| AVS 60th International Symposium and Exhibition | |
| Plasma Science and Technology | Thursday Sessions |
| Session PS+AS+NS+SS-ThM |
| Session: | Plasma Synthesis of Nanostructures |
| Presenter: | C.J. Hogan, University of Minnesota |
| Authors: | C.J. Hogan, University of Minnesota A. Kumar, Case Western Reserve University S. Kang, University of Minnesota C. Larriba-Andaluz, University of Minnesota H. Ouyang, University of Minnesota R.M. Sankaran, Case Western Reserve University |
| Correspondent: | Click to Email |
Using a high resolution differential mobility analyzer (1/2-mini DMA, Nanoengineering) coupled to a Faraday cage electrometer for ion mobility spectrometry, we have investigated the formation of Ni clusters in a DC atmospheric pressure Ar microplasma. To produce Ni clusters, nickelocene (bis(cyclopentadienyl)nickel) vapor was continuously introduced into the microplasma by sublimation of a heated solid powder into an Ar gas flow. Particles were nucleated, grown, and rapidly quenched to limit their diameter to less than ~10 nm. Prior to mobility measurement, a steady-state charge distribution of the aerosol particles was achieved via diffusion charging with background gas ions produced in a Kr-85 source (TSI, Inc.). Both positive and negative mobility distributions were measured. A background high intensity peak around ~0.75 nm equivalent “mobility diameter”, corresponding to the ions produced by the Kr-85 source, was always observed. The introduction of nickelocene vapor in the microplasma resulted in a lower intensity distribution of particles, spanning from the peak corresponding to Kr-85 generated ions to 10 nm in mobility size. Under all circumstances, the mobility distribution from the ion peak to the largest produced particles was continuous, indicating the microplasma reactor can form stable Ni clusters below 2.0 nm in size. To obtain structure-mobility relationships, density functional theory and gas molecule scattering calculations were carried out. The nanoparticles were also collected by electrostatic precipitation and further characterized by atomic force microscopy to confirm their size and distribution. These results confirm a that a continuous distribution of particles is formed in microplasma processes down to less than 1.0 nm which could have both fundamental and technological implications ranging from the study of particle formation in the vapor phase to novel applications of quantum confined materials.