Showing papers on "Van der Pauw method published in 1992"
TL;DR: In this paper, the authors developed a formalism to calculate the weighting function, applying it to square van der Pauw samples and to linear and square four-point probe arrays.
Abstract: Resistivity measurement is a weighted averaging of local resistivities. We develop a formalism to calculate the weighting function, applying it to square van der Pauw samples and to linear and square four‐point probe arrays. In each case, some regions of the sample are negatively weighted, but these regions can be reduced or eliminated by van der Pauw averaging. We discuss negative weighting, which we feel is responsible for spurious reports of superconductivity above room temperature. We show how a square four‐point array can be more effective at measuring local resistivity than a linear one. Finally, we show how to apply our formalism to anisotropic materials.
58 citations
TL;DR: In this paper, a patterned semiconducting polycrystalline diamond films have been synthesized by hot-filament CVD using in situ doping by pure boron powder.
Abstract: Patterned semiconducting polycrystalline diamond films have been synthesized by hot‐filament CVD using in situ doping by pure boron powder. P‐type conduction was confirmed by both Hall and Seebeck effects. The quality of deposited films, as determined by SEM and Raman spectroscopy, was unaffected by the doping. The resistivity and Hall mobility measured by the Van der Pauw method were in the range of 20–100 Ω cm and 2–32 cm2 V−1 s−1, respectively. The dopant activation energies, as computed from the resistivity versus temperature curves (up to 300 °C), were in the range of 0.38–0.30 eV corresponding to Hall concentration in the range of 9×1015–2×1017 cm−3 and boron concentration in the range of 1017–1021 cm−3. The estimated impurity concentration is consistent with SIMS results.
35 citations
TL;DR: In this article, the van der Pauw Hall effect measurements from 77-350 K were reported for a series of p-type nitrogen-doped ZnSe thin films, and Epitaxial HgSe electrodes were used as ohmic contacts.
Abstract: The van der Pauw Hall effect measurements from 77–350 K are reported for a series of p‐type nitrogen‐doped ZnSe thin films. Epitaxial HgSe electrodes were used as ohmic contacts in these experiments.
32 citations
TL;DR: In this article, an ohmic contact metallization with a specific contact resistivity of 2 × 10 −5 Ω-cm 2 on heavily doped diamond films was developed for active electronic devices.
20 citations
TL;DR: In this article, a computer-controlled system for electrical conductivity measurements using the van der Pauw four-probe method was constructed using a compressed powder disc, which is automatically measured for both AC and DC at various temperatures.
Abstract: A computer-controlled system for electrical conductivity measurements has been constructed using the van der Pauw four-probe method. Electrical conductivity of a compressed powder disc is automatically measured for both AC and DC at various temperatures (120-400 K). The measurement is facilitated by switching the current and voltage probe using a microcomputer and electrical relay.
19 citations
TL;DR: In this paper, a natural IIa diamond was implanted with boron ions at a substrate temperature of 80 K. Van der Pauw resistivity/Hall measurements were taken as a function of temperature from room temperature to nearly 600 °C.
Abstract: A natural IIa diamond was implanted with boron ions at a substrate temperature of 80 K. Ohmic contacts (Mo/Au) were formed using a solid‐state reaction process. Van der Pauw resistivity/Hall measurements were taken as a function of temperature from room temperature to nearly 600 °C. Heating to approximately 350 °C was necessary to stabilize resistance values to over 3.4 MΩ/sq and 1.3 MΩ/sq for the unimplanted and implanted sides, respectively, indicating possible hydrogen incorporation into the diamond during annealing of the metallized sample in hydrogen. Comparison of the electrical properties of the implanted and unimplanted sides showed that the boron implant introduced electrically active acceptors.
16 citations
TL;DR: In this paper, resistivity measurements have been carried out on thin films of evaporated α-Mn between 300 and 1.5 K using the Van der Pauw technique, revealing a wide variety of low temperature behaviours ranging from that typical of bulk α-mn to that regarded as typical of a metallic alloy glass with a negative temperature coefficient of resistivity at room temperature.
15 citations
TL;DR: In this article, the dependence of the two-point resistance on the electrode size, sample radius, and thickness was investigated both theoretically and experimentally, and an expression was given for the dependence on the twopoint resistance.
Abstract: Current‐voltage relations on circular samples with four equally spaced semicircle electrodes are investigated both theoretically and experimentally. An expression is given for the dependence of the two‐point resistance on the electrode size, sample radius, and thickness. Combining this with a four‐point van der Pauw conductivity measurement enables the determination of the electrode overpotential. Experimental results of the I‐V relations in a thin carbon layer are presented.
14 citations
TL;DR: In this article, the effects of a thin nucleation layer of AlN on the magnetron sputtering growth of InN are investigated in comparison with films deposited onto bare sapphire surfaces.
11 citations
TL;DR: The formation of epitaxial CoSi2 on (001) Si using the solid state reaction between an amorphous Co75W25 sputtered layer and Si has been studied as mentioned in this paper.
Abstract: The formation of epitaxial CoSi2 on (001) Si using the solid state reaction between an amorphous Co75W25 sputtered layer and Si has been studied. Auger electron spectroscopy depth profiling, Rutherford backscattering spectrometry, x‐ray diffraction, transmission electron microscopy, and resistivity and mobility measurements on Van der Pauw structures have been used to investigate the interaction between the amorphous alloy and Si. By employing anneals in vacuum between 500 and 600 °C for 60 or 120 min, Co diffuses out of the alloy into the substrate to form CoSi2. X‐ray diffraction measurements indicate that the greater part (about 75%) of the disilicide film is epitaxial. The CoSi2 film is unstrained at the growth temperature. At room temperature a tetragonal distortion of the silicide lattice is noted, which results from cooling from the growth temperature, and is caused by the difference in the thermal expansion coefficients of Si and CoSi2. After a selective etch to remove the remaining amorphous allo...
10 citations
TL;DR: In this paper, Boron-doped polycrystalline diamond films (PDFs) were synthesized by thermal filament chemical vapour deposition, and the Hall effect, together with the resistivity of samples with different dosages, was measured by Van der Pauw's method.
TL;DR: In this article, the authors reported the contactless determination of the conductivity, the mobility and the carrier concentration of II-VI semiconductors by means of the technique of the partially filled waveguide at a microwave frequency of 9 GHz.
Abstract: We report the contactless determination of the conductivity, the mobility and the carrier concentration of II–VI semiconductors by means of the technique of the partially filled waveguide at a microwave frequency of 9 GHz. The samples are CdHgTe epitaxial layers, grown on CdZnTe substrates by molecular beam epitaxy. The conductivity is determined from the transmission coefficient of the sample in the partially filled waveguide. For the analysis of the experimental data, the complex transmission coefficient is calculated by a rigorous multi-mode matching procedure. By varying the conductivity of the sample, we obtain an optimum fit of the calculated data to the experimental results. Comparison with conductivity data determined by the van der Pauw method shows that our method allows to measure the conductivity with good accuracy. The behaviour of the transmission coefficient of the sample is discussed in dependence on the layer conductivity, the layer thickness and the dielectric constant of the substrate. The calculations require to consider in detail the distribution of the electromagnetic fields in the sample region. The usual assumption of a hardly disturbed TE10 mode cannot be used in our case. By applying a magnetic field in extraordinary Voigt configuration, galvanomagnetic measurements have been carried out which yield the mobility and thus the carrier concentration. These results are also in good agreement with van der Pauw transport measurements.
TL;DR: In this article, the authors showed that the superconductive critical temperature is not described by mean-field theory and showed that a broad resistive transition occurs only in films of thin (two or three atomic-lattice cells) Y-compound layers and thick (PrBa 2 Cu 3 O 7 ) layers.
Abstract: Experimental measurements of four-terminal (van der Pauw) transport-current resistivity and of dynamic AC magnetic response of certain superlattice films show broad resistive transitions and frequency-dependent magnetic transitions into the superconductive state. Such observations indicate that the superconductive critical temperature is not described by mean-field theory. pitaxial, c ⊥ superlattice films of YBa 2 Cu 3 O 7 /PrBa 2 Cu 3 O 7 were grown in situ by laser ablation. Layer thicknesses of each compound ranged from two to four atomic cells. While material inhomogeneity can produce such a broad resistive transition,it would prevent our observation of a relatively sharp step-like transition in the inductive impedance. Such response must arise due to vibrations of pinned and bound supercurrent vortices. Observation of the Kosterlitz-Thouless (K-T) transition of bound vortices is expected to occur in a two-dimensional system. We see apparent K-T transitions only in films of thin (two or three atomic-lattice cells) Y-compound layers and thick Pr-compound layers. This systematically implies that extreme anisotropy of CuO superconductors can be tied to observations of two-dimesional physical phenomena.
TL;DR: In this paper, Shubnikov-de Haas and Van der Pauw Hall effect measurements at 1.5 K have been carried out to investigate the existence of a two-dimensional electron gas and to determine subband energies in Si-delta-doped GaAs grown by atmospheric pressure metalorganic chemical vapor deposition.
02 Jan 1992-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, the authors compared the performance of random and implantable van der Pauw patterns under channeling and random conditions and showed that the shape of the profiles dramatically changes due to dechanneling caused by the crystal disorder.
Abstract: Phosphorus ions in the energy range 0.25—1 MeV and in the dose range 2 × 1013–1 × 1015 P/cm2 were implanted into (100) Si single crystal at different tilt angles. In particular channeling and random conditions were investigated. For comparison some implants were performed on samples with a 2 μm thick surface amorphous layer. Chemical concentration P profiles were obtained by secondary ion mass spectrometry. Carrier concentration and mobility profile measurements were carried out by sheet resistance and Hall measurements on implanted van der Pauw patterns. Carrier concentration profiles were also obtained by spreading resistance (SR) measurements. The damage in the as-implanted samples was determined by backscattering and channeling spectrometry (RBS) as a function of the dose and implantation energy. Comparison of random implants in crystal with implants in amorphous layers shows that in the first case it is impossible to completely avoid the channeling tail. In the implants performed under channeling conditions at low doses the P profiles are flat over more than 2 μm thick layers. Furthermore, by increasing the implanted dose, the shape of the profiles dramatically changes due to the dechanneling caused by the crystal disorder. The data are discussed and compared with Monte Carlo simulations using the MARLOWE code. A simple description of the electronic energy loss provides an excellent agreement between the calculated and experimental profiles.
TL;DR: In this paper, it has been confirmed that there are some areas of a square sample near the corners besides the boundary suitable to the resistance measurement of Van der Pauw's method.
Abstract: By using conformal transformation to take account of the boundary effect, it has been confirmed that there are some areas of a square sample near the corners besides the boundary suitable to the resistance measurement of Van der Pauw’s method. The theoretical criterion of the suitability is whether Van der Pauw’s formula for calculation of the sheet resistance is still valid provided the voltage values in the formula for two times the measurement are substituted with those obtained by using the theory of conformal transformation. The experimental criterion is whether the experimental values of sheet resistance for probes in some areas are equal to that for them at the boundary for the same sample. The experimentally confirmed areas are larger than what the theory predicts. Our repeated experiments show that the areas out of the circle tangent to the boundary are suitable to Van der Pauw’s method.
TL;DR: In this article, the shrinkage of the lattice constant of the (p+) GaAs epilayer was found to be initiated by the tensile stress on the epilayers.
Abstract: The well‐known abnormal outdiffusion problem of heavily Be‐doped GaAs prepared by molecular‐beam epitaxy was found to be initiated by the shrinkage of the lattice constant of the (p+) GaAs epilayer. Through detailed investigation of the double‐crystal x‐ray spectra, van der Pauw measurements, photoluminescence, and infrared‐absorption spectra of Be‐doped GaAs for various doping concentrations, it is found that there exists a critical doping concentration, i.e., 2.6×1019/cm3, beyond which the lattice constant of the epilayer starts to shrink and the Be outdiffusion into the substrate is significantly enhanced. Apparently, the tensile stress on the epilayer results in the abnormal Be outdiffusion. The absorption coefficient of Be‐doped GaAs in the 8–10 μm region with carrier concentration 8.3×1019/cm3 are found to be about 104 cm−1 which is useful for the application of this layer to a p+‐type AlGaAs/GaAs heterojunction infrared detector.
TL;DR: In this article, natural type IIa (insulating) diamonds were implanted at liquid nitrogen temperature with either boron or carbon plus borons Van der Pauw resistivity and Hall effect measurements as a function of temperature were used to determine the effect of the implantation, in comparison with the unimplanted side of the sample.
Abstract: Natural type IIa (insulating) diamonds were implanted at liquid nitrogen temperature with either boron or carbon plus boron Van der Pauw resistivity and Hall effect measurements as a function of temperature were used to determine the effect of the implantation, in comparison with the unimplanted side of the sample Implantation with carbon plus boron resulted in a carrier concentration more than an order of magnitude greater than that resulting from implantation with boron alone, but with a much lower hole mobility
TL;DR: In this article, the authors measured the Hall mobility in semi-insulating GaAs by probing the Hall voltage dropped across the thickness of the sample optically by exploiting the linear electro-optic (Pockels) effect in the material.
Abstract: The Hall mobility in semi‐insulating GaAs has been measured by probing the Hall voltage dropped across the thickness of the sample optically. This is achieved by exploiting the linear electro‐optic (Pockels) effect in the material. The method only involves two electrical contacts to the sample which gives a distinct advantage over the conventional Hall or Van der Pauw techniques. It permits, in principle, the direct measurement of the time evolution of carrier populations, a useful corollary to transient photoconductivity. It also makes possible the measurement of a Hall voltage dropped across the width of a quantum well.
TL;DR: In this article, the effects of elevated temperature annealing on reactive rf magnetron sputtered InN films have been conducted. But the results of the experiments were limited to a single set of films grown at 100°C and annealed at an elevated temperature (Ta).
Abstract: Two related studies of the effects of elevated temperature annealing on reactive rf magnetron sputtered InN films have been conducted. In the first study, thin films of InN were deposited and annealed in 5 mTorr of nitrogen gas using a conventional high-vacuum (HV) magnetron sputtering system. Films were grown at 100°C and following annealing at an elevated temperature (Ta) for 4 hours were removed from the system for physical characterization. The physical properties of the annealed films improved with thermal treatment and were strikingly coincident with the properties of a second set of films grown at Ta. In the second study, films were deposited at 400°C in 5 mTorr of nitrogen gas using an ultrahigh-vacuum (UHV) sputtering system. Samples were annealed (at 550°C) and electrically characterized under UHV conditions using a custom designed annealing furnace with an integral Van der Pauw probe. Contrary to expectations, the carrier concentration of these films showed a steady decrease with extended annealing and the carrier mobility nearly doubled after 15 hours of treatment.
TL;DR: In this article, thin films of superconducting Pb2Sr2Y0.5Ca 0.5Cu3O8+δ have been grown in situ on (100) MgO substrates using the laser ablation technique, in vacuum, and also in low oxidizing atmosphere.
TL;DR: In this paper, Shubnikov-de Haas and Van der Pauw Hall effect measurements on strained InAs0.6P0.4/InP one-side-modulation-doped quantum wells grown by metalorganic chemical vapour deposition have been performed in order to investigate the properties of an electron gas in an single quantum well.
Abstract: Shubnikov-de Haas and Van der Pauw Hall effect measurements on strained InAs0.6P0.4/InP one-side-modulation-doped quantum wells grown by metalorganic chemical vapour deposition have been performed in order to investigate the properties of an electron gas in an InAs0.6P0.4 single quantum well. Hall effect measurements showed that the mobility and the carrier concentration were 40800 cm2 V-1 s-1 and 1.43*1012 cm-2 at 1.5 K, respectively. The Shubnikov-de Haas measurements and fast-Fourier analyses clearly showed an oscillation frequency, which changes with the angle between the magnetic field and the surface normal, indicative of the occupation of the InAs0.6P0.4 potential well by two-dimensional electrons. The subband energies and energy wavefunctions were determined using the experimental results and a self-consistent method taking into account the exchange-correlation effects.
TL;DR: In this paper, high quality ZnSe epitaxial layers (epilayers) on CaF 2 (111) transparent substrate have been successfully fabricated for the first time by atmospheric pressure metallo-organic chemical vapour deposition, using dimethylzinc and H 2 Se as sources.
TL;DR: In this paper, the authors investigated the dependence on growth parameters to establish optimum conditions for a bottom contact layer of a double-heterostructure (DH) laser diode monolithically integrated with its driver circuit on a semi-insulating InP substrate.
TL;DR: In this paper, SIMOX wafers were implanted with high doses of cobalt and annealed at high temperature in order to study the formation of buried single-crystal CoSi 2 layers in this material.
Abstract: SIMOX (separation by implanted oxygen) wafers were implanted with high doses of cobalt and annealed at high temperature in order to study the formation of buried single-crystal CoSi 2 layers in this material. For this study SIMOX wafers of (100) oriented silicon were implanted at 100–200 KeV with doses of 1.2–2.0×10 17 Co + cmsu−2, and annealed in a rapid thermal processor or tube furnace. As-implanted and annealed samples were analyzed by Rutherford backscattering with channeling spectroscopy (RBS), cross-sectional transmission electron microscopy (XTEM), secondary ion mass spectroscopy, and the van der Pauw technique. The best buried CoSi 2 layers were obtained at an implantation energy of 100 KeV and by subsequent rapid thermal annealing. RBS minimum yields of approximately 6% were obtained for the buried layer, which is the same as that reported for bulk (100) silicon. The measured resistivity of 15 μω cm and XTEM confirmed the continuity of the layer. Buried CoSi 2 layers were successfully produced up to an implantation energy of 180 keV. However, as the energy was increased the quality of the CoSi 2 layer degraded, with minimum yields increasing to 24% at 180 keV, and with a corresponding degradation in the minimum yields in the top silicon layer. At 200 keV a buried epitaxial layer was not produced. The degradation of crystal quality with ion implantation energy and the failure to produce a buried layer at 200 keV are discussed.
TL;DR: In this article, a site-percolative computer simulation of the superconducting transition of BiSr-Ca-Cu-O polycrystalline thin films is presented.
Abstract: Several Bi-Sr-Ca-Cu-O polycrystalline thin films have been produced ex situ by sequential thermal evaporation. The relativity broad superconducting transition of these films was characterized both resistively and inductively. The maximum of the derivative of the inductive measurement curve was found, within experimental accuracy, to correspond to the resistively obtained Tc (zero). A discrepancy between the two measurement techniques was observed for the onset of the transition. The resistive van der Pauw technique indicates Tc (onset) typically above 90 K and Tc (zero) at around 79 K. On the other hand, the inductive transition starts only around 5 K above the resistively obtained Tc (zero). Percolation theory is employed in an attempt to explain these observations. In this site-percolative computer simulation, the concept of the average cluster size is modified to incorporate the effect of superconducting closed loops.
TL;DR: Shubnikov-de Haas and Van der Pauw Hall effect measurements on an In052Al048As/In065Ga035As lattice mismatched single quantum well grown by molecular beam epitaxy have been carried out to investigate the electrical properties of an electron gas and subband energies in a unique potential well.
Abstract: Shubnikov-de Haas and Van der Pauw Hall effect measurements on an In052Al048As/In065Ga035As lattice-mismatched single quantum well grown by molecular beam epitaxy have been carried out to investigate the electrical properties of an electron gas and subband energies in a unique potential well The measurements at 15 K have demonstrated clearly the existence of a quasi-two-dimensional electron gas in the quantum well It is found that three subbands in the quantum well are occupied Electron energy subbands in the quantum well were calculated by a self-consistent method taking into account exchange-correlation effects and making use of the experimentally determined carrier density
TL;DR: In this article, the magnetotransport properties of an electron gas and the subband energies and wave functions in a single quantum well were determined using the experimental results and a self-consistent method by taking into account the exchange-correlation effects.
02 Feb 1992-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: Ion beam analyses have been used for characterization of superconducting Y1Ba2Cu3O7 − x thin films deposited by reactive co-sputtering from Y, BaCu and Cu targets combined with in situ postannealing as mentioned in this paper.
Abstract: Ion beam analyses have been used for characterization of superconducting Y1Ba2Cu3O7 − x thin films deposited by reactive co-sputtering from Y, BaCu and Cu targets combined with in situ postannealing. Ion backscattering spectra for4He and 12C ions have been obtained in the energy range 2–20 MeV. Resonant scattering of 4He ions from 16O at 3.045 MeV has been used to determine the oxygen contents of the films. The data from these measurements have been compared to results obtained with other characterization methods. The film morphology and lateral homogeneity have been examined using SEM and SIMS element mapping. X-ray diffraction have been used for crystalline phase identification. The film resistivity as a function of temperature has been measured in a cryocooler using the Van der Pauw method.
21 Apr 1992
TL;DR: The effects of ytterbium addition to the melt of InGaAs grown on InP by liquid phase epitaxy are studied in this paper, where the results show that the background carrier concentrations of the epilayers were reduced by more than one order of magnitude.
Abstract: The effects of ytterbium addition to the melt of InGaAs grown on InP by liquid phase epitaxy are studied. Samples were examined by double-crystal X-ray diffractometry, photoluminescence, secondary ion mass spectroscopy, and Hall/van der Pauw measurements. After Yb addition, the background carrier concentrations of the epilayers were reduced by more than one order of magnitude; the samples luminesced considerably more strongly; the lattice matching was not appreciably affected by the Yb; and no Yb was found in the epilayers themselves. It is believed the Yb is both acting as a scavenging agent in the melt, tying up impurities that otherwise would have been incorporated in the epilayers, and introducing impurities of its own. >