Four-probe Resistivity Measurements Research Articles

Structural, magnetic, and electrical properties of LaMnO3 doped with Na by microwave-assisted synthesis method

Abstract The electric and magnetic transport properties of La1-xNaxMnO3 (x = 0.15, 0.2, 0.25, 0.3) are studied using the X-ray diffraction (XRD), vibrating sample magnetometer (VSM), and four-probe resistivity measurement method. The samples are synthesized by the method of microwave heating. The obtained samples show phase changes around x = 0.25. The magnetization measurement shows the curie temperature (Tc) increases as the level of doping increases and saturates around x = 0.25. The resistivity measurement dramatically decreases at a metal-insulator transition temperature close to Tc. These findings are discussed along with the structural features of different Na concentrations.

Failure Analysis and Piezo-resistance Response of Intralaminar Glass/Carbon Hybrid Composites Under Blast Loading Conditions

Abstract In this study, damage mechanisms and the piezo-resistance response of glass/carbon intralaminar hybrid composites are examined under blast loading conditions. Two-ply orientations are considered, namely a repeating ((G45C45)R) and an alternating ((G45C45)A) +/− 45° glass/carbon layers, along with three boundary condition configurations: simply supported, partially fixed, and fully fixed are applied. A shock tube apparatus and the three-dimensional digital image correlation technique are utilized to investigate the interaction of shock waves with the composites and gather a comprehensive deformation field during the loading. A modified four-probe resistivity measurement method is implemented to comprehend the piezo-resistance response associated with damage evolution. The results underscore the substantial influence of boundary conditions on the blast mitigation capacity of the composites. Analysis following the experiments reveals that the damage to the specimens primarily involves the fracture of fibers accompanied by internal delamination. Thermal imaging of the tested composite specimens provides enhanced insight into the precise occurrences of internal fiber breakage and delamination. Composites of (G45C45)A type demonstrate an increased energy dissipation ranging from 18% to 33% compared to (G45C45)R composites, depending on the specific boundary conditions among the three types considered. Furthermore, the findings indicated a strong correlation between changes in piezo-resistance and the fracture of carbon fibers, coupled with the sustained deformation of the composites. Notably, (G45C45)A composites exhibited 100% ∼ 300% higher change in piezo-resistance compared to (G45C45)R composites, indicative of the superior damage-sensing capabilities of the former.

Effect of internal moisture on the electric conductivity of cement composites with expanded graphite determined by impedance spectroscopy

The paper presents the results of a study of the effect of internal moisture on the electrical conductivity of cement composites with expanded graphite. Cement pastes with different content of expanded graphite were prepared for measurement. The electrical conductivity was determined by using impedance spectroscopy at different degrees of water saturation. The results of the impedance spectroscopy were presented in Nyquist plots. On the basis of the obtained Nyquist plots, electrical equivalent circuits were fitted for different water saturation. Capacitance and resistance were calculated from the fitted equivalent circuits. Additionally, DC four-probe resistance measurements were carried out. The results showed that internal moisture affects the electrical conductivity of composites not only for a low amount of expanded graphite but also for the content in the percolation zone. For composites with expanded graphite with percolation zone (4 and 5 wt%), the dominant conduction mechanism changed from electron to ionic with moisture content. This change is observed as a change in the nature of the Nyquist plot from a vertical line to a semicircle. Internal moisture does not affect the conductivity of cement composites with expanded graphite higher than the percolation threshold.

Full lifetime demonstration of a Micro-Cathode-Arc thruster evolution characteristics

Ground lifetime test is the most crucial experiment to assess the performance, reliability, and flight qualification of electric propulsion, and it can bring new insights for understanding the operation characteristics. This work demonstrates a full lifetime test of 140000 cycles on a Micro-Cathode-Arc Thruster (μCAT) with 160 μs charging time and 86 mJ charging energy. A four-probe resistivity measurement method is utilized to investigate variations in the conductive film thickness and resistivity throughout the thruster lifespan. Direct film parameters show that the lifetime of the μCAT can be divided into three stages. In the initial stage, the film thickness decreases by 1.2 μm and the resistivity increases significantly due to the high discharge intensity and intense film ablation; In the steady stage, the change of the film thickness is within 5%, and the resistivity of the film increases slowly from 0.050 Ω·mm to 0.223 Ω·mm. In the end stage, the resistivity exponentially increases from 0.223 Ω·mm to 1.176 Ω·mm, with the increase accounting for 81%, ultimately resulting in the failure of the thruster open circuit. Additionally, the evolution of discharge parameters, and the variation of plume parameters are measured throughout the lifetime. The discharge characteristics also show significant differences in the duration of voltage and current in these three stages. The results of plume shape and plasma parameters are also well consistent with the discharge parameters and film state. These results suggest that, for evaluating the steady stage lifetime of thrusters, the film thickness is the best indicator compared to the variations in resistivity and voltage-current characteristics. For the end stage, the plasma plume morphology, discharge duration, and plume parameters can conveniently and clearly characterize the thruster failures and irregularity.

Comparison between Four-Probe and Two-Probe Electrical Resistivity Measurement to Monitor the Curing and Piezoresistivity Behavior of Smart Cement Paste Modified with Waste Steel Slag and Green Nano-magnetite

Abstract This study aims to examine the compressive strength, electrical resistivity, and piezoresistivity characteristics of ordinary Portland cement (OPC) with a constant water-to-cement ratio (w/c) of 0.38. The optimal value of steel slag (SS) was determined to be 5 % based on the compressive strength of six different mixes of cement paste modified with various SS from 0 % to 30 % weight of cement. Additionally, the investigation will include modified cement samples containing 1 % green synthesized material and commercially available nano-magnetite (NM). Because iron is the primary component of SS and NM, the electrical resistivity, which is the primary criterion for structural health monitoring of cementitious material, can be increased by adding SS and NM. Hence, a comparative analysis was conducted to assess the resistivity of cement paste throughout the early curing period up to 28 days using an alternative current (AC) and embedding wires into the specimen, employing both the two-probe (2P) and four-probe (4P) methodologies. The findings suggest that the 4P method is a more precise approach for determining electrical resistivity than the 2P method, as the wire probe is not considered in the 4P method. Hence, it is imperative to compute the correlation between the 2P and 4P methodologies in order to attain a precise resistivity measurement. The suggested model indicates that the expected 4P resistivity can be measured with high precision, a high coefficient of determination (R2) of .97, and a low root mean square error (RMSE) of 7.33 Ω·m, based on the 2P result. The piezoresistivity results demonstrated that the cement paste modified with green synthesis nano-magnetite (GSNM) had a higher electrical resistivity (ER) change, 10.85 % greater than cement paste only, 57 % higher than cement modified with SS, and 34.2 % higher than cement paste modified with commercial nano-magnetite (CNM) after 28 days of curing. In addition, the compressive strength of cement paste modified with GSNM was higher than that of cement paste, cement paste modified with SS, and cement paste modified with CNM by 15.96 %, 21 %, and 1.7 %, respectively, after 28 days of curing. A Vipulanandan p–q model was used to forecast the electrical resistivity of cement paste versus time at start hydration during 28 days of curing and the change of electrical resistivity versus compressive strength at 3, 7, and 28 days. The Vipulananda p–q model anticipated both electrical resistivity and piezoresistivity behavior well.

Origin of the near-room temperature resistance transition in lutetium with H2/N2 gas mixture under high pressure.

The recent report of room-temperature superconductivity at near-ambient pressure in nitrogen-doped lutetium hydride (Lu-H-N) by Dasenbrock-Gammon etal. [Nature 615, 244-250 (2023)] has attracted tremendous attention due to its anticipated great impact on technology. However, the results could not be independently reproduced by other groups worldwide in follow-up studies, which elicited intense controversy. Here, we develop a reliable experimental protocol to minimize the extensively concerned extrinsic influences on the sample by starting the reaction from pure lutetium loaded with an H2/N2 gas mixture in a diamond anvil cell under different pressures and temperatures and simultaneously monitoring the entire chemical reaction process using in situ four-probe resistance measurements. Therefore, we could repeatedly reproduce the near-room temperature upsurge of electrical resistance at a relatively early stage of the chemical reaction. However, the mechanism is suggested to be a metal-to-semiconductor/insulator transition associated with the structural modulation in the non-stoichiometric Lu-H-N, rather than superconductivity.

Properties of superconducting MgB2 spherical shells deposited on 2 mm and 1 mm diameter Si3N4 spheres

Superconducting spherical shells may not only provide an appealing platform for exploring superconductivity in three-dimensional (3D) geometries with curved surfaces, but also be practically applied in important fields, such as in gyroscopes and gravimeters. In inertial confinement fusion (ICF), the perturbation on the target capsule caused by traditional contact support methods is recognized as one of the major contributors to performance degradation in ICF implosions. It was proposed recently that coating the capsule with a thin superconducting MgB2 spherical shell to realize non-contact support by means of magnetic levitation at the required temperatures K might offer a promising solution to this longstanding problem. To simulate the coating of ICF capsules, we deposited MgB2 spherical shells onto polycrystalline Si3N4 spheres (diameter d = 2 mm and 1 mm) via a hybrid physical–chemical vapour deposition technique. For both diameters, the spherical shells, of about 1 µm in thickness and covering the whole spheres completely, were polycrystalline with thin plate-shaped MgB2 crystallites oriented randomly and closely connected. The spherical shells exhibited superconducting transition at a zero resistance temperature of 38.5–39.4 K in four-probe resistance measurements and ideal diamagnetism at low temperatures in magnetization measurements, suggesting the good crystallinity and homogeneity of the shells. The upper critical field , the irreversibility field and the lower critical field were characterized and showed similar magnitudes and temperature dependencies for the d = 2 mm and 1 mm shells, yielding of 7–8 T and of 7–12 mT at 20 K. The superconducting critical current density values, evaluated from the magnetization hysteresis loops, were A cm−2 and A cm−2 at 20 K under zero and 2 T applied field, respectively, for the d = 1 mm shell. The occurrence of small flux jumps was observed at low temperatures up to 12 K and in low fields below 0.3 T. The results demonstrate the feasibility of fabricating MgB2 spherical shells with properties applicable to potential areas employing magnetic levitation such as in ICF and that MgB2 spherical shells may be exploited as an experimental system to study superconductivity in 3D curvilinear geometry.

Ru thin films prepared by RF magnetron sputtering with Ru targets of different microstructures

Ruthenium (Ru) exhibits excellent electrical properties at the nanoscale, and it can be used to replace Al and Cu as interconnect metals for nodes of 20 nm and below in the next generation of integrated circuits. Ru interconnects mainly exist in the form of films, and Ru targets are used as the key raw materials to produce these films. Establishing whether there is an inheritance relationship in terms of microstructure and electrical properties between these targets and the resultant films will determine whether these are important factors for improving the electrical properties of Ru films and will provide directional guidance for the preparation of Ru targets. In this work, Ru targets were prepared by vacuum hot pressing with two different Ru powders with different morphologies and particle sizes. Ru films were then deposited on SiO2/Si(100) substrates by RF magnetron sputtering at substrate temperatures ranging from room temperature (RT, about 25 °C) to 400 °C. The microstructures and electrical properties of the Ru targets and Ru films were investigated by high-resolution field-emission scanning electron microscopy, x ray diffraction, atomic force microscopy, four-probe resistivity measurements, and digital conductivity tests. The results showed that Ru targets with a more uniform microstructure had lower resistivity; furthermore, Ru films deposited by Ru targets with a more uniform microstructure were preferentially crystallized, and they also had a faster average deposition rate, a smaller average grain size, and lower surface roughness. However, no correlation was found between the crystal orientations of the Ru films and Ru targets.

Role of Hydrogen in Ethylene-Based Synthesis of Single-Walled Carbon Nanotubes.

We examined the effect of hydrogen on the growth of single-walled carbon nanotubes in the aerosol (a specific case of the floating catalyst) chemical vapor deposition process using ethylene as a carbon source and ferrocene as a precursor for a Fe-based catalyst. With a comprehensive set of physical methods (UV-vis-NIR and Raman spectroscopies, transmission electron microscopy, scanning electron microscopy, differential mobility analysis, and four-probe sheet resistance measurements), we showed hydrogen to inhibit ethylene pyrolysis extending the window of synthesis parameters. Moreover, the detailed study at different temperatures allowed us to distinguish three different regimes for the hydrogen effect: pyrolysis suppression at low concentrations (I) followed by surface cleaning/activation promotion (II), and surface blockage/nanotube etching (III) at the highest concentrations. We believe that such a detailed study will help to reveal the complex role of hydrogen and contribute toward the synthesis of single-walled carbon nanotubes with detailed characteristics.

Enhanced Magnetism and Anomalous Hall Transport through Two-Dimensional Tungsten Disulfide Interfaces.

The magnetic proximity effect (MPE) has recently been explored to manipulate interfacial properties of two-dimensional (2D) transition metal dichalcogenide (TMD)/ferromagnet heterostructures for use in spintronics and valleytronics. However, a full understanding of the MPE and its temperature and magnetic field evolution in these systems is lacking. In this study, the MPE has been probed in Pt/WS2/BPIO (biphase iron oxide, Fe3O4 and α-Fe2O3) heterostructures through a comprehensive investigation of their magnetic and transport properties using magnetometry, four-probe resistivity, and anomalous Hall effect (AHE) measurements. Density functional theory (DFT) calculations are performed to complement the experimental findings. We found that the presence of monolayer WS2 flakes reduces the magnetization of BPIO and hence the total magnetization of Pt/WS2/BPIO at T > ~120 K-the Verwey transition temperature of Fe3O4 (TV). However, an enhanced magnetization is achieved at T < TV. In the latter case, a comparative analysis of the transport properties of Pt/WS2/BPIO and Pt/BPIO from AHE measurements reveals ferromagnetic coupling at the WS2/BPIO interface. Our study forms the foundation for understanding MPE-mediated interfacial properties and paves a new pathway for designing 2D TMD/magnet heterostructures for applications in spintronics, opto-spincaloritronics, and valleytronics.

Effect of substrate temperature on the optical properties of DC magnetron sputtered copper oxide thin films

Copper oxide thin films are deposited on quartz substrates by DC magnetron sputtering and the effect of deposition temperature on the optical properties is examined in detail. Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) analysis, Raman spectroscopy, UV–vis spectroscopy, and four-probe sheet resistance measurements are used to characterize the surface morphology, structural, optical, and electrical properties of the deposited films respectively. Sputter deposition is carried out with the substrate at room temperature and at elevated temperatures between 200 and 300 °C. XRD analysis indicates that the oxide formed is primarily Cu2O and the absorption spectra show a critical absorption edge at around 300 nm. The sheet resistance gradually decreases with increase in deposition temperature, corresponding to an increase in the conductivity of the films. Also observed is an increase in the band gap energy from 2.02 eV for room temperature deposition to 2.35 eV at 300 °C, corresponding to an improved film crystallinity and reduction in defect density. The band gap energy and the variation of sheet resistance with substrate temperature shows that the microstructure plays a vital role in their behavior. These transformation characteristics are of huge technological importance having variety of applications including transparent solar cell fabrication.

Possible unconventional order parameter in single crystals of SrPt3P superconductor

Anisotropic properties of single crystals of SrPt3P were studied using London penetration depth and electrical resistivity measurements. The upper critical field, , was determined from four-probe electrical resistivity measurements for three orthogonal directions of a magnetic field with respect to the crystal. The London penetration depth, , was determined from the magnetic susceptibility of the Meissner–London state measured using a tunnel-diode resonator technique. Whereas and the normal-state are practically identical for all three magnetic field orientations, the London penetration depth shows significant unidirectional anisotropy. The low-temperature is exponentially attenuated when a small excitation radiofrequency magnetic field, H rf , is applied along the -direction, in which case screening currents flow in the -plane, while for the other two orientations, and , the London penetration depth shows a much stronger, , variation. Such unusual and contrasting behavior of the two anisotropies, and , imposes significant constraints on the possible order parameter. Although our measurements are insufficient to derive conclusively the superconducting gap anisotropy, the order parameter with two point nodes and a modulation in the perpendicular direction is qualitatively consistent with the experimental observations.

Electrical resistance and capacitance responses of smart ultra-high performance concrete with compressive strain by DC and AC measurements

Electrical properties and strain self-sensing ability of smart ultra-high performance concrete (UHPC) containing different steel fiber concentrations were characterized using DC resistivity, AC resistivity, and capacitance measurements. Four-probe DC resistance measurement and four-probe/ two-probe AC impedance measurement were performed in this study. The resistivity measured by the two-probe AC method is lower than that measured by the four-probe DC method. The magnitude of impedance measured by the four-probe method is close to that measured by the two-probe method. The capacitance of UHPC increases with an increase in fiber dosages, which is mainly related to the interfacial polarization, including the polarization of solid–liquid electrical double layer and fiber/matrix/fiber interfacial polarization. The addition of steel fibers can effectively improve the sensitivity of AC resistance and capacitance variation with strain, but it has less effect on the sensitivity of DC resistance variation with strain, which is due to different strain self-sensing mechanisms. Thus, the sensitivity represented by AC resistance and capacitance is higher than that represented by DC resistance. UHPC with the steel fiber content of 1.5% exhibits high sensitivity and good linear relationship between the fractional change in AC electrical parameters and strain. The results indicate that AC resistance measurement is preferable to be adopted for strain self-sensing using smart UHPC.

Semiconductor-to-metal transition in nanocomposites of wide bandgap oxide semiconductors

The semiconductor-to-metal transition (SMT) is reported in nanocomposite films of wide bandgap semiconducting oxides. This study offers insight into the existing models of temperature-dependent charge transport by tailoring the defects induced disorder into the lattice by swift heavy ions irradiation. The structural studies show the presence of both cadmium oxide and zinc oxides phases and confirm the nanocomposite nature of films. Temperature-dependent charge transport properties of the nanocomposite films were studied by carrying out four-probe resistivity measurements in the wide temperature range of 35–300 K. Here, the swift heavy ions irradiated films demonstrated the tuning of SMT phenomena and its transition temperature upon increasing fluence of irradiation. These irradiation effects are discussed in terms of irradiation-induced defects/disorders into the lattice. The change in the nature of temperature-dependent resistivity in pristine and irradiated films has been envisaged with a quantitative fit of experimental data by invoking quantum correction to conductivity (QCC). Our results are consistent with QCC model, which essentially depends on weak localization and renormalized electron-electron interactions. Thus, this work extends the validity of the weak localization model to composite systems.

Effect of synthesis conditions and composition on structural and phase states and electrical properties of nanogranular (FeCoZr)x (PZT)100-x films (30 ≤ x ≤ 85 at.%)

Granular films containing Fe50Co50Zr10 alloy nanoparticles inside Pb0,81Sr0,04(Na0,5Bi0,5)0,15(Zr0,575Ti0,425)O3 (PZT) ferroelectric matrix possess a combination of functional magnetic and electrical properties which can be efficiently controlled by means of external electric or magnetic fields. The formation of the required granular structure in PZT matrix is only possible if synthesis is carried out in an oxygen-containing atmosphere leading to substantial oxidation of metallic nanoparticles. Thus an important task is to study the oxidation degree of metallic nanoparticles depending on synthesis conditions and the effect of forming phases on the electrical properties of the films. The relationship between the structural and phase state and electrical properties of granular FeCoZr)x (PZT)100-x films (30 ≤ x ≤ 85 at.%) synthesized in an oxygen-containing atmosphere at the oxygen pressure PO in a range of (2.4–5.0) · 10–3 Pa has been studied using X-ray diffraction, EXAFS and four-probe electrical resistivity measurement. Integrated comparative analysis of the structural and phase composition and local atomic order in (FeCoZr)x (PZT)100-x films has for the first time shown the fundamental role of oxygen pressure PO during synthesis on nanoparticle oxidation and phase composition. We show that the oxygen pressure being within PO = 3.2 · 10–3 Pa an increase in x leads to a transition from nanoparticles of Fe(Co,Zr)O complex oxides to a superposition of complex oxides and a-FeCo(Zr,O) ferromagnetic nanoparticles (or their agglomerations). At higher oxygen pressures РО = 5.0 · 10–3 Pa the nanoparticles undergo complete oxidation with the formation of the (FexCo1-x)1-δO complex oxide having a Wurtzite structure. The forming structural and phase composition allows one to explain the observed temperature dependences of the electrical resistivity of granular films. These dependences are distinguished by a negative temperature coefficient of electrical resistivity over the whole range of film compositions at a high oxygen pressure (РО = 5.0 · 10–3 Pa) and a transition to a positive temperature coefficient of electrical resistivity at a lower oxygen pressure (РО = 3.2 · 10–3 Pa) in the synthesis atmosphere and x &amp;gt; 69 at.% in the films. The transition from a negative to a positive temperature coefficient of electrical resistivity which suggests the presence of a metallic contribution to the conductivity is in full agreement with the X-ray diffraction and EXAFS data indicating the persistence of unoxidized a-FeCo(Zr,O) ferromagnetic nanoparticles or their agglomerations.

Study of Carrier Transfer Mechanism When Substituting Strontium at Barium Sites in CuTl-1223 Superconducting Phase

Strontium-doped CuTl-1223 phase has been obtained by employing a nonstoichiometric composition of the form Tl1/2Cu1/2(Ba1−xSrx)Ca1Cu4Oy (x = 0, 0.1, 0.2, 0.3). The superconducting properties of the samples were investigated by x-ray diffraction analysis and four-probe resistivity, alternating-current (AC) susceptibility, and Fourier-transform infrared (FTIR) absorption measurements. The effect of doping strontium atoms on the intrinsic superconductor parameters of these samples was studied by excess conductivity analysis. All the samples showed orthorhombic crystal structure in space group Pmmm, and the cell parameters were determined by using all the planar reflections. The c-axis length and the unit cell volume decreased with Sr doping in the final compound. Suppression of the room-temperature resistivity followed by metallic variations in resistivity versus temperature measurements are typical features for these samples. The zero-resistivity critical temperature and the onset of diamagnetism were suppressed with increasing Sr doping in the final compound. The apical oxygen phonon mode of type Cu(1)–OA–Cu(2) observed at around 548 cm−1 hardened with increasing Sr doping. The excess conductivity analysis revealed that the coherence length along the c-axis, the interlayer coupling, and the Fermi velocity of the carriers increased for the Sr doping levels of x = 0.1 and 0.2 but decreased for the sample with x = 0.3. The values of Bc0(T), Bc1(T), and Jc0(0) increased with increasing Sr doping in the final compound. It is proposed that this effect arises due to an increase in the superconducting volume fraction. A decrease in the value of the London penetration depth λp.d. and the Ginzburg–Landau (GL) parameter shows that the flux-pinning characteristics of the samples were improved by Sr doping. An increase in the mean free time of the carriers and a decrease in the energy required to break apart Cooper pairs result from a decrease in the remanent field scattering induced by the increased population of pinning centers in Sr-doped samples.

New Cage-Like Cerium Trihydride Stabilized at Ambient Conditions

New Cage-Like Cerium Trihydride Stabilized at Ambient Conditions

Calibration of Manganin pressure gauge for diamond-anvil cells

Pressure calibration for most diamond-anvil cell (DAC) experiments is mainly based on the ruby scale, which is key to implementing this powerful tool for high-pressure study. However, the ruby scale can often hardly be used for programmably controlled DAC devices, especially the piezoelectric-driving cells, where a continuous pressure calibration is required. In this work, we present an effective pressure gauge for DACs made of Manganin metal based on the four-probe resistivity measurements. Pressure dependence of its resistivity is well established and shows excellent linear relations in the 0-30GPa pressure range with a slope of 23.4 (9) GPa for the first-cycle compression, in contrast to that of multiple-cycle compression and decompression having a nearly identical slope of 33.7 (4) GPa likely due to the strain effect. In addition, the such-established Manganin scale can be used for continuously monitoring the cell pressure of piezoelectric-driving DACs, and the reliability of this method is also verified by the fixed-point method with a Bi pressure standard. Realization of continuous pressure calibration for programmably controlled DACs would offer many opportunities for the study of dynamics, kinetics, and critical behaviors of pressure-induced phase transitions.

Automated low-temperature resistivity measurement setup: Design and fabrication

In this paper we present, the design and working of the automated low-temperature four-probe DC electrical resistivity measurement setup developed in-house. This setup measures the resistance/resistivity in the temperature range 300 K to 80 K. The overall arrangement comprises a low-temperature four-probe sample holder, Lakeshore 335 Temperature controller, Keithley Delta mode 6221 AC/DC source, 2182A Nano-voltmeter, and a vacuum system. For the measurement of sample temperature Pt-100 sensor is employed. The IEEE-488.2 card and GPIB cables link the mentioned instruments to the computer. The licenced Lab-VIEW 2018 software is employed to build the control programme. The established setup can measure the resistance of both bulk and thin-film samples, making it versatile. A test measurement on well-characterized ceramic Pr0.67Sr0.33MnO3 perovskite oxide synthesized using a solid-state route has been carried out in the newly installed setup. The data acquired from the installed setup and beforehand resistance measurement carried out in-house low-temperature resistance measurement setup at UGC-DAE-Consortium for scientific research, Indore conceded a precision for both temperature and resistance.

Macroscopic yarns of FeCl3-intercalated collapsed carbon nanotubes with high doping and stability

Macroscopic arrays of highly-crystalline nanocarbons offer the possibility of modifying the electronic structure of their low dimensional constituents, for example through doping, and studying the resulting collective bulk behaviour. Insertion of electron donors or acceptors between graphitic layers is an attractive method to reversibly increase charge carrier concentration without disruption of the sp2-conjugated system. This work demonstrates FeCl3 intercalation into fibres made up of collapsed (flattened) carbon nanotubes. The bundles of collapsed CNTs, similar to crystallites of graphitic nanoribbons, host elongated layered FeCl3 crystals of hundreds of nm long, much longer than previous reports on graphitic materials and directly observable by transmission electron microscopy and X-ray diffraction. Intercalated CNT fibres remain stable after months of exposure to ambient conditions, partly due to the spontaneous formation of passivating monolayers of FeClO at the crystal edge, preventing both desorption of intercalant and further hydrolysis. Raman spectroscopy shows substantial electron transfer from the CNTs to FeCl3, a well-known acceptor, as observed by G band upshifts as large as 25 cm−1. After resolving Raman features for the inner and outer layers of the collapsed CNTs, strain and dynamic effect contributions of charge transfer to the Raman upshift could be decoupled, giving a Fermi level downshift of −0.72 eV and a large average free carrier concentration of 5.3·1013 cm−2 (0.014 electrons per carbon atom) in the intercalated system. Four-probe resistivity measurements show an increase in conductivity by a factor of six upon intercalation.