From Blue to White Luminescence in Cerium-Doped Aluminum Oxynitride: Electronic Structure and Local Chemistry Perspectives

Abstract

The excellent physical and chemical properties of aluminum oxynitride, Al(O)N, along with the tunable luminescence features of cerium ions (Ce) hold a promising future in white light sources based on chip technology. Manipulation of the light emission color from blue to green, to yellow and finally to white is demonstrated for the first time in Ce-doped Al(O)N thin films by tuning of the local structure, electronic structure and film thickness. Analysis of the electronic structure by electron energy loss spectroscopy (EELS) at the Ce-M4,5, Al-L2,3, O-K and N-K edges and photoluminescence spectroscopies highlight the essential role of oxygen and post-deposition annealing in changing the valence state of Ce ions from Ce 4+(optically inactive) to Ce 3+ (optically active) as well as the local field around Ce 3+ and, finally, in activating excitation pathways through generation of specific defect complexes in the oxynitride matrix.

Ultraviolet to infrared downshifting in Ce and Yb co-doped aluminum oxynitride thin films

“…Hence, producing AlN free from oxygen is very difficult. In addition, we evidenced in a previous work [23] that 7% of oxygen was required in order to activate the luminescence from Ce in an AlN matrix. Therefore, in the present study, for comparison purposes, all Yb doped samples, single and co-doped, have been prepared in Al(O)N hosts with 7% of oxygen.…”

Generation of White Light by Hybridization of Red–Green–Blue–Luminescent Materials

“…One approach involves the use of phosphors capable of producing white light similar to that of sunlight, and this involves the study of active agents that enhance the material photoluminescence (PL) in the long wavelength region . The second approach involves the development of single trichromatic white light–emitting materials, and it is mainly embodied by the doping of additional luminescent elements in the host luminescent material . In this case, however, controlling and maintaining an appropriate amount of each component to achieve the desired color balance is both challenging and complex.…”