Sputtering of size-tunable oxidized Fe nanoparticles by gas flow method
Systematic optimization of sputter parameters allowed the growth of size-tunable ferric nanoparticles on glassy-carbon substrates using gas flow sputtering technique. By variation of the sputtering pressure and particle aggregation length, Fe nanoparticles with mean diameter ranging between 20 and 150 nm were formed. Several physical and optical techniques were used to examine the size and morphology of the nanoparticles. While nanoparticles were revealed as spherical, their crystalline structure was detected only for the hematite type of Fe. By fostering the sputtering growth using Ar and He admixture flow, density variation within the grown particles was established, offering a strategy to overcome the slow growth rates in the sputter sources. Magnetization measurements taken at room temperature did not show evidence of the impact of size on the magnetic properties of the nanoparticles. Thus, saturation magnetization and coercivity values were obtained. Measurements of the linear optical properties of the sputtered nanoparticles showed a general decrease in extinction with decreasing nanoparticle size. Monotonically decreasing spectra were observed, except for a shoulder in the 300–400 nm range.