Size-controllable synthesis of 2D Mn3O4 triangular-shaped nanosheets by thermal chemical vapor deposition

• Main Authors: Hamzan, Najwa, Goh, Boon Tong, Yeoh, Keat Hoe, Chew, Khian-Hooi
• Format: Article
• Published: Elsevier 2022
• Subjects: QC Physics; QD Chemistry
• Online Access: http://eprints.um.edu.my/42217/

In this study, monolayer up to few-layer of Mn3O4 nanosheets grown on c-Si (111) substrates using a thermal chemical vapor deposition (TCVD) technique were investigated in detail, where the growth reaction pressure was varied from 0.12 to 0.72 mbar. The morphology of the triangular-shaped Mn3O4 nanosheet greatly depends on the atomic ratio of O to Mn, which eventually determines the horizontal growth rate of the triangle's edges that forms the shape of the nanosheet. A low O/Mn ratio results in the formation of a triangle with a longer edge as compared to a high O/Mn ratio which produces a shorter edge. The 2D triangular-shaped Mn3O4 nanosheets prepared at 0.42 mbar exhibited a thickness of -1.10-2.29 nm (equivalent to the approximate thickness of monolayer-bilayer) with a maximum edge length of -850 nm, whereas ultrathin nanosheets with a thickness of -1.93-4.68 nm (equivalent to -2-3 layers) with an edge length of <250 nm were found at the highest reaction pressure of 0.72 mbar. The results imply a synthesis of 2D Mn3O4 nanosheets with controllability of thickness and edge length that vary from monolayer to ultrathin nanosheets at different O/Mn ratios. By presuming that the Mn3O4 growth along the 001] direction, we performed first-principles density-functional theory calculations to validate the structure and electronic properties of these 2D Mn3O4 nanosheets. Our calculated lattice parameters for the 2D Mn3O4 were considerably close to the experimental measurements. The band structure calculations predicted that the 2D Mn3O4 possessed metallic characteristics. This paper discusses the seed-assisted growth mechanism of these 2D Mn3O4 nanosheets.