Variation Of Resistivity Research Articles

The Utilization of Pearson’s Method to Analyze Piezoresistive Effect in Self-Sensing Cement Composite with Graphite

Structural health monitoring (SHM) techniques aim to detect and prevent failures in constructions, although their use may require many sensors, which makes this technique expensive and laborious. In this sense, the use of self-sensing cementitious composites based on the piezoresistivity effect could be a solution to some monitoring problems. Thus, the evaluation of the piezoresistive effect is commonly performed by analyzing the linearity between mechanical forces and the variation of electrical resistivity, through the coefficient of determination (R2). However, this work has been used to perform the analysis through Pearson's correlation in samples of self-sensing cementitious composites with graphite addition. The results obtained have shown that Pearson's correlation has the potential to be used for the evaluation of the correlation between electrical resistivity and mechanical forces to verify the piezoresistive effect in the cases studied.

Experimental and modeling of electrical resistivity changes due to micro-spatial distribution of fluid for unconsolidated sand

Electrical resistivity measurements of reservoir rocks are usually applied to identify fluid type and saturation. Although it has been widely studied, the effect of fluid saturation on electrical resistivity is not yet fully understood, especially when considering the spatial distribution of fluids. Hysteresis and electrical resistivity jump in the imbibition process are two of the phenomena that remain unclear. Microscopical evaluation would be useful in understanding these phenomena. In this paper, we analyzed the influence of the micro-spatial distribution of fluids on electrical resistivity. In order to achieve the objective, laboratory measurements and computer modeling of electrical resistivity were carried out. Measurements were made on unconsolidated sand samples that were saturated with brine. Two categories of samples were prepared based on the position of the brine injection to obtain fluid spatial distribution variations in rock pores. Measurement results showed that the electrical resistivity varies depending on the brine injection position. Subsequently, 3-D microcomputed tomography images were acquired to analyze sample microstructure and model fluid spatial distribution. We implemented three different saturation models made up of varying fluid filling mechanisms onto digital images of samples, then used them to compute the electrical resistivity of the sub-sample using the finite element method. The measurement and calculation of electrical resistivity showed good agreement. These results indicate that the proposed model is capable of representing spatial fluid distribution in pore spaces of measured samples. This fluid distribution is most responsible for the variation of the electrical resistivity in the samples. Furthermore, the electrical resistivity jump phenomenon in the imbibition process was successfully explained through the proposed model. Based on this study's results, it can be concluded that the spatial distribution of fluids needs to be considered in the estimation of electrical resistivity. The research findings provide insight into how micro-spatial distribution affects electrical properties of rocks of importance to the interpretation of electrical resistivity data.

Improved Resistive Switching Observed in Ti/Zr3N2/p-Si Capacitor via Hydrogen Passivation

Charge-trap based resistive switching (RS) has attracted attention in the resistive random-access memory (RRAM) industry due to its gradual RS behavior for multi-level and synaptic applications. In this work, in order to lower the operating current level closely related to device&#x2019;s degradation, we applied a hydrogen passivation to Zr₃N₂ based RRAM devices and investigated the correlation between current level and trap density, such as an interface trap density (<inline-formula> <tex-math notation="LaTeX">$\text{N}_{\mathrm {it}}$ </tex-math></inline-formula>) at the Zr<inline-formula> <tex-math notation="LaTeX">$_{3}\text{N}_{2}/p$ </tex-math></inline-formula>-Si layer and nitride trap density (<inline-formula> <tex-math notation="LaTeX">$\text{N}_{\mathrm {nt}}$ </tex-math></inline-formula>) within Zr₃N₂ films, for memory cells annealed in conventional N₂ gas as well as H₂ gas. Compared to the N₂-annealed sample, after H₂ annealing, <inline-formula> <tex-math notation="LaTeX">$\text{N}_{\mathrm {it}}$ </tex-math></inline-formula> is lowered by the hydrogen passivation effect, which results in a reduction of both current level at high resistive state (HRS) and variation of HRS and low resistive state (LRS). As a result, in the H₂ annealed Zr₃N₂ RRAM cell, we observed a lower operation voltage/current, longer endurance, and larger read margin due to the hydrogen passivation effect.

Mapping the spatial variability of subsurface resistivity by using vertical electrical sounding data and geostatistical analysis at Borena Area, Ethiopia

Vertical electrical sounding survey has been done to map and visualize resistivity distribution at Borena basin. The area is situated in Southern Main Ethiopian Rift, where Rirriba rift, Mega rift and associated fractures define the structural setting of the area. It is covered by Quaternary deposits, Quaternary and Tertiary basaltic rocks and Precambrian metamorphic rocks. Bullal basaltic formation outstretch in the Rirriba rift and it is thought to be potential groundwater aquifer. About 288 Vertical Electrical Sounding data were collected. Inflection and extreme points were used to identify characteristic points. Variograms are modeled and kriging interpolation is used to map distribution of resistivity, determined from characteristic points, in the area. Very low to low resistivity variations are mapped in northern end of the study area, whereas medium to moderately resistive ground are mapped in the middle and southern part of the area. The low resistivity horizon at the shallow subsurface could be due to salinity since the area occupy numerous saline craters and maars. Approximate mapping of large sets of Vertical Electrical Sounding data with geostatistical treatment has facilitated the interpretation and provided a sound picture of the subsurface.• Inflection and extreme points were extracted from smothed VES curves to identify characteristic points.• Variograms are modeled and kriging interpolation is used to map 3D distribution of resistivity data.

Magnetotransport and magnetocaloric effect in Gd3In

The electrical transport and magnetic properties of the rare-earth based binary intermetallic compound Gd3In are reported here. The sample has orthorhombic crystal structure with space group Pnma. At TC = 190 K, the sample orders ferromagnetically, however, a reentrant antiferromagnetic-like state is observed below TN = 100 K where a sharp drop in magnetization is noticed. Clear signature of meta-magnetic transition is present in the isothermal variation of magnetization for an applied field of HC = 11.5 kOe at 2 K. Due to the presence of field induced transition, we have calculated the magnetocaloric effect (MCE) around the magnetic transitions using our magnetization data, which turns out to be quite eventful. MCE, expressed in terms of change in entropy (ΔS) due to the change in magnetic field (H), is found to be negative around TC with a maximum value of ΔS = −5.3 J kg−1 K−1 for H = 50 kOe. On the other hand, it is positive up to H = 10 kOe around TN, and turns negative for higher values of H with a maximum value of ΔS = −2.6 J kg−1 K−1 for 50 kOe applied magnetic field. This is clearly due to the metamagnetic transition observed around 11.5 kOe. In the temperature variation of electrical resistivity, we observe clear signatures of magnetic transitions occurring at TC and TN, and the sample shows negative magnetoresistance throughout the temperature range (6–300 K) with a value of −12% at around 6 K for H = 50 kOe.

Estimation of the Pb Content in a Tailings Dam Using a Linear Regression Model Based on the Chargeability and Resistivity Values of the Wastes (La Carolina Mining District, Spain)

The study area is located in the old mining district of Linares–La Carolina (southeastern Spain), the largest global producer of lead between 1875 and 1920. The selected environmental liability is the dam of the Federico mine and the waste that was generated during the flotation process. Geophysical techniques were applied along the slope of the dam, specifically ERT and IP. In total, 26 waste samples were taken along the entire slope of the dam, in which a high metal(oid) content was identified, sometimes much higher than the reference levels established by European and regional legislation for contaminated soils. The concentrations of Pb, As, and Ba stood out, with mean values of 4863 mg·kg−1, 89 mg·kg−1, and 794 mg·kg−1, respectively. Univariate and multivariate statistical analysis could characterize the distribution of the contents of the different elements along the slope, defining the associations and dispersion patterns of the metal(oid)s in the interior structure of the mine wastes. With the results of the Pb content (the most abundant metal in mineral paragenesis), a mathematical model was obtained by linear regression that related the variability of this cation with the variation in electrical resistivity and chargeability obtained by geophysical techniques.

Shallow and deep submarine groundwater discharge to a tropical sea: Implications to coastal hydrodynamics and aquifer vulnerability

The groundwater of the coastal aquifers, the primary source of drinking water for the community around it, is under stress due to changing climatic conditions, extreme climate events, over-exploitation, and natural/anthropogenic interferences. To sustain coastal groundwater, it is essential to understand the hydrogeological control on the distribution of salinity and submarine groundwater discharge (SGD) in various spatial and temporal scales at different depths. This study is focused to delineate the SGD and salinity distribution for shallow surficial and deep aquifers by application of the hydrogeochemical and geophysical approach in an intertidal zone. The resistivity [Electrical Resistivity Tomography (ERT), Vertical Electrical Sounding (VES)] and Ground Penetrating Radar (GPR) data show surficial aquifers have (up to 1.5 m below ground level (m bgl)) have higher freshwater discharge at the post-monsoon season and recirculation of infiltrated brackish water with increasing offshore distances. The re-circulated seawater in distant offshore was also predominant for intermediate (>1.5 up to 100 m bgl) (brackish water-saturated) and deeper depths (>100 m bgl) (fresh groundwater), which is observed from the distinct resistivity contrasts from VES. The interaction process for all the depths with seawater has been induced by the coastal hydrodynamics, meteoric recharge, and fluctuation of groundwater levels. However, variations of resistivity and sounding data delineate that the groundwater resources underneath the shallow depth brackish water are physically vertically disconnected from the surficial aquifer, but spatial variation in sounding data shows the hydraulic connectivity, which would lead to a serious concern for fresh groundwater resources, where density-dependent transportation of solute is plausible, both vertically and horizontally.

Tracking and modelling water percolation process in modern intensive farming loess terraces

Loess slopes along the Yellow River in China are prone to failure in response to intensive irrigation. Existing studies found that the wetting front depth subjected to intensive farming water could barely reach 6 m in loess terrace. Long-term field monitoring revealed that irrigation water takes a short time to recharge the groundwater. Yet the dynamic process and mechanism of irrigation water percolation through thick unsaturated loess remains unrevealed. To address this problem, the Heifangtai terrace was selected as the study area and a series of unique full-scale controlled field irrigation experiments were carried out combined with numerical modelling. The variations in water content, pore-water pressure, and electrical resistivity over time were monitored. From the field testing, the unsaturated stratified loess layer could be divided into two vadose zones based on the water percolation characteristics, namely, transient flow zone (0–6.5 m) and steady flow zone (>6.5 m). Variation in water content presented a hysteresis effect in the transient flow zone compared with the steady flow zone. In the whole seepage process, the vertical percolation rate of 0.5 m/day was double that of the horizontal percolation rate. Furthermore, the irrigation water percolating process was modelled using a finite element code, PANDAS, which was validated by the field testing. Numerical simulation results demonstrated that the movement of wetting front was hampered by the air outflow within transient flow zone and that irrigation water reached the deep groundwater table through the thick unsaturated stratified loess within 100 days, which was consistent with the field monitoring data. This research aids in a better understanding of the irrigation water percolation process in unsaturated stratified loess in the loess region.

Charge transport mechanisms in monovalent doped mixed valent manganites

In this communication, we report the results of the studies on structural and transport properties of monovalent Na+ doped La1–xNaxMnO3 (LNMO; x = 0.00, 0.05, 0.10, 0.15, 0.20, 0.25 and 0.30) manganites synthesized by conventional ceramic method. X-ray diffraction (XRD) and Rietveld refinements reveal the single phasic nature of LNMO manganites without any detectable impurity within the measurement range. Temperature dependent resistivity, under different applied magnetic fields, has been performed on LNMO samples. Samples understudy exhibit metal to insulator (semiconductor) transition at temperature TP which is strongly influenced by the substitution of Na+ at La3+ site. r – T plots also exhibit resistivity upturn behavior at low temperature well below 40K under all the applied fields. Variation in TP and resistivity has been discussed in the context of the competition between the transport favoring tolerance factor and zener double exchange (ZDE) mechanism and transport degrading Jahn–Teller (JT) and size variance effects. In order to understand the mechanisms responsible for the charge transport in metallic and semiconducting regions and to explore the possible electronic processes responsible for the observed low temperature resistivity minima in all the presently studied LNMO manganites, various models have been employed. It has been found that VRH mechanism gets successfully fitted to the resistivity data in the semiconducting region while ZDE polynomial law is responsible for the charge conduction in metallic region for all the presently studied LNMO samples. A strong dependence of activation energy on the Na+ – content as well as applied magnetic field has been discussed in the context of variation and interrelations between the structural parameters. Charge conduction in metallic region has been discussed in the light of electron–phonon interactions which is influenced by the Na+ – content and applied magnetic field. Electrostatic blockade model has been employed to understand the low temperature resistivity minima behavior. Blocking energy for the charge carriers shows a dependence on the magnetic energy provided to the charge carriers. Present study can be useful to understand and to control the charge conduction in the manganites and hence to design the manganite based thin film devices for various spintronic applications.

Low-pressure air plasma induced modification of structural and electrical properties of Gd1− x Sr x MnO3 manganites

The structural and electrical properties of Gd1−x Sr x MnO3 manganites pellets with different doping concentrations x (= 0.2,0.3,0.4,0.5) are modified using an easy low-pressure plasma irradiation method. Powder x-ray diffraction studies of the samples revealed that lattice parameters a and c increase with doping as well as plasma exposure except for x = 0.5 for which a decreases. On the contrary, lattice parameter b decreases with doping as well as plasma exposure and is more pronounced. The crystallite size increases with increasing doping concentration both with or without plasma exposure. Plasma exposure tends to decrease the Mn–O–Mn bond angle as well as the Mn–O bond length. The temperature-dependent electrical resistivity of samples reveals that the pristine Gd1−x Sr x MnO3 exhibits insulating behavior for all the doping concentrations. However, the resistivity is enhanced at low temperature for all samples after plasma exposure. The variation of electrical resistivity after plasma exposure may be attributed to the disorder near the grain boundaries and cell volume. The resistivity behavior is unaffected by plasma exposure for all samples. The small polaron hoping model explains the conduction mechanism at high temperature while the conduction at low temperature is attributed to variable range polarons.

Effect of Heat Treatment Conditions on Microstructures and Mechanical Properties of Cu-9Ni-6Sn-0.22Nb Alloy

Due to its high strength, excellent electrical conductivity and high resistance to stress corrosion, Cu-Ni-Sn alloy has been selected as a kind of advanced metal material which can be used as the manufacture of springs, connectors, bearings and so on. In addition, the addition of Nb can efficiently improve the comprehensive properties of the alloy. In the present work, the effect of heat treatment conditions on microstructure and mechanical properties were studied in a Cu-9Ni-6Sn-0.22Nb alloy by means of optical microscopy (OM), transmission electron microscopy (TEM), tensile test and microhardness tests. The results show that before ageing, a large number of fine γ precipitates with DO22 type structure are distributed on the matrix. With the prolongation of ageing time, the ultimate tensile strength (UTS), yield strength (YS) and Vickers hardness increased firstly, and then decline. The reason can be attributed to the occurrence of spinodal decomposition and the formation of discontinuous precipitation (DP). At first, spinodal decomposition induced the enhanced interaction between dislocations and internal stress field, resulting in an increase of mechanical properties. Then the increased DP at grain boundaries leads to the decline of strength in the material. Finally, the relationship between the microstructure and the electrical conductivity was also analyzed, and the results show that the electrical conductivity increased with ageing time/ageing temperature increasing for the present alloy. Through the analysis of Matthiessen’ s rule, the variation of electrical resistivity depends on precipitates, solute atoms, dislocations, vacancies and grain boundaries, and the precipitates play an important role among them. Besides, more precipitates improve electrical conductivity. Therefore, the increase of ageing time/ageing temperature induced the increase of DP, resulting in an increase of electrical conductivity.

Characterization of Structural Defects in (Cd,Zn)Te Crystals Grown by the Travelling Heater Method

Structural defects and compositional uniformity remain the major problems affecting the performance of (Cd, Zn)Te (CZT) based detector devices. Understanding the mechanism of growth and defect formation is therefore fundamental to improving the crystal quality. In this frame, space experiments for the growth of CZT by the Travelling Heater Method (THM) under microgravity are scheduled. A detailed ground-based program was performed to determine experimental parameters and three CZT crystals were grown by the THM. The structural defects, compositional homogeneity and resistivity of these ground-based crystals were investigated. A ZnTe content variation was observed at the growth interface and a high degree of stress associated with extensive dislocation networks was induced, which propagated into the grown crystal region according to the birefringence and X-ray White Beam Topography (XWBT) results. By adjusting the growth parameters, the ZnTe variations and the resulting stress were efficiently reduced. In addition, it was revealed that large inclusions and grain boundaries can generate a high degree of stress, leading to the formation of dislocation slip bands and subgrain boundaries. The dominant defects, including grain boundaries, dislocation networks and cracks in the interior of crystals, led to the resistivity variation in the crystals. The bulk resistivity of the as-grown crystals ranged from 109 Ωcm to 1010 Ωcm.

Radio‐magnetotelluric and controlled‐source magnetotelluric surveys on a frozen lake: Opportunities for urban applications in Nordic countries

ABSTRACTIn a novel approach, we have carried out controlled‐source and radio‐magnetotelluric measurements in the frequency range of 2–250 kHz on a frozen lake located over a planned major multi‐lane underground road tunnel near the city of Stockholm. The aim was to gain a better understanding of the resistivity variations above and, potentially, within the crystalline bedrock. Previous studies on the lake water using the boat‐towed radio‐magnetotelluric technique at the higher end of the frequency band lacked resolution at depth and could not provide conclusive information about bedrock level and potential fracture systems within the bedrock. Taking advantage of Nordic winters, we measured four profiles on the frozen lake complementing the previously acquired boat‐towed radio‐magnetotelluric data utilizing a double horizontal magnetic dipole transmitter that generated signals down to 1 kHz. The new resistivity models, incorporating the lower frequency data, show improvements and deeper penetrations based on a combined analysis of penetration depth, data misfits and sensitivity studies. The resistivity models also show better correlation with the available high‐resolution shallow water seismic reflection data and the geological observations. A potential fracture system within the bedrock can also be inferred better in the new models. The idea of running similar surveys on frozen lakes can be further exploited in similar conditions in countries such as Sweden, where approximately 7% of the land is covered by freshwater bodies and poorly explored for infrastructure planning projects.

Transport and thermal properties of single crystal TaNiTe5

Here, we study the thermal and transport properties of topological single crystal TaNiTe5 down to near 0 K and magnetic fields up to 14 T. By analyzing the variation of resistivity ρ and Seebeck coefficients S with temperature T, we provide the evidence of electron-electron scattering and electron-phonon scattering in the lower and higher temperature region, respectively. The dependence of S and κ on magnetic field H is well described by two-band model of conduction |ΔS/S|∝Hn and |Δκ/κ|∝Hn for various temperatures, which also suggests electron and phonon are two kinds of carriers and benefit to the thermal conduction.

Geophysical characterization of volcanic layering

Seismic methods, electrical resistivity, and outcrop observations provide an integrated subsurface view of young basaltic lavas and their overlying weathered products. The study site is a sea cliff in the Kohala province in the northwestern part of the Big Island of Hawai'i, which provides an ideal laboratory for combined seismic reflectivity, shear-wave velocity, electrical resistivity, and outcrop observations. Our primary observation is the division of the shallow subsurface into weathered (saprolite) and underlying unweathered (hard basalt) zones. Significant heterogeneity is evinced by strong reflectivity changes within and between the two zones and the structural variability of the basal surface separating the weathered zone from the unweathered zone (reflector undulations, fault offsets, and prominent diffractions). Seismic reflectivity contrasts arise from variations in rigidity and porosity (density) corresponding to seaward-dipping lava flow units. The degree of clay alteration is interpreted to govern subsurface resistivity variations along with the influence of fresh groundwater and the incursion of seawater saturating the porosity. Our study provides a generalized model for visualizing weathered versus unweathered basaltic lavas in the shallow subsurface.

Geoelectrical structure and monitoring in fault zones of Uimon depression in Gorny Altai region using electromagnetic methods

In this paper we present the results of our studies of sections of the Uimon basin in Gorny Altai (Russia) using a complex of electrical prospecting methods. The areas of Baratal Formation at the surface have been investigated. This areas explored in order to understand the stages of formation of the depression. In addition, the possibilities of the electrotomography method for regular observations in seismoactive regions are shown. Comparison of the amplitudes of the resistivity variations based on repeated ERT measurements in different zones of the Terekta fault indicates the activity of its eastern part, which is expressed in significant resistivity variations exceeding 100%. At the same time, the variations in the northwestern part of the fault, reaching 15% on average, are many times smaller.

Monitoring of LISS Nozzle Proximity to CANDU® Fuel Channels Using the Eddy Current Gap Probe

Fuel channels in CANDU® (CANadian Deuterium Uranium) nuclear reactors consist of two non-concentric tubes; an inner pressure tube (PT) and a larger diameter calandria tube (CT). The gas annulus space between the 6 m long tubes, known as the gap, is monitored from within the PT using a transmit-receive eddy current probe that can detect changes in the environment using electromagnetic induction according to Faraday’s Law. Accurate measurements are required to ensure that contact between PT and CT is not imminent. Fuel channels may also pass over perpendicularly oriented tubes (nozzles) that are part of the liquid injection shutdown system (LISS). The proximity of LISS nozzles not only compromises gap measurement, but flow-induced vibrations from within the moderator could lead to CT deformation and/or fretting at LISS-CT contact. Investigation of the eddy current based gap probe as a tool to measure proximity of LISS nozzles was carried out experimentally. Eddy current response as a function of LISS-PT proximity, the distance between the PT outer diameter and LISS nozzle outer diameter, was determined. When PT wall thickness, PT resistivity, probe lift-off, and PT-CT gap variations spanned typical values found in-reactor this dependence could be used to determine the LISS-PT proximity up to 20 mm with sub-millimeter accuracy. This method has the potential to provide LISS-CT proximity using existing gap measurement data. Obtaining LISS nozzle proximity at multiple inspection intervals could be used to provide an estimate of the time to LISS-CT contact, and thereby, provide a means of optimizing maintenance schedules.

Stress-Induced Apparent Resistivity Variations at the Kalpin Observatory and the Correlation with the 2020 Mw 6.0 Jiashi Earthquake

Stress may induce apparent resistivity changes. Clarifying the deformation process of the source media is critical for determining the correlations between resistivity variations and earthquake occurrence. In this study, the stress state of a medium was analyzed by integrating GPS measurements, the spatiotemporal evolution of the load/unload response ratio (LURR), geochemical monitoring, and synchronous apparent resistivity changes preceding the 2020 Mw 6.0 Jiashi earthquake. The medium hosting the Kalpin Observatory underwent elastic deformation before 2019, and the synchronous decreases in the E–W and N–S apparent resistivities from 2015 can be attributed to N–S-dominated compressive stress. The microdamage stage occurred in 2019, with subsequent E–W apparent resistivity variation amplitudes that were ~0.4 Ωm higher than those in previous years. This difference is a result of microdamage to the medium owing to tensile stress during the seismogenic process. The spatiotemporal evolution of the LURR and gas seepage monitoring data also indicate that the medium was damaged prior to the earthquake. Variations in the apparent resistivity measured at the Kalpin Observatory indicate that the medium underwent elastic deformation, followed by microdamage, until stress triggered the earthquake.

Electrical resistivity imaging of continental United States from three-dimensional inversion of EarthScope USArray magnetotelluric data

Long-period magnetotelluric (MT) sites, covering much of the continental United States (US) have been collected through the EarthScope USArray MT Transportable Array (TA) project. Previous regional studies using subsets of these data suggest large-scale variations in deep (sub-lithospheric) resistivity, often of significant amplitude. Here, we present a range of three-dimensional (3D) continental-scale electrical resistivity models from 3D inversion of the MT TA data, with a focus on testing robustness and resolution of this deep structure. The main features of our initial model, obtained with no constraints, are quite similar to those from previous studies, with significant (±1 order of magnitude) lateral variations in deep resistivity. We show that data fit, as measured by global normalized root-mean-square misfit, is not increased by replacing structures below 200 km depth with layer averages. A more careful examination of residuals leads to further refinements, with a slight improvement in data fit. These include a moderately conductive mantle transition zone (13Ω.m), and subtle (±1/4 order of magnitude) lateral variations in resistivity below 200 km. In contrast to the initial results, these variations can be explained by reasonable variations in mantle temperature and hydration. Overall, our results suggest that the asthenospheric mantle at 200–275 km is nearly dry on average and at greater depths contains 150–300 ppm water. Lateral variations may be explained by this range of water content, or by temperature variations of 80–120∘C. Patterns of resistivity variations below 200 km are consistent with known continental structure, and suggest deep roots (∼250 km) beneath cratons, and perhaps also beneath the mid-continent rift. Reduced resistivity, likely requiring greater hydration (or higher temperatures), occurs beneath the North-central part of the continental US, the oldest part of the continent, and beneath the Yellowstone hotspot.

Electrical Characterization of Hydrogenated Boron Carbon Nitride Thin Films at Cryogenic Temperatures

Compounds in boron-carbon-nitrogen ternary triangle such as diamond (C), cubic boron nitride (c-BN), and boron carbide (B4C) have gained attention due to their covalent bonding, short bond lengths, low atomic mass[1]. These materials exhibit low dielectric values along with excellent mechanical and thermal strength. Boron carbon nitride (BCN) compounds are known to combine unique properties of boron carbide and boron nitride, with the properties being tunable with varying elemental composition and structure. These outstanding properties have made BCN attractive and finds multi-functional applications in anti-wear and protective coatings, supercapacitors, UV detectors, nanobiotechnology and nanomedicine[2]. BCN thin films also find opto-electronic applications in the harsh environments. While addition of small amounts of hydrogen has been proven beneficial for electrical and optical properties in BCN films, the electrical behavior of hydrogenated BCN films at low temperatures is not evaluated. Such evaluations will further expand the use of of hydrogenated BCN for extreme temperature applications.In this study, BCN thin films are deposited using RF magnetron sputtering with varying hydrogen/nitrogen gas flows. Substrate temperature is kept constant at room temperature. Dual target sputtering from B4C and BN targets is performed to deposit BCN thin films. I-V characterization is performed from room temperature to 70 K. The variation in resistivity with reactive gas flow rate at low temperature is reported.