Electrical Conductivity Of Thin Films Research Articles

The Effect of Ba/Sr Ratio on Electrical and Optical Properties of BaxSr(1-x)TiO3 (x = 0.25; 0.35; 0.45; 0.55) Thin Film Semiconductor

Ferroelectric BaxSr(1-x)TiO3 thin film semiconductors with Ba/Sr ratio deposited on silicon using chemical solution deposition (CSD) method have been investigated, followed by annealing at 850°C for 15 hours. Observations by I-V meter, LCR meter, and oscilloscope were employed to characterize the electrical properties of the thin films and the observation of fourier transform spectroscopy (FTIR) and particle size analyzer (PSA) to characterize the optical properties. The results showed that the dielectric constant was given around 2–18. Moreover the obtained films were found to be resistor because the I-V graph of each sample was ohmic either in dark or bright environment. The increase of BST mol fraction at dark environment is proportional to the increase of the curve slope. While at bright environment gives the highest curve slope for BST with fraction x = 0.45. Based on electrical conductivity of thin films, we conclude that the thin films are semiconductor. Moreover, functional group and particle size of sample were analyzed using FTIR and PSA analyzer. The augmentation of Ba would decrease the transmittance band of OH− and increase the transmittance band of C-O because the radius of Ba is higher than Sr. The particle distribution size of BST 0.45 is 134.93 nm smaller than BST 0.25 which gives 186.26 nm, BST 0.35 gives value of 467.86 nm and BST 0.55 is 407.49 nm.

Responsive Gels with the Polymer Containing Alternating Naphthalene Diimide and Fluorinated Alkyl Chains: Gel Formation and Responsiveness as Well as Electrical Conductivity of Polymer Thin Films

AbstractA new electroactive polymer 1 with alternating NDI (naphthalene diimide) moieties and fluorinated alkyl chains was prepared and characterized. Gels of polymer 1 were formed in several solvents. Interestingly, gels of polymer 1 exhibited responsiveness toward N2H4, F− and CN−. Absorption and ESR spectroscopic studies revealed that such responsiveness is owing to the reduction of NDI moieties into the respective NDI.−. In addition, thin films of polymer 1 were easily prepared with spin‐coating technique and the electrical conductivity of thin films reached 52.4 S/m after exposure to N2H4 vapor.

Optical and Electrical Properties of Inner Tubes in Outer Wall-Selectively Functionalized Double-Wall Carbon Nanotubes

Atom-thick materials such as single-wall carbon nanotubes (SWNTs) and graphene are prone to chemical attacks because all constituent atoms are exposed. Here we report the retention of optical and electrical properties of inner tubes in heavily functionalized double-wall carbon nanotubes (DWNTs). Correlated optical absorption spectroscopy, Raman scattering, and thin film electrical conductivity all suggest that an inner tube behaves strikingly similar to a pristine SWNT; however, because of the protection of the outer wall, the inner tube can survive aggressive chemical attacks (e.g., by diazonium chemistry) without compromising physical properties. At the saturation limit of the diazonium functionalization, an SWNT network becomes electrically insulating; in stark contrast, the double-walled structure retains ∼50% of the initial conductivity, owing to the intact inner tube pathway. These results suggest the possibility of high-performance DWNT electronic devices with important capabilities for tailored su...

Correlation of the morphology and electrical conductivity in thin films of PEDT/PSS complex: an integrated meso-scale simulation study

Using an integrated meso-scale simulation methodology, the morphology and electrical conductivity relationship of the poly(ethylene-dioxy)thiophene/poly-styrenesulphonate (PEDT/PSS) complex in the range of PSS/PEDT mass ratios 1.4–20 has been established. The morphology presented as a density field has been generated by dynamic density field theory-based MesoDyn simulation code for all systems taking into account the substrate surface effect. Generated anisotropic morphologies have been characterised by the modified anisotropy parameter Q i and Q Di values indicating the anisotropy along the system diagonals and coordinates, respectively. Based on the hopping mechanism of the conductivity, the values of the percolation-related critical parameter are identified and correlated with the macroscopic in-plane (∥) and out-of-plane ( ⊥ ) electrical conductivities, relative to the substrate surface. These macroscopic conductivities are also calculated accurately by applying the Kirchoff laws to the respective random resistor networks. The results are in a reasonable agreement with the available experimental data.

Synthesis and characterizations of AgSCN nanospheres using AgCl as the precursor

Nanospheres of AgSCN with an average radius of 30–80 nm have been prepared by a simple reaction between AgCl suspension and KSCN in the presence of gelatin. Gelatin played a decisive role as an inhibitor of the direct attack of SCN − ions to AgCl surfaces and coagulation of the growing AgSCN in producing the spherical AgSCN nanoparticles. The products were characterized by X-ray powder diffraction, transmission electron microscopy and X-ray photoelectron spectra techniques. The electrical conductivity of thin films of as-prepared AgSCN nanoparticles and polyethylene oxide (PEO) at room temperature was measured. The maximum value of electrical conductivity of as-prepared AgSCN–PEO was 1.53 × 10 −5 S cm −1.

Volatile organic compounds sensing properties of tetrakis(alkylthio)-substituted lutetium(III) bisphthalocyanines thin films

The effect of volatile organic compounds (VOCs) such as acetone, methanol, ethanol, chloroform, carbon tetrachloride, dichloromethane, and hexane on electrical conductivity of thin films of bis[tetrakis(alkylthio)phthalocyaninato]lutetium(III) double decker complexes [(C n H 2 n+1 S) 4Pc] 2Lu(III) was investigated. The [(C n H 2 n+1 S) 4Pc] 2Lu(III) molecules substituted with different alkylthia chains ( n = 6, 8, 10, 12, and 16) were coated on interdigital transducers using a jet spray technique. A change (increase or decrease) in the conductivity of the [(C n H 2 n+1 S) 4Pc] 2Lu(III) films was observed depending on the concentration of the VOCs, which was ranging from 500 to 5000 ppm. The decrease in the conductivity of the sensors for the dissolvent of the compounds (chloroform, carbon tetrachloride, dichloromethane and hexane) could be related to swelling of the films. On the other hand, the increase in the conductivity of the sensors for the other VOCs (acetone, methanol and ethanol) could be resulted from that the VOCs act as electron donors and/or acceptors in the films. A linear relationship between the sensor response and concentration of the VOC vapors is obtained. The sensitivities of the [(C n H 2 n+1 S) 4Pc] 2Lu(III) films were in the range of 2.10 −4–3.10 −3%/ppm.

The influence of surface roughness on electrical conductance of thin Cu films: An ab initio study

First-principles calculations show that atomic-scale surface roughness dramatically affects the electrical conductivity of thin films. Atomic clusters, 1–3 atoms high, deposited on the flat Cu(001) surface of an 11 monolayer thick film lead to a 30−40% reduction of its conductance. This is attributed to the destruction of isotropic Fermi surface sheets. We provide a simple parametrized formula, correlating the size of the surface added structures to the film conductance, and also demonstrate that Ta and Al surface monolayers on rough Cu surfaces cause a conductance decrease and increase, respectively.

Cr-inserted TiO2 thin films for chemical gas sensors

Cr–Ti oxide thin films were prepared by rf sputtering of Cr-inserted Ti targets. The roles played by Cr content and thermal treatments on both the structure and the electrical conductivity of thin films were investigated. Selected series of samples were tested as sensors for different gases like carbon monoxide and ethanol. In both the cases, samples exhibiting the best sensing performances were determined and possible correlations between structure and electrical properties were evidenced.

Measurements and modeling of the DC temperature dependence of electrical conductivity in thin films of lead phthalocyanine

Many of the phthalocyanines exhibit p-type conductivity, and electrical conductivity through thin films of these materials having ohmic contacts show space-charge-limited conductivity (SCLC) dominated by trap levels located within the band gap. In the present work evaporated thin films of lead phthalocyanine with ohmic gold electrodes were prepared, which showed two distinct regions in the dependence of current density J on applied voltage V. At low voltages sample conductivity was ohmic, changing at higher voltages to a square-law dependence of J on V, which is indicative of SCLC dominated by trap levels located at a single discrete energy level. The results of temperature measurements indicate three distinct regions, in each of which the hole concentrations are controlled by different activation energies. A simple model is proposed in which a single trap level is located at the same energy spacing E t from the valence band edge as a single acceptor level. This predicts three different temperature ranges, two of which correspond to those covered by the experimental results. The experimental results indicate a trap level located at an energy E t = 0.36 eV above the valence band edge and a thermal band gap E g = 1.51 eV. Using the proposed model together with data from the experimental J–V characteristics, an acceptor concentration of 4.85 × 10 19 m − 3 and a trap concentration of 5.18 × 10 25 m − 3 are indicated. Measurements of mobility based on this model yield a value of 2.6 × 10 − 4 m 2 V − 1 s − 1 , which is in close agreement with previous work.

Ligands of biologically active compounds in the nanochemistry of silver and gold (A review)

Examples of the interactions of gold and silver clusters with various organic compounds containing olefinic and carbonyl groups capable of acting as ligands for the formation of coordination compounds with these metals are considered. Common physicochemical properties of the coordination complexes of silver ions with olefins are described. The behavior of olefins as ligands of the coordination complexes with silver ions in liquid chromatographic systems is analyzed. There is a correlation between the lipophilicity of such organic molecules and the possible variations of the coordination numbers of metal atoms, as well as between the degree of unsaturation of olefin chains in these molecules and the electrical conductivity of thin films of related lipids (including those of natural origin). Such complexes can be used in nanotechnology for the creation of biocomputer memory cells.

Investigation into the Sensory Properties of Fine-Grain Polycrystalline Films Based on Cobalt, Nickel, and Praseodymium Oxides

The changes in the electrical conductivity of thin films of cobalt, nickel, and praseodymium oxides in air and in media with a high concentration of ozone and argon are investigated. The surface morphology and the initial stages of formation of the films are analyzed. The samples prepared are examined using different physicochemical methods, such as X-ray powder diffraction and differential thermal analyses.

Influence of anomalous roughness growth on the electrical conductivity of thin films

In this work it is explored how anomalies in the dynamic evolution of self-affine interface roughness influence electrical conduction in thin films. For metallic films if the roughness amplitude $w$ increases faster than the correlation length $\ensuremath{\xi}$ with increasing film thickness that leads to higher scattering and thus lower conductivity. The latter still increases with increasing roughness exponent $H$ due to interminiband scattering. The opposite behavior was observed for semiconducting films where only one miniband was occupied, therefore excluding interminiband scattering effects. Therefore, dynamic roughness evolution and interminiband scattering can interact and influence the thickness dependent conductivity of thin films. Indeed for semiconducting films the evolution of the long wavelength roughness parameters $w$ and $\ensuremath{\xi}$ can obscure the smoothing effect due to increment of the roughness exponent $H$ and decrease the conductivity in the case of rapid surface/interface roughening.

Non-linearity in the I?V characteristic of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) due to Joule heating

Deviations from Ohm's law are reported for electrical conduction in thin films of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS). A bridge method is used with two independent currents: a `pump' current flowing through mainly one resistive part and a small `probe' current. Changes in resistance are independent of the probe current, but linearly proportional to the electrical power delivered by the pump current. The change in resistance is interpreted in terms of Joule heating and a constant relating the relative change in resistance to the heat production is extracted: αs=8×10−8 √s cm3/J.

Non-linearity in the I–V characteristic of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) due to Joule heating

Deviations from Ohm's law are reported for electrical conduction in thin films of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS). A bridge method is used with two independent currents: a `pump' current flowing through mainly one resistive part and a small `probe' current. Changes in resistance are independent of the probe current, but linearly proportional to the electrical power delivered by the pump current. The change in resistance is interpreted in terms of Joule heating and a constant relating the relative change in resistance to the heat production is extracted: αs=8×10−8 √s cm3/J.

The effects of solvents on the morphology and sheet resistance in poly(3,4-ethylenedioxythiophene)–polystyrenesulfonic acid (PEDOT–PSS) films

Films of poly(3,4-ethylenedioxythiophene)–polystyrenesulfonic acid (PEDOT–PSS), prepared by coating the aqueous PEDOT–PSS dispersion and by coating a mixture of the PEDOT–PSS dispersion and different solvents, have been studied using four-point probe conductivity measurements, atomic force microscopy and photoelectron spectroscopy. The electrical conductivity of thin films of the second type (further on called PEDOT–PSS–solvents) was increased by a factor of about 600 as compared to films of the first type (further on called PEDOT–PSS–pristine). Morphological and physical changes occur in the polymer film due to the presence of the solvent mixture, the most striking being that the ratio of PEDOT-to-PSS in the surface region of the films is increased by a factor of ∼2–3. This increase of PEDOT at the surface indicates that the thickness of the insulating PSS ‘shell’ that surrounds the conducting PEDOT–PSS grains is reduced. The (partial) reduction of the excess PSS layer that surrounds the conducting PEDOT–PSS grains is proposed to lead to an increased and improved connectivity between such grains in the film and hence a higher conductivity. When PEDOT–PSS–solvents receives a post-coating heat treatment, the increased PEDOT-to-PSS ratio at the surface is maintained or even slightly improved, as is the increase in electrical conductivity, even though spectroscopy show that the solvent molecules are removed. This suggests that screening or doping by the solvents throughout the film are not likely to be the key mechanisms for the improved conductivity and supports our proposed mechanism of improved conductivity through improved connectivity between the conducting grains.

Synthesis by plasma and characterization of bilayer aniline–pyrrole thin films doped with iodine

AbstractThe synthesis by plasma and characterization of aniline–pyrrole bilayer polymers doped in situ with iodine were studied. The objective was to study the electrical conductivity of thin films composed of alternating layers of different polymers. The results indicated that the plasma technique is capable of forming chemically bonded layered polymers with several possible combinations. The electric conductivity was studied during heating–cooling cycles so the dependence of the bilayer polymers on temperature could be observed. The behavior was related with the Arrhenius model, with average activation energies of 0.4 ± 0.1 eV in the heating steps and 0.5 ± 0.1 eV in the cooling steps. The difference in both steps shows the influence of the aniline in the bilayer polymer network because polyaniline presents changes in the structure during heating processes. The bilayer aniline–pyrrole polymers had greater electric conductivity at room temperature than that shown by the separate homopolymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1850–1856, 2002

Conduction models in polyaniline: The effect of temperature on the current–voltage properties of polyaniline over the temperature range 30< T(K)

Electrical conduction in thin films and pellets of polyaniline has been shown by several researchers to be temperature activated. Commercial polyaniline (Pan) obtained from Aldrich (HCl and CSA doped) and chemically synthesized (HCl doped) in our laboratory were used in this present work. The Kivelson, Mott’s variable range hopping and Arrhenius laws were used to model conductivity in Pan. Charge transfer in Pan samples of different forms and dopant type were analyzed over the temperature ranges, 30< T(K)<300 and 300< T(K)<450. For temperatures below 60 K, application of currents in the range 2×10 −3–2×10 −8 A show non-ohmic behavior; however, over the same current range, the current–voltage profile becomes ohmic as temperature rises to 300 K. It has been shown that the charge transfer characteristics of Pan is similar, despite of the type and dopant used. The Montgomery and four-point probe methods were used for DC measurements.

Erratum: Roughness effects on the electrical conductivity of thin films grown in a quasi-layer-by-layer mode [Phys. Rev. B63, 125404 (2001)

Erratum: Roughness effects on the electrical conductivity of thin films grown in a quasi-layer-by-layer mode [Phys. Rev. B<b>63</b>, 125404 (2001)

Roughness effects on the electrical conductivity of thin films grown in a quasi-layer-by-layer mode

We investigate morphology effects on the electrical conductivity on thin semiconducting and metallic films grown in a quasi-layer-by-layer growth mode within the framework of quantum-mechanical electron transport theory. The film growth mode is described by a nonequilibrium Sine–Gordon model that incorporates evaporation/recondensation, surface diffusion, and lattice pinning effects. For semiconducting films, pinning effects manifest themselves as oscillations superimposed on a smoothly increasing conductivity with growth time. For metallic films, quantum size effect oscillations are strongly convoluted with pinning induced oscillations, which dominate the conductivity variations at later stages of growth.

Meyer–Neldel rule in amorphous strontium titanate thin films

In this letter, we report the experimental result indicating that the electrical conductivity in thin films of amorphous strontium titanate (a-STO) is well fit to the Meyer–Neldel (MN) rule over the temperature range 300–470 K. The films were ion-beam sputtered and annealed in two different atmospheres: a vacuum and flowing oxygen. The MN plots for the films show two parallel straight lines depending on the annealing atmosphere, which give the identical MN parameters of about 35 meV with the conductivity prefactors of 9.3×10−10 and 2.3×10−14(Ω cm)−1 for the vacuum- and oxygen- annealed films, respectively.