High-sensitivity dielectric polarization noise measurements

Techniques for measurement of low-level dielectric polarization noise spectra over a broad dynamic range are described. The method provides a powerful probe of 1/f noise and near-equilibrium dynamics in nonconducting materials of interest such as glass formers, liquid crystals, polymers, or ferroelectrics. Dielectric polarization noise was measured via voltage fluctuations in a capacitance cell filled with sample material. Measurements were carried out in the temperature range 80-400 K on glycerol and poly-vinyl-chloride near their respective glass transitions. To maximize the dynamic range and sensitivity and limit effects of stray capacitance an ultralow-noise junction field-effect transistor based preamplifier was operated adjacent to the sample in vacuum within the low-temperature cryostat. The technique offers potentially greater accuracy than susceptibility measurements in low-loss regimes, and may be useful in single-electron-transistor applications. (C) 1997 American Institute of Physics.