34420 a nanovolt meter

Standard electrical characterization was performed in a liquid ⁴He gas flow cryostat, which allowed for temperatures down to 2 K and magnetic fields up to 14 T. All reported values of charge carrier mobility and charge carrier concentration were extracted from four-probe Hall and quantum Hall measurements. The standard measurement setup used current biased samples at maximum of 100 nA DC (Keithley 6221 DC and AC current source, Agilent 34420 A nanovolt meter), in this range samples showed linear IV characteristics down to cryogenic temperatures. The electrostatic top gate was DC biased with voltages ranging from −100 to +200 V, where leakage current was <0.05 nA.

Au microelectrodes for electrical
characterization were prepared by standard ultraviolet contact photolithography
and sputtering of an 8 nm Cr adhesion layer, followed by 250 nm Au
for general substrates and 75 nm Au for the microelectrodes on SiO₂ (300 nm)/p-Si substrates (CrysTec GmbH; Germany).
In
situ two-point electrical transport measurements were carried out
inside the SEM microscope after FEBID/FIBID.^{59 (link)} Standard measurements were performed using a Keithley 2400 source
meter and an Agilent 34420A nanovoltmeter.