Heteroepitaxial van der Waals semiconductor superlattices

Abstract

We report atomic layer-by-layer epitaxial growth of van der Waals (vdW) semiconductor superlattices (SLs) with programmable stacking periodicities, composed of more than two kinds of dissimilar transition-metal dichalcogenide monolayers (MLs), such as MoS2, WS2 and WSe2. The kinetics-controlled vdW epitaxy in the near equilibrium limit by metalorganic chemical vapour depositions enables to achieve accurate ML-by-ML stacking, free of interlayer atomic mixing, resulting in the tunable two-dimensional (2D) vdW electronic systems. We identified coherent atomic stacking orders at the vdW heterointerfaces, and present scaling valley polarized optical excitations that only pertain to a series of 2D type II band alignments.

Characteristic Changes in First-Visit Patients with Peripheral Facial Palsy before and during COVID-19 Pandemic: Focused on a Korean Medicine Hospital

“…The proportion of patients who received both outpatient and inpatient treatment persistently decreased, but the proportion of patients who received only outpatient treatment persistently increased during COVID-19. This decrease is similar to that in a previous study, where the number of people visiting medical institutions for admissions decreased during the COVID-19 outbreak [36]. Several complex factors may have played a role in this process.…”

“…In the early days of the COVID-19 epidemic in South Korea, the pandemic spread rapidly in medical and living facilities [37]. Moreover, inpatients experienced higher levels of anxiety about infection than outpatients [36]. In addition, although facial palsy hinders the quality of life and affects social life, it is not a life-threatening condition [38].…”