Electrical Conductivity Of Thin Films Research Articles

Porous Ti3AlC2 MAX phase enables efficient synthesis of Ti3C2Tx MXene

AbstractMXenes, a large family of two‐dimensional carbides and/or nitrides, are among the most studied materials worldwide due to their great diversity of structures and compositions. Their unique properties find use in several applications. Typically, they are manufactured by selective wet‐chemical etching of layered MAX phase ceramics, which are produced nowadays primarily for MXene synthesis. However, the synthesis of MAX phases has not been changed since the time of their use in structural and high‐temperature applications, and it has not been optimized for MXene manufacturing. The main purpose of this study is to develop a porous Ti3AlC2 MAX phase that can be easily ground into individual grains without time‐consuming, harsh, and tedious crushing and milling steps. Moreover, we also demonstrate the synthesis of highly porous Ti3AlC2 from an inexpensive titanium sponge instead of a highly pure titanium powder and explain the mechanisms of reaction sintering and formation of porous MAX phase. MXene obtained from this MAX phase, Ti3C2Tx, shows larger flake size and higher electrical conductivity in thin films, compared to the materials produced from the costly fine titanium powder. The proposed approach may apply to the synthesis of other MAX phases as well.

Role of nanocrystal incrustation in the electrical conductivity of pm-SiGe:H thin films at room temperature

The production of hydrogenated polymorphous silicon–germanium (pm-SiGe:H) has been reported as a promising material in microelectronics due to its relevant properties, such as high electrical conductivity, production cost, and manufacturing versatility. Nonetheless, the material performance at room temperature remains to be evaluated. In this work, we report an evaluation of a set of deposition conditions of pm-SiGe:H using low-frequency plasma-enhanced chemical vapor deposition (LF-PECVD). Also, the crystallinity of the samples was investigated by Raman spectroscopy and transmission electron microscopy. Furthermore, the hydrogen-dilution ratio, gas-phase germane content, and deposition pressure play an essential role in the improvement of the electrical properties and material’s structural composition due to the nanoparticle growth inside the thin film, which is a critical factor that enhances the electrical conductivity of thin films by about seven orders of magnitude.

Electrical Conductivity of Composites from Polymer Poly(Ethylene Oxide) and Nematic Liquid Crystals E8


 
 
 The electrical conductivity of thin films (150 μm) of composites produced from polymer poly(ethylene oxide) (PEO) and nematic liquid crystals E8 (in compositional ratio PEO:E8 = 70:30 wt%) was studied by means of complex electrical impedance spectroscopy in the range from 1 Hz to 1 MHz. Both ion conductivity and alternating-current conductivity of PEO/E8 films were determined as depending on temperature in the room-temperature region 25–50◦C. The results show that the ion-conductive PEO/E8 composite is a promising material for electronic applications.
 
 

Performance and electrochemical evolution of (Zn0.4Ni0.6)0.95Li0.05O thin film for Li-ion storage electrode

To improve the electrochemical performance of thin films based on Zn0.4Ni0.6O (ZNO) solid solution compound (SSC), Li-decorated ZNO [(Zn0.4Ni0.6)0.95Li0.05O, ZNLO] SSC was designed in this work. ZNO and ZNLO nanostructured thin films were prepared by RF magnetron sputtering with related lab-made ceramic targets. Phase composition, element valences, microstructure, electrochemical properties and electrochemically-induced phase evolution of the thin films were investigated. The cells assembled with ZNLO thin films as electrode deliver high reversible specific capacity of 773 mAh g−1 at 200 mA g−1 after 200 cycles, which is extremely superior to that of the ZNO thin film (363 mAh g−1). ZNLO thin film shows a high rate performance with specific capacity of 511 mAh g−1 at 1000 mA g−1 even after 750 cycles. The electrochemically induced phase evolution was studied by transmission electron microscopy, and the results revealed that nearly complete redox conversions of Zn-Ni-O ↔ Ni/Zn and ZnO ↔ Zn took place in ZNLO thin films electrode. The high electrochemical performance owes to the enhanced electrical conductivity of thin film doped with Li-ion and nanostructured characteristics of thin film that provide high specific surface and redox conversion processes.

CNTs modified ZnO and TiO2 thin films: The effect of loading rate on band offset at metal / semiconductor interfaces

ZnO and TiO2 are direct wide band gap semiconductors with intriguing properties. A wide range of applications makes it one of the most studied materials in the past decade, particularly when elaborated as nanostructures. In this work, we focus on synthesis of CNTs modified ZnO and TiO2 thin films using sol-gel method. The morphological and optical characterizations of the based ZnO and TiO2 films were carried out using scanning and transmission electron microscopy (SEM and TEM), XRD and UV spectroscopy. Electrical properties of the deposited ZnO/CNTs and CNTs /TiO2 were studied using I-V measurements at room temperature in metal/semiconductor/metal configuration, by the use of an array of metallic micro-electrodes deposited on the surface of the elaborated thin films. This allows determining qualitatively the electrical conductivity of thin films and the different parameters of the Schottky junction between the composites nano-films and the substrate. This study is necessary for future applications in solar cell.

Electrical conductivity of a thin film in the case of an arbitrarily oriented ellipsoidal isoenergetic surface of a conductor

The static electrical conductivity of a thin conducting film is calculated using the kinetic approach. The model of diffuse boundary conditions is used as boundary conditions for the charge carrier distribution function. The isoenergetic surface of the conducting film material is an ellipsoid of rotation that is arbitrarily oriented in the pulse space. The volume of the conductor is dominated by scattering on impurity atoms and on dislocations of electrons (holes). The electrical conductivity of the film is analyzed depending on the angles that determine the direction of the ellipsoid axis of rotation, and a comparison with the results for the case of a macroscopic sample is presented. A comparison is made with experimental data for the electrical conductivity of Bi and Si thin films.

Electrical conductivity of MoS2 thin films and graphite under continuous injection to protons

The electrical conductivity of thin films of MoS2 and graphite has been studied under conditions of continuous injection of low-energy protons (∼ 1-4 keV). The effect of a sharp increase (by 3-4 orders of magnitude) in the electrical conductivity of substances with a layered structure (MoS2 and graphite) at T ∼ 293 K has been established. The observed effect increases (from 2 to 10 times) as the temperature decreases from room temperature to liquid nitrogen temperature (T ∼ 77 K) and with increasing number of protons injected into the sample. The established temperature variation of electrical resistance is typical for materials with a metallic type of conductivity. It is shown that a thin surface layer, onto which protons penetrate, is responsible for the change in the electrical conductivity of MoS2 and graphite films.

Изменение электропроводности стекла, кварца и пленок Au, C, МоS2 под влиянием непрерывной инжекции протонов

Changes in the electrical conductivity of a wide range of materials with different crystal-chemical types and electrophysical properties (quartz, glass, molybdenum disulfide, graphite, gold) under continuous proton injection are studied. Film samples of layered MoS2 and graphite compounds were obtained on rough surfaces of glass or quartz by mechanical rubbing of powder. Gold films are formed on glass substrates by magnetron sputtering of a gold target. To create a continuous stream of protons injected into the test sample, a stationary ion source with a cold cathode and a magnetic field forming an ion beam of relatively low intensity was used. The current in the ion beam is up to 1.2 mA, the pressure of hydrogen in the chamber is ~10 – 2 Pa, the energy of hydrogen ions is from 1 to 4 keV. The experimental results indicate that under conditions of continuous proton injection, the electrical conductivity of thin films with a layered structure (MoS2 and graphite) increases sharply (by 4 – 5 orders of magnitude). This effect increases when the temperature decreases from ~ 293 to ~ 77 K, as well as when the number of charges supplied to the sample increases. In the case of continuous injection of protons into massive dielectrics (glass, quartz) and thin films of gold, no noticeable change in electrical conductivity was detected.

Carbon ratio effect on the electrical and morphological properties of Silicon Carbide thin films

An experimental method for preparing a homogenous mixture of Silicon Carbide by a small quantity of concentrated sulfuric acid at room temperature was introduced. SiC film exhibits an amorphous state due to acidic treatment that etches the crystalline surface of the film. SiC films were characterized using FTIR, SEM and optical images. SiC films porosity has been observed by SEM images show the morphology of the final composite. Electrical conductivity of thin films have been evaluated by four point probe Hall measurements. The best ratio of 6Si:4C demonstrated the highest conductivity 0.55 μS.cm.

Electrical conductivity of thin films grown by deposition of random clusters of particles

Extensive numerical simulation of the frequency-dependent effective conductivity of porous thin films, grown by deposition of clusters of elementary particles with various shapes and sizes, as well as rodlike particles has been analyzed and reported. The dependence of frequency-dependent effective conductivity $$\sigma _{\text {e}}(s)$$ of films on their morphology has been studied. The conductivity variations versus the size of deposited clusters have been investigated which show a decreasing function behavior. Also, the conductivity depends on the frequency s by a power law whose exponent is non-universal, but depends weakly on the size of the clusters. The non-universality of the exponent is in agreement with the experimental data for the electrical conductivity of a wide variety of materials. In order to study the important characteristic of well-connected materials, the direct current conductivity as a function of films’ stationary porosity has been investigated which shows an essentially linear function. It also grows as a power law with the thickness of the film, which is also in agreement with the past experimental data.

ЛЁД 0 В ПРИРОДНОЙ СРЕДЕ. ЭКСПЕРИМЕНТАЛЬНЫЕ ДАННЫЕ И ПРЕДПОЛАГАЕМЫЕ ОБЛАСТИ ЕГО СУЩЕСТВОВАНИЯ

The paper presents the available experimental data on ice 0 and the assumed objects of the cryosphere in which it can exist. This ice is formed from supercooled volumetric water, and it precedes the formation of ices Ih or Ic, at temperatures below −23 °C. This crystalline modification has been recently predicted by computer simulations using methods of molecular dynamics. Ice 0 was then experimentally found by electromagnetic investigation of wetted nanoporous media. Interest in this modification of ice was aroused due to its special physical and chemical characteristics. A singularity of ice 0 is that it is a ferroelectric that has a high static dielectric constant. When ferroelectric ice 0 contacts other dielectrics at their boundaries a thin layer is formed due to the diffusion of electric charges, and its electrical conductivity is higher than that of the contacting media. High electrical conductivity in thin films allows investigating frozen dispersed media containing ice 0 using non-contact electromagnetic measurement methods. As this takes place, it becomes possible to register water freezing processes in objects existing at temperatures of −23 ÷ −100 C using microwave spectroscopy and remote sensing methods. It is assumed that ice 0 is involved in chemical transformations in different objects of the cryosphere – in the atmosphere, and vegetation and soil covers. Its formation in the pores of materials of man-made structures may exert influence on the life-time of mechanisms and structures at low temperatures due to increased electrocorrosion. Ice 0 is assumed to exist on cold planets and their moons. That is why studying the possibility of ice 0 appearing in different objects of the natural environment at negative temperatures is so important for understanding their properties and developing remote sensing methods.

Control electrically conductive of thin films by using subminiature eddy current transducers

The research objective was the development of subminiature eddy-current transducer designed for studying thin films. Timeliness is subject to the need to assess and predict safe operation life of products manufactured using thin films. A review of various methods for thin films studying was made, including the eddy-current method, based on an analysis of the interaction of an external electromagnetic field with the electromagnetic field of eddy currents induced by an energizing winding in an electrically conductive film. A subminiature surface eddy-current transducer of the transformer type was developed. On the basis of eddy-current transducer, a software and hardware complex was developed to control the eddy-current transducer (to generate alternating current of various frequencies, to provide its supply to the eddy-current transducer, to receive a useful signal from transducers to ensure its convenient visualization). The hardware and software complex provided the opportunity to make local studies of the electrical conductivity of non-ferromagnetic thin films by the method of eddy currents. In the course of the study it was possible to develop an algorithm for finding changes in the average amplitude of the output signal, which allows to conclude about the electrical conductivity of the thin film. The study of thin film samples using the developed measuring system is conducted. The results of testing of Al, Ag and Ni films were presented, and the electrical conductivity values of the samples were obtained.

Size Effect in the Electrical Conductivity of Thin Films of Topological Insulator Bi2Se3

The electrical resistivity of thin films of topological insulator (TI) Bi2Se3 10 to 75 nm thick is measured in the temperature range of 4.2 to 300 K. A size effect is observed in the electrical conductivity of the Bi2Se3 films; i.e., there is a linear dependence of a film’s conductivity on its inverse thickness. It is assumed that a similar effect can be observed in other TIs and in systems with nonuniform distributions of current over the cross section of a sample.

Change of the structural organization in the polar elastomer film under the action of electrostatic field

The effect of the electrostatic field on the structural organization of macromolecules of polar elastomers was studied using polychloroprene (PCP) as an example. The impact of the electrostatic field on thin films of polychloroprene in the process of their formation leads to the formation of a supramolecular structure that is different from that in films formed under similar conditions, but in the absence of a field. An analysis of the dielectric relaxation spectra of samples in an electrostatic field shows an increase in order in the arrangement of macromolecules (degree of crystallinity). The results of the evaluation of the increase in the degree of crystallinity of the films studied by the dielectric method are in good agreement with the estimate of this parameter by analyzing the IR spectra. The results obtained give grounds to conclude that there is an increase in orderliness in the arrangement of polar molecules in thin films of elastomers when they are formed and kept in an electrostatic field. Increasing the order in the arrangement of polar macromolecules leads to an increase in electrical conductivity in thin films of such a material. The work substantiates and uses a method for assessing the degree of crystallinity of an elastomer by analyzing the temperature dependence of electrical capacity.

Nonaggregating Doped Polymers Based on Poly(3,4-Propylenedioxythiophene)

Electrical doping of organic semiconductors is critical for their use in electrical devices. However, many high-performance semiconductors exhibit drastically reduced solubilities when doped in solution, making it difficult to deconvolute the roles of doping and morphological changes on their electrical properties. Here, we report the synthesis of a semiconducting polymer based on poly(3,4-propylenedioxythiophene) (ProDOT) substituted with oligo(ethylene glycol) (EG) side chains that is designed to solvate dopant molecules. When doped with F4TCNQ in solution, the polymer P(ProDOT-EG) undergoes efficient charge transfer while remaining soluble with no indication of aggregation. The electrical conductivity of thin films cast from heavily doped solutions is ∼1 S/cm; optical spectroscopy reveals that the doping efficiency is reduced upon formation of the solid film. Diffusion of F4TCNQ from the vapor phase into films of neutral P(ProDOT-EG) yields comparable conductivities to films cast from doped solutions. ...

A focus on polystyrene tacticity in synthesized conductive PEDOT:PSS thin films

Poly(3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) is a transparent conductive material and a good candidate for being employed as substitute for indium tin oxide (ITO) in reducing the production costs of organic solar cells. To enhance the performance of organic devices, an improving in the conductivity of PEDOT:PSS is crucial and using the solvent additive rises the electrical conductivity by the optimization of the film morphology. The studies have only focused on the relationship between the electrical conductivity of thin films and the crystallinity of PEDOT, and it is also found that the high conductivity is observed in the highly crystalline samples. This study focused on the effect of tacticity of PS on the conductivity of PEDOT:PSS films. First, atactic and isotactic polystyrenes were sulfonated and the complexes of PEDOT:PSS were synthesized. The N-methylpyrrolidone (NMP), as a secondary dopant, was then added to the complexes and conductivity enhancement was investigated in various annealing times. The obtained films were characterized by atomic force microscopy, X-ray diffraction, four point probe resistivity measurement system, UV–visible spectroscopy, FT-IR, and cyclic voltammetry. The electrical conductivity of PEDOT:iPSS films synthesized by the isotactic polystyrene was ~ 0.68 S/cm and by adding 5 wt% NMP into PEDOT:PSS solution, the conductivity of the annealed thin layers increased more than 10-folds (~ 7.73 S/cm) at an appropriate temperature.

Electropulsing-Induced Microstructural Changes and Their Effects on Electrical Conductivity of Thin Films of an Al-doped ZnO

Electropulsing-induced phase decompositions and microstructural changes in AZO-5 thin films were studied by X-ray diffraction, scanning electron microscopy, atomic force microscopy, Hall effect measurement and photoluminescence (PL) measurement techniques. It was found that the electropulsing induced phase decomposition started with spinodal decomposition, which was accompanied by discontinuous precipitation in the AZO-5 thin films. Both circular phase decompositions and the crystal orientation occurred. Inappropriate electropulsing might damage zones, which resulted in tremendous decrease in electrical conductivity. Circular changes in both the peak position and the width of the PL wavelength were observed in the EPT AZO-5 thin films. Formation of zones favored reducing the roughness of the thin film.

Application of an eddy-current method to measure electrical conductivity of thin films

The research objective was the development of subminiature eddy-current transducer(ECT) designed for studying thin films. The possibility of studying the electrical conductivity of thin films of metals as per the amplitude of the eddy-current transducer signal. A subminiature surface eddy-current transducer of the transformer type was developed, and the optimum shape and size of the core and number of inductance coils and turns in them were defined, this provides efficient localization of electromagnetic field. On the basis of eddy-current transducer, a software and hardware complex was developed to control the eddy-current transducer (to generate alternating current of various frequencies, to provide its supply to the eddy-current transducer, to receive a useful signal from transducers to ensure its convenient visualization). The signal working frequency on the energizing winding of the eddy-current transducer was 3 MHz, the signal working amplitude on the energizing winding was 1.1 V. The hardware and software signal processing made it possible to significantly improve the accuracy of measurements. In the developed system, the parameter with information about the monitoring object is the averaged amplitude of the voltage applied by the eddy currents into the measuring winding of the ECT. The algorithm to determine the averaged signal amplitude is given. The dependence between the averaged amplitude of the eddy-current transducer signal and the electrical conductivity of thin films was analyzed and studied. The results of testing of Al, Cu and Zn films were presented, and the electrical conductivity values of the samples were obtained.

Simultaneous stoichiometric composition and highly (00l) orientation of flexible Bi2Te3thin films via optimising the DC magnetron sputter-deposition process

Simultaneous stoichiometric composition and highly (00l) orientation of flexible Bi2Te3 thin films were investigated under the DC magnetron sputtering parameters. Stoichiometric Bi2Te3 and highly (00l) orientation structure was obtained by sputtering conditions, preheat temperature at 350 °C, and working pressure of 1.8 × 10−3 mbar. This designed structure of layered compact feature with stoichiometry provide the relatively high mobility. The maximum carrier mobility of 118 cm2/V was observed for highly (00l) film. The electrical conductivity of thin film has been greatly enhanced, to a maximum of about 14.90 × 103 S/cm at 50 °C. This value is higher than those of hot-pressed or spark plasma sintering n-type Bi2Te3 bulk alloys. The maximum power factor of 12.5 × 10−3 W/m.K2 was obtained at 300 °C.

Thermoelectric Properties of Poly(3-hexylthiophene) (P3HT) Doped with 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) by Vapor-Phase Infiltration

Doping of thin films of semiconducting polymers provides control of their electrical conductivity and thermopower. The electrical conductivity of semiconducting polymers rises nonlinearly with the carrier concentration, and there is a lack of understanding of the detailed factors that lead to this behavior. We report a study of the morphological effects of doping on the electrical conductivity of poly(3-hexylthiophene) (P3HT) thin films doped with small molecule 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ). Resonant soft X-ray scattering shows that the morphology of films of P3HT is not strongly changed by infiltration of F4TCNQ from the vapor phase. We show that the local ordering of P3HT, the texture and form factor of crystallites, and the long-range connectivity of crystalline domains contribute to the electrical conductivity in thin films. The thermopower of films of P3HT doped with F4TCNQ from the vapor phase is not strongly enhanced relative to films doped from solution, but the el...