Engineering Inorganic Thin Films and Nanoparticles from Molecular Coordination Precursors

Abstract

Abstract Multimodal nanomaterials integrate complementary chemical, optical, and physical functionalities into a single nanoscale object, and have potential applications in numerous fields. A versatile surface chemistry of transition metal oxide and chalcogenide nanomaterials are ideal multimodal platforms. This project has focused on synthesizing 2D nanomaterials and nanocrystals primarily based on transition metal chalcogenides (TMCS) (e.g., MoS2, WS2, V2S3, MoSe2, WSe2, and VSe2) and transition metal oxides (TMO). Three vanadyl complexes, [VO(S2CNEr2)2] (1), [VO(S2CNEr2)4] (2), and [VO(S2CNiPr2)3] (3), have been synthesized and fully characterized to be used as a single source precursors of nanomaterials. Rhombohedral phase of V2O3 thin films were produced from 1, 2 and 3 by Aerosol Assisted Chemical Vapour Deposition (AACVD). The effect of changing the precursor and the deposition temperature has been probed by p-XRD and SEM. The novel complex [VO(S2CNPr2)3](3) probed to be uniquely placed to act as an efficient tetra-modal precursor for the production of both vanadium oxides (VO2, V2O3) and chalcogenides (V2S3, VS) products by judicious choice of reaction conditions employed. In the next work, the syntheses of [MoV 2S4O2(S2CNEt2)2] (4), [MoVS2O(S2CNEt2)2] (5) and [WV 2S4(S2CNiPr2)2] (6) complexes have been described along with the full characterization of their crystal structures and thermogravimetric behaviour. The metal complexes were used as novel single source precursors to deposit metal sulfide nanomaterials in the form of thin films by AACVD. Hexagonal phases for both MoS2 and WS2 thin films were produced and confirmed by p-XRD, SEM, EDX, and Raman spectroscopy. The films are paramagnetic, without showing a magnetic hysteresis loop. In the next stage of this work, quaternary alloyed Mo0.9-xWxV0.1S2 thin films were synthesized via AACVD using [Mo2S4O2(S2CNEt2)2] (4), [W2S4(S2CNiPr2)2] (6) and [VO(S2CNiPr2)3] (3) as precursors. The preferred orientation of the crystals within the films was found to be in the (002) basal plane as confirmed by p-XRD. The band gaps of Mo0.9-xWxV0.1S2 thin films varied from 1.45 to 1.55 eV upon increasing the W4+ molar fraction (x). Finally, molecular precursors of selenium were used as a single source precursor to produce metal diselenide nanoparticles and thin films. Pure MoSe2, WSe2, and VSe2 nanomaterials have been synthesized via solventless thermolysis and AACVD methods, and were fully characterized by p-XRD, SEM, EDX, Raman .spectroscopy, and SQUID magnetometry