Moire Modification Due to Sample Imperfections on Aligned Graphene/Hexagonal Boron Nitride Heterostructures for New Quantum Dot Devices

Quantum dots (QD) are a perennial device testbed for the development of novel quantum sensors, information processing units , and simulators. Two-dimensional materials are atomically-thin and exhibit versatile properties when stacked onto one another. Their small lateral dimensions facilitate compacting many components into one device, enabling ultra high density quantum dot devices. There are a wide variety of heterostructure configurations that provide the necessary high tunability for QD devices. One such configuration consists of graphene (G) mated to hexagonal boron nitride (hBN) with aligned lattices. This configuration results in graphene with a band gap, a critical component for a QD device. Notably, alignment of these materials result in moire patterns, which can provide a direct indication of their lattice alignment. These periodic geometric patterns form when two similar lattices are overlaid on top of each other. Features on the sample surface, such as bubbles or folds, can significantly alter the resulting moire pattern. The periodicity can be characterized by scanning probe microscopy techniques to reveal the twist angle between the materials, as well as observe the abnormalities in the periodicity that can occur due to sample imperfections. In this presentation I will discuss the fabrication and characterization of aligned G/hBN heterostructures. Sample fabrication was done via polymer transfer method while sample characterization was done by Atomic Force Microscopy (AFM) and Lateral Force Microscopy (LFM). Such characterization yields critical topographical information and moire characteristics that will be utilized to determine sample viability for new QD devices.