A LAYER-WISE TOPOGRAPHIC STUDY OF A POLYMERIC LIGHT-EMITTING DIODE - INDIUM-TIN OXIDE POLY(2,3-DIPHENYL-P-PHENYLENE VINYLENE)/AG/

Scanning tunneling microscopy was used to characterize surface topogra phies relevant to polymeric light-emitting diodes (LEDs) whose active medium is a thin film of poly(2,3-diphenyl-p-phenylene vinylene) (DP-P PV). We performed a sequence of topographic studies on an indium-tin o xide (ITO) substrate, a DP-PPV film deposited on the ITO substrate, an d a Ag layer of thickness of about 100 Angstrom as evaporated on the D P-PPV film. ITO showed a granular structure, DP-PPV exhibited a fibrou s-like bundled structure, and the Ag layer formed clusters whose surfa ce roughness was comparable to the layer thickness. The different surf ace topographies were quantified by using the scaling of the height-he ight correlation functions.