Electronic, Structural, and Chemical Response of Strain and Heteroatom Doping on Graphene
Open Access
- Author:
- Granzier-Nakajima, Tomotaroh
- Graduate Program:
- Physics (PHD)
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- August 30, 2021
- Committee Members:
- Chaoxing Liu, Major Field Member
Mauricio Terrones, Chair & Dissertation Advisor
Eric Hudson, Major Field Member
Joshua Robinson, Outside Unit & Field Member
Nitin Samarth, Program Head/Chair - Keywords:
- Graphene
strain
pseudo electromagnetic field
oxygen reduction reaction
graphene oxide
graphene ripple
doped graphene
boron and nitrogen co-doped graphene
nitrogen doped graphene
boron doped graphene
XPS
in-situ Raman - Abstract:
- Since their discovery, two-dimensional materials have exhibited a wide range of interesting and unique properties. Graphene’s low energy electrons are described by massless Dirac fermions and have served as a platform to observe many unique phenomena. The atomically flat nature of graphene also makes it ideal to study dopant properties and interactions. Methods for the manipulation of graphene present many unique possibilities that have been realized. Here I present three projects which explore the properties and applications of different methods for the manipulation of graphene’s properties. In the first project, non-uniform, periodic strain in suspended graphene is studied. To synthesize this system, I grew graphene under low pressure on a Cu substrate to encourage step bunching. Graphene which grew over these large Cu steps was suspended and found to ripple. In these regions, periodically varying pseudo electromagnetic fields are found to generate well-defined equally spaced electronic states. The mechanical properties of these nanoscale ripples were also studied and a coupling between bonding and stretching modes is identified. This coupling is unique to this length scale and not found in the rippling of classical elastic sheets. In the second project, the properties of graphene oxide (GO) films are explored. It is found that the mechanical properties of GO films can be altered by applying a mechanical shear strain. This strain is found to align the GO sheets and change its mechanical properties. Kirigami is additionally employed to expand the use of GO films as an actuator. The addition of kirigami cuts and control over GO film thickness enables electrostatic actuation of the films. In the third and final project, a general understanding of the mechanism by which dopants in graphene enhance its electrocatalytic properties for the oxygen reduction reaction (ORR) is investigated. Boron doped graphene and boron and nitrogen co-doped graphene are synthesized along with pristine graphene and hBN. Cyclic voltammetry and linear sweep voltammetry are used to characterize their electrochemical behaviors. X-ray photoelectron spectroscopy and in-situ Raman spectroscopy are used to explore the intermediate products during ORR. It is found that carbon atoms adjacent to dopant atoms play an important role in doped graphene for ORR and that epoxide groups may play a role in the ‘synergistic effect’ that has previously been observed to explain why graphene doped with multiple dopants has enhanced electrocatalytic properties. In-situ Raman is also identified as a potentially new technique for the detection of ORR intermediates.