Density Profiles in Sputtered Molybdenum Thin Films and Their Effects on Sodium Diffusion in Cu(InxGa1-x)Se2 Photovoltaics
Molybdenum (Mo) thin films were sputtered onto soda lime glass (SLG) substrates. The main variable in the deposition parameters, the argon (Ar) pressure p{sub Ar}, was varied in the range of 6-20 mTorr. Ex situ spectroscopic ellipsometry (SE) was performed to find out that the dielectric functions {var_epsilon} of the Mo films were strongly dependent on p{sub Ar}, indicating a consistent and significant decrease in the Mo film density {rho}{sub Mo} with increasing p{sub Ar}. This trend was confirmed by high-angle-annular-dark-field scanning transmission electron microscopy. {var_epsilon} of Mo was then found to be correlated with secondary ion mass spectroscopy profiles of Sodium (Na) in the Cu(In{sub x}Ga{sub 1-x})Se{sub 2} (CIGS) layer grown on top of Mo/SLG. Therefore, in situ optical diagnostics can be applied for process monitoring and optimization in the deposition of Mo for CIGS solar cells. Such capability is demonstrated with simulated optical transmission and reflectance of variously polarized incident light, using {var_epsilon} deduced from SE.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy Solar Energy Technologies Program
- DOE Contract Number:
- AC36-08GO28308
- OSTI ID:
- 1049621
- Resource Relation:
- Conference: [Proceedings] 37th IEEE Photovoltaic Specialists Conference (PVSC '11), 19-24 June 2011, Seattle, Washington; Related Information: See NREL/CP-5200-50701 for preprint
- Country of Publication:
- United States
- Language:
- English
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