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Showing papers on "Van der Pauw method published in 2013"


Journal ArticleDOI
TL;DR: In this paper, the authors used Hall effect measurements based on the Van der Pauw method to perform single-base sequence selective detection of DNA on graphene sheets, which are prepared by chemical vapor deposition.
Abstract: There is broad interest in using graphene or graphene oxide sheets as a transducer for label-free and selective electrical detection of biomolecules such as DNA. However, it is still not well explored how the DNA molecules interact with and influence the properties of graphene during the detection. Here, Hall effect measurements based on the Van der Pauw method are used to perform single-base sequence selective detection of DNA on graphene sheets, which are prepared by chemical vapor deposition. The sheet resistance increases and the mobility decreases with the addition of either complementary or one-base mismatched DNA to the graphene device. The hole carrier concentration of the graphene devices increases significantly with the addition of complementary DNA but it is less affected by the one-base mismatched DNA. It is concluded that the increase in hole carrier density, indicating p-doping to graphene, is better correlated with the DNA hybridization compared to the commonly used parameters such as conductivity change. The different electrical observations of p-doping from Hall effect measurements and n-doping from electrolyte-gated transistors can be explained by the characteristic morphology of partially hybridized DNA on graphene and the mismatch between DNA chain length and Debye length in electrolytes.

117 citations


Journal ArticleDOI
TL;DR: In this article, the effects of cobalt dopant on the crystalline structure and orientation of nanostructure ZnO films were investigated using X-ray diffraction (XRD) study.

96 citations


Journal ArticleDOI
TL;DR: In this article, the electrical characterization and Raman spectroscopy of chemical vapor deposition copper-grown graphene transferred onto a Si/SiO2 substrate by high-speed (1 mm/s) electrochemical delamination were reported.
Abstract: We report on the electrical characterization and Raman spectroscopy of chemical vapor deposition copper-grown graphene transferred onto a Si/SiO2 substrate by high-speed (1 mm/s) electrochemical delamination. We determine graphene’s sheet resistance, carrier mobility, and concentration as well as its physical quality as a function of the electolyte concentration. Graphene’s electrical properties are investigated with standard Hall measurements in van der Pauw geometry and a contactless method that employs a single-post dielectric resonator operating at microwave frequencies. These properties are related to the widely used copper etching technique. The results prove that the high-speed electrochemical delamination provides good-quality graphene within a short time scale.

77 citations


Journal ArticleDOI
TL;DR: In this paper, thin films of Cu2ZnSnS4 (CZTS) were deposited on Pyrex substrates at various temperatures by spray pyrolysis technique from aqueous solution containing an economic stannous chloride (SnCl2) precursor for the tin and the effect of substrate temperature on the structural and opto-electronic properties was investigated.
Abstract: Thin films of Cu2ZnSnS4 (CZTS) were deposited on Pyrex substrates at various temperatures by spray pyrolysis technique from aqueous solution containing an economic stannous chloride (SnCl2) precursor for the tin and the effect of substrate temperature on the structural and opto-electronic properties was investigated. X-ray diffraction patterns and Raman spectroscopy reveal that all the CZTS films exhibited kesterite structure with preferential orientation along the (1 1 2) direction and some secondary phases. Also, they possessed different band gaps, which were found to lie between 1.52 and 1.81 eV, indicating that CZTS compound has absorbing properties favorable for applications in solar cell devices. Van der Pauw technique and Hall effect measurements were used to determine the electrical properties of CZTS films and the resistivity was of about 0.12 Ω cm for film grown at 280 °C.

61 citations


Journal ArticleDOI
TL;DR: In this article, structural properties were determined at room temperature using X-ray powder diffraction and conductivity measurements were performed using the four probe DC and van der Pauw techniques at different temperatures and atmospheres.
Abstract: Samples from across the solid solution series La0.2Sr0.7−xCaxTiO3, were successfully synthesised by solid state reaction. Structural properties were determined at room temperature using X-ray powder diffraction and conductivity measurements were performed using the four probe DC and van der Pauw techniques at different temperatures and atmospheres. On increasing x, the perovskite phase lattice symmetry changes from cubic Pmm to tetragonal I4/mcm at x = 0.05 and tetragonal to orthorhombic Pbnm at x = 0.425. The lattice also shrinks as x increases. Samples showed only a slight 0.3% increase in lattice volume after reduction at 900 °C in 5% H2. On increasing calcium doping, conductivity in reduced samples and equilibrated at 900 °C in 5%H2 increased markedly reaching 27.53 S cm−1 at x = 0.45, but decreased as x increased further.

50 citations


Journal ArticleDOI
TL;DR: In this paper, Ni-TiN nanocomposites have been deposited on Si (100) substrate at Ar:N-2 = 1:1, 1:2 or 1:3 at ambient temperature by reactive co-sputtering of Ti and Ni targets used as RF and DC sources.
Abstract: Thin films of Ni-TiN nanocomposites have been deposited on Si (100) substrate at Ar:N-2 = 1:1, 1:2 or 1:3 at ambient temperature by reactive co-sputtering of Ti and Ni targets used as RF and DC sources, respectively. X-ray diffraction (XRD) studies have shown and as preferred orientations for Ni and TiN, respectively. X-ray photoelectron spectroscopic examination of the films has shown Ti/N to be approximate to 1 for Ar:N-2 = 1:2, and 1 for Ar:N-2 = 1:1 or 1:3, respectively. Scanning and transmission electron microscopic studies have shown that with an increase in Ar:N-2 from 1:1 to 1:3, both porosity content and grain sizes are reduced, while the TiN volume fraction obtained by Rietveld analysis of XRD peaks is increased from 22 to 44%. The magnitude of compressive residual stress in both Ni and TIN phases is found to increase with the decrease in Ar:N-2 ratio. Nanoindentation studies have shown that hardness and elastic moduli of films increase with TiN content closely following the rule of mixtures, whereas the scratch resistance scales with hardness. Furthermore, resistivity measured by Van der Pauw four-point probe method appears to be proportional to the TiN volume fraction. (C) 2013 Elsevier B.V. All rights reserved.

47 citations


Journal ArticleDOI
TL;DR: In this article, single-layer graphene sheets were annealed at various temperatures (TA) under vacuum below 10−3 Torr for 10min and characterized by atomic force microscopy, Raman spectroscopy, x-ray photoelectron spectrograph, and 4-probe van der Pauw method.
Abstract: Single-layer graphene sheets grown on Cu foils by chemical vapor deposition were transferred on 300 nm SiO2/n-type Si wafers and subsequently doped with 10 mM AuCl3 solution. The doped graphene sheets were annealed at various temperatures (TA) under vacuum below 10−3 Torr for 10 min and characterized by atomic force microscopy, Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), and 4-probe van der Pauw method. The XPS studies show that the compositions of Cl and Au3+ ions in doped graphene sheets increase slightly by annealing at 50 °C, but by further increase of TA above 50 °C, they monotonically decrease and become almost negligible at TA = 500 °C. These XPS results are consistent with the corresponding TA-dependent behaviors of the Raman scattering and the sheet resistance, implying that the doping efficiency is maximized at TA = 50 °C and the Cl and Au3+ ions play a major role in the doping/dedoping processes that are very reversible, different from the case of carbon nanotubes. These results...

39 citations


Journal ArticleDOI
TL;DR: In this article, undoped and Co-doped ZnO nanorod films were grown by electrochemical deposition onto p-Si substrates from an aqueous route.

33 citations


Journal ArticleDOI
01 Jan 2013-Vacuum
TL;DR: In this paper, the structural and electrical properties of aluminum-doped zinc oxide (AZO) films were ex situ investigated by the X-ray diffractometer and Hall measurement with the Van der Pauw method, respectively.

33 citations


Journal ArticleDOI
TL;DR: The evaporation technique combined with simultaneous heating of the glass leads to change of the sheet resistance, surface roughness, and optical properties of gold nanostructures.
Abstract: The paper is focused on the preparation and surface characterization of gold coatings and nanostructures deposited on glass substrate. Different approaches for the layer preparation were applied. The gold was deposited on the glass with (i) room temperature, (ii) glass heated to 300°C, and (iii) the room temperature-deposited glass which was consequently annealed to 300°C. The sheet resistance and concentration of free carriers were determined by the van der Pauw method. Surface morphology was characterized using an atomic force microscopy. The optical properties of gold nanostructures were measured by UV–vis spectroscopy. The evaporation technique combined with simultaneous heating of the glass leads to change of the sheet resistance, surface roughness, and optical properties of gold nanostructures. The electrically continuous layers are formed for significantly higher thickness (18 nm), if the substrate is heated during evaporation process. The annealing process influences both the structure and optical properties of gold nanostructures. The elevated temperature of glass during evaporation amplifies the peak of plasmon resonance in the structures, the surface morphology being significantly altered.

32 citations


Journal ArticleDOI
TL;DR: In this article, a tritagonal zinc phosphide (α-Zn3P2) was grown pseudomorphically, by compound-source molecular-beam epitaxy on GaAs(001), and the films grew coherently strained, with epitaxial relationships of Zn_(3)P_(2)(004)

Journal ArticleDOI
TL;DR: In this article, the authors report on the evolution of anisotropic electrical resistivity versus temperature of titanium thin films and measure the components of the conductivity tensor by the van der Pauw method during annealing treatment in air ranging from 298 to 873 K.

Journal ArticleDOI
TL;DR: In this paper, the van der Pauw inequality is used to detect the presence of an isolated hole and contacts located on the same edge, however rigorous proof is not given for any sample.

Journal ArticleDOI
TL;DR: In this paper, the authors describe both in-plane and cross-plane measurement methodologies for thin-film thermoelectric characterization, including the four-probe and van der Pauw methods for electrical conductivity measurement.
Abstract: The key thin film thermoelectric characterization techniques are described. Due to the small dimensions, a careful examination of electrical and thermal paths in the device is necessary. We describe both in-plane and cross-plane measurement methodologies. Sample requirements for four-probe and van der Pauw methods for in-plane electrical conductivity measurement are discussed. The in-plane Seebeck coefficient is characterized under a temperature gradient which generates a voltage. Precise measurements of temperature and voltage at the same location in the sample are very important. For the cross-plane electrical conductivity, the modified transmission line method is evaluated. To eliminate parasitic contact and substrate resistances, several samples with varying thicknesses are required. Two approaches, a DC method and the 3ω method, are described in detail for the cross-plane Seebeck coefficient characterization. Next, we focus on the transient Harman method to directly measure the cross-plane thermoelectric figure of merit of a thin film. The device requirements for reducing parasitic heat losses and current nonuniformity are presented. Thermoreflectance imaging can be used together with transient Harman in order to extract electrical and thermal conductivities and the Seebeck coefficient simultaneously. Finally, Z-meters are described for directly determining the figure of merit and efficiency of a thermoelectric element or module under a large temperature gradient. Recent developments have significantly reduced thermal and electrical parasitics, as well as radiation heat loss in the system, enabling ZT measurement of legs as thin as one hundred microns.

Journal ArticleDOI
TL;DR: The presented paper deals with the transmission of video encoded with H.264/AVC (Advanced Video Coding) video coding standard through wireless local area network (WLAN) using the programming environment OPNET Modeller (OM).
Abstract: This article describes the design, construction and control program of an automatic measuring system (AMS), which was designed for sheet resistance and sheet Hall mobility measurements. The van der Pauw technique and 4-point probe method are used to measure sheet resistance and calculate the specific resistance. Furthermore, the software of the AMS contains graphical subroutines for conversion of resistivity to concentration and mobility. Hall effect and electronic transport measurements are invaluable for understanding and characterization of the physical properties of semiconductors such as Si, GaAs, ZnO, and nanocrystal diamond as well as other electronic and magnetic materials. An important part in production of electronic components and integrated circuits is the diagnostics of basic material parameters. The van der Pauw method is one of the most utilized measurement methods for evaluation of the semiconductor material electrical properties, such as resistivity, carrier density, and mobility [1]. Method can be used to measure samples of arbitrary shape, although several basic sample conditions must be satisfied to obtain accurate measurements. Among them the most important are good homogeneity of the sample, constant thickness of the sample and in ideal case infinitive small point contacts placed at the edges of the samples [2]. Moreover, the quality of contact in terms of good ohmic behavior has to be assured. The van der Pauw method is a common method used for investigation of new prepared thin films to determine their quality. Characterizing the mobility of new materials is essential for semiconductor technology innovations, so making accurate Hall effect measurements will continue to be important [2]. Additional resistivity measurement method, the 4point probe, is also widely used in the semiconductor industry to monitor the production process. Electrical measurements are done on test structures to provide information on the various process steps. For example, resistivity measurements of doped semiconductor structures provide information about the carrier concentration and mobility and are used as feedback for the doping diffusion process [3]. This paper describes an AMS with Hall and the 4point-probe method. Optimum measurement conditions for determination of mobility µ are established for different semiconductor layers and structures. Hall effect is invaluable to understand and characterize the physical properties of semiconductors including materials such as: Si, Ge, GaAs, AlGaAs, ZnO, and others. Transport measurements of Hall effect and magnetoresistance are ideally suited for material research, product development, and quality control [2,45]. 2 THEORY The designed automatic measuring system can be used to determine several material parameters: the Hall voltage (VH), carrier concentration (n), Hall coefficient (H) and the conductivity type (n or p) are all derived from the Hall voltage measurement. To be able to evaluate carrier mobility (µ) it is necessary to measure also the resistivity of the sample (�). Due to the required contact node arrangement shown in Fig. 1, the van der Pauw method is the most frequently used method in the Hall measurement systems to evaluate the sample resistivity.

Journal ArticleDOI
TL;DR: In this article, the sintering of asymmetric CGO bi-layers (thin dense membrane on a porous support; Ce 0.9 Gd 0.1 O 1.95− δ ǫ = CGO) with Co 3 O 4 as sinterding additive has been optimized by combination of two in situ techniques.
Abstract: The sintering of asymmetric CGO bi-layers (thin dense membrane on a porous support; Ce 0.9 Gd 0.1 O 1.95− δ = CGO) with Co 3 O 4 as sintering additive has been optimized by combination of two in situ techniques. Optical dilatometry revealed that bi-layer shape and microstructure are dramatically changing in a narrow temperature range of less than 100 °C. Below 1030 °C, a higher densification rate in the dense membrane layer than in the porous support leads to concave shape, whereas the densification rate of the support is dominant above 1030 °C, leading to convex shape. A flat bi-layer could be prepared at 1030 °C, when shrinkage rates were similar. In situ van der Pauw measurements on tape cast layers during sintering allowed following the conductivity during sintering. A strong increase in conductivity and in activation energy E a for conduction was observed between 900 and 1030 °C indicating an activation of the reactive sintering process and phase transformation of cobalt oxide.

Journal ArticleDOI
TL;DR: In this article, Van der Pauw et al. demonstrated a technique for the measurement of the electron velocity versus electric field on as-grown and H-intercalated graphene.
Abstract: A technique for the measurement of the electron velocity versus electric field is demonstrated on as-grown and H-intercalated graphene. Van der Pauw, coplanar microbridge, and coplanar TLM structures are fabricated in order to assess the carrier mobility, carrier concentration, sheet resistance, and contact resistance of both epi-materials. These measurements are then combined with dynamic IV measurements to extract a velocity-field characteristic. The saturated electron velocity measurements indicate a value of 2.33 x 10(7)cm/s for the as-grown material and 1: 36 x 10(7)cm/s for the H-intercalated material at 300 K. Measurements are taken as a function of temperature from 100K to 325K in order to estimate the optical phonon energy E-so of 4H-SiC by assuming an impurity scattering model. The extracted values of E-so are 97 meV for the as-grown sample and 115 meV for the H-intercalated sample. The H-intercalated result correlates to the anticipated value of 116 meV for 4H-SiC, while the as-grown value is significantly below the expected value. Therefore, we hypothesize that the transport properties of epitaxial graphene on SiC are influenced both by intercalation and by remote phonon scattering with the SiC substrate.

Journal ArticleDOI
TL;DR: In this article, the effects of TiN/Ti and TiO2/Ti double layer coatings, with a metal buffer layer, on the corrosion resistance and electrical properties of Al1050 substrates for using them as bipolar plates in PEMFCs were investigated.

Journal ArticleDOI
TL;DR: In this article, the reactive gas pulsing process (RGPP) was used to deposit tantalum metal/oxide periodic nanometric multilayers using the artful technique, namely, the RGPP.
Abstract: Dc reactive sputtering was used to deposit tantalum metal/oxide periodic nanometric multilayers using the artful technique namely, the reactive gas pulsing process (RGPP). Different pulsing periods were used for each deposition to produce metal-oxide periodic alternations included between 5 and 80 nm. Structure, crystallinity and chemical composition of these films were systematically investigated by Transmission Electron Microscopy (TEM) and Energy-dispersive X-ray (EDX) spectroscopy techniques. Moreover, electrical properties were also studied by the van der Pauw technique.

Journal ArticleDOI
TL;DR: In this paper, the authors discuss the results of Hall effect measurements to examine the electrical properties of the graphene films synthesized by low-temperature microwave plasma chemical vapor deposition and discuss the factors controlling the mobility and how to improve the quality of the graphite films by reducing the number of defects.
Abstract: In this Letter, we discuss the results of Hall effect measurements to examine the electrical properties of the graphene films synthesized by low-temperature microwave plasma chemical vapor deposition. Van der Pauw devices with sizes of 50–100 μm were fabricated, for which we observed p-type conduction and mobility from 10 to 100 cm2/V s. To investigate the mobility dispersion, we performed Raman mapping to quantify the number of defects and the disorder in graphene films. The results suggest that the D-band/G-band intensity ratio is correlated with the mobility. Moreover, we discuss the factors controlling the mobility and how to improve the quality of the graphene films by reducing the number of defects.

01 Jun 2013
TL;DR: In this article, a new approach has been made to determine electroconductive properties of a textile product on the basis of the idea of Van der Pauw method, which is used to determine only two characteristic resistances associated with four electrodes.
Abstract: A new approach has been made to determine electroconductive properties of a textile product on the basis of the idea of Van der Pauw method. This method is used to determine only two characteristic resistances associated with four electrodes. Surface resistivity of the sample is not determined because this technique requires some special conditions. The influence of the contact diameter of electrodes as well as the electrodes arrangement on the resistance value of textile sample has been studied. The results show that in case of selected range of the electrodes diameters, the contact diameters do not affect resistance when constant force is applied. However, the impact of electrodes arrangement on the resistance measurements is found to be noticeable. Anisotropy of electrical properties of the textile sample is also studied.

Journal ArticleDOI
TL;DR: In this paper, exact analytic expressions for the sensitivity of resistive and Hall measurements to local inhomogeneities in a specimen's material properties in the combined linear limit of a weak perturbation over an infinitesimal area in a small magnetic field were derived.
Abstract: We derive exact, analytic expressions for the sensitivity of resistive and Hall measurements to local inhomogeneities in a specimen's material properties in the combined linear limit of a weak perturbation over an infinitesimal area in a small magnetic field. We apply these expressions both to four-point probe measurements on an infinite plane and to symmetric, circular van der Pauw discs, obtaining functions consistent with published results. These new expressions speed up calculation of the sensitivity for a specimen of arbitrary shape to little more than the solution of two Laplace equation boundary-value problems of the order of N3 calculations, rather than N2 problems of total order N5, and in a few cases produces an analytic expression for the sensitivity. These functions provide an intuitive, visual explanation of how, for example, measurements can predict the wrong carrier type in n-type ZnO.

Journal ArticleDOI
TL;DR: A novel automatic multi-channel measurement system that can acquire the temperature coefficient of resistance (TCR) and the I – V characteristics of multi-layer thin films and a highly accurate resistance measurement method for characterizing the multi- layer thin films is developed.

Journal ArticleDOI
TL;DR: In this paper, post-deposition annealing in air of CdS thin films deposited via chemical bath deposition, influences the defects and impurities in the films, which in turn affect the electrical conductivity and optical transparency of the films.

Journal ArticleDOI
TL;DR: In this paper, the authors used a sol-gel route as the cathode material for SOFC, and used methanol and acetyl acetone as solvent and chelating agent, respectively.

Journal Article
TL;DR: In this article, a wave function of two-dimensional electron gas (2DEG) in the channel is analyzed and the authors show that the alloy and interface roughness scattering mechanism plays an important role in reducing the mobility of 2DEG.
Abstract: AlGaN/GaN heterostructures attract attention of many research groups over the last decade because of their superior properties (high mobility and saturation velocity of 2DEG) and strong capability in high frequency/power electronics and sensors applications. One of the factors which reduces the mobility of two-dimensional electron gas (2DEG) is the alloy and interface roughness scattering mechanism occurring at the heterointerface. Mathematical calculations of a wave-function of 2DEG in the channel show that theses two phenomena play an important role, due to the fact that some electrons in 2DEG can migrate into AlGaN barrier and be strongly dissipated. One of the proposed solutions against alloy scattering in the buffer layer is the use of thin AlN spacer at the heterointerface between AlGaN and GaN layers. AlN layer enhances the conduction band offset due to a polarization-induced dipole in the AlN layer, and therefore increases carrier confinement. Several Al 0.18 GaN 0.82 /AlN/GaN heterostructures with different AlN spacer layer thickness were grown by MOVPE method for studies of the Hall mobility and sheet carrier concentration of 2DEG. Hall measurements performed using Van der Pauw shown mobility maximum at nominally 1.3 nm AlN spacer thickness and almost linear dependence of sheet carrier concentration with AlN spacer thickness in the range from 0.7 to 2 nm.

Journal ArticleDOI
TL;DR: In this article, it was proved both theoretically and experimentally that no anisotropy can be detected with the collinear contacts of the four-point probe, and therefore, it was used to measure the anisotropic properties of the electric conductivity.
Abstract: The sheet resistance of electrically conducting screen-printed surfaces can be measured with different techniques such as Van Der Pauw or four-point probe. As electroconductive textile materials show anisotropic behaviour we investigate the possibility of using the four-point probe method to measure the anisotropic properties of the electric conductivity. It was proved both theoretically and experimentally that no anisotropy can be detected with the collinear contacts of the four-point probe.

Journal ArticleDOI
TL;DR: In this article, the effects of laser fluence, the number of shots with the laser, and Sb content on the electrical properties such as resistivity, carrier concentration, and carrier mobility of the Sb-doped epitaxial (001) SnO2 thin films were investigated.
Abstract: Excimer-laser-assisted metal–organic deposition (ELAMOD) was used to prepare Sb-doped epitaxial (001) SnO2 thin films on (001) TiO2 substrates at room temperature. The effects of laser fluence, the number of shots with the laser, and Sb content on the electrical properties such as resistivity, carrier concentration, and carrier mobility of the films were investigated. The resistivity of the Sb-doped epitaxial (001) SnO2 thin film prepared using an ArF laser was lower than that of the film prepared using a KrF laser. The van der Pauw method was used to measure the resistivity, carrier concentration, and carrier mobility of the Sb-doped epitaxial (001) SnO2 thin films in order to determine the effect of Sb content on the electrical resistivity of the films. The lowest resistivity obtained for the Sb-doped epitaxial (001) SnO2 thin films prepared using ELAMOD with the ArF laser and 2 % Sb content was 2.5 × 10−3 Ω cm. The difference between the optimal Sb concentrations and resistivities of the films produced using either ELAMOD or conventional thermal MOD was discussed.

Journal ArticleDOI
TL;DR: In this paper, a pulsed photoacoustic technique was used to investigate the semiconductor-metal transition of thin vanadium pentoxide films (V2O5) under increasing temperature.
Abstract: In this work, the pulsed photoacoustic technique was used to investigate the semiconductor-metal transition of thin vanadium pentoxide films (V2O5) under increasing temperature. The V2O5 thin films were simultaneously deposited by RF magnetron sputtering at room temperature, on corning glass and SnO2:F/glass substrates, in order to compare the photoacoustic response. The elemental and structural analysis of the V2O5 films was performed by Rutherford backscattering spectroscopy and X-ray diffraction. The optical transmission and band gap were determined using UV-Vis spectroscopy. The electrical properties were measured using four-point probe measurements with the Van der Pauw geometry.

Journal ArticleDOI
TL;DR: In this paper, the authors compared two van-der-Pauw-type measurement configurations of resistivity, with respect to the movement of the point-like voltage and current contacts away from the periphery of a thin, square sample.