Single crystal

About: Single crystal is a research topic. Over the lifetime, 59617 publications have been published within this topic receiving 870828 citations.

Excitonic structure and absorption coefficient measurements of ZnO single crystal epitaxial films deposited by pulsed laser deposition

Abstract: The optical properties of high quality single crystal epitaxial zinc oxide thin films grown by pulsed laser deposition on c-plane sapphire substrates were studied. It was found that annealing the films in oxygen dramatically improved the optical and electrical properties. The absorption coefficient, band gap, and exciton binding energies were determined by transmission measurements and photoluminescence. In both the annealed and the as-deposited films excitonic absorption features were observed at both room temperature and 77 K. In the annealed films the excitonic absorption peaks were substantially sharper and deep level photoluminescence was suppressed.

Properties of Fe single‐crystal films grown on (100)GaAs by molecular‐beam epitaxy

Abstract: Single‐crystal (100)Fe films 90–330 A thick have been grown on etch‐annealed (100)GaAs substrates by molecular‐beam‐epitaxy techniques. Ferromagnetic resonance data indicate that the two in‐plane 〈110〉 directions are inequivalent and, together with magnetometry data, show that the average film magnetization decreases as the thickness decreases. The inequivalence is attributed to the nature of the interface bonding at a (100) zinc‐blende surface. The decreased magnetization is attributed to the formation of Fe2As microclusters in the film due to As diffusion which is supported by Auger and electron diffraction studies. In general, the Fe films grown to date on etch‐annealed (100)GaAs substrates are significantly inferior to those grown on (110)GaAs.

Single-Crystal Structure of a Covalent Organic Framework

Abstract: The crystal structure of a new covalent organic framework, termed COF-320, is determined by single-crystal 3D electron diffraction using the rotation electron diffraction (RED) method for data collection. The COF crystals are prepared by an imine condensation of tetra-(4-anilyl)methane and 4,4′-biphenyldialdehyde in 1,4-dioxane at 120 °C to produce a highly porous 9-fold interwoven diamond net. COF-320 exhibits permanent porosity with a Langmuir surface area of 2400 m2/g and a methane total uptake of 15.0 wt % (176 cm3/cm3) at 25 °C and 80 bar. The successful determination of the structure of COF-320 directly from single-crystal samples is an important advance in the development of COF chemistry.

Deep-ultraviolet nonlinear optical crystals: Ba3P3O10X (X = Cl, Br).

Abstract: Deep-ultraviolet nonlinear optical (deep-UV NLO) crystals are of worldwide interest for the generation of coherent light with wavelength below 200 nm by the direct second-harmonic generation (SHG) output from solid-state lasers. The unprecedented deep-UV NLO phosphates representing their own structure types, Ba3P3O10Cl (BPOC), Ba3P3O10Br (BPOB), have been discovered, which display moderate powder SHG intensities in type I phase matchable behaviors with a short UV cutoff edge of 180 nm (measured by a single crystal, one of the shortest values among phosphates to date). Insightfully, the geometry and polarization of the C1-P3O105– building unit are affected by the crystal packing. DFT calculations and cutoff energy dependent SHG coefficient analyses reveal that the SHG origin is from the cooperation of asymmetric C1-P3O105– anion, Ba2+ cation, and Cl–/Br– anion.