Temperature Coefficient Of The Resistance Research Articles

Thick film pastes for silicon nitride ceramics

Silicon nitride ceramic is a potential new substrate material for thick film- / hybrid applications in the field of power electronics or microwave technology. The main advantages are the excellent thermal shock resistance, high fracture toughness, a thermal expansion coefficient close to silicon, high thermal conductivity and good dielectric properties. Nevertheless, the use of Si3N4 as chip carries or power electronic package is no achieved due to the lack of suitable connection technology such as thick film pastes. The main challenge for the respective pastes is the adhesion on the substrate. The low thermal expansion of about 2.8 ppm/K of Si3N4 and material interactions with the thick film components need to be considered in the paste development. Therefore, new glasses and glass-ceramic composites are required. Reason developments were performed towards thick film pastes for Si3N4, consisting of AgPd conductor, resistor and encapsulating paste. Good solder wetting (>95%) and high conductivity (<25 mΩ/sq) of the AgPd conductor film is achieved in presence of 2 percent glass with matching composition and 2 percent of an inorganic additive. A high adhesion of up to 23 N/4mm2 (wire pull test) of the fired film was obtained. For resistors, RuO2 was used as conductive material. The influence of the conductive material content on the sheet resistivity and of the TCR modifier was studied. The developed resistor paste has a sheet resistivity of 10 Ω/sq with a temperature coefficient of the resistance (TCR) between -100 and 100 ppm/K. The film structures were analyzed in FESEM studies of cross sections.

Composite Cu/VO and VO/Cu Nanofilaments in Cu/Ta2O5/Pt Devices

Formation of nanofilament conductive path in solid electrolytes is a promising phenomenon exploited in reversible resistive switching. 1 Widely researched metal oxide resistive switching memory is one of the most competitive candidates for future generations of nonvolatile memory applications due to its simple cross-point structure, fastswitchingspeed,highscalabilitypotential,andcompatibilitywith CMOS technology. The mechanism of resistive switching random access memory (RRAM) has been widely attributed to formation and rupture of conductive filaments assumed to consist of metal precipitates such as (Cu, Ag, Ni) or oxygen vacancies. 2 Specifically, switching of a resistive Cu/TaOx/Pt device can be based on the formation of two types of CFs in the same device: Cu and oxygen vacancy (Vo) filaments depending on the polarity of switching voltage. 3 The two types of conduction can be distinguished by different values of the temperature coefficient (α) of resistance defined as R(T) = R(To) [1 + α(T-To)]. For TaOx formed by physical vapor deposition (PVD), the temperature coefficient α of the on-resistance Ron is α(Cu-CF) = 0.0033 K −1 for Cu CF and α(Vo-CF) = 0.001 K −1 for Vo CF. 3 The α(Cu-CF) in oxygen deficient TaOx is close to the bulk value of Cu, α(Cu) =0.0039 K −1 . In this paper, we present evidence for composite Cu and VO single CF observed in Cu/Ta2O5/Pt devices with a Ta2O5 deposited by atomic layer deposition (ALD). The characterization of the temperature dependence of the filament resistance is an effective way of exploring the properties of the elusive nano-filaments. 4‐7 In Ni/HfO2/p + Si devices an α(Ni-CF) = 0.0063 K −14 which is close to the temperature coefficient of solid Ni nanowire (30 nm diameter) of α(Ni-NW). = 0.0048 K −1 . 5 In Ref. 6 the temperature coefficient of the resistance has been measured in the range of 100 K to 300 K on Ag CF in Ag/La-BFO/Pt devices and a difference has been found for bipolar α(Ag-bipolar) = 0.00194 K −1 and for unipolar characteristics α(Ag-unipolar) = 0.00177 K −1 . In Ni/ZrO2/Pt devices it was found that α(Ni-CF) varies between 0.00127 K −1 and 0.00220 K −1 , 7 indicating that the Ni CFs are metallic and close to the α coefficients of Ni nanowire with 10‐30 nm diameter. 5,8,9

Investigation of Cell Structure and Doping for Low-On-Resistance SiC Metal–Oxide–Semiconductor Field-Effect Transistors with Blocking Voltage of 3300 V

We have investigated the effect of n-type doping into the junction field-effect transistor region (JFET doping) on the static characteristics of 3300-V-class 4H-SiC metal–oxide–semiconductor field-effect transistors (MOSFETs). The JFET doping technique is significantly effective in reducing the on-resistance of SiC MOSFETs without degradation of the blocking characteristics when the MOS cells are properly designed. The JFET doping reduces the temperature coefficient of the resistance in the JFET region, leading to lower on-resistance of the SiC MOSFETs at high temperatures.

Thick film pastes for nitride ceramics for high power applications

Aluminum and silicon nitride ceramics show high potent as substrate materials for thick film- / hybrid applications in the field of power electronics and microwave technology. A main advantage of AlN is its very high thermal conductivity. Si3N4 has also a thermal conductivity comparable to AlN but higher thermal shock resistance and fracture toughness. Nevertheless, the use of Si3N4 in power electronic packages or heater applications is not achieved due to the lack of suitable connection technology such as thick film pastes. The main challenge for the respective pastes is the adhesion on the substrate. The low thermal expansion (CTE) of about 2.8 ppm/K of Si3N4 and material interactions with the thick film components must be considered in the paste development. Therefore, new glasses and glass-ceramic composites are required. Reason development was performed towards AgPd based thick film heater pastes for Si3N4. The pastes consists of AgPd in a 1:1 ratio, an inorganic filler and a glass phase adapted to the CTE of Si3N4. By variation of the content of inorganic filler and glass content three pastes with a sheet resistivity of 0.1 ohm/sq, 0.8 ohm/sq, and 7.9 ohm/sq and temperature coefficient of the resistance (TCR) between −100 and 100 ppm/K were developed. The performance of heater films prepared from these pastes under electric pulse load was studied. An electrical power of up to 85 W can be applied without a significant change of the resistivity (ΔR/R) of 0.1%. As reference comparable investigations on AlN were performed with adapted pastes. The film structures were analyzed in FESEM studies.

Sensing properties of resistive-type hydrogen sensors with a Pd–SiO2 thin-film mixture

Zigzag-shaped pure-Pd thin film and Pd–SiO2 thin-film mixture as resistive-type hydrogen sensors were deposited on cover-glass substrates through a multiple-boat thermal evaporator. Temperature dependence of the resistance of the pure-Pd resistive-type sensor showed a relative sensitivity of 3.2% at 80 °C with a temperature coefficient of the resistance (TCR) of 0.058%/°C. Sensing properties of the Pd–SiO2 resistive-type sensor responding to the presence of 1% H2/N2 are much better than those of the pure-Pd one, including a higher relative sensitivity (9%–7.7%), a faster response time (10 s–30 s), and a lower detection concentration limit (50 ppm–100 ppm). A higher dissociation rate and a faster diffusion rate due to porous-like properties and more hydrogen atoms caught due to oxygen associated with the Pd–SiO2 thin-film mixture explain why the Pd–SiO2 resistive-type sensor has a higher relative sensitivity with a shorter response time.

Structural, dielectric, magnetic, magnetodielectric and impedance spectroscopic studies of multiferroic BiFeO3–BaTiO3 ceramics

Abstract Polycrystalline (1−x)BiFeO3–xBaTiO3 (x = 0.00, 0.10, 0.20 and 0.30) ceramics have been prepared via mixed oxide route. The effect of BaTiO3 substitution on the dielectric, ferroelectric and magnetic properties of the BiFeO3 multiferroic perovskite was studied. From XRD analysis it revealed that BaTiO3 substitution does not affect the crystal structure of the (1−x)BiFeO3–xBaTiO3 system up to x = 0.30. Improved dielectric properties were observed in the prepared system. An anomaly in the dielectric constant (ɛ) was observed in the vicinity of the antiferromagnetic transition temperature. Experimental results suggest that in the (1−x)BiFeO3–xBaTiO3 system, the increase of BaTiO3 concentration leads to the effective suppression of the spiral spin structure of BiFeO3, resulting in the appearance of net magnetization. The dependence of dielectric constant and loss tangent on the magnetic field is a evidence of magnetoelectric coupling in (1−x)BiFeO3–xBaTiO3 system. The impedance analysis suggests the presence of a temperature dependent electrical relaxation process in the material, which is almost similar for all the concentrations in the present studies. The electrical conductivity has been observed to increase with rise in temperature showing a typical negative temperature coefficient of the resistance (NTCR) behaviors analogous to a semiconductor and suggests a non-Debye type of electrical relaxation.

Adjustment of thermal hysteresis in epitaxial VO2 films by doping metal ions

Thermal hysteresises of electrical resistance, accompanying with a structural phase transition, in epitaxial VO2 films have been successfully reduced to 1°C or less by doping Ti or Nb ions. We considered that owing to the metal-ion-substitutive structural defects induced by doping metal ions into VO2 films, the structural phase transition easily occurred without superheating or supercooling. In Nb-doped VO2 films, the hysteresis disappeared at a lower doping level than Ti-doped VO2 films. The maximum values of the temperature coefficient of the resistance of V0.91Ti0.09O2 and V0.982Nb0.018O2 films, which exhibited non-hysteretic MI transitions, were −24.8%/°C at 46°C and −21.6%/°C at 19°C, respectively.

Structure and Electrical Resistivity of Sputtered Tb/Ti and Tb/Si Magnetic Multilayers

A study of structural properties and electrical resistivity of [Tb/Ti]n and [Tb/Si]n multilayers deposited by rf-sputtering is presented. The transmission electron microscopy data show that the Tb layers with Ti spacers remain nanocrystalline down to a multilayer thickness of 1.5 nm. In this case titanium does not form a mixture with terbium and there is a tendency of granular structure formation at very low terbium layer thicknesses. In contrast, for the Tb/Si multilayered nanostructures interdiffusion of terbium and silicon layers takes place leading to the formation of amorphous Tb-Si alloys. Resistance was measured in the temperature range 2 to 300 K, showing metallic behavior when the Tb layer thickness, L Tb, was >1.5 nm for [Tb/Ti]n multilayers and for L Tb = 12 nm in the [Tb/Si]n samples. In the other cases, a negative temperature coefficient of the resistance was observed. The behavior of electrical resistivity has been correlated with structural properties of the multilayers. Temperature dependences of the electrical resistance for Tb/Ti and Tb/Si multilayers were studied both without magnetic field and in the presence of magnetic field of 90 kOe.

Magnetoresistance in Sn-Doped In2O3Nanowires

In this work, we present transport measurements of individual Sn-doped In2O3nanowires as a function of temperature and magnetic field. The results showed a localized character of the resistivity at low temperatures as evidenced by the presence of a negative temperature coefficient resistance in temperatures lower than 77 K. The weak localization was pointed as the mechanism responsible by the negative temperature coefficient of the resistance at low temperatures.

Thermoelectric Properties of Bismuth Micro/Nanowire Array Elements Pressured into a Quartz Template Mold

A quartz template having a length of several millimeters and with holes having diameters on the order of micro/nanometers was fabricated. Bismuth was injected into the template holes by high-pressure injection. A bismuth micro/nanowire array sample was prepared, and the temperature dependence of the Seebeck coefficient and the resistance were measured in the temperature range of 50 K to 300 K. Although the temperature dependence of the Seebeck coefficient is similar to that of polycrystalline bulk bismuth, the temperature coefficient of the resistance is much less than that of the bulk sample. The magnetic-field dependence of the Seebeck coefficient was also measured. The Umkehr effect was observed, demonstrating that the mixed micro/nanowires are a bundle of single-crystal wires. The magnitude of the absolute value of the Seebeck coefficient was found to be large in high magnetic field and at low temperature.

Low-noise La0.7Sr0.3MnO3 thermometers for uncooled bolometric applications

We report measurements of the temperature coefficient of the resistance (TCR) and the low-frequency noise of epitaxial La0.7Sr0.3MnO3 (LSMO) thin films deposited on SrTiO3 (STO) and (LaAlO3)0.3(Sr2AlTaO6)0.7 substrates. An x-ray-diffraction study showed that the films were (001) oriented. A normalized Hooge parameter of 9×10−31m3 was measured at 300K in the case of a 10-μm-wide, 575-μm-long line patterned in the 200-nm-thick film grown on STO substrate. This value is among the lowest reported values for manganites and close to values measured in standard metals and semiconductors. The corresponding noise equivalent temperature (NET) was constant in the 300–340K range and equal to 6×10−7KHz−1∕2 at 10Hz and 150μA for a 10-μm-wide, 575-μm-long line patterned in a 200-nm-thick LSMO film. This very low NET value is comparable to the best published results for manganites and was even found to be lower than the NET of other uncooled thermometers such as amorphous semiconductors, vanadium oxides, or semiconducting YBa2Cu3O6+σ. This can easily be explained by the lower noise level of epitaxial manganites thin films compared to others. The results show that despite a TCR of only 0.017K−1 at 300K, and thanks to a very low-noise level, LSMO thin films are real potential material for uncooled thermometry and bolometry.

Uncooled bolometer response of a low noise La2∕3Sr1∕3MnO3 thin film

We report measurements of the optical responses of a La2∕3Sr1∕3MnO3 (LSMO) sample at a wavelength of 533 nm in the 300–400 K range. At 335 K the temperature coefficient of the resistance of a 100-μm-wide, 300-μm-long LSMO line was 0.017K−1 and the normalized Hooge parameter was 9×10−30m3, which is among the lowest reported values. We then measured an optical sensitivity at I=5mA of 10.4VW−1 and corresponding noise equivalent power (NEP) values of 8.1×10−10WHz−1∕2 and 3.3×10−10WHz−1∕2 at 30 Hz and above 1 kHz, respectively. Simple considerations on bias current conditions and thermal conductance G are finally given for further sensitivity improvements using LSMO films.

A.C. Impedance analysis of the effect of dopant concentration on electrical properties of calcium modified BaSnO 3

Polycrystalline electroceramics having the stoichiometric formula, Ba 1− x Ca x SnO 3 ( x = 0–0.15) have been prepared by a standard high temperature solid-state reaction route. X-ray diffraction analysis confirmed the formation of compounds and indicated that the structure of the system still remains cubic with a very small lattice distortion. The electrical properties of Ba 1− x Ca x SnO 3 were studied using the ac impedance spectroscopy technique over a wide range of temperature (30–500 °C) in the frequency range of 100 Hz–1 MHz. Nyquist plots recorded at different temperatures show a decrease in the bulk resistance ( R b) of the materials with rise in temperature for all concentration. The effect of calcium doping on the electrical properties of BaSnO 3 is clearly visible indicated by an increase in the resistance ( R b) with increasing Ca concentration. Ca substitution at the Ba-site results in lowering of the conducting properties irrespective of temperature and the effect is concentration dependent. The impedance analysis suggests the presence of a temperature dependent electrical relaxation process in the material, which is almost similar for all the dopant concentration in the present studies. The electrical conductivity has been observed to increase with rise in temperature showing a typical negative temperature coefficient of the resistance (NTCR) behaviour analogous to a semiconductor. The electrical modulus analysis suggests a non-Debye (polydispersive) type electrical relaxation. Modulus spectra reveal a lowering of material capacitance on Ca-doping in BaSnO 3 in good agreement with complex impedance spectrum results. The effect of Ca concentration on electrical properties as a function of temperature and frequencies are described based on the impedance spectroscopy analysis.

Bias temperature instability assessment of n- and p-channel MOS transistors using a polysilicon resistive heated scribe lane test structure

A fast wafer level device reliability stress at elevated temperatures is demonstrated. It neither needs an external heat source like a thermal chuck or an oven nor cooling. The necessary temperature for acceleration of the bias temperature stress drift mechanism is achieved by electrically resistive heating. For this reason a polycrystalline silicon (polysilicon) resistive heated test structure was designed with a MOSFET embedded between two polysilicon heater strips. A 4-terminal metal resistor above the heater allows temperature control via the temperature coefficient of the resistance. The stress algorithm performs simultaneous thermal and electrical stress. The device temperature is determined by a comparison of the temperature measured at the metal level and the pn-junction temperature determined from the forward diode characteristics. Results of an assessment of the bias temperature instability of CMOS transistors using this type of structure are discussed. They demonstrate the usefulness of the whole methodology presented.

Negative temperature coefficient thermistor based on Bi3Zn2Sb3O14 ceramic: An oxide semiconductor at high temperature

Bi 1.5 ZnSb 1.5 O 7 dielectric ceramic with pyrochlore structure was investigated by impedance spectroscopy from 400 to 750 °C. Pyrochlore was synthesized by the polymeric precursor method, a chemical synthesis route derived from Pechini’s method. The grain or bulk resistance exhibits a sensor temperature characteristic, being a thermistor with a negative temperature coefficient (NTC). Only a single region was identified on the resistance curve investigated. The NTC thermistor characteristic parameter (β) is equal to 7140 °C, in the temperature range investigated. The temperature coefficient of the resistance (α) was derived, being equal to −4.46×10−2 °C−1 at 400 °C. The conduction mechanism and relaxation are discussed.

Thermistor ceramic with negative temperature coefficient based on Zn7Sb2O12: An inverse spinel-type phase

The electric properties of the semiconductor ceramic Zn7Sb2O12 were investigated by impedance spectroscopy. The grain resistance exhibits a thermistor behavior with negative temperature coefficient. Two regions on the resistance curve were identified. Each region shows a different thermistor characteristic parameter (β), which is equal to 3170 and 3845 °C, at measurement temperatures up to 350 °C and above 450 °C, respectively. The temperature coefficient of the resistance (α) was derived being equal to −2.59×10−2 °C−1 and −1.89×10−2 °C−1, at 350 and 450 °C, respectively. The anomalous behavior of the resistance is further evidence of phase transition phenomenon.

Electrophysical properties of Co-, Cr-, Ni-based double-layer films at interdiffusion of atoms

Electrophysical properties of double-layer structures consisting of the alternate Co and Ni layers or Co and Cr or Ni and Cr layers obtained in the vacuum of-lCMo -5 Pa were investigated. The size dependences of the temperature coefficient of the resistance (TCR) of the films were obtained experimentally and compared with microscopic and macroscopic theoretical models. The analysis shows that the main reason for the difference between theoretical and experimental data of TCR is the interdiffusion of atoms from one layer to anolher_and, in some cases, formation of intermediate layer.

Physical Properties of La0.85K0.15MnO3 in Magnetic Field

We have measured the specific heat, resistance and dc susceptibility of the mixed valence manganite La0.85K0.15MnO3 as a function of temperature. The sample shows colossal magnetoresistance effects with phase transitions at low temperature. The magnetic specific heat of this sample is proportional to the temperature coefficient of the resistance, following the Fisher-Langer relation. This suggests that the sharp drop in the transition region of the sample is due to the magnetic scattering.

Semiconducting diamond as material for high temperature thermistors

Based on material parameters of diamond and typical experimental data of inverse temperature dependence of electrical conductivity, the temperature coefficient of the resistance of a semiconducting diamond, has been calculated and combined with classic NTC, and platinum thermistors. The results indicate that a boron-doped diamond is postulated to be used as a thin-film NTC high-temperature thermistor. The use of diamond for thermistors extend the operating speed and temperatures because of inherent material advantages.

Glasses for High-Resistivity Thick-Film Resistors

Knowledge about the role of the glass matrix in thick-film resistors is necessary for improvement of their electrical properties for use in high-performance components. The influence of glass composition on the microstructure of ruthenate conductor and resistor parameters has been studied. Additions of TiO 2 , GeO 2 , and TeO 2 , which in dilute concentrations markedly increase the resistivity, improve the temperature coefficient of the resistance and the voltage stability. The oxide enrichment of the glass film between the conducting particles reduces the ruthenium-ion solubility and decreases the tunneling conductivity between the conductor grains.