SBIR-STTR Award

Terahertz (THz) spectroscopies offer unmatched non-contact probing of low-energy excitations underlying electronic transport and magnetism in a wide range of novel materials. To-date, expensive and complex THz Time Domain Spectroscopy (THz-TDS) systems are the most common THz source used in these studies. Lower cost, continuous wave (CW-THz) spectroscopy systems can offer comparable performance as THz-TDS but with superior spectral resolution. Lake Shore will leverage its existing efforts in coherent CW terahertz emission and detection at cryogenic temperatures to deliver a prototype CW-THz materials characterization platform tailored to the research needs of the AFRL materials community. In Phase I, Lake Shore will collaborate with Wright State University and the University of Arizona to develop and validate material parameter extraction methodologies with CW-THz spectroscopy in cryogenic and high magnetic field environments. Comparisons between Hall, THz-TDS, and CW-THz measurements on known semiconductor and novel materials of interest to AFRL researchers will provide a benchmark and methodology for CW-THz materials characterization. A final report at the end of Phase I will discuss these efforts and outline necessary alterations to the hardware platform and measurement methodologies required for materials of interest as well as additions to CW-THz material parameter extraction algorithms.

Benefit:
Lake Shore?s vision is to provide researchers of novel semiconductor and magnetic materials with a turnkey characterization solution that is affordable, highly capable and readily usable. Affordability is achieved in part over previously complex and costly time-domain systems (THz-TDS) by utilizing emerging, lower cost CW-THz generation and detection. Other benefits include faster examination of novel materials due to non-destructive, non-contact THz characterization; more convenient, higher resolution measurements due to CW-THz over THz-TDS; and new research insights into material properties that will help accelerate the development of the next generation of electronic devices. The viability of using CW-THz for these types of characterizations will be demonstrated in this Phase I project.

Keywords:
Cw Terahertz, Semiconductor Material Characterization, Non-Contact, Integrated System, Cryogenics, Magnetics, Measurement Protocols, Thz Electronics

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.

Benefits:
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.

Keywords:
materials characterization, terahertz, chemical biological threat detection, plasmonics