14 August 1998
Vol 281, Issue 5379

About The Cover

Cover image expansion

COVER Colored scanning tunneling microscope image (75 nanometers wide) of the (0001) surface of gallium nitride, a semiconductor used in the development of intense blue and green lasers and light-emitting diodes. Two growth fronts spiral away from a point at which a screw dislocation intersects the surface. See H. J. Queisser et al. on 945 and the special section beginning on 939. [Photo: A. R. Smith, R. M. Feenstra, D. W. Greve]