The post-growth treatment of PbI2 thick films as an attempt to suppress the films surface effect

PbI2 thick films were coated with different materials (Parylene C, HumiSeal and PbBr2) in order to improve the films' surface properties. It was shown that Parylene C and HumiSeal coating decreased the dark current of PbI2 films and changed the shape of the I-V and I-t curves. X-ray-irradiated films demonstrated a significant increase in signal-to-noise ratio due to a decrease in the dark current, a slightly increased rise time, and a decreased decay time compared to non-coated PbI2 films. In addition, Pd atoms from the electrical contact easily penetrated the Parylene C protective layer over a period of 1-2 h. The Pd diffusion coefficient and Parylene C dark resistivity estimated from these experiments were DPd=(3.6±2.1)×10−13 cm2/s and ρParylene C=(130±70) T Ω cm, respectively. Only the PbBr2 coating led to decreased rise and decay times compared to non-coated PbI2 films.