Real time spectroscopic ellipsometry of thin film CdTe deposition by magnetron sputtering for photovoltaic applications

Real time spectroscopic ellipsometry based on rotating-compensator modulation and multichannel detection has been implemented to characterize CdTe deposition for polycrystalline thin film photovoltaic applications. The CdTe film measured and analyzed in detail in this study was prepared by magnetron sputtering onto a native oxide-covered crystalline silicon substrate. Key observations from this study include: (i) monolayer-level surface roughness thickness (∼3 Å) at the onset of bulk layer formation and during subsequent growth to ∼50 Å; (ii) gradual development of a lower density bulk layer after ∼13000 Å of CdTe thickness; and (iii) much broader above-gap critical points in the dielectric function for thin film polycrystalline CdTe compared to the single crystal.