Electronic properties and device applications of rotationally controlled van der Waals heterostructures
type: CreativeWork
description: Van der Waals heterostructure is a highly versatile platform to unveil two-dimensional (2D) electron physics and to explore new device functionalities. In this dissertation, we present comprehensive experimental studies of van der Waals heterostructures considering the rotational control between different 2D layers. A hemispherical handle polymer stamp is introduced to improve 2D layer transfer, which allows rotational control when stacking 2D layers. To verify the accuracy of rotational control, we demonstrate a rotationally aligned double monolayer graphene using a sequential pick-up of two graphene layers, which originate from a single crystal domain, and compare it with Bernal stacked bilayer graphene using Raman spectroscopy, scanning probe microscopy (SPM), and electrical transport measurements under an applied transverse electric-field. We also demonstrate resonant tunneling in double bilayer graphene heterostructures using hexagonal boron nitride (hBN) as an interlayer dielectric, in which rotational alignment between the two bilayer graphene is the key ingredient for the device functionality. To further highlight the significance of highly accurate rotational alignment between different layers, we demonstrate tunable moiré crystals in small-twist-angle bilayer graphene. A comprehensive electron transport study is conducted, and the data are compared with SPM results. We observe transport gaps at ±8 electrons per moiré unit cell, along with a conductivity minimum at charge neutrality with twist angle less than 1°. In magnetic fields, we also observe the emergence of a Hofstadter butterfly in the energy spectrum, with four-fold degenerate Landau levels (LLs), and broken symmetry quantum Hall states at filling factors, ν = ±1, ±2, ±3. We demonstrate dual-gated tungsten diselenide (WSe₂) interlayer tunneling devices, consisting of two WSe₂ monolayers with controlled rotational alignment, and separated by a thin hBN tunnel barrier. In samples where the two WSe…
abstract: Van der Waals heterostructure is a highly versatile platform to unveil two-dimensional (2D) electron physics and to explore new device functionalities. In this dissertation, we present comprehensive experimental studies of van der Waals heterostructures considering the rotational control between different 2D layers. A hemispherical handle polymer stamp is introduced to improve 2D layer transfer, which allows rotational control when stacking 2D layers. To verify the accuracy of rotational control, we demonstrate a rotationally aligned double monolayer graphene using a sequential pick-up of two graphene layers, which originate from a single crystal domain, and compare it with Bernal stacked bilayer graphene using Raman spectroscopy, scanning probe microscopy (SPM), and electrical transport measurements under an applied transverse electric-field. We also demonstrate resonant tunneling in double bilayer graphene heterostructures using hexagonal boron nitride (hBN) as an interlayer dielectric, in which rotational alignment between the two bilayer graphene is the key ingredient for the device functionality. To further highlight the significance of highly accurate rotational alignment between different layers, we demonstrate tunable moiré crystals in small-twist-angle bilayer graphene. A comprehensive electron transport study is conducted, and the data are compared with SPM results. We observe transport gaps at ±8 electrons per moiré unit cell, along with a conductivity minimum at charge neutrality with twist angle less than 1°. In magnetic fields, we also observe the emergence of a Hofstadter butterfly in the energy spectrum, with four-fold degenerate Landau levels (LLs), and broken symmetry quantum Hall states at filling factors, ν = ±1, ±2, ±3. We demonstrate dual-gated tungsten diselenide (WSe₂) interlayer tunneling devices, consisting of two WSe₂ monolayers with controlled rotational alignment, and separated by a thin hBN tunnel barrier. In samples where the two WSe…
author: Kim, Kyounghwan
language: en
keywords: Van der Waals heterostructures, Moire pattern, Resonant tunneling
date published: 2018-10-12
date modified: 2026-07-24T05:01:18Z
provider: University of Texas
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: The University of Texas at Austin

PropertyValue
property ID: Handle
value: https://hdl.handle.net/2152/74214

PropertyValue
property ID: DOI
value: 10.26153/tsw/1345