Tetsuo Inoue

Recrystallization of Cu-phthalocyanine on KCl (001) substrates by annealing method

Abstract In order to establish the general way to prepare thin film crystals of organic semiconductors, we studied annealing effects on the heteroepitaxial growth of Cu-phthalocyanine (CuPc) crystallites on KCl {0xa00xa01} substrate crystals. CuPc was deposited on a cleaved KCl single crystal by vacuum evaporation (under 10 −4 xa0Torr). Then, the sample was taken out from the vacuum chamber and annealed in the air. On the CuPc as-deposited surface, no clear contrast was observed by scanning electron microscopy (SEM). On the contrary, many needle-like crystallites could be observed after the annealing treatment. Those crystallites were oriented so that their long axis was parallel to the 〈1xa00xa00〉 direction of the KCl substrate. We also investigated the effects of the annealing temperature and annealing duration time to find an optimal annealing condition.

Enhancement of Crystallization of Hard Spheres by Gravity: Monte Carlo Simulation

We present the effects of gravity on the growth of a hard-sphere (HS) crystal as determined by Monte Carlo simulations. HSs were confined between hard walls at the top (z=Lz) and the bottom (z=0) of the system with a periodic boundary condition in the horizontal direction. After preparing a melt state as an initial state, the gravity was suddenly switched on. The values of the gravity were mg?/kBT(?g*)=0.1,0.2,...,2.0, where m was the mass of a HS, g the acceleration of gravity, ? the HS diameter, and kBT the temperature multiplied by Boltzmanns constant. We observed the enhancement of crystallization due to gravity up to g*=0.7 and that the crystals of largest size were formed at g*=0.7?0.9. On the other hand, for g*?1.0, the top position of the HS crystal that was grown from the bottom became lower with an increase in the gravity, where crystals with various axis directions coexisted. The polycrystallization is speculated to occur due to polynucleation. These results are qualitatively consistent with those of an experimental study of the centrifugal sedimentation of colloidal crystallization.

Various Growth Shapes of Na2S2O3 5H2O Crystals

The relation between the growth shapes and supersaturations and/or supercoolings was investigated in the Na 2 S 2 O 3 .5H 2 O crystals: (i) The growth shapes changed from a hexagonal prismatic crystal, aggregate of platy crystals and to a spherulite with an increase of supersaturations and/or supercoolings. (ii) The deposition rate suddenly increased at a certain supersaturation and/or supercooling, where the growth shape changed from the hexagonal prism to the aggregate of platy crystals. (iii) The deposition rates of spherulites become higher with increasing the solute concentrations. (iv) The formation process of the spherulites were in situ observed by the Schlieren and/or Mach-zehnder interferometer methods.

Effects of impurity upon the habit changes in NaBrO3 crystals grown from aqueous solution

Abstract The effects of impurity (acetic acid, 1.15xa0mol%) upon the habit changes of NaBrO 3 crystals have been investigated. The crystals were grown from aqueous solution under the following conditions: (i) supersaturations: ln(C/Ce)=0–0.24, (Ce: equilibrium mole fraction), (ii) growth temperatures: 20–64°C. The results of habit changes were shown in a plot of growth temperature against supersaturation (such a plot is called a morphodrome). It was found that the impurity effects on the habit changes were more important in the low supersaturation range than in the high supersaturation range.

Growth and perfection of KCl crystals grown from aqueous solution

Abstract KCl crystals were grown from aqueous solution by the evaporation method at the growth temperature of 40°C, the Pb ion concentration was 0–1/2000 in molar fraction, the pH was 2.0–4.0, the evaporation rate 0.4–1.1 g/day and the duration of growth 5–32 days. The results obtained are summarized as follows. (1) Pb ion addition played the most important role for growing larger KCl crystals, since it reduced the generation of parasite crystals. (2) Growth shape changed from cubic to octahedral with increasing Pb ion concentration. (3) Dislocation density in the crystals grown from seeds was always much higher than that in the crystals grown from spontaneous nuclei. Some crystals grown from spontaneous nuclei were nearly free of dislocations. (4) Growth striations were always observed on the etched {100} surfaces of KCl crystals grown in this work. A growth history could be seen from the change of striation pattern with the growth.

Growth of Cobalt-Phthalocyanine on KCl (001) Substrate and Copper-Phthalocyanine Whisker

Metal-phthalocyanines (MPc’s) are promising organic semiconductor materials whose electronic and optical properties can be changed by substituting their central metals. In our previous study, we reported the epitaxial growth of copper-phthalocyanine (CuPc) on a KCl {001} substrate by a vapor deposition and thermal treatment (VDTT) method 1) (Figure 1). A needle-like copper-phthalocyanine (CuPc) whisker, which was approximately 30 nm in diameter and 1 mm in length, was epitaxially grown on a KCl substrate. The CuPc whiskers were oriented so that their long axes were parallel to the h100i direction of the KCl substrate at an incline of about 56 � with the substrate. The first question is whether these phenomena can be obtained when other phthalocyanines grow on the KCl substrate. Therefore, we first examined the growth of cobalt-phthalocyanine on a KCl {001} substrate. This direction-controlled crystallite has potential to be used in nano-sized organic devices. To realize the fabrication of such devices, a study of the heteroepitaxy of organic crystals is believed to be important. The correspondence of the lattice constant of the organic crystal with that of the substrate is one of the required conditions for heteroepitaxial growth. Hence, the epitaxial growth of organic molecules is generally difficult because of the different sizes and shapes of the molecules of the epitaxial crystals and substrates. However, CuPc and CoPc have quite similar crystal structures 2) and should therefore satisfy this condition. The second purpose of this work is to study the heteroepitaxial growth of CoPc on CuPc by repeated VDTT. 2. Experiments A single crystal of KCl was grown by the Czochralski method and cleaved through its {001} plane. The CuPc and CoPc were purchased from Aldrich Co. and Tokyo Kasei Kogyo Co., Ltd., respectively, and were used without further purification. The crystallization of CoPc grown on the KCl {001} substrate was carried out by VDTT. 30 mg of CoPc powder was placed in a molybdenum boat, and the boat was mounted in the lower part of a vacuum chamber. A crystal substrate was placed in the upper part of the chamber so that its surface was facing downward. The distance between the (a)

Habit changes in NaBrO3 crystals grown from an aqueous solution

The growth of sodium bromate (NaBrO3) from an aqueous solution has been observed over a range of temperatures (29–46°C) and supersaturations (In(CCe) = 0.01–0.1, Ce: equilibrium mole fraction). The gross morphologies of the crystals grown in this experiment have taken three distinct forms: cubic, tetrahedral and polyhedral. The controlling factors have been found to be growth temperature and supersaturation (chemical potential).

Striations in the KCl single crystals grown from aqueous solutions

Abstract Growth striations were always observed on the etched surfaces of KCl crystals grown from aqueous solutions doped with Pb. However, the origin of the striations is not known in the case of aqueous solution growth. In this work, it was studied how the width and period among the striations were influenced by the growth rate and concentration of the dopant Pb. The crystals were grown from the aqueous solutions doped with Pb (1/4000–1/1250 in molar fraction) by an evaporation method at pH=2.0. The average growth rates were changed from 24 to 115xa0μm/day by controlling the evaporation rate. It was found that both the width and period among the striations decreased with an increase of the average growth rate. However, the effects of the concentration of dopant Pb upon the width and period among the striations were not found within the concentration range examined.

Liquid phase epitaxial growth of bismuth based superconductors

Abstract The liquid phase epitaxial growth of superconducting films of Bi 2 Sr 2 CaCu 2 O y (2212 phase) and Bi 2 Sr 2 CuO z (2201 phase) were carried out on three types of substrates; SrTiO 3 , LaAlO 3 and NdGaO 3 . Twinning structures of the 2212 phase were observed in the films grown on the SrTiO 3 (100) and LaAlO 3 (100) substrates which belong to the cubic crystal system, while nearly twin-free structures were obtained when the film was grown on the NdGaO 3 (001) substrate (orthorhombic system). Atomic force microscopy revealed a 2201 phase film with a reasonably flat area (several μm 2 ) grown on the LaAlO 3 (100) substrate. It was observed that the 2212 phase nucleated on the substrate following the Volmer-Weber type mechanism (three-dimensional island growth mode). The enlarging processes of the island layers were discussed.

Growth of High Tc Crystals

Since the discovery of Ba-La-Cu-O compounds of high T c superconductors by Bednorz and Muller [1] , many papers have been published on the various types of high T c superconductors containing copper oxides such as LnBa 2 Cu 3 O y (123 type), where Ln is a rare earth atom and Y, and Bi-Sr-Ca-Cu-O (BSCCO) compounds. This chapter is made up of the following three parts: 1. Growth of the high T c phase of BSCCO ( T c ~ 100 K)