Growth of magnetic thin films using CO2 RESS expansions

A continuous-flow rapid expansion of supercritical solution (RESS) apparatus is used to grow thin iron oxide thin films under ambient and vacuum conditions. The magnetic thin films are produced by expanding a supercritical solution of ferric acetylacetonate (Fe(acac)3) and CO2 and directing the resulting supersonic jet onto both hot and cold silicon wafers. The concentration of the expanding solution is monitored in-line with a UV–vis high pressure view cell which is also used to perform solubility measurements. The resulting films contain nano- and sub-micronic particles in the 13–700 nm size range and show magnetic order. Structural and magnetic data for these thin particle films have been obtained by SQUID and SEM measurements and compared as a function of substrate surface temperature, growth times, and initial solute concentrations. Experimental and theoretical analysis of the thermodynamics and fluid mechanics appropriate for this RESS process is discussed.