Self‐organization of silica nano‐particles induced by the ion beam

Abstract

We studied the self‐organization (SO) of small‐size (D = 90 nm), medium‐size (220 nm), and large‐size (450 nm) colloidal silica nanoparticles in Langmuir‐Blodgett layers induced by a focused Ga+ ion beam with energy of 30 keV. The ion irradiation induces SO into various types of clusters as the result of particle charging and heating, Coulomb repulsion and motion on the substrate surface, as well as of particle ‐ particle and particle ‐ substrate interaction. These processes show a great difference of the underlying dynamics and of the characteristics of SO pattern, depending on the particle size and on the ion fluence. The two dimensional (2D) pattern of the small‐size particles is transformed into “infinite” chain‐cluster, while the pattern of medium‐size particles is transformed into a number of short separated chain‐clusters. The pattern of large‐size particles is mostly unchanged, but shows particle melting and buckling, which at higher fluences passes into ion beam‐induced sputtering (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Ar+ ion irradiation-induced reorganization of colloidal silica nanoparticles in Langmuir–Blodgett monolayers

“…The physical parameters playing crucial role in such effects are ion energy, ion mass, particle size and shape, particle-particle distance and the initial self-organization of particles in the LB monolayer [5,6]. So far low mass ions like He + [11], medium mass ions like Ar + or Ga + [5,6], and heavy ions like Xe + [12,13], Xe 2+ [7,14] or Xe 4+ [15] have been used for the irradiation of various materials and study of the above mentioned phenomena.…”

“…At low and medium fluence this process depends on the charging of particles and relation between Coulomb and friction forces [5,6], proximity effects [7,8] and the swelling of the silicon substrate. At high fluence, discharging and thermal effects like 2D surface…”

Various Nanostructures on Macroscopically Large Areas Prepared by Tunable Ion-Swelling

“…[12] for 15 keV and 75 keV C + irradiated silica particles and in Ref. [24] for 30 keV Ga + irradiated LB films. For low energy ion irradiation the anisotropic transformation process does not occur, instead particle clustering and sintering takes place.…”

“…The process is quite complex and is affected by particle charging, heating, softening, particle-particle and particle-substrate adhesion forces, for details see Ref. [24]. The features of clustering and neck formation depend on the particle size and irradiation parameters (ion mass, ion fluence, ion flux, etc.).…”

“…Ions penetrating into the single crystalline Si substrate generate defects and cause mechanical stresses effecting surface swelling of which degree depends on the parameters of the irradiation: ion mass, ion energy, ion fluence, and substrate temperature. [21][22][23][24] In the images it can be observed that the contrast of masking is high according to SRIM calculations represented in Figure 1(a), surface swelling occurs only in between the nanospheres and the gradient is high between the unmasked and masked regions, i.e., underneath the nanoparticles. Figure 2 also shows that the structure height (swelling) can be tuned by the applied ion fluence.…”