Inverse Piezoelectric In-situ Strain Regulation Of Ferroelectric/upconversion Luminescent Films

Rare-earth upconversion photoluminescence?UPL?materials have drawn considerable attention owing to their wide applications in biomedicine,solid state lasers and solar cell.How to realize the modulation and enhancement of the UPL effects attracted continuous interest in the photoluminescence field.To date,the modulation of UPL in phosphors was generally achieved through a conventional chemical approach.However,the modulation based on the traditional chemical routine was usually static,which was difficult for the researchers to learn about the underlying mechanism for the dynamic UPL process.In present work,we propose an alternative routine to realize the modulation of the UPL property through the in-situ strain which was generated by high-performance relaxor ferroelectric 0.7Pb?Mg1/3Nb2/3?O₃-0.3PbTiO₃?PMN-PT,PMNT?single crystals.Through the utilization of the pulsed laser deposition?PLD?method,high-quality ferroelectric/photoluminescence film was grown on the PMN-PT substrate using the SrRuO₃?SRO?thin film as the conducting layer.The influence of the fabrication parameters on the phase structure,ferroelectric domain structure,morphology along with the electrical and UPL properties were systematically studied.The details were as follows,1.For the fabrication of the ferroelectric/photoluminescence system,the ferroelectric BaTiO₃?BTO?system was selected as the host material.Single Er³⁺-doped,Er³⁺/Yb³⁺ co-doped luminous systems were designed and fabricated.The influence of the sintering temperature on the phase structure,density,and the UPL properties was studied.Results indicated that the A-site Er³⁺/Yb³⁺ co-doped system exhibited superior UPL properties compared to the Er³⁺-doped and B-site Er³⁺/Yb³⁺ co-doped system.2.Based on the PMN-PT single crystal substrate,the bottom electrode SRO thin film was first deposited by PLD.The influence of the deposition temperature,oxygen and time on the morphology and electric resistance was studied.Optimized SRO thin films exhibited low square resistance of 60 ? and the RMS roughness of the film was only 0.5 nm.Furthermore,BaTiO₃?Yb/Er?epitaxial thin film was fabricated by PLD on the SRO-electroded PMN-PT substrate.The optimized BaTiO₃?Yb/Er?thin film exhibited low RMS roughness of ⁰.9 nm.The corresponding remnant polarization and coercive field were 10 ?C/cm2 and 5 kV/mm,respectively.The local poling experiments indicated complete polarization switching under 10 V in the as-grown thin film.Also strong UPL output was detected.3.Based on the piezoelectric effect of PMN-PT single crystal substrate,an improvement of about 10% was observed in the UPL intensity of BaTiO₃?Yb/Er?thin film after the substrate was poled under 0.5 kV/mm.When an in situ electric field of 0-0.5 kV/mm was applied to the substrate,repeatable UPL intensity enhancement of about 15% could be detected in BaTiO₃?Yb/Er?thin film.After the field removal,the UPL intensity returned to the original value.These results indicated that in-situ piezoelectric strain can provide an effective routine to modulate the UPL intensity and the present work would provide an alternative way to design new UPL devices.