Abstract: There is provided a flat electrode for a surface light source, in which a conductive electrode is formed in a fine strip-shaped pattern on a plane. The flat electrode may comprise a base layer, an electrode pattern formed on the base layer, and a protection layer formed on the electrode pattern. There is also provided an ultra thin surface light source device which comprises: a first substrate and a second substrate which are spaced apart from each other at a predetermined interval; and a first surface electrode formed on the first substrate, and a second surface electrode formed on the second substrate. The surface light source device may further comprise a medium layer formed in at least one of spaces between the first substrate and the first surface electrode and between the second substrate and the second surface electrode.

Abstract: There are provided an yttrium oxide composition having particle size of 25 nm or less, a method of preparing the same and a method of forming an yttrium oxide layer using the same. The yttrium oxide composition is prepared by dissolving an yttrium salt into a solvent to prepare an yttrium salt solution, and adding a basic compound to the yttrium salt solution to adjust a pH value to a range of 3.7 to 7. The yttrium oxide composition can form an yttrium oxide layer having improved properties since the composition has particle size of 25 nm or less and uniform particle distribution.