Interpretation of X-ray Powder Diffraction Patterns . By H. Lipson and H. Steeple. Pp. viii + 335 + 3 plates. (Mac-millan: London; St Martins Press: New York, May 1970.) £4.

X-Ray Diffraction

Influence of composition on optical and dispersion parameters of thermally evaporated non-crystalline Cd50S50−xSex thin films

Neural stimulation with high spatial and temporal precision is desirable both for studying the real-time dynamics of neural networks and for prospective clinical treatment of neurological diseases. Optical stimulation of genetically targeted neurons expressing the light sensitive channel protein Channelrhodopsin (ChR2) has recently been reported as a means for millisecond temporal control of neuronal spiking activities with cell-type selectivity. This offers the prospect of enabling local delivery of optical stimulation and the simultaneous monitoring of the neural activity by electrophysiological means, both in the vicinity of and distant to the stimulation site. We report here a novel dual-modality hybrid device, which consists of a tapered coaxial optical waveguide (‘optrode’) integrated into a 100 element intra-cortical multi-electrode recording array. We first demonstrate the dual optical delivery and electrical recording capability of the single optrode in in vitro preparations of mouse retina, photo-stimulating the native retinal photoreceptors while recording light-responsive activities from ganglion cells. The dual-modality array device was then used in ChR2 transfected mouse brain slices. Specifically, epileptiform events were reliably optically triggered by the optrode and their spatiotemporal patterns were simultaneously recorded by the multi-electrode array.

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Integrated device for optical stimulation and spatiotemporal electrical recording of neural activity in light-sensitized brain tissue

Enhanced the photocatalytic activity of Ni-doped ZnO thin films: Morphological, optical and XPS analysis

Synthesis and characterization of zinc oxide thin films for optoelectronic applications

Effect of Ag photo-doping on structural, optical and phase change properties of GeTe chalcogenide films

The measurements and analysis of optical transmission and far-infrared (IR) reflectivity spectra of thermally evaporated Sb2Se3:Sn films are reported. The refractive index and film thickness have been determined from the upper and lower envelopes of the transmission spectra (Swanepoel's standard envelope method), measured at normal incidence, in the spectral range from 800 to 2500 nm. Values of the refractive index fit well to Cauchy's dispersion relation. The optical gap decreases with an increase in the Sn content, while a maximum in the tailing parameter and Urbach's energy occurs with only a small amount (∼1 at %) of this additive. Characteristic vibrational bands for SbSe3 structural units are revealed in the far-IR spectrum with no additional ones arising from the Sn additive. The Kramers–Kronig analysis has been used to calculate the dielectric constants and hence the longitudinal optic and transverse optic splitting for various compositions. The inclusion of Sn as a charged entity along with the C...

Optical properties of amorphous Sb2Se3:Sn films

This paper reports the spectroscopic studies on the thermally evaporated SnxSb20Se80 − x (2 ≤ x ≤ 8) films. Optical gap and band tailing parameter decreases except for x = 8, where it increases. The red shift in peak reflectivity spectrum in the interband transition region (200–800 nm) has been observed. The position and shape of the reflectivity bands (80–378 cm− 1) indicate the change in the local structure of the films. The Kramer–Kronig transformations have been used to evaluate the dielectric constants from the far-infrared reflectivity spectrum. Splitting of the longitudinal optic and transverse optic mode characterizes the partial ionic character for Sn–Sb–Se system. The relationship between the optical properties and structure has been revealed.

Effect of Sn addition on the optical gap and far-infrared reflectivity spectra of amorphous Sb–Se films

Normal, helical and zigzag deposited Ni films were produced by letting a vapour stream of source material impinge on Corning 1737 glass substrates at oblique incidence while rotating the substrate during deposition. Films produced by glancing angle deposition (GLAD) technique while rotating the substrate. The microstructures of these Ni films were studied using X-ray diffractometry technique. The X-ray diffraction (XRD) patterns depicted 100% and 42% relative intensity (RI) peaks identified for normal and helical deposited Ni films but none for the zigzag deposited Ni film. Higher degree of crystallinity of Ni was demonstrated by the helical thin film sample having 200 nm thickness (sample Ni40) compared to the normal thin film which had only the 100% RI peak defined. Should an application therefore require Ni thin films of high crystallinity, it would be the film prepared with helical microstructure of 200 nm thickness that will be employed. @JASEM

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Understanding Nickel Thin Film crystallization using X-Ray Diffractometry

Effect of Pb substitution on the amorphous-crystalline transformation temperature, optical band gap and crystalline structure of Ge 2 Sb 2 Te 5 has been studied. In Pb:GeSbTe chalcogenide films prepared by thermal evaporation, an amorphous to crystallization transition is observed at 124, 129, 136 and 138 °C in Pb 0 Ge 20 Sb 24 Te 56 , Pb 1.6 Ge 19 Sb 26 Te 54 , Pb 3 Ge 17 Sb 28 Te 53 and Pb 5 Ge 12 Sb 28 Te 55 respectively. XRD investigations of annealed samples reveal that Pb substitution retains NaCl type crystalline structure of GST but expands the lattice due to large atomic radii. The increase in amorphous-crystalline transformation temperature is followed with the increase in phase segregation. The optical gap shows marginal variations with composition.

T.S. Sathiaraj

Papers

Effect of Ag photo-doping on structural, optical and phase change properties of GeTe chalcogenide films

Optical properties of amorphous Sb2Se3:Sn films

Effect of Sn addition on the optical gap and far-infrared reflectivity spectra of amorphous Sb–Se films

Understanding Nickel Thin Film crystallization using X-Ray Diffractometry

Phase segregation in Pb:GeSbTe chalcogenide system