Discovery of Novel Photonic Phenomena in Mixed-Dimensional Heterostructures
Abstract
The isolation of graphene on an insulating surface in 2004 was a watershed moment in condensed matter physics and materials science, which ultimately led to the search for additional two-dimensional (2D) materials. The emergence of both structural as well as electronic variety in van der Waals (vdW)-bonded layered materials has opened new avenues for fundamental scientific studies and applied device designs. As a consequence, several combinations of distinct 2D layers have been assembled to create vdW heterostructures with varying functionalities. These all-2D vdW heterostructures exhibit unique properties such as gate-tunability, imbuing them with potentially novel functionality versus conventional devices as summarized in several recent reviews However, it remains a challenge to produce entire families of 2D materials and their heterostructures over large areas with high electronic quality. Furthermore, control of doping type, carrier concentration, and stoichiometry remain outstanding challenges in the majority of 2D materials, limiting the scope and progress of all-2D vdW heterostructures. Van der Waals interactions however, are not limited to interplanar interactions in layered materials. Any passivated, dangling bond-free and oxide free surface interacts with another similar surface via vdW forces. Consequently, any layered 2D material can be integrated with an array of materials of different dimensionality to form mixed-dimensional vdW heterostructures. Such combinations of 2D + n-D (n = 0, 1 and 3) materials have begun to emerge and represent a much broader class of vdW heterostructures for further study. The goal of this project is to gain fundamental understanding of charge transport, transfer and photon emission mechanisms at atomic and molecular scale interfaces via assembly and engineering of new structures and interfaces, hitherto unexplored in quantum materials. The material classes under consideration are two-dimensional (2D) semiconductor materials of structure MX2 and AX (M=Mo, W, Re; A= In, Ga; X= S, Se, Te) and zero-dimensional (0D) quantum dots (QDs) of the Cd and Pb chalcogenide family, one-dimensional (1D) materials such as carbon nanotubes as well as quasi 1D van der Waals materials such as elemental Se and Te. Structure-property relationships dictating quantization and localization of tightly bound excited states (excitons) based on the symmetry and interfacial chemistry will be established using confluence of synthesis and characterization techniques: metal organic chemical vapor deposition (MOCVD), scanning near-field optical microspectroscopy (SNOM) tip enhanced Raman scattering (TERS) as well as far field photoluminescence (PL) and absorption spectroscopy. The objectives are to: i.Develop a controlled mixed-dimensional (2D+nD) heterostructure using growth, nanofabrication and colloidal self-assembly techniques ii.Measure the absorption and luminescence properties in both near and far field to determine the nature of excitons and charge transfer iii.Measure charge transport and photocurrent to understand the nature of band bending and alignment at the junction iv.Exploit this system to understand effect of interface atomic and electronic structures on the luminescent property and lifetime of excitons as well as controlling band alignments This program will culminate with charge-transfer, photon emission and band alignment guidelines based on interface atomic and electronic structure of 2D-nD (n=0,1) materials heterostructure systems thereby leading to a new paradigm of a static and dynamically tunable interface for optical modulators, light emitting diodes, single photon emitters and lasers for integration into next-generation military technologies.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 14, 2019
- Source ID
- W911NF1910109
Entities
People
- Deep Jariwala
Organizations
- Army Contracting Command
- United States Army
- University of Pennsylvania