Nanomaterials and Nanoelectronics

Since the discovery of graphene in 2004, the field of two-dimensional (2D) materials has expanded into a rich family of layered semiconductors, insulators, and metals with over a thousand candidates now identified. These materials are only a single atomic layer thick, which means that electrons are confined in an ultra-thin plane and behave fundamentally differently than in their bulk, three-dimensional counterparts. This reduced dimensionality leads to strongly modified band structures, enhanced Coulomb interactions, and remarkably tunable optical and electronic properties that can be engineered with precision. Materials such as graphene, monolayer transition metal dichalcogenides, and hexagonal boron nitride have become essential platforms for studying new quantum phenomena and designing device architectures beyond the limits of traditional semiconductors. Because of the dangling bond-free nature of 2D materials, they can be stacked in any order and on top of 3D materials or nanophotonic components without lattice mismatch restriction. As conventional silicon technologies approach physical scaling limits, 2D materials offer new pathways toward ultrathin transistors, compact optoelectronic devices, neuromorphic computing elements, and bioelectronic sensors, to name a few.

Our group's research focuses on identifying promising 2D materials and demonstrating high-performance devices including field-effect transistors, tunneling devices, neuromorphic devices etc. We also investigate the van der Waals heterostructures, where stacking different atomic layers creates new electronic and optical behaviors. To understand and optimize material behavior at the nanoscale, we use advanced characterization techniques such as transmission electron microscopy, Raman spectroscopy, atomic force microscopy and Kelvin probe force microscopy. Through this approach, we directly relate nanoscale material properties to the device behavior and performance, with the aim to uncover new physical phenomena and lay the foundation for next-generation nanoelectronics.

2D Material Exfoliation and Transfer

We work with a wide range of 2D materials that are either synthesized on large areas using CVD and MOCVD techniques or mechanically exfoliated from high-quality bulk crystals. We isolate monolayers or few-layer flakes and transfer them onto target substrates in controlled sequences to form desired heterostructures. Throughout this process, we develop scalable fabrication methods that allow us to create hundreds of complex, multi-layer stacks within a single fabrication cycle. For an example of this work, see one of our publications here.

Field-Effect Transistor Devices

Fabricating field-effect transistor (FET) devices allows us to probe the electronic properties of 2D materials in a controlled and quantitative manner. By measuring current–voltage and gate-dependent transport characteristics, we can extract key parameters such as carrier mobility, contact resistance and presence of a Schottky barrier. These measurements also reveal the level and type of doping in the material, as well as the presence and density of defects or trap states that influence charge transport. We perform FET device fabrication using photolithography and EBL techniques. To ensure reliable, large scale and high-quality devices, we continuously develop and refine fabrication methods that preserve the intrinsic properties of the materials and minimize processing-induced disorder. For an example of this work, see one of our publications here.

Transmission Electron Microscopy

Transmission electron microscopy (TEM) provides direct insight into the atomic structure of 2D materials, enabling us to visualize lattice arrangement with sub-nanometer resolution. Because 2D materials are only one or a few atoms thick, TEM is especially powerful for distinguishing structural variations that strongly influence material's electronic and optical properties. For instance, in our recent project we studied how laser illumination can change the phase of PdSe2 leading to formation of much more metallic semiconductor material, see the publication here. By correlating the structural details with device performance, TEM helps us understand how we can control the materials properties at nanoscale.

Raman Spectroscopy

Raman spectroscopy serves as a powerful, non-destructive tool for fingerprinting the properties of 2D materials. Because vibrational modes in these ultrathin crystals are highly sensitive to layer number, strain, doping, and defects, Raman spectra provide a direct and reliable way to identify material composition and monitor changes in its electronic environment. In 2D systems, even subtle shifts in peak position, intensity, or linewidth can reveal information about interlayer coupling, doping or the presence of disorder. By investigating these spectral signatures, Raman spectroscopy allows us to quickly evaluate material quality and directing precise tuning of local electronic and structural properties. We also use surface-enhanced Raman spectroscopy (SERS) to amplify vibrational signals and fingerprint molecules at very low concentrations. See our paper here.

Atomic and Kelvin Probe Force Microscopies

Atomic force microscopy (AFM) allows us to map the topography of 2D materials with nanometer precision, providing information about surface roughness, thickness, grain structure, and mechanical properties. Kelvin probe force microscopy (KPFM), an extension of AFM, further enables spatial mapping of surface potential and local work function. This allows us to visualize charge distribution and doping variations across a device or heterostructures. Together, AFM and KPFM offer a powerful platform for correlating nanoscale morphology and surface electronic properties with material behavior and device characteristics. See an example of our past work here.

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