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Controlling the Charge Density Wave in VSE2 Containing Heterostructures

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.

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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.

Identiferoai:union.ndltd.org:uoregon.edu/oai:scholarsbank.uoregon.edu:1794/23179
Date10 April 2018
CreatorsHite, Omar
ContributorsJohnson, David
PublisherUniversity of Oregon
Source SetsUniversity of Oregon
Languageen_US
Detected LanguageEnglish
TypeElectronic Thesis or Dissertation
RightsAll Rights Reserved.

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