Growth of Optical Crystals by the Micro-Pulling-Down Method

MRS Bulletin ◽  
2009 ◽  
Vol 34 (4) ◽  
pp. 266-270 ◽  
Author(s):  
Akira Yoshikawa ◽  
Valery Chani
Keyword(s):  
Cross Sections ◽  
Driving Forces ◽  
General Scheme ◽  
Crystal Shape ◽  
Growth Interface ◽  
Crucible Bottom ◽  
Growth System ◽  
Growth Method ◽  
Crystal Fibers ◽  
Made In

AbstractThe micro-pulling-down technique is a crystal growth method that has been mostly developed since 1992. The general scheme of the growth system is relatively simple: the melt (oxide, fluoride, metal) residing in a crucible is transported in downward through microcapillary channel(s) made in the bottom of the crucible. Two driving forces (capillary action and gravity) support the delivery of the melt to the liquid/solid growth interface formed under the crucible due to a properly established temperature gradient. Appropriate configuration of the crucible bottom allows for controlling of the crystal shape (fibers, rods, tubes, plates) and the dimensions of the crystals' cross sections that range approximately from 0.1 to 10 mm. A great number of scientifically and industrially important optical crystal fibers have been successfully produced using this method.

Mg-Doped Sapphire Crystal Fibers Grown by Laser-Heated Pedestal Growth Method

2006 ◽  
Vol 45 (1A) ◽  
pp. 194-199 ◽  
Author(s):  
Che-Ming Liu ◽  
Jyh-Chen Chen ◽  
Chang-Hung Chiang ◽  
Long-Jang Hu ◽  
Sheuan-Perng Lin
Keyword(s):  
Sapphire Crystal ◽  
Growth Method ◽  
Crystal Fibers ◽  
Laser Heated ◽  
Mg Doped

InSb Czochralski Growth Single Crystals for InGaSb Substrates

2014 ◽  
Vol 1616 ◽  
Author(s):  
J. E. Flores Mena ◽  
R. Castillo Ojeda ◽  
J. Díaz Reyes
Keyword(s):  
Low Cost ◽  
Electronic Devices ◽  
Czochralski Method ◽  
Liquid Nitrogen Temperature ◽  
Longitudinal Optical ◽  
Czochralski Growth ◽  
Etch Pit ◽  
Growth System ◽  
Radiation Sensors ◽  
Made In

ABSTRACTThe massive crystal growth of single crystal semiconductors materials has been of fundamental importance for the actual electronic devices industry. As a consequence of this one, we can obtain easily a large variety of low cost devices almost as made ones of silicon. Nowadays, the III-V semiconductors compounds and their alloys have been proved to be very important because of their optical properties and applications. It is the case of the elements In, Ga, As, Sb, which can be utilized for the fabrication of radiation sensors. In this work we present the results obtained from the ingots grown by the Czochralski method, using a growth system made in home. These results include anisotropic chemical attacks in order to reveal the crystallographic orientation and the possible polycrystallinity. Isotropic chemical attacks were made to evaluate the etch pit density. Metallographic pictures of the chemical attacks are presented in this work. Among the results of these measurements, the best samples presented in this work showed mobilities of 62.000 cm2/V*s at room temperature and 99.000 cm2/V*s at liquid nitrogen temperature. Typical pit density was 10,000/cm2. The Raman spectra present two dominant peaks associated at Transversal Optical (TO)- and Longitudinal Optical (LO)-InSb, the first vibrational mode is dominant due to the crystalline direction of the ingots and second one is associated to high defects density.

Subgrain Structures Characterized by Electron Backscatter Diffraction (EBSD)

2014 ◽  
Vol 794-796 ◽  
pp. 3-8 ◽  
Author(s):  
Sindre Bunkholt ◽  
Knut Marthinsen ◽  
Erik Nes
Keyword(s):  
Driving Forces ◽  
Electron Backscatter Diffraction ◽  
Subgrain Growth ◽  
Electron Backscatter ◽  
Physically Based ◽  
Physically Based Models ◽  
Photo Editing ◽  
Backscatter Diffraction ◽  
Ebsd Method ◽  
Made In

Subgrain structures are frequently characterized by the electron backscatter diffraction (EBSD) method, which is both accurate and provides good statistics. This is essential to better understand the subgrain growth mechanisms and e.g. establish the driving forces and motilities for comparison with physically based models. However, there is no commercially available software which can provide adequate subgrain boundary maps necessary for e.g. size and misorientation analysis. Here, a method that produces such maps utilizing only commercially available software is presented. The clue is to provide the EBSD-software with a parameter that can be used to identify all subgrains. By combining various maps exported from the EBSD-software into photo editing software, a new map is made in which all subgrain boundaries are identified. Missing and incomplete boundaries are traced manually before a reconstructed subgrain map is generated and imported back into the EBSD-software. With this method, the built-in algorithms in the EBSD-software can be readily used to e.g. characterize subgrain growth in aluminium with respect to orientation, size and misorientation.

Indentation plastic displacement field: Part I. The case of soft films on hard substrates

1999 ◽  
Vol 14 (6) ◽  
pp. 2196-2203 ◽  
Author(s):  
T. Y. Tsui ◽  
Joost Vlassak ◽  
William D. Nix
Keyword(s):  
Plastic Deformation ◽  
Cross Sections ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Porous Titanium ◽  
Titanium Layer ◽  
Plastic Deformation Behavior ◽  
Plastic Displacement ◽  
Film Substrate ◽  
Made In

The plastic deformation behavior of Knoop indentations made in a soft, porous titanium/aluminum multilayered thin film on a hard silicon substrate is studied through use of the focused-ion-beam milling and imaging technique. Pileup is observed for indentations with depths larger than 30% of the total film thickness. Analysis of the indentation cross sections shows that plastic deformation around the indentation is partly accommodated by the closing of the pores within the multilayers. This densification process reduces the amount of pileup formed below that predicted by finite element simulations. Experimental results show that the pileup is formed by an increase of the titanium layer thickness near the edges of the indentation. The thickness increase is largest near the film/substrate interface and decreases toward the surface of the multilayered film. The amount of normal compression near the center of the indenter is characterized, and it is demonstrated that the deformation becomes more nonuniform with increasing indentation depth.

Control of Flow Pattern and Solidification Interface Shape in an Induction Heated Czochralski Crystal Growth System

2007 ◽  
Author(s):  
Haisheng Fang ◽  
Lili Zheng ◽  
Hui Zhang
Keyword(s):  
Crystal Growth ◽  
Natural Convection ◽  
Rotation Rate ◽  
Melt Inclusion ◽  
Interface Shape ◽  
Growth Interface ◽  
Solidification Interface ◽  
Crystal Rotation ◽  
Growth System ◽  
Stagnant Point

Optical crystals grown by Czochralski technique from a solute-rich melt usually suffer defects of melt inclusion or bubble core defects, which severely affect the optical, thermal and mechanical properties of the material. It is well known that the formation of melt inclusion or bubble core is highly related to species distribution in the growth system especially at the solidification interface and the shape of the growth interface. This paper has examined the flow pattern and solidification interface changes by changing the forced convection, e.g., crystal rotation and by changing the natural convection, e.g., inserting a horizontal disk plate. The relative effect of fluid-flow convection modes in the melt associated with crystal rotation rate is represented by a dimensionless parameter, Gr/Re2. Increasing the rotation rate will cause the solid-liquid interface change from the convex shape to concave. When the crystal rotation rate is relatively low and natural convection is strong, Gr/Re2 is large. In this case, the concentration of species pertinent to melt inclusion moves down along the axis of rotation. When the crystal rotation rate is increased, the value of Gr/Re2 decreases. The precipitated composition spreads over the growing interface may then be swiped away from the growth interface by increased crystal rotation. Melt inclusion-free crystals can thus be obtained. The relationship between Gr/Re2 and growth interface shape change is achieved by numerical simulations. The stagnant point location as a function of crystal rotation is also presented, which shows that the stagnant point moves outward by increasing Reynolds number and/or reducing Grashof number. From such understanding, the interface shape and melt inclusion position can then be controlled through control of Gr/Re2 in the growth system. Many times, it is, however, not practical in the experiments to use a high rotation rate for optical crystal growth since high rotation rate will introduce the striation defects. A new design to reduce natural convection is then proposed to improve the effect of crystal rotation and to control the solidification interface shape. Numerical simulations have been performed to demonstrate the possibility of the new design. Results show that such design is very effective and practical to control the melt inclusion and the solidification interface shape.

scholarly journals A Study of the Vibrational Excitation of H2 by Measurements of the Drift Velocity of Electrons in H2−Ne Mixtures

1988 ◽  
Vol 41 (4) ◽  
pp. 573 ◽  
Author(s):  
JP England ◽  
MT Elford ◽  
RW Crompton
Keyword(s):  
Cross Section ◽  
Drift Velocity ◽  
Cross Sections ◽  
Excitation Cross Section ◽  
Vibrational Excitation ◽  
Pure Hydrogen ◽  
Velocity Data ◽  
Highly Sensitive ◽  
Hydrogen Mixtures ◽  
Made In

Measurements of electron drift velocities have been made in 1�160% and 2�892% hydrogen-neon mixtures at 294 K and values of EI N from 0�12 to 1�7 Td. The measurements are highly sensitive to the region of the threshold of the v = 0 → 1 vibrational excitation cross section for hydrogen and have enabled more definitive tests of proposed cross sections to be made than was possible using drift velocity data for H2−He and H2−Ar mixtures. The theoretical v = 0 → 1 vibrational excitation cross section of Morrison et al. (1987) is shown to be incompatible with the present measurements. A new set of hydrogen cross sections has been derived from the available electron swarm measurements in pure hydrogen and hydrogen mixtures.

The Resistance of Inclined Struts in a Uniform Air Current

1915 ◽  
Vol 19 (73) ◽  
pp. 7-12 ◽  
Author(s):  
A. P. Thurston ◽  
N. Tonnstein
Keyword(s):  
Cross Sections ◽  
Constant Velocity ◽  
Equal Length ◽  
Maximum Width ◽  
Air Resistance ◽  
The Cross ◽  
Made In

These experiments were carried out in the aerodynamical laboratory at East London College, with a view to investigating the variation of air resistance of certain bars as the inclination of their longitudinal axes to the direction of the wind was varied, the current of air being kept at a constant velocity. Four bars were used, having the cross sections shown in Fig. I, that is, a square, a 2:1rectangle, a circle, and a 3:1 streamline form. The bars were carefully made in wood to an equal length of 34m. and approximately a maximum width of lin. in each case. It was thought that interference due to the ends of the bars would be minimised by having some sort of entering edge fitted to the flats. Accordingly, wedge-shaped ends were tried in the case of a fifth bar, but various difficulties seemed to lead to erroneous results and they were abandoned in favour of squared-off ends.

Organic Analysis of Hevea Latex VIII. Development of a General Scheme of Analysis

1946 ◽  
Vol 19 (3) ◽  
pp. 781-787 ◽  
Author(s):  
R. F. A. Altman
Keyword(s):  
Organic Compounds ◽  
General Scheme ◽  
Practical Experience ◽  
The Other ◽  
Complete Analysis ◽  
Organic Analysis ◽  
Original State ◽  
Quantitative Separation ◽  
Ideal Method ◽  
Made In

Abstract An attempt is made in this work to show the desirability and the practicability of a complete analysis of Hevea latex. It has been found that fresh, unammoniated latex is the only trustworthy starting material for analysis. Difficulties encountered in the analysis are due principally to (1) the trouble-some property of the rubber hydrocarbon to adsorb, and hold firmly, the other components of latex; (2) probable chemical, enzymic, and bacterial changes, which cause great difficulties in the isolation of those components in the state in which they are originally present in latex, and (3) the lack of proven methods of quantitative separation of the various groups of organic compounds. In his attempt at an ideal method of analysis, the author, due to the above-named difficulties, is faced with the apparent impossibility, as yet, of separating the various components of latex quantitatively and in the original state in which they are present in the latex. As a result of much theoretical considera- tion and practical experience, gained meantime, the author has reached a method, the scheme of which is described in the present work.

scholarly journals The scattering of hydrogen positive rays, and the existence of a powerful field of force in the hydrogen molecule

1922 ◽  
Vol 102 (715) ◽  
pp. 197-209 ◽  
Keyword(s):  
Electric Fields ◽  
General Scheme ◽  
Hydrogen Gas ◽  
Theoretical Interpretation ◽  
Scattering Medium ◽  
Hydrogen Atoms ◽  
Hydrogen Molecules ◽  
Nuclear Particle ◽  
Positively Charged ◽  
Made In

In view of the extremely important results obtained by Sir E. Rutherford and others from a study of the scattering of α -rays, it seemed worth while to investigate the scattering of particles moving with smaller velocities such as occur in the positive rays. The most interesting, because the simplest, are the rays of positively charged hydrogen atoms, which presumably consist simply of a nuclear particle, or proton. The experiments described in this paper were made in some cases with these rays, in others with the positively charged hydrogen molecules, systems consisting of two protons and one electron. The scattering medium was in all cases hydrogen gas. This was chosen largely for convenience, as the experimental arrangement is considerably simplified if the same gas is used to produce the rays and to scatter them, and also because, with the exception of helium, the molecule of hydrogen is the simplest known, and there seemed more hope of obtaining results which could be given a definite theoretical interpretation. The general scheme of experiment was to produce the rays in a discharge tube, analyse them by magnetic and electric fields in the ordinary way, cut off all except those of the kind required by a slotted diaphragm, pass the remainder through a chamber containing the scattering gas, and receive them in a Faraday cylinder arranged behind a slit of variable width. The experiment consisted in finding how the charge received by the Faraday cylinder varied with the width of the slit, when this was made wider than the geometrical “shadow” of the slot in the diaphragm. Any rays lying outside this “shadow” must have been scattered.

Determination of Fiber Cross-Sectional Circularity From Measurements Made in a Longitudinal View

1979 ◽  
Vol 101 (1) ◽  
pp. 59-64 ◽  
Author(s):  
R. L. Barker ◽  
D. W. Lyons
Keyword(s):  
Cross Sections ◽  
Analytical Procedure ◽  
Cross Sectional ◽  
Longitudinal View ◽  
Made In

A procedure is described for obtaining information concerning the circularity of fiber cross-sections from measurements made in a longitudinal view of the fibers. A method is developed for viewing and measuring the projected diameter of fibers viewed longitudinally, and an analytical procedure is described for analyzing these measurements to determine the flatness or roundness of the fiber cross-sections. Experimentation conducted to test the reliability of these procedures is discussed as these methods are used to measure numerous different samples of fibers of known and varied cross-sectional shapes and sizes.

Sign in / Sign up

Export Citation Format

Share Document