Fabrication by means of x-ray lithography of two-dimensional GaAs/AlGaAs photonic crystals with an unconventional unit cell

2002 ◽  
Vol 13 (5) ◽  
pp. 644-652 ◽  
Author(s):  
F Romanato ◽  
L Businaro ◽  
E Di Fabrizio ◽  
A Passaseo ◽  
M De Vittorio ◽  
...  
Keyword(s):  
Photonic Crystals ◽  
Unit Cell ◽  
Two Dimensional ◽  
X Ray

scholarly journals The Diffraction Pattern Calculator(DPC) toolkit: a user-friendly approach to unit-cell lattice parameter identification of two-dimensional grazing-incidence wide-angle X-ray scattering data

2014 ◽  
Vol 47 (6) ◽  
pp. 2090-2099 ◽  
Author(s):  
Anna K. Hailey ◽  
Anna M. Hiszpanski ◽  
Detlef-M. Smilgies ◽  
Yueh-Lin Loo
Keyword(s):  
Crystal Structure ◽  
Grazing Incidence ◽  
Unit Cell ◽  
Lattice Parameters ◽  
Scattering Data ◽  
Wide Angle ◽  
Two Dimensional ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

TheDPCtoolkit is a simple-to-use computational tool that helps users identify the unit-cell lattice parameters of a crystal structure that are consistent with a set of two-dimensional grazing-incidence wide-angle X-ray scattering data. The input data requirements are minimal and easy to assemble from data sets collected with any position-sensitive detector, and the user is required to make as few initial assumptions about the crystal structure as possible. By selecting manual or automatic modes of operation, the user can either visually match the positions of the experimental and calculated reflections by individually tuning the unit-cell parameters or have the program perform this process for them. Examples that demonstrate the utility of this program include determining the lattice parameters of a polymorph of a fluorinated contorted hexabenzocoronene in a blind test and refining the lattice parameters of the thin-film phase of 5,11-bis(triethylsilylethynyl)anthradithiophene with the unit-cell dimensions of its bulk crystal structure being the initial inputs.

Fabrication of two-dimensional photonic structure of titanium dioxide with sub-micrometer resolution by deep x-ray lithography

2004 ◽  
Vol 820 ◽  
Author(s):  
Koichi Awazu ◽  
Makoto Fujimaki ◽  
Xiaomin Wang ◽  
Akihide Sai ◽  
Yoshimichi Ohki
Keyword(s):  
Refractive Index ◽  
Titanium Dioxide ◽  
Photonic Crystals ◽  
Band Gap ◽  
Photonic Band Gap ◽  
3D Structure ◽  
Two Dimensional ◽  
Nano Structure ◽  
X Ray ◽  
Photonic Band

AbstractTwo dimensional photonic crystals of titanium dioxide is expected to have many advantage compared with photonic crystals of semiconductors, e.g., silicon and GaAs. For example, low optical loss in the near infrared region used for optical communication, low thermal expansion, and its refractive index which is close to that for optical fiber are attractive advantages. However, it is difficult to create micro-nano structure in titanium dioxide because micro-fabrication technique for semiconductor is not available for titanium dioxide. As the first step we calculated photonic band gap of titanium dioxide rod-slab on SiO2. Also, band gap percent against thickness of the rod-slab was examined. Finally, we confirmed the most suitable structure of 2D photonic crystals. Deep x-ray lithography technique was employed for create a very deep and precise template of PMMA. Then, liquid-phase deposition was used to faithfully deposit a tightly packed layer of titanium oxide onto the template. Finally, the template is selectively removed to obtain a photonic nano-structure. We also calculate photonic band gap on the 3D-structure of TiO2. A template for the most appropriate structure was fabricated by the method proposed by Yablonovitch. By using of the same method, it was successful to obtain 3D structure of TiO2. Refractive index of obtained TiO2 followed by heating at 700°C was determined to 2.5 which is close to that for anatase phase.

A crystal structure of ultra-dispersed form of polytetrafluoroethylene based on X-ray powder diffraction data

2004 ◽  
Vol 19 (3) ◽  
pp. 219-224 ◽  
Author(s):  
V. M. Bouznik ◽  
S. D. Kirik ◽  
L. A. Solovyov ◽  
A. K. Tsvetnikov
Keyword(s):  
Powder Diffraction ◽  
Rietveld Method ◽  
Unit Cell ◽  
Two Dimensional ◽  
Powder Diffraction Data ◽  
X Ray Diffraction ◽  
Rotational Displacement ◽  
X Ray ◽  
Dimensional Unit ◽  
Disordered Atoms

An X-Ray powder diffraction study of ultra-dispersed polytetrafluoroethylene was carried out. As well as a regular polytetrafluoroethylene the ultra-dispersed form contents a high proportion of the crystalline phase. The X-ray diffraction pattern could be described with two-dimensional hexagonal unit cell [a=5.685(1) Å, symmetry group p6mm]. Structural modeling with a continuous electron density approach as well as with a discrete disordered atoms distribution was accomplished. The model was refined using the Rietveld method. The structure is characterized by a spiral arrangement of polymers (CF2-)n along the z-axis with complete mutual disordering by rotational displacement around z, as well as a partial molecular translation along the z-axis. Molecular disordering results in a systematic absence of reflections with 1≠0 and as a sequence in two-dimensional unit cell effect. The presence of complete rotational disordering distinguishes the ultra-dispersed form of polytetrafluoroethylene from the standard one (fluoroplast-4), where only partial disordering is observed.

scholarly journals Crystallization of SHARPIN using an automated two-dimensional grid screen for optimization

2012 ◽  
Vol 68 (7) ◽  
pp. 816-819 ◽  
Author(s):  
Benjamin Stieglitz ◽  
Katrin Rittinger ◽  
Lesley F. Haire
Keyword(s):  
Escherichia Coli ◽  
Protein Concentration ◽  
Unit Cell ◽  
Data Sets ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
One Step

An N-terminal fragment of human SHARPIN was recombinantly expressed inEscherichia coli, purified and crystallized. Crystals suitable for X-ray diffraction were obtained by a one-step optimization of seed dilution and protein concentration using a two-dimensional grid screen. The crystals belonged to the primitive tetragonal space groupP43212, with unit-cell parametersa = b = 61.55,c= 222.81 Å. Complete data sets were collected from native and selenomethionine-substituted protein crystals at 100 K to 2.6 and 2.0 Å resolution, respectively.

The External Shape of Human γ GI Immunoglobulin from Crystal Sections

1971 ◽  
Vol 29 ◽  
pp. 428-429
Author(s):  
L. W. Labaw
Keyword(s):  
Molecular Weight ◽  
Sodium Phosphate ◽  
Osmium Tetroxide ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
X Ray ◽  
Large Molecular Weight ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Crystallographic Axes

Crystals of a human γGl immunoglobulin have the external morphology of diamond shaped prisms. X-ray studies have shown them to be monoclinic, space group C2, with 2 molecules per unit cell. The unit cell dimensions are a = 194.1, b = 91.7, c = 51.6Å, 8 = 102°. The relatively large molecular weight of 151,000 and these unit cell dimensions made this a promising crystal to study in the EM.Crystals similar to those used in the x-ray studies were fixed at 5°C for three weeks in a solution of mother liquor containing 5 x 10-5M sodium phosphate, pH 7.0, and 0.03% glutaraldehyde. They were postfixed with 1% osmium tetroxide for 15 min. and embedded in Maraglas the usual way. Sections were cut perpendicular to the three crystallographic axes. Such a section cut with its plane perpendicular to the z direction is shown in Fig. 1.This projection of the crystal in the z direction shows periodicities in at least four different directions but these are only seen clearly by sighting obliquely along the micrograph.

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