Fabrication Of Indium Oxide Nanostructures And Investigation Of Correspoding Property

In this paper, we demonstrate large-scale fabrication of diverse In₂O₃ nanostructures, including ertical nanowire arrays, vertical nanotube arrays, small-diameter square nanotubes and nanosheet chains, etc., via thermal chemical-vapor-deposition process, benefiting from substrate-inducement, self-catalyzed VLS growth and self-assemble property. These aligned structures are directly integrated on InP substrates, which could facilitate subsequent nanoscale device performance, without using any adhesive to seal them for application demands. Equally important, remarkable photoinduced wettability conversion between superhydrophobicity and high-hydrophilicity has been firstly observed on arrayed In₂O₃ nanostructures. This reversible effect is ascribed to the photogenerated surface defective sites and the special nanostructures. Such reversible switching surfaces will greatly widen the applications of In₂O₃ films.At First, we give a brief introduction to the concept, history and application field of nanotechnology. Then we present some conventional synthesis approaches for nanostructures and their basic principles. According to the growth environment, they can be mainly divided into two categories: vapor phase method and liquid (solution) phase method. After this, main apparatus used for characterizing nanostructured materials are introduced, such as transmission electron microscope, scanning electron microscope, X-ray diffraction system, atomic force microscope, and photoluminescence (PL) spectra.Second, we review the basic information and theory of electrochemical anodizing etching. Based on normal two-step anodization knowledge, we present the preparation of well-aligned nano-porous InP and nano-porous alumina membranes. The membranes'morphology, size and other structural information are important factors in the subsequent CVD growth process.Third, we introduce the fabrication and characterization of versatile In₂O₃ nanostructures via thermal CVD process and discuss about the influence of experimental details. If the as-prepared uniform nano-porous InP used as substrate and source, was annealed with reaction gas oxygen in a certain temperature and time, vertical In₂O₃ nanowire arrays would be obtained, taking advantage of substrate geometry-inducement and self-decomposition of porous InP. We also found that this process profited from self-catalyzed property of liquid indium. Hence, we supposed to obtain other morphology by artificially altering the experiment conditions, the results are showing: by adding a pre-annealing step (liquid indium will self-assembly shape large circles on the top of porous structures), we achieved vertical nanotube arrays; by adding extra indium source and improving the annealing temperature (force to occur simultaneous reaction: decomposition of InP and nucleation of In₂O₃), we achieved cloned square nanotubes; by adding extra source and changing substrate morphology (separated nanodot InP substrate), we achieved ultralong In₂O₃ nanowire alignment; by adding extra source and using as-prepared vertical In₂O₃ nanowire arrays as substrate, we achieved In₂O₃ nanosheet chains; by changing substrate to porous alumina membranes and carrying out a two-step method of"first evaporation and second deposition"process, we achieve porous In₂O₃ membranes, etc. All in all, substrate inducement, VLS self-catalyzed growth and self-assembly property are the crucial keys dominating the results in all the experiment.At last, we investigate the reversible switching of wettability between superhydrophobicity to superhydrophilicity of arrayed In₂O₃ nanostructures, which is governablly induced by ultraviolate illumination and darkness storage. We suggest that the photoinduced superhydrophilic phenomenon is due to photogenerated surface defects and special nanostructures. However, the surface defects are not stable by darkness storage in air for a certain time. They will generally disappear by reaction with oxygen. So, the nanostructure induced superhydrophobicity is returned again.