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 Zagreb, Croatia, 1

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

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 FOR MORE INFORMATION 3

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

First team from Croatia on SAXS in Resources allocated to the project:”SAXS study of grain sizes and porosity in nanophase TiO 2 ” –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

Second team from Croatia on SAXS in Resources allocated to project:”SAXS, study of grain sizes and porosity in TiO 2, CeO 2 and CeO 2 /SnO 2 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

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)=  2 I  (ŝ)I 2 –ŝ =(ŝ-ŝ 0 )/ - 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

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

Determination of grain size and porosity of nanostructures Guinier law: I(q)=(  ) 2 exp(-R g 2 q 2/3 ) 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 [q 4 I(q)]}/Q, q  9

Determination of grain sizes 10 Guinier plot

Determination of specific surface Mittelbach-Porod approximation 11

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

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