The LB method is usually used to fabricate highly ordered ultrathin films of various organic sub-stance based on amphiphyllic molecules.Now the LB technique is used to made some of oxide thin films.The metal carboxylate films were constructed by LB technique and used as precursors.The organic component was removed to form metal oxide films by directly heating the LB films or exposing the LB films to ultraviolet light and reactive oxygen.In this paper we constructed Eu-doped yttrium arachidate LB film us-ing YCl

3

and EuCl

3

aqueous as subphase.The π-A isotherm indicated that the arachidic acid had good film-forming ability on the YC13 aqueous subphase

the monolayer collapse pressure was about 53mN/m.The monolayer on the surface of YCl3 aqueous was successfully transferred onto different substrates such as mica

silicon wafer

quartz and so on.The AFM image exhibited the uniformity of the transferred mono-layer.The IR spectrum and the X-ray photoelectron spectrum confirmed that the arachidic acid reacted with YCl3 and formed yttrium arachidate.From the emission spectrum

the luminescence of Eu

3+

was ob-served.These results indicated that the Eu-doped yttrium arachidate LB film was constructed successfully and some treatment could be completed to make Y

2

O

3

Eu thin film.