X-ray luminescence and characteristics of potassium-doped cesium iodide film

This study delves into the structural and luminescent properties of un-doped and potassium (K) doped cesium iodide (CsI) thin films fabricated by thermal vacuum co-evaporation. These films were characterized by aspects of X-ray diffraction (XRD) patterns, field emission scanning electron microscopy (FE-SEM) images, energy-dispersive X-ray spectroscopy (EDS), X-ray luminescence spectra, and X-ray photoelectron spectroscopy (XPS). The predominant crystal orientation changed from the (200) plane to the (110) one after K-doping. Upon X-ray excitation, the defect-related luminescence spectra of K-doped CsI films unveiled a broad peak from 380 to 600 nm in the region. Notably, the sample doped with 2 wt% of KI exhibited the highest luminescence efficiency. Finally, XPS analysis disclosed the binding energies associated with Cs–I and multiple-I ions. This observation suggested the existence of crystal defects, including F-, H-, and V_k-centers, in addition to the conventional CsI ionic crystal structure.