Common sample geometries. (a) Preferred geometry for four-probe resistivity measurements, (b) common geometry for a Hall effect measurement, resistance measurements, (c) and (d) arbitrarily shaped lamella for VDP measurements showing contact arrangements for two resistance measurements, and (e) contact arrangement for a Hall effect measurement with the VDP method. The arrow in the bottom right corner indicates the positive direction of the magnetic field in panels (b) and (e).
Illustration of the sample holder. (a) The sample is mounted on a heated plate inside a heat shield. Two rods can be used to fix the sample holder between the poles of the electromagnet (not shown). (b) Zoom on the post-and-screw design. When the metal rods are pressed against the sample they bend elastically. This ensures good electrical contact during thermal expansion. The other end of the rods are either pressed against metal pads or connected directly to wires, in which case the pads are unnecessary. Both methods are shown for comparison.
I-V curve for metal contacts showing no Shottky anomaly. The current range, 0−500 mA, covers the currents typically used. The inset shows a zoom on the low current data to emphasize the absence of a Shottky anomaly. The sample used is n-type intrinsic Mg2Si with n ∼ 2.8 × 10−18 cm−3. Molybdenum has been chosen for the contacts.
Example of a measurement of (a) Hall carrier concentration, (b) Hall mobility and (c) electrical resistivity. The data were measured during heating and cooling to 600 °C on both the Caltech (squares) and Aarhus (line) setups. The sample is doped PbS.
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