Supersonic jet deposition of silver nanoparticle aerosols: Correlations of impact conditions and film morphologies

Abstract

We describe experiments and modeling for the deposition of silver lines and films via the impaction of a silver nanoparticle aerosol delivered through a supersonic jet. The aerosol gas dynamics of the jet flow field, nanoparticle acceleration in the jet, and deposition by impaction onto the substrate were modeled for both a flat-plate nozzle and for a conical nozzle designed to obtain higher impaction velocities. We modeled nanoparticle dynamics for He, Ar, and N2 gasses, all initially at room temperature and 1 atm pressure, flowing through a 250 μm orifice into vacuum with a pressure ratio of ~5000. Experiments were conducted to deposit silver nanoparticle aerosols under the same conditions as were modeled. The silver nanoparticles were generated by laser ablation of a flowing microparticle aerosol entrained in either He or Ar that produced nanoparticles 5−10 and 15−20 nm in diameter, respectively. Deposition was made onto an unheated substrate in vacuum. The morphology of the deposited films was determined by scanning electron microscope cross-section images and crystallite size was determined by x-ray diffraction analysis. The morphological features and crystallite size were correlated with the nanoparticle impaction velocity and impaction energy derived from the model. We found that, for a given gas type, the size of the grains and morphological features within the impacted films were similar to the size of the nanoparticles from which the films were formed. The density and the degree of consolidation of the films were highly dependent on the nanoparticle impaction velocity/energy and were highest for helium. Control of film morphology, grain size, and film density during supersonic impaction of nanoparticle aerosols are discussed in light of these results.

Deformation of Porous, Nanostructured Silver at Room Temperature and 150 °C

“…The writing speed was set at 0.6 mm/s and films were written in 30 passes, resulting in a film thickness of about 25 µm. SEM observations revealed that the films are nanoparticulate with a 10-20 nm length scale and intraparticle porosity [1]. XRD Scherrer analysis confirmed that the grain size was in the range of 11.2-26.4 nm [1].…”

“…Gas dynamics during the acceleration of the flow have been studied previously [1] and calculations show that the NPs reach a speed of approximately 1000 m/s upon impaction, which is sufficient for them to stick and form cohesive films with a relative density of ~70%. A silicon substrate was placed below the nozzle to collect the NPs, and was mounted on a computer controlled translation stage to enable the writing of films.…”

“…The physics of nanoparticle formation at fluences above the breakdown threshold have been discussed previously [6]. For the experimental conditions used for this study, this process produces NPs with a mean diameter of approximately 5 nm, with a narrow size distribution [1]. The aerosol microparticle feed rate used for the experiments was set at ~10 mg/hr.…”

Synthesis and characterization of permalloy nanostructured films by deposition of laser ablated nanoparticles

“…The LAMA process has been described in detail elsewhere [5][6][7]. In summary, a KrF excimer laser with wavelength of 248 nm, pulse width of 12-15 ns, and repetition rate of 200 Hz was focused onto a microparticle aerosol stream that was confined by a coaxial buffer gas.…”

“…Nanoparticulate thick films can be produced by combining the LAMA process with supersonic impaction. Film densities of 60-80% have been achieved by controlling the gas type and the impaction nozzle geometry [7].…”