The Design of a Scanning Tunneling Microscope for Electroluminescence Studies
Hairsine, Kristopher Ryan
STM , Piezoelectric
A conventional scanning tunneling microscope (STM) provides topographical and tunneling spectra information of atomic structures. However, the extremely small lateral dimension of the tunneling filament is also responsible for locally exciting photon emission with low-energy electrons. By combining an optical system to capture emitted photons with a conventional STM a powerful tool is realized. Optical, in addition to the geometrical and electrical, properties of atomic structures may be studied simultaneously at sub-Angstrom spatial resolution. This information could potentially be used as a means for chemically identifying individual molecules on surfaces. Furthermore, a complete understanding of luminescent molecules at the nanometer length scale could have implications with regard to nanoscale electronic devices. This thesis presents an innovative design of a novel STM in conjunction with an optical system to study the electroluminescence of nanoscale objects. The STM features (1) a parabolic mirror as the primary optical component for photon capture, (2) simplified miniature piezoelectric actuated inertial z-motors and xy-positioning stage used to position the tunnel junction at the focal point of the parabolic mirror, (3) high photon collection efficiency equal to 0.90pi steradians and (4) capacitive displacement sensors monitoring the position of the tunnel junction in three-dimensions. This document reveals how the combination of these features makes this STM design superior to existing designs. The design of the STM, the importance of its features and the characterization of its performance are discussed in detail.