2DCC In-House Research Highlight

Project Summary: Transition metal dichalcogenides (TMDs) samples are often characterized using atomic force microscopy (AFM), which generates large amounts of historical data. To effectively use this data, models for automated detection and classification of TMD samples are needed. These trained models can then help create simplified, low-dimensional representations of the data that are more accessible. In this work, transfer learning with convolutional neural networks (CNNs) is used to classify five TMDs: MoS2, WS2, WSe2, MoSe2, and Mo-WSe2.

Project Summary: Transition metal dichalcogenide monolayers such as WS2 provide a platform for the production of diverse
device functionalities through doping. For example, the transition metal vanadium, when substituted on the WS2 lattice, produces a
dilute 2D magnetic semiconductor with room-temperature ferromagnetic ordering. This study performs the first broadband
optical characterization of its electronic band structure and dependence on vanadium concentration. Power-dependent

Project Summary: Invited book chapter in “Comprehensive Semiconductor Science and Technology”, ScienceDirect/Elsevier

Project Summary: Controlled thin film growth via molecular beam epitaxy
(MBE) is pivotal in tuning material properties for various applications. Addressing
challenges in thin film fabrication, such as island growth modes and
morphological irregularities is essential for enhancing material and device
performance. This study reports an atomic-level investigation of the selective
area nucleation of SnSe on a MgO(001) substrate via MBE, using ReaxFF
reactive molecular dynamics (MD) simulations. By employing graphene masks

Project Summary: Computer vision models have become a mainstay in analysis of microscopy characterization data and hence the need to address the implication of using different models (for example regression or segmentation), data augmentations, and pretrain domains on the deployment of the models for practical applications. In this study, we perform an in-depth analysis of the prediction of crystal coverage (the proportion of the substrate covered with grown crystal) in WSe2 thin film atomic force microscopy (AFM) micrographs using regression and segmentation models.

Heterogeneous interfaces that juxtapose different materials have been known to create emergent quantum phenomena. We used molecular beam epitaxy to synthesize heterostructures formed by stacking together two magnetic materials, a ferromagnetic topological insulator (Cr,Bi,Sb)₂Te₃ and an antiferromagnetic metal, iron chalcogenide (FeTe). High-resolution transmission electron microscopy (HRTEM) and x-ray diffraction show the formation of heterostructures with sharp interfaces and good crystallinity.

MnBi₂Te₄ has garnered substantial scientific interest due to its status as the first intrinsic antiferromagnetic (AFM) topological insulator and its ability to host quantum anomalous Hall insulator and axion insulator states within 2D thin layers. In the bulk form, MnBi₂Te₄ has been theoretically anticipated to host an ideal time-reversal symmetry-breaking type-II Weyl semimetal (WSM) state in the ferromagnetic (FM) phase.

Nonlinear optical (NLO) crystals play a crucial role in converting laser light from one color to another using nonlinear optical processes, enabling a wide spectrum of applications such as optical communications, sensing, imaging, spectroscopy, aviation, and security. While they are mainly operational in the visible region, there are only a few crystals that work in the infrared.

Two-dimensional metals stabilized at the interface between graphene and SiC are attracting considerable interest thanks to their intriguing physical properties, providing promising material platforms for quantum technologies. However, the nanoscale picture of the ultrathin metals within the interface that represents their ultimate two-dimensional limit has not been well captured. In this work, we explore the atomic structures and electronic properties of atomically thin indium intercalated at the epitaxial graphene/SiC interface by means of cryogenic scanning tunneling microscopy.

Van der Waals epitaxy, a unique growth mechanism that relies on weak intermolecular forces between the depositing film and substrate, plays a pivotal role in the synthesis of 2D layered chalcogenides such as MoS₂, WSe₂ and related materials. By illuminating the intricacies of this growth mode using a combination of synthesis, characterization and theory/simulation, researchers affiliated with the 2D Crystal Consortium Materials Innovation Platform are enabling precise control over the nucleation and subsequent lateral growth of 2D materials.