Quantum confinement effect and size-dependent photoluminescence in laser ablated ultra-thin GZO films

The structural, morphological, and optical characteristics of GZO ultra-thin films were investigated using XRD (X-ray diffraction), FE-SEM (field emission electron microscopy), in situ EDS (Energy Dispersive X-ray) spectroscopy, UV-VIS-IR spectroscopy and photoluminescence spectroscopy (PL) respectively. Morphological analysis reveals the noodle, seed and particle like structure of GZO for GaN, sapphire and Si substrates respectively with average grain size ranging from 5 to 20 nm. An effective mass model (EM-Model) for particle in a cylindrical wave function of e-h pair was correlated with experimental results. The reduction in FWHM value (from 31 nm to 13 nm) of NBE (near-band-edge) emission peak and enhanced NBE intensity have been achieved with small grain size. Blue shift in optical band gap is explained in term of grain radius by EM-model. Improved optical and structural properties were found in relation with quantum confinement effect. The current study states that grain size plays vital role in order to tailor optical properties of GZO thin films.