MODIFICATION OF SURFACE AND BANDGAP ON SB-INCORPORATED CUINSE2 THIN-FILMS BY (NH4)(2)S-X SULFURIZATION

In this work, we study the effect of the addition of antimony, and che mical sulfurization of CuInSe2 thin films with (NH4)(2)S-x solution. C uInSe2 thin films were deposited by the molecular beam deposition meth od and trace amounts of antimony have been added. The antimony, detect ed by scanning Auger electron microscopy, reacts with the bi-or tri-co ordinated In to saturate the dangling bonds on the growing surface as surfactants. During (NH4)(2)S-x sulfurization, the sulfur atoms enter the thin films through a pathway which is created by the replacement o f antimony atoms segregated on the thin film surface. A portion of the selenide film is transformed into an alloy of CuInSe2 and CuInS2 on t he grain surface. Significant amounts of sulfur (35%) distributed thro ughout the thin film of CuInSe2 under an antimony source temperature o f 510 degrees C in the film growth was shown from the Anger electron d epth profile, and an increase of energy bandgap up to 1.3 eV as determ ined from optical absorption measurements. The chemical reactions are justified from thermodynamic considerations. (C) 1998 Elsevier Science B.V.