Sol-gel Soft Lithography Research Articles

Plasma Enhanced Electrochemical Preparation for Photo-Luminescent Metal Oxide Films on Al Foil

Electrochemical coating technologies of metal surface have been widely used for decades in various industries, because it provides the thick and anti-corrosive films with a simple and cheap process [1]. Especially, plasma electrolytic oxidation (PEO), which is a high electrical power-induced technology, has much attention in recent years due to their excellent film property. The PEO produces adherent ceramic-like coatings, which are beneficial to enhance the corrosion and wear resistance, so the oxidized film can be applied in many industrial fields [2-4]. During PEO process, a high–voltage discharge zone is generated with spark or arc plasma micro-discharge, and the thick ceramic coating is directly formed on the surface of metals together with elements in the electrolyte. At the discharge zone, the extreme environments with high temperature and pressure are generated, and estimated temperature is around 8000 K at a hot core and 1800 K at a cold circumferential area [5]. In this study, we applied the plasma discharge phenomenon in PEO process to generate the photo-luminescent oxide film by adding the rare-earth ions in the electrolytes, and the white light emitting oxide film was successfully formed on aluminum foil. So far, the luminescent film was fabricated by screen printing technique, combustion CVD, spin coating, sol-gel soft lithography, and radio-frequency magnetron sputtering, but those kinds of phosphor films showed many problems such as poor uniformity of film thickness and low adhesion to the substrate [6-8]. In case of PEO process, the rare-earth ions are directly incorporated during oxidation process, so well adhesive luminescent films can be obtained. In order to prepare photo-luminescent oxide film, the plasma electrolytic oxidation of Al foil was conducted in rare-earth ion containing base electrolyte with constant current density of 3 A/dm2 using DC pulse power supply. Various electrolytes and rare earth ions were employed and their effects on the photoluminescence properties of the obtained films were examined. To find out the correlation of photo-luminescence and micro arc generation in early stage, cathode-luminescence properties were investigated in the films formed around break-down voltage with SEM images. When europium was present in the electrolyte, a white light emitting ceramic-like film covering from NUV to visible was formed on aluminum foil (Fig. 1). The film was mainly composed of γ-Al2O3, and the emission spectrum consisted of two emission peaks centered at 420 nm and 500 nm with a broad FWHM (~197.6 nm). The origin of these emission peaks will be discussed in this presentation. In addition, the effects of electrolyte composition and rare-earth ions on the phase content and photoluminescence properties of the Al2O3films will be presented.Reference[1] G. Helen Annal Therese and P. Vishnu Kamath, Chem. Mater.,12, 1195 (2000)[2] A. Kuhn, Met. Finish, 101, 44 (2003)[3] X. Nie, E. I. Meletis, J. C. Jiang, A. Leyland, A. L. Yerokhin, and A. Matthews, Surf. Coat. Technol., 149, 245 (2002)[4] C. Blawert, W. Dietzel, E. Ghali, and G. Song, Adv. Eng. Mater., 8, 511 (2006)[5] A. L. Yerokhin, X. Nie, A. Leyland, A. Matthews, and S. J. Dowey, Surf. Coat. Technol., 122, 73 (1999)[6] K.Y. Jung, Y.C. Kang, Mater. Lett, 58, 2161 (2004)[7] Z.T. Kang, Y. Liu, B.K. Wagner, R. Gilstrap, M. Liu, C.J. Summers, J. Lumin., 121, 595 (2006)[8] W.-H. Chao, R.-J. Wu, T.-B. Wu, J. Alloys Compd., 506, 98 (2010)

Fabrication, patterning and luminescence properties of X 2–Y 2SiO 5:A (A=Eu 3+, Tb 3+, Ce 3+) phosphor films via sol–gel soft lithography

X 2–Y 2SiO 5:A (A=Eu 3+, Tb 3+, Ce 3+) phosphor films and their patterning were fabricated by a sol–gel process combined with a soft lithography. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM), scanning electron microscopy (SEM) optical microscopy and photoluminescence (PL) were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 900 °C with X 1–Y 2SiO 5, which transformed completely to X 2–Y 2SiO 5 at 1250 °C. Patterned thin films with different band widths (5 μm spaced by 5 μm and 16 μm spaced by 24 μm) were obtained by a soft lithography technique (micromoulding in capillaries, MIMIC). The SEM and AFM study revealed that the nonpatterned phosphor films were uniform and crack free, and the films mainly consisted of closely packed grains with an average size of 350 nm. The doped rare earth ions (A) showed their characteristic emissions in X 2–Y 2SiO 5 phosphor films, i.e., 5D 0– 7F J ( J=0,1,2,3,4) for Eu 3+, 5D 3, 4– 7F J ( J=6,5,4,3) for Tb 3+ and 5d ( 2D)–4f ( 2F 2/5, 2/7) for Ce 3+, respectively. The optimum doping concentrations for Eu 3+, Tb 3+ were determined to be 13 and 8 mol% of Y 3+ in X 2–Y 2SiO 5 films, respectively.

Patterning and luminescent properties of nanocrystalline Y 2O 3:Eu 3+ phosphor films by sol–gel soft lithography

Nanocrystalline Y 2O 3:Eu 3+ phosphor films and their patterning were fabricated by a Pechini sol–gel process combined with a soft lithography. X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG–DTA), atomic force microscopy (AFM), optical microscopy, UV/vis transmission and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 500 °C and the crystallinity increased with the elevation of annealing temperatures. Uniform and crack free non-patterned phosphor films were obtained, which mainly consisted of grains with an average size of 70 nm. Using micro-molding in capillaries technique, we obtained homogeneous and defects-free patterned gel and crystalline phosphor films with different stripe widths (5, 10, 20 and 50 μm). Significant shrinkage (50%) was observed in the patterned films during the heat treatment process. The doped Eu 3+ showed its characteristic emission in crystalline Y 2O 3 phosphor films due to an efficient energy transfer from Y 2O 3 host to them. Both the lifetimes and PL intensity of the Eu 3+ increased with increasing the annealing temperature from 500 to 900 °C, and the optimum concentrations for Eu 3+ were determined to be 5 mol%.

Preparation, patterning and luminescent properties of oxyapatite La9.33(SiO6)4O2:A(A = Eu3+, Tb3+, Ce3+)phosphor films by sol–gel soft lithography

Silicate oxyapatite La9.33(SiO6)4O2:A(A = Eu3+,Tb3+ and/orCe3+)phosphor films and their patterning were fabricated by a sol–gel process combinedwith soft lithography. X-ray diffraction(XRD), Fourier transform infraredspectroscopy, atomic force microscopy, optical microscopy and photoluminescencespectra, as well as lifetimes, were used to characterize the resulting films. The resultsof XRD indicated that the films began to crystallize at 800 °Cand the crystallinity increased with the increase in annealing temperatures.Transparent nonpatterned phosphor films were uniform and crack-free, whichmainly consisted of rodlike grains with a size between 150 and 210 nm.Patterned thin films with different bandwidths(20, 50µm) wereobtained by the micromoulding in capillaries technique. The doped rare earth ions(Eu3+, Tb3+ andCe3+)showed their characteristic emission in crystalline La9.33(SiO6)4O2phosphor films, i.e. Eu3+5D0 −−7FJ(J = 0, 1, 2, 3, 4), Tb3+5D3,4 −−7FJ(J = 3, 4, 5, 6)and Ce3+ 5d(2D)−− 4f(2F2/5,2F2/7)emissions, respectively. Both the lifetimes and PL intensity of the Eu3+, Tb3+ ionsincreased with increasing annealing temperature from 800 to 1100 °C,and the optimum concentrations for Eu3+, Tb3+were determined to be 9 and 7 mol% of La3+ in La9.33(SiO6)4O2films, respectively. An energy transfer from Ce3+ toTb3+was observed in the La9.33(SiO6)4O2:Ce,Tb phosphor films, and the energy transfer efficiency was estimated as a function of Tb3+concentration.

Patterning and optical properties rhodamine B-doped organic–inorganic silica films fabricated by sol–gel soft lithography

Rhodamine B (RB)-doped organic–inorganic silica films and their patterning were fabricated by a sol–gel process combined with a soft lithography. The resulted film samples were characterized by atomic force microscope (AFM), optical microscope and UV/Vis absorption and photoluminescence excitation and emission spectra. The effects of the concentration of the RB dye and heat treatment temperature on the optical properties of the hybrid silica films have been studied. Four kinds of patterning structures with film line widths of 5, 10, 20 and 50 μm have been obtained by micromolding in capillaries by a soft lithography technique. The RB-doped hybrid silica films present a red color, with an excitation and emission bands around 564 and 585 nm, respectively. With increasing the RB concentration, the emission intensity of the RB-doped hybrid silica films increases and the emission maximum presents a red shift. The emission intensity of the films decreases with increasing the heat treatment temperatures.