Post by Lake Shore Jeff L on Jun 4, 2019 15:02:46 GMT -5
Geometry C and D refer to two different way to connect the current source and voltmeter to your sample. For a hall measurement the current source is connect on one diagonal of the sample and the voltmeter is connect to the other diagonal. However, if you interchange the current source and voltmeter this is also a valid measurement. These two measurements a called Geometry C and Geometry D. If the sample is idea, these two measurements are equal.
One reason why you could be getting different carrier type in the two geometries is that the mobility of your sample is too low for a DC field measurement. When the mobility of your samples is below about 10 cm2/(V s), the DC measurement becomes very difficult. Here is a link to our white paper on AC field Hall measurements. The AC field option is not available on the superconducting magnet 8425 system, but the white paper describes the problems of measuring low mobility samples with DC field Hall.