Variable-temperature Microwave Impedance Microscope with Light Stimulation for Research on Photo-induced Phase Transitions
Abstract
The Defense University Research Instrumentation Program (DURIP) is designed to improve the capabilities of U.S. Universities to conduct research and to educate scientists and engineers in selected technical areas of importance to national defense. DURIP funding provides for the acquisition of research equipment and instrumentation for this purpose. This proposal is for the purchase of components for a Variable-temperature Microwave Impedance Microscope with Light Stimulation. The P.I., Professor Keji Lai, of the University of Texas will use the equipment to augment and enhance research capabilities in the area of Photo-induced Phase Transitions (PIPTs). The proposed system consists of a cryogenic chamber and the enclosed low-temperature positioning and scanning stages, a scan controller, a set of microwave electronics for impedance detection, and a set of laser optics for light stimulation. The new equipment will allow us to perform nanoscale electrical imaging for the study of PIPTs in novel materials. Different from the conventional temperature-, pressure-, or electric/magnetic field-driven phase transitions, the PIPT is initiated by photo-generated carriers that modify the potential energy landscape and redirect the system into a competing state. To date, PIPTs have been probed by macroscopic diffraction, transport, and optical measurements to study the drastic change of electrical and optical properties during the process. On the other hand, due to the intricate interplay between disorders and electron correlations, most advanced materials showing PIPTs also exhibit prominent nanoscale electronic inhomogeneity. It is therefore imperative to investigate their local photo-response for the fundamental understanding of PIPTs. Microwave Impedance Microscope (MIM) is a powerful technique to spatially resolve the mesoscopic electrical properties without the need of contact electrodes. Combined with laser stimulation, the setup will enable the following innovative scientific work (1) Mapping out the coexistence of multiple photo-induced phases in chalcogenide glasses; (2) Understanding the physical mechanism of light-driven versus temperature or field-driven metal-insulator transitions in complex transition metal oxides; (3) Probing the spatial propagation of hidden phases in charge-density wave materials. The proposed program is significant as it introduces a new tool for probing light-driven phenomena in novel quantum materials at the nanoscale. The spatial, temporal, and thermal evolutions of the emergent phases to be studied here carry important information of the underlying physics, which is not captured by earlier bulk measurements. The work will establish a new research direction and augment existing DoD programs at UT-Austin. The research is of fundamental importance for Army applications of photo-sensitive materials in future sensing and data storage devices.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 12, 2017
- Source ID
- W911NF1610276
Entities
People
- Keji Lai
Organizations
- Army Contracting Command
- United States Army
- University of Texas at Austin