Terahertz Frequency Materials Testing at Cryogenic Temperatures and in High Magnetic Fields

ABSTRACT: Temperature and magnetic field dependent terahertz spectroscopies have proven useful for characterizing novel electronic and magnetic materials. To this end, we are developing a turn-key, continuous-wave (CW) terahertz transmission platform operating from 5 K to 300 K with fields up to 9 T. Fiber-coupled photoconductive switches operate from 200 GHz to 1.2 THz in the cryogenic and high-field sample environment -- eliminating the need to align a THz beam through multiple cryostat windows. In Phase I, first generation prototype hardware demonstrated the promise of this approach especially for characterization of thin-film electronic materials. This proposal focuses on finalizing development, application, validation, and software integration of the experimental methods and physical models that ultimately form the heart of a commercial THz material characterization system. In this work, the accuracy of material parameter extraction algorithms will be improved with the development of a calibration procedure specific to this experimental platform. Upgrades to first generation hardware, including a more phase-stable CW-THz spectrometer, will improve the efficiency and reliability of signal acquisition. Finally, the hardware, calibration and material property extraction algorithms will be validated through a series of Hall and CW-THz characterization measurements on conductive ZnO thin films.; BENEFIT: This system will be an affordable, compact, convenient-to-use measurement platform focused on the characterization needs of researchers of novel electronic and magnetic materials. As a turnkey solution conditioned with the necessary cryogenic/ magnetic sample environment and application-specific software, scientist users who are not necessarily optics and THz experts can rapidly begin productive and illuminating material characterization work. THz characterization is expected to help reveal new properties of materials being studied for high speed semiconductor, THz sensors, photovoltaics, organic electronics, and spintronics applications, as well as chemical/biological threat detection.