Resistance-temperature Relationship Research Articles

Carbon nanotubes film based temperature sensors

This study presents the design and fabrication of carbon nanotubes (CNTs) film based temperature sensor. The sensor has been fabricated by the sequential deposition of thin layers of glue and CNT nanopowder on a paper substrate. The diameter of multiwalled nanotubes (MWNTs) varied between 10 and 30 nm. The ostensible thickness of the CNT films in the samples was ∼30–40 μm. The inter-electrodes distance (length) and width of the surface-type samples were 5 and 4 mm, respectively. The results revealed that the DC resistance of the sensors decreases in average by 10–20% as the temperature increases from 20 to 75 °C. The resistance–temperature relationship was simulated.

Evaluating the Resistivity-Temperature Relationship for RTDs and Other Conductors

It has long been established from experimental evidence that resistance temperature detectors (RTDs) and conductors in bulk form have an electrical resistivity that is a linear function of temperature. Although this experimental data has existed for some time, there has not been a straightforward model to explain the mechanisms leading to this relationship. In order to better understand the nature of this relationship, a microscopic model is needed so that analysis of the electrons in the material can be performed. Therefore, a theoretical framework using solid-state physics and quantum mechanics principles is presented and developed to obtain an equation for bulk conductors that relates resistivity to temperature. It is then shown that this newly developed equation produces a linear relationship for conductors and provides a very good match with experimental data obtained from platinum and nickel RTDs. Therefore, this newly developed theoretical model provides great insight into the mechanisms of experimental findings.

Nanopatterned polycrystalline ZnO for room temperature gas sensing

We demonstrate that the soft e-beam lithography (soft-eBL) fabricated polycrystalline ZnO nanolines show reproducible response to ppm-level H 2 and NO 2 even at room temperature, due to the intrinsic Joule heating effect in such nanodevices. The Joule heating effect is confirmed by studying the resistance–temperature relationship of the sensor as well as the persistent photoconductivity phenomena in ZnO. We note that Joule heating increases the nanoline temperature to around 72 °C, which enhances the oxidation–reduction reaction at the ZnO surface. Therefore, the nanolines show faster photoresponse than the thin film. These results may help tailor and optimize gas sensor devices for improved performance.

STUDY ON METAL MEMBRANE TEMPERATURE SENSOR AND MICROHEATER FOR PCR CHIP

The development of PCR chip shortens the reaction time of DNA amplification, reduces the bulk of reaction reagents; therefore, it is widely applied to biomedicine and other related fields. Since PCR reaction is completed through three different precise temperature zones periodically, the sensitivity of temperature measurement and the heating property of the metal membrane must be highly regarded. In this paper, three kinds of membranes, Ni , Pt , and Ni – Cr , were fabricated on silicon substrates; their resistance–temperature characteristics and heating properties are discussed. The results show that Ni and Pt films have good linear resistance–temperature relationship; the heating property of Pt film is superior to that of Ni – Cr film. The PCR chip with Pt film microheater can reach 150°C in a short time with 25 V voltage.

Hopping Conduction in NTD Germanium: Comparison Between Measurement and Theory

We present precise measurements of the resistance-temperature variation of several samples of neutron transmutation doped (NTD) germanium, at temperatures from 70 mK to 1 K. This material is widely used for sensitive thermometry, often as the thermistor element in bolometers and microcalorimeters. It is also used in investigations of the low temperature conductivity of highly doped semiconductors. The resistance, R, is expected to follow the variable range hopping equation R(T)=R 0 exp(T 0/T) p , where T is temperature and R 0 and T 0 are material parameters. A value of p=0.5 is predicted theoretically, and generally seems to be in good agreement with experimental measurements. However, some theories and numerical calculations predict different values of p. Knowledge of the correct resistance-temperature relationship is important for the accurate calibration of thermometers, and also delivers insight into the basic physics involved. Most experimental measurements on germanium have not had sufficient precision to distinguish between the different predicted values of p. We show that such measurements are nevertheless possible. Our results are all in excellent agreement with the expected variable range hopping behaviour. However, the values of p appear to vary with doping density, in disagreement with most theories. We have considered and rejected both random and systematic errors as an explanation for the observed behaviour, and have confirmed the results by making measurements in two different systems with independent readout systems and temperature calibrations. The situation is complicated by the possibility of temperature dependence of R 0. The expected form is R 0(T)∝T q; however, there is considerable disagreement over the predicted value of q. We show that in general it is not possible to determine both p and q from resistance measurements. However, our results can only be explained if either or both of q and p vary from sample to sample. Such behaviour is not generally expected. We show that neglecting the q term can lead to serious errors when calibrating thermometers. However, the degeneracy between p and q means that for a calibration the q term can be neglected, and good fits obtained if p is allowed to vary. Our results suggest that further theoretical work is required in this area, backed up by more comprehensive measurements.

Application of radiometric temperature determination methods to semiconductor gas sensors

A radiometric method for the determination of the operating surface temperature of very small objects to within ±5 K has been applied to commercial semiconductor gas sensors operated in a static atmosphere. The method involves the collection of the infrared (IR) emission spectrum of the sensor at regular intervals over the operating heater voltage range, followed by the fitting of ambient-corrected Planck functions to determine the temperature at each voltage. At least one independent calibrating temperature measurement (to eliminate the effects of sensor emissivity and spectrometer response) is obtained using the known melting point of an inorganic salt. The operating voltage–temperature relationships for two popular Figaro tin oxide sensors were found to be pseudo-linear and are reported as T=103 V+214±3 K for the Figaro TGS813 sensor with its base removed, T=101 V+224±5 K for the TGS813 with its base attached, and T=106 V+238±5 K for the Figaro TGS2611 sensor. (The temperature of the sensors does not rise appreciably above ambient when they are operated below 0.5 V.) These results indicate that sensor temperatures are significantly higher than most previously reported estimates, particularly those made using infrared thermometers (IRTs). A heat loss model for the sensors is discussed, and the calibration of the heater resistance–temperature relationship is achieved for the TGS2611.

Effect of heating rate on positive-temperature-coefficient-of-resistivity behavior of conductive composite thin films

A phenomenon was discovered that leads to the selective detection of abrupt increases in the temperature of conductive composite thin films consisting of conductive ceramic fillers and an insulating polymer matrix. Examining the heating rate dependence of the positive-temperature–coefficient-of-resistivity (PTCR) effect provided information about this intelligent phenomenon. The anomalous PTCR effect was observed above 0.3 °C min−1 for all the prepared films. However, the magnitude of the anomaly decreased when the heating rate decreased below 0.1 °C min−1, and when the heating rate further decreased below 0.04 °C min−1, the anomalous resistivity–temperature relationship disappeared. The results suggest that these thin films can selectively detect abrupt increases in temperature, which could lead to an intelligent mechanism. Our results also suggest a PTCR mechanism, in which the expansion of crosslinked polymers in the thermodynamic nonequilibrium state essentially produces the anomaly.

The characterization of single structure diamond heater and temperature sensor

Abstract Heat generation and temperature sensing, essential for most heater applications, were achieved by using a single diamond resistor. Chemical vapor-deposited p-type diamond resistors were fabricated on polycrystalline diamond substrates and oxidized Si wafers using diamond film technology compatible with integrated circuit processing. The resistivity-temperature relationship of diamond thermistors was characterized in the temperature range of 300–1000 K. The maximum heating temperature and power density of 950 K and 93 W cm −2 , respectively, were achieved for heating application. The average difference between the temperatures determined by self-sensing of diamond thin film heaters and the temperatures measured by thermocouples was in the range of 1.05–3.6%. Due to its high thermal conductivity, the substrate temperature was isothermal, as indicated by two-dimensional optical thermometry.

In situ diffuse reflectance infrared spectroscopy (DRIFTS) study of the reversibility of CdGeON sensors towards oxygen

A novel diffuse reflectance infrared spectroscopy (DRIFTS) chamber, specially designed for in situ and simultaneous infrared and conductance analysis of sensors, is described in this paper. The capabilities of this new tool are shown through the study of the reversible behaviour versus temperature of a CdGeON sensor under N 2 and synthetic-air atmospheres. The conductance of the sensor is directly related to the presence of DRIFTS bands at 810, 780 and 580 cm −1 assigned to oxygenated species directly bonded to single Ge atoms. These species are eliminated or restored in the solid network upon heating under N 2 or synthetic air, respectively. From the analysis of the resistance-temperature Arrhenius-type relationships, the influence of the atmosphere on the conduction mechanism is discussed.

Structural and galvanomagnetic properties of CuInS2 films

Thin copper-indium-disulphide films were prepared by thermal evaporation technique. X-ray diffraction analysis of the compound used for evaporation showed a tetragonal polycrystalline structure. Differential Thermal Analysis (DTA) of this compound showed two exothermic peaks at 585 and 632 °C. Thin films with thicknesses of 0.14 and 0.27 nm have a deposition rate 10 nm/min, while those with thicknesses of 0.54 and 0.56 nm have a deposition rate 48 nm/min. The obtained films have polycrystalline structure as shown from the electron diffraction study. A growth process was detected in the films by transmission electron microscopy as the film thickness increases. The surface topography was revealed by scanning electron microscopy. The variations of Hall mobility and carrier concentration with magnetic induction were studied. The resistivity-temperature relationship was investigated, from which the activation energies before and after annealing were found to be 0.2, 0.3 and 0.055 eV, respectively.

Influence of Oxygen in the Sensing Properties of Cadmium and Germanium Oxynitride

A novel cadmium and germanium oxynitride (CdGeON) sensor, originally designed for NH3 and SH2 detection, has been studied by in situ Fourier transform diffuse reflectance infrared spectroscopy (DRIFTS), XPS, and UV−vis in order to elucidate the influence of an oxygen-containing environment on the sensor's electrical response. Under oxygen, the conductivity of this sensor is directly related with DRIFTS bands at 810, 780, and 580 cm-1 assigned to oxygenated species bonded to single Ge atoms. These species are reversibly eliminated or restored in the solid framework upon heating in N2 or synthetic air, respectively. XPS and UV−vis spectroscopies have confirmed the oxygen uptake and the increase in the coordination number of Ge atoms upon exposure of the CdGeON sensor to synthetic air. A similar conclusion is presumed for Cd atoms although no conclusive results can be inferred from the UV−vis spectra. From the analysis of the resistance-temperature Arrhenius-type relationships, a model involving the filling ...

Observation of intergrowth structures of Hg-1212, Hg-1223 and Hg-1234 phases in a nominal Hg-1223 ceramic superconductor

Intergrowth structures of the Hg-1223 superconductor containing other Hg superconducting phases such as Hg-1212 and Hg-1234 were observed under a transmission electron microscope. The X-ray diffraction pattern, the resistance-temperature relationship and the a.c. magnetic susceptibility-temperature relationships indicate that the sample contains mainly Hg-1223 phase. However, scanning electron microscope and energy dispersive X-ray analysis show that the sample contains intergrowth structures. In our previous joint work, two fundamental intergrowth structures were reported. Here we report two more intergrowth structures, namely Hg-1223/(Hg-1212, Hg-1223, Hg-1234) and Hg-1223/(Hg-1223, Hg-1234). Calculation of the ratio of strain energy density Utand the Young modulus E001 along the (001) direction of the unit cell of the Hg sample shows that the value of Ut/E001 for the first region is 1.54*10-4 and for the second is 1.56*10-3. The reason for the formation of the ill-defined mismatch region in the second intergrowth structure may be due to the relatively large strain field in the conjunction boundary of the structure.

On the thermodynamic accuracy of the ITS-90: platinum resistance thermometry below 273 K

An analysis of the resistance-temperature relationship for six low-temperature platinum resistance thermometers is carried out to determine the thermodynamic accuracy of the ITS-90 below 273 K. The use of smooth thermodynamic functions in a model equation for platinum resistance indicates that there is a significant deviation of the ITS-90 from thermodynamic values over the range 80 K to 270 K. The deviation is consistent with recent results in acoustic and gas thermometry, namely around 10 mK at 150 K. For this reason a re-evaluation of the existing thermodynamic data on the temperature scale appears warranted.

Universality in the resistivity-temperature relationship for decagonal quasicrystals.

The temperature T dependence of the resistivity of decagonal single quasicrystals available at present has been carefully examined from 77 to 340 K. All the samples show a precisely linear T dependence of resistivity along the periodic direction, while in the quasicrystalline plane a quadratic term was added to fit the data. The linear T dependence in the large temperature range implies a very low transport Debye temperature, and can be easily understood by the nearly filled band model used to explain Hall-effect anisotropy. The T dependence of the resistivity in the quasicrystalline plane can be satisfactorily explained by the generalized Faber-Ziman theory, proving an enhanced electron-phonon interaction and an enhanced phonon-phonon coupling in the quasicrystalline plane.

Fabrication of diamond thin-film thermistors for high-temperature applications

CVD diamond thin-film thermistors have been fabricated in various geometries and at different doping levels in an effort to achieve practical resistance- vs.-temperature characteristics. Typical activation energy values reported for polycrystalline films were combined with a targeted resistance range to plot an idealized relationship between resistance and temperature for CVD diamond thin films. The optimum device geometry and boron concentration were subsequently approximated from these ideal plots. Fabricated devices were electrically characterized in air at temperatures ranging from 25°C to over 500°C. Repeatability was demonstrated over two temperature cycles and stability was maintained at 500°C for 9 h. Effects of varying thermistor geometry and boron dopant concentration to achieve useful resistance-temperature relationships will be discussed.

Correlation between Carrier Concentration and Superconductivity in the 123-phase System

Besides the structure and oxygen content, the resistance-temperature relationship, Hall carrier concentration (nH) and midpoint temperature of superconducting transition (Tc) were measured for more than six 123-phase systems with elemental substitution. No correlation is found between the oxygen content and Tc, nor is between the orthorhombic structure and Tc. Instead, an unmonotonic relationship is found between nH and Tc. The optimum nH for the highest Tc is about 3.8 × 1021 cm-3. All this draws a conclusion that nH is a parameter to describe the high Tc superconductivity.

AN XPS STUDY ON Y-Ba-Cu-Al-O SYSTEM

The XPS, oxygen content and resistance-temperature relationship of YBa2Cu3-xAlxO7-y single phase system are determined. The experimental results show that Al can possibly substitute the Cu and Y positions in 1-2-3-phase partially. Because of the existence of Al3+, the content of oxygen increases, the environment of oxygen tends to be uniform, the difference of the two states of O15 in XPS is indistinct. The presence of Cu3+ is clearly observed.

High-Temperature Superconducting Y-Ba-Cu-O Thin Film by using Ionized Cluster Beam Method

ABSTRACTHigh-temperature superconducting Y-Ba-Cu-O films were obtained for the first time by using the ionized cluster beam (ICB) method. It was confirmed that the films resulted in superconductor showing the zero resistance at the temperature above 7 7K.Three ICB sources were used to control the composition of the film, where ionized each cluster of Y, Ba and Cu was ejected simultaneously from the sources to the MgO substrate in high vacuum. The grown film annealed at 930 °C in oxygen atmosphere showed superconducting behaviour in electrical resistance-temperature relationship. The transition temperature to a superconducting state depends on the voltage to accelerate ionized cluster beams and film thickness. The highest temperature obtained to date is 89K.

The conduction mechanism of polymer–filler particles

AbstractIn this paper, the electrical properties and the conductive mechanism of polymer‐filler particles are discussed using polymer‐grafted carbon black. Resistors with resistivities in the range of ca. 10–108 Ω cm were made, and the resistance–temperature relationship was measured between 77 and 298° K. In this temperature range, the resistance decreased with an increase of temperature, suggesting that the electrical conduction is thermally activated. The resistance as a function of field strength was measured by a pulse method. The resistor was a resistivity of ca. 104 Ω cm showed field dependence, and the change of resistance was reversible. It was found that the resistance was independent of temperature at high field strength, and tunneling conduction is predominant. On the basis of these facts, theoretical equations were derived and compared with the experimental values.

Properties of industrial-grade platinum–cobalt resistance thermometers between 1 and 27 K

The stability at 20 K of five industrial-type platinum–cobalt resistance thermometers on thermal cycling has been studied together with their resistance-temperature characteristics between 1 and 27 K and their self-heating. The stability at 20 K on cycling between room temperature and 20 K is of the order of 10 mK and on cycling between 100 and 20 K is a few mK. Differences in the resistance-temperature relationships of the thermometers are very small, but the self-heating effects are relatively large, particularly below 4 K.