Abstract
Atomic layer deposition (ALD) technology has unlocked new ways of manipulating the growth of inorganic materials. The fine control at the atomic level allowed by ALD technology creates the perfect conditions for the inclusion of new cationic or anionic elements of the already-known materials. Consequently, novel material characteristics may arise with new functions for applications. This is especially relevant for inorganic luminescent materials where slight changes in the vicinity of the luminescent centers may originate new emission properties. Here, we studied the luminescent properties of CaS:Eu by introducing europium with oxygen ions by ALD, resulting in a novel CaS:EuO thin film. We study structural and photoluminescent properties of two different ALD deposited Eu doped CaS thin films: Eu(thd)3 which reacted with H2S forming CaS:Eu phosphor, or with O3 originating a CaS:EuO phosphor. It was found that the emission wavelength of CaS:EuO was 625.8 nm whereas CaS:Eu was 647 nm. Thus, the inclusion of O2− ions by ALD in a CaS:Eu phosphor results in the blue-shift of 21.2 nm. Our results show that ALD can be an effective way to introduce additional elements (e.g., anionic elements) to engineer the physical properties (e.g., inorganic phosphor emissions) for photonics and optoelectronics.
Highlights
The development of new luminescent materials and optoelectronic devices such as lamps, displays, lasers, solar cells and photodetectors, relies strongly on the flexibility of the used fabrication technique
Two samples of Eu doped calcium sulfide doped with europium (CaS) phosphors were grown by atomic layer deposition (ALD)
X-ray diffraction (XRD) analysis shows the polycrystalline nature of the phosphor layers with a slight difference in the lattice dimension and level of crystallinity between the samples
Summary
The development of new luminescent materials and optoelectronic devices such as lamps, displays, lasers, solar cells and photodetectors, relies strongly on the flexibility of the used fabrication technique. The meticulous inclusion of dopants can be conducted in a single fabrication run, while the host material is being grown These effects are interesting regarding the doping level control of thin film materials. They are appropriate for the fabrication of inorganic phosphors, where the doping element acts as a luminescent center. The distance is restrained by the steric hindrance effect of the ligands [5,6,7,8] With this distribution engineering procedure, higher doping concentrations can be achieved in comparison to other fabrication techniques [7], which may reflect in higher luminance values
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