Student: Thomas Theiner

Project: Electronic Band Structure of ALD MoTe2/TiO2 Heterostructures

Poster: Horizontal (PDF) | Vertical (PDF)

Institution: Lehigh University

Major: Material Science & Engineering

Advisor: Nicholas Strandwitz


Molybdenum Telluride, MoTe2, is a promising photovoltaic material which strongly absorbs light across the visible spectrum.  Atomic Layer Deposition (ALD) was applied to synthesize ultra-thin films of MoTe2 and deposit four nanometers of amorphous TiO2 on top of these as a charge-separating layer.  ALD is a process in which a substrate is alternately exposed to low-vacuum concentrations of two precursors which react at the surface in a self-limiting manner to enable extremely uniform and thin films, often as thin as a single layer of atoms. Such films of MoTe2 have unique electronic properties, namely an indirect-to-direct bandgap transition as the thickness of the film is reduced to the monolayer case.  The goal of this project was to characterize the electronic properties of these thin-film heterostructures of MoTe2 and TiO2 and analyze the chemistry observed at the interface.  The behavior of excitons at the MoTe2/TiO2 interface is of primary interest.  In this work, the band alignments of the Valence and Conduction bands have been identified for MoTe2/TiO2 heterostructures with five thicknesses of MoTe2, ranging from approximately one to eight atomic monolayers, as part of a larger study applying Transient Absorption Spectroscopy to assess the behavior of excitons in MoTe2.  X-ray photoelectron spectroscopy was also applied to analyze the chemical species present at the MoTe2/TiO2 interface.

Thomas Theiner

About Thomas Theiner

Thomas Theiner is a sophomore in the Lehigh University Materials Science and Engineering Department.  His main areas of interest are nanotechnology and technologies promoting sustainability.  His current research area is ultra-thin films, particularly their applications to solar energy technologies.  He has been working with Strandwitz research group during his first two years in college and over the intervening summer studying thin films deposited by Atomic Layer Deposition.