INVESTIGATION OF STEARIC-ACID AND MANGANESE STEARATE FILMS OBTAINED BY LANGMUIR-BLODGETT AND VACUUM DEPOSITION METHODS

The molecular structure and morphology of 1-100 nm films, prepared by vacuum deposition of stearic acid (HSt) and manganese stearate (MnSt(2)) on Si, NaCl and C/NaCl substrates, have been investigated by Fourier transform IR spectroscopy, scanning electron microscopy and transmission electron diffraction techniques and compared with characteristics of Langmuir-Blodgett films on Si. Contrary to previous work, more emphasis is placed on films a few nanometres thick. The parameters (frequencies and intensities) of the Davydov splitting components in IR spectra are evaluated to determine the molecular orientation and intermolecular interaction in these films. HSt shows a three-dimensional growth in vacuum-deposited films on all substrates studied which is evidence of a weak interaction of H-bonded HSt dimers and the substrate. MnSt, is found to decompose upon evaporation, resulting in stearone (C17H35)(2)CO formation and deposition. The orientation of these molecules depends on the substrate type. A Stranski-Krastanov growth mechanism is realized owing to the strong interaction of polar stearone molecules with the substrates. The possible reasons for the distinction of the HSt and the stearone interactions with the substrates are discussed. The Langmuir-Blodgett films exhibit a higher thickness uniformity but lower molecular ordering than vacuum-deposited films do.