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, a method for contact-free determination of the sheet resistance of large area and arbitrary shaped wafers or sheets coated with graphene and other (semi) conducting ultrathin layers is described, which is based on an open dielectric loaded microwave cavity.
Abstract: A method for contact-free determination of the sheet resistance of large-area and arbitrary shaped wafers or sheets coated with graphene and other (semi) conducting ultrathin layers is described, which is based on an open dielectric loaded microwave cavity. The sample under test is exposed to the evanescent resonant field outside the cavity. A comparison with a closed cavity configuration revealed that radiation losses have no significant influence of the experimental results. Moreover, the microwave sheet resistance results show good agreement with the dc conductivity determined by four-probe van der Pauw measurements on a set of CVD samples transferred on quartz. As an example of a practical application, correlations between the sheet resistance and deposition conditions for CVD graphene transferred on quartz wafers are described. Our method has a high potential as measurement standard for contact-free sheet resistance measurement and mapping of large area graphene samples.
32 citations
TL;DR: The evaporation technique combined with simultaneous heating of the glass leads to change of the sheet resistance, surface roughness, and optical properties of gold nanostructures.
Abstract: The paper is focused on the preparation and surface characterization of gold coatings and nanostructures deposited on glass substrate. Different approaches for the layer preparation were applied. The gold was deposited on the glass with (i) room temperature, (ii) glass heated to 300°C, and (iii) the room temperature-deposited glass which was consequently annealed to 300°C. The sheet resistance and concentration of free carriers were determined by the van der Pauw method. Surface morphology was characterized using an atomic force microscopy. The optical properties of gold nanostructures were measured by UV–vis spectroscopy. The evaporation technique combined with simultaneous heating of the glass leads to change of the sheet resistance, surface roughness, and optical properties of gold nanostructures. The electrically continuous layers are formed for significantly higher thickness (18 nm), if the substrate is heated during evaporation process. The annealing process influences both the structure and optical properties of gold nanostructures. The elevated temperature of glass during evaporation amplifies the peak of plasmon resonance in the structures, the surface morphology being significantly altered.
32 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, the influence of microstructure on the gas sensing characteristics of ZnO thin films was investigated using MOCVD growth technique using diethyl zinc and tert-butanol as zinc and oxygen precursors.
Abstract: The present work is aimed to investigate the influence of microstructure on the gas sensing characteristics of ZnO thin films. By controlling the deposition parameters we have successfully grown ZnO thin films of different microstructures on quartz substrates by MOCVD growth technique using diethyl zinc and tert-butanol as zinc and oxygen precursors, respectively. X-ray diffraction pattern shows that the films are textured along (0 0 2) plane. FESEM images reveal the uniform deposition of fine grains with varying microstructures. Growth mode dependent microstructure formation is explained on the basis of a simple model. The optical characterization reveals that the films are transparent in the visible range with band gap energy in the range 3.234–3.217 eV. The effect of microstructure on the electrical parameters of the ZnO such as carrier concentration, resistivity and Hall mobility is understood through Hall effect measurement using standard Van der Pauw geometry. The gas sensing characteristics of the grown films is investigated as a function of temperature and gas concentration in CO test gas environment. The observed results are analyzed on the basis of the variation of microstructures of the grown films.
32 citations
TL;DR: The van der Pauw technique was used to measure the electrical resistivity of the samples at temperatures between 4.2 and 300 K and the Hall coefficient at room temperature and the Drude parameters obtained are in good agreement with those obtained from the optical data.
Abstract: Optical and electrical properties are reported for single-crystalline ${\mathrm{ZrC}}_{0.89}$. The specular reflectance was measured between 0.025 and 6.5 eV, and ellipsometry measurements were made between 1.2 and 4.5 eV. The combination of ellipsometry with reflectance allows optical functions to be computed reliably between 0 and 6.5 eV and also provides a check on the consistency of the measurements. The van der Pauw technique was used to measure the electrical resistivity of the samples at temperatures between 4.2 and 300 K and the Hall coefficient at room temperature. Drude parameters obtained from the electrical measurements are in good agreement with those obtained from the optical data. Both the optical and electrical results are compared to other experimental results and to theory.
32 citations