F.M. Pontes et al. / Journal of Alloys and Compounds 477 (2009) 608–615
615
Table 2
Evolution of the roughness and average grain size parameters of XWO4 (X = Ca, and Sr) thin films on silicon substrate.
CaWO4
SrWO4
Annealing temperature (◦C)
Rms (nm)
A.G.S (nm)
300
0.358
–
350
0.413
15
400
1.270
30
500
6.891
110
300
0.247
–
350
0.359
20
400
1.520
50
500
6.623
100
A.G.S, average grain size; Rms, roughness.
4. Conclusions
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We have successfully demonstrated, the growth of XWO4 (X = Ca
and Sr) thin films with scheelite-type structure onto silicon sub-
strates by a soft chemical route, the so-called polymeric precursor
method. The experimental results by NMR and FT-Raman spec-
troscopy showed that the formation of the citric acid metallic
complex took place with the COOH terminal group of citric acid.
Polycrystalline, homogeneous, dense, and crack-free thin films
were successfully prepared on silicon substrates using the spin-
coating technique. The XRD results showed that no intermediate
phase was detected and a single XWO4 (X = Ca and Sr) phase was
crystallized from an amorphous matrix. XRD results showed a
tetragonal structure for the polycrystalline thin films with lat-
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techniques provides comprehensive information on the vibrational
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The authors thank Rorivaldo Camargo for his technical support
with the AFM analysis. This work was financially supported by the
Brazilian agencies FAPESP/CEPID, (FAPESP process no. 06/53926-4
and no. 08/53513-7).
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