Deposition of thin organic and metal films from carbon dioxide by free meniscus and solvent displacement methods

This thesis investigates the use of liquid carbon dioxide (1-CO2) and supercritical carbon dioxide (scCO2) as coating solvents to deposit small organic molecules, polymers and metal films. The low cost, low toxicity and unique physical properties of 1-CO2 and scCO2, including extremely low surface tension, low viscosity, and tunable density, make them appropriate coating media to overcome some of the constraints associated with traditional coating methods. Two novel pieces of equipment, a high-pressure free meniscus coating (hFMC) apparatus and an apparatus for film deposition by displacement from two immiscible supercritical phases (DISP), were designed and constructed to produce thin films from CO 2 media. It was demonstrated that highly uniform and ultrathin films of sucrose octaacetate (SOA) and poly[(2-perfluorooctyl)ethyl acrylate] (PFOEA) can be formed on substrates consisting of native oxide of silicon (SiOx) using 1-CO2 hFMC. The films deposited from 1-CO2 were much thinner, more uniform, and exhibited much fewer drying defects and lower surface roughness compared to films from typical organic solvents. The unique surface properties of the PFOEA films from 1-CO2 hFMC were also investigated.; The lack of an interfacial boundary associated with the supercritical state of CO2 does not allow its use in traditional liquid-based coating processes. This drawback can be overcome by introducing a fluid such as supercritical He that is not readily miscible with scCO2 to create an interfacial boundary. It has been demonstrated that particles and films of SOA and PFOEA can be deposited on SiOx from the interfacial boundary between a scCO2 phase and a scHe phase using a solvent displacement (DISP) technique. The films deposited from DISP exhibit unique surface morphologies when compared with the films from 1-CO2 hFMC and the films from normal dip coating with organic solvents.; Even though 1-CO2 and scCO2 have valuable properties as coating media, the poor solvent power of CO2 for most of polymeric materials is a major limitation. This limitation can be overcome by depositing polymeric precursors that are soluble in CO2 followed by subsequent polymerization directly on the surface. Ultrathin fluorinated films with optically clear and chemically resistant characteristics were produced by first depositing photocurable perfluoropolyether (alpha-,o-methacryloxy terminated perfluoropolyether) from 1-CO2 hFMC and subsequently curing the deposited films. This deposition/reaction technique can be also utilized in metal film deposition. Nanosize copper particles and copper films were deposited on SiOx or titanium nitride substrates by first producing Cu (II) hexafluoroacetylacetonate hydrate films from DISP and subsequently reducing them in a hydrogen environment. It also has been demonstrated that palladium catalyzed copper deposition using DISP and subsequent reduction can produce highly uniform and ultrathin Cu films.