GROWTH AND MELTING OF THE CLEAVAGE FACE $\{10 \bar{1}1\}$ of Yb:YAl3(BO3)4 Crystal

Yb:YAl3(BO3)4 (YbYAB) is a self-frequency-doubling laser crystal. In this paper, we report a series of atomic force microscopy (AFM) observations on the growth and melting of the cleavage face [Formula: see text] of the crystal. Both growth and nucleation rates are very fast when the flux temperature is 0.5–1.5°C below the saturation point. These fast growth and nucleation rates are related to the nonsaturated bonds on the cleavage face formed during cleaving. The growth morphologies sensitively change to spiral melting holes when the flux temperature increases by only 0.5°C above the saturation point. When the temperature increases by another 1°C, the spiral melting mechanism transforms into a two-dimensional nucleation melting mechanism. The heights of the growth or melting steps are n × unit height of the structure layer in this direction. The melting step height increases much as the temperature increases by 1°C, but the growth step height increases only a little as the temperature decreases by 1°C. The melting steps are much wider than the growth steps, which reflects the fact that the melting centers (or melting nuclei), unlike the growth nuclei, are difficult to form. The growth morphology is not reverse-symmetric to the melting morphology as the temperature variation is reverse-symmetric on the saturation point.

MORPHOLOGY AND GROWTH MECHANISM OF THE $\{11\bar{2}0\}$ FACE OF Yb:YAl3(BO3)4 CRYSTAL

Yb:YAl 3( BO 3)4 (YbYAB) is a self-doubling frequency laser crystal. Based on atomic force microscopy (AFM) observations, a series of growth morphologies formed after different growing times on the smooth [Formula: see text] face are reported in this paper. No two-dimensional nuclei or growth steps have been found on this face after growth of several seconds, or even several minutes. This reflects the fact that at the beginning stage, the growth rate of the [Formula: see text] face is much slower than that of the [Formula: see text] cleavage face of YbYAB crystal (reported in our previous work). The reason is the different properties of nonsaturated bonds on the surfaces between a cleavage face and a natural face. After growth of 50 min, checklike morphologies of a special kind develop on the face. These morphologies result from twin structure. The growth steps with small heights (~ 0.6 nm) cannot cross the two twinned crystal regions, but those with large heights (6–8 nm) can cross by changing the directions at the twin boundaries. We have also observed the rough morphology of the [Formula: see text] face obtained by spontaneous nucleation growth at a high rate. The rough morphology is composed of many small [Formula: see text] faces with the same orientation but very different heights. This reflects the fact that the rough face does not grow by accumulating the growth units irregularly.

Structure of Octacyanophthalocyanine Derivatives Prepared by CVD

Phthalocyanine compounds have been attracting a good deal of attention as semiconductors and photoconductors. We have studied the crystal structure of octacyanophthalocyanine(2a)-metal complex crystal prepared by CVD reaction of 1,2,4,5-tetracyanobenzene (TCNB:1a) with metal films by HREM. In the case of 2a-K complex crystal, the high resolution image of the crystal showed a grid pattern with a spacing of 1.57nm, as is shown in Fig.1. The planar molecules of 2a stacked along a column to coordinate with the intercalated potassium atoms in the complex crystal. In this study, we examined the structure of the films prepared by CVD reaction of TCNB derivatives, which were introduced iodides(1b) or chlorines(1c) into 3 and 6 positions of TCNB, with KCl.The films were prepared on a cleavage face of KCl single crystal by heating with the powders of 1b and 1c in an evacuated sealed tube at 350 C for 12h. The specimens were examined in a JEOL-200CX microscope equipped with a minimum dose system.