Langmuir Blodgett films are provided having second order molecular hyperpolarizability of at least 30.10.sup.-50 C.sup.3 m.sup.3 J.sup.-2. combined with chemical stability and a melting point of over 70.degree.. They also have desirable pyroelectric properties shown by a static pyroelectric coefficient of at least 0.0039 nCcm.sup.2 k.sup.-1. The films comprise compounds of the following formula: ##STR1## wherein M is ruthenium, iron or cobalt; R.sup.1 is cyclopentadienyl, methylcyclopentadienyl, pentamethylcyclopentadienyl or indenyl; A.sup.1 is (R.sup.2).sub.3 Z or carbonyl; Q.sup.2 is (R.sup.2).sub.3 Z or carbonyl; Z is phosphorus or arsenic; R.sup.2 is an aryl of alkyl radical; A is ##STR2## Y is a straight chain alkyl or alkoxy radical comprising from 3 to 17 carbon atoms, or, when A is ##STR3## N(R.sup.3).sub.2 ; R.sup.3 is a lower alkyl radical comprising up to 5 carbon atoms; and X is PF.sub.6 or BF.sub.4.
A layer of a hydrocarbon molecule is applied to a substrate by the Langmuir-Blodgett technique, and the surface is irradiated with a laser to decompose the layer of molecules at the surface without influencing the substrate. After decomposition the carbon atoms rearrange on the surface of the substrate to form a DLC film. The method of the invention may also be used to form other film, using a suitable molecule to produce the LB layer before irradiation.
