Schematic display of two- and four-probe techniques for measuring resistance. In the four-probe technique the bias current is injected through the two outer contacts, and the voltage is measured across the two inner contacts. In the two-probe technique the same contacts are used for current biasing and voltage measurement.
Sketch of noise measurement setup. The sample equivalent circuit is shown inside the dashed box and is represented by the resistances , , and , each with an associated noise source . The noise measurements are performed with both two- and four-probe configurations.
(Color online) Microphotograph of a planar structure patterned in the investigated LSMO thin film consisting in a wide horizontal line and several tracks to perform electrical transport and noise measurements. Voltage probes are placed on each side of the line.
Noise voltage spectral densities, and , generated by the bias resistor and the preamplifier, respectively. The experimental spectral density, measured with no current flowing in the bias circuit , is also reported.
Frequency dependence, at a constant current and at temperature , of noise voltage spectral densities measured across the current contacts (: gray curve) and across the voltage contacts (: black curve), using a two-probe and a four-probe technique respectively. The spectral trace, obtained by applying the proposed experimental procedure (: curve), is also shown.
Bias current dependencies, at temperature and at a frequency , of the measured (open circles) and of the corrected (full circles) voltage spectral density components. The curves are fittings of the data using a second order polynomial. The values of the fitting parameters are reported in Table II.
Measured values of the resistances and the capacitance used. The reported quantities are referred to the case study of the sample: LSMO/STO(100)-G237 (; ; ).
Fitting coefficients of Eq. (11) for the spectral density component of the experimentally measured trace and of the corrected trace .
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