Van Der Pauw Method Research Articles

Electrical Conductivity of (Mg, Fe)CO3 at the Spin Crossover and Its Implication for Mid‐Mantle Geomagnetic Heterogeneities

Abstract(Mg, Fe)CO3 is an important deep carbon carrier and plays a vital role in our understanding of lower‐mantle carbon reservoirs. The electrical conductivity (EC) of FeCO3 was measured at 126−2000 K up to 83 GPa in diamond‐anvil cells using a standard four‐probe van der Pauw method. Moreover, the EC of FeCO3 increases by ∼6 orders of magnitude from 300 to 1500 K at 10−20 GPa, indicating a strong effect of high temperature. The EC of Fe0.65Mg0.35CO3 was measured up to 60 GPa at 300 K, the EC values of (Mg, Fe)CO3 are proportional to iron content and increase by 2–3 orders of magnitude at 300 K across the spin crossover. The EC values of (Mg, Fe)CO3 and FeCO3 + Fe3O4 ± C mixtures surpass that of bridgmanite, ferropericlase and davemaoite by ∼1–4 orders of magnitude at depths of 800–2,000 km. This result sheds insights into the genesis of local geomagnetic heterogeneities in the mid‐lower mantle.

Addressing Mobility Overestimation in Short-Channel IGZO TFTs Using the Gated Van der Pauw Method.

The determination of field-effect mobility in indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) is pivotal for advancing high-performance electronic devices. However, accurately evaluating the field-effect mobility in IGZO-TFTs with short channel lengths of less than a few micrometers poses a formidable challenge. This difficulty arises due to the increasing significance of contact resistance in the total resistance as the channel length decreases. Consequently, increasing contact resistance can lead to inaccurate sheet resistance values, resulting in overestimating critical parameters, such as mobility and contact resistance, during device evaluations. Therefore, a precise method for extracting sheet resistance, an intrinsic channel characteristic, is imperative for short-channel IGZO TFTs. Herein, a gated van der Pauw (gVDP) method was employed to extract sheet resistance precisely and independently of contact resistance. This contact-resistance-independent approach mitigates the risk of overestimating charge behaviors in IGZO TFTs. Furthermore, it facilitates precise evaluations of intrinsic channel mobility, enabling accurate predictions of the maximum performance of devices with short channels.

In-Situ Coating of Iron with a Conducting Polymer, Polypyrrole, as a Promise for Corrosion Protection

Iron microparticles were coated with polypyrrole in situ during the chemical oxidation of pyrrole with ammonium peroxydisulfate in aqueous medium. A series of hybrid organic/inorganic core–shell materials were prepared with 30–76 wt% iron content. Polypyrrole coating was revealed by scanning electron microscopy, and its molecular structure and completeness were proved by FTIR and Raman spectroscopies. The composites of polypyrrole/carbonyl iron were obtained as powders and characterized with respect to their electrical properties. Their resistivity was monitored by the four-point van der Pauw method under 0.01–10 MPa pressure. In an apparent paradox, the resistivity of composites increased from the units Ω cm for neat polypyrrole to thousands Ω cm for the highest iron content despite the high conductivity of iron. This means that composite conductivity is controlled by the electrical properties of the polypyrrole matrix. The change of sample size during the compression was also recorded and provides a parameter reflecting the mechanical properties of composites. In addition to conductivity, the composites displayed magnetic properties afforded by the presence of iron. The study also illustrates the feasibility of the polypyrrole coating on macroscopic objects, demonstrated by an iron nail, and offers potential application in the corrosion protection of iron. The differences in the morphology of micro- and macroscopic polypyrrole objects are described.

Thermal and Dynamo Evolution of the Lunar Core Based on the Transport Properties of Fe‐S‐P Alloys

AbstractPaleomagnetic analyses have suggested that the lunar magnetic field underwent a significant change from 4.25 to 3.19 Ga, indicating the rapid transition of the lunar dynamo mechanism. We used the van der Pauw (vdP) method to measure the electrical resistivity of Fe‐S‐P alloys under conditions relevant to the lunar core and estimated the thermal conductivity of the Fe‐S‐P lunar core. These values were incorporated into thermal and dynamo models to investigate the evolution of the lunar core. Our model indicates that the inner core began to grow as early as 4.35 Ga, the solidification regime switched at 3.50 Ga, and the thermal dynamo ceased between 3.78 and 3.51 Ga. The cessation of the dynamo could be due to a low buoyancy flux and insufficient entropy dissipation. Thermal and compositional dynamos cannot sustain the ancient strength of the Moon's magnetic field, and require other energy sources.

Assessment of the Influence of Fabric Structure on Their Electro-Conductive Properties.

Electro-conductive fabrics are key materials for designing and developing wearable smart textiles. The properties of textile materials depend on the production method, the technique which leads to high conductivity, and the structure. The aim of the research work was to determine the factors affecting the electrical conductivity of woven fabrics and elucidate the mechanism of electric current conduction through this complex, aperiodic textile material. The chemical composition of the material surface was identified using scanning electron microscopy energy dispersion X-ray spectroscopy. The van der Pauw method was employed for multidirectional resistance measurements. The coefficient was determined for the assessment of the electrical anisotropy of woven fabrics. X-ray micro-computed tomography was used for 3D woven structure geometry analysis. The anisotropy coefficient enabled the classification of electro-conductive fabrics in terms of isotropic or anisotropic materials. It was found that the increase in weft density results in an increase in sample anisotropy. The rise in thread width can lead to smaller electrical in-plane anisotropy. The threads are unevenly distributed in woven fabric, and their widths are not constant, which is reflected in the anisotropy coefficient values depending on the electrode arrangement. The smaller the fabric area covered by four electrodes, the fewer factors leading to structure aperiodicity.

Optical and electrical properties of Al-doped ZnO thin films deposited by sol-gel method

The multilayer (10 layers) Al doped ZnO (AZO) thin films were deposited on glass substrate by sol-gel & dipping method. X-Ray diffraction measurements showed that the AZO films were polycrystalline with a hexagonal wurtzite structure. The morphological properties of the films were analyzed by atomic force microscopy showing continuous and homogeneous film, completely covering the substrates. The thickness, optical constants, optical band gap (Eg) and transmittance (T) of AZO films were assessed by spectroscopic ellipsometry on UV-vis-NIR spectral range. The AZO film has high transmittance above 80% in the visible region and the optical band-gap energy around 3.7 eV. The electrical characteristics regarding conductivity, mobility and carrier concentrations, were measured by Hall Effect measurements (van der Pauw method). The bulk carrier concentration of the AZO film with 10 layers was found to be 1.16x1019 cm-3. The vibrational bands were obtained by Raman analysis. Defects due to oxygen vacancies in the prepared AZO films were evidenced by photoluminescence spectroscopy (PL). The optical and electrical properties of the AZO thin films proved the possibility to be used in optoelectronic applications.

Lorenz number and transport properties of Fe: Implications to the thermal conductivity at Earth's core-mantle boundary

Abstract The electrical resistivity (ρ) and thermal conductivity (κ) of the Earth's core compositions are essential parameters for constraining the core's thermal state, the inner core age, and the evolutionary history of the geodynamo. However, controversies persist between experimental and computational results regarding the electronic transport properties (ρ and κ) of the Earth's core. Iron is the major element in the core, and its transport properties under high pressure and high temperature conditions are crucial for understanding the core's thermal state. We measured the ρ values of solid iron using the four-wire van der Pauw method at 300 K and pressures ranging from 3 to 26 GPa within a multi-anvil press. For comparison, we calculated the ρ and κ values of hexagonal close-packed (hcp) iron at conditions of 300-4100 K and 22-136 GPa using the first-principles molecular dynamics (FPMD) method. Our calculations generally align with prior studies, indicating that the electrical resistivity of solid hcp iron at Earth's core-mantle boundary (CMB) conditions is ~76-83 μΩ∙cm. The resistivity of hcp iron changes small as it melts from solid to liquid at pressures from 98 to 134 GPa. The impact of temperature and pressure on the Lorenz numbers of solid hcp iron are investigated according to our calculation results and previous studies. Under the CMB's pressure conditions, the κ of hcp iron initially decreases with increasing temperature and subsequently increases. The electron-electron scattering plays a dominant role at low temperatures and causes the decrease in κ. At high temperatures, the increase of electronic specific heat significantly increases the Lorentz number and κ. Overall, we estimate the κ of solid hcp iron at CMB's condition to be 114 ± 6 W/m/K, slightly lower than the room temperature value of 129 ± 9 W/m/K at the same pressure. Our model shows that a 0-525 km thickness of a thermally stratified layer may exist beneath the Earth's CMB depending on the core's heat flow and thermal conductivity.

Electrophysical properties of silicon doped with lutetium

This article discusses the electrical properties of silicon doped with lutetium. The diffusion method is used in the fabrication of silicon structures doped with lutetium. n-Si, p-Si, n-Si<Lu> and p-Si<Lu> were prepared to measure electrophysical parameters. The resistivity of the samples, the mobility of charge carriers, the concentration and the distribution of electrophysical parameters depending on the temperature and thickness of the sample have been studied. These parameters were determined by the four-probe van der Pauw method. Research work was carried out at room temperature and in the range of 77÷300 K. Ohmic contact was obtained through a mixture of 1% Sb + 99% Au for measuring samples on the HMS500 instrument. The resistivity and concentration of charge carriers were also studied, taken from a distance of 2 µm from the surface of the samples. The electrical parameters of the samples were measured using an Ecopia Hall effect measurement system. The electrical parameters of the p-Si and p-Si<Lu> samples did not change significantly. Changes in the surface morphology of these samples were observed in the results obtained in ACM.

Demonstration of tritium adsorption on graphene.

In this work, we report on studies of graphene exposed to tritium gas in a controlled environment. The single layer graphene on a SiO2/Si substrate was exposed to 400 mbar of T2, for a total time of ∼55 h. The resistivity of the graphene sample was measured in situ during tritium exposure using the van der Pauw method. We found that the sheet resistance increases by three orders of magnitude during the exposure, suggesting significant chemisorption of tritium. After exposure, the samples were characterised ex situ via spatio-chemical mapping with a confocal Raman microscope, to study the effect of tritium on the graphene structure (tritiation yielding T-graphene), as well as the homogeneity of modifications across the whole area of the graphene film. The Raman spectra after tritium exposure were comparable to previously observed results in hydrogen-loading experiments, carried out by other groups. By thermal annealing we also could demonstrate, using Raman spectral analysis, that the structural changes were largely reversible. Considering all observations, we conclude that the graphene film was at least partially tritiated during the tritium exposure, and that the graphene film by and large withstands the bombardment by electrons from the β-decay of tritium, as well as by energetic primary and secondary ions.

Исследование электронных и оптических свойств тонких пленок оксидов меди, осажденных с помощью дугового разряда низкого давления

In this work, thin films of copper oxides obtained by arc deposition at low pressure on borosilicate glass were studied. The phase composition, structural characteristics and chemical state of the samples were confirmed by X-ray diffraction and X-ray photoelectron spectroscopy. Hall measurements using the van der Pauw method showed that films of both Cu2O and CuO phase compositions have hole conductivity (p-type). The concentration of charge carriers, mobility and resistivity of the samples were determined. In a thin film of mixed composition (Cu2O/CuO), the formation of a heterojunction was observed with a significant decrease in the concentration of charge carriers due to the recombination of electron-hole pairs. From UV-visible spectroscopy measurements, the absorption/transmission characteristics of the films are determined and the optical band gap is calculated. It has been shown that changing the phase composition of the oxide from Cu2O to CuO leads to a decrease in the band gap from 1.90 to 1.34 eV.

Effect of oxygen flow on electrical and optical properties of ITO films synthesized by magnetron sputtering method

The tin-doped indium oxide thin films were synthesized by DC magnetron sputtering on the surface of polished silicon samples and glass slides in a mixed argon-oxygen atmosphere. The other deposition parameters: operating pressure, magnetron power and substrate rotation speed were kept constant. Thickness and density of thin films were measured by X-ray Reflectometry. The effects of oxygen flow rate and substrate temperature on the optical and electrical properties were investigated. The electrical properties (resistivity, Hall mobility and charge concentration) of the thin films were measured by the Van der Pauw method using the Hall effect. The minimum value of resistivity 0.52 × 10-3 Ohm·cm, and maximum charge mobility 28 cm2V-1s-1 was achieved at an oxygen proportional gas mixture of 2.6% (0.71 sccm). The transmission spectra of the films were measured in the wavelength range from 300 to 1100 nm. The transmittance of all films exceeds 75% in the visible and near-infrared spectral ranges. It was found that increasing the oxygen flow rate and heating of the substrate up to optimal value 150°C led to an increase in the crystallinity of the films and, consequently, to an increase in the Hall mobility and the transmittance.

Application of the van der Pauw method for electrical conductivity measurements at high temperatures using an insulating compressing ring.

High quality data on the high temperature electrical properties of ceramics, particularly oxides, is of great value for material selection, design, and modeling for a broad range of emerging applications. Utilizing the mismatch in the coefficient of thermal expansion between two materials, a purely mechanical method for establishing electrical contact in the van der Pauw geometry to measure the bulk resistivity of ceramic disks at high temperatures is presented. Measurements of a reference material, 20 mol. % Gd-doped cerium oxide, are presented up to 1000 °C. The viability of electrical measurements up to a maximum temperature of 1600 °C is also considered. Measurements are performed using multiple techniques and compared to literature values finding excellent agreement. The approach described in this work enables the van der Pauw method to be applied to many ceramic materials over a wide range of temperatures and environments.

Measurement of granite resistivity under deep underground conditions based on van der Pauw method

With the growing demand for sustainable energy and infrastructure development in the country, the utilization of deep geothermal resources and the development of deep underground space engineering are becoming more and more important. Under the background that the country vigorously promotes the development of deep rock and soil underground space and the utilization of resources. The experiment will be performed on granite, one of the deep subsurface rocks, a rock type widely used in geotechnical research projects because of its high strength, low permeability and thermal stability. However, its properties under the extreme temperature and chemical conditions deep in the earth are unknown, and how to efficiently convert deep rocks into geothermal resources for utilization is still unknown. Therefore, studying the influence of temperature and chemical corrosion on the resistivity of granite is very important to ensure the safety and durability of underground structures and effectively utilize thermal energy resources in deep underground. This experiment will control the influence of temperature, pressure, chemical corrosion and the comprehensive effect of the three on the resistivity of granite, and indirectly measure the amount of heat absorbed in the granite rock mass. Simulate the deep underground granite under high confining pressure, high ground temperature and corrosion conditions the nature of the performance. Record, count and analyze the data, comprehensively judge the environmental interference of the granite rock formation under actual conditions and compare the destructive effects of temperature and chemical corrosion and the change of the resistivity of the rock mass. Help scientifically judge and accurately analyze the underground construction problems that may be encountered in future projects and the effective utilization of geothermal energy and provide a basis for the application of key technologies and methods.

Carbonized Leather Waste with Deposited Polypyrrole Nanotubes: Conductivity and Dye Adsorption.

This paper reports the conversion of a waste to a conducting material, exploiting the ability to adsorb pollutant organic dyes. Leather waste was carbonized at 800 °C in an inert nitrogen atmosphere. The resulting biochar was used for in-situ deposition of polypyrrole nanotubes produced by the oxidative polymerization of pyrrole in the presence of methyl orange. The composites of carbonized leather with deposited polypyrrole nanotubes of various composition were compared with similar composites based on globular polypyrrole. Their molecular structure was characterized by infrared and Raman spectra. Both conducting components formed a bicontinuous structure. The resistivity was newly determined by a four-point van der Pauw method and monitored as a function of pressure applied up to 10 MPa. The typical conductivity of composites was of the order of 0.1 to 1 S cm-1 and it was always higher for polypyrrole nanotubes than for globular polypyrrole. The method also allows for the assessment of mechanical features, such as powder fluffiness. The conductivity decreased by 1-2 orders of magnitude after treatment with ammonia but still maintained a level acceptable for applications operating under non-acidic conditions. The composites were tested for dye adsorption, specifically cationic methylene blue and anionic methyl orange, using UV-vis spectroscopy. The composites were designed for future use as functional adsorbents controlled by the electrical potential or organic electrode materials.

Effect of deposition temperature and hydrogen as a process gas on mechanical properties and specific electrical resistivity of thick a-C:H obtained by means of PACVD

DLC coatings are widely used for their protective properties such as high wear resistance, low friction coefficient as well as chemical inertness. However, their electrical resistance is usually very high, which limits their utilization in electrotechnical applications. To improve electrical conductivity, DLC films are typically doped with nitrogen or metals. This study, however, investigates the mechanical and electrical properties of un-doped, hydrogenated DLC films deposited using temperatures above 450 °C. To further enhance the coating's properties, hydrogen gas was added during deposition.The DLC coatings were produced by means of PA-CVD using a pulsed DC discharge. Temperatures of 450 °C, 500 °C and 550 °C were used to deposit a-C:H films on steel substrate. The process gas consisted of a mixture of argon and acetylene. Additionally, coatings were deposited with hydrogen added to the gas mixture. A silicon-based interlayer served as an electrical insulator between substrate and coating and was deposited with HMDSO as a precursor. To measure the specific electrical resistivity of the films, the van der Pauw method was performed. The mechanical properties of the coatings were determined through nanoindentation. Raman spectroscopy was performed to analyze the structure of the DLC coatings.The films showed a significant decrease in specific electrical resistivity with increasing deposition temperature. Values dropped to <104 μΩ cm at 550 °C, attaining levels close to graphite. Hardness and Young's modulus increased up to 147 % with rising deposition temperature. The addition of 18 % hydrogen gas during deposition resulted in at least 60 % further reduction in specific electrical resistivity, while also slightly raising coating hardness for deposition temperatures above 450 °C. With this new distinct deposition method, electrically conductive a-C:H coatings with improved mechanical properties can be produced only by increasing the deposition temperature and the utilization of hydrogen as process gas.

Comparison of the resistivities of nanostructured films made from silver, copper-silver and copper nanoparticle and nanowire suspensions

Spray deposition and inkjet printing of various nanostructures are emerging complementary methods for creating conductive coatings on different substrates. In comparison to established deposition techniques like vacuum metal coating and lithography-based metallization processes, spray deposition and inkjet printing benefit from significantly simplified equipment. However, there are number of challenges related to peculiar properties and behaviour of nanostructures that require additional studies. In present work, we investigate electroconductive properties and sintering behaviour of thin films produced from nanostructures of different metals (Ag, Cu and Cu-Ag) and different shapes (nanowires and spherical nanoparticles), and compare them to the reference Ag and Cu magnetron deposited films. Synthesized nanostructures were studied with transmission electron microscopy. Morphology and crystallinity of produced metal films were studied with scanning electron microscopy and X-ray diffraction. The electrical parameters were measured by the van der Pauw method. All nanowires-based films provided high conductivity and required only modest thermal treatment (200 °C). To achieve sufficient sintering and conductivity of nanoparticles-based films, higher temperatures are required (300 °C for Ag nanoparticles and 350 °C for Cu and Cu-Ag nanoparticles). Additionally, stability of nanowires was studied by annealing the samples in vacuum conditions inside a scanning electron microscope at 500 °C.

Oxygen plasma treatment of TeO2—B2O3 (boro-tellurite) thin films

In this study, boro-tellurite glasses with a composition of 75TeO2–25B2O3 (mol. %) (TB) were synthesized using a traditional melt-quenching method. The glasses were subsequently deposited as thin films using the thermionic vacuum arc system, and a subset of the samples underwent treatment with a low-pressure cold oxygen plasma system, resulting in the formation of the “TBO (boro-tellurite treated by oxygen plasma)” thin films. The structural and morphological properties of the TB and TBO thin films were characterized using x-ray diffraction analysis, x-ray photoelectron spectroscopy, Raman spectroscopy, field emission scanning electron microscopy, and atomic force microscopy. The optical properties of the thin film samples were evaluated using ultraviolet–visible spectrophotometry in the range of 300–800 nm. The resistivity of the thin films was measured using the four-probe Van der Pauw method. It was found that the TB thin films had an amorphous structure with some crystalline formations, whereas the TBO thin films were similar to the bulk boro-tellurite glasses described in the literature, with no detectable crystalline formations. Both TB and TBO thin films exhibited homogenous and amorphous surfaces. Furthermore, the electronic structure of the thin films has changed after oxygen plasma treatment.

Crack-Free High-Composition (&gt;35%) Thick-Barrier (&gt;30 nm) AlGaN/AlN/GaN High-Electron-Mobility Transistor on Sapphire with Low Sheet Resistance (&lt;250 Ω/□)

In this article, a high-composition (&gt;35%) thick-barrier (&gt;30 nm) AlGaN/AlN/GaN high-electron-mobility transistor (HEMT) structure grown on a sapphire substrate with ultra-low sheet resistivity (&lt;250 Ω/□) is reported. The optimization of growth conditions, such as reduced deposition rate, and the thickness optimization of different epitaxial layers allowed us to deposit a crack-free high-composition and thick AlGaN barrier layer HEMT structure. A significantly high two-dimensional electron gas (2DEG) density of 1.46 × 1013 cm−2 with a room-temperature mobility of 1710 cm2/V·s was obtained via Hall measurement using the Van der Pauw method. These state-of-the-art results show great potential for high-power Ga-polar HEMT design on sapphire substrates.

Enhanced photovoltaic performance of silicon-based solar cell through optimization of Ga-doped ZnO layer

In the present study, the impact of deposition pressure and substrate temperature of Ga-doped Zinc Oxide (GZO) thin film and the photovoltaic performance of this structure as a transparent conductive oxide (TCE) layer in silicon-based solar cell were investigated. Implementing a single target of GZO, the structural, optical, and electrical properties of 350 nm thick GZO thin films with various deposition pressure (5 mTorr, 10 mTorr, 15 mTorr and 20 mTorr) at room temperature (RT) and substrate temperature (RT, 150 °C, 200 °C, 250 °C) at 15 mTorr deposition pressure were fabricated using RF magnetron sputtering technique. The aim here was to find out the GZO films with the optimum pressure and substrate temperature to incorporate them into solar cell as a TCE layer. The X-ray diffraction (XRD) and atomic force microscopy (AFM) techniques were used to determine the structural properties of all samples. The optical transmission measurements were performed using spectroscopic Ellipsometer and the band gap values were calculated by Tauc plot using optical transmission data. In addition, the electrical characterization of the GZO samples were analyzed by the Van der Pauw method and Hall measurements. Finally, the most promising GZO thin film was determined based on the structural and optoelectrical characterization. The findings indicated that the XRD pattern of all the prepared films was dominated by (002) preferential orientation irrespective of the deposition pressure and substrate temperature. The AFM measurements showed that all the samples had a dense surface morphology regardless of the deposition pressures, but the surface morphology of the samples was clearly changed upon increasing substrate temperatures. The transmission values of the film did not significantly alter (∼82%) when the deposition pressures except for the substrate temperature of 200 °C (86%) were changed. The band gap values were calculated between 3.30 eV and 3.36 eV, which can be associated with enhancement of crystalline quality of the films. The lowest resistivity and the highest carrier concentration values belonged to the film fabricated at 15 mTorr@200 °C by 2.0 × 10−3 Ω.cm and 1.6 × 1020 cm−3, respectively. Both increasing the deposition pressure (up to 15 mTorr) and substrate temperature (up to 200 °C) contributes to improving the crystallite size, widening the optical band gap, lowering the resistivity, and increasing the carrier concentration. In order to evaluate and compare the effect of both deposition pressure and substrate temperature, Silicon-based solar cells were fabricated using the most promising layers (15 mTorr@RT, 15 mTorr@200 °C). The cell performance with the GZO thin film as a TCE layer showed that varying both the pressure and substrate temperature of the GZO film contributed to enhancing the solar cell parameters. Thus, the conversion efficiency increased from 9.24% to 12.6% with the sequential optimization of pressure and temperature. It can be concluded that the pressure applied during the deposition and substrate temperature had a significant impact on the properties of GZO thin films and its photovoltaic performance of solar cell used as TCE layer.

Investigating the Influence on the Electro-Conductive Properties of Leather as a Result of Natural Aging

Conductive leather and its use in smart products have found a lot of interest. Leather behaves as a good insulator, so it was treated with electrically conducting polypyrrole using a chemical polymerization technique to give it conductive characteristics. The electro-conductive properties are obtained by using the double in–situ oxidative polymerization of pyrrole. The electrical properties of conductive samples are studied using the Van Der Pauw method as a measuring method. The conductive leather transformation process was carried out during the 2018-2020 period, and the conductive leather samples were preserved in room conditions until the year 2023. The effect of natural ageing on the electro-conductive properties of conductive leather is the focus of this research. The results show that environmental factors influence polymer breakdown and stability, by causing an increase in electrical resistance. The changes in electrical surface resistance, as the effect of the ageing factor, vary from 39.8% to 129.9%. Those changes in electrical resistance indicate that ageing is one of the major concerns in the electrical properties and stability of conductive leather samples, so the performed measurements have importance in providing information for the researchers and designers regarding the conductivity changes over time as a result of natural ageing, which would like to work with conductive leather on smart products.