"Current-line driven" macropores: Which current?

In the electrochemical elaboration of porous semiconductors and for a certain class of macropores, the pore direction appears to follow the current lines. However, in the presence of a large transverse magnetic field, the current lines at the semiconductor/electrolyte interface exhibit an abrupt change of direction, the current lines on the semiconductor side being tilted with respect to the surface normal. We show here that the pore direction is also tilted, though to a much lesser extent. On the other hand, tilting the current line direction in the electrolyte does not affect the growth direction significantly. We conclude that the main factor governing the pore growth direction is the current direction in the space charge, which is essentially normal to the envelope of the pore fronts. The reasons for the presence of a small magnetic-field effect are discussed.