AVS 51st International Symposium
    Thin Films Thursday Sessions
       Session TF-ThA

Paper TF-ThA2
Formation of Chalcogen Containing Plasmas and Their Use in Synthesis of Photovoltaic Absorber Layers

Thursday, November 18, 2004, 2:20 pm, Room 303C

Session: Photovoltaic Thin Films
Presenter: S. Kosaraju, Colorado School of Mines
Authors: S. Kosaraju, Colorado School of Mines
C.A. Wolden, Colorado school of Mines
R. Ingrid, ITN Energy Systems, Inc.
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The synthesis of copper chalcopyrite solar absorbers requires high temperature and excess chalcogen due to low chalcogen reactivity. This paper describes work aimed at addressing these issues through plasma processing. An inductively coupled plasma (ICP) source was used to activate both sulfur and selenium vapors into high-energy atomic and radical species. Stable ICP discharges were achieved with both sulfur and selenium vapors using argon as a carrier gas. ICP processing configurations are described for both a flowtube geometry used for metal selenization as well as for incorporation into a high vacuum co-evaporation environment. Actinometry was employed to measure the flux of chalcogen vapors from solid sources as a function of source temperature and the RF power. The potential of this approach was demonstrated by converting indium and copper/indium/gallium films to chalcopyrites using the ICP source. It is shown that indium is readily converted to In@sub 2@Se@sub 3@ using argon/selenium plasma at room temperature. Similarly, Cu/In/Ga precursor thin films on a stainless steel substrate were exposed to plasma-activated selenium at 300@super o@C. The foils were converted into ternary and quandary chalcopyrite compounds, and no crystalline binary phases (i.e. In@sub 2@Se@sub 3@, CuSe) were observed. Films were additionally characterized by scanning electron microscopy and energy dispersive spectroscopy.