Bottom-up growth of fully transparent contact layers of indium tin oxide nanowires for light-emitting devices

Thin layers of indium tin oxide are widely used as transparent coatings and electrodes in solar energy cells, flat-panel displays, antireflection coatings, radiation protection and lithium-ion battery materials, because they have the characteristics of low resistivity, strong absorption at ultraviolet wavelengths, high transmission in the visible, high reflectivity in the far-infrared and strong attenuation in the microwave region. However, there is often a trade-off between electrical conductivity and transparency at visible wavelengths for indium tin oxide and other transparent conducting oxides. Here, we report the growth of layers of indium tin oxide nanowires that show optimum electronic and photonic properties and demonstrate their use as fully transparent top contacts in the visible to near-infrared region for light-emitting devices.

In-situ examination of the selective etching of an alkanethiol monolayer covered Au{111} surface

An examination of the selective etching mechanism of a 1-alkanethiol self-assembled monolayer (SAM) covered Au{111} surface using in-situ atomic force microscopy (AFM) and molecular resolution scanning tunnelling microscopy (STM) is presented. The monolayer self-assembles on a smooth Au{111} surface and typically contains nanoscale non-uniformities such as pinholes, domain boundaries and monatomic depressions. During etching in a ferri/ferrocyanide water-based etchant, selective and preferential etching occurs at SAM covered Au(111) terrace and step edges where a lower SAM packing density is observed, resulting in triangular islands being relieved. The triangular islands are commensurate with the Au(111) lattice with their long edges parallel to its [11-0] direction. Thus, SAM etching is selective and preferential attack is localized to defects and step edges at sites of high molecular density contrast.

Mechanism that dictates pore width and <111>a pore propagation in InP

We report a mechanism for pore growth and propagation based on a three-step charge transfer model. The study is supported by electron microscopy analysis of highly doped n-InP samples anodised in aqueous KOH. The model and experimental data are used to explain propagation of pores of characteristic diameter preferentially along the <111>A directions. We also show evidence for deviation of pore growth from the <111>A directions and explain why such deviations should occur. The model is self-consistent and predicts how carrier concentration affects the internal dimensions of the porous structures.

Dissociative adsorption of methane on the Cu and Zn doped (111) surface of CeO2

The development of economical heterogeneous catalysts for the activation of methane is a major challenge for the chemical industry. Screening potential candidates becomes more feasible using rational catalyst design to understand the activity of potential catalysts for CH4 activation. The focus of the present paper is the use of density functional theory to examine and elucidate the properties of doped CeO2. We dope with Cu and Zn transition metals having variable oxidation state (Cu), and a single oxidation state (Zn), and study the activation of methane. Zn is a divalent dopant and Cu can have a +1 or +2 oxidation state. Both Cu and Zn dopants have an oxidation state of +2 after incorporation into the CeO2 (111) surface; however a Hubbard +U correction (+U = 7) on the Cu 3d states is required to maintain this oxidation state when the surface interacts with adsorbed species. Dissociation of methane is found to occur locally at the dopant cations, and is thermodynamically and kinetically more favorable on Zn-doped CeO2 than Cu-doped CeO2. The origins of this lie with the Zn(II) dopant moving towards a square pyramidal geometry in the sub surface layer which facilitates the formation of two-coordinated surface oxygen atoms, that are more beneficial for methane activation on a reducible oxide surface. These findings can aid in rational experimental catalyst design for further exploration in methane activation processes.

Synthesis of indium nanoparticles at ambient temperature; simultaneous phase transfer and ripening

The synthesis of size-monodispersed indium nanoparticles via an innovative simultaneous phase transfer and ripening method is reported. The formation of nanoparticles occurs in a one-step process instead of well-known two-step phase transfer approaches. The synthesis involves the reduction of InCl3 with LiBH4 at ambient temperature and although the reduction occurs at room temperature, fine indium nanoparticles, with a mean diameter of 6.4 ± 0.4 nm, were obtained directly in non-polar n-dodecane. The direct synthesis of indium nanoparticles in n-dodecane facilitates their fast formation and enhances their size-monodispersity. In addition, the nanoparticles were highly stable for more than 2 months. The nanoparticles were characterised by dynamic light scattering (DLS), small angle X-ray scattering (SAXS), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and Fourier transform infrared (FT-IR) spectroscopy to determine their morphology, structure and phase purity.