We have succeeded in the first direct observation under high pressure of the elementary steps (7.2 nm high) on {011} faces of glucose isomerase (GI) crystals, by using a laser confocal microscope combined with a differential interference contrast microscope (LCM-DIM) and a specially designed high-pressure vessel with a sapphire window of 1 mm thickness. The images of elementary steps taken under 50 MPa exhibited a sufficiently high contrast level for subsequent studies of crystal growth. By in situ observations, we directly confirmed that, irrespective of pressure, {011} faces of GI crystals grew by two-dimensional (2D) nucleation growth of the polynucleation type, and that pressure did not affect growth morphology. We measured the solubility of GI crystals under high pressure by observing in situ the growth and dissolution of elementary steps and ridges on the crystals. The resulting solubility curve exhibited much higher precision than those determined by interferometry, and revealed a significant decrease in solubility with increasing pressure. We also measured the 2D nucleation rates of 2D islands and the velocities of elementary steps under high pressure.

The perpendicular fracture surface of a dried colloidal crystal with pillar-like grains, obtained by centrifugation of a dispersion of polystyrene particles, was observed using a scanning electron microscope. Many grain boundaries on the fracture surface were observed at the particle level. Most of the particles on the surface showed a face-centered cubic (FCC) array. Although some grains were single FCC ones, other FCC grains contained some stacking disorders. Most of the surface was covered with such grains, and the grain boundaries formed a mosaic-like pattern. From these results, we confirmed that the colloidal crystals obtained by centrifugation formed a bundle structure of pillar-like FCC grains. A fracture surface adjacent to the side wall of the growth cell was also observed. The surface was composed of several layers. In the uppermost layer closest to the wall, numerous point defects and mismatches of triangular lattices between the neighboring two-dimensional islands were observed. These mismatches and point defects probably generated several lattice defects in the crystal. Similar generation of lattice defects probably occurred at the bottom of the container or the growth front of the crystals. Screw dislocations were also found in the layers, although they were not observed frequently. From these results, it was concluded that two-dimensional nucleation growth and spiral growth probably occurred on the crystal-dispersion interfaces of colloidal crystals as well as on the surface of atomic crystals.