Atomic-force microscope observation and molecular-scale flattening of the single-crystal surface of 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST)

The surface of an organic electro-optic crystal tends to be covered with a degenerate rough layer, which may cause light scattering or unfavorable tra nsmission of light. We demonstrate a novel method of removing this layer an d flattening the (001) surface of a 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) crystal on a molecular scale by applying suitable force on the tip of an atomic-force microscope (AFM). When the loading force on the AFM tip is kept near 10 nN, the DAST molecules can be removed layer by lay er. This method produced a large, flat terrace of 250,000 nm(2), and the mo lecular-scale flatness of this area was confirmed by AFM observation. (C) 2 000 Optical Society of America OCIS codes: 000.2170, 190.4400, 240.4350, 24 0.5450, 240.5770, 240.6700.