as flexible catheter/devices for multimodal biomedical monitoring. In this paper, a polysilicon thin film was developed on a flexible polyimide substrate using aluminum induced crystallization process for biomedical pressure and temperature sensing applications. The formation of polycrystalline structure was verified from the developed polysilicon film. Long term stability and real-time temperature tests were performed to evaluate potential application to the in vivo monitoring of brain or body temperature. The linear real-time change of polysilicon resistance with temperature was attained with the temperature coefficient of the resistance of −0.0027/°C and the resolution of 0.05 °C. With a gauge factor of 10.3, the polysilicon film developed in this paper represents a promising material for the development of high-sensitivity pressure sensors on flexible polyimide substrates. [2015-0106]

Vanadium oxide thermal microsensor integrated in a microfluidic chip for detecting cholesterol and glucose concentrations

A highly sensitive thermal measurement device based on a vanadium oxide (VOx) microthermistor is developed for detecting biological molecules based on enzymatic reactions. The measurement principle of the VOx thermistor relies on the temperature dependence of its electrical resistance owing to the heat generation of enzymatic reactions. The device comprises a microfluidic channel and chambers, and VOx thermistors on a suspended Si3N4 membrane for thermal insulation. The enzyme is immobilized in silica gel on the sensor. The temperature coefficient of the resistance of the fabricated VOx thermistor is −1.3 %/K. The fabricated device has a temperature resolution of 0.30 mK/√Hz and a temperature response of 4.9 mV/K. Thermal measurements of cholesterol and glucose are demonstrated using the heat production caused by enzymatic reactions. The detectable concentrations of glucose and cholesterol were 30 and 15 µM/√Hz, respectively.

Direct fabrication of Cu/Cu2O composite micro-temperature sensor using femtosecond laser reduction patterning

Micro-temperature sensors, which composed of a Cu2O-rich sensing part and two Cu-rich electrodes, were directly fabricated by femtosecond laser reduction patterning of CuO nanoparticles. Patterning of the microstructures was performed by laser scanning with pitches of 5, 10, and 15 µm. Cu2O-rich micropatterns were formed at the laser scan speed of 1 mm/s, the pitch of 5 µm, and the pulse energy of 0.54 nJ. Cu-rich micropatterns that had high generation selectivity of Cu against Cu2O were fabricated at the laser scan speed of 15 mm/s, the pitch of 5 µm, and the pulse energy of 0.45 nJ. Electrical resistivities of the Cu2O- and Cu-rich micropatterns were approximately 10 Ω m and 9 µΩ m, respectively. The temperature coefficient of the resistance of the micro-temperature sensor fabricated under these laser irradiation conditions was −5.5 × 10−3/°C. This resistance property with a negative value was consistent with that of semiconductor Cu2O.

The Electrical Property of Polymer Matrix Composites Added Carbon Powder

The electrical property of polymer matrix composites with added carbon powder is studied based on the temperature dependency of the conduction mechanism. The temperature coefficient of the resistance of the polymer matrix composites below the percolation threshold (x) changed from negative to positive at 0.20

Structural, Dielectric, Magnetic And Magnetoelectric Characterization Of Co0.5Ni0.5Fe2O4 - Bi0.9La0.1FeO3 Composite

Mixed spinel -perovskite composites of (x) Co0.5Ni0.5Fe2O4-(1−x) Bi0.9La0.1FeO3(x = 0, 0.25, 0.40, 0.55, 1.0) have been synthesized by conventional solid state reaction method and annealed at 850 ºC. The X-ray diffraction (XRD) pattern shows that the composites consisted of spinel Co0.5Ni0.5Fe2O4 and rhombohedral perovskite Bi0.9La0.1FeO3 ceramics. FESEM micrographs show closely packed microstructure with grain size in the range 503 nm - 960 nm. Variation of dielectric constant and dielectric loss with temperature at two fixed frequencies (500 kHz and 1 MHz) was studied. The composite with composition x = 0.55/sintered at 850 ºC exhibits the largest coercitivity (Hc) of 883 Oe. The saturation magnetization (Ms) and magnetic moment (µB) increase with an increase of Co0.5Ni0.5Fe2O4 concentration in the composites. From ferroelectric hysteresis loop analysis the values of remnant polarization (Pr) and coercive field (Ec) was found to lie in the range of 0.018-0.745 µC/cm 2 and 3.89-6.06 kV/cm. The relative change of magnetocapacitance was found to be 6.6% at a magnetic field of 8 kOe for x = 0.55 composition. Impedance analysis suggests the presence of a temperature dependent electrical relaxation in the material having a typical negative temperature coefficient of the resistance (NTCR) behavior analogous to a semiconductor.

Preparation and Electrical Properties of La0.9Sr0.1TiO3+δ.

La1−xSrxTiO3+δ (LST) has been studied in many fields, especially in the field of microelectronics due to its excellent electrical performance. Our previous theoretical simulated work has suggested that LST has good dielectric properties, but there are rare reports about this, especially experimental reports. In this paper, LST was prepared using a solid-state reaction method. The X-rays diffraction (XRD), scanning electron microscope (SEM), broadband dielectric spectroscopy, impedance spectroscopy and photoconductive measurement were used to characterize the sample. The results show that the values of dielectric parameters (the relative dielectric constant εr and dielectric loss tanδ), dependent on temperature, are stable under 350 °C and the value of the relative dielectric constant and dielectric loss are about 52–88 and 6.5 × 10−3, respectively. Its value of conductivity increases with rise in temperature, which suggests its negative temperature coefficient of the resistance. In addition, the band gap of LST is about 3.39 eV, so it belongs to a kind of wide-band-gap semiconductor materials. All these indicate that LST has anti-interference ability and good dielectric properties. It could have potential applications as an electronic material.

High conductance 2D transport around the Hall mobility peak in electrolyte-gated rubrene crystals.

We report the observation of the Hall effect at hole densities up to 6×10¹³ cm⁻² (0.3 holes/molecule) on the surface of electrolyte-gated rubrene crystals. The perplexing peak in the conductance as a function of gate voltage is confirmed to result from a maximum in mobility, which reaches 4 cm² V⁻¹ s⁻¹ at 2.5×10¹³ cm⁻². Measurements to liquid helium temperatures reveal that this peak is markedly asymmetric, with bandlike and hopping-type transport occurring on the low density side, while unconventional, likely electrostatic-disorder-affected transport dominates the high density side. Most significantly, near the mobility peak the temperature coefficient of the resistance remains positive to as low as 120 K, the low temperature resistance becomes weakly temperature dependent, and the conductance reaches within a factor of 2 of e²/h, revealing conduction unprecedentedly close to a two-dimensional metallic state.

LSMO thin films with high metal–insulator transition temperature on buffered SOI substrates for uncooled microbolometers

Abstract La0.67Sr0.33MnO3 (LSMO) thin films have been grown by a pulsed laser deposition (PLD) on Bi4Ti3O12(BTO)/CeO2/YSZ buffered silicon-on-insulator (SOI) substrates. We compare the properties of these films with results of other authors. We analyse structural properties of LSMO/BTO/CeO2/YSZ/SOI multilayer structure prepared using PLD. Electrical measurements have shown that the temperature corresponding to maximum of resistance derivative (operating temperature of a microbolometer) is about 330 K (well above room temperature) and the highest resistivity of metal–insulator transition is at temperature (TP) above 400 K. Temperature coefficient of the resistance (TCR) has achieved values of 3.4% K−1 at 325 K for some LSMO films. Transmission electron microscopy analysis has confirmed epitaxial growth of all the layers and showed a mosaic character of the LSMO films due to strain relaxation.