A. Yousif

The role of growth atmosphere on the structural and optical quality of defect free ZnO films for strong ultraviolet emission

Highly c-axis oriented wurtzite structured ZnO thin films were deposited on silicon substrates using pulsed laser deposition (PLD) by ablating a ZnO target in different atmospheres, including vacuum, argon and oxygen in the deposition chamber. The stress in the films was shown to vary from −3.83 to −0.03 GPa as a function of the chamber atmosphere. The minimum compressive stress (−0.03 GPa) was observed for the oxygen atmosphere. X-ray photoelectron spectroscopy data indicated that the O1s peak consists of three components designated as O1 (due to ZnO), O2 (due to defects) and O3 (due to adsorbed species). A small defect level emission was obtained in the luminescence spectra of the ZnO film deposited in the oxygen atmosphere, while strong ultraviolet (UV) emission was observed for the ZnO films deposited in the vacuum and argon atmosphere. These PLD grown ZnO thin films have the potential to be used as sources of UV radiation in light emitting devices.

Ultra-broadband luminescent from a Bi doped CaO matrix

CaO:Bi phosphor powders were successfully synthesized by the sol–gel combustion method. Post heat treatment led to the enrichment of the Ca2+ site with multiple Bi centers. These centers were responsible for the change in the ultra-broadband cathodoluminescence (CL) emission as a function of different electron beam currents/beam voltages. The CaO phase formation and the presence of the enrichment of Bi was confirmed by using the X-ray diffraction and X-ray photoelectron spectroscopy techniques. The thermoluminescence afterglow spectra for the samples annealed at 800 °C and 1200 °C were strongly modified for the CaO and the presence of the multiple Bi centers. Of particular interest was that the ultra-broadband CL may have potential applications in inorganic single-emitting components that produce various colours under different beam currents/beam voltages or in a variety of optical devices if it can be better controlled.

Photoluminescence and thermoluminescence properties of Y3(Al,Ga)5O12:Tb3+ phosphor

A comparative study of the structural, photoluminescence (PL) and thermoluminescence (TL) properties of Y3(Al,Ga)5O12:Tb3+ phosphor powder was performed. The scanning electron microscope images showed that the phosphor particles were agglomerated and irregular in shape. The bigger particles consisted of smaller spherically shaped agglomerated particles ranging in size between 0.5 and 1 μm. The UV–VUV synchrotron radiation was used to study the luminescence properties of the phosphor. The TL study was performed after the sample was irradiated by γ-rays obtained from a 60Co target in the dose range of 10–50 Gy. The effect of heating rate on the TL glow curves and trapping parameters was also calculated. The correlation between PL and TL was explored.