As an example, in the early days of ALD, inorganic phosphors such as ZnS:M (M = Mn, Tb, Tm), SrS:M (M = Ce, Cu, Tb, Pb), CaS:M (M = Eu, Ce, Tb, Pb), were extensively researched for the development of thin film electroluminescent displays (TFEL). The need for higher material quality and versatility in the fabrication of optoelectronic devices was one of the main motivations that lead to the birth and development of atomic layer deposition (ALD). 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. 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.
Thus, the inclusion of O 2− ions by ALD in a CaS:Eu phosphor results in the blue-shift of 21.2 nm. It was found that the emission wavelength of CaS:EuO was 625.8 nm whereas CaS:Eu was 647 nm. We study structural and photoluminescent properties of two different ALD deposited Eu doped CaS thin films: Eu(thd) 3 which reacted with H 2S forming CaS:Eu phosphor, or with O 3 originating a CaS:EuO phosphor. 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. This is especially relevant for inorganic luminescent materials where slight changes in the vicinity of the luminescent centers may originate new emission properties. Consequently, novel material characteristics may arise with new functions for applications. 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. Atomic layer deposition (ALD) technology has unlocked new ways of manipulating the growth of inorganic materials.