SPIRAL GROWTH OF C-FACETS IN HE-4 CRYSTALS AT MK-TEMPERATURES

We have made detailed investigations on spiral growth of c-facets in h elium crystals with dislocation densities similar to 10 cm(-2). Our re sults at high temperatures T = 100 - 200 mK agree quite well with the classical parabolic power law for spiral growth, whereas a linear depe ndence on the driving pressure is observed at 2 - 20 mK. This is a con sequence of the inertia of elementary steps in the situation when damp ing due to phonons is small. At high velocities, all our data display a tendency to saturation which is interpreted as an indication of step localization at large driving forces.