Dynamic environmental transmission electron microscopy of spin crossover materials

Cornelius, Ryan Dean

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https://hdl.handle.net/2142/107966 Copy

Description

Title

Dynamic environmental transmission electron microscopy of spin crossover materials

Author(s)

Cornelius, Ryan Dean

Issue Date

2020-05-05

Director of Research (if dissertation) or Advisor (if thesis)

van der Veen, Renske M

Department of Study

Chemistry

Discipline

Chemistry

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Dynamic Transmission Electron Microscopy
• time-resolved microscopy, DTEM, spin-crossover, nanomaterials

Abstract

The work reported here focuses on the study of spin crossover (SCO) materials via dynamic transmission electron microscopy (DTEM). SCO metal complexes commonly contain first-row d4-d7 transition metals in an octahedral ligand field, which splits the d-orbitals into tripledegenerate t2g and anti-bonding, double-degenerate eg* levels. The electrons can rearrange across these levels such that a low-spin (LS) and a high-spin (HS) configuration is obtained. This LS-HS bistability makes SCO materials promising candidates for nanodevices which take advantage of the different physical and electronic properties of the LS and HS phases. In this work, thin films of two SCO materials are examined: FeII(bapbpy)(NCS)2 and FeII(HB(tz)3)2. These materials have been proven to be vacuum sublimable, as well as to possess cooperative spin crossover transitions within accessible temperatures. Dynamic transmission electron icroscopy (DTEM) is the technique of choice for these studies due to its unique capabilities to analyze the physical structure and electronic properties with time resolutions ranging from femtoseconds, nanoseconds, to milliseconds. This is accomplished by a variety of stroboscopic and fast camera methods. The work detailed here includes the integration of UV photoexcitation, development of low-dose methodologies, and details regarding the pump delivery system of the DTEM setup.

Graduation Semester

2020-05

Type of Resource

Thesis

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http://hdl.handle.net/2142/107966

Copyright and License Information

Copyright 2020 Ryan Cornelius

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