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 noncond ucting materials of interest such as glass formers, liquid crystals, p olymers, or ferroelectrics. Dielectric polarization noise was measured via voltage fluctuations in a capacitance cell filled with sample mat erial. Measurements were carried out in the temperature range 80-400 K on glycerol and poly-vinyl-chloride near their respective glass trans itions. To maximize the dynamic range and sensitivity and limit effect s of stray capacitance an ultralow-noise junction field-effect transis tor based preamplifier was operated adjacent to the sample in vacuum w ithin the low-temperature cryostat. The technique offers potentially g reater accuracy than susceptibility measurements in low-loss regimes, and may be useful in single-electron-transistor applications. (C) 1997 American Institute of Physics.