Transition from thin gold layers to nano‐islands on TCO for catalyzing the growth of one‐dimensional nanostructures

Abstract

International audienceThe formation of gold islands on a transparent conductive oxide by annealing a thin evaporated layer is studied by SEM. The droplets of metal formed this way may catalyze the growth of nanowires or nanotubes to be used in optoelectronic devices. The effect of the initial thickness (between 1 nm and 4 nm) and the annealing temperature (between 70 °C and 650 °C) is investigated. A qualitative description of the evolution is given and quantitative data are obtained by automated image analysis. Number density, area and effective diameter of the aggregates depend heavily on the initial thickness but very slightly on the annealing temperature. Three phenomena are considered to explain the evolution: interfacial stress due to mismatch in the linear expansion coefficient, Ostwald ripening and kinetic aggregation. By comparing the experimental size distributions to the theoretical ones, the relevance of the last two is discussed. As an application, the gold catalyzed CVD growth of silicon nanowires on zinc oxide is demonstrated

Solid-State Limited Nucleation of NiSi/SiC Core-Shell Nanowires by Hot-Wire Chemical Vapor Deposition

“…Figure 8 illustrates the schematic diagram of the proposed growth mechanisms of the NiSi nanoparticle and NiSi/SiC core-shell nanowires prepared by HWCVD. In the initial stage of the process, the Ni nanoparticles were formed as a result of the hydrogen plasma treatment at high substrate temperature conditions that similar to the works reported by Alet et al [ 36 ] and Colli et al [ 37 ]. The hydrogen plasma treatment plays an essential role in activating the catalyst metallic nanoparticles [ 24 , 38 ].…”

Tunable Localized Plasmon Transducers Prepared by Thermal Dewetting of Percolated Evaporated Gold Films

“…Studies concerning formation of island structure upon annealing of metal films of thicknesses in the vicinity of the percolation threshold are scarce compared to the large number of works devoted to annealing of island films or thick, fully percolated films. ,− Formation of well-defined island structures during annealing of near- and just-percolated Au films with nominal thicknesses of 7.5–15 nm was observed for Au films evaporated on mica, quartz, as well as bare and silanized glass. Island films were obtained by annealing at 435–500 °C of just-percolated Au films on ITO. , Annealing of just-percolated Ag and Cu films was also reported. , Just-percolated Ag films, 14–16 nm (nominal thickness), transformed to island films upon annealing. , The absence of a SP peak in as-deposited, 16 nm films suggested a percolated structure, which was transformed to islands after annealing at 600 K . Annealing of near-percolated, 14 nm Ag films at 120–350 °C resulted in a blue shift of the SP band, from 700 to 450 nm, allowing tuning in a relatively large wavelength window …”

“…Island films were obtained by annealing at 435À500 °C of just-percolated Au films on ITO. 39,53 Annealing of just-percolated Ag and Cu films was also reported. 54,55 Just-percolated Ag films, 14À16 nm (nominal thickness), transformed to island films upon annealing.…”

In situ generation of indium catalysts to grow crystalline silicon nanowires at low temperature on ITO

“…Yet few attempts have been reported. 13 One possible reason is the lack of stability of these substrates at high temperature. In particular, ITO is known to be superficially reduced upon exposure to SiH 4 or H 2 plasmas above 200 C. 14 In this communication, we propose to turn this sensitivity into an advantage to produce indium catalyst droplets in situ, and to grow SiNW by PECVD directly on ITO.…”