Banca de DEFESA: HIGO DE ARAUJO OLIVEIRA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : HIGO DE ARAUJO OLIVEIRA
DATE: 21/09/2023
TIME: 14:00
LOCAL: Através de Videoconferência: https://meet.google.com/jci-ygzi-qct
TITLE:

Thermal conductivity calculation in Si membranes: a Homogeneous Non Equilibrium Molecular Dynamics approach

KEY WORDS:

Silicon Membranes. Thermal conductivity. Phonons. Defects. Molecular Dynamics.

PAGES: 74
BIG AREA: Ciências Exatas e da Terra
AREA: Física
SUMMARY:

In this work, we calculated the thermal conductivity of Si(110) membrane with a thickness
of a single unit cell (5.431Å), using the out-of-equilibrium homogeneous non-equilibrium
molecular dynamics (HNEMD) method. The calculated conductivity using this method for
these membranes exhibits a size dependence with respect to to the x, y plane dimensions, but
shows convergence for sizes larger than 𝐿 × 𝐿 with 𝐿 = 30.72 nm. The conductivity is found
to be 61.73 (𝜎 = 2.5) W/m/K.
We also employed the spectral decomposition method of heat flux to separate the average
contribution of vibrational modes (phonons) to thermal conductivity. This analysis revealed
that the major contribution comes from low-frequency modes (𝑓 ≤ 4.5 THz). Additionally,
decomposing the conductivity into in-plane and out-of-plane components allows us to show
that the in-plane components (longitudinal acoustic modes) are the predominant ones. It was
observed that the introduction of periodic defects in these membranes reduces the conductivity
value by around 90% . This reduction also depends on the defect’s geometrical shape. We
tested circular, square, and equilateral triangle shapes for the same removed material density
(different shapes with same area). The reduction is approximately 90% for squares (𝜅𝑥 = 6.037
W/m/K) and circles (𝜅𝑥 = 6.116 W/m/K), while it is 95% for triangles (𝜅𝑥 = 3.290 W/m/K).
This suggests that the phonon scattering at the defect interface depends not only on the
removed material density, as already known in literature, but also on the geometric shape of
the inserted defects.

COMMITTEE MEMBERS:
Externo à Instituição - DAVIDE DONADIO
Presidente - 2457464 - LUIZ FELIPE CAVALCANTI PEREIRA
Interno - 2378411 - RENE RODRIGUES MONTENEGRO FILHO