TY - JOUR

T1 - Effects of Bond Disorder and Surface Amorphization on Optical Phonon Lifetimes and Raman Peak Shape in Crystalline Nanoparticles

AU - Utesov, Oleg I.

AU - Koniakhin, Sergei V.

AU - Yashenkin, Andrey G.

N1 - Publisher Copyright: © 2021 American Chemical Society.

PY - 2021/8/26

Y1 - 2021/8/26

N2 - Optical phonons in nanoparticles with randomness of interatomic bonds are considered both analytically and numerically. For weak dilute disorder, two qualitatively different regimes of separated and overlapped levels are observed, resembling the case of random atomic masses investigated previously. At stronger and/or more dense disorder, the particles become essentially inhomogeneous, thus constituting a minimal model to describe an amorphous phase, where the picture of vibrational modes becomes more subtle. We concentrate here on the experimentally relevant case of a strong disorder located near the particle surface and formulate the core-shell model aimed to describe the ubiquitous phenomenon of particle surface amorphization. We observe a peculiar effect of volume optical phonons "repelling"from the disordered shell. It results in the Raman spectrum appearing in the form of a combination of narrow well-resolved peaks stemming from the quantized modes of a pure particle core (red-shifted due to its effective smaller size) and a wide pedestal-like signal from the disordered shell, placed primarily to the right of the main Raman peak.

AB - Optical phonons in nanoparticles with randomness of interatomic bonds are considered both analytically and numerically. For weak dilute disorder, two qualitatively different regimes of separated and overlapped levels are observed, resembling the case of random atomic masses investigated previously. At stronger and/or more dense disorder, the particles become essentially inhomogeneous, thus constituting a minimal model to describe an amorphous phase, where the picture of vibrational modes becomes more subtle. We concentrate here on the experimentally relevant case of a strong disorder located near the particle surface and formulate the core-shell model aimed to describe the ubiquitous phenomenon of particle surface amorphization. We observe a peculiar effect of volume optical phonons "repelling"from the disordered shell. It results in the Raman spectrum appearing in the form of a combination of narrow well-resolved peaks stemming from the quantized modes of a pure particle core (red-shifted due to its effective smaller size) and a wide pedestal-like signal from the disordered shell, placed primarily to the right of the main Raman peak.

KW - X-RAY-DIFFRACTION

KW - NANODIAMOND

KW - SPECTRA

KW - SPECTROSCOPY

KW - CARBON

KW - SIZE

KW - TRANSFORMATION

KW - CHEMISTRY

KW - SILICON

KW - ENERGY

UR - http://www.scopus.com/inward/record.url?scp=85113982227&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/a08ca322-3fdc-3051-9816-3023209ceaf3/

U2 - 10.1021/acs.jpcc.1c04007

DO - 10.1021/acs.jpcc.1c04007

M3 - Article

AN - SCOPUS:85113982227

VL - 125

SP - 18444

EP - 18455

JO - Journal of Physical Chemistry C

JF - Journal of Physical Chemistry C

SN - 1932-7447

IS - 33

ER -