Dynamics of laser induced metal nanoparticle and pattern formation

Abstract

Discontinuous metal films are converted into either almost round, isolated, and randomly distributed nanoparticles (NPs) or fringed patterns of alternate non transformed film and NPs by exposure to single pulses (20 ns pulse duration and 193 nm wavelength) of homogeneous or modulated laser beam intensity. The dynamics of NPs and pattern formation is studied by measuring in real time the transmission and reflectivity of the sample upon homogeneous beam exposure and the intensity of the diffraction orders 0 and 1 in transmission configuration upon modulated beam exposure. The results show that laser irradiation induces melting of the metal either completely or at regions around intensity maxima sites for homogeneous and modulated beam exposure, respectively, within 10 ns. The aggregation and/or coalescence of the initially irregular metal nanostructures is triggered upon melting and continues after solidification (estimated to occur at 80 ns) for more than 1 ls. The present results demonstrate that real time transmission rather than reflectivity measurements is a valuable and easy-to-use tool for following the dynamics of NPs and pattern formation. They provide insights on the heat-driven processes occurring both in liquid and solid phases and allow controlling in-situ the process through the fluence. They also evidence that there is negligible lateral heat release in discontinuous films upon laser irradiation. V C 2015 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4908251]Metal nanoparticles (NPs) either randomly distributed or periodically organised have a high potential for several applications including camouflage, sensors, photovoltaic or optical devices, and tissue engineering scaffolds. 1,2 Most of the applications relate to their unique optical response that is dominated by the surface plasmon resonance (SPR). 3 Heating of metal thin films is a method used since very long to produce them because metal films on dielectric substrates are thermodynamically unstable and tend to dewet for reducing their surface to volume ratio and thus the free energy of the system. [4][5][6] Laser techniques offer a faster means not only for producing NPs on a surface by a heat driven process but also for producing periodic structures, thus representing an alternative route to the costly lithographic methods such as electron beam writing, 3 particularly for those applications in which large-scale and low-cost manufacturing is essential. Irradiation with homogeneous or Gaussian converts metal films into nanoislands, beads or NPs and even self-organised structures with well-defined length scales. 7-11 Irradiation with modulated beams such as those produced by beam interference produces structures with controlled motives and periods in large areas (>mm 2 ). 12-16 These earlier works aim either to the understanding of the length scales of the dewetting and/or mass flow mechanisms or the fabrication of nanostructures. There is only a very recent work studying the dewetting process in real time upon Gaussian ns laser pulses 11 by ...

Dewetting dynamics of nickel thin film on alpha-quartz substrate: A molecular dynamics study

“…However, it is not straightforward to control the dewetting process since the dewetting is governed by the nonlinear dynamics related to the capillary effect, which results in various patterns of morphology even in the same condition. Therefore, instability of nanoscale liquid metals on the substrate is widely studied [7,12,13]. For example, collapse and breakup of the nanostructure due to the capillary effect is closely discussed on the basis of the Plateau-Rayleigh instability [11][12][13], which originally explains the breakup of the falling stream of fluid into smaller droplets with same volume [14,15].…”

“…For example, metal nanoparticles monodispersed on the substrate are widely used as a catalyst of the synthesis of vertically-aligned carbon nanotubes [1][2][3]. Since size and density of nanoparticles strongly affect quality and yield of products [3], there are many studies focusing on the pattern formation and self-organization of metal nanoparticles on the substrate via the dewetting [4][5][6][7]. Moreover, dewetting is proactively used to synthesize various nanomaterials such as graphene-nanoribbon [8,9], nanowire [10] and nanoparticle-array [11,12].…”

One‐Pot Hybrid SnO2/Poly(methyl methacrylate) Nanocomposite Formation through Pulsed Laser Irradiation

“…For this reason, this unconventional synthetic methodology has paved the way for the achievement of various hybrids by simply tuning the organic environments in which the inorganic fillers will grow. Nevertheless, reports dealing with the formation of NPs induced by laser light mainly refer to chalcogenide‐based semiconductor materials (CdS, ZnS), transition metals, and lately ZnO NPs . To date, SnO 2 in situ synthesis in a polymer matrix through irradiation has not been presented.…”

“…Recently,the in situ synthesis of NPs triggered by laser irradiation, rather than the aforementioned chemical approach, has gained much more attention compared with other nanocomposite synthetic methods, [2,22,23] due to its capability to form well-dispersed, size-controlled NPs in specific areaso ft he polymeric matrix, in whicht he precursors are previously dispersed. For this reason,t his unconventional synthetic methodology has paved the way fort he achievement of various hybridsb y simply tuning the organic environments in which the inorganic fillers will grow.N evertheless, reports dealing with the formation of NPs inducedb yl aser light mainly refer to chalcogenide-based semiconductor materials (CdS, ZnS), [24][25][26] transition metals, [27][28][29][30][31] andl ately ZnO NPs. [32] To date, SnO 2 in situ synthesis in ap olymer matrix through irradiation has not been presented.U Vl ight and electron beam irradiation techniques have only been employed to grow SnO 2 NPso nn on-polymeric substrates, such as graphene oxide sheets, [21,33] whereas it would be highly desirable to develop new strategies fort he in situ formation of SnO 2 NPs in solid polymericf ilms.…”

Large area compatible broadband superabsorber surfaces in the VIS-NIR spectrum utilizing metal-insulator-metal stack and plasmonic nanoparticles

“…A set of studies on PV devices are available utilizing random nanoparticles for enhanced plasmonic absorption for solar cells and photodiodes [3][4][5], while Wang et al propose an MIM stack carrying the burden of both absorption and photocurrent generation which would place harsh restrictions on device engineering to comply with desirable electrical and photonic characteristics [6]. There has been numerous efforts to attain random nanoparticles by laserinduced and heat-induced dewetting [7,8].…”