Technological, structural and morphological aspects of screen-printed ITO used in ITO/Si type structure

Abstract

ITO thin films (In₂O₃(Sn)) have been prepared by a screen-printing technique (SPT). Deposits obtained from a paste (ESL No.3050) on a Pyrex substrate are fired in air at approximately 600 degrees C. Layers thus realized are found to be polycrystalline. Their crystalline structure has been identified by comparing their X-ray diagram with that of pure In₂O₃ (ASTM). Then the crystalline texture of the films is studied as a function of fabrication parameters. X-ray diffraction pattern analysis shows that dopant tin atoms can exist outside the In₂O₃ matrix in an Sn₃O₄ minority phase. Surface transmission electron microscopy (TEM) of ITO grown on a silicon substrate shows that screen-printed ITO is granular and porous. The average grain size measured from surface TEM micrographs is about 120 AA. Cross section TEM observations of the ITO/Si structure confirm that screen-printed ITO is granular and porous. Growth of an expected SiO₂ interfacial layer has been pointed out. It was found that the SiO₂ interfacial thickness is due to firing temperature and ITO porosities which facilitate oxygen diffusion.