Materials Science Seminar: Direct Integration of 2D Materials for Next Generation Electronic Devices

Learn from Zakaria (Zak) Y. Al Balushi as he presents on 2D Materials for next generation electronic devices.

Abstract:
Two-dimensional (2D) semiconductors offer promising pathways beyond the scaling limits of silicon electronics, but their wafer-scale synthesis and direct integration into functional devices remain significant challenges. In the first part of this talk, I will present a wafer-scale, conformal strategy for growing continuous mono- to few-layer metal sulfides. Demonstrated across six compounds and multiple polytypes, the method uses spin-coated, single-source organosulfur precursors derived from dithioacids. Molybdenum ethyl xanthate, for example, decomposes below 200 °C to form a metastable, sulfur-rich amorphous ₃ intermediate that governs the nucleation and growth of MoS 2 during annealing. In situ spectroscopy and microscopy, reactive molecular dynamics, and density functional theory reveal how precursor chemistry controls crystallization, thickness, grain size, and defect formation. The resulting monolayers exhibit optical properties comparable to exfoliated materials and conformally coat high-aspect-ratio structures. The reactive intermediate also enables substrate-selective growth, seed-free integration of atomic-layer-deposited dielectrics, transfer-free superlattice fabrication, and substitutional doping through precursor co-formulation. The films support reliable field-effect transistors and vertical memristors exhibiting nanosecond spike-timing-dependent plasticity. This general chemistry provides a scalable route toward manufacturable 2D electronics. The second part of my talk will describe a selective-area method for tuning the work function and carrier density of monolayer graphene. Sub-monolayer gallium is precipitated beneath graphene from an ion-implanted diamond-like carbon film. Controlling the annealing temperature enables spatially precise, ambient-stable ambipolar doping, with carrier densities ranging from approximately 1.8 × 10 10 cm -2 hole-doped to 7 × 10 13 cm -2 electron-doped. Theory and experiments confirm that interfacial gallium governs charge transfer to the graphene. Extending this approach to other elements that can be implanted into diamond-like carbon offers a versatile platform for investigating highly doped 2D materials and emerging heterostructures.

Biography:
Zak Al Balushi is an assistant professor in the department of Materials Science and Engineering at University of California, Berkeley, and a faculty scientist in the Materials Science Division at the Lawrence Berkeley National Laboratory. Zakaria received his B.S. (2011), M.S. (2012) in Engineering Science and his Ph.D. (2017) in Materials Science and Engineering all from The Pennsylvania State University. His early work focused on integration and fabrication of silicon nanowire devices, then on the growth of group-III nitride semiconductors, in situ metrology during MOCVD growth, epitaxial graphene and the discovery and characterization of unconventional low-dimensional materials and heterostructures. Prior to his appointment at the University of California, Berkeley, he held two postdoctoral fellowships: the Resnick Prize Fellowship in Applied Physics and Materials Science and the NSF Alliances for Graduate Education and the Professoriate (AGEP) Fellowship both at the California Institute of Technology under the supervision of Professor Harry Atwater. At the University of California, Berkeley, his research group continues to expand in this area and beyond, creating new synthesis and integration schemes for emerging low-dimensional materials. He is currently serving on the editorial board of Communications Materials, is an elected executive committee member for the American Association for Crystal Growth and recently named “Four rising stars who are reshaping nanoscience” by Nature [Nature 608, S12-S13 (2022)]. He is also a SK Hynix Faculty Fellow, Society of Hellman Fellow, a CIFAR Azrieli Global Scholar in Quantum Materials and a recipient of the NSF CAREER and Micron Corporation Early Career Awards in 2022.

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