Preparation Of KY(WO₄)₂ Film By Layer-by-layer Dipping Method And Its Film-forming Mechanism

In recent 10 years,potassium yttrium tungstate?KY?WO₄?₂?has been widelystudied and applied as a kind of excellent substrate material.In this paper,Eu:KY?WO₄?₂ thin film was prepared by the layer by layer impregnation method.The phase,morphology,roughness and fluorescence properties of samples were studied by XRD,SEM,AFM and fluorescence spectrometer.Film forming mechanism of Eu:KY?WO₄?₂ thin film was studied.The result follows:1.Quartz glass based SDBS?CTAB?/KY?WO₄?₂ films were prepared by layer-by-layer impregnation method.The effects of substrate cleaning methods,number of coating layers,surfactants,and heat treatment conditions on the films were investigated.The results showed that the films prepared by caustic washing had higher density,the films showed preferential growth of?220?and?040?crystal faces,and the acetone alcohol cleaning film had low density;the effect was best when the number of coating layers was 10,SDBS?CTAB?/KY?WO₄?₂ films had good crystallinity and crystal face development;Surfactant SDBS promoted?042?and?331?growth,CTAB promoted?220?crystal growth,the crystal grain of KY?WO₄?₂ thin films were a polyhedron with straight edges and sharp edges.It had good dispersibility and uniform particle size distribution.The crystallinity of SDBS?CTAB?/KY?WO₄?₂ films increased with the increase of temperature and holding time during the heat-treatment temperature of 600°C to 800°C.SEM characterization showed that the films were covered with the substrate surface and the density was high.SDBS?CTAB?/KY?WO₄?₂ films were greatly affected by the heating rate.When the heating rate was decreased,the crystallinity of the film grains increased,the film grown on the substrate as islands,the pores of the film gradually decreased,and the density gradually increased.2.Eu:KY?WO₄?₂ thin films were prepared by layer-by-layer impregnation and their fluorescence properties were studied.The results showed that:KY?WO₄?₂ doped Eu³⁺films could emit 614nm under 262nm excitation?⁵D₀?⁷F₂?red light.The fluorescencelifetimeof614nmfluorescencewavelengthwere0.98ms?SDBS/KY?WO₄?₂ film?and 0.84ms?CTAB/KY?WO₄?₂ film?.With the increasing of doping concentration of Eu³⁺ions,the characteristic peaks of XRD curves of SDBS?CTAB?/KY?WO₄?₂ films showed blue shift.The fluorescence intensity increased with the increase of Eu³⁺ion doping concentration.When the Eu³⁺doping concentrationreachedthe15at%?SDBS/KY?WO₄?₂film?andthe20at%?CTAB/KY?WO₄?₂ film?,the fluorescence intensity reached the highest.Then the doping concentration of Eu³⁺continued to increase and the fluorescence intensity decreased due to the fluorescence quenching effect.With the increase of the number of coating layers,the fluorescence intensity increased.When the number of coating layers was three,the fluorescence intensity reached the highest point,and continued to increase the number of coating layers,the fluorescence intensity tended to stabilize or even weaken.When the holding time was less than 5 h,the fluorescence intensity gradually increased with the increase of the holding time.And the fluorescence intensity reached the highest value when the holding time was 5 h,and then continued to prolong the holding time,the fluorescence intensity showed a trend of weakening.3.The SDBS/KY?WO₄?₂ thin film crystal on the Si substrate had preferential growth on the plane of?31^—2?,?042?and?33^—4?.The particle size was in the range of800-1000nm,and the density of the film was not high on the surface of silicon wafer.This was mainly due to the low surface smoothness and surface adhesion of the silicon wafer.The CTAB/KY?WO₄?₂ thin film crystal on the silicon substrate was preferred to grow on the crystal plane of?31^—2?,?040?and?20^—4?,which was somewhat different from that of the anionic surfactant SDBS.KY?WO₄?₂ film particles were polyhedral structure.The crystallinity of SDBS/KY?WO₄?₂ films was better.The particle size of SDBS/KY?WO₄?₂ films was in the range of 800-1000nm.The particle size of CTAB/KY?WO₄?₂ film was in the range of 200-800nm.The density of thin films on the surface of silicon wafer was low.4.There was one growth model in the process of SDBS?CTAB?/KY?WO₄?₂thin film growth,which was island growth model.The process of growth was basically the same at different stages.At first,the thin films were made up of short fibrous KYW,and then the grains were fused into polygonal island structures.Finally,these large island structures were combined to form blocky films.