Synthesis and characterization of cesium iodide thin film, grown by RF-Magnetron sputtering

Abstract

To develop Cesium Iodide (CsI)-based optoelectronic devices, CsI thin films were deposited on Si (100) wafer substrate by RF-magnetron sputtering with varying sputtering power at 10, 30 and 50 watts. Along the 30 minutes of deposition with Ar gas, the operating pressure was controlled at the constant of 10 mTorr. The prepared CsI films were characterized for their crystallinities, morphologies, optical properties, and electrical properties through the grazing-incidence X-ray diffraction (GIXRD), field-emission scanning electron microscope (FE-SEM), photoluminescence (PL) and Hall Effect measurements. The GIXRD results show that the CsI films are formed in BCC structure with several crystallographic planes, especially (110) and (211) which have a crystal structure lattice constant of 4.5622 ± 0.0024 Å under a minimal tensile strain of -0.004%. The cross-sectional FE-SEM images exhibit that the thickness of the CsI thin films growth at a sputtering power of 50 W results in a dense crystalline arrangement. And the growth rate of CsI films is 400 nanometers per hour. The PL measurements indicate that the CsI films, by the excitation wavelength of 200 nm, have an emission light as multiple peaks in the 420-470 nm range. In addition, the Hall measurements show that the growth CsI films are p-type semiconductors with a carrier concentration 2.935x10¹⁵ cm^-3 and a resistivity of and 0.3735 kΩcm. All results of the film’s characterizations indicate that these CsI films, by the optimized sputtering technique are promising for the future development of radiation semiconductor detector.