Low-Temperature Fabrication of Zinc Oxide Micropatterns Using Selective Electroless Deposition

Abstract

Zinc oxide ͑ZnO͒ micropatterns were synthesized site-selectively on photocatalytically activated regions of TiO 2 in an aqueous solution of zinc nitrate and dimethylamine-borane at 55°C by an electroless deposition process. The as-deposited ZnO micropatterns showed a polycrystalline wurtzite structure with a thickness of approximately 0.1 m. The ZnO micropatterns emitted ultraviolet light at 380 nm due to the recombination of bound excitons and broad visible-light luminescence ͑500-800 nm͒. Since the first report of ultraviolet by lazer from zinc oxide ͑ZnO͒, 1,2 substantial effort has been devoted to the development of synthetic methodologies for ZnO films. Among the various techniques described in the literature, evaporation and condensation processes are favored for their simplicity and high-quality products, but these gas-phase approaches generally require economically prohibitive temperatures of 800-900°C.3,4 Despite recent metallorganic chemical vapor deposition ͑MOCVD͒ schemes that reduced the deposition temperature to 450°C by using organometallic zinc precursors, 5 the commercial potential of gas-phase grown ZnO films remains constrained by the size and cost of the vapor deposition systems. Thus, a low-temperature, large-scale, and versatile synthetic process is needed before ZnO can have realistic applications in solar energy conversion, 6 light emission, 7 and other promising areas. [8][9][10] Solution approaches to ZnO films are appealing because of their low growth temperatures and good potential for scale-up. Because of this, Izaki et al. developed an electroless deposition ͑ELD͒ method for polycrystalline particulate ZnO films that is based on the reduction of nitrate ions and that uses dimethylamine borane ͑DMAB͒.11,12 By immersing substrates in an aqueous solution maintained at ϳ60°C, crystalline ZnO particulate films were obtained on the Pd catalyst particles attached to the substrates. However, in spite of the importance of the solution approaches to the fabrication of ZnO films, the chemical deposition mechanism of the ZnO film from aqueous solution is controversial, and several mechanisms have been proposed. Izaki et al. explained that the reduction reaction of the nitrate ion plays an important role in ZnO formation from the solution and is driven by the oxidation reaction of DMAB contained in the solution.11,12 It was also proposed that the deposition mechanism of the ZnO film originates from precipitation of Zn͑OH͒ 2 by the reduction of oxygen, 13,14 and participation of superoxide radicals by the reduction of oxygen. 15Selective ELD has recently become very promising for micro-/ nanostructuring a wide range of materials; that is, a method in which metal is electrolessly plated up from a predetermined pattern. In particular, it is proving increasingly useful in semiconductor and packaging technologies. A major requirement prior to performing selective ELD is the catalytic Pd seed ͑the placement and activation of the seed on the surface͒ and its selectivity: the seed must be confined to sp...

Recent progress in the electrochemical deposition of ZnO nanowires: synthesis approaches and applications

“…Although other chemical reducing agents can be used for the process, most published works report the use of DMAB. Likewise, the parameters in Table 2 are based on the use of DMAB, because stronger reducing agents could suggest alternative conclusions 6,124,127,[130][131][132][133][134][135][136][137][138][139][140][141] .…”

“…Bath temperature -Longitudinal growth-that is, (002) preferred orientation growth-as well as crystallinity increases as the temperature of deposition rises 139 . Texturation with the c-axis perpendicular to the substrate's surface is promoted at temperatures exceeding 55 °C 140 .…”

Morphologies of Sol–Gel Derived Thin Films of ZnO Using Different Precursor Materials and their Nanostructures

“…Zinc nitrate is also used for the synthesis of ZnO nanoparticles [ 8 ]. Micropatterns of ZnO have been synthesized [ 9 ] on photocatalytically activated regions of TiO 2 in an aqueous solution of zinc nitrate and dimethylamine-borane by an electroless deposition process. The as-deposited ZnO micropatterns showed a polycrystalline wurtzite structure.…”

Selective Electroless Deposition Using Photoinduced Oxidation of Sn(II) Compounds on Surface-Modified Polyimide Layers

“…Polyimide metallization is increasingly required in many applications (3)(4)(5)(6). Various methods have been developed for this purpose, and among them, selective electroless deposition (ELD) has emerged as an appealing patterning technique in which the metal is electrolessly plated onto a pre-established pattern (7)(8)(9)(10). Selective ELD requires the selective placement and activation of the catalytic Pd seed on the surface: the seed must be confined to specified regions of the substrate and be completely absent from other regions.…”