Real time spectroscopic ellipsometry studies of ultrathin CIGS films deposited by 1-stage, 2-stage and 3-stage co-evaporation processes

Ultrathin Cu(In,Ga)Se₂ (CIGS) films were deposited by 1-stage, 2-stage and 3-stage co-evaporation processes. In situ, real time spectroscopic ellipsometry (RTSE) was used to study the growth dynamics of the ultrathin CIGS films. Time dependent surface roughness layer (d_s) and bulk layer (d_b) thicknesses were extracted in the early stages of film growth. Exsitu spectroscopic ellipsometry was used to characterize the fundamental optical constants of these films. Other ex-situ measurements were performed on each ultrathin layer to corroborate composition, thickness, grain size and surface roughness thickness obtained by the SE measurements.