Simultaneous Formation and Spatial Patterning of ZnO on ITO Surfaces by Local Laser-Induced Generation of Microbubbles in Aqueous Solutions of [Zn(NH₃)₄]²⁺

Abstract

We demonstrate the simultaneous formation and spatial patterning of ZnO nanocrystals on an indium-tin oxide (ITO) surface upon local heating using a laser (1064 nm) and subsequent formation of microbubbles. Laser irradiation of an ITO surface in aqueous [Zn(NH)] solution (1.0 × 10 M at pH 12.0) under an optical microscope produced ZnO nanocrystals, the presence of which was confirmed by X-ray diffraction analysis and Raman microspectroscopy. Scanning the focused laser beam over the ITO surface generated a spatial ZnO pattern (height: ∼60 nm, width: ∼1 μm) in the absence of a template or mask. The Marangoni convection generated in the vicinity of the microbubbles resulted in a rapid concentration/accumulation of [Zn(NH)] around the microbubbles, which led to the formation of ZnO at the solid-bubble-solution three-phase contact line around the bubbles and thus afforded ZnO nanocrystals on the ITO surface upon local heating with a laser.

Light-Guided Surface Plasmonic Bubble Movement via Contact Line De-Pinning by In-Situ Deposited Plasmonic Nanoparticle Heating

“…The merging process occurs at a time scale of less than 200 μs, which is due to the Ostwald ripening effect 40,41 . We believe that the laser-guided merging process of two surface bubbles can enable potential applications beyond the demonstrated ones such as micro-pattern writting [16][17][18] and micro-particle assembly 14,19 .…”

Laser Irradiation of Metal Oxide Films and Nanostructures: Applications and Advances

“…This technique is based on the utilization of long‐range forces such as the capillary force and surface tension or convection, to construct patterned structures via a self‐assembly approach at the nano/mesoscale level. Laser‐assisted patterning of a variety of materials, such as CdSe/ZnS quantum dots, polyoxometalates, glycine single crystals, carbon nanotubes, Al 2 O 3 NWs, and ZnO nanocrystals has been demonstrated . This fast and easily controllable patterning approach has potential for diverse applications in microelectronics, chemical/biomolecular systems, photonics, and energy‐conversion systems.…”

“…Haga and co‐workers demonstrated the simultaneous formation and spatial patterning of ZnO nanocrystals on ITO substrates in aqueous [Zn(NH 3 ) 4 ] 2+ solution based on the laser‐induced generation of microbubbles ( Figure a–d) . For this purpose, a CW laser (Nd:YAG, 1064 nm) was focused on the ITO surface through the objective lens of an optical microscope.…”

“…Furthermore, solvent evaporation from the bubble–substrate–solution three‐phase contact line accelerates the nucleation and growth of the MO at the interface. Finally, manipulation of the location of the bubble formation by laser scanning results in a spatial patterning of the material on the substrate (Figure e) . To induce the above‐discussed phenomenon, it is necessary to have a precursor solution with high absorbance in the chosen laser‐wavelength region and a substrate with low thermal conductivity for inducing local heating on its surface upon laser irradiation.…”

“…The large temperature gradients and high diffusion rates during laser processing lead to epitaxial growth rates that are orders of magnitude larger and effective heating times much shorter than that for conventional thermal treatment . Furthermore, the laser irradiation technique has been utilized for processing of complex nanostructures, such as site‐specific growth of nanowires (NWs) (e.g., ZnO, TiO 2 ) and nanorods (NRs) (e.g., Fe 2 O 3 , Ag/ZnO), spatial patterning of nanocrystals (e.g., ZnO) and NWs (e.g., Al 2 O 3 ), fabrication of nanosheets (e.g., Fe 2 O 3 ) and clustered nanostructures (e.g., Ag–ZnS@ZnO, Ag/WO 3− x ), production of oxide nanoparticles (NPs) by laser ablation in liquid (e.g., CuO, MnO x , Y 3 Fe 5 O 12 , Ag/TiO 2 , Y 2 O 3 :Eu 3+ , Gd 2 O 3 :Eu 3+ , Y 3 Al 5 O 12 :Ce 3+ (YAG:Ce), Fe@Fe 2 O 3 , or Fe 3 O 4 ), in situ formation of nanocomposites (e.g., Co 3 O 4 , MoO 2 , and Fe 3 O 4 particles embedded in graphene, ZnO particles embedded in poly(methyl methacrylate)), selective patterning of hybrid electrodes (e.g., Ni/NiO), direct scribing of fine structures (e.g., ITO), and direct writing of microdevices (e.g., TiO 2 , Cu/Cu 2 O).…”