Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2016)
    Nanomaterials Tuesday Sessions
       Session NM-TuE

Paper NM-TuE9
Nanoparticles and Nanostructures Synthesis by High-Power Pulsed Hollow Cathode Sputtering

Tuesday, December 13, 2016, 8:20 pm, Room Hau

Session: Nanofabrication and Nanodevices II
Presenter: Ulf Helmersson, Linköping University, Sweden
Authors: U. Helmersson, Linköping University, Sweden
S. Askari, Linköping University, Sweden
N. Brenning, Linköping University, Sweden
S. Ekeroth, Linköping University, Sweden
R. Gunnarsson, Linköping University, Sweden
Correspondent: Click to Email
The use of high-power pulses for synthesis of nanoparticles in the gas phase is of interest because of the effective ionization of the supplied gases and the sputtered source material. The advantage of ionizing the source material is the effective trapping of positive ions onto the negatively charged nanoparticles in the plasma resulting in a significant increase in growth rate and utilization of material. A cylindrical metal hollow cathode was used where sputtering occurs on the internal surface of the cylinder. Apart from that a cathode configuration with a linear slit was employed suitable for roll-to-roll deposition. The sputtered material of ions and neutrals is ejected from the cathode due to the the pressure buildup by the high voltage pulse, due to the outward directed ambipolar electric field structure at the hollow cathode opening and due to the flow of the gas through the cathode. This results in rapid expansion of the sputtered material and it leads to nucleation and growth of nanoparticles. A range of materials has been synthesized by this technique including Fe, Cu, Ti, Ag, Mo, In and Zn. By adding a reactive gas to the process nanoparticles containing Ti-O, Ti-N Zn-O and In-N has been synthesized. Several process parameters were identified to affect the size, size distribution, shape and structure of the nanoparticles. These parameters include pulse power, pulse frequency, sputtering gas composition, gas pressure and geometry of the setup. By tuning these parameters, the nanoparticle size can range from a few nm to more than 250 nm in diameter. Depending on the employed process parameters, the crystal structure of nanoparticles varies from a single crystal with well-defined crystallographic faces to polycrystalline and amorphous cauliflower structures consisting of randomly oriented agglomerates of nano-crystals. In the presentation it will also be shown that the nanoparticles can be used for assembling of different nanostructures.