122 research outputs found
Characterizing the Structure of Topological Insulator Thin Films
We describe the characterization of structural defects that occur during
molecular beam epitaxy of topological insulator thin films on commonly used
substrates. Twinned domains are ubiquitous but can be reduced by growth on
smooth InP (111)A substrates, depending on details of the oxide desorption.
Even with a low density of twins, the lattice mismatch between (Bi,Sb)2Te3 and
InP can cause tilts in the film with respect to the substrate. We also briefly
discuss transport in simultaneously top and back electrically gated devices
using SrTiO3 and the use of capping layers to protect topological insulator
films from oxidation and exposure
Inverse Design of Terahertz Nanoresonators through Physics-Informed Machine Learning
The rapid development of 6G communications using terahertz (THz)
electromagnetic waves has created a demand for highly sensitive THz
nanoresonators capable of detecting these waves. Among the potential
candidates, THz nanogap loop arrays show promising characteristics but require
significant computational resources for accurate simulation. This requirement
arises because their unit cells are 10 times smaller than millimeter
wavelengths, with nanogap regions that are 1,000,000 times smaller. To address
this challenge, we propose a rapid inverse design method for terahertz
nanoresonators using physics-informed machine learning, specifically employing
double deep Q-learning combined with an analytical model of the THz nanogap
loop array. Through approximately 200,000 iterations in about 39 hours on a
middle-level personal computer (CPU: 3.40 GHz, 6 cores, 12 threads, RAM: 16 GB,
GPU: NVIDIA GeForce GTX 1050), our approach successfully identifies the optimal
structure, resulting in an experimental electric field enhancement of 32,000 at
0.2 THz, 300% stronger than previous achievements. By leveraging our analytical
model-based approach, we significantly reduce the computational resources
required, providing a viable alternative to the impractical numerical
simulation-based inverse design that was previously impractical
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