Showing papers on "Van der Pauw method published in 2010"
TL;DR: In this paper, the electrochemical characteristics of the solid oxide fuel cell (SOFC) cathodes prepared by infiltration of (La 0.85 Sr 0.15 ) 0.9 MnO 3-δ (LSM) nanoparticles into porous Y 0.5 Bi 1.5 O 3 (YSB) backbones were investigated in terms of overpotential, interfacial polarization resistance, and single cell performance.
101 citations
TL;DR: In this article, the thermoelectric properties of lattice-matched AlInN grown by metal organic chemical vapor deposition were measured and analyzed, and the results indicated that lattice matched Al-InN alloy on GaN is an excellent material candidate for thermal application.
Abstract: Thermoelectric properties of lattice-matched AlInN grown by metal organic chemical vapor deposition were measured and analyzed. The n-type Al0.83In0.17N alloy exhibited thermal conductivity of 4.87 W/(m K) measured by 3ω differential method. The Seebeck coefficient of n-Al0.83In0.17N was measured as −6.012×10−4 V/K by thermal gradient method. The sheet resistivity of n-Al0.83In0.17N was measured by using Van der Pauw method, and the electrical conductivity was measured as 2.38×104/(Ω m). The thermoelectric figure of merit (Z∗T) of n-type Al0.83In0.17N was measured as 0.532 at room temperature (T=300 K). The finding indicates lattice-matched AlInN alloy on GaN as excellent material candidate for thermoelectric application.
74 citations
TL;DR: In this article, N-type Bi 2 Te 2.7 Se 0.3 thin films with thickness 800nm have been deposited on glass substrates by flash evaporation method at 473 K.
68 citations
TL;DR: In this paper, thin Permalloy films are grown by dc-magnetron sputtering on heated substrates and by thermal evaporation with subsequent annealing.
Abstract: Permalloy (Ni80Fe20) is broadly used to prepare magnetic nanostructures for high-frequency experiments where the magnetization is either excited by electrical currents or magnetic fields. Detailed knowledge of the material properties is mandatory for thorough understanding its magnetization dynamics. In this work, thin Permalloy films are grown by dc-magnetron sputtering on heated substrates and by thermal evaporation with subsequent annealing. The specific resistance is determined by van der Pauw methods. Point-contact Andreev reflection is employed to determine the spin polarization of the films. The topography is imaged by atomic-force microscopy, and the magnetic microstructure by magnetic-force microscopy. Transmission-electron microscopy and transmission-electron diffraction are performed to determine atomic composition, crystal structure, and morphology. From ferromagnetic resonance absorption spectra the saturation magnetization, the anisotropy, and the Gilbert damping parameter are determined. Co...
57 citations
TL;DR: In this paper, the electrical properties of polypyrrole films electrodeposited in different aqueous electrolyte solutions including p-toluenesulfonate, naphtalenesulfone, nitrate, tetrafluoroborate, and perchlorate anions were investigated using the Van der Pauw procedure.
49 citations
TL;DR: In this article, a simple setup was used to measure the sheet resistances of polypyrrole-coated woven para-aramide fabrics and compared with those obtained using a sophisticated commercial collinear array probe.
Abstract: In this article, it is shown that the Van der Pauw (VDP) method, generally known in microelectronics, can be successfully adapted to sheet resistance measurements of electroconductive fabrics. We prepared two polypyrrole-coated woven para-aramide fabrics and used a simple setup to measure their sheet resistances. The results were then compared with those obtained using a sophisticated commercial collinear array probe. The measurements were done in a 1 month interval, to investigate the influence of the coating aging on the sheet resistance of the samples. The influence of the contact positioning on the accuracy of the VDP measurement was investigated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
45 citations
TL;DR: In this paper, the influence of resin content on ac magnetic properties of Fe-based composite material was investigated to extend possibilities for application of this kind of material at higher frequency and the dc hysteresis loops were measured by a fluxmeter-based hystresisgraph, and the values of the specific resistivity measured by the van der Pauw method were used for calculation of eddy current losses.
Abstract: We investigated the influence of resin content on ac magnetic properties of Fe-based composite material to extend possibilities for application of this kind of material at higher frequency. The samples of composite material with different content of phenol-formaldehyde resin acting as insulator were prepared by conventional powder metallurgy. The samples in the form of the ring were used for ac magnetic measurements and in the form of cylinder for specific resistivity measurements. The ac magnetic properties (sample in the form of ring) were measured at maximum flux density up to 0.4 T by MATS-2010SA loop tracer in a frequency range 1-150 kHz and obtained total power losses. The dc hysteresis loops were measured by a fluxmeter-based hysteresisgraph. The values of the specific resistivity measured by the van der Pauw method (sample in the form of cylinder) were used for calculation of eddy current losses. All magnetic properties of the composite rings were compared with the properties of the material prepared from the powder provided by Hoganas AB Sweden by the technology usually used by the producer.
41 citations
TL;DR: The influence of intermixing heterogeneous regions that have different electrical properties from the base materials on van der Pauw measurement values was theoretically studied by computer simulation using the finite-element method as mentioned in this paper.
Abstract: The influence of intermixing heterogeneous regions that have different electrical properties from the base materials on van der Pauw measurement values was theoretically studied by computer simulation using the finite-element method. The measurement samples selected were thin films of inhomogeneous semiconductors. Calculated electrical properties, such as resistivity, carrier density, and mobility of the thin films, varied in predictable ways when heterogeneous regions were dispersed in wide ranges over the samples. On the other hand, the mobility of the thin films showed a different change when heterogeneous regions were locally concentrated in the measurement samples.
39 citations
TL;DR: In this article, thermal evaporation technique was employed to deposit pristine and iodine doped polyaniline (PANI) thin films on glass substrates, which were characterized by FTIR and UV-VIS spectroscopy.
37 citations
TL;DR: In this article, an experimental investigation of the influence of an AlN interlayer on the electron mobility and the device characteristics of N-polar AlGaN/GaN metal-insulator-semiconductor-high electron mobility transistors grown by metal-organic chemical vapor deposition on miscut sapphire substrates is presented.
Abstract: This paper presents an experimental investigation of the influence of an AlN interlayer on the electron mobility and the device characteristics of N-polar AlGaN/GaN metal-insulator-semiconductor-high electron mobility transistors grown by metal-organic chemical vapor deposition on miscut sapphire substrates. Use of miscut substrates leads to the formation of multiatomic steps at the AlGaN/GaN interface and anisotropy in electron transport properties. A combination of van der Pauw Hall, gated transfer length measurements, and capacitance-voltage measurements has been used to study the desired properties in directions parallel and perpendicular to the multiatomic steps and qualitative explanations were provided for the observed trends. Similar to the Ga-polar devices, the introduction of AlN interlayer improved the device performance by increasing both the electron mobility and the two-dimensional electron gas charge density in the devices. Orienting the devices such that the conduction occurred parallel to the multiatomic steps was beneficial for better electron transport and device performance.
29 citations
TL;DR: In this article, a new electrically conducting nanosized Ag-PANI-silica complex was synthesized by using γ-irradiation at room temperature and not by using polyvinylpyrrolidone (PVP) as a colloidal stabilizer.
TL;DR: In this paper, N-polar metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs) were fabricated from a GaN/AlN/InAl N/GaN heterostructure grown by metalorganic chemical vapor deposition on a vicinal sapphire substrate.
Abstract: N-polar metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs) were fabricated from a GaN/AlN/InAlN/GaN heterostructure grown by metalorganic chemical vapor deposition on a vicinal sapphire substrate, using Si3N4 as the gate insulator. Hall measurements in van der Pauw geometry on the heterostructure showed a sheet charge density and a mobility of 2.15 × 1013 cm-2 and 1135 cm2·V-1·s-1, respectively. Resistance measurements revealed anisotropic conductivity with respect to the surface steps induced by the substrate misorientation, and the sheet resistance of the 2-D electron gas was as low as 226 Ω/□ in the parallel direction. MIS-HEMTs with a gate length of 0.7 μm and a source-drain spacing of 2.2 μm had a peak drain current of 1.47 A/mm and an on-resistance of 1.45 Ω·mm. At a drain bias of 8 V, the current- and power-gain cutoff frequencies were 14 and 25 GHz, respectively.
TL;DR: A series of CoFe/Cu multilayers were electrodeposited on Ti substrates from the electrolytes containing their metal ion under potentiostatic control and exhibited giant magnetoresistance (GMR) and the GMR values up to 8% were obtained.
Abstract: A series of CoFe/Cu multilayers were electrodeposited on Ti substrates from the electrolytes containing their metal ion under potentiostatic control, but the Fe concentration in the electrolytes was changed from 0.0125 M to 0.2 M. The deposition was carried out in a three-electrode cell at room temperature. The deposition of Cu layers was made at a cathode potential of -0.3 V with respect to saturated calomel electrode (SCE), while the ferromagnetic CoFe layers were deposited at -1.5 V versus SCE. The structural studies by X-ray diffraction revealed that the multilayers have face-centered-cubic structure. The magnetic characteristics of the films were investigated using a vibrating sample magnetometer and their easy-axis was found to be in film plane. Magnetoresistance measurements were carried out using the Van der Pauw method at room temperature with magnetic fields up to +/- 12 kOe. All multilayers exhibited giant magnetoresistance (GMR) and the GMR values up to 8% were obtained.
TL;DR: In this article, double donor codoping was applied to germanium substrates and the dopant profiles with a quadratic dependence of the dopants diffusion coefficient on the free electron concentration were obtained by secondary ion mass spectroscopy.
Abstract: We report arsenic and phosphorus diffusion experiments and activation related phenomena in codoped germanium substrates utilizing conventional thermal annealing. Chemical profiles were obtained by secondary ion mass spectroscopy, sheet resistance was estimated by the Van der Pauw method. Our study covers the temperature range from 600 to 750 °C. We accurately described the dopant profiles with a quadratic dependence of the dopants diffusion coefficient on the free electron concentration. In our simulations we considered the dopant pile-up near the surface and dopant loss owing to outdiffusion during the annealing. Although the double donor codoping technique exhibited no advantage over monodoping with P concerning the level of activation and junction depth, it was interesting to observe the different diffusion behavior of the two dopants. Whereas the diffusion of As indicates a retardation under codoping the diffusion of P remains either unaffected or is slightly enhanced by codoping. The activation level of the codoped samples remains lower compared to the respective monodoped samples, except for the highest annealing temperature.
TL;DR: AlxIn1-xN films were grown on (0001) sapphire substrates by reactive radiofrequency (RF) magnetron sputtering in an ambient of Ar and N2 as discussed by the authors.
Abstract: AlxIn1–xN films were grown on (0001) sapphire substrates by reactive radiofrequency (RF) magnetron sputtering in an ambient of Ar and N2. The XRD patterns are shown from AlxIn1–xN films grown on AlN/sapphire substrates using a wide range of magnetron power ratio settings. The wurtzite structure films have high crystal quality with full-width at half-maximum (FWHM) in the range of 0.22°–0.52°. The surface morphologies were observed by scanning electron microscopy (SEM). Raman spectra were measured on the AlxIn1–xN surfaces in a backscattering configuration at room temperature with 532 nm laser excitation and show A1(LO) bimodal behavior. Electrical resistivity and electron mobility were measured by the Hall effect method in the conventional Van der Pauw geometry at room temperature. The lowest electrical resistivity is 1 × 10−3 Ω·cm. This work suggests that reactive magnetron sputtering is a promising method for growing AlxIn1–xN films in over a large composition range.
TL;DR: In this article, the effect of contact placement error induced by pressure on the resistivity measurement accuracy of van der Pauw method was studied using finite element analysis, and the results showed the contact placement has a significant effect on determination accuracy.
Abstract: The van der Pauw technique is widely used to determine resistivity of materials. In diamond anvil cell the compressed sample will make the contact placement change under high pressure. Using finite element analysis, we study the effect of contact placement error induced by pressure on the resistivity measurement accuracy of van der Pauw method. The results show the contact placement has a significant effect on determination accuracy. This method can provide accurate determination of sample resistivity when the spacing b between the contact center and sample periphery is less than D/9 (sample diameter). And the effect of contact placement error on accuracy rapidly increases as the contact location is closing to the sample center. For the same contact placement, the contact size error has a more obvious effect on the semiconductor sample.
TL;DR: In this article, the performance of n-GaN/AlGaN, Al 2 O 3 gate oxide was demonstrated using the low temperature liquid phase deposition technique for high electron mobility transistors.
Abstract: The performance of n-GaN/AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors (MOSHEMTs) with a 20 nm thick Al 2 O 3 gate oxide deposited using the low temperature liquid phase deposition technique is demonstrated. MOSHEMTs exhibit a 23% increase in saturation drain current density, 13% higher extrinsic transconductance, and a lower gate leakage current of 3 orders of magnitude in comparison with high electron mobility transistors. The stability and the interface quality of Al 2 O 3 /n-GaN by this alternative process are discussed. The sheet carrier concentration and Hall mobility are also estimated from the channel conductance under the gate, which is comparable with those measured by the van der Pauw method before the device processing.
TL;DR: Van der Pauw's method as discussed by the authors enables the sheet resistance Rsq and the Hall mobility μH to be extracted from arbitrarily shaped simply connected planar samples with four peripheral pointlike contacts.
Abstract: Van der Pauw's method enables the sheet resistance Rsq and the Hall mobility μH to be extracted from arbitrarily shaped simply connected planar samples with four peripheral pointlike contacts. This paper generalizes the method for devices with extended contacts. It is found that Rsq and μH can be extracted using only six resistance measurements in the absence of a magnetic field and a single magnetic sensitivity measurement. Conversely, if the μH of a simply connected planar conducting device with peripheral contacts is known, the magnetic sensitivity of the device can be predicted based on six resistance measurements in the absence of a magnetic field, without any further knowledge of the device geometry. The new method is applied to a variety of differently shaped diffused silicon n-wells with peripheral contacts. The extracted sheet resistance and Hall mobility values show excellent consistency and are in agreement with the fabrication specifications.
01 Jun 2010-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, the relation between low resistivity and Zn interstitial in ZnO single crystals implanted with the peak Si atomic concentration of 2.62 × 10 20 cm −3 is studied by combining Rutherford backscattering spectroscopy/channeling, photoluminescence, and Van der Pauw methods.
Abstract: The relation between low resistivity and Zn interstitial in ZnO single crystals implanted with the peak Si atomic concentration of 2.62 × 10 20 cm −3 is studied by combining Rutherford backscattering spectroscopy/channeling, photoluminescence, and Van der Pauw methods. The variation in resistivity from ∼10 4 Ω cm for un-implanted ZnO to ∼10 −3 Ω cm for as-implanted ones is observed. The lattice displacement of Zn atoms of ∼0.10 A from the 〈0 0 0 1〉 row is estimated from the normalized angular yield profiles, preserving the single crystallinity in as-implanted ZnO with a minimum yield ( χ min ) of ∼11%. The low resistance is maintained by the 1000 °C annealing, accompanied with the lattice displacement of Zn atoms of ∼0.07 A. These results suggest the existence of the shallow donor consisting of Zn interstitial and/or Zn interstitial-related complex corresponding to a newly appeared 3.33 eV-emission located at ∼40 meV from the bottom of the conduction band.
TL;DR: In this article, polycrystalline thin films of RuO2 were grown on fused-quartz substrates and a parametric study was carried out to probe the influence of film nanostructure on the four-point Van der Pauw resistivity and Hall coefficient.
Abstract: Polycrystalline thin films of RuO2 were grown on fused-quartz substrates and a parametric study was carried out to probe the influence of film nanostructure on the four-point Van der Pauw resistivity and Hall coefficient. The films were grown via reactive rf magnetron sputtering of a Ru target in an Ar∕O2 plasma using deposition rates from 0.27to3.5A∕s and substrate temperatures from 16to500°C. Room-temperature resistivities of the RuO2 films ranged from 58to360μΩcm. Upon first heating following deposition, some films showed decreasing resistivity with increasing temperature, but the resistivities also decreased upon subsequent cooling suggesting that the annealing treatment reduces the film defect density. The temperature coefficient of resistance was found to be small (<0.001K−1) in agreement with previous investigations. Hall coefficient measurements of the polycrystalline thin films demonstrated that either n-type or p-type majority carriers can be present depending on deposition conditions and the re...
TL;DR: In this paper, a procedure to dope n-type Cr 2 − ǫ-x Ti x O 3 thin films is proposed, which consists on the deposition of 10nm Ti and 50nm Au, followed by thermal annealing at 1000°C for 20min in N 2 atmosphere.
01 Oct 2010
TL;DR: In this article, high quality (0,0,2) zinc oxide thin films were grown on (1 − 0) silicon substrates by pulsed laser deposition (PLD), and four-point Van Der Pauw Hall effect measurements were performed to evaluate the electrical conduction in the films.
Abstract: Undoped high quality (0 0 2) zinc oxide thin films were grown on (1 0 0) silicon substrates by pulsed laser deposition (PLD). The films were developed at low growth temperatures between 200 and 300 °C, and a range of oxygen pressures from 8.5 × 10−5 to 2.6 × 10−4 Torr. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and room temperature photoluminescence (PL) have been carried out in order to verify the formation of ZnO layers and evaluate the structural and optical properties of the grown layers. Four-point Van Der Pauw Hall effect measurements were performed to evaluate the electrical conduction in the films. The grown ZnO films on Si were found to be perfectly (0 0 2) aligned polycrystalline structures with a best full-width at half-maximum (FWHM) value of 0.24° obtained for the optimum growth conditions. The PL study showed high optical quality with a substantially suppressed defect related emission band for the optimized conditions. Hall effect measurements showed that samples prepared at oxygen pressures of 1.0 × 10−4 Torr and above had p-type conductivity at room temperature, whereas samples grown at lower pressures were n-type. All samples showed n-type conductivity at low temperature (77 K) regardless of the growth conditions, which suggests a thermal competition between donor-like oxygen vacancies and/or oxygen vacancy complexes with hydrogen, and acceptor-like oxygen interstitials and possibly Zn vacancies.
TL;DR: In this paper, B-doped homoepitaxialy grown diamond is characterized with and without mesa structures by Hall effect measurements as function of temperature in the as-grown state and following oxygen reactive ion etching (RIE).
Abstract: Electrical properties of B-doped homoepitaxialy grown diamond are characterized with and without mesa structures by Hall effect measurements as function of temperature in the as-grown state and following oxygen reactive ion etching (RIE). The extracted carrier type, concentration, and mobility are found to depend on the measurement contact configuration. For measurements performed without mesa major differences, even in carrier type, are found following the RIE treatment, however no changes what so ever are observed when measuring with a mesa structure. Finite element simulation confirms that carrier concentration or/and mobility inhomogeneities in the regions surrounding the contacts in Hall effect measurements using the Van der Pauw configuration can result in wrong assignments of carrier type, concentration and mobility.
TL;DR: In this paper, the authors used Van der Pauw method to analyze the structural and electrical properties of polycrystalline ZnO thin films with thickness d = 100nm.
TL;DR: In this article, p-type ZnO thin films have been reported by depositing it on semi insulating GaAs substrates by Pulsed Laser Deposition (PLD) technique.
TL;DR: In this article, the authors compared the ionic conductivity of single-crystal GDC films and poly-crystalline GDC thin films, showing that the single crystal film exhibits a lower activation energy for ionic conduction of 0.85 − 0.01 − 1/eV than the 0.99 − 0.01 − 2 /eV observed in the poly-Crystal film.
TL;DR: In this paper, structural and electrical characterization of palladium oxide (PdO) films grown by thermal oxidation of nanometric Pd films was reported. But the PdO films were not shown to be p-type with a hole concentration of 10 20 cm −3 and mobility in the range of 2-32 cm 2 /V
Abstract: Structural and electrical characterization of palladium oxide (PdO) films grown by thermal oxidation of nanometric Pd films is reported. Pd films were deposited on n-type silicon (1 1 1) substrates by the electroless deposition technique (EDT) in a PdCl 2 –HF aqueous solution. The growth rate and the structural properties of PdO films were characterized using X-ray diffraction and Raman spectroscopy techniques. The electrical properties of the PdO films were measured by the van der Pauw method. The PdO films resulted p-type with a hole concentration of 10 20 cm −3 and mobility in the range of 2–32 cm 2 /V s.
01 Nov 2010-Microsystem Technologies-micro-and Nanosystems-information Storage and Processing Systems
TL;DR: In this paper, the effect of relative size and misalignment of the VDP sensor on the sensitivity is investigated using a coupled piezoresistive/stress finite element model, where the mode is developed to simulate the full field stress over the deformed diaphragm in which the van der Pauw (VDP) is diffused.
Abstract: This paper characterizes a piezoresistive sensor under variations of both size and orientation with respect to the silicon crystal lattice for its application to MEMS pressure sensing The sensor to be studied is a four-terminal piezoresistive sensor commonly referred to as a van der Pauw (VDP) structure It is observed that the sensitivity of the VDP sensor is over three times higher than the conventional filament type Wheatstone bridge resistor With MEMS devices being used in applications which continually necessitate smaller size, characterizing the effect of size and orientation of a VDP structure on the performance of a MEMS pressure sensor is important In this paper, the effect of relative size and misalignment of the VDP sensor on the sensitivity is investigated using a coupled piezoresistive/stress finite element model The mode is developed to simulate the full field stress over the deformed diaphragm in which the VDP is diffused The change in resistivity of the VDP is then analyzed to predict the sensitivity of the VDP structure Sensor size, position relative to the diaphragm, and angular misalignment of the VDP were varied to determine a theoretical result for the dependence of VDP output on those parameters It is determined that the performance of the sensor is strongly dependent only on the longitudinal position of the sensor on the diaphragm, and is relatively tolerant of other errors in the manufacturing process such as transverse position, sensor depth, and orientation angle
TL;DR: In this paper, a Van der Pauw Hall measurement is performed on intended doped ZnO films (Na doped znO) grown by using the molecular beam epitaxial method.
Abstract: A Van der Pauw Hall measurement is performed on the intended doped ZnO films (Na doped ZnO) grown by using the molecular beam epitaxial method. All as-grown samples show n-type conductivity, whereas the annealed samples (annealing temperature 900° C) show ambiguous carrier conductivity type (n- and p-type) in the automatic Van der Pauw Hall measurement. A similar result has been observed in Li doped ZnO and in as-doped ZnO films by other groups before. However, by tracing the Hall voltage in the Van der Pauw Hall measurement, it is found that this alternative appearance of both n- and p-type conductivity is not intrinsic behavior of the intended doped ZnO films, but is due to the persistent photoconductivity effect in ZnO. The persistent photoconductivity effect would strongly affect the accurate determination of the carrier conductivity type of a highly resistive intended doped ZnO sample.
01 Oct 2010
TL;DR: In this paper, the authors investigated a new method of growing detector grade large GaTe layered chalcogenide single crystals using graphite crucible by slow crystallization from a melt of high purity (7N) Ga and Te precursors in an argon atmosphere.
Abstract: In this work we investigated a new method of growing detector grade large GaTe layered chalcogenide single crystals. GaTe ingots (2″ diameter) were grown by a novel method using graphite crucible by slow crystallization from a melt of high purity (7N) Ga and Te precursors in an argon atmosphere. GaTe samples from the monocrystalline area of the ingot have been cleaved mechanically and characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis by x-rays (EDAX), atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS), transmission line matrix method (TLM), resistivity measurements using van der Pauw technique, Hall Effect, and Capacitance-Voltage measurements. Our investigations reveal high potential for developing superior quality GaTe crystals using this growth technique for growing large volume inexpensive GaTe single crystals for nuclear radiation detectors.