Showing papers on "Van der Pauw method published in 2000"
TL;DR: A symmetric van der Pauw disk of homogeneous nonmagnetic indium antimonide with an embedded concentric gold inhomogeneity is found to exhibit room-temperature geometric magnetoresistance as high as 100, 9100, and 750,000 percent at magnetic fields of 0.05, 0.25, and 4.0 teslas.
Abstract: A symmetric van der Pauw disk of homogeneous nonmagnetic indium antimonide with an embedded concentric gold inhomogeneity is found to exhibit room-temperature geometric magnetoresistance as high as 100, 9100, and 750,000 percent at magnetic fields of 0.05, 0.25, and 4.0 teslas, respectively. For inhomogeneities of sufficiently large diameter relative to that of the surrounding disk, the resistance is field-independent up to an onset field above which it increases rapidly. These results can be understood in terms of the field-dependent deflection of current around the inhomogeneity.
332 citations
TL;DR: In this article, the influence of the deposition parameters, such as oxygen pressure, substrate temperature and laser energy density variation on the properties of the grown film, was studied, and it was shown that the intensity of the light emission of laser-ablated ZnO thin films increased as substrate temperatures increased from 200 to 600°C.
63 citations
TL;DR: In this paper, a vertical type hot wall furnace was used as a reactor in the deposition system Zinc acetate dissolved in methanol was selected as a precursor, and the substrate temperature was varied from 180 °C to 240 °C.
Abstract: Transparent conductive aluminum-doped zinc oxide (AZO) films were prepared by an ultrasonic spray pyrolysis method. A vertical type hot wall furnace was used as a reactor in the deposition system Zinc acetate dissolved in methanol was selected as a precursor. The substrate temperature was varied from 180 °C to 240 °C. Aluminum (Al) was doped into ZnO films by incorporating anhydrous aluminum chloride AlCl3 in the zinc acetate CH3CO2)2Zn solution. The proportion of the Al in the starting solution was varied from 0 wt % to 3.0 wt %. The crystallographic properties and surface morphologies of the films were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The resistivity of the films was measured by the Van der Pauw method, and the mobility and carrier concentration were obtained through Hall effect measurements. Transmittance was measured in the visible region. The effects of substrate temperature and aluminum content in the starting solution on the structural and electrical properties of the AZO films are discussed.
49 citations
Patent•
30 Nov 2000TL;DR: In this article, a bilinear conformal mapping is used to transform a circular composite van der Pauw disk sensor (12) having an embedded conducting inhomogeneity (22) into a corresponding externally shunted rectangular plate structure.
Abstract: A symmetric van der Pauw disk (12) of homogeneous nonmagnetic semiconductor material, such as indium antimonide, with an embedded concentric conducting material (22), such as gold, inhomogeneity exhibits room temperature geometric extraordinary magnetoresistance (EMR) as high as 100 %, 9,000 % and 750,000 % at magnetic fields of 0.05, 0.25 and 4.0 Tesla, respectively. Moreover, for inhomogeneities of sufficiently large cross-section relative to that of the surrounding semiconductor material, the resistance of the disk is field-independent up to an onset field above which the resistance increases rapidly. These results can be understood in terms of the field-dependent deflection of current around the inhomogeneity. For example, a bilinear conformal mapping is used to transform a circular composite van der Pauw disk sensor (12) having an embedded conducting inhomogeneity (22) into a corresponding externally shunted rectangular plate structure. The result is an EMR sensor that can be realized in very simple structures which faccilitate fabrication in mesoscopic dimensions important for many magnetic sensor applications.
42 citations
TL;DR: In this paper, the authors presented transport measurements on both vacancy doped and gold doped Hg07Cd03Te p-type epilayers grown by liquid phase epitaxy (LPE), in which a thin 2 µm surface layer has been converted to n-type by a short reactive ion etching (RIE) process.
Abstract: This paper presents transport measurements on both vacancy doped and gold doped Hg07Cd03Te p-type epilayers grown by liquid phase epitaxy (LPE), with NA=2×1016 cm−3, in which a thin 2 µm surface layer has been converted to n-type by a short reactive ion etching (RIE) process Hall and resistivity measurements were performed on the n-on-p structures in van der Pauw configuration for the temperature range from 30 K to 400 K and magnetic field range up to 12 T The experimental Hall coefficient and resistivity data has been analyzed using the quantitative mobility spectrum analysis procedure to extract the transport properties of each individual carrier contributing to the total conduction process In both samples three distinct carrier species have been identified For 77 K, the individual carrier species exhibited the following properties for the vacancy and Au-doped samples, respectively, holes associated with the unconverted p-type epilayer with p ≈ 2 × 1016 cm−3, μ ≈ 350 cm2V−1s−1, and p ≈ 6 × 1015 cm−3, μ ≈ 400 cm2V−1s−1; bulk electrons associated with the RIE converted region with n ≈ 3 × 1015cm−3, μ ≈ 4 × 104 cm2V−1s−1, and n ≈ 15 × 1015 cm−3, μ ≈ 6 × 104 cm2V−1s−1; and surface electrons (2D concentration) n ≈ 9 × 1012 cm−2 and n ≈ 1 × 1013 cm−2, with mobility in the range 15 × 103 cm2V−1s−1 to 15 × 104 cm2V−1s−1 in both samples The high mobility of bulk electrons in the RIE converted n-layer indicates that a diffusion process rather than damage induced conversion is responsible for the p-to-n conversion deep in the bulk On the other hand, these results indicate that the surface electron mobility is affected by RIE induced damage in a very thin layer at the HgCdTe surface
37 citations
TL;DR: In this article, the preparation and characterisation of spectrally selective reflector surfaces of pyrolytically deposited fluorine-doped tin oxide (SnOx:F) on aluminium is reported.
37 citations
TL;DR: Magnetoresistance data taken along [ 2 3 3] and [ 0 1 1 ] directions in a GaAs/AlGaAs two-dimensional hole sample with van der Pauw geometry exhibit significant anisotropy at half-integer filling factors as discussed by the authors.
Abstract: Magnetoresistance data taken along [ 2 3 3] and [0 1 1 ] directions in a GaAs/AlGaAs two-dimensional hole sample with van der Pauw geometry exhibit significant anisotropy at half-integer filling factors. The anisotropy appears to depend on both the density and symmetry of the hole charge distribution.
37 citations
TL;DR: In this paper, a micromachined thermal van der Pauw test structure is reported, which consists of a cross-shaped sandwich of the dielectric CMOS layers isolated from the bulk silicon by four narrow suspension arms.
Abstract: A micromachined thermal van der Pauw test structure is reported. Similar in principle to the conventional electrical van der Pauw Greek cross test structures, it enables the in-plane thermal sheet conductivities of thin films to be determined. The microstructure was fabricated using a commercial CMOS application-specific integrated circuit process followed by anisotropic silicon etching. It consists of a cross-shaped sandwich of the dielectric CMOS layers isolated from the bulk silicon by four narrow suspension arms. Integrated polysilicon resistors make it possible to generate controlled amounts of heat power and to measure local temperature changes to determine the thermal response of the structure. The measurement principle exploits the analogy between the two-dimensional (2-D) heat flow in thin film samples and the electrical current pattern in thin film conductors. A thermal sheet resistance of 1.87/spl times/10/sup 5/ K/W was extracted from the complete sandwich of the dielectric CMOS layers. This resistance is equivalent to an average in-plane thermal conductivity of the dielectric layer sandwich of /spl kappa/=1.44 W m/sup -1/ K/sup -1/. Thermal finite element simulations showed that the radiative heat loss from the structure has a negligible effect on the extracted /spl kappa/ value.
30 citations
TL;DR: In this article, a non-gaseous source (ngs-) process is used for the growth of carbon doped (InGa)P/GaAs and InP/(InGaAs)As heterojunction bipolar transistors (HBT).
28 citations
TL;DR: In this article, LiCoO 2 -powder was synthesized from carbonate precursors by calcination in air and argon/air at 500/750°C.
28 citations
TL;DR: In this article, boron doped amorphous SiGe films and dopant activation were realized by furnace annealing at 550 and 570°C, temperatures which are suitable for processing on Corning glass 7059.
TL;DR: In this paper, it was shown that Si is predominantly an acceptor in AlSb, with an energy level 33±4 meV above the top of the valence band.
Abstract: Thick epitaxial layers of AlSb(Si) and AlSb(Be) were grown by molecular beam epitaxy and characterized by variable-temperature Hall/van der Pauw measurements. Si is shown to be predominantly an acceptor in AlSb, with an energy level 33±4 meV above the top of the valence band. Be is also an acceptor, with an energy level 38±4 meV above the top of the valence band. Be is a robust doping source for p-AlSb for carrier densities ranging from 1015 to 1019 cm−3. Background impurity levels in AlSb can be assessed by measuring the transport properties of lightly doped AlSb(Be) layers.
TL;DR: In this article, three different coating procedures have been used to investigate the effect on the structure, morphology and the electrical properties of tranparent conducting coatings, and it is shown that the individual layer thickness in multilayer coatings influences dramatically the mentioned properties.
Abstract: Tranparent conducting coatings have been prepared by sol gel methods either by a conventional sol-gel process (Antimony doped Tin Oxide—ATO, Aluminium doped Zinc Oxide—AZO) or a new wet chemical process using fully dispersed crystalline nanoparticles (ATO, Indium Tin Oxide—ITO). The dip coating technique has been used as deposition technique with single coating thickness varying from a few nanometer to ca. 400 nm. The layers have been fired in a furnace. Structural properties have been determined by x-ray diffraction and TEM analysis and the electrical properties by the van der Pauw/Hall measurement. Three different coating procedures have been used to investigate the effect on the structure, morphology and the electrical properties of the coatings. It is shown that the individual layer thickness in multilayer coatings influences dramatically the mentioned properties. Very thin individual layers favour a heterogeneous nucleation with dense columnar growth of the crystallites leading to low electrical resistivity (ρ ≈ 10−3Ω cm), while thick individual layers result in a porous morphology made of small crystallites leading to resistivities in the 10−2Ω cm range.
TL;DR: In this article, a short and fast iterative algorithm for calculating the geometric factor in a van der Pauw sheet resistance measurement is described, and fractional errors below 10−14 are obtained with less than 50 iterations for any value of the resistance ratio.
Abstract: A short and fast iterative algorithm for calculating the geometric factor in a van der Pauw sheet resistance measurement is described. Fractional errors below 10−14 are obtained with less than 50 iterations for any value of the resistance ratio RAB,CD/RBC,DA.
TL;DR: In this paper, germanium (Ge)-and zinc (Zn)-doped p-type InAs0.04Sb0.96 epilayers with a cutoff wavelength of 12.5 µm were grown on n-InAs substrates by melt epitaxy (ME).
Abstract: We grew germanium (Ge)- and zinc (Zn)-doped p-type InAs0.04Sb0.96 epilayers with a cutoff wavelength of 12.5 µm on n-InAs substrates by melt epitaxy (ME), and undertook a study of the properties of Ge-doped long-wavelength p-InAsSb epilayers. The quality of the epilayers was evaluated by transmittance, electroprobe microanalysis (EPMA) and Van der Pauw measurements. The results showed that the cutoff wavelength of the InAsSb epilayers with different levels of Ge doping showed no significant changes when the composition of the epilayers was kept constant. The Ge distribution, both on the surface and along the growth direction of the epilayer, is rather homogeneous. A maximum hole mobility of 1120 cm2/Vs with a carrier density of +9.18 ×1016 cm-3 at 77 K was achieved in a Ge-doped p-InAsSb epilayer. However, in the case of a Zn-doped epilayer, a hole mobility of 860 cm2/Vs with a carrier density of +2.48 ×1017 cm-3 was obtained at 77 K.
TL;DR: In this article, the chemical diffusion coefficient of polycrystalline nickel oxide was studied as a function of oxygen activity (10 5 atm < p O2 < 1 atm) and temperature (700°C < T < 1200°C).
TL;DR: In this article, the authors review the growth technique developed at McMaster University involving He-plasma-assisted gas source molecular beam epitaxy (GSMBE) which produces III-V materials with properties useful in specific device applications.
TL;DR: In this article, the authors report results of magneto-transport studies of homogeneous, highmobility, Te-doped InSb in a thin film van der Pauw disk geometry (radius r b ) containing a lithographically patterned, concentric, cylindrical metallic inhomogeneity.
Abstract: We report results of magneto-transport studies of homogeneous, high-mobility, Te-doped InSb in a thin film van der Pauw disk geometry (radius r b ) containing a lithographically patterned, concentric, cylindrical metallic inhomogeneity (radius r a ). The room temperature giant magnetoresistance (GMR) increases dramatically with increasing r a . We show that the GMR enhancement could in principle be made far larger by optimizing the material selection and lithographic patterning. We also discuss the potential impact of our results on read-head devices in high-density recording and on other magnetic sensors.
16 Oct 2000
TL;DR: In this paper, the authors measured transport parameters of semi-insulating GaAs using the van der Pauw method and demonstrated the advantage of using a constant voltage source instead of a constant current source in the case of high resistivity semiconductor materials.
Abstract: We measured transport parameters of semiinsulating (SI) and low temperature (LT) GaAs using the van der Pauw method A detailed procedure for semiinsulating sample preparation and for obtaining reliable experimental data is given The advantage of using a constant voltage source instead of a constant current source is demonstrated in the case of high resistivity semiconductor materials
TL;DR: In this article, large and in-plane anisotropic zero-field spin-splittings are found in two-dimensional electron gas (2DEG) formed at In x Ga 1− x As/In y Al 1− y As ( x, y > 0.6) heterojunctions.
Abstract: Large and in-plane anisotropic zero-field spin-splittings are found in two-dimensional electron gas (2DEG) formed at In x Ga 1− x As/In y Al 1− y As ( x , y >0.6) heterojunctions. Low-temperature magnetoresistance (MR) measurements were carried out in van der Pauw, Hall bar and quantum wire field effect transistor (QWR-FET) samples. Maximum spin–orbit coupling constant α zero of 78 (×10 −12 eVm ) was attained at 1.5 K in the Hall bar sample with the 〈−1 1 0〉 direction. Also, an in-plane anisotropy of almost twice as well as a gate-voltage-dependent change of α zero are confirmed in QWR-FET samples with 〈−1 1 0〉 and 〈1 1 0〉 directions. Those results suggest the importance of interface contribution to the zero-field spin splitting, which might be enhanced in our unique heterojunctions.
TL;DR: In this article, a GaInAs intermediate layer is used to prevent n-type inversion in Zn-doped AlInAs, which occurs when it is grown directly on an InP buffer layer.
TL;DR: In this paper, annealing was applied to InAsSb epilayers with cut off wavelength of 12.5 μm by GAO et al. They reported an electron mobility of 4.83 x 10 4 cm 2 /Vs and a carrier density of 8 x 10 15 cm -3 for InAs 0.04 Sb 0.96 epilayer at 77 K.
Abstract: We have reported narrowed band gap InAsSb single crystals with cut off wavelength of 8-12 pm grown by a new method of Melt Epitaxy (ME) (GAO et al. 1999). In this paper, we firstly present the improvement of low temperature mobility of the InAsSb epilayers with cut off wavelength of 12.5 μm by annealing treatment. The electrical properties were investigated by Van der Pauw measurements at 300 K and 77 K. After an annealing treatment for 11 hours, an electron mobility of 4.83 x 10 4 cm 2 /Vs and a carrier density of 8 x 10 15 cm -3 have been obtained for an InAs 0.04 Sb 0.96 epilayer at 77 K. This is the best result so far for the InAsSb materials with cut off wavelength of 8-12 μm. The mechanism of the improvement of the electrical properties for this material after annealing treatment was studied by observing the etch pits on the surface of the sample before and after heat treatments.
TL;DR: In this paper, zero-field spin-splittings are estimated from low-temperature magnetoresistances in two-dimensional electron gas (2DEG) in In x Ga 1−x As / In y A 1 1−y As (x,y=0.75) van der Pauw, Hall-bar and quantum wire field effect transistor (QWR-FET) samples.
Abstract: Zero-field spin-splittings are estimated from low-temperature magnetoresistances in two-dimensional electron gas (2DEG) in In x Ga 1−x As / In y A 1 1−y As (x,y=0.75) van der Pauw, Hall-bar and quantum wire field effect transistor (QWR-FET) samples. Maximum spin–orbit coupling constant α zero of 78 (×10 −12 eVm) was obtained in the Hall bar sample with 〈−1 1 0〉 direction, which has a sheet electron density and a mobility at 1.5 K of 1.1×10 12 /cm 2 and 5.54×10 5 cm 2 / Vs . In-plane anisotropies of mobility as well as of α zero are confirmed in QWR-FET samples with 〈1 1 0〉 and 〈1 1 0〉 directions. If those results are considered together with the fact that a part of α zero was able to be changed by the gate-voltage, interface effect contributing to the zero-field splitting might play an important role in this heterojunction.
TL;DR: In this article, the optical, crystallographic and transport properties of nominally undoped n-type ZnS x Se 1−x /Si grown by atomic layer epitaxy have been studied.
TL;DR: In this paper, the van der Pauw four probe technique was used to conduct DC measurements for 0 to 100 vol%Cu films in the temperature range 150 to 600 K. The samples were 200 nm thick, deposited at 600 K at a rate of 0.8 nm/s.
Abstract: Thin films containing 0 to 100 vol%Cu was prepared by thermal co-evaporation. The samples were 200 nm thick, deposited at 600 K at a rate of 0.8 nm/s. DC conductivity measurements were carried out using the van der Pauw four probe technique for 0 to 100 vol%Cu films in the temperature range 150 to 600 K. Samples containing ≥60 vol%Cu exhibited a ‘metallic-like’ behaviour with positive TCR whereas lower concentrations exhibited an activated conduction mechanism with negative TCR.
TL;DR: The magnetic and magneto-resistive properties of the samples have been measured by vibrating sample magnetometery and van der Pauw method, respectively, at the temperatures ranging 100 K-300 K with applied magnetic field of 0.4 T.
Abstract: Bi-doped lanthanum manganites with chemical compositions of BixLa0.67 − xCa0.33MnO3 (x = 0, 0.04, 0.1, 0.2) have been prepared by the standard ceramic process. The crystallinity and microstructures of the samples have been investigated by x-ray diffractometry and optical microscopy, respectively. The magnetic and magneto-resistive properties of the samples have been measured by vibrating sample magnetometery and van der Pauw method, respectively, at the temperatures ranging 100 K–300 K with applied magnetic field of 0.4–0.5 T. Good crystallinity and high Curie temperature (275 K) have been obtained for the Bi-doped samples with small dosage (x = 0.04, 0.1) even they were sintered at 1200°C, which is about 200°C lower than normal sintering temperature of undoped sample. The Bi-doped samples with the small dosage showed lower relative electrical resistivity and higher magneto-resistive ratio compared to the undoped sample in the most temperatures measured. The Bi-doped samples also exhibited large magneto-resistive ratio (maximum of 15% for x = 0.1) at room temperature even under a weak magnetic field of 0.4 T.
TL;DR: In this paper, the abplane resistivity of La2−xSrxCuO4 single crystals with small Sr content (x=0.052÷0.075) between 4.2 and 300 K was measured using the AC Van der Pauw technique.
Abstract: We have measured the ab-plane resistivity of La2−xSrxCuO4 single crystals with small Sr content (x=0.052÷0.075) between 4.2 and 300 K by using the AC Van der Pauw technique. As recently suggested by Ichikawa et al., the deviation from the linearity of the πab(T) curve starting at a temperature Tch can be interpreted as due to a progressive slowing down of the fluctuations of pre-formed charge stripes. An electronic transition of the stripes to a more ordered phase could instead be responsible for some very sharp anomalies present in the πab(T) of superconducting samples just above Tc.
TL;DR: In this paper, amorphous silicon films with B, P, and As implants were activated with thermal anneals that include spiking to the maximum temperature, and they were grown over thermal oxide by chemical vapor deposition as two separately implanted 50-nm layers for manipulating dopant placement and diffusion.
Abstract: Amorphous silicon films with B, P, and As implants were activated with thermal anneals that include spiking to the maximum temperature. Films were grown over thermal oxide by chemical vapor deposition as two separately implanted 50-nm layers for manipulating dopant placement and diffusion. Electrical activation was determined by Hall van der Pauw and MOS C-V, and dopant diffusion was profiled by secondary ion mass spectroscopy (SIMS). Flat-band voltage was used to benchmark relative thermal budgets for p-type poly. Temperature-time relationships are used to deduce effective activation energies.
TL;DR: In this paper, pressure-induced transformations of silicon, namely, Si-III (BC-8) and Si-IX are identified by X-ray diffraction in a Si-I matrix on deposits formed by vacuum plasma spray.
Abstract: Polycrystalline silicon deposits were formed on a monocrystalline silicon substrate by thermal spraying. The resulting structure exhibits a device characteristic. Pressure-induced transformations of silicon, namely, Si-III (BC-8) and Si-IX are identified by X-ray diffraction in a Si-I matrix on deposits formed by vacuum plasma spray. The presence of the Si-III and Si-IX indicates that the pressure-quenched silicon deposit is highly conductive, as determined by four-point van der Pauw resistivity measurement. Hall mobility measurements, combined with photoconductivity results, indicate that the highly conductive silicon deposit displays the same range of mobility as a polycrystalline deposit containing only Si-I. The silicon deposit, with or without metastable phases, displays the same photoconductivity properties. The silicon deposit on a monocrystalline silicon substrate exhibits rectifying I–Vcharacteristics, possibly caused by band bending of trapping states associated with impurities segregating at the polycrystalline deposit/monocrystalline substrate interface