All ETDs from UAB

Advisory Committee Chair

Renato Camata

Advisory Committee Members

David Hilton

Mary Ellen Zvanut

Document Type

Thesis

Date of Award

2022

Degree Name by School

Master of Science (MS) College of Arts and Sciences

Abstract

Iron-based superconductors have been of interest in recent decades due to their unconventional nature which is coupled with the inclusion of high temperature superconductors. Iron selenide is a particular contender due to its versatility and high critical temperature in the monolayer form. Pulsed Laser Deposition has been demonstrated as a prime method for the growth of iron selenide films due to its control of the film stoichiometry, thickness, and crystallinity. In this thesis, Pulsed Laser Deposition was used to image the β-FeSe plasma plume under varied spot sizes and background pressures and determine whether β-FeSe epitaxy is possible with the introduction of background gas. It was further used to develop iron selenide films under these conditions to study their effect on film composition, orientation, and continuity. Langmuir probe data and gated ICCD camera imaging indicate the increase of background pressure or the decrease of spot area decreases the density and slows the species in the plume. Imaging further reveals a shift in the laser energy apportionment from thermal heating to directed energy as a function of the spot size. Furthermore, increased background pressure separates the plume into three distinct components. The slowing of the atomic species in the plasma allows for their recombination into molecular clusters to drive the FeSe deposition. FeSe films grown under the varied conditions, using a 248 nm KrF excimer laser and a substrate temperature of 350◦ C, all present the β phase and c-axis orientation after being characterized via X-Ray Diffraction and Atomic Force Microscopy. Films deposited under background pressure demonstrate a distinctly different microstructure from the continuous layers under vacuum conditions which is formed through the deposition of molecular clusters. The clusters re-orient during deposition to maintain both in-plane and out of plane epitaxy, so the FeSe thin film growth is determined by the epitaxy regardless of introduction of background gas.

Share

COinS