UC Berkeley

Without changing a material’s chemical composition, lattice geometry, or orbital structure, the physical properties of a material can be drastically modified by changes to its dimensionality. Two-dimensional materials are therefore an ideal platform for exploring the role of reduction in material geometry because they can be stacked to form three-dimensional structures or etched to form one- and zero-dimensional features.

In this dissertation, I explore the methods for isolating two-dimensional hexagonal boron nitride (h-BN) and related materials, for controlling their three-dimensional structural properties synthetically, and for using irradiation to locally reduce their dimensionalities through vacancy formation. After discussing these techniques and their underlying physics, I investigate the applications of etched two-dimensional materials for nanopore sequencing and nanomachines.

In Chapter 2, I outline the techniques for isolation of two-dimensional materials by both exfoliation from bulk crystals and by synthetic deposition. I delve into the mechanics of chemical vapor deposition synthesis of h-BN graphene and establish methods for controlling their three-dimensional stacking.

In Chapter 3, I investigate the effects of electron irradiation on h-BN. I show that accelerated electrons induce specific vacancy geometries in h-BN depending on its stacking sequence and develop a method for creating atomically precise nanopores. I explore the application of these nanopores for DNA sequencing.

In Chapter 4, I similarly characterize the effects helium ion irradiation on two-dimensional materials. I explore the damaging effects on the lattice of h-BN and MoS2 while assessing the controlled use of these helium ions to etch one- and zero-dimensional nanostructures.

In Chapter 5, I study the use of patterned graphene for softened mechanical actuators. I show that micron scale graphene can be used as an acoustic transducer and demonstrate a novel electron beam driven rotational actuator.