Showing papers on "Van der Pauw method published in 2006"
TL;DR: In this paper, a van der Pauw (VDP) structure was used for sheet resistance measurement on (100) and (111) silicon surfaces, and it was predicted theoretically that VDP devices will exhibit more than three times higher sensitivity to stress than standard resistor sensors.
Abstract: Piezoresistive sensors fabricated on (100) and (111) silicon surfaces are capable of measuring from four to all six components of the stress state at a point on the surface of an integrated circuit die. Such resistor-based sensors have been successfully designed and fabricated on these wafer planes and have been used successfully for measurement of die stresses in electronic packages by many research teams. In this paper, classical van der Pauw (VDP) structures, traditionally used for sheet resistance measurement, are shown to provide more than three times the sensitivity of standard resistor sensors. A single four-terminal VDP device replaces two resistor rosette elements and inherently utilizes the high-accuracy four-wire resistance measurement method. Theoretical expressions are developed for the change in resistance of the VDP device as a function of the individual stress components resolved in wafer coordinate systems on both the (100) and (111) silicon surfaces, and it is predicted theoretically that VDP devices will exhibit more than three times higher sensitivity to stress than standard resistor sensors. Design, fabrication, and experimental characterization of VDP and resistor test structures are presented for both silicon surfaces, and numerical simulation is used to help resolve discrepancies between theory and experiment. Sources of experimental error are identified, and the 3.16 times sensitivity enhancement of the VDP device is confirmed.
78 citations
TL;DR: Van der Pauw et al. as mentioned in this paper used pulsed magnetron sputtering of transparent conductive oxide (TCO) films from powder targets, which produces films with dense columnar, defect-free structures and optical and electrical properties comparable to other deposition techniques.
Abstract: The pulsed magnetron sputtering of transparent conductive oxide (TCO) films from powder targets is a promising technique, which produces films with dense columnar, defect-free structures and optical and electrical properties comparable to other deposition techniques. The targets are formed from loosely packed oxide powder blends, and no additional processes, such as sintering, are required. This preparation method allows target composition and, therefore, film composition (a key parameter in TCO coatings) to be readily varied. The flexibility of this approach was exploited to produce a series of doped zinc oxide coatings, in which both the dopant level (1–5at.%) and the dopant material (Al, Sn, In, Sb, or Ga) were varied systematically. The structures and properties of these coatings were analyzed and measured using a range of techniques, including electron microscopy, spectrophotometry, x-ray diffraction, four-point probe, and Van der Pauw’s method. The TCO coatings were deposited in a rig specially desi...
41 citations
TL;DR: Cadmium telluride (CdTe) thin films were prepared by the closed-space sublimation (CSS) technique, using CdTe powder as evaporant onto substrates of water-white glass as mentioned in this paper.
37 citations
TL;DR: In this article, electrical resistivity and Hall effect measurements of pellets compacted from fullerene-like WS2 nanoparticles (IF -WS2) and bulk 2H-WS2 powder were carried out using the van der Pauw method over a wide temperature range.
Abstract: Electrical resistivity and Hall effect measurements of pellets compacted from fullerene-like WS2 nanoparticles (IF -WS2) and bulk 2H-WS2 powder were carried out using the van der Pauw method over a wide temperature range. In addition IF -WS2 pellets were annealed at elevated temperatures under vacuum in a specially designed system. Arrhenius plots for the conductivities of the WS2 samples (2H, IF and IF +annealing) exhibit marked uprise of ∂ ln (sT–1)/∂T–1 with temperature. The resistivity of the non-annealed IF -WS2 pellets is higher by 2–8 orders of magnitude than that of 2H-WS2 pellets, whereas the resistivity of the annealed IF pellets is higher than that of the non-annealed ones. Hall Effect measurements at 300 K show p-type conductivity and similar carrier concentration for both types of materials. The carrier mobility of 2H-WS2 platelets is found to be in the range of the reported values. However, IF -WS2 pellets have shown an unusually low mobility for a semiconducting material. The experimental data was found to be in a good agreement with a model used for analyzing the conductivity of polycrystalline semiconductors, which takes into consideration fluctuations of the barrier heights among the different nanoparticles as well as within a single nanoparticle boundary. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
35 citations
TL;DR: In this paper, the authors present Hall effect measurements on pyrolytic graphite that indicate the occurrence of the integer quantum-Hall-effect and show that the quasi-linear and non-saturating longitudinal magnetoresistance in graphite is governed by the Hall effect in agreement with a recent theoretical model for disordered semiconductors.
34 citations
TL;DR: In this article, the surface composition of all samples differed considerably from the stoichiometric value with an important segregation of strontium and mainly ruthenium with regard to chromium at the surface of the catalysts.
Abstract: Perovskite type catalysts La 0.7 Sr 0.3 Cr 1− x Ru x O 3 (0.025 ≤ x ≤ 0.100) were synthesized by annealing a mixture of metal oxides and carbonates gradually up to 1000 °C in air, and characterized by XRPD, XPS, TPD, SEM-EDS and the van der Pauw method. The CO oxidation activity was investigated in a differential recycle reactor. According to the XRPD results, all samples achieved a perovskite structure, with a small presence of SrCrO 4 phase. The XPS results revealed that the surface composition of all samples differed considerably from the stoichiometric value with an important segregation of strontium and mainly ruthenium with regard to chromium at the surface of the catalysts. The sharp decrease of resistivity with increasing surface concentration of ruthenium and the independence of the resistivity on temperature for the sample with x = 0.100 imply the possible presence of SrRuO 3 , La–Ru–O and highly dispersed RuO 2 (invisible by XRPD), known as good electric conductors, at the surface. The CO oxidation activity increases with increasing the degree of substitution ( x ). The surface concentrations of ruthenium are almost the same in the samples with x = 0.075 and 0.100. Those samples showed the similar values of resistivity in whole investigated temperature range and very close CO oxidation activity, which indicates that the concentration of Ru 4+ in the surface region and its stability are determining factors for the CO oxidation activity. The main results of this study are that ruthenium perovskites have a high thermal stability and CO oxidation activity.
31 citations
TL;DR: In this article, amorphous ZnO thin films were obtained by direct UV irradiation of β-diketonate Zn(II) precursor complexes spin-coated on Si(1−0−0) and fused silica substrates.
Abstract: In this paper, amorphous ZnO thin films were obtained by direct UV irradiation of β-diketonate Zn(II) precursor complexes spin-coated on Si(1 0 0) and fused silica substrates. ZnO films were characterized by means of XPS, X-ray diffraction (XRD) and Atomic Force Microscopy (AFM). These analyses revealed that as-deposited films are amorphous and have a rougher surface than thermally treated films. Optical characterization of the films showed that these are highly transparent in the visible spectrum with an average transmittance of up to 95% over 400 nm, and an optical band-gap energy of 3.21 eV for an as-deposited film, and 3.27 eV for a film annealed at 800 °C. Low resistivity values were obtained for the ZnO films (1.0 × 10−2 Ω cm) as determined by Van der Pauw four-point probe method.
27 citations
TL;DR: In this article, an alumina-encapsulated microcircuit on a diamond anvil for high-pressure and high-temperature electrical conductivity measurement is reported, which significantly improves the laser heating performance.
Abstract: We report an alumina-encapsulated microcircuit on a diamond anvil for high-pressure and high-temperature electrical conductivity measurement. An alumina thin film was deposited on a diamond anvil as a thermal insulation layer for laser heating, on which a molybdenum film was deposited and photolithographically fabricated to a van der Pauw circuit. The introduction of the alumina layer significantly improves the laser heating performance. This specially fabricated diamond anvil permits us to measure the resistivity of (Mg0.875Fe0.125)2SiO4 at 3450K and 35GPa in a laser-heated diamond anvil cell. We expect to substantially extend the pressure-temperature scale of in situ resistivity measurement.
25 citations
14 Nov 2006-Microsystem Technologies-micro-and Nanosystems-information Storage and Processing Systems
TL;DR: In this article, the structural transformation and transformation kinetics of Sb x Se100−x films were studied to investigate the feasibility of applying Sbx Se 100−x alloys in phase-change nonvolatile memories.
Abstract: The structural transformation and transformation kinetics of Sb x Se100−x films (60 ≤ x ≤ 70) were studied to investigate the feasibility of applying Sb x Se100−x alloys in phase-change nonvolatile memories. The temperature-dependent van der Pauw measurements, Hall measurements, X-ray diffraction and a static tester were used to investigate the electrical properties and crystallization behavior of the Sb x Se100−x films. The sheet resistance difference between amorphous and crystalline state was higher than 104 Ω per square According to Hall measurement, Sb x Se100−x films have p-type conduction and the Hall mobility and carrier concentration increases with the increase in Sb content. The crystalline structure of the metastable phase of Sb x Se100−x alloys, which plays a major roll in fast crystallization, is similar to that of Sb2Te (rhombohedral structure). The transition temperature, sheet resistance and activation energy for transformation decrease as the amount of Sb increases in the Sb x Se100−x film. Applying the Kissinger method, the activation energies for crystallization were in the range from 1.90 ± 0.15 to 4.16 ± 0.28 eV. The desired crystallization speed can be obtained by a systematic change of the composition owing to the variation of the activation barrier with stoichiometry.
22 citations
TL;DR: In this article, Cadmium telluride (CdTe) thin films were deposited onto scratch-free transparent glass substrates by the two-source evaporation technique, using Cd and Te as two different evaporants.
Abstract: Cadmium telluride (CdTe) thin films were deposited onto scratch-free transparent glass substrates by the two-source evaporation technique, using Cd and Te as two different evaporants. In the next step, films were heated under vacuum at 500 ?C for 1 h and dipped in Cu(NO3)2?H2O solution at room temperature. These films were again heated under vacuum for 1 h at 500 ?C to obtain maximum Cu diffusion. The samples were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), optically by a Lambda 900 UV/VIS/NIR spectrophotometer and electrically, i.e. dc electrical resistivity, by the van der Pauw method at room temperature, dark conductivity, and activation energy analysis as a function of temperature by the two-probe method under vacuum. The EDX results showed an increase of Cu content in the samples by increasing the immersion time of the CdTe films in the solution. The layer thickness of diffused Cu atoms in CdTe is determined by comparing the difference of absorption between as-deposited and immersed films with the absorption graph of Cu films of varying thicknesses.
TL;DR: A model provides good agreement with the experimental data and clearly demonstrates the geometry dependence of the field effect in extraordinary electroconductance (EEC), which results from the thermionic field emission of electrons and the geometrical amplification.
Abstract: We provide the first demonstration of extraordinary optoconductance (EOC) in macroscopic metal-semiconductor hybrid structures fabricated from GaAs and In and the first example of an extraordinary transport (EXX) effect that is based on a perturbation of the relative bulk conductances of the constituents. Four-lead van der Pauw plate structures show a gain of order 500% in the optocondutance when shunted by In relative to unshunted devices. The dependence of the optocondutance on the position of a focussed Ar laser beam has been measured and is in agreement with a Gaussian broadened point charge model that accounts for the Dember effect. We also account quantitatively for the temperature dependence of the EOC.
TL;DR: In this article, the authors report on the electrical characterization of conductive polyaniline and its derivatives and conductivity measurements were also performed on the intercalated phases formed by the encapsulation of the polymers into layered molybdenum disulfide.
TL;DR: In this article, the structural, photo-electronic, optical and electrical properties of doped and undoped SnO2 thin films were studied by measuring their optical transmission as a function of wavelength.
Abstract: Stannous oxide (SnO2) thin film is one of the most widely used n-type transparent semi-conductor films in electronics, electro-optics and solar energy conversion. By achieving controlled non-stoichiometry, we can get good transparency and high electrical conductivity simultaneously in SnO2 thin films. Dy and La doped SnO2 thin films have been prepared by a cost effective vapour deposition technique. The structural, photo-electronic, optical and electrical properties of the doped and undoped films were studied. The results of X-ray Diffraction studies reveals the polycrystalline nature of the films with preferential orientation along the (101), (211) and (301) planes and their average grain size variation for different deposition temperature. Photoconductivity and Photovoltaic studies of the films were also performed. The optical properties of these films were studied by measuring their optical transmission as a function of wavelength. The optical transmission is found to be increased on Dy doping and decreased on La doping. The band gap, refractive index and thickness of the films were calculated from U-V transmittance and Absorption graphs. The optical band gap of undoped film is found to be 4.08 eV, but on doping it shifts to lower energies and then increases on increasing the concentration of both dopants. Its electrical parameters such as sheet resistance, resistivity, mobility, Hall coefficient, and carrier concentration were determined by Four Probe, Van der Pauw and Hall Probe method. On doping with Dy, carrier conversion takes place from n-type to p-type and p-conductivity dominates. On La doping no carrier conversion takes place but resistivity decreases. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
TL;DR: A two-sourced evaporation technique was used for deposition of cadmium telluride thin films onto scratch-free transparent glass substrates, using Cd and Te as two different evaporants as mentioned in this paper.
Abstract: A two-sourced evaporation technique was used for deposition of cadmium telluride thin films onto scratch-free transparent glass substrates, using Cd and Te as two different evaporants. Nine samples were deposited at three Te evaporation rates, that is, 6.5, 4.5, and 2.5 nm/s as a function of three substrate temperatures at 400, 300, and 200 °C respectively, keeping the Cd evaporation rate fixed at 2.7 nm/s. All the samples were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM), optically by Lambda 900 UV/vis/NIR spectrophotometer and electrically, that is, DC electrical resistivity, by the van der Pauw method at room temperature. Content composition was investigated by energy-dispersive X-ray analysis. Strong mutually supporting effects on structure, morphology, optical transmission, reflection, and electrical resistivity were observed.
TL;DR: In this article, the dependence of van der Pauw resistivity measurements on local macroscopic inhomogeneities is shown to be nonlinear, and an empirical nonlinear correction for f(x,y) is presented which provides excellent fit over the entire range of both positive and negative perturbations for the entire specimen.
Abstract: The dependence of van der Pauw resistivity measurements on local macroscopic inhomogeneities is shown to be nonlinear. A resistor grid network models a square laminar specimen, enabling the investigation of both positive and negative local perturbations in resistivity. The effect of inhomogeneity is measured both experimentally, for an 11×11 grid, and computationally, for both 11×11 and 101×101 grids. The maximum “shortlike” perturbation produces 3.1±0.2 times the effect predicted by the linear approximation, regardless of its position within the specimen, while all “openlike” perturbations produce a smaller effect than predicted. An empirical nonlinear correction for f(x,y) is presented which provides excellent fit over the entire range of both positive and negative perturbations for the entire specimen.
TL;DR: In this article, a sacrificial porous silicon layer on both sides of the silicon substrates with randomly hemispherical voids was created for extrinsic and intrinsic gettering.
TL;DR: In this paper, the effects of reactive ion etching (RIE) of sputtered tungsten films, a suitable candidate for gate metallization in compound semiconductor based high mobility channel devices, with the aim of developing a detailed understanding of the effect of etching parameters vital to reducing etch-induced damage and improving etching performance, yield, uniformity and repeatability were investigated.
TL;DR: In this article, a 10nm n-type PbTe / Pb 0.9 Eu 0.1 Te quantum well at millikelvin temperatures was measured in a Van der Pauw geometry under high magnetic fields up to 23 T. A robust signature of integer quantum Hall effect was observed without any sign of parasitic parallel conduction.
Abstract: Transport measurements have been carried out on a 10 nm n-type PbTe / Pb 0.9 Eu 0.1 Te quantum well at millikelvin temperatures. The Hall and longitudinal resistances are measured in a Van der Pauw geometry under high magnetic fields up to 23 T. A robust signature of the integer quantum Hall effect is observed without any sign of parasitic parallel conduction. The unconventional sequence of filling factors associated with the integer quantum Hall effect is discussed in terms of the occupancy of multiple valleys.
TL;DR: In this article, the 2-wt% aluminum-doped zinc oxide films (AZO) were sputtered on corning glass plate at temperatures of 30-200°C by DC magnetron sputtering using ceramic target.
TL;DR: In this paper, lattice mismatched layers of InxGa1−xAsySb1−y with band edge corresponding to a wavelength of 109μm have been grown on GaAs substrates using a self-graded compositionally organized near-equilibrium growth process based on quaternary melt thermochemistry.
Abstract: Lattice mismatched layers of InxGa1−xAsySb1−y with band edge corresponding to a wavelength of 109μm have been grown on GaAs substrates using a self-graded compositionally organized near-equilibrium growth process based on quaternary melt thermochemistry A variable composition quaternary acts as a buffer layer between the GaAs substrate and the final layer of uniform composition Layers of a constant composition with thicknesses as high as 100μm have been achieved The dislocation densities in the layers are as low as 8×105cm−2 even for a lattice mismatch of 1308% van der Pauw measurements showed room temperature electron mobility as high as 14×104cm2∕Vs and carrier concentration of 42×1016cm−3 With further optimization in the growth conditions and improvements in the material quality, the grown layers are expected to be suitable for infrared optoelectronics, high speed electronic devices, and magnetoresistive sensors
TL;DR: The resistivity of the annealed ZnO films was determined by the Van der Pauw measurement technique, and a pH between 4 and 5 is found to be optimum for film deposition.
Abstract: Ag alvanic technique for the deposition of ZnO thin films is reported. The depositions were carried out on p-type single-crystal silicon substrates at room temperature, from a solution of ZnSO4 ,w here the Zn rod acted as a sacrificing anode and p-Si was the cathode. The deposition of ZnO by this method is pH sensitive, and a pH between 4 and 5 is found to be optimum for film deposition. This deposition technique is simple, inexpensive and can be carried out at room temperature. X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies revealed the nanocrystalline structure of the films. The resistivity of the annealed ZnO films was determined by the Van der Pauw measurement technique.
TL;DR: In this paper, the electrical and optical properties of n-type CdGeAs2 crystals doped with indium have been studied at room temperature using van der Pauw Hall measurements, infrared absorption, and infrared reflectance.
Abstract: The electrical and optical properties of n-type CdGeAs2 crystals doped with indium have been studied at room temperature using van der Pauw Hall measurements, infrared absorption, and infrared reflectance. Free-electron concentrations (n) in the sample set range from 2.3 ? 1017 to 4.3 ? 1018?cm?3 at 300?K. For the higher levels of free carriers, conduction-band non-parabolicity causes significant increases in electron effective mass m*. Infrared absorption due to free carriers is consistent with ionized impurity scattering, and absorption coefficients ?f for different samples agree with theoretical predictions when the dependence of m* on n is included. A relation between ?f and n has been determined for CdGeAs2:In that can be applied to large-sized samples used in nonlinear optical applications. The optical effective mass mopt* obtained from reflectance data is also in good agreement with predicted m* values for CdGeAs2.
TL;DR: In this paper, a linear correlation between absorption at 5.5μm and hole concentration (p) was established, and the variation in activation energy with p, and also with NA and find excellent agreement with theory.
Abstract: CdGeAs2 crystals typically exhibit an absorption band near 5.5μm that limits their use as a nonlinear frequency-conversion material in high-power infrared laser systems. This absorption band is related to the p-type nature of the as-grown bulk crystals. We correlate the electrical properties, as determined using van der Pauw Hall measurements, with optical absorption and photoluminescence data. The samples are all p type at room temperature with hole concentrations varying from 1×1015to2×1017cm−3. High-absorption samples have two acceptor levels, while low-absorption samples have one deep acceptor. A linear correlation between absorption at 5.5μm and hole concentration (p) is established. Also, we account for ambipolar conduction and explain possible discrepancies which may arise when comparing hole concentrations and optical data in low-absorption CdGeAs2 samples. We correlate the variation in activation energy with p, and also with NA and find excellent agreement with theory. An ionization energy is obt...
TL;DR: The relationship between the densities of residual carriers and those of dislocation in GaSb films grown on Si substrates was investigated by cross-sectional transmission electron microscopy (TEM) images as discussed by the authors.
TL;DR: In this article, the authors investigated the performance of p-type doped SiC wafers grown by the Modified- Physical Vapor Transport (M-PVT) method.
Abstract: We report on investigation of p-type doped, SiC wafers grown by the Modified- Physical Vapor Transport (M-PVT) method. SIMS measurements give Al concentrations in the range 1018 to 1020 cm-3, with weak Ti concentration but large N compensation. To measure the wafers’ resistivity, carrier concentration and mobility, temperature-dependant Hall effect measurements have been made in the range 100-850 K using the Van der Pauw method. The temperature dependence of the mobility suggests higher Al concentration, and higher compensation, than estimated from SIMS. Additional LTPL measurements show no evidence of additional impurities in the range of investigation, but suggest that the additional compensation may come from an increased concentration of non-radiative centers.
01 Oct 2006
TL;DR: In this article, the authors measured the optical, MCL and deep traps spectra of TlBr and found that the concentration of deep traps increased dramatically upon adding a small amount of Br into the ampoule with constituent components.
Abstract: Electrophysical characteristics were measured for TlBr crystals grown by Bridgman technique in various ambients: vacuum, Ar, air, Br. The dark resistivity of the crystals measured by Van der Pauw method was (1.0-2.3) times 1010 Ohmmiddotcm at 18 degC. The growth ambient had a profound influence on optical, MCL and deep traps spectra of TlBr, but not on the position of the Fermi level pinned around 0.80-0.85 eV from the valence band edge. The major traps had activation energies of 0.60, 0.50, 0.36, 0.27 and 0.19 eV. Crystals grown in vacuum showed the highest concentration of deep traps while the lowest density of traps was detected in the ingots grown in air. The concentration of deep traps was found to decrease dramatically upon addition of a small amount of Br into the ampoule with constituent components. However, when the amount of Br was increased, the direction of the crystal parameters changes was ambiguous. We assume that this is due to the formation of the second phase of TlBr3. MCL spectra measured at 95 K showed the presence of 2.98 and 2.70 eV exciton lines and of wide defect bands at 2.46 eV, 2.25 eV and 1.90 eV.
TL;DR: In this paper, a high resolution, low damage dry etching of tungsten, a suitable candidate for gate metallization in compound semiconductor based high mobility channel device, by using a Surface Technology Systems Ltd. (STS) inductively coupled plasma (ICP) etching system with SF"6 and C"4F"8 process gases was investigated.
TL;DR: In this paper, electric transport properties measured by Van der Pauw resistivity experiments of Low-Temperature Molecular Beam Epitaxy (LT-MBE) GaAs samples are used to identify a method to improve the resistivity of GaAs material.
Abstract: Electric transport properties measured by Van der Pauw resistivity experiments of Low-Temperature Molecular Beam Epitaxy (LT-MBE) GaAs samples are used to identify a method to improve the resistivity of GaAs material. We present results on five samples grown at 265, 310, 315, 325, and 345 oC. The electric measurements were carried out at temperatures ranging from 130 to 300 K. In this temperature range the dominant transport process is identified as variable range hopping. The hopping parameter plotted against the growth temperature is shown to present a maximum. The mechanisms responsible for this behavior are discussed in relation to the compensation ratio.
TL;DR: In this article, a tin dioxide (FTO) film was deposited on silicon wafers by inverted pyrosol technique using solutions with different doping concentration (F/Sn=0.00, 0.12,0.75 and 2.50) and the physical and electrical properties of the deposited films were analyzed by SEM, XRF, resistivity measurement by four-point probe method and Hall coefficient measurement by van der Pauw method.
Abstract: Fluorine-doped tin dioxide (FTO) films were deposited on silicon wafers by inverted pyrosol technique using solutions with different doping concentration (F/Sn=0.00, 0.12, 0.75 and 2.50). The physical and electrical properties of the deposited films were analyzed by SEM, XRF, resistivity measurement by four-point-probe method and Hall coefficient measurement by van der Pauw method. The electrical properties showed that the FTO film deposited using the solution with F/Sn=0.75 gave a lowest resistivity of 3.2·10–4 ohm cm. The FTO films were analyzed by temperature programmed desorption (TPD). Evolved gases from the heated specimens were detected using a quadruple mass analyzer for mass fragments m/z, 1(H+), 2(H2+), 12(C+), 14(N+), 15(CH3+), 16(O+), 17(OH+ or NH3+), 18(H2O+ or NH4+), 19(F+), 20(HF+), 28(CO+ or N2+), 32(O2+), 37(NH4F+), 44(CO2+), 120(Sn+), 136(SnO+) and 152(SnO2+). The majority of evolved gases from all FTO films were water vapor, carbon monoxide and carbon dioxide. Fluorine (m/z 19) was detected only in doped films and its intensity was very strong for highly-doped films at temperature above 400°C.