Competing processes during the production of metal nanoparticles by pulsed laser deposition

Abstract

In this work we report on the competition between growth, implantation, and sputtering effects during the production of metal nanoparticles ͑NPs͒ by pulsed laser deposition. The production sequence involves first the deposition of an amorphous ͑a-͒Al 2 O 3 layer onto which gold NPs are produced. They are subsequently covered by a-Al 2 O 3 and this sequence is repeated five times. The resulting nanocomposite films have metal contents per layer in a broad range: 1 -9 ϫ 10 15 at cm −2 . The results clearly show the formation of two NP layers per layer of gold deposited, the deepest one consisting of NPs produced by metal implanted into the a-Al 2 O 3 layer, which is acting as a substrate, and the other one consisting of NPs grown on the a-Al 2 O 3 surface. The high kinetic energy of a significant fraction of the Au species present in the plasma and the high fluxes ͑1016 -10 18 at cm −2 s −1 ͒ at the substrate plays an essential role in the nucleation and growth of the NPs. The competition between surface growth and sputtering at high fluence induces a self-regulation of the NP dimensions that narrows the size distributions.

Gold coating of micromechanical DNA biosensors by pulsed laser deposition

“…24 For the characteristic kinetic energies applicable to these experiments (which have been reported to be !3.0 eV in similar experimental conditions), 14 the preferential orientation of the crystallites is a manifestation of a minimum in the configuration energy, as (111) surfaces have the closest packing in the face centered cubic structure adopted by gold.…”

“…These differences can be explained in relation to the nucleation processes of the laser ablated species that take place on the substrate. In fact, it has been proposed 14,28,29 that defects created during layer growth by the high energetic plasma species reaching the substrate are responsible of the nucleation process. At the initial state of deposition, the dominating island-like growth results in small coverage of the surface area by clusters.…”

“…Self-sputtered processes are also thought to be responsible of the evolution of the nanoparticle size. 14 The presence of overimposed aggregates in the case of gold layers fabricated with a larger number of pulses (!12 000) can be explained by taking into account in this case the ejection mechanism. This is dominated by explosive boiling of the target material, 10-13 a phenomenon which is described as an explosive relaxation of the laser induced melt into a coexistent mixture of liquid droplets and vapor.…”

“…[8][9][10][11][12][13] This technique also offers the capability for producing epitaxial growth, and it has extensively been applied to produce metal nanoparticles. 14 Mechanical biosensors are based on the principle that molecular recognition on the surface of a bio-functionalized micromechanical system (e.g., a cantilever) can result in a bending (deflection) of a few nanometers. The origin of the nanomechanical response is the change of the surface stress due to electrostatic, van der Waals, and steric intermolecular interactions on the cantilever surface.…”

Determination of Morphological Parameters of Supported Gold Nanoparticles: Comparison of AFM Combined with Optical Spectroscopy and Theoretical Modeling versus TEM

“…Different techniques are employed to characterize the particle morphology [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39].…”