Probing Nanoscale Fundamental Interactions of Electrons and Quasiparticles from Optical to Terahertz Frequencies
Abstract
The goal of the work was to probe fundamental nanoscale properties of electrons and quasiparticles in layered materials,correlated oxides and nitrides as well as nanoscale interactions with phase change materials by performingnanospectroscopicimaging from optical to terahertz frequencies. We have demonstrated a reconfigurable hyperbolic metasurfacecomprising of a heterostructure of isotopically enriched hexagonal boron nitride (hBN) in direct contact with the phase-changematerial vanadium dioxide (VO2). We implement a novel nanoscopy tools integrated with state-of-the-art infrared lasers and Vis/IRlight sources. We have introduced hyperspectral terahertz (THz) nano-imaging by combining scattering-type scanning near-field optical microscope (s-SNOM) with THz time-domain spectroscopy (TDS). We describe the technical implementations that enabled this achievement and demonstrate its performance with a heterogeneously doped semiconductor samples. We recorded for the first time THz hyperspectral image and with a spatial nanoscale spatial resolution by measuring at each pixel with a time domain spectrum covering the range from 0.4 to 1.8 THz. Fitting the spectra with a Drude model allows for measuring noninvasively and without the need for Ohmic contacts the local mobile carrier concentration of the differently doped semiconductor areas. Phase separations in ternary group III-Nitride semiconductor alloys area significant challenge that limits the efficiency and performance of optoelectronic devices. We have shown that the growth of indium-rich ternary In1xGaxN (InGaN) alloys by MOCVD exhibits strong nanoscale phase separations, reflected in compositional and gap energy fluctuations. Instability of black phosphorus (BP) surface due to chemical degradation in ambient conditions remains a major impediment to its prospective applications.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 06, 2019
- Accession Number
- AD1097071
Entities
People
- Mukesh Dhamala
Organizations
- Georgia State University