CHEMICAL PURITY OF COPPER-GALLIUM THIN FILMS DEPOSITED FROM DIFFERENT SPUTTERING TARGETS

摘要

Thin films sputtered from two different CuGa (30 wt.% Ga) target qualities exhibit no differencesin oxygen content. The mean oxygen concentration level was 0.41 – 0.46 at.% in the thin films, which is about afactor of 2 higher than in the powder metallurgical sputtering target and about a factor of 200 higher than in thecast sputtering target, respectively. It can be concluded that residual oxygen in the sputtering chamber is the mainfactor determining the oxygen content in the sputtered thin films, and not the oxygen content in the sputteringtarget itself. On the other hand, metallic impurities like iron, nickel, and chromium in thin films clearly correlatewith the target composition and therefore mainly originate from the sputtering target. With powder metallurgicalmanufactured CuGa sputtering targets a consistent and homogeneous gallium distribution and thicknessuniformity within the sputtered thin films is achieved. Efficiency of solar cell samples with CuGa precursor thinfilms sputtered from a P/M target is more homogeneous than with thin films sputtered from a cast target.