PREPARATION AND STRUCTURE OF Q-STATE LEAD SULFIDE MONOLAYERS IN METASTABLE STEARIC-ACID LANGMUIR-BLODGETT-FILMS

Monolayers of Q-state PbS were prepared by exposure of Langmuir-Blodgett (LB) films of lead stearate to H2S at a pressure of 1 Torr. Its long spacing measured by X-ray diffraction is 50.5 +/- 0.2 angstrom which is just the same with that of lead stearate LB films. It was determined by X-ray diffraction and IR that the hydrocarbon chains are still packed in an orthorhombic unit cell after the reaction. The carboxylic groups yielded by the reaction form a ring structure by hydrogen bonds which controls PbS within a monolayer. A structured UV-visible absorption spectrum of the PbS monolayer was obtained. The PbS monolayer consists of a two-dimensional domain or linear form of PbS. The latter is more possible. Their size is almost homogeneous. The onset of the absorption of PbS monolayer is blue-shifted by 1.4 eV with respect to bulk PbS.