Chemical control of the oxidation state of the metal and the morphology of nanostructures and films deposited by metalorganic vapor deposition

Abstract

Metal deposition has a wide range of applications in many fields, from nano-fabrications to catalytic reactions. Hence, it is important to understand the basic chemical mechanism of the deposition process. In this work, two major target metals, silver and copper, are investigated for the effective deposition by metalorganic vapor deposition approach. In particular, Chapter 1 gives a general overview of the importance and applications of metal deposition in different fields. Specifically, the reactions of different metalorganic precursors containing either copper or silver are addressed. Chapter 2 describes materials and experimental and computational methods used. Experimental investigation of the deposition of copper and silver-containing precursors on different substrates is described in Chapter 3. It is found that a specific controlled surface morphology can be obtained by changing the reaction parameters, such as pressure, dosing time, and temperature. It is also found that the choice of the substrate functionalities affect the final morphology of the nanostructure on the surface. For example, an H-terminated silicon surface was found to be less reactive to the silver precursor (hfac)AgP(CH3)3 (trimethylphosphine(hexafluoroacetylacetonato)silver(I)) than an HO-terminated silicon surface. ☐ Apart from controlling the morphology of the nanostructure and the oxidation state of the metal, other studies involving the role of the metal oxide, specifically CuO, in H2S sensing and poisoning was also investigated and discussed in Chapter 4. It was found that the CuO component was reduced and oxidized back and forth when exposed to H2S and O2, respectively, hence affecting the sensing performance of the sensor. ☐ Computational investigations are also performed and discussed in Chapter 5 to deconvolute the steric and electronic effects for the reactions between metalorganic precursors and silicon surfaces. In particular, a bulky precursor TDMAT (tetrakis(dimethylamido)titanium) and a much smaller precursor TMA (trimethylaluminum) were compared. By changing the size, as well as the type of the surface substituents, steric and/or electronic effects can be distinguished.