Looking Outside the Square: The Growth, Structure, and Resilient Two-Dimensional Surface Electron Gas of Square SnO Nanotubes.

Nanotechnology has delivered an amazing range of new materials such as nanowires, tubes, ribbons, belts, cages, flowers, and sheets. However, these are usually circular, cylindrical, or hexagonal in nature, while nanostructures with square geometries are comparatively rare. Here, a highly scalable method is reported for producing vertically aligned Sb-doped SnO nanotubes with perfectly-square geometries on Au nanoparticle covered m-plane sapphire using mist chemical vapor deposition.

Wavelength Selective Solar Cells Using Triple Cation Perovskite.

Perovskite materials offer high-efficiency low-cost solar cells and applications versatility. We report on cesium-based hybrid perovskite solar cells with wavelength-selective properties ranging from 500 nm (UV-VIS) to 800 nm (IR). The band gap tuning was achieved through composition changes of mainly lead(II) iodide PbI and lead(II) bromide PbBr The optical spectra of the developed materials were studied, including the photoluminescence (PL), optical transparency, X-ray diffraction and external quantum efficiency for samples prepared under different compositions.

Electroreduction of Aryldiazonium Ion at the Polar and Non-Polar Faces of ZnO: Characterisation of the Grafted Films and Their Influence on Near-Surface Band Bending.

ZnO is a strong candidate for transparent electronic devices due to its wide band gap and earth-abundance, yet its practical use is limited by its surface metallicity arising from a surface electron accumulation layer (SEAL). The SEAL forms by hydroxylation of the surface under normal atmospheric conditions, and is present at all crystal faces of ZnO, although with differing hydroxyl structures. Multilayer aryl films grafted from aryldiazonium salts have previously been shown to decrease the downward bending at O-polar ZnO thin films, with Zn-O-C bonds anchoring the aryl films to the substrate.

The effect of covalently bonded aryl layers on the band bending and electron density of SnO surfaces probed by synchrotron X-ray photoelectron spectroscopy.

Tin(iv) dioxide (SnO) is a technologically important transparent conducting oxide with high chemical stability. In air, the SnO surface is terminated with hydroxyl groups which cause the electronic bands to bend downward at the surface capturing a two-dimensional surface electron accumulation layer (SEAL). The SEAL promotes adsorption at the surface, giving environmentally-sensitive electronic properties; this sensitivity is a barrier to some potential applications of the material.

Alloy-Free Band Gap Tuning across the Visible Spectrum.

We present evidence, from theory and experiment, that ZnSnN_{2} and MgSnN_{2} can be used to match the band gap of InGaN without alloying-by exploiting cation disorder in a controlled fashion. We base this on the determination of S, the long-range order parameter of the cation sublattice, for a series of epitaxial thin films of ZnSnN_{2} and MgSnN_{2} using three different techniques: x-ray diffraction, Raman spectroscopy, and in situ electron diffraction. We observe a linear relationship between S^{2} and the optical band gap of both ZnSnN_{2} (1.

Tuning the Band Bending and Controlling the Surface Reactivity at Polar and Nonpolar Surfaces of ZnO through Phosphonic Acid Binding.

ZnO is a prime candidate for future use in transparent electronics; however, development of practical materials requires attention to factors including control of its unusual surface band bending and surface reactivity. In this work, we have modified the O-polar (0001̅), Zn-polar (0001), and m-plane (101̅0) surfaces of ZnO with phosphonic acid (PA) derivatives and measured the effect on the surface band bending and surface sensitivity to atmospheric oxygen. Core level and valence band synchrotron X-ray photoemission spectroscopy was used to measure the surface band bending introduced by PA modifiers with substituents of opposite polarity dipole moment: octadecylphosphonic acid (ODPA) and 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctylphosphonic acid (FOPA).

Persistent spectral hole burning due to deuteron tunneling in SrF(2):Pr(3+):D(-).

We report the observation of persistent spectral hole burning due to a mechanism that is new to inorganic materials, i.e., light-induced deuteron (or proton) tunneling.

Reversible polarized bleaching in hydrogenated rare-earth-doped fluorites.

By using site-selective laser spectroscopy, several sites in hydrogenated and deuterated rare-earth-doped fluorite crystals have been found to exhibit reversible bleaching. The site orientations can be switched between orthogonal directions by corresponding changes in the laser polarization. Such effects are a form of photochemical hole burning and are attributed to laser-induced migration of H(-) or D(-) ions between equivalent interstitial positions adjacent to the rare-earth ion.

Titration of phytic acid.

Titrimetric assays for phytic acid by titration with iron(III) or thorium are described. Stannous chloride interferes in both systems, causing negative errors directly proportional to the amount of stannous chloride. The thorium:phytate ratio in the complex formed is 2:1, which is interpreted as resulting from the possession of two chelating centres by phytic acid.