Topic
Van der Pauw method
About: Van der Pauw method is a research topic. Over the lifetime, 1682 publications have been published within this topic receiving 25364 citations.
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TL;DR: In this article, NiO was resistively deposited on glass substrates and oxidised (isochronally) in oxygen at temperatures ranging from 300 °C to 600 °C. The oxidised NiO layers were subsequently characterised using scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-visible photospectrometry in the range 200 nm - 1000 nm.
Abstract: Nickel oxide (NiO) is a versatile wide band gap semiconductor material. At present, transparent conducting oxide films find application as transparent electrodes and window coatings for opto-electronic devices but most are n-type. However p-type conducting films, of which NiO is one, are required as optical windows for devices where minority carrier injection is required. In this study, nickel (Ni) was resistively deposited on glass substrates and oxidised (isochronally) in oxygen at temperatures ranging from 300 °C to 600 °C. The oxidised Ni layers were subsequently characterised using scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-visible photospectrometry in the range 200 nm - 1000 nm. The four point probe method (van der Pauw geometry) was used to determine the sheet resistances of the oxidised films. SEM results of the surface revealed a strong dependence of the surface texture and particle size on the oxidation temperature and time. XRD performed on the oxidised Ni indicated progressive transformation from nanograined polycrystalline Ni to NiO at elevated temperatures. Film thicknesses, particle sizes, energy band gap and wavelength-dependent refractive indices were determined from transmission and absorbance data.
11 citations
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.
11 citations
TL;DR: In this paper, the electrical and optical properties of single crystals of Europium compounds were investigated using the van der Pauw technique, and the thermal activation energies observed were attributed to impurity effects.
11 citations
01 May 2009-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, the authors improved the figure of merit of the single layer of Er 0.1 Fe 1.9 SbGe 0.4 thin film used as thermoelectric generators.
Abstract: Effective thermoelectric materials and devices have a low thermal conductivity and a high electrical conductivity. The performance of the thermoelectric materials and devices is shown by a dimensionless figure of merit, ZT. The purpose of this study is to improve the figure of merit of the single layer of Er 0.1 Fe 1.9 SbGe 0.4 thin film used as thermoelectric generators. We have deposited the monolayer of Er 0.1 Fe 1.9 SbGe 0.4 thin film on silicon and silica substrates with thickness of 302 nm using ion beam assisted deposition (IBAD). Rutherford backscattering spectrometry (RBS) was used to determine the total film thickness and stoichiometry. The MeV Si ion bombardments were performed on single layer of Er 0.1 Fe 1.9 SbGe 0.4 thin films at five different fluences between 5 × 10 13 −5 × 10 15 ions/cm 2 .The defect and disorder in the lattice caused by ion beam modification and the grain boundaries of these nanoscale clusters increase phonon scattering and increase the chance of annihilation of the phonon. The increase of the electron density of states in the miniband of the quantum dot structure formed by bombardment also increases the Seebeck coefficient and the electrical conductivity. We measured the thermoelectric efficiency of the fabricated device by measuring the cross plane thermal conductivity by the 3rd harmonic (3 ω ) method, the cross plane Seebeck coefficient, and the electrical conductivity using the Van Der Pauw method before and after the MeV ion bombardments.
11 citations
TL;DR: In this paper, the authors studied the optical and electrical properties of Tb films as a function of hydrogen concentration and obtained the complex refractive index of the Tb film's complex dielectric function, e1 and e2.
Abstract: The absorption of hydrogen in the rare earth metals produces interesting changes in their optical and electrical properties. In this work we study these properties on Tb films, 50 nm thick, as a function of hydrogen concentration. The Tb films are covered with a 15 nm thick Pd overcoat which allows hydrogenation while protecting the highly reactive Tb film from contamination. Electrical resistivity is measured using the van der Pauw method, the transmission spectra are measured in the visible region and the concentration using a quartz crystal microbalance. The maximum concentration reached was 2.95 H/Tb at a hydrogen pressure of 450 Torr. From the measured transmission spectra, using a Spectral Projected Gradient Method, we obtain the Tb film's complex refractive index. From this we calculate the real and imaginary parts of the dielectric function, e1 and e2, and follow their evolution as a function of hydrogen concentration. e1 changes from negative values, characteristic of metals, to positive values characteristic of semiconductors and dielectrics. e2 decreases indicating a significant decrease in light absorption. These results are similar to those observed on Dy, Gd, La and Y films. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
11 citations