Bi32Cd3P10O76: a new congruently melting nonlinear optical crystal with a large SHG response and a wide transparent region

Large size single crystal Bi32Cd3P10O76 with a large SHG response (4 × KDP) and a wide transmission range covering 0.36–4.9 μm.

Growth and Structural Characterization of Doped Polymorphic Crystalline MgPc as an Organic Semiconductor

The doping and crystallization of the molecular semiconductor formed from the magnesium phthalocyanine (MgPc) and 1-(4-Methoxyphenyl)-2,2,6,6-tetramethyl-5-phenylhepta-3,4-dienedioic (MTPDA) acid was carried out in this work. The crystals obtained were characterized by using transmission electronic microscopy (TEM), Raman spectroscopy, and X-Ray diffraction (XRD), to later evaluate their optical behavior. Raman, IR, and UV–Vis results indicate that the MgPc has been doped with the MTPDA. A uniform material layer with particles is observed as a result of a two-stage process, nucleation and growth. The polycrystalline films are constituted by a mixture of α and β phases with crystalline sizes of ~7 nm, 14 nm, and 20 nm average sizes. The films exhibit a preferred orientation along the [001]. The MTPDA doping does not have an important effect on the molecule planar distances indicating that the MTPDA molecule is among the equivalent MgPc plane direction. A transparent region with a minimum at 483 nm is observed, also a B-band at 337 nm and a Q-band transition with a high-energy peak around 639 nm, and a low energy peak around 691 nm.

SPATIAL STRUCTURE OF AZIMUTHALLY SMALL-SCALE MHD WAVES IN ONE-DIMENSIONALLY INHOMOGENEOUS FINITE PRESSURE PLASMA WITH CURVED FIELD LINES

We have studied propagation of hydromagnetic (MHD) waves in one-dimensionally inhomogeneous finite pressure plasma with curved field lines. Magnetic surfaces are considered to be concentric cylinders, where the cylinder’s radius models the radial coordinate in Earth’s magnetosphere. The waves are supposed to be azimuthally small-scale. In this approximation there are only two MHD modes — Alfvén and slow magnetosonic (SMS). We have derived an ordinary differential equation for the spatial structure of the wave field in this model. We have examined the character of the singularity on the surface of Alfvén and SMS resonances and the influence of field line curvature on them. We have determined wave transparent regions. The SMS transparent region was found to essentially broaden as compared to the straight field line case. The very existence of the Alfvén transparent region is caused by the field line curvature and finite plasma pressure; otherwise, the wave structure is represented by a localized resonance.

SPATIAL STRUCTURE OF AZIMUTHALLY SMALL-SCALE MHD WAVES IN ONE-DIMENSIONALLY INHOMOGENEOUS FINITE PRESSURE PLASMA WITH CURVED FIELD LINES

We have studied propagation of hydromagnetic (MHD) waves in one-dimensionally inhomogeneous finite pressure plasma with curved field lines. Magnetic surfaces are considered to be concentric cylinders, where the cylinder’s radius models the radial coordinate in Earth’s magnetosphere. The waves are supposed to be azimuthally small-scale. In this approximation there are only two MHD modes — Alfvén and slow magnetosonic (SMS). We have derived an ordinary differential equation for the spatial structure of the wave field in this model. We have examined the character of the singularity on the surface of Alfvén and SMS resonances and the influence of field line curvature on them. We have determined wave transparent regions. The SMS transparent region was found to essentially broaden as compared to the straight field line case. The very existence of the Alfvén transparent region is caused by the field line curvature and finite plasma pressure; otherwise, the wave structure is represented by a localized resonance.

Transparency in the eye region of an ostracod carapace ( Macrocypridina castanea , Myodocopida)

Many myodocopid ostracods are unusual in that they have well-developed compound eyes yet must view their environment through a shell. The cypridinid Macrocypridina castanea is relatively large among ostracods (about 5–10 mm) and is a pelagic predator. This species possess highly pigmented shells with a transparent region lying just above the eye. Here we examine the ultrastructure and transparency of this window using electron microscopy, serial-block face scanning electron microscopy and X-ray diffraction analysis and optical modelling. An internal, laminar stack was identified within the window region of the shell that formed a more regular half-wave reflector than in non-window regions, and where the distance between molecules in the chitin–protein fibrils decreases as compared to the non-window area. This results in excellent transmission properties—at around 99% transmission—for wavelengths between 350 and 630 nm due to its half-wave reflector organization. Therefore, blue light, common in the mid and deep sea, where this species inhabits, would be near-optimally transmitted as a consequence of the sub-micrometre structuring of the shell, thus optimizing the ostracod's vision. Further, pore canals were identified in the shell that may secrete substances to prevent microbial growth, and subsequently maintain transparency, on the shell surface. This article is part of the theme issue ‘Bioinspired materials and surfaces for green science and technology’.

Focused Ion Beam Preparation of Specimens for Micro-Electro-Mechanical System-based Transmission Electron Microscopy Heating Experiments

Micro-electro-mechanical systems (MEMS)-based heating holders offer exceptional control of temperature and heating/cooling rates for transmission electron microscopy experiments. The use of such devices is relatively straightforward for nano-particulate samples, but the preparation of specimens from bulk samples by focused ion beam (FIB) milling presents significant challenges. These include: poor mechanical integrity and site selectivity of the specimen, ion beam damage to the specimen and/or MEMS device during thinning, and difficulties in transferring the specimen onto the MEMS device. Here, we describe a novel FIB protocol for the preparation and transfer of specimens from bulk samples, which involves a specimen geometry that provides mechanical support to the electron-transparent region, while maximizing the area of that region and the contact area with the heater plate on the MEMS chip. The method utilizes an inclined stage block that minimizes exposure of the chip to the ion beam during milling. This block also allows for accurate and gentle placement of the FIB-cut specimen onto the chip by using simultaneous electron and ion beam imaging during transfer. Preliminary data from Si and Ag on Si samples are presented to demonstrate the quality of the specimens that can be obtained and their stability during in situ heating experiments.

EFFECT OF ANNEALING TEMPERATURE ON STRUCTURAL AND OPTICAL PARAMETERS OF SOL–GEL ROUTED MOLYBDENUM OXIDE THIN FILM

The influence of annealing temperature on structural and optical properties of sol–gel routed spin-coated molybdenum tri oxide ( MoO 3) thin films are studied. The higher annealing temperatures improve the crystalline nature of the film. The X-ray diffraction (XRD) study reveals the formation of α-orthorhombic phase at higher annealing temperature and amorphous nature at lower annealing temperature. The optical bandgap of molybdenum tri oxide ( MoO 3) film is found to be 3.3–3.8 eV, and the refractive index of the film is found to be 2.2–2.9. The dispersion curve of the refractive index shows that an abnormal dispersion in the absorption region and normal dispersion in the transparent region are observed. The optical polarizability, optical conductivity, dielectric constant, volume and surface energy loss parameters are evaluated.

Enhancement in crystalline perfection and optical properties of benzophenone single crystals: the remarkable effect of a liquid crystal

The remarkable enhancement of the crystalline perfection of benzophenone (BP) crystals induced by liquid crystal (LC) doping has been investigated, and has in turn led to better optical properties. High-resolution X-ray diffractometry demonstrates that the structural grain boundaries present in pure crystals can be eliminated when the crystal is grown with LC doping. Thus, the high alignment capability of LCs has for the first time been utilized to enhance the quality of BP bulk single crystals. The LC-doped crystal exhibits higher optical transparency over its entire transparent region. The optical polarizing behaviour of the doped BP crystal is also improved.