AFM AND X-RAY STUDIES OF FILMS FORMED BY THERMAL EVAPORATION AND BY THE LB TECHNIQUE

The object of this research was to compare multilayers formed by therm al evaporation and the LB technique and to investigate their structure by atomic force microscopy (AFM) and X-ray diffraction. Films of a wi de range of amphiphilic materials were formed by thermal evaporation i n vacuo onto substrates maintained at temperatures chosen to maximise order as evidenced by low angle X-rav diffraction. Where it was possib le multilayers of these materials were also formed by the Langmuir Blo dgett (LB) technique. The X-ray diffraction patterns obtained from fil ms formed in the two different ways are very similar. Studies of these films made by AFM show that, in most cases, there is substantial surf ace structure and terracing in the case of films formed by both techni ques. We have made particular studies of films of cadmium stearate. Mu ltilayers of this material made by thermal evaporation appear to consi st of platelets having a Y-structure whose planes are parallel to the substrate. LB films of this material show terracing but also flat area s. Even these areas contain circular defects less than a micron in dia meter which tend to multiply and grow with time. The best thermally ev aporated films we obtained were formed from N-methylstearamide. These films had relatively smooth surfaces showing only small steps and had a good Y-layer structure as evidenced by X-ray diffraction.