Spectroscopic Characterization and Modeling and Simulation of Zinc Oxide and Zinc Sulfide Quantum Dots

The piezoelectric properties of zinc oxide and zinc sulfide molecules have brought attention to their use as potential quantum dot qubits. We have analyzed the properties of these molecules and quantum dots to compare their properties. We have run Density Functional Theory (DFT) calculations using the Quantum Espresso and Siesta suites. The modeling resulted in band structure and density of states plots that were complemented by Raman spectroscopy measurements and identification of vibrational modes associated with zinc oxide quantum dots. We calculated the piezoelectric tensor for the 10 nm zinc oxide and zinc sulfide quantum dots and the 2.1 nm zinc sulfide double quantum dot to compare their piezoelectric properties, like the polarization of the system in certain directions, and the overall strength of the piezoelectric tensor. We also present a many-body perturbation GW/Bethe-Salpeter Equation (BSE) approach applied to zinc oxide quantum dots that quantifies uncertainty from basis/truncation/frequency convergence, enforces spherical Coulomb truncation, and provides cross-implementation checks between Wannier-based Excited State Theory (WEST) Projective Dielectric Eigendecomposition (PDEP)-GW and conventional empty-state approach on reduced systems. We have validated the computational recipes with uncertainty quantification protocols for zinc oxide quantum dots (300, 800, 1000 atoms), including Quasiparticle (QP) gaps and Ionization Potential (IP)/Electron Affinity (EA).