Room Temperature Hall Effect System
Demonstrate and Measure the Hall Effect

Optimized for Demonstrating the Hall Effect

Accommodates TeachSpin Silicon and Copper Samples

Permanentmagnet structure provides reversible Bfield

Transparent connections for tracking polarity

Unambiguously gives sign of charge carriers for n and ptype Si and Cu

Permits 4wire measurement of resistivity in semiconductors

Comes with currentlimiting resistor and currentreversing switch

Guides students to firstprinciples measurements of sign and magnitude of Bfield
Introduction
The Hall Effect is the standard method for determining the absolute sign, and the number density, of charge carriers in a conductor. TeachSpin now offers, in support of its CondensedMatter Physics initiative, a unique educational system that allows students to see, in the same apparatus, the Hall Effect in both semiconductor and in metal samples.
Measuring the Hall Effect requires a sample of known thickness t, conducting a sample current i, immersed in a transverse magnetic field B. The detectable effect is a potential difference ΔV, arising perpendicular to both the field and the current, of a magnitude
Here n is the number density (number per unit volume) of the mobile charge carriers. TeachSpin’s apparatus is devised to make n measurable over the huge range that spans metal and semiconductor samples.
The R.T. HallEffect system is crafted to use the same mounted and packaged semiconductor samples used in the CMP ElectricalTransport experiment, and it also accommodates thinfilm copper samples laid out in an identical format. The system is also uniquely ‘transparent’, permitting students to trace every electrical lead in 3d space, as is required for deducing the absolute sign of the charge of the mobile carriers.
Our system offers a firstprinciples method for establishing the absolute direction of the magnetic field B in its two field regions, and another firstprinciples method for establishing the magnitude of the field B (about 0.6 Tesla, or 6000 gauss) in the field regions.
Our samples offer preciselyspecified geometry of the samples, and have enough electrical contacts to permit measurement of longitudinal, as well as transverse, potential differences. For semiconductor samples of known thickness, this permits an absolute and fourwire measure of the sample’s resistivity; for metal samples of known resistivity, this permits an absolute measurement of sample thickness.
For semiconductor samples, mere microamperes of sample current i will give millivolts of Hall potential ΔV. For metal samples, with a carrier density n of order 10⁸ times larger, the Hall potentials are vastly smaller – so we build our copper samples thinner (t < 20 μm, instead of t ≈ 500 μm), and we use much larger sample currents (i ≈ 3 A, instead of i « 3 mA). This gives microvoltlevel Hall potentials, conveniently detected with a sensitive DMM.