Resistivity measurement setup

In general, the sheet resistivity can be expressed as: where the factor k is a geometric factor. Operation Procedures The following steps should be taken in the following sequence: Turn on the voltmeter, set the mode to DC and voltage range to mV. Place wafer onto the probe stage. Watch the probe casing lower until the probes stabilize on the wafer. Set the current to the desired level, and proceed with measuring the voltage across the inner two probes.

Map the wafer. Turn off voltmeter. Hall voltage versus magnetic field for two Ag thin films at room temperature. The slope of fitted lines is used for computation of the Hall coefficient.

Corresponding errors in fitted slopes are 2. Hall coefficient versus temperature for thin-film samples of the high- Tc superconductor YBCO, with different doping. A limited amount of points was measured in each curve due to the long time taken by each measurement. Nevertheless, we obtain reliable data with very small noise that can be used for analysis of these curves, as required in the computation of transport coefficients. These data present a good linear behavior for all samples with different doping, as observed in high-Tc superconductors by several authors.

An appropriate normalization of the data made all curves coalesce into a single line. Since the purpose of this report is not to study the physics of our measurements, we refer the interested reader to a discussion of these results presented elsewhere [3], [10]. Hall voltage versus inverse temperature for thin-film samples of the high-Tc superconductor YBCO, with different doping. Hole carrier doping A. Final Remarks is indicated by an arbitrary index ranging from 0.

Good linear dependence, with small fluctuations, is observed A point worth mentioning is that our setup is able to measure even in the most overdoped sample bottom curve. These results agree with measurements reported by other authors. In the literature of high-Tc supercon- functional dependence on temperature.

Fixing instrumentation prob- lems is made easy by allowing a follow-up of signals through each step of the system. Precision and quality measurements are guaranteed by the quality of component instruments and quality of samples.

This setup can be used in industrial and scientific applications with different samples like semiconductors, met- als, and superconductors. A detailed description of instruments and measurement methodology has been presented.

Two such systems have already been built in different institutions and are actually being used in scientific research [3], [10].

Normalized Hall cotangent versus temperature squared for thin-film For the square sample and contact numbering shown in samples of the high-Tc superconductor YBCO, with different doping.

A robust Fig. Appropriate normalization makes all lines coalesce into a single line. However, this practice reduces the These values have to obey the following conditions: precision of measurements due to the inherent low resolution of high current supplies.

A remarkable constacts or instrumentation problems. Once these relationships reduction of fluctuations in Hall coefficient measurement has are verified, we compute resistivity in the following way.

First, been obtained by computing it from a linear fit of the Hall define the average resistances in the two perpendicular di- voltage versus the magnetic field, which has been measured at rections, i. Our method offers the advantage of more transparent study of samples, in addition to the possibility of The resistivity of the sample is computed by solving Van der using them in further tests or directly for applications.

Following contact numbering of Fig. It is possible to improve these figures by a more careful design and by improving sample Inversion of the magnetic field polarity and subtraction of both preparation and connection techniques.

A checkout of individual measurements collaboration. Vij must be performed to verify the validity of 5 — 7. AAPT , vol. Ashcroft and N. Mermin, Solid State Physics, Int. Orlando, FL: Saunders College, , cp 1 and Castro and G. B, Condens. Matter, vol. New York: Plenum, This is a list of the instruments that are used in this setup. Schroder, Semiconductor Material and Device Characterization, availability.

Hoboken, NJ: Wiley, , pp. Castro and L. C, vol. New York: Plenum, , pp. This paper presents a setup for measuring the Seebeck coefficient and the electrical resistivity of bulk thermoelectric materials. The sample holder was designed to have a compact structure and can be directly mounted in a standard cryostat system for temperature-dependent measurements. For the Seebeck coefficient measurement, a thin bar-shaped sample is mounted bridging two copper bases; and two ceramic heaters are used to generate a temperature gradient along the sample.

Two type T thermocouples are used to determine both temperature and voltage differences between two widely separated points on the sample.