Coherent Terahertz Spectroscopic Imaging with Scattering Near-Field Microscopy

Abstract

A THz scattering-type near-field microscope (THz-NFM) is implemented by combining a conventional THz time-domain spectroscopy system and an atomic force microscope. A float-zone silicon wafer partially coated with a gold layer is imaged with the THz-NFM system. The resolution of the system is estimated to be less than 100 nm. Measured approach curves on the gold surface and the float-zone silicon surface show a clear near-field interaction. Spectroscopic measurements are performed on each part of the sample. A theoretical model for the THz-NFM is developed. We demonstrated the quantitative analysis and measurements of near-fields interactions in the THz-NFM. We developed a self-consistent line dipole image method for the quantitative analysis of the near-field interaction in THz-NFM. The approach curves and relative contrasts on gold and silicon substrates were in excellent agreement with calculations by the line dipole image method. This thesis is the first demonstration of the nanoscale THz NFM which is capable of broadband spectroscopic measurements.