GROWTH OF ELECTROCRYSTALLIZED ZNO PARTICLES BY REACTION OF VACUUM-DEPOSITED ZN FILMS WITH DISTILLED WATER

Products by electrochemical reaction of vacuum-deposited Zn firms with distilled water at 20 degrees C are investigated by scanning electron microscopy (SEM) and an X-ray diffraction method. The time dependence of the pH of the water indicates three stages of the reaction; the initial stage I at pH = 7 for about 20 h, the middle stage II at pH > 7 (Max = 7.7) for about 100 h and the final stage III at pH = 7. In stage I etching pits occur as a result of the local cell formation. Each pit is enclosed by a ZnO bank on the ring margin of 10-100 mu m in diameter. Stage II is characterized by the growth of many spindle-like ZnO particles on the speckles which are traces of the pits of stage I. The ZnO banks dissolve and dendritic beta-Zn(OH)(2) crystals also appear near the margins. The spindle crystals disappear in stage III. The formation and morphology of the spindle crystals are described.