Small Temperature Coefficient Of Resistance Research Articles

Fabrication of tantalum silicate films with low TCR and low resistivity by magnetron sputtering

Tantalum silicate (Ta–Si–O) thin film materials have gained significant interest in hybrid renewable energy systems and thin-film resistors due to their exceptional thermal stability and adjustable electrical properties. In this study, we investigated the effects of target compositions and sputtering power densities on the material structures, chemical compositions, microstructures, and electrical properties of Ta–Si–O films. Two target compositions, Ta65(SiO2)35 and Ta80(SiO2)20, were utilized in the deposition process. Notably, we observed substantial variations in the temperature coefficient of resistance (TCR) value and resistivity of Ta–Si–O thin films with different Ta concentrations. Most importantly, when the Ta content of the film is controlled at 62 ± 0.6 % by using this target, the resistivity of the Ta0.62Si0.20O0.18 film can be as small as 2.31 ± 0.05 × 10−4 Ω-cm and has an extremely small TCR of 22 ± 0.4 ppm/°C, which shows an excellent opportunity for the development of precision thin film resistors. A TCR value close to zero can be finely tuned by controlling the Ta concentration in the Ta–Si–O film. These intriguing electrical behaviors were found to be highly correlated with the predominant formation of metallic Ta5Si3 as the main structural phase in the films. This work presents a simple and effective approach to produce Ta–Si–O thin films with near-zero TCR, making them highly suitable for applications under high-temperature conditions. Our findings contribute to the development of tailored thin film materials with desirable electrical properties for advanced electronic and energy devices.

A low TCR MEMS heater developed for cryogenic application

A microheater with a small temperature coefficient of resistance (TCR) at liquid hydrogen temperature was designed and fabricated by microfabrication technology. The NiCr heater annealed in N2 at 250 °C achieved the smallest TCR. The crystal structures of the NiCr film annealed in nitrogen were analyzed using a scanning electron microscope (SEM) and by x-ray diffraction (XRD). The crystallization of the NiCr film improved with the increase in annealing temperature. The failure mechanism of the microheater is studied, and it is seen that the central area of the heating film and the joint of the heating film and the electrode are most vulnerable to destruction.

Study of Ni–Cr / CrN bilayer thin films resistor prepared by magnetron sputtering

In this study, we prepare bilayer Ni–Cr/CrN films. A Ni–Cr resistive thin film was prepared by DC sputtering from targets of Ni0.8-Cr0.2 casting alloy. A CrN protection thin film was prepared based on optimum sputtering conditions of the Ni–Cr film, which was made by DC and RF magnetron co-sputtering from targets of Ni0.8-Cr0.2 casting alloy and chromium. The electrical properties and microstructures of the resistive films at different annealing temperatures were investigated. The phase evolution, microstructural and composition of Ni–Cr and NiCr/CrN films were characterized by X-ray diffraction (XRD), field-emission transmission electron microscopy (HRTEM) and auger electron spectroscopy (AES). The results indicated that the resistivity of the bilayer Ni–Cr/CrN films is higher than Ni–Cr films. When the annealing temperature was set to 300 °C, the bilayer Ni–Cr/CrN films exhibited a resistivity ∼303 μΩ cm with the smallest temperature coefficient of resistance (TCR) of −3 ppm/°C. However, the Ni–Cr films that annealed at 300 °C showed a resistivity of ∼210 μΩ cm, with a TCR of 13 ppm/°C. In addition, the TCR and resistivity variation rate of CrN protective coating layer on the Ni–Cr films after high temperature testing at 150 °C up to 100 h was done. The results show that the average change rate of the TCR for bilayer Ni–Cr/CrN films is lower than single Ni–Cr films.

Investigations on TaHf alloys for thin film resistor applications

TaHf thin films were deposited by performing the cosputtering of Ta and Hf targets. The results indicated that TaHf alloy is suitable for use as a resistive layer for thin film chip resistors and a replacement for NiCr and TaNx alloys. Maintaining the Hf:Ta ratio at approximately 1:1 produced the highest resistivity of 5.7 × 10−4 Ωcm when compared with TaNx and NiCr alloy thin films. This ratio also yielded a smaller temperature coefficient of resistance of −330 ppm/°C compared with TaNx thin films. Furthermore, the temperature coefficient of resistance of most TaHf thin films could be adjusted closer to zero through annealing. The increased Hf content in TaHf alloy was attributed to its poorer thermal stability and anticorrosion property relative to pure Ta films. However, the anticorrosion property of TaHf thin films was still stronger than that of NiCr thin films.

High entropy alloy CrFeNiCoCu sputter deposited films: Structure, electrical properties, and oxidation

High entropy alloy (HEA) films of CrFeCoNiCu were deposited by sputtering. Their structure was characterized and their electric transport properties were studied by temperature-dependent Hall and Seebeck measurements. The HEA films show a solid solution with an fcc structure. The residual electrical resistivity of the films is around 130 μΩ cm, which is higher than the Mott limit for a metal while the temperature dependence of the resistivity above 30 K is metal-like but with a small temperature coefficient of resistivity (2 ppm/K). The dominant scattering mechanism of charge carriers is alloy scattering due to chemical disorder in the HEA. The Hall coefficient is positive while the Seebeck coefficient is negative. This is interpreted as arising from an electronic structure where the Fermi level passes through band states having both holes and electrons as indicated by band structure calculations. Below 30 K, the conduction is discussed in terms of weak localization and Kondo effects. The HEA structure appears stable for annealing in vacuum, while annealing in an oxygen-containing atmosphere causes the surface to oxidize and grow a Cr-rich oxide on the surface. This is then accompanied by demixing of the HEA solid solution and a decrease in the effective resistance of the film.

Influence of a heterolayered Al2O3–ZrO2/Al2O3 ceramic protective overcoat on the high temperature performance of PdCr thin film strain gauges

The application of PdCr thin film strain gauges on gas turbine engines requires protective overcoats to prevent the oxidation of the PdCr sensitive element. In this work, a heterolayered Al2O3–ZrO2/Al2O3 ceramic film, which was fabricated by electron beam evaporation, is utilized as a protective overcoat over the PdCr sensitive thin film. The morphology and microstructure of the prepared films indicate that the composite Al2O3–ZrO2 film is smooth and compact, and the interface between the composite Al2O3–ZrO2 film and Al2O3 film is crack-free, which contributes to improving the protective performance of the heterolayered Al2O3–ZrO2/Al2O3 ceramic protective overcoat at high temperature. Moreover, the PdCr thin film strain gauge with heterolayered Al2O3–ZrO2/Al2O3 ceramic film as protective overcoat displays a minimum drift rate of less than 0.09%/h at 800 °C, and excellent cyclic repeatability such that the eight cyclic curves of the relative grid resistance are almost overlapped from room temperature to 800 °C, indicating the excellent protecting performance of the heterolayered Al2O3–ZrO2/Al2O3 ceramic overcoat. It also reveals the smallest temperature coefficient of resistance of 155.3 ppm/°C compared to the monolayer Al2O3 overcoat and composite Al2O3–ZrO2 overcoat.

A study on the NiCrMnZr thin film resistors prepared using the magnetron sputtering technique

We prepared two types of thin film, a NiCrMn resistive thin film was prepared using direct current and radio frequency magnetron co-sputtering from Ni0.6Cr0.4 casting alloy and manganese targets. A NiCrMnZr resistive thin film was prepared based on the optimum NiCrMn film composition, which was made using direct current and radio frequency magnetron co-sputtering from NiCrMn casting alloy and zirconium targets. The electrical properties and microstructures of the resistive films under different annealing temperatures were investigated. The results indicated that the NiCr film resistivity can be enhanced by adding manganese. When the annealing temperature was set to 300 °C, the NiCrMn films exhibited a resistivity ~400 μΩ-cm with the smallest temperature coefficient of resistance of −6.6 ppm/°C. For NiCrMnZr films, there are some Ni7Zr2 Nano crystalline phases observed when the annealing temperature was set to 400 °C. However, the NiCrMnZr film annealed at 300 °C still has an amorphous structure by transmission electron microscopy analysis. NiCrMn films with 16.7 at.% Zr exhibited the smallest temperature coefficient of resistance (+53 ppm/°C) with the resistivity ∼510 μΩ-cm after annealing at 300 °C in air.

Ni-Cr-Mn-Y-Nb resistive thin film prepared by co-sputtering

A Ni-Cr-Mn-Y-Nb resistive thin film was prepared in this study using DC and RF magnetron co-sputtering from Ni0.45-Cr0.27-Mn0.13-Y0.16 cast alloy and niobium targets. The electrical properties and microstructures of Ni-Cr-Mn-Y films with Nb addition under various annealing temperatures were investigated. The phase evolution, microstructure and composition of Ni-Cr-Mn-Y and Ni-Cr-Mn-Y-Nb films were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), field-emission transmission electron microscopy (HRTEM). All Ni-Cr-Mn-Y-Nb films annealed at 300 °C exhibited an amorphous structure. The Ni17Y12 crystalline phase was observed in Ni-Cr-Mn-Y-Nb films with or without lower Nb content when annealed at 400 °C. When the annealing temperature was set to 300 °C, the Ni-Cr-Mn-Y films exhibited a resistivity ∼480 μΩ-cm with the temperature coefficient of resistance (TCR) at +30 ppm/°C. However, Ni-Cr-Mn-Y films with 14 at.% Nb exhibited the smallest temperature coefficient of resistance (+5 ppm/°C) with the resistivity ∼585 μΩ-cm after annealing at 300 C in air.

Ternary Mn3NMn1−xAgx compound films of nearly constant electrical resistivity and their magnetic transport behaviour

Antiperovskite thin films were successfully prepared by reactive magnetron sputtering. The increasing substitution of Ag atoms at the MnA-sites of cubic Mn3NMn lattice leads to the metal-to-semiconductor transition, through which a vanishingly small temperature coefficient of resistivity down to 20 ppm K−1 over a temperature range of 50 to 200 K was achieved. Meanwhile, with increasing content of Ag atoms the magnetic behaviour of the deposits also changes that the ferromagnetism gradually diminishes and the freezing temperature steadily downshifts. The simultaneously tunable magnetic property and the nature of electric conductivity may inspire some innovative applications of the manganese nitride-based antiperovskite thin films.

Small Temperature Coefficient of Resistivity of Graphene/Graphene Oxide Hybrid Membranes

Materials with low temperature coefficient of resistivity (TCR) are of great importance in some areas, for example, highly accurate electronic measurement instruments and microelectronic integrated circuits. In this work, we demonstrated the ultrathin graphene-graphene oxide (GO) hybrid films prepared by layer-by-layer assembly with very small TCR (30-100 °C) in the air. Electrical response of the hybrid films to temperature variation was investigated along with the progressive reduction of GO sheets. The mechanism of electrical response to temperature variation of the hybrid film was discussed, which revealed that the interaction between graphene and GO and the chemical doping effect were responsible for the tunable control of its electrical response to temperature variation. The unique properties of graphene-GO hybrid film made it a promising candidate in many areas, such as high-end film electronic device and sensor applications.

Junction array carbon nanotube bolometer

Vertically aligned arrays of multi-walled carbon nanotubes (MWNT forests) irradiated with low-intensity near-infrared laser exhibited bolometric response that became significant with decreasing temperature down from room to about 84 K. High responsivity of 42 V/W with signal bandwidth of about 2600 Hz was observed in the region with a surprisingly small temperature coefficient of resistance. This fact along with peculiar current dependences of material differential photoresistance can be explained by lifting Coulomb blockade in carbon nanotube junctions irradiated with light. A combination of significant bolometric response and nonlinear electrical transport are believed to be characteristic features of the nanostructured junction array system. Investigated material also revealed quite substantial noise with equivalent power of 3 * 10−6 WHz−½ that can be reduced by optimization of nanotube junction network in the forest structure.

Annealing effect on the electrical properties and microstructure of embedded Ni–Cr thin film resistor

Ni–Cr (80/20at.%) alloy was deposited on the copper foil substrate as embedded thin film resistor (ETFR) materials by DC magnetron sputtering method. Electrical properties and microstructure of Ni–Cr ETFR under different annealing conditions were investigated. Results indicated that the ETFR exhibited the smallest temperature coefficient of resistance (TCR) after annealing at 250°C for 540s in N2. The structure, stress, composition and surface morphology of ETFR materials were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS) and atomic force microscopy (AFM). The rarely reported hexagonal Ni (011), (002) and (103) in Ni–Cr thin film were found in Ni–Cr (80/20at.%) ETFR materials. The chemical states on the surface of the ETFR materials after annealing were mainly Cr2O3. The segregation of chromium during annealing can affect the resistivity and temperature coefficient of resistance (TCR). The different surface morphology of ETFR in annealing will affect the resistivity.

TCR of the Ni-Cr Thin Film Resistors Used in Piezoresistive Pressure Sensor

In this paper, temperature characteristic of Ni-Cr thin film resistors is studied which have a low temperature drifting coefficient and used in a kind of metal piezoresistive pressure sensors based on MEMS technology. Normally, Ni-Cr alloys have a small temperature coefficient of resistance (TCR) compared with some other metal materials. But it depends on the composition of Ni and Cr in the alloy and on the annealing process under different temperature. Through the research of the effect of the composition of the alloy and annealing cycles, it is found that 50:50wt% Ni-Cr thin film has negative TCR and 80:20wt% NiCr thin film has positive TCR. Both of them have a small TCR and can improve the precision of piezoresistive pressure sensor.

Experimental Fabrication of High Efficiency Force Sensor by Cr-Si-C Composite Thin Film

Chromium silicon carbide (Cr-Si-C) composite thin film has been deposited on the stainless steel substrate by radio frequency (RF) sputtering and the possibility of the force sensor is discussed. The characteristic of the Cr-Si-C composite thin film force sensor is also described. Small temperature coefficient of resistance (TCR) dispersion has been obtained by a Cr-Si-C composite thin film force sensor, and the TCR was between -20 and 10 ppm/°C at the aspect ratio of 510 and the film thickness of 15 nm. The force sensor with hysteresis-free and good linearity has been prepared on the stainless steel substrate by using the Cr-Si-C composite film. The gauge factor of force sensor has increased according to the reduction of film thickness and the increase of sensor pattern aspect ratio. The gauge factor reached 14.2 at the aspect ratio of 510 and the film thickness of 15 nm, which is 7 times larger than that of Ni-Cr strain gauge.

Nickel containing diamond like carbon thin films

Diamond like carbon (DLC) coatings are well established for multiple applications. The electrical conductivity of DLC or amorphous carbon can be influenced by several orders of magnitude via doping with different metals. Depending on the deposition process hydrogen may be incorporated as well, thereby decreasing the conductivity. Recent investigations of DLC disclose nice piezoresistive properties. Our work was focused on Ni:a-C:H thin films on different substrates by reactive sputtering from a nickel target. Several carbon precursors were added to the sputtering gas to create an amorphous carbon hydrogen network with embedded crystal clusters. In order to optimize the piezoresistive properties we varied various process parameters. The piezoresistive response was monitored by measuring the resistance change during bending. Our Ni:a-C:H films develop gauge factors of approx. 12 in a wide range of process parameters. For sensor applications the temperature coefficient of resistance (TCR) is important as well. It depends on the metal concentration in the thin film and can be adjusted by the concentration of the incorporated nickel. It can be set to approximately zero in a wide temperature range of 80–400 K. The combination of a high gauge factor and a very small TCR is achieved and described in this paper. XRD measurements reveal nickel or nickel carbide clusters with diameters of approx. 8–30 nm depending on the metal concentration. The clusters crystallize in the hexagonal hcp structure which could be transformed into the cubic fcc structure of nickel by thermal annealing in a vacuum.

Microstructure and electrical properties of Ni–Cr thin films fabricated by ion beam sputtering

By ion beam sputtering method, Ni–Cr films were fabricated. Then the films were characterised by X-ray diffraction (XRD), atomic force microscopy (AFM), Alpha-Step IQ profilers, four point probe (FPP) respectively. The thin film electrical properties and its microstructure have been probed into. The gauge factor (GF) of the Ni–Cr thin films was determined by cantilever beam method. The results show that the Ni–Cr thin films can be used as piezoresistive films, which present specific characteristics such as relative small temperature coefficient of resistance (TCR), good GF and high sheet resistance.

The crystallization of Cr–Si–Ni–Al amorphous films—nucleation and growth of intermetallic phase Cr(Al,Si) 2

When sputtered amorphous Cr–Si–Ni–Al films with an atomic ratio [Si]/[Cr]>2 were heated up to temperature of 600 °C, they were found to crystallize into two phases: the intermetallic phase Cr(Al,Si) 2 and the pure silicon phase; the growth rate of the crystalline phases at the initial stage of reaction was faster than that at the final stage, resulting from the combined redistribution of Cr, Si, Al and Ni elements between the initial crystalline phases and the parent amorphous phase. The formation of the crystalline phases resulted in a significant increase of both the electrical resistivity and the temperature coefficient of resistance (TCR) for the annealed Cr–Si–Ni–Al films. In particular, the intermetallic Cr(Al,Si) 2 particles, which were embedded in the amorphous matrix, were responsible for achieving a zero TCR. Moreover, the deviation between the TCR 25 125 (TCR averaged between 25 °C and 125 °C) and the TCR −55 25 (TCR averaged between −55 °C and 25 °C) in the annealed Cr–Si–Ni–Al films with small TCR was diminished.

The influence of zirconium on the crystallization behavior and electrical properties of Cr–Si–Al resistive films

Abstract The microstructure and electrical properties of annealed Cr–Si–Al and Cr–Si–Al–Zr films were investigated. When sputtered amorphous Cr–Si–Al and Cr–Si–Al–Zr films were heated up to a temperature of 700 °C, both were found to crystallize into two phases: the nanocrystalline Cr(Al,Si) 2 and Si phase. The addition of Zr into amorphous Cr–Si–Al films inhibited the nucleation and growth of the crystallization phase, resulting in the higher annealing temperatures for Cr–Si–Al–Zr films in comparison with Cr–Si–Al films to obtain a small temperature coefficient of resistance (TCR). As a result, the Cr–Si–Al–Zr films had higher electrical stability.

Comparison of porous silicon, porous polysilicon and porous silicon carbide as materials for humidity sensing applications

This paper investigates the suitability of porous polysilicon and porous SiC as materials for sensing humidity. The investigation is a continuation of earlier work on porous single-crystalline silicon, where it was shown that this material was appropriate for humidity sensing, and could be easily integrated with standard Si processing. It was also shown that membrane structures enable the integration of a heating device to ‘reset’ the system. The best microstructure for humidity sensing was obtained for low-doped p-type silicon. The advantage of using polysilicon is that it is possible to tune its response (by doping) so that it has only a very small temperature coefficient of resistance. The idea is that a humidity sensor with a very small temperature dependence could be realised. The advantage of using SiC is that it offers the possibility of a humidity sensor that could withstand very harsh chemical environments.

Use of low-energy ion assistance for the modification of diamond-like carbon films conductivity

Results for DLC films produced by vacuum condensation of carbon plasma created by a pulsed-arc accelerator are presented. Coatings were irradiated by argon ion beams with an energy of 40–90 eV and an ion current density of 50–200 μA/cm 2. Electron-diffraction results show, that the coatings deposited both with and without ion assistance are amorphous. In comparison with films obtained without ion assistance, the surface resistance of the irradiated films decreased from 10 10–10 11 to 10 5–10 8 Ω/square. It has been found that the film conductivity was thermally activated. The value of the activation energy for non-irradiated and irradiated films was determined to be 0.94 and 0.49 eV, respectively. These films have a negative temperature coefficient of resistance, it is 4–5 less for the irradiated films. X-ray photoelectron spectroscopy has been used to determine the elemental composition and chemical compounds of the irradiated films. A method of manufacturing high resistance low noise miniature resistors is proposed in which a thin modified layer (skin-layer) having a small temperature coefficient of resistance and simultaneously a high surface resistance is formed on the DLC-film surface.