We report on dielectrophoretic alignment of carbon black particles into radially arranged string-like assemblies in oligourethane mixtures followed by photopolymerization. Using finite element modelling and optical microscopy we find significant difference in field distributions depending on the substrate beneath aligned films. On glass, the field is concentrated between the electrode tips leading to string-like assemblies between the tips. On oxide covered silicon, the field is distributed along the electrode circumference leading to more distributed fractal assemblies. Using comprehensive dc resistance measurements and ac-impedance spectroscopy we show that the resistance of the strings varies from 120 kΩ to 5 MΩ with a mean of 1.03 MΩ.Strings on oxide covered silicon show significantly higher resistances than the strings on glass. We also demonstrate the effect of aging and an increase in resistance through elongating aligned strings.

This paper presents characterization of the first prototype of a predictable photodiode cryogenic radiometer (PPCR) at 77 K. The PPCR combines a predictable quantum efficiency detector (PQED) with a cryogenic radiometer (CR). When combining these two inherently different primary standards for measuring optical power on the same device, systematic error sources are eliminated, and the relationship between the elementary charge e and Planck's constant h can be found from the modelled responsivity of the PQED. Our initial value deviates from the tabulated value of CODATA by 0.004 %.