TY - JOUR

T1 - Study of localized phonon in ultrananocrystalline diamond films investigated by Raman spectroscopy

AU - Kumar, N.

AU - Kozakov, A. T.

AU - Panda, Kalpataru

AU - Nikolskii, A. V.

AU - Milekhin, I. A.

AU - Khamatdinov, E. U.

AU - Volodin, V. A.

AU - Goryainov, S. V.

AU - Milekhin, A. G.

N1 - A.T. Kozakov and A.V. Nikolsky are grateful to the Ministry of Science and Higher Education of the Russian Federation for financial support (State Assignment in the Sphere of Scientific Activity 2023 No. FENW-2023-0014), S.V. Goryainov thanks for support the Russian Federation state assignment of the Sobolev Institute of Geology and Mineralogy SB RAS (state registration number: 122041400176-0), grant from Ministry of science and higher education of Russia FSUS-2024-0020 and shared research center VTAN at NSU, support by the state assignment of ISP SB RAS is also acknowledged, Kalpataru Panda acknowledges to the Manipal Academy of Higher Education (MAHE) for their financial support to carry out the research activities, late Prof. I Nan Lin (Department of Physics, Tamkang University, Taiwan) is acknowledged for the technical support.

PY - 2025/12

Y1 - 2025/12

N2 - The study employed multiwavelength excitation (UV-ultraviolet, visible and near infrared) of Raman spectroscopy to probe resonant and non-resonant scattering mechanisms in ultrananocrystalline diamond (UNCD) films, exploring wavelength-dependent phonon dispersion, defect-activated modes, and interfacial vibrations of grain boundaries. UV excitation enhanced the diamond D* peak due to resonant coupling with zone-center optical phonons, while visible and near infrared spectra highlighted amorphous carbon (a-C)/sp2-rich grain boundary contributions (D, G, and trans-polyacetylene (t-PA) modes). Temperature-dependent studies (cryogenic to room temperature) demonstrated anomalous phonon behavior: the D and G bands redshift due to anharmonicity, while the v2mode of t-PA blueshifts from reduced Peierls distortion. Laser power-dependent measurements revealed thermal strain effects, with hardening of phonon mode inducing initial blueshifts followed by thermal redshifting at higher powers. Polarization-resolved spectroscopy identifies symmetry breaking at grain boundaries, evidenced by anisotropic scattering of the v3mode. The heat capacity of UNCD, calculated via Einstein and Debye models, deviates from bulk diamond due to low-energy vibrational and defect modes.

AB - The study employed multiwavelength excitation (UV-ultraviolet, visible and near infrared) of Raman spectroscopy to probe resonant and non-resonant scattering mechanisms in ultrananocrystalline diamond (UNCD) films, exploring wavelength-dependent phonon dispersion, defect-activated modes, and interfacial vibrations of grain boundaries. UV excitation enhanced the diamond D* peak due to resonant coupling with zone-center optical phonons, while visible and near infrared spectra highlighted amorphous carbon (a-C)/sp2-rich grain boundary contributions (D, G, and trans-polyacetylene (t-PA) modes). Temperature-dependent studies (cryogenic to room temperature) demonstrated anomalous phonon behavior: the D and G bands redshift due to anharmonicity, while the v2mode of t-PA blueshifts from reduced Peierls distortion. Laser power-dependent measurements revealed thermal strain effects, with hardening of phonon mode inducing initial blueshifts followed by thermal redshifting at higher powers. Polarization-resolved spectroscopy identifies symmetry breaking at grain boundaries, evidenced by anisotropic scattering of the v3mode. The heat capacity of UNCD, calculated via Einstein and Debye models, deviates from bulk diamond due to low-energy vibrational and defect modes.

KW - Ahharmonic coupling

KW - Grain boundaries

KW - Localized phonon

KW - Phonon decay

KW - Specific heat

KW - Ultrananocrystalline diamond

UR - https://www.scopus.com/pages/publications/105020441738

UR - https://www.mendeley.com/catalogue/9f797085-ca20-338c-a39f-24b3b4d0e6de/

U2 - 10.1016/j.diamond.2025.112941

DO - 10.1016/j.diamond.2025.112941

M3 - Article

VL - 160

JO - Diamond and Related Materials

JF - Diamond and Related Materials

SN - 0925-9635

M1 - 112941

ER -