We present a new experimental method for determining the broadband dielectric permittivity of ferroelectric thin film samples over the broad frequency range 100 Hz - 40 GHz. Such characterization is extremely important for both a fundamental understanding of the dielectric response of ferroelectrics, as well as for a wide range of potential device applications of these technologically important materials. Ferroelectric materials in general display a wide range of behavior as a function of temperature, frequency, composition, and electric field bias, so comprehensive measurement techniques are required in order to adequately cover the broad parameter space relevant for understanding the electromagnetic response of these materials systems. Our experimental technique consists of applying accurate measurements to an ensemble of planar devices patterned onto a single thin-film samples using photolithographic techniques. This approach allows us to combine different types of devices, e.g. lumped-element and distributed structures, in order to determine the dielectric response over an extremely wide range of frequencies, as well as to use different device geometries in order to isolate device-dependent measurement errors such as surface or interface effects. The resulting frequency-dependent dielectric permittivity function can then be measured as a function of composition, temperature, or electric field bias to more fully understand the behavior of ferroelectric materials systems. We describe in detail the different device structures and measurement techniques that are employed to cover this broad frequency range, and demonstrate the usefulness of the approach by presenting broadband permittivity results for a strontium titanate (SrTiO3) thin film at room temperature.
Citation: Ferroelectric Thin Films at Microwave Frequencies
Publisher Info: Research Signposts, Kerala, IN
Pub Type: Books
broadband characterization, ferroelectric thin films, microwave dielectric response