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.

Application of the van der Pauw Methodto Conductivity Relaxation Experimentson YBa2Cu3O6+δ

Abstract: The van der Pauw method has been applied to conductivity relaxation experiments on YBa2Cu3O6+δ at 600°C in order to determine the chemical diffusion coefficient as a function of the oxygen partial pressure in the surrounding atmosphere (100 > p O 2/bar > 10−3). It is shown that the van der Pauw technique is suitable for monitoring the conductivity relaxation when the oxygen diffusion is perpendicular to the direct current flowing through the sample in accordance with the van der Pauw geometry using thin tablets as samples. The oxygen partial pressure is changed stepwise (generally Δlogp O 2 ≤ 0.5) by employing appropriate gas mixtures as well as an electrochemical oxygen pump device. An evaluation formula is given for the determination of the chemical diffusion coefficient neglecting slow surface processes. In addition, the electronic conductivity of YBa2Cu3O6+δ has been measured at 600°C as a function of oxygen partial pressure of the ambient atmosphere (100 > p O 2/bar > 10−5) by means of the van der Pauw method applying the same experimental set-up. Typical values of the chemical diffusion coefficient are in the range of 10−6 cm2·s−1; the results of the conductivity measurements are interpreted in terms of an appropriate defect model.

Hydrogen Dissociation from Mg-doped GaN

Abstract: We have investigated the thermal activation process of Mg dopant in Mg-doped GaN by secondary ion mass spectrometry (SIMS) and Hall measurement with the van der Pauw configuration. We have found a systematic relationship between the amount of the hydrogen dissociated from the Mg-doped GaN layer by thermal annealing and the electronic conductive properties of the layer, i.e., Hall mobility, Hall carrier density and resistivity of the layer. The hydrogen in the Mg-doped GaN layer has been classified into at least two different modes. The first mode involves relatively larger activation energy of the dissociation process from the Mg-doped GaN layer, and the dissociation energy from the Mg-doped GaN to the atmosphere is 0.8–1.5 eV. The second mode has the dissociation energy of 0.2–0.5 eV. The former mode may be associate with the hydrogen passivation of the Mg dopant in GaN and the latter one may be closely related to the passivation of the electrical compensation mechanism for the positive hole carriers in the Mg-doped GaN.

In situ four-point conductivity and Hall effect apparatus for vacuum and controlled atmosphere measurements of thin film materials

Abstract: An ultrahigh vacuum (UHV) chamber equipped with a fixture for in situ four-point Van Der Pauw conductivity and Hall effect measurements has been constructed and attached to a multichamber thin film synthesis and characterization system. The combined systems allow for film synthesis and characterization of microstructure, chemical composition, morphology, and electronic transport properties without air exposure. The four-point measurement fixture features spring-loaded probes for electrical contacts and temperature measurement and a sample docking mechanism designed to minimize probe damage to the films. The electronics were designed for measurement of high resistance samples. Measurements can be made at sample temperatures from 25 to 450 °C in selected gas environments from UHV to atmospheric pressure. The design and performance of the system are reported, and representative results on the electronic transport properties of n-type Si (100) and tungsten oxide films on sapphire are presented.