Exploring the properties of layered materials as a function of thickness has largely
been limited to semiconducting materials as thin layers of metallic materials tend to
oxidize readily in atmosphere. This makes it challenging to further understand properties
such as superconductivity and charge density waves as a function of layer thickness that
are unique to metallic compounds. This dissertation discusses a set of materials that use
the modulated elemental reactants technique to isolate 1 to 3 layers of VSe2 in a
superlattice in order to understand the role of adjacent layers and VSe2 thickness on the
charge density wave in VSe2.
The modulated elemental reactants technique was performed on a custom built
physical vapor deposition to prepare designed precursors that upon annealing will self
assemble into the desired heterostructure. First, a series of (PbSe)1+δ(VSe2)n for n = 1 – 3
were synthesized to explore if the charge density wave enhancement in the isovalent
(SnSe)1.15VSe2 was unique to this particular heterostructure. Electrical resistivity
measurements show a large change in resistivity compared to room temperature
resistivity for the n = 1 heterostructure. The overall change in resistivity was larger than
what was observed in the analogous SnSe heterostructure.
v
A second study was conducted on (BiSe)1+δVSe2 to further understand the effect
of charge transfer on the charge density wave of VSe2. It was reported that BiSe forms a
distorted rocksalt layer with antiphase boundaries. The resulting electrical resistivity
showed a severely dampened charge density wave when compared to both analogous
SnSe and PbSe containing heterostructures but was similar to bulk.
Finally, (SnSe2)1+δVSe2 was prepared to further isolate the VSe2 layers and
explore interfacial effects on the charge density wave by switching from a distorted
rocksalt structure to 1T-SnSe2. SnSe2 is semiconductor that is used to prevent adjacent
VSe2 layers from coupling and thereby enhancing the quasi two-dimensionality of the
VSe2 layer. Electrical characterization shows behavior similar to that of SnSe and PbSe
containing heterostructures. However, structural characterization shows the presence of a
SnSe impurity that is likely influencing the overall temperature dependent resistivity.
This dissertation includes previously published and unpublished co-authored
materials.
| Identifer | oai:union.ndltd.org:uoregon.edu/oai:scholarsbank.uoregon.edu:1794/23179 |
| Date | 10 April 2018 |
| Creators | Hite, Omar |
| Contributors | Johnson, David |
| Publisher | University of Oregon |
| Source Sets | University of Oregon |
| Language | en_US |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Rights | All Rights Reserved. |
Page generated in 0.0016 seconds