Showing papers on "Van der Pauw method published in 2020"

Reconciliation of Experiments and Theory on Transport Properties of Iron and the Geodynamo.

Abstract: We measure the electrical resistivity of hcp iron up to ∼170 GPa and ∼3000 K using a four-probe van der Pauw method coupled with homogeneous flattop laser heating in a DAC, and compute its electrical and thermal conductivity by first-principles molecular dynamics including electron-phonon and electron-electron scattering. We find that the measured resistivity of hcp iron increases almost linearly with temperature, and is consistent with our computations. The results constrain the resistivity and thermal conductivity of hcp iron to ∼80±5 μΩ cm and ∼100±10 W m^{-1} K^{-1}, respectively, at conditions near the core-mantle boundary. Our results indicate an adiabatic heat flow of ∼10±1 TW out of the core, supporting a present-day geodynamo driven by thermal and compositional convection.

Simple analytical method for determining electrical resistivity and sheet resistance using the van der Pauw procedure.

Abstract: This work reports an analytical method for determining electrical resistivity (ρ) and sheet resistance (RS) of isotropic conductors. The method is compared with previous numerical solutions and available experimental data showing a universal behavior for isotropic conductors. An approximated solution is also reported allowing one to easily determine ρ and RS for samples either with regular or arbitrary shapes.

Approaches to Measure the Resistivity of Grain Boundaries in Metals with High Sensitivity and Spatial Resolution: A Case Study Employing Cu.

Abstract: It is well-known that grain boundaries (GBs) increase the electrical resistivity of metals due to their enhanced electron scattering. The resistivity values of GBs are determined by their atomic structure; therefore, assessing the local resistivity of GBs is highly significant for understanding structure-property relationships. So far, the local electrical characterization of an individual GB has not received much attention, mainly due to the limited accuracy of the applied techniques, which were not sensitive enough to detect the subtle differences in electrical resistivity values of highly symmetric GBs. Here, we introduce a detailed methodology to probe in situ or ex situ the local resistivity of individual GBs in Cu, a metallic model system we choose due to its low resistance. Both bulk Cu samples and thin films are investigated, and different approaches to obtain reliable and accurate resistivity measurements are described, involving the van der Pauw technique for macroscopic measurements as well as two different four-point-probe techniques for local in situ measurements performed inside a scanning electron microscope. The in situ contacts are realized with needles accurately positioned by piezodriven micromanipulators. Resistivity results obtained on coincidence site lattice GBs (incoherent Σ3 and asymmetric Σ5) are reported and discussed. In addition, the key experimental details as well as pitfalls in the measurement of individual GB resistivity are addressed.

Evaluation of the Sheet Resistance of Inkjet-Printed Ag-Layers on Flexible, Uncoated Paper Substrates Using Van-der-Pauw’s Method

Abstract: With the growing significance of printed sensors on the electronics market, new demands on quality and reproducibility have arisen. While most printing processes on standard substrates (e.g., Polyethylene terephthalate (PET)) are well-defined, the printing on substrates with rather porous, fibrous and rough surfaces (e.g., uncoated paper) contains new challenges. Especially in the case of inkjet-printing and other deposition techniques that require low-viscous nanoparticle inks the solvents and deposition materials might be absorbed, inhibiting the formation of homogeneous conductive layers. As part of this work, the sheet resistance of sintered inkjet-printed conductive silver (Ag-) nanoparticle cross structures on two different, commercially available, uncoated paper substrates using Van-der-Pauw's method is evaluated. The results are compared to the conductivity of well-studied, white heat stabilised and treated PET foil. While the sheet resistance on PET substrate is highly reproducible and the variations are solely process-dependent, the sheet resistance on uncoated paper depends more on the substrate properties themselves. The results indicate that the achievable conductivity as well as the reproducibility decrease with increasing substrate porosity and fibrousness.

Low Thermal Budget Heteroepitaxial Gallium Oxide Thin Films Enabled by Atomic Layer Deposition.

Abstract: This work explores the applicability of atomic layer deposition (ALD) in producing highly oriented crystalline gallium oxide films on foreign substrates at low thermal budgets. The effects of substrate, deposition temperature, and annealing process on formation of crystalline gallium oxide are discussed. The Ga2O3 films exhibited a strong preferred orientation on the c-plane sapphire substrate. The onset of formation of crystalline gallium oxide is determined, at which only two sets of planes, i.e., α-Ga2O3 (006) and β-Ga2O3 (402), are present parallel to the surface. More specifically, this work reports, for the first time, that epitaxial gallium oxide films on sapphire start to form at deposition temperatures ≥ 190 °C by using an optimized plasma-enhanced ALD process such that α-Ga2O3 (006)∥α-Al2O3 (006) and β-Ga2O3 (201)∥α-Al2O3 (006). Both α-Ga2O3 (006) and β-Ga2O3 (201) planes are polar planes (i.e., consisting of only one type of atom, either Ga or O) and, therefore, favorable to form by ALD at such low deposition temperatures. Ellipsometry and van der Pauw measurements confirmed that the crystalline films have optical and electrical properties close to bulk gallium oxide. The film grown at 277 °C was determined to have superior properties among as-deposited films. Using TEM to locate α-Ga2O3 and β-Ga2O3 domains in the as-deposited crystalline films, we proposed a short annealing scheme to limit the development of α-Ga2O3 domains in the film and produce pure β-Ga2O3 films via an energy-efficient process. A pure β-Ga2O3 phase on sapphire with β-Ga2O3 (201)∥α-Al2O3 (006) was successfully achieved by using the proposed process at the low annealing temperature of 550 °C preceded by the low deposition temperature of 190 °C. The results of this work enable epitaxial growth of gallium oxide thin films, with superior material properties offered by ALD, not only with potential applications as a high-performance material in reducing global energy consumption but also with an energy-efficient fabrication process.

One-Dimensional Nanostructures of Polypyrrole for Shielding of Electromagnetic Interference in the Microwave Region

Abstract: Polypyrrole one-dimensional nanostructures (nanotubes, nanobelts and nanofibers) were prepared using three various dyes (Methyl Orange, Methylene Blue and Eriochrome Black T). Their high electrical conductivity (from 17.1 to 60.9 S cm-1), good thermal stability (in the range from 25 to 150 °C) and resistivity against ageing (half-time of electrical conductivity around 80 days and better) were used in preparation of lightweight and flexible composites with silicone for electromagnetic interference shielding in the C-band region (5.85-8.2 GHz). The nanostructures' morphology and chemical structure were characterized by scanning electron microscopy, Brunauer-Emmett-Teller specific surface measurement and attenuated total reflection Fourier-transform infrared spectroscopy. DC electrical conductivity was measured using the Van der Pauw method. Complex permittivity and AC electrical conductivity of respective silicone composites were calculated from the measured scattering parameters. The relationships between structure, electrical properties and shielding efficiency were studied. It was found that 2 mm-thick silicone composites of polypyrrole nanotubes and nanobelts shield almost 80% of incident radiation in the C-band at very low loading of conductive filler in the silicone (5% w/w). Resulting lightweight and flexible polypyrrole composites exhibit promising properties for shielding of electromagnetic interference in sensitive biological and electronic systems.

Doping of silicon by phosphorus end-terminated polymers: drive-in and activation of dopants

Abstract: An effective doping technology for the precise control of P atom injection and activation into a semiconductor substrate is presented. Polystyrene polymers with a narrow molecular weight distribution and end-terminated with a P containing moiety are used to build up a phosphorus δ-layer to be used as the dopant source. P atoms are efficiently injected into the Si substrate by high temperature (900–1250 °C) thermal treatments. Temperature dependent (100–300 K) resistivity and Hall measurements in the van der Pauw configuration demonstrate high activation rates (ηa > 80%) of injected P atoms. This bottom-up approach holds promise for the development of a mild technology for efficient doping of semiconductors.

Effect of Doping and Annealing on Thermoelectric Properties of Bismuth Telluride Thin Films

Abstract: This work investigates the thermoelectric and electrical performance of nanostructured thin films of antimony (Sb)-doped Bi2Te3 (thickness ∼ 60 nm) and Bi0.5Sb1.5Te3 (thickness ∼ 60 nm). The films were deposited on a glass substrate by thermal evaporation under high vacuum conditions. The structure and morphology of the films was investigated by standard characterization techniques. X-ray diffraction was used to identify the formation of different phases during the synthesis of the films. The Van der Pauw and Harman methods were employed to measure the conductivity (σ) and figure of merit (ZT). Further, samples were subjected to annealing under a high vacuum at 200°C for 1 h to improve the quality and ZT of the deposited films. The Sb-doped Bi2Te3 film was found to be ∼ 6.5 times more conductive than the Bi0.5Sb1.5Te3 film. However, the two films exhibited comparable ZT values owing to the small value of the Seebeck coefficient (S) of Sb. This study represents a significant contribution in the field of thermoelectric materials and device applications.

DC Magnetron-Sputtered Mo Thin Films with High Adhesion, Conductivity and Reflectance

Abstract: The main challenge in the deposition of molybdenum thin films for high efficiency in copper indium gallium selenide (CIGS) modules lies in gaining an adherent coating without compromising conductivity and reflectance characteristics. In this study, Mo thin films were deposited on soda-lime glass by DC magnetron sputtering at different deposition power (55, 100, 200 and 300 W) and with high working gas pressure (2 and 4 Pa). Analytical techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and Hall effect were employed to analyze the structure, morphology and electrical resistivity of the deposited films. Ultraviolet–visible (UV–Vis) spectrometry was performed to measure the reflectance and a cross-hatch adhesion tape test was employed to determine the adhesion behavior of deposited films. With higher sputtering power and reduced gas pressure, an increase in the crystallite size of the deposited films was observed. Films deposited at higher gas pressure were found with tensile stresses and higher adhesion with the substrate. The van der Pauw method reveals an increase in conductivity at high power and low gas pressure. Improved reflectance was achieved at moderate sputtering power and low gas pressure.

A setup to measure the Seebeck coefficient and electrical conductivity of anisotropic thin-films on a single sample.

Abstract: This work documents an all-in-one custom setup that allows us to measure the in-plane Seebeck coefficients and electrical conductivities of anisotropic thin film samples close to room temperature. Both pairs, S∥ and σ∥ and S⊥ and σ⊥, can be measured using four contacts on the same sample, reducing measurement time and minimizing potential sources of error due to aggregating data from several distinct samples. The setup allows us to measure the electrical conductivity of isotropic samples using the well-known van der Pauw method. For samples with in-plane anisotropy, the two components σ∥ and σ⊥ can be extracted from the same type of measurements by performing additional calculations. Using the same contacts, the Seebeck coefficient along one direction is measured using a differential steady-state method. After rotating the sample by 90°, the orthogonal Seebeck component can be measured. In order to show the generality of the method, we measure different types of samples, from metal references to oriented doped conjugated polymers.

Van der Pauw device used to investigate the thermoelectric power factor.

Abstract: In this paper, we describe a measuring system based on the Van der Pauw principle with four calibrated type S thermocouples. By means of this system, we conducted traceable measurements of the absolute Seebeck coefficients and the electrical conductivity of thermoelectric bulk materials to establish a precise determination of the power factor. The results of a comparative investigation of metallic (ISOTAN® and Nickel) and semiconducting (SiGe) materials in the temperature range of 300 K–1100 K are presented. The good agreement of the Seebeck coefficients and electrical conductivities measured using the system and the data reported from the literature and values of these transport properties premeasured using another measuring system forms the basis for the usage of the system for the further certification of thermoelectric reference materials for the power factor up to 1100 K.

Effect of Pb(Zr0.52Ti0.48)O3 thin films on electron transport at the LaAlO3/SrTiO3 interface by surface acoustic waves

Abstract: Surface acoustic waves (SAWs) are capable tools for providing mechanical control over the electronic properties of functional materials. Coupling SAWs with the LaAlO3/SrTiO3 (LAO/STO) conducting interface is particularly interesting as this interface exhibits extraordinary features, such as high mobility at low temperature, ferromagnetism, and superconductivity below 200 mK. For SAW generation, piezoelectricity is indispensable, and due to lack of that in the LAO/STO system, a 200 nm thick Pb(Zr0.52Ti0.48)O3 (PZT) film was grown on top of LAO. SAW excitation and propagation was demonstrated on a PZT/LAO/STO multilayer structure. We further employed SAWs in order to transport free electrons confined to the LAO/STO interface, detected as an acoustoelectric voltage at room temperature. Electrical characterization of the interface was carried out by Van der Pauw measurements. We found that having a PZT layer on top of LAO/STO considerably degraded the interfacial conductivity. The degradation became more pronounced at low temperatures. We attribute these effects to the filling of oxygen vacancies due to interlayer oxygen migration, combined with carrier freeze-out at low temperatures.

Achieving near-zero temperature coefficient of resistivity in atomic layer deposition TiSixN films through composition tuning

Abstract: Atomic layer deposition (ALD) is used to systematically vary the composition of TiSixN films by modulating the ratio of Ti and Si precursors with NH3 as a coreactant. The as-synthesized films have varying atomic (at.) % Si (0 ≤ x ≤ 24.2) to provide both metallic (i.e., TiN) and insulating (i.e., Si3N4) behavior. The competing material properties reduce the temperature coefficient of resistivity (TCR) of the film, thereby generating a regime where electrical conductance is independent of temperature. The TiSixN (Si = 3.4 at. %) film with 139.6 nm thickness exhibits a near-zero TCR of −23 ppm K−1, between 298 and 398 K, and a resistivity of 348.1 μΩ cm. Materials characterization using x-ray reflectometry, x-ray diffraction, x-ray photoelectron spectroscopy, and Raman spectroscopy, in conjunction with van der Pauw measurement and spectroscopic ellipsometry, are conducted to characterize film properties. Correlating structural, electrical, and optical properties provides insights into the electronic interactions of TiN with Si3N4, synthesized as an ALD nanocomposite thin film.

Acoustoelectric Study of Microwave-Induced Current Domains.

Abstract: Surface acoustic waves (SAW) have been utilized to investigate the properties of a two-dimensional electron system subjected to a perpendicular magnetic field and monochromatic microwave radiation in the regime where the so-called microwave-induced zero-resistance states form. Contrary to conventional magnetotransport in Hall bar and van der Pauw geometries, the collimated SAW beam probes only the bulk of the electronic system exposed to this wave. Clear signatures appear in the SAW propagation velocity, corroborating that neither contacts nor sample edges are a root source for their emergence. By virtue of the directional nature of this probing method and with the assistance of theoretical modeling, we were able to demonstrate that the SAW response depends on the angle between its propagation vector and the orientation of domains that spontaneously form when zero-resistance is observed in transport. This confirms in unprecedented manner the formation of an inhomogeneous phase under these nonequilibrium conditions.

Synthesis and Characterization of Gallium Oxide/Tin Oxide Nanostructures via Horizontal Vapor Phase Growth Technique for Potential Power Electronics Application

Abstract: The monoclinic β-gallium oxide (Ga2O3) was viewed as a potential candidate for power electronics due to its excellent material properties. However, its undoped form makes it highly resistive. The Ga2O3/SnO2 nanostructures were synthesized effectively via the horizontal vapor phase growth (HVPG) technique without the use of a magnetic field. Different concentrations of Ga2O3 and SnO2 were varied to analyze and describe the surface morphology and elemental composition of the samples using the scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) spectroscopy, respectively. Meanwhile, the polytype of the Ga2O3 was confirmed through the Fourier transform infrared (FTIR) spectroscopy. The current-voltage (I–V) characteristics were established using a Keithley 2450 source meter. The resistivity was determined using the van der Pauw technique. The mobility and carrier concentration was done through the Hall effect measurements at room temperature using a 0.30-Tesla magnet. It was observed that there was an increase in the size of the nanostructures, and more globules appeared after the concentration of SnO2 was increased. It was proven that the drop in the resistivity of Ga2O3 was due to the presence of SnO2. The data gathered were supported by the Raman peak located at 662 cm−1, attributed to the high conductivity of β-Ga2O3. However, the e-polytype was verified to appear as a result of adding SnO2. All the samples were considered as n-type semiconductors. High mobility, low power loss, and low specific on-resistance were attained by the highest concentration of SnO2. Hence, it was clinched as the optimal n-type Ga2O3/SnO2 concentration and recommended to be a potential substrate for power electronics application.

Conduction and Electric Field Effect in Ultra-Thin Tungsten Films

Abstract: Ultra-thin tungsten films were prepared using hotwire assisted atomic layer deposition. The film thickness ranged from 2.5 to 10 nm, as determined by spectroscopic ellipsometry and verified by scanning electron microscopy. The films were implemented in conventional Van der Pauw and circular transmission line method (CTLM) test structures, to explore the effect of film thickness on the sheet and contact resistance, temperature coefficient of resistance (TCR), and external electric field applied. All films exhibited linear current-voltage characteristics. The sheet resistance was shown to considerably vary across the wafer, due to the film thickness non-uniformity. The TCR values changed from positive to negative with decreasing the film thickness. A field-induced modulation of the sheet resistance up to $\sim 4.6\cdot 10^{-4}\,\,\text{V}^{-1}$ was obtained for a 2.5 nm thick film, larger than that generally observed for metals.

Growth and anisotropic transport properties of off-axis MgB2 thin films

Abstract: Off-axis MgB2 thin films with c-axis tilted away from the film normal have been fabricated on MgO (211) substrate via a hybrid physical-chemical vapor deposition method. Microscopy images show that the film surface is characterized by terrace steps, which, in line with the x-ray diffraction experiment, demonstrates the tilted growth of the film. To probe the resistivity anisotropy resulted from this tilted growth, resistance measurements in Van der Pauw configuration have been performed. By refining an equivalent-circuit model proposed previously to simulate the measurement, the anisotropy ratio ρT/ρL is estimated, where ρT or ρL is the resistivity transverse or parallel to the terrace steps respectively. The validity of the estimation has been checked by direct measurements of ρT and ρL in standard linear-four probe configuration, which are performed by patterning microbridges from the film along or across the terrace steps. The patterned microbridges also enable us to measure the anisotropy of the superconducting critical current density Jc, which shows that Jc,L parallel to the terrace steps is higher than Jc,T transverse to the terrace steps and the anisotropy ratio Jc,L/Jc,T decreases as temperature increases, following a simple [ 1 + ( T / T c ) 2 ] − 1 / 2 dependence with Tc the superconducting transition temperature. The results are discussed under the framework of multiband transport of MgB2 which exhibits anisotropy between the crystallographic c-axis and ab-plane because of the anisotropic contribution of the σ bands.

Generalized Gated Four-Probe Method for Intrinsic Mobility Extraction With Van Der Pauw Structure

Abstract: Measuring the mobility of thin-film transistors fabricated using newly developed semiconductors is difficult because of various factors, such as contact resistance. In this work, the generalized gated four-probe and van der Pauw structure were combined to precisely measure the carrier mobility of semiconductors. The method is geometry-independent, suitable for gate-dependent mobility in all operation regimes, and the test devices could be easily fabricated. Experimental verifications were performed on specially designed InGaZnO devices with different electrodes and at various temperatures. The developed approach enables simple and precise investigation of the semiconductor’s properties via easily fabricated devices. In particular, the technique could be used for newly developed semiconductors that can only be patterned via low-resolution techniques, such as shadow mask patterning.

Using a Natural Ratio to Compare DC and AC Resistances

Abstract: The simulation and construction of a direct current (dc) and alternating current (ac) resistor, based on a silicon wafer, has been described and demonstrated. By applying the van der Pauw (vdP) method, and the Thompson–Lampard (TL) theorem, to within approximations accommodating the conditions of the resistor’s construction, a constant resistance ratio, ( $\pi $ /ln2)2, was derived that is independent of the sample resistivity, and thickness. The constant ratio, valued at approximately 20.5, can theoretically be used as a basis of comparison between two distinct calibration chains, one based on the traceability from a calculable capacitor (CC), and the other based on the quantum Hall effect. To support the calculated ratio, several sets of simulations were performed for both dc and ac cases. The dc simulation results agreed with the ratio value to within 0.035% when using a wafer thickness of 0.53 mm. Additionally, the experimental dc and ac (1 kHz) results agreed with the calculated ratio value to within 0.23%, with not more than 0.06% standard uncertainty before point contact errors from device fabrication.

Optimization of AlN spacer layer in MOVPE grown AlGaN/AlN/InGaN/GaN high electron mobility heterostructure

Abstract: High electron mobility heterostructure AlGaN/AlN/InGaN/GaN, employing InGaN as the channel were grown using metal organic vapor phase epitaxy (MOVPE). In different samples, the AlN spacer layers were grown differently but at the temperature that were used for growth of InGaN channel i.e. at low temperature (LT) ~ 720°C. The grown samples were characterized using photoluminescence (PL), atomic force microscope (AFM) and Van der Pauw Hall measurement. As a result of optimization of AlN spacer, a significant improvement in rms surface roughness from Rq ~ 3.87 nm to Rq ~ 0.82 nm was obtained. The corresponding improvement in mobility of 2DEG was from µ ~ 39 cm2/V·s to µ ~ 201 cm2/V·s. The results show that optimum growth condition of LT AlN in such InGaN channel heterostructures should be decided on the basis of a reasonable trade-off between surface roughness and the transport properties of 2DEG.

An apparatus for measuring water content of unsaturated soil based on the van der Pauw principle

Abstract: Understanding water migration in soil specimens under triaxial test conditions is of great significance for investigating the mechanism of distress in railway subgrades. However, the water content distribution along the specimen height is difficult to determine with current equipment. Motivated by such limitations, we developed an apparatus relying on the van der Pauw principle, to measure the water content based on the specimen’s electrical properties. Additionally, a series of exploratory tests on unsaturated soil specimens were conducted to evaluate the performance of this apparatus. To verify the practicability of the apparatus, a water-supply dynamic triaxial test was also carried out with an unsaturated dynamic triaxial test system (GDS). The results indicate that this apparatus is stable, as the measurement accuracy is not influenced by the electrode position or the soil geometry or dimensions. In a narrow triaxial pressure chamber, this apparatus can be used to determine the distribution of water content in unsaturated specimens nondestructively and consecutively during a triaxial test. The maximum error obtained from the apparatus when measuring the gravimetric water content was 0.7%. The soil resistivity calculation function was obtained considering the dry density and gravimetric water content with high correlation and precision. This apparatus has broad applications for investigating the mechanism of water migration within some geotechnical materials.

Electrical Properties 1

Abstract: Studies of Si, Ge donors and Fe, Mg as acceptors in β-Ga2O3 through temperature-dependent van der Pauw and Hall effect measurements of samples grown by a variety of methods are presented in this chapter. Si and Ge are identified as shallow donors with donor energy of 30 meV instead of DX states. Fe is a deep acceptor with its energy level 860 meV below the conduction band edge. Mg-doped samples present an activation energy of 1.1 eV, but the type could not be resolved. Unintentional donors and acceptors are also discussed including intrinsic defects (i.e., vacancies) and extrinsic impurities. Last, an unintentional donor with energy of 110 meV is presented and the impacts of its incomplete ionization to power devices are discussed.

Method for measuring resistivity of metallic iron under ultrahigh pressure

Abstract: The invention discloses a method for measuring resistivity of metallic iron under ultrahigh pressure. The method comprises the following steps that a high-purity iron sheet and a rhenium sheet are machined into a circular sample and a rectangular part by using a laser cutting machine respectively; the rhenium sheet is used as a heater, and the circular iron sheet, three tungsten wires and a tungsten-rhenium alloy wire are placed into an ultrahigh pressure testing device to be assembled; a test assembly block is placed in a cubic press, and is loaded to specified pressure and temperature, and the resistivity of the sample is measured and recorded by adopting a four-probe van der Pauw principle; after heating and data recording are completed, pressure is unloaded; and the circular iron sheetsample is taken out, fixed with epoxy resin, cut, ground and polished to obtain a longitudinal section of the circular iron sheet, the thickness is measured, and resistivity values of the metal ironsheet under different temperature and pressure conditions are calculated by using a van der Pauw measurement method formula. The problems that in the prior art, the temperature gradient is large, temperature measurement is inaccurate, measurement wires make contact with one another, resistivity calculation parameters are excessive, and errors are large are solved.

Method for measuring resistivity of metal iron sheet under high temperature and high pressure

Abstract: The invention discloses a method for measuring resistivity of a metal iron sheet under high temperature and high pressure. The method comprises the following steps that a high-purity iron sheet and arhenium sheet are machined into a circular sample and a rectangular part by using a laser cutting machine respectively; the rhenium sheet is used as a heater, and the circular iron sheet and four high-purity tungsten wires are placed into a high-temperature and high-pressure testing device to be assembled; a test assembly block is placed in a cubic press, and is loaded to specified pressure and temperature, the resistivity of the sample is measured and recorded by adopting a four-probe van der Pauw principle, and the temperature is measured with a separate thermocouple; after heating and datarecording are completed, pressure is unloaded; and the circular iron sheet sample is taken out, fixed with epoxy resin, cut, ground and polished to obtain a longitudinal section of the circular iron sheet, the thickness is measured, and resistivity values of the metal iron sheet under different temperature and pressure conditions are calculated by using a van der Pauw measurement method formula. The problems that in the prior art, the temperature gradient is large, temperature measurement is inaccurate, measurement wires make contact with one another, resistivity calculation parameters are excessive, and errors are large are solved.