ABSTRACT
We measure photon-assisted tunneling in 4- and 6-junction electron pumps at photon frequencies up to 60 GHz. We determine the microwave voltage at the pumps using noise thermometry. The standard theory of leakage in the electron pump, modified to include photon-assisted tunneling, describes our experiments well. From this test of theory we argue that, in the absence of external microwaves, photon-assisted tunneling driven by 1/f noise is an important error mechanism in electron pumps.
ABSTRACT
We describe the current performance of the prototype microcalorimeter energy-dispersive spectrometer (&mgr;cal EDS) developed at NIST for X-ray microanalysis. We show that the low-energy &mgr;cal EDS, designed for operation in the energy range 0.2-2 keV, offers significant advantages for low-beam-energy microanalysis. We present several examples in which the prototype &mgr;cal EDS has been used to solve problems in low-voltage microanalysis, including the analysis of tungsten silicide (WSi2), titanium nitride (TiN) and barium titanate (BaTiO3) and the measurement of chemical shifts in Fe and C compounds.
ABSTRACT
A capacitance standard based directly on the definition of capacitance was built. Single-electron tunneling devices were used to place N electrons of charge e onto a cryogenic capacitor C, and the resulting voltage change DeltaV was measured. Repeated measurements of C = Ne/DeltaV with this method have a relative standard deviation of 0.3 x 10(-6). This standard offers a natural basis for capacitance analogous to the Josephson effect for voltage and the quantum Hall effect for resistance.
