Preparation And Patterning Of Rare Earth Luminescent Films

With the increasing development in miniaturization and microfabrication of devices, thepreparation of thin films have been one of the most active research areas in recent yearsbecause of the size-/thickness-dependent properties of materials and their potential for a broadrange of applications. As an important aspect, thin films that exhibit unique propertiescompared to bulk materials, are fundamental for electronic, displays, sensors, opticalequipment, and meet the need for scaling devices to small sizes, and are therefore attractiveboth in theory and practice.Microcontact printing （μCP）, one of soft lithography methods, is an effective techniquefor forming patterned films with micro-and nanoscales. This process utilizes a PDMSelastomeric mold as the stamp to create heterogeneous pattern on quartz substrates firstly andthen combined with a Pechini-type sol-gel process to selectively deposit the luminescentphosphors on hydrophilic regions, in which precursor solutions are employed as ink.These obtained ordered luminescent patterns samples were revealed by X-ray diffraction（XRD）, field emission scanning electron microscopy （FE-SEM）, optical microscope and soon. Additionally, photoluminescence （PL） and cathodoluminescence （CL） spectra werecarried out to characterize the luminescence properties of the patterned samples. Underultraviolet excitation and low-voltage electron beam excitation, the doped rare earth ionsshow their characteristic emission in the obtained rare earth luminescent materials.Ordered arrays of luminescent GdVO₄:Ln (Ln=Eu³⁺, Dy³⁺, Sm³⁺) films with dotpatterns have been successfully fabricated via microcontact printing （μCP） method andsol-gel process. Upon UV-light or electron-beam irradiation, the rare earth ions Eu³⁺, Dy³⁺and Sm³⁺in the crystalline GdVO₄host show their characteristic transitions dominated by⁵D₀-⁷F₂,⁴F_9/2-⁶H_13/2and⁴G_5/2-⁶H_7/2, respectively.Gd₂（WO₄）₃doped with Eu³⁺or Tb³⁺thin phosphor films with dot patterns have beenprepared by a combinational method of sol-gel process and microcontact printing. Underultraviolet excitation and low-voltage electron beams excitation, the Gd₂（WO₄）₃:Eu³⁺samplesexhibit a strong red emission arising from Eu³⁺(⁵D_0,1,2–⁷F_1,2) transitions, while theGd₂（WO₄）₃:Tb³⁺samples show the green emission coming from the characteristic emission ofTb³⁺corresponding to⁵D₄–⁷F_6,5,4,3transitions. The results show that the patterning of rare earth–doped phosphors through combiningmicrocontact printing with a Pechini-type sol-gel route has potential for field emissiondisplays （FEDs） applications.