The Ohio State University
McCormick, Elizabeth Joan, McCormick.
Optical Properties of Two Dimensional Semiconductors.
Degree: PhD, Physics, 2018, The Ohio State University
Two dimensional materials (2D) have become a huge
research focus in recent history due to the interesting properties
and phenomena that occur with reduced dimensionality. Additionally,
the reduced size of these materials, the plethora of different
properties available in the 2D arsenal, and the ability to
relatively easily combine different 2D materials makes them
extremely promising for nanodevices and future computing
architectures. Here, we investigate the optical properties of two
different 2D semiconductors, germanane and transition metal
dichalcogenides (TMDs). We focus on the band gap and band edge
physics in thin film germanane, a topic that is largely unexplored.
We are able to grow thin films of germanane and transfer them onto
insulating substrates, a critical step for opto-electronic
applications and investigations. Using a combination of optical and
opto-electronic techniques including photoconductivity, absorption
spectroscopy, and photoluminescence, we are able to investigate the
band gap, as well as determine the existence of band tail and
defect states in the gap. Having an understanding of the band gap
is necessary for future electronic and opto-electronic
applications, as many of the interesting properties of a
semiconductor are highly dependent on the band gap. Transition
metal dichalcogenides have very interesting spin/valley properties
due to the large spin-orbit coupling and existence of
non-equivalent valleys in their band structure. We investigate the
long spin and valley lifetimes in tungsten disulphide, a member of
the TMD family, using time resolved Kerr rotation (TRKR) microscopy
and photoluminescence microscopy. Our unique approach provides
insight into the role of dark trions in the long spin and valley
lifetimes, in addition to the transfer of angular momentum to
resident carriers in the material. We also find that the strong
spin-orbit coupling leads to spins robust against in-plane external
magnetic fields. In order to study the unique spin and valley
transport in TMDs, including the valley Hall effect, we developed a
spatially offset time resolved Kerr rotation microscopy system,
which allows spins and valleys to be excited in one location and
probed in another. Preliminary data on spin/valley diffusion in
tungsten diselenide, another member of the TMD family, is
presented, with a discussion of the substrate effect on diffusion
in WSe2. These studies enable an unprecedented microscopic
understanding of spin and valley dynamics in TMDs, a crucial
component in developing future nanoscale spintronic and
Advisors/Committee Members: Kawakami, Roland (Advisor).
Subjects/Keywords: Condensed Matter Physics; Optics; Physics; Transition Metal Dichalcogenides; TMD; ultra-fast optics; TRKR; time resolved Kerr rotation; imaging; germanane; 2D; spin dynamics; valley dynamics; photoluminescence, spin lifetime
to Zotero / EndNote / Reference
APA (6th Edition):
McCormick, Elizabeth Joan, M. (2018). Optical Properties of Two Dimensional Semiconductors. (Doctoral Dissertation). The Ohio State University. Retrieved from http://rave.ohiolink.edu/etdc/view?acc_num=osu1531907387651019
Chicago Manual of Style (16th Edition):
McCormick, Elizabeth Joan, McCormick. “Optical Properties of Two Dimensional Semiconductors.” 2018. Doctoral Dissertation, The Ohio State University. Accessed December 16, 2018.
MLA Handbook (7th Edition):
McCormick, Elizabeth Joan, McCormick. “Optical Properties of Two Dimensional Semiconductors.” 2018. Web. 16 Dec 2018.
McCormick, Elizabeth Joan M. Optical Properties of Two Dimensional Semiconductors. [Internet] [Doctoral dissertation]. The Ohio State University; 2018. [cited 2018 Dec 16].
Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1531907387651019.
Council of Science Editors:
McCormick, Elizabeth Joan M. Optical Properties of Two Dimensional Semiconductors. [Doctoral Dissertation]. The Ohio State University; 2018. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1531907387651019