Crystal growth, spectroscopic characterization, and laser performance of Tm:LiLuF4 crystal

The National Science Foundation of China(Grant No. 60578044).

Effects and numerical analysis of argon gas flow on the oxygen concentration in Czochralski silicon single crystal growth

Argon gas, as a protective environment and carrier of latent heat, has an important effect on the temperature distribution in crystals and melts. Numeric simulation is a potent tool for solving engineering problems. In this paper, the relationship between argon gas flow and oxygen concentration in silicon crystals was studied systematically. A flowing stream of argon gas is described by numeric simulation for the first time. Therefore, the results of experiments can be explained, and the optimum argon flow with the lowest oxygen concentration can be achieved. (C) 2002 Elsevier Science B.V. All rights reserved.

PRELIMINARY-RESULTS OF GAAS SINGLE-CRYSTAL GROWTH UNDER HIGH GRAVITY CONDITIONS

GaAs single crystals have been grown under high gravity conditions, up to 9g0, by a recrystallization method with decreasing temperature. The impurity striations in GaAs grown under high gravity become weak and indistinct with smaller striation spacings. The dislocation density of surcharge-grown GaAs increases with increase of centrifugal force. The cathodoluminescence results also show worse perfection in the GaAs grown at high gravity than at normal earth gravity.

PHYSICAL VAPOR TRANSPORT AND CRYSTAL-GROWTH OF GESEXTE1-X SOLID-SOLUTIONS

Physical vapor transport studies of GeSe(x)Te1 - x (x = 0.1, 0.2, 0.3, and 0.4) solid solutions demonstrated, that individual, large single crystals of these materials can be grown in closed ampoules. A compositional analysis of the grown crystals revealed, that the mass transport (crystal growth) process under steady-state conditions is pseudo-congruent and controlled by diffusion processes in the source material. From these experiments, the degree of non-stoichiometry (Ge-vacancy concentrations) of GeSe(x)Te1 - x single crystals could be estimated. The effects of the cubic to rhombohedral phase transformation during cooling on the microstructure and morphology of the grown mixed crystals are observed. This work provides the basis for subsequent defect studies and electrical measurements on these crystals.

Effects and numerical analysis of argon gas flow on the oxygen concentration in Czochralski silicon single crystal growth

Argon gas, as a protective environment and carrier of latent heat, has an important effect on the temperature distribution in crystals and melts. Numeric simulation is a potent tool for solving engineering problems. In this paper, the relationship between argon gas flow and oxygen concentration in silicon crystals was studied systematically. A flowing stream of argon gas is described by numeric simulation for the first time. Therefore, the results of experiments can be explained, and the optimum argon flow with the lowest oxygen concentration can be achieved. (C) 2002 Elsevier Science B.V. All rights reserved.

Effects of forced solution flow on lysozyme crystal growth

In order to study quantitatively the effects of forced solution on crystal growth, we designed a new set of experimental equipment, in particular, a microchannel mixer was used as crystallization container so that the consumption of protein samples was much reduced and thus an exact syringe pump could be used for precise control of the flow rates. Since the mixer’s section was designed to be rectangular, the solution velocity in its center was steady and constant, and thus repeatable experiments were facilitated. Experimental results showed that the effects of forced solution on protein crystal growth were different under different levels of supersaturation, and new results were obtained for cases of high supersaturation. When the supersaturation is σ = 2.3, with increasing flow rates the growth rates of the lysozyme crystal’s (110) face hardly change when the flow rates are lower than 1300 μm/s, and decrease quickly afterwards. When the flow rate reaches 2000 μm/s, the crystal nearly ceases to grow. When the supersaturation is σ = 2.7, with increasing flow rates the (110) face growth rates increase at the beginning then reach the maximum values at 1700 μm/s – 1900 μm/s and decrease afterwards, approaching zero or so when the flow rate reaches 12000 μm/s. The higher the supersaturation, the larger the flow rate at which the crystal ceases to grow. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Crystal Growth Transition from Flat-On to Edge-On Induced by Solvent Evaporation in Ultrathin Films of Polystyrene-b-Poly(ethylene oxide)

The transition of lamellar crystal orientation from flat-on to edge-on in ultrathin films of polystyrene-b-poly(ethylene oxide) (PS-b-PEO) via solvent vapor (toluene) treatment Was investigated. When the as-prepared film was treated in saturated solvent vapor, breakout crystals could form quickly, and then they transformed from square single crystals (flat-on lamellae) to dendrites and finally to nanowire crystals (edge-on lamellae). Initially, heterogeneous nucleation tit the polymer/substrate interface dominated the structure evolution, leading to flat-on lamellar crystals orientation. And the transition from faceted habits to dendrites indicated a transition of underlying mechanism from nucleation-controlled to diffusion-limited growth. As the solvent molecules gradually diffused into the polymer/substrate interface, it will subsequently weaken the polymer-substrate interaction.