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Aleksandra Turković Ruđer Bošković Institute

Determination of grain sizes and porosity in nanophase vanadium oxide and V/Ce oxide with GISAXS and GIXR. Aleksandra Turković Ruđer Bošković Institute Division of Materials Physics Laboratory for semiconductors Bijenička 54, P.O.Box 180 HR-10002 Zagreb, Croatia,. 1.

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Aleksandra Turković Ruđer Bošković Institute

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  1. Determination of grain sizes and porosity in nanophase vanadium oxide and V/Ce oxide with GISAXS and GIXR Aleksandra Turković Ruđer Bošković Institute Division of Materials Physics Laboratory for semiconductors Bijenička 54, P.O.Box 180 HR-10002 Zagreb, Croatia, 1

  2. Morphology of porous nanocrystalline V/Ce films • Application in optical electronics • Experiment at synchrotron ELETTRA, Trieste • GIXR, GISAXS methods of measurements 2

  3. Small-angle X-ray scattering • Austrian SAXS beamline at ELETTRA • Grazing-incidence geometry • Samples are thin films on glass substrate • Electrical, optical experiments - cooperation with Slovenia http://www.elettra.trieste.it/ • ... http://www.irb.hr/ • ... http://www.ki.si/ • ... http://www.ijs.si/ FOR MORE INFORMATION 3

  4. SAXS-beamline • SAXS method used • is not destructive • Samples remain in the form (film on the glass substrate) • in which they are often used in functional applications of this material • As glass substrates strongly absorb X-ray radiation • the standard transmission geometry mode of measurement was replaced by the reflection geometry mode. GISAXS, GIXR! 4

  5. First team from Croatia on SAXS in 1997. • Resources allocated to the project:”SAXS study of grain sizes and porosity in nanophase TiO2” • people:A.Turković(leader), P.Dubček, M.Lučić Lavčević, B.Etlinger and O.Milat • equipment: SAXS beamline • locations: Basovizza near Trieste, Italy • support from synchrotron and Ministry of Science and Technology of Croatia • three papers in international journals till the end of 1997. 5

  6. Second team from Croatia on SAXS in 1998. • Resources allocated to project:”SAXS, study of grain sizes and porosity in TiO2, CeO2 and CeO2/SnO2 nanophases” • people:A.Turković(leader), P.Dubček, M.Lučić Lavčević and O.Milat • equipment: SAXS beamline • locations: Basovizza near Trieste, Italy • support: Ministry of Science and Technology of Croatia • three papers in international journals till the end of 1998 and one Ph.D.thesis M.Lučić Lavčević. 6

  7. SAXS • m=/2D • m= maximal angle at SAXS • = wavelength of x-rays • D= diameter of largest grain • General formula for intensity of scattering: • Ī(s)= 2I(ŝ)I2 • ŝ =(ŝ-ŝ0)/  - vector in reciprocal space, for very small angles: IŝI=s=2/; q=4/; q=2s • =uniform electron density • (s) Fourier transform of (x), which is form factor of grain [1 in grain, 0 outside] 7

  8. (0)= V • Volume of grain • I(0)= 2V2=n2 • I(s)I • centrosymmetric no matter about the shape of grain • Broadness of central diffuse peak: • (I(s)I2 dVs)/ I(0)I2 • dVs =volume element in s space equal to 1/V • For sphere of radius R with n electrons: • I(s)= n22(2sR) • (x) = 3 (sin(x)-xcos(x)/x3 • (x)=0 for: SminR=(2k+1)/4-1/(2k+1) 3 8

  9. Determination of grain size and porosity of nanostructures • Guinier law: I(q)=()2exp(-Rg2q2/3) for small q. The "average particle radii" can be estimated from radius of gyration Rg in the Guinier formula. • Mittelbach-Porod formula: • S/V =  {lim [q4I(q)]}/Q, q 9

  10. Determination of grain sizes • Guinier plot 10

  11. Determination of specific surface • Mittelbach-Porod approximation 11

  12. GIXR • Determination of layer thickness:2d=/(sinj+1 - sinj) • Grain sizes distribution within layer 12

  13. Further plans • Electron microscopy • IJS • Solar and galvanic cells • IRB • New sol-gel samples • NIC 13

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