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Título: CHEMICAL, STRUCTURAL, TRIBOLOGICAL, AND OPTICAL PROPERTIES OF HEXAGONAL BORON NITRIDE FILMS SYNTHESIZED BY CHEMICAL VAPOR DEPOSITION
Autor: THAIS CRISTINA VIANA DE CARVALHO
Instituição: PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO - PUC-RIO
Colaborador(es):  MARCELO EDUARDO HUGUENIN MAIA DA COSTA - ADVISOR
CESAR AUGUSTO DIAZ MENDOZA - CO-ADVISOR

Nº do Conteudo: 67676
Catalogação:  22/08/2024 Liberação: 22/08/2024 Idioma(s):  ENGLISH - UNITED STATES
Tipo:  TEXT Subtipo:  THESIS
Natureza:  SCHOLARLY PUBLICATION
Nota:  Todos os dados constantes dos documentos são de inteira responsabilidade de seus autores. Os dados utilizados nas descrições dos documentos estão em conformidade com os sistemas da administração da PUC-Rio.
Referência [pt]:  https://www.maxwell.vrac.puc-rio.br/colecao.php?strSecao=resultado&nrSeq=67676&idi=1
Referência [en]:  https://www.maxwell.vrac.puc-rio.br/colecao.php?strSecao=resultado&nrSeq=67676&idi=2
Referência DOI:  https://doi.org/10.17771/PUCRio.acad.67676

Resumo:
Hexagonal Boron Nitride (h-BN) is a material composed of alternating Boron (B) and Nitrogen (N) atoms with a hexagonal aspect. Thin films of h-BN play a crucial role in the development of applications such as 2D devices based on Van der Waals heterostructures, protective coatings, tribological applications, among others. The synthesis of h-BN still represents a significant challenge. In this thesis, the synthesis of h-BN was investigated using the low-pressure chemical vapor deposition (LPCVD) method, employing ammonia borane (AB) as a precursor source of B and N. The study focused on direct growth on the silicon <100> substrate, thus eliminating the need for film transfer for subsequent characterization and avoiding degradation and contamination associated with the transfer process. The first part of this study focused on CVD growth, controlling parameters such as the amount of precursor material, precursor and furnace evaporation temperature, gas flow rates during the reduction and synthesis stages, temperature, reduction time, synthesis, and cooling. Two series were synthesized: one as a function of growth temperature between 1173 and 1373 K, and a second as a function of synthesis time at a temperature of 1373 K. The films were characterized by spectroscopy, Raman, Fourier-transform infrared (FTIR), UV-visible (UV-Vis), X-ray photoelectron (XPS), atomic force microscopy (AFM), contact angle measurements, scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), and tribology. Initially, the effect of growth temperature on the quality of films grown for 10 minutes was studied. Raman spectroscopy results confirmed the growth of h-BN, evidenced by the E2g peak at approximately 1375 cm−1 . Morphological studies showed that temperature variations lead to the formation of different structures on the Si surface. Growth is observed from 1273 K, while samples grown below 1223 K show no signs of growth. We observed the formation of two-dimensional (2D) nanosheets with lateral dimensions ranging from 80 to 500 nm, as well as the continuous growth of films with nanocrystals of varying sizes. The B:N ratio determined by XPS was approximately 1:1, and the optical gap of the h-BN films was determined to be 5.75 eV. Tribology studies demonstrated a friction coefficient of 0.1, and there was no delamination after 3000 linear reciprocating cycles in the ball-on-disk test, covering 10 mm in each cycle on the film, while for Si it was 0.6. For films synthesized as a function of time, Raman spectroscopy characterization revealed an E2g vibration mode peak at 1374 cm−1 with intensity correlated to the film thickness. FTIR spectroscopy confirmed the presence of B-N bonds, and the optical band was determined to be 5.65 eV. Contact angle measurements showed hydrophobic films. XPS data indicated a stoichiometric 1:1 ratio between B and N, and the thickness was analyzed by cross-sectional STEM measurements, being around 20 nm for films grown for 10 minutes at 1373 K.

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