In-situ resistance measurement during the growth of CuInGaSe2 films by multi-source evaporation

JinWoo Lee, Lei Chen, Uwa Obahiagbon, Chris Thompson, William N. Shafarman, Robert W. Birkmire Institute of Energy Conversion, University of Delaware, Newark, DE, United States

An in-situ resistance measurement technique is presented and used to monitor the evolution of the resistance of Cu(InGa)Se2 films during growth.  Both a 1-step and 3-stage growth processes are evaluated.  The resistance of the film is initially high and drops to ~100 Ω by the end of the deposition and during cooling increases to ~ 104 Ω.  When the bell jar is open and the samples exposed to air the resistance rapidly reduces to ~100 Ω.  The rapid change in resistances requires air or moisture and does not occur when exposed to N2, O2 or 5% H2 + Ar.  Since the resistance is a cross grain measurement and the change is so abrupt, the air exposure most likely affects the grain boundary chemistry.  The temperature dependence of both in-situ and ex-situ conductivities were compared and an estimate of the activation energy was the same for both the in-situ and ex-situ.