Electrical Conduction Mechanism Research Articles

Exploration of electrical conduction mechanisms via modulating sintering period of La0.67Ca0.33MnO3 films in various phase regions

Perovskite manganese oxide films have garnered significant attention due to their unique and diverse physical properties. In this work, La0.67Ca0.33MnO3 (LCMO) films are prepared on LaAlO3 (00l) substrates using the sol−gel spin coating method with varying sintering period (Ps). By optimizing Ps, improvements were observed in the films’ structure, morphology, ionic valence, and temperature−dependent resistivity. The reduction in Mn−O bond length and the increase in Mn−O−Mn bond angle change the degree of MnO6 distortion, resulting in an increased eg bandwidth. As Ps increased, the LCMO films exhibited better crystalline quality. The improved Mn4+/Mn3+ ratio strengthened the double exchange effect, facilitating the carrier hopping of the eg electrons. Analyses of various electrical conduction mechanisms showed that optimized electron scattering behavior, reduced hopping distance, energy and theoretical Curie temperature collectively enhance the temperature coefficient of resistivity (TCR) of LCMO films under optimal Ps. The TCR of the LCMO films reached a maximum value (31.64 % K−1) at Ps = 18 min. These findings offer valuable insights into the main electrical conduction mechanisms in both metallic and semiconducting phases, providing a deeper understanding of the underlying physical processes and offering experimental guidance for optimizing the electrical transport properties of perovskite films.

Electrical properties and conduction mechanisms of ε-GaSe films for selector and phase-change memory applications

Owing to the pressing requirement for advanced memory solutions driven by explosive data growth, nonvolatile and fast-operating 1S1R structured XPoint memory has become a prominent focus, with recent interest shifting towards the 1S structured selector-only memory. The use of chalcogenide-based materials in these technologies constrains the application of such memories because of their complex quaternary compositions. This study investigated the previously unreported potential of GaSe, a simple binary Se-based chalcogenide, for applications as a selector and phase-change memory (PCM). In this study, ε-GaSe thin films were deposited using thermal evaporation and subsequently annealed in a Se atmosphere for 1 and 2 h. These ε-GaSe thin film devices incorporated metal–insulator–metal construction to exhibit both selector and PCM characteristics. The ε-GaSe device that was Se-annealed for 1 h demonstrated superior performance with a lower threshold voltage and off current, high selectivity as a selector, and reduced set voltage and reset power as a PCM. These characteristics render the proposed device a highly promising candidate for dual selector/PCM applications. To explain the electrical behavior of the ε-GaSe device, we propose the conduction mechanism model depending on the Se-annealing time, which is related to the change in the physical properties of ε-GaSe.

The Electrical Conductivity Mechanisms and Dielectric Properties of Multiphase Co-synthesized CuV2O6–MnV2O6

AbstractMany research studies on photodegradation, energy storage applications, and biosensing have focused on single and mixed Cu and Mn divanadates (MV2O6, M2+ = Cu2+ and/or Mn2+). In this work, MV2O6 was synthesized, and its electrical conductivity and dielectric properties were studied. The electrical and dielectric properties were investigated in a frequency range of 0.1-300 kHz and a temperature range of 298 K to 573 K. The results indicate that the DC conductivity, AC conductivity, dielectric constant, dielectric loss factor, and loss tangent of the investigated materials increase with temperature, which support the contribution of grains and grain boundaries to the electrical properties. The materials exhibit non-Debye type relaxation, as indicated by the progression of the relaxation frequency. As frequency increases, the activation energy of AC conduction decreases, indicating that hopping conduction is the dominant mechanism. In all samples, the DC conduction activation energy is higher than the AC conduction activation energy. The circuit model was used to estimate the relaxation times. The results revealed remarkable dielectric characteristics, notably higher dielectric loss tangent values at frequencies below 1 kHz. Consequently, these materials can be used as electromagnetic attenuation absorbers. Graphical Abstract

Synthesis, Structural, Morphology and Magnetic Properties: Effect of La on Multiferroic Nature of BiFeO3 Nanoparticles

Objectives: The present study focuses on developing La-doped BiFeO3 multiferroic materials for dielectric absorber applications. Methods: The samples are characterized by X-ray Diffractometer (XRD). Further, the morphology is examined using field emission electron microscopy (FESEM) and Transmission Electron Microscopy (TEM). The dielectric parameters and ac-electrical parameters are carried out by impedance spectroscopy. The magnetic properties are studied using a vibrating sample magnetometer VSM, P-E loop. Findings: XRD confirms the rhombohedral (trigonal) structure of BLFO nanoparticles. The grain and particle size values are determined by SEM and TEM, respectively. The dielectric and ac-electrical parameters for all the samples are thoroughly discussed at room temperature. The Maxwell-Wagner or interfacial polarization is noticed at low input field frequencies for x=0.2-0.8. The impedance analysis shows the contribution of grain and its boundary in the electrical conduction mechanism. The multiferroic behavior is examined using M-H loops, P-E loops, and μi-f plots. Novelty: The samples are synthesized by the hydrothermal process to prepare La-doped BiFeO3 nanomaterials. Keywords: Nanoparticles, Electron Microscopy, Multiferroic, Magnetization, Polarization, Permeability

Mixed-valence Sm-doped LaF3 crystals as ion-electron conductors: Crystal growth and impedance characterization

The single crystals with the composition La1−y(Sm3+1−xSm2+x)yF3−xyLa1−ySm1−x3+Smx2+yF3−xy(y = 0.04) were grown from melt by the vertical Bridgman technique. A part of the Sm3+ doping ions in LaF3 matrix is reduced to the Sm2+oxidation state due to interaction with carbon during the growth process. The crystals were studied by X-ray diffraction analysis, optical and impedance spectroscopy. The Sm-doped crystals LaF3 are single-phase, retaining the tysonite-type structure (sp. gr. P-3c1P3̄c1) and demonstrate a bipolar electrical conductivity mechanism. Both the ionic conductivity σi = 4.7 × 10−5 S/cm caused by heterovalent substitutions of La3+ for Sm2+ and the comparable electronic conductivity σe = 3 × 10−5 S/cm due to the variable oxidation states Sm2+/Sm3+ ions were detected for the grown crystals. The discovered mixed ionic-electronic conductivity of La0.96Sm3+0.004Sm2+0.036F2.964 crystals opens up a new direction for the practical application of the tysonite-type fluorides as a component of electrode materials for fluorine-ion current sources.

An In-depth Analysis of Dielectric and Electrical Conduction Mechanisms in Magnesium-Substituted LiTaO3 Solid Solutions

An In-depth Analysis of Dielectric and Electrical Conduction Mechanisms in Magnesium-Substituted LiTaO3 Solid Solutions

Dielectric relaxation and electrical conduction mechanism via hopping of polarons in (Pb0.3Bi0.7)(Zn0.1Nb0.2Fe0.7)O3 perovskite compound: A study based on CBH model

This work analyses the dielectric and conducting properties of the PZN-modified BF solid solution (0.3PZN-0.7BF) synthesized at 850 °C by solid-state reaction. The Rietveld refinement of 0.3PZN-0.7BF solid solution displays three phases: tetragonal Pb(Fe0.5Nb0.5)O3 (76.68 %), α-BZN (21 %), and Bi2Fe4O9 (2.32 %). Dielectric parameter frequency dispersion implies normal ferroelectricity. Thermal relaxation shifts dielectric loss, imaginary impedance (Z''), and loss modulus (M'') peaks to higher frequencies. Electrical investigation indicates electrode polarization, dipole orientation, charge ordering, oxygen vacancies, and defects. Investigations suggest p-type polarons dominate conductivity. At room temperature and 1 MHz, the compound has 117 dielectric constant and 0.009 tangent loss. Conductivity and impedance testing show semi-conductivity. UV–Vis spectrum investigation shows a 1.97 eV energy band gap, supporting its semiconductor properties. Photovoltaic and optoelectronic device applications benefit from 0.3PZN-0.7BF solid solution optical and electrical property studies.

Correlated barrier hopping transport and non-Debye type dielectric relaxation in Zn2V2O7 pyrovanadate

Herein, the Zn2V2O7 electro-ceramic pyrovanadate was synthesized via a conventional solid-state reaction technique and calcined at 700 °C. The single phase formation of Zn2V2O7 pyrovanadate crystallized in the monoclinic structure with C12/c1 space group was confirmed by X-ray diffraction (XRD). The XRD powder diffraction profile was analyzed by Rietveld refinement to investigate the structural details of the compound. The complex impedance analysis was carried out in the frequency domain of 83−2×106 Hz over a temperature range of 453–613 K to study the electrical charge conduction and dielectric relaxation mechanism in the material which revealed the presence of the distribution of relaxation times with thermal charge activation. Depressed semicircles in the Nyquist plots were modeled by an equivalent circuit with configuration (RGCG)(RGBQGB) which resolved the contributions of grains and grain boundaries towards the transport properties of the material. The electrical conductivity spectra followed Jonscher's power law behavior and the temperature variation of frequency exponent suggested correlated barrier hopping (CBH) as the governing transport mechanism in the Zn2V2O7 pyrovanadate system. The comparison between scaling behaviors of imaginary parts of impedance and modulus advocated the temperature-independent nature of relaxation time distribution. The imaginary electrical modulus spectra were reproduced by the Kohlrausch, Williams, and Watt formulism, and the fitted parameters confirmed the non-Debye type nature of the dielectric relaxation. Further, the Haveriliak-Negami function was employed to investigate the dielectric response of the material which was found to be consistent with impedance, conductivity, and modulus analyses. The frequency dispersion of the tangent loss verified that the hopping mechanism was thermally activated.

Multi-scale structural regulation of negative temperature coefficient effect and electrical conduction mechanism of xSm2O3-(1-x) CaCu3Ti4O12 ceramics

In this work, a series of xSm2O3-(1-x) CaCu3Ti4O12 (xSm2O3-(1-x)CCTO, x = 0.00-0.05) negative temperature coefficient (NTC) ceramics were prepared by a solid-state method. The influence of Sm2O3 content on electrical properties was examined using microstructural, band gap, morphological, Direct Current (DC) resistivity, and impedance spectroscopy analysis. The increase in Sm2O3 content resulted in a gradual decrease of the resistivities (ρ25), thermal constants (B25/75), activation energies for electrical conduction (Ea) and activation energies of the relaxation process (Erelax) from 1.16×107 Ω•cm, 6387 K, 0.5456 eV and 0.5592 eV to 3.43×105 Ω•cm, 4149 K, 0.4088 eV and 0.4115 eV respectively. First-principles calculations revealed a reduction in the band gap by adding Sm2O3, partially explaining the decrease in electrical resistivity. In-situ XPS analysis elucidated a relationship between conduction mechanism of Sm2O3-doped CCTO ceramics and electron hopping. Impedance analyses showed that both grains and grain boundaries contributed to the NTC effect of ceramics. The electrical inhomogeneity arose from grains and grain boundaries, while local relaxation was due to the short-range motion of charge carriers.

Atmospheric modulation of apparent electrical conductivity in a metal−organic framework

Combining high surface area and efficient charge transport, electrically conductive metal−organic frameworks (MOFs) find wide applications in energy storage, sensing, and electrocatalysis. Reliable characterization of electrical conductivity, the key metric for assessing this class of materials, remains challenging due to its high sensitivity to the atmosphere. Herein, through electrical characterization of an exemplary MOF, Cd2(TTFTB) (TTFTB4− = tetrathiafulvalene tetrabenzoate), under various controlled atmospheres, we show that adsorption of water in humid air or N2 improves the apparent room-temperature electrical conductivity by one to two orders of magnitude compared to the values observed in dry atmospheres. This observation in conjunction with spectroscopic characterization, structural analysis, and band structure calculations indicates significant contribution of water-mediated proton conductivity and/or proton-electron coupling to the apparent electrical conductivity. Thus, controlling and reporting atmospheres in electrical conductivity measurements of MOFs is critical to improve their reproducibility and to gain insights into electrical conduction mechanisms.

Impact of Mo+2 addition and thermal annealing on the surface morphology, electrical transport properties and Mott's parameters of WO3 films for potential photonic devices

This work investigates the compositional dependence and thermal annealing of the morphological properties, electrical conductivity mechanisms and Mott's parameters of sprayed MoxW1-xO3 (x = 0, 0.05, 0.10 and 0,20) thin films. The prepared thin films were examined using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDX) and Fourier transform infrared spectroscopy (FTIR) techniques. In addition, the two-point probe method was used to calculate the electrical properties of MoxW1-xO3 thin films. The FTIR results revealed that; the tungsten hydroxyl bond (W-OH) and the surface hydroxyl group vibrated within the ranges of 1558.62–1645.56 cm−1 and, 3296.76 and 3424.34 cm−1, respectively. Furthermore, a prominent band in the spectrum spanning from 850 to 650 cm−1 represents the W-O-W bridge mode. The FE-SEM investigations found that the molybdenum (Mo) dopant caused significant changes in the surface morphology of the films. The EDX results showed that the percentages of the isotropic elements MoxW1-xO3 agreed well with those obtained by atomic weight. Studies of the conduction mechanism indicate that the transition temperature was approximately 393K. Corresponding to Mott's model, the conduction mechanism below this temperature was across the variable hopping conduction band near the Fermi level. The mechanism exhibited a cycle of localised states through activated thermionic emission above 393K. Mott parameters were also estimated in addition to barrier potential energies, trapping state energies, local state densities, and other variables. The results revealed that both temperature areas had a rise in ρo and ρ1 values during and after annealing. The ΔEo and ΔE1 values in each temperature area decreased as the Mo-ion concentration increased. Furthermore, the conversion temperature gradually reduced as Mo was added. Based on these properties, the study's overall findings indicate that MoxW1-xO3 is suitable for future photonic devices and optoelectronic applications.

Effect of Phytic Acid, Tin Oxide and Graphite Incorporation in Polyaniline Semiconductive Ink

Enhanced electrical conductivity and pressure sensing functionalities of phytic acid-doped polyaniline ink (PPhyA) incorporated with SnO2 (PPhyAS) and graphite flakes (PPhyAG) as reported in our previous article, encouraged us to explore the electrical conduction mechanism and associated optical properties. In order to realize the enhanced electrical conduction in the reported inks, detailed studies were carried out in our research described here in comparison with normal HCl-doped polyaniline (PANI). This can be attributed to the formation of a highly ordered molecular arrangement with high crystallinity, a change in the hopping pathway between two adjacent molecules and the hopping activation energy of the PANI chain in the phytic acid-doped ink systems. Optical parameters, such as absorption edge, Urbach energy, refractive index, extinction coefficient, optical conductivity and optical dielectric constants, were estimated from the result of UV-Vis spectroscopy. The results of these studies showed enhancement of the optical properties of the phytic acid-doped ink systems (PPhyA, PPhyAS and PPhyAG) in the low photon energy range as compared to HCl-doped PANI. Phytic acid-doped ink systems are paintable on a variety of flexible surfaces, such as paper and plastics. Hence, we suggest that the phytic acid-doped ink systems have a great potential for developing flexible and foldable circuitry for infrared optics and remote sensing.

Influence of nature melanin on the structural, linear/nonlinear optical properties and electrical conduction mechanism of PVA/CMC/PPy blended polymers for optoelectronic applications

Polyvinyl alcohol (PVA) and carboxymethyl cellulose (CMC) have been used as polymeric matrices to create polymeric nanocomposite films that contain polypyrrole (PPY) and melanin as fillers. The structure of the PVA/CMC/PPy/x wt % melanin blends was analyzed using the X-ray diffraction technique. The scanning electron microscopy technique was used to investigate the morphologies of the blends. The highest absorbance and reflectance spectra were observed when the melanin content reached 0.25 and 0.2 % wt %, respectively. The smallest direct and indirect optical band gaps are (4.91, 4.44) eV and (4.22, 3.79, 2.34) eV, respectively, achieved when the melanin content was 0.25 wt%. The blend doped with 0.15 wt% PANi yielded the highest refractive index values (1.396 at λ = 600 nm). The optical dielectric constant values of the blends exhibited irregular improvement when the PVA/CMC/PPy blended polymer was filled with varying quantities of melanin. The blend doped with 0.15 wt% melanin exhibits the highest optical conductivity values in the visible range. The blend of PVA/CMC/PPy with a melanin concentration of 0.15 or 0.2 wt% demonstrated the highest nonlinear optical parameters. The blend of PVA/CMC/PPy with a melanin concentration of 0.15 or 0.2 wt% demonstrated the highest nonlinear optical parameter. Based on the observed behavior of the I-V characteristic, the possibility of ohmic conduct ions or space charge limited conduct ions is ruled out in all blends. The charge transport mechanisms that take place in different blends under varying temperatures were examined. These outcomes suggest the opportunity of employing the created blended polymer in capacitive energy storage, optoelectronic devices and photocatalytic application.

Modified Liquid Electrolyte with Porous Liquid Type-II for Lithium-Metal Batteries

Liquid electrolytes modified by adding type-II porous liquid (PL) were designed and prepared to study its effect on the performance of lithium-metal batteries. Porous liquids provide internal, permanent, and empty porosity which are capable of coordinating and transporting Li+. The potential of the porous liquid to capture and transport ions with high mobility leads to enhancement in battery performance. In this study, the physicochemical properties of electrolytes, mechanism of solvation, transport, and electrical conductivity of lithium ions through the new electrolytes will be presented, and the potential of the liquid electrolyte based on the type-II porous liquid to develop the battery performance was investigated. This modification effectively improved the Li ionic conductivity of the electrolyte because of the Li+ ion solvation by type-II PL. The dissociation of Li+-TFSI− ion pairs and the formation of complexes with Li+ ions (Li-PL) were improved by using the type-II PL, resulting in an increase in the ionic conductivity of the electrolyte. Our findings suggest that the use of PL electrolytes can be a good candidate for improvement in physicochemical properties of electrolytes leading to an enhancement in Lithium-Metal Batteries.

Synthesis of aqueous NiFe2O4-Fe3O4 hybrid magnetic nanofluids and investigation on electrical conducting behaviour

Highly stable aqueous magnetic mono nanofluids of nickel ferrite (NiFe2O4), magnetite (Fe3O4), and hybrid magnetic nanofluids of NiFe2O4-Fe3O4 are synthesized through a two-step method. The structural analysis of the NiFe2O4 and Fe3O4 nanoparticles made through X-ray diffraction identifies their spinel cubic structure. The magnetic studies indicate their superparamagnetic nature, which is further confirmed through the Langevin fitting of the experimental data. The monodomain nature of nanoparticles is verified using the coupling constant, and a spherical morphology is observed using a transmission electron microscope. The surface charge of the nanoparticles is studied through zeta potential analysis. The electrical conductivity of the aqueous mono and hybrid magnetic nanofluids is measured for various concentrations and temperatures. The hybrid magnetic nanofluids show higher electrical conductivity values than those of both the mono nanofluids. For instance, NiFe2O4-Fe3O4 (1.2 vol%) hybrid nanofluid is found to have a conductivity value of 18.91 μS/cm that is 1.5 times enhanced than that of Fe3O4 mono nanofluid (12.87 μS/cm) and three times enhanced than that of NiFe2O4 (6.43 μS/cm) mono nanofluid of same volume percentage at 303 K. A Maximum enhancement of 136 % is obtained for 1.2 vol% hybrid nanofluid with respect to water at 303 K and this enhancement further increases to 196 % with the rise in temperature to 323 K. There is no theoretical model found in literature to explain the electrical conductivity of hybrid nanofluids. Maxwell, Bruggeman, Cruz, and Shen models are applied to explain the conductivity of hybrid magnetic nanofluids. Through a comparison of experimental values with theoretical values, it is found that the Shen model, if modified suitably, can explain the electrical conduction of hybrid magnetic nanofluids. Also, the electrical conduction mechanism in hybrid magnetic nanofluids is described in terms of electrophoretic charge transportation and the Brownian motion. In addition, the magneto-electrical conductivity study is performed by measuring the electrical conductivity by applying a magnetic field of various strengths. The electrical conductivity, magneto-electrical conductivity studies and an understanding of electrical conduction mechanism are highly significant for magnetically transportable electronic cooling and conducting applications of hybrid magnetic nanofluids.

Temperature dependent electrical resistance and mesoscopic electronic transport mechanisms on aerographite and single-walled carbon nanotube aerogel

We investigate temperature dependent electrical resistance properties of aerographite and single-walled carbon nanotube (SWCNT) aerogel in the temperature range of 2–300 K by employing the four-probe method with magnetic field effects (in the range 0–9 T, in steps of 2 T). The current–voltage (I–V) curves were taken for several temperatures varying from 5 to 300 K, and the electrical resistance values of aerographite and SWCNT aerogel were decreased from 7.30 Ω (5 K, 0 T) to 4.88 Ω (300 K, 0 T) and 22.56 Ω (5 K, 0 T) to 0.99 Ω (300 K, 0 T) with temperature increases, respectively. Experimental results show that the electrical resistance falls exponentially as the temperature increases. Such temperature dependence of R(T) points to a form of tunneling conduction or hopping. Two mesoscopic mechanisms for electronic transport, fluctuation-induced tunneling conduction (FITC) and variable range hopping (VRH), are employed to explicate possible electrical conduction mechanisms occurring in aerographite and SWCNT aerogel, respectively. These mainly result in disorder-induced symmetry-breaking, which are modified by their structural symmetries and electronic band structures, both play important roles in temperature dependent electrical resistance properties of aerographite and SWCNT aerogel. Characteristic parameters (T0, T1, and R0) have been estimated using the morphology and the uncertainty principle for aerographite and the percolation theory for SWCNT aerogel. While the FITC mechanism captures a wide temperature range of data for aerographite, the VRH model provides an explanation for SWCNT aerogel. This study provides groundwork for further development of carbon aerogel systems with high conductivity in large-scale preparation.

Electrical conductivity and relaxation mechanisms of nanocrystalline Ba0.75Ca0.2Cs0.05TiO3

Ca and Cs doped barium titanate lead-free ceramic with the formula Ba0.75Ca0.2Cs0.05TiO3 has been prepared by the solid-state reaction method. X-ray diffraction (XRD) confirms the crystallization of the sample in a tetragonal structure with a P4mm space group. The phase purity and grain morphology were evaluated using X-ray diffraction and scanning electron microscopy (SEM). The material exhibits a primary phase of Ba0.75Ca0.2Cs0.05TiO3 with a minor secondary phase of BaO2, and the average grain size is determined to be 1.66 μm. Using non-destructive complex impedance spectroscopy (CIS), we extensively studied the electrical behavior, including complex impedance (Z*), complex modulus (M*), electrical conductivity, and relaxation mechanisms, of Ba0.75Ca0.2Cs0.05TiO3 over a wide temperature (85 K–290 K) and frequency range. The ac conductivity analysis reveals that the dominant conduction mechanism is the non-overlapping small polaron tunneling (NSPT) model. The impedance analysis indicates a single semi-circle in the real and imaginary parts, suggesting a single relaxation mechanism. Additionally, the activation energy was calculated to be approximately 0.0489 eV. These findings contribute to the understanding of the structural and electrical properties of Ba0.75Ca0.2Cs0.05TiO3, highlighting its potential applications in electronic devices such as capacitors, thermistors, and ferroelectric random access memories (FRAMs).

Investigating the dielectric characteristics, electrical conduction mechanisms, morphology, and structural features of mullite via sol-gel synthesis at low temperatures

This research explores the fabrication of mullite precursor powder utilizing the sol-gel process at low temperatures. Silicon tetraethoxide (Si(C2H5O)4) and aluminum nitrate nonahydrate (Al(NO3)3.9H2O) were employed as the sources of SiO2 and Al2O3 oxides, respectively. Various analytical techniques, such as Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG), dilatometry, differential thermal analysis (DTA), and X-ray powder diffractometer (XRD), were utilized to investigate the formation and crystallization of the amorphous powder. The microstructure of specimens sintered at 1600 °C for 1 h was examined utilizing scanning electron microscopy (SEM). Measurements of hardness (HV) and coefficient of thermal expansion (CTE) were conducted on mullite samples heated to 1600 °C and then cooled, revealing an increase in HV from 888 to 1000 HV as the sintering temperature rose from 1500 to 1600 °C. The CTE of mullite within the temperature range of 50–1300 °C was determined as 5.23 × 10−6/°C. Additionally, the dielectric and electrical characterization of mullite was analyzed utilizing complex impedance spectroscopy at a frequency of 0.1–106 Hz and conductivity measurements over a temperature range of 40–400 °C. The real and imaginary parts of the dielectric permittivity exhibited frequency-dependent and temperature-dependent behaviors. Significantly, the observed variations in the imaginary component of the modulus and impedance maximum frequency point to a relaxation process that is not Debye-type, with calculated activation energies (Ea) consistent across different methods.

Electrical Conduction Mechanism of Mg-Doped ZrO2 Thin Films.

Amorphous ZrO2 thin films with increasing Mg content were deposited on quartz substrates, by dip coating method. The films are transparent in the visible domain and absorbent in UV, with an optical band gap that decreases with the increase of Mg content, from 5.42 eV to 4.12 eV. The temperature dependent conductivity measurements showed typical semiconductor comportment. The decrease of the electrical conductivity by Mg doping was related to the increase of the OH groups (37% to 63%) as seen from X-ray Photoelectron Spectroscopy. It was found out that the electrical conductivity obeys the Meyer-Neldel rule. This rule, previously reported for different disordered material systems is obtained for ZrO2 for the first time in the literature. Exploring novel aspects of Mg-doped ZrO2, the present study underscores the origin of the Meyer-Neldel rule explained by the small-polaron hopping model in the non-adiabatic hopping regime. Determination of the presence of such a conduction mechanism in the samples hold promise for comprehending the important aspects, which might be a concern in developing various devices based on Mg-doped ZrO2.

Programmed Heterostructures for Enhanced Electrical Conductivity.

Interfacial electron transport in multicomponent systems plays a crucial role in controlling electrical conductivity. Organic-inorganic heterostructures electronic devices where all the entities are covalently bonded to each other can reduce interfacial electrical resistance, thus suitable for low-power consumption electronic operations. Programmed heterostructures of covalently bonded interfaces between ITO-ethynylbenzene (EB) and EB-zinc ferrite (ZF) nanoparticles, a programmed structure showing 67 978-fold enhancement of electrical current as compared to pristine NPs-based two terminal devices are created. An electrochemical approach is adopted to prepare nearly π-conjugated EB oligomer films of thickness ≈26nm on ITO-electrode on which ZF NPs are chemically attached. A "flip-chip" method is employed to combine two EB-ZnFe2O4 NPs-ITO to probe electrical conductivity and charge conduction mechanism. The EB-ZnFe2O4 NPs exhibit strong electronic coupling at ITO-EB and EB-NPs with an energy barrier of 0.13eV between the ITO Fermi level and the LUMO of EB-ZF NPs for efficient charge transport. Both the DC and AC-based electrical measurements manifest a low resistance at ITO-EB and EB-ZF NPs, revealing enhanced electrical current at ± 1.5V. The programmed heterostructure devices can meet a strategy to create well-controlled molecular layers for electronic applications toward miniaturized components that shorten charge carrier distance, and interfacial resistance.