Showing papers on "Van der Pauw method published in 2001"
TL;DR: In this paper, the amount of spontaneous spin splittings was estimated from low-temperature magnetoresistances in two-dimensional electron gases created at In0.75Ga0.25As/In 0.75Al0.5As heterojunctions under a gate bias.
Abstract: Amounts of spontaneous spin splittings were estimated from low-temperature magnetoresistances in two-dimensional electron gases created at In0.75Ga0.25As/In0.75Al0.25As heterojunctions under a gate bias. Typical sheet electron densities and mobilities in the raw wafers were ∼1.0×1012/cm2 and 2–5×105 cm2/V s at 1.5 K, respectively. A maximum spin-orbit coupling constant αzero of ∼30(×10−12 eV m) was obtained for the van der Pauw sample. In gated Hall-bar samples, a decrease in the αzero value with decreasing gate voltage (Vg) was first confirmed in a normal heterojunction. The main origin for such a large αzero, which is a few times larger than any previously reported, was found to be a structure-dependent so-called interface contribution in the Rashba term.
166 citations
TL;DR: In this article, high-oriented tungsten trioxide thin films have been grown on (0, 1 2 ) r-cut sapphire substrates using reactive rf magnetron sputtering of a target in various oxygen/argon mixtures.
Abstract: Highly oriented tungsten trioxide thin films have been grown on (0 1 2) r-cut sapphire substrates using reactive rf magnetron sputtering of a tungsten metal target in various oxygen/argon mixtures Parameters for growth of stoichiometric tungsten trioxide (WO 3 ) films were determined by X-ray photoelectron spectroscopy (XPS) In situ four-point Van der Pauw conductivity measurements were performed on as-grown films and after post-deposition annealing to study changes in the oxygen vacancy population Reflection high-energy electron diffraction (RHEED) and X-ray diffraction (XRD) indicate that stoichiometric WO 3 films deposited at 450°C are dominated by the tetragonal phase with (0 0 1) orientation along the growth direction, and films deposited at 650°C possess coexisting (0 0 2), (0 2 0), and (2 0 0) in-plane orientations of the monoclinic phase Tetragonal and monoclinic-phase WO 3 films exhibit a change in conductivity of 01 Ω −1 cm −1 to 20 ppm H 2 S at 250°C, but display different response kinetics
149 citations
TL;DR: In this paper, the microstructure and electrical properties of indium oxide and tin oxide thin films are analyzed by XRD, AFM, and van der Pauw fourpoint-probe technique and the results discussed.
80 citations
TL;DR: In this article, the extraordinary magnetoresistance exhibited by a composite van der Pauw (vdP) disk consisting of a semiconductor with an internal shunt can also be obtained from an electrically equivalent, externally shunted structure that is amenable to fabrication in the mesoscopic sizes required for important magnetic sensor applications.
Abstract: We show that extraordinary magnetoresistance (EMR) exhibited by a composite van der Pauw (vdP) disk consisting of a semiconductor with an internal shunt can also be obtained from an electrically equivalent, externally shunted structure that is amenable to fabrication in the mesoscopic sizes required for important magnetic sensor applications. As an example, we use bilinear conformal mapping to transform the composite vdP disk into an externally shunted rectangular plate and calculate its EMR by solving Laplace’s equation with appropriate boundary conditions using no adjustable parameters. The calculations are in good agreement with measurements of InSb plates with Au shunts. Room-temperature EMR values as high as 550% at 0.05 T are obtained.
79 citations
TL;DR: In this article, the electrical conductivity of carbon aerogels is measured by the van der Pauw method and it is shown that the electrical capacity increases with the increase of both temperature and density of the aerogel.
Abstract: Carbon aerogels are prepared by a sol-gel process. By controlling the mass ratio of reactants and the molar ratio of resorcinol to catalyst (R/C), carbon aerogels with different microstructures can be developed. The electrical conductivity is measured by the van der Pauw method. The results show that the electrical conductivity increases with increase of both temperature and density of carbon aerogel. Cyclic voltammetry is a useful technique to investigate the electrochemical properties of carbon aerogel electrodes. The maximum specific capacitance of carbon aerogel electrode in H 2 SO 4 electrolyte is ∼86 F/g.
45 citations
TL;DR: In this article, multilayers of Bi2Sr2Ca1Cu2Ox/Bi2sr2Cu1Ox were prepared by pulsed laser deposition (PLD) using the fourth harmonic 266 nm YAG.
Abstract: Multilayers of Bi2Sr2Ca1Cu2Ox/Bi2Sr2Cu1Ox were prepared by pulsed laser deposition (PLD) using the fourth harmonic 266 nm YAG. Compared to an excimer laser, YAG PLD required the higher oxygen atmosphere. The higher oxygen pressure together with the lower energy generated by YAG laser collapsed the region of plume emission. In order to produce the same energy density as an excimer, only Q-switch was modulated by 2 Hz while the flash lamp kept the original repetition rate of 10 Hz. With the rate of 2 Hz, we obtained the higher energy density per pulse, and more stable laser output of the fourth harmonics, 266 nm. To characterize the multilayers, reflection high-energy electron diffraction (RHEED) and X-ray diffraction (XRD) were employed, and indicative of epitaxial layers with limited in-plane order. The resistivities of multilayers were measured by the Van der Pauw method, and showed the temperatures of superconducting transition, Tc0 (R=0), around 65 K on the multilayers.
29 citations
TL;DR: In this paper, the van der Pauw method has been applied to conductivity relaxation experiments on YBa2Cu3O6+δ at 600°C in order to determine the chemical diffusion coefficient as a function of the oxygen partial pressure in the surrounding atmosphere.
Abstract: The van der Pauw method has been applied to conductivity relaxation experiments on YBa2Cu3O6+δ at 600°C in order to determine the chemical diffusion coefficient as a function of the oxygen partial pressure in the surrounding atmosphere (100 > p
O
2/bar > 10−3). It is shown that the van der Pauw technique is suitable for monitoring the conductivity relaxation when the oxygen diffusion is perpendicular to the direct current flowing through the sample in accordance with the van der Pauw geometry using thin tablets as samples. The oxygen partial pressure is changed stepwise (generally Δlogp
O
2 ≤ 0.5) by employing appropriate gas mixtures as well as an electrochemical oxygen pump device. An evaluation formula is given for the determination of the chemical diffusion coefficient neglecting slow surface processes. In addition, the electronic conductivity of YBa2Cu3O6+δ has been measured at 600°C as a function of oxygen partial pressure of the ambient atmosphere (100 > p
O
2/bar > 10−5) by means of the van der Pauw method applying the same experimental set-up. Typical values of the chemical diffusion coefficient are in the range of 10−6 cm2·s−1; the results of the conductivity measurements are interpreted in terms of an appropriate defect model.
27 citations
TL;DR: In this paper, the electrical properties of extrinsic in situ doped mercury cadmium telluride (Hg1−xCdxTe) epilayers grown by molecular beam epitaxy on (211)B CdTe/Si and CdZnTe substrates are studied.
Abstract: The electrical properties of extrinsic in situ doped mercury cadmium telluride (Hg1−xCdxTe) epilayers grown by molecular beam epitaxy on (211)B CdTe/Si and CdZnTe substrates are studied. The doping is performed with an elemental arsenic source. HgCdTe epilayers with a CdTe mole fraction between 0.23 and 0.36 are grown at substrate temperatures of 175–185 °C. The temperature dependent Hall effect characteristics of the grown samples are measured by the van der Pauw technique. A magnetic field of up to 0.8 T is used in these measurements. An analysis of the Hall coefficient in the temperature range of 40–300 K with a fitting based on a two-band nonparabolic Kane model, a fully ionized compensating donor concentration, and two independent discrete acceptor levels is reported. In addition, the fitting results of a three-band modeling of Hall effect results are compared to published data on p-type Hg1−xCdxTe. Both as-grown and annealed samples are used in this study. All of the as-grown samples showed n-type c...
24 citations
TL;DR: In this paper, the optical absorption coefficient was measured on thin films grown on various substrates, on self-sustaining films, where the substrate was partly removed and on a single crystal by photothermal deflection spectroscopy.
Abstract: Recently, Ru2Si3 has been predicted to be a direct semiconductor with a band gap of ≈0.8 eV. Since the corresponding wavelength of this potential light emitter coincides with the absolute absorption minimum of glass fibers of 1.5 μm, considerable attention has been attracted. Measurements of the temperature dependence of the electrical resistivity of silicide films on insulating substrates were carried out in van der Pauw geometry. The results were explained by assuming carrier hopping over grain boundaries. The optical absorption coefficient was measured on thin films grown on various substrates, on self-sustaining films, where the substrate was partly removed and on a single crystal by photothermal deflection spectroscopy. A direct band gap at 0.84 eV was found. The absorption coefficient is very low up to ≈1.5 eV, likely due to a low density of states, and then strongly increases at higher energies. The experimental results qualitatively confirm the predictions of the band structure calculations.
13 citations
TL;DR: In this article, thin polycrystalline SnO2 films were deposited on glass substrates by magnetron sputtering and the electrical, optical, and gas-sensing properties, as well as the structure and phase composition of the films, were studied.
Abstract: Thin polycrystalline SnO2 films were deposited on glass substrates by magnetron sputtering. Electrical, optical, and gas-sensing properties, as well as the structure and phase composition of the films, were studied. The electrical resistance of the films and the concentration and mobility of free charge carriers were determined by the four-point-probe and van der Pauw methods. The band gap and the type of optical transitions in the films were derived from optical absorption spectra. The sensitivity to toxic and explosive gases was measured. The composition, morphology, and crystal structure of the films annealed at 600°C were examined by X-ray diffraction and electron microscopy. The films were found to contain only a tetragonal SnO2 phase and have good crystallinity. The average grain size in the annealed films is 11–19 nm. A model of the electrical conduction in the polycrystalline SnO2 films is discussed.
13 citations
TL;DR: In this paper, the electrical activation of As in Si has been measured with spreading resistance profiling, four point probe, and van der Pauw methods, and an inactive meta-stable As solid solution was formed in the near-surface region after amorphous layer regrowth.
Abstract: Arsenic implants performed in Si at ultralow energy have been extensively studied with structural, chemical, and electrical analysis. The near-surface damage annealing and its influence on the electrical activation of ultrashallow As in Si as a function of the anneal ambient has been investigated. Double alignment medium energy ion scattering, high resolution transmission electron microscopy, and low energy secondary ion mass spectrometry have been used to assess the dopant behavior and crystal recovery in the near-surface regions. The electrical activation of As in Si has been measured with spreading resistance profiling, four point probe, and van der Pauw methods. Major redistribution of the dopant into the SiO2–Si interface region occurred during crystal regrowth of the damaged Si layer. An inactive meta-stable As solid solution was formed in the near-surface region after amorphous layer regrowth. Electrical activation of the dopant occurred upon dissociation of the As solid solution, when the dopant c...
TL;DR: In this paper, the spectral dependence of the refractive index n and absorption coefficient a of the chalcopyrite compound Cu(In,Ga)Te-2 thin films were determined using rigorous expressions for transmission and reflection in an air/film/substrate/air multilayer system.
TL;DR: In this paper, the extraordinary magnetoresistance of an InSb van der Pauw disk with a centrally embedded cylindrical metallic inhomogeneity was calculated by solving the Maxwell equations with corresponding boundary value conditions.
TL;DR: In this paper, the structural and electrical properties of iron silicides in the transformation process from e-FeSi to βFeSi2 and show the electrical characteristics of heterostructure p-β-Fe0.95Mn0.05Si2/n-Si(100) diodes formed by high-dose Fe+ and Mn+ co-implantation in Si (100).
TL;DR: In this paper, the variation of the electron carrier occupation and the mobility in the subband as a function of the spacer layer thickness was investigated by Shubnikov-de Haas (S-dH) and Van der Pauw Hall-effect measurements.
12 Nov 2001
TL;DR: In this paper, the annealing and electrical properties of extrinsic in situ doped mercury cadmium telluride epilayers grown by molecular beam epitaxy (MBE) on B CdTe/Si and CdZnTe substrates are studied.
Abstract: The annealing and electrical properties of extrinsic in situ doped mercury cadmium telluride epilayers grown by molecular beam epitaxy (MBE) on B CdTe/Si and CdZnTe substrates are studied. The doping is performed with an elemental arsenic source. HgCdTe epilayers of CdTe mole fraction in the range of mid-wavelength IR are grown at substrate temperatures of 175-185 degrees C. The temperature dependent Hall effect characteristics of the grown samples are measured by the van der Pauw technique. A magnetic field of up to 0.8 T is used in these measurements. The analysis of the Hall coefficient in the temperature range of 40-300 K with a fitting based on a three-band non-parabolic Kane model, a fully ionized compensating donor concentration, and tow independent discrete acceptor levels is reported. Both as-grown and annealed samples are used in this study. All of the as-grown samples showed-type characteristics whereas annealed samples showed p-type characteristics. Activation annealing at different temperatures was performed. Conversion to p-type at lower than conventional annealing temperatures was achieved. Theoretical models are utilized to understand the dependence of the activated arsenic concentration on the annealing temperature.
TL;DR: In this article, the growth characteristics of AlxGa1−xN/GaN epilayers which were grown with various x values and their effects on the characteristics of UV LED chips fabricated by a GaN double heterojunction having different band offset were studied.
TL;DR: In this paper, the van der Pauw method was used to obtain the measurement values of anisotropic semiconductors using the finite element method (FEM) and it was clarified that the values are quite sensitive to anisotropy of the carrier mobility.
Abstract: Semiconductors, which are electrically anisotropic, are often obtained due to their methods of preparation or their own characteristics. Measurement values of such anisotropic semiconductors obtained by the van der Pauw method are simulated using the finite-element method (FEM). It is clarified that the values are quite sensitive to anisotropy of the carrier mobility, and variations in the measurement values can reach about two orders of magnitude even when the anisotropy is small.
Patent•
31 Jan 2001TL;DR: In this article, a method for measuring critical dimensions on photomasks using an electrical test structure was proposed, consisting of a cross resistor for van der Pauw sheet resistance measurements, a bridge resistor 34, and a split bridge resistor 36.
Abstract: A method for measuring critical dimensions on photomasks, and more specifically to a method for measuring critical dimensions on photomasks using an electrical test structure. The test structure 30 may be comprised of a cross resistor 32 for van der Pauw sheet resistance measurements, a bridge resistor 34 , and a split-bridge resistor 36.
TL;DR: The spark-source mass spectrometric assessment of silicon concentrations in silicon-doped vertical-gradient-freeze gallium arsenide is presented and the silicon concentrations determined are compared with the charge-carrier densities measured by means of the Hall effect with van der Pauw symmetry along the axis of a single crystal.
Abstract: The spark-source mass spectrometric assessment of silicon concentrations in silicon-doped vertical-gradient-freeze gallium arsenide is presented. The silicon concentrations determined are compared with the charge-carrier densities measured by means of the Hall effect with van der Pauw symmetry along the axis of a single crystal.
TL;DR: In this article, resistivity measurements on thermally evaporated Mn100−xNix films were performed over the temperature range from 300 to 1.4 K using the van der Pauw four probe technique.
TL;DR: In this paper, the electrical properties of a N ion implanted layer in (1100)-oriented 6H-SiC were investigated by means of Van der Pauw and Hall effect measurements.
Abstract: The electrical properties of a N ion implanted layer in (1100)-oriented 6H-SiC are investigated by means of Van der Pauw and Hall effect measurements. The samples are implanted using N ions at an energy of 30 keV with a dose ranging from 5 ×1014 to 5 ×1015/cm2 at room temperature. The samples annealed at 1500°C for 10 min show very low sheet resistance of the order of 102 Ω/\Box. The low sheet resistance is correlated to the high electrical activation of N impurities in the implanted layer with good crystalline quality.
TL;DR: In this article, van der Pauw measurements and FTIR spectroscopy were used to study thin film properties, such as resistivity and extinction coefficient, and simple engineering issues (i.e., the relationship between film thickness, resistance and transmission).
Abstract: : We have prepared lanthanum strontium cobalt oxide La(0.50)50Sr(0.50)Co(0.50)Ni(0.50)O3; LSCNO 50/50 and lanthanum strontium cobalt nickel oxide La(0.50)Sr(0.50)Co(0.50)Ni(0.50)O3; LSCNO as candidate transparent electrodes for use in a shutter-based infrared sensor protection device. The shutter device requires that the electrode be transparent (80% transmission) and have moderate sheet resistance (300 ohms/sq.). Because of the effects of film thickness on intrinsic material properties, such as resistivity and extinction coefficient, and simple engineering issues (i.e., the relationship between film thickness, resistance and transmission), films of various thicknesses were prepared to achieve an optimal balance of electrical and optical performance. van der Pauw measurements and FTIR spectroscopy were used to study thin film properties. The best LSCO films prepared demonstrated electrical (438 ohms/sq.) and optical (68% transmission at 8 micrometers) properties that did not meet the target property goals for this application. However, the LSCNO films (of optimal thickness) offered performance (323 ohms/sq. and 73% transmission) close to the device requirements.
01 Jan 2001
TL;DR: In this article, the first experimental report of Mg implantation on Mg-doped GaN and achieving high surface hole concentration was presented, and the p-type GaN was achieved with high hole concentration (8.28×10 17?cm -3 ) after annealing at 800?℃ for 1?h.
Abstract: Mg ions were implanted on Mg\|doped GaN grown by metalorganic chemical vapor deposition(MOCVD).The p\|type GaN was achieved with high hole concentration(8.28×10 17 ?cm -3 )conformed by Van der pauw Hall measurement after annealing at 800?℃ for 1?h.This is the first experimental report of Mg implantation on Mg\|doped GaN and achieving p\|type GaN with high surface hole concentration.
TL;DR: In this article, the growth of InP layers on GaAs substrates by molecular beam epitaxy (MBE) using gallium phosphide (GaP) as a phosphorus source was investigated.
01 Jan 2001
TL;DR: In this article, the van der Pauw method has been applied to conductivity relaxation experiments on YBa2Cu3O6+δ at 600°C in order to determine the chemical diffusion coefficient as a function of the oxygen partial pressure in the surrounding atmosphere.
Abstract: The van der Pauw method has been applied to conductivity relaxation experiments on YBa2Cu3O6+δ at 600°C in order to determine the chemical diffusion coefficient as a function of the oxygen partial pressure in the surrounding atmosphere (10° > p O2/bar > 10-3). It is shown that the van der Pauw technique is suitable for monitoring the conductivity relaxation when the oxygen diffusion is perpendicular to the direct current flowing through the sample in accordance with the van der Pauw geometry using thin tablets as samples. The oxygen partial pressure is changed stepwise (generally ∆log/po2 ≤ 0.5) by employing appropriate gas mixtures as well as an electrochemical oxygen pump device. An evaluation formula is given for the determination of the chemical diffusion coefficient neglecting slow surface processes. In addition, the electronic conductivity of YBa2Cu3O6+δ has been measured at 600°C as a function of oxygen partial pressure of the ambient atmosphere (10° > po 2 /bar > 10–5) by means of the van der Pauw method applying the same experimental set-up. Typical values of the chemical diffusion coefficient are in the range of 10-6cm2s-1; the results of the conductivity measurements are interpreted in terms of an appropriate defect model.
TL;DR: In this article, the Hall coefficient and electrical conductivity were measured by the standard van der Pauw technique over the temperature range from 93K to 283K from which the Hall carrier mobility was calculated.
Abstract: We prepared a series of (AgBiTe 2 ) 1−x (Ag 2 Te) x (0≤×≤1) composite materials by melt and cool down [1]. The Hall coefficient and the electrical conductivity were measured by the standard van der Pauw technique over the temperature range from 93K to 283K from which the Hall carrier mobility was calculated. Ag 2 Te had the highest mobility while the mobility of AgBiTe 2 was the lowest of all samples at 283K. However the mobility of the (AgBiTe 2 ) 0.125 (Ag 2 Te) 0.875 composite material was higher than the motility of Ag 2 Te below 243K. It seems that a small second phase dispersed in the matrix phase is effective against the increased mobility.
TL;DR: In this article, a high purity, stoichiometric InP is produced in crucible-shaped, 3-kg charges by the phosphorus injection method in a high-pressure magnetic liquid encapsulated Czochralski (MLEC) crystal growth system.
13 May 2001
TL;DR: In this paper, single crystals of chalcopyrite semiconductor CuInTe/sub 2/ have been grown by a vertical Bridgman technique and the optical properties were studied by photoacoustic spectroscopy in order to determine parameters such as absorption spectra, band gap and defect level states.
Abstract: In this paper, single crystals of chalcopyrite semiconductor CuInTe/sub 2/ have been grown by a vertical Bridgman technique. The Hall effect, mobility, resistivity and carrier concentration data have been obtained for several samples using the van der Pauw technique. The optical properties were studied by photoacoustic spectroscopy (PAS) in order to determine parameters such as absorption spectra, band gap and defect level states.
TL;DR: In this article, high-textured transparent conducting ZnO:Al thin films have been prepared by r.f. magnetron sputtering and the films were deposited on polyester (Mylar type D, 100 μm thickness) and glass substrates at room temperature.
Abstract: Highly textured transparent conducting ZnO:Al thin films have been prepared by r.f. magnetron sputtering. The films were deposited on polyester (Mylar type D, 100 μm thickness) and glass substrates at room temperature. Surface stylus profiling, X-ray diffraction, scanning electron microscopy, transmission electron microscope and Hall effect measurements as a function of temperature, using the van der Pauw technique have characterized the films. The samples are polycrystalline with a hexagonal wurtzite structure and a strong crystallographic c-axis orientation (002) perpendicular to the substrate surface (columnar structure). The ZnO:Al thin films with a resistivity as low as 3.6×10 −2 ωcm have been obtained, as deposited.