Metal-organic coordination can be utilized to direct layer-by-layer (LBL) assembly of thin films.  With sequential deposition of the organic and metal component on the surface, tailoring of film structure and composition is permitted.  Controlled step-wise assembly defines the resulting film structure, presenting an opportunity to design the framework for specific applications.  Toward this realization, this research focuses on understanding the fundamentals of film formation for two types of metal-organic coordinated thin films, multilayers (MLs) and frameworks (MOFs).  The ML system studied was an assembly of a,?-mercaptoalkanoic acids and Cu (II) ions and the MOF system was composed of benzene-1,3,4-tricarboxylic acid and Cu (II) ions (HKUST-1, Cu3(btc)2).  Throughout the alternating solution-phase deposition, films were characterized using ellipsometry to measure film thickness and scanning probe microscopy (SPM) to map topographical morphology of film growth LBL.  Using image analysis software, quantitative data regarding the growth of these thin films based on the images was procured (e.g. Particle Analysis and Percent Area Coverage).  For both ML and MOF systems, ellipsometry shows that film thicknesses uniformly increase by 2 nm per layer deposited.  However, SPM images of the foundational film layers reveal two distinct growth mechanisms, one that forms a semi-continuous conformal film with distinct features (ML) and one that forms a rough surface of nucleating crystallites (MOF).  Work is underway to determine how many layers are necessary for the MOFs to form a continuous film and to investigate if the growth mechanism transitions at that point.  Further studies will investigate the effect of processing variables such as morphology of underlying substrate, chemical functionality of organic binding layer, and post-deposition annealing.

Layer-by-layer assembly and characterization of metal-organic coordinated thin films

247th National Meeting (2014)

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