Table 3 Comparison of experimentally established (according to X-ray
fluorescence analyses) and simulated (according to eqn (1)) composition
for a thin film of La0.50Sr0.50FeO3 prepared by ALD at 260 ◦C on a Si(100)
substrate
findings concur qualitatively with those for the La1-xCaxMnO3
phase.7,39 The deposited films obtain a higher Sr content than ex-
pected from the pulsed ratio. Like chemisorbed Ca(thd)2, Sr(thd)x
fragments (x = 1) probably exhibit smaller steric hindrances than
chemisorbed fragments of La(thd)3 and Fe(thd)3. The findings for
the La(thd)3 and Fe(thd)3 precursors reveal that a smaller surface
size is to be associated with the La(thd)x fragments (x = 1 or 2)
than the corresponding Fe(thd)x fragments (x = 1 or 2). This may
be interpreted as either evidence for a flatter shape of the Fe(thd)x
fragments (viz. less constraints acting on the central atom to ligand
bonds) than the La(thd)x fragments or by a statistical difference
in the x-parameter of the adsorbed M(thd)x fragments (M = Fe,
La).
Metal constituent (M)
La
Sr
Fe
Desired composition: La0.50Sr0.50FeO3
Desired DM (mole fraction of M per formula
unit)
0.25
0.25
0.50
Growth ratea UM (relative value)
Intermediate calculation: DM ¥ UM* ¥ UM**
0.568
1
0.348
0.0870 0.0494 0.284
Simulated pulsing ratio
0.207 0.118
0.676
6
0.667
Practical pulsing ratio (9 pulses per cycle)
Practical pulsing ratio (normalized to 1 mol
metal)
2
1
0.222 0.111
Intermediate calculation: PM ¥ UM
0.126 0.111
0.232
Acknowledgements
Simulated metal content (DM)
Analyzed metal content
0.269 0.237
0.245 0.250
0.494
0.505
The authors wish to thank Oddvar Dyrlie for his help with the
AFM images, Turid Winje for XRF measurements, Karina Barn-
holt Klepper for FT-IR measurements, and Dr M. A. K. Ahmed
for the synthesis of Sr(thd)2. The work has been supported
by the Research Council of Norway, Grant. No. 158518/431
(NANOMAT).
Obtained composition: La0.49Sr0.50Fe1.01O3
a Alternative designation: surface utilization coefficient.
composition–adjustment procedure. The table is intended to be
largely self-explanatory and only a few points will be commented
in the text.
References
Relative values for the growth-rate parameters UM are extracted
from fittings of experimental data to eqn (1). Depending on the
selected sets of experimental data used in these computations
somewhat different UM -ratio combinations may be obtained, e.g.
0.528 : 1 : 0.338 which we reported for ULa : USr : UFe in ref. 39 versus
0.568 : 1 : 0.348 extracted from the presently chosen experimental
data base. The present study has also given slightly different UM
ratios for Si(100) and soda-lime-glass substrates (0.568 : 1 : 0.348
versus 0.651 : 1 : 0.402). The UM-ratio triplets certainly carry appre-
ciable uncertainties (see also ref. 39), but at present it is difficult
to point at which and to what extent other effects contribute. The
1 R. L. Puurunen, J. Appl. Phys., 2005, 97, 121301–121352.
2 M. Nieminen, M. Putkonen and L. Niinisto¨, Appl. Surf. Sci., 2001, 174,
155–165.
3 M. Lie, H. Fjellva˚g and A. Kjekshus, Thin Solid Films, 2005, 488,
74–81.
4 M. Vehkamaki, T. Hatanpaa, T. Hanninen, M. Ritala and M. Leskela¨,
Electrochem. Solid-State Lett., 1999, 2, 504–506.
5 O. Nilsen, H. Fjellva˚g and A. Kjekshus, Thin Solid Films, 2004, 450,
240–247.
6 A. Kosola, M. Putkonen, L. S. Johansson and L. Niinisto¨, Appl. Surf.
Sci., 2003, 211, 102–112.
7 O. Nilsen, E. Rauwel, H. Fjellva˚g and A. Kjekshus, J. Mater. Chem.,
2007, 17, 1466–1475.
8 M. Nieminen, T. Sajavaara, E. Rauhala, M. Putkonen and L. Niinisto¨,
J. Mater. Chem., 2001, 11, 2340–2345.
9 M. Nieminen, S. Lehto and L. Niinisto¨, J. Mater. Chem., 2001, 11,
3148–3153.
10 O. Nilsen, M. Peussa, H. Fjellva˚g, L. Niinisto¨ and A. Kjekshus,
J. Mater. Chem., 1999, 9, 1781–1784.
11 H. Seim, M. Nieminen, L. Niinisto¨, H. Fjellva˚g and L.-S. Johansson,
Appl. Surf. Sci., 1997, 112, 243–250.
12 H. Seim, H. Molsa, M. Nieminen, H. Fjellva˚g and L. Niinisto¨, J. Mater.
Chem., 1997, 7, 449–454.
13 L. Sangaletti, L. E. Depero, B. Allieri, P. Nunziante and E. Traversa,
J. Eur. Ceram. Soc., 2001, 21, 719–726.
14 D. Kuscer, D. Hanzel, J. Holc, M. Hrovat and D. Kolar, J. Am. Ceram.
Soc., 2001, 84, 1148–1154.
15 E. Traversa, S. Matsushima, G. Okada, Y. Sadaoka, Y. Sakai and K.
Watanabe, Sens. Actuators, B, 1995, 25, 661–664.
16 J. Mizusaki, T. Sasamoto, W. R. Cannon and H. K. Bowen, J. Am.
Ceram. Soc., 1982, 65, 363–368.
17 U. Kersen, Analyst, 2001, 126, 1377–1381.
18 I. Hole, T. Tybell, J. K. Grepstad, I. Waernhus, T. Grande and K. Wiik,
Solid-State Electron., 2003, 47, 2279–2282.
19 J. Luning, F. Nolting, A. Scholl, H. Ohldag, J. W. Seo, J.
Fompeyrine, J.-P. Locquet and J. Stohr, Phys. Rev. B, 2003, 67, 214433–
214414.
20 M. F. Vignolo, S. Duhalde, M. Bormioli, G. Quintana, M. Cervera and
J. Tocho, Appl. Surf. Sci., 2002, 197–198, 522–526.
21 S. Zhao, J. K. O. Sin, B. Xu, M. Zhao, Z. Peng and H. Cai, Sens.
Actuators, B, 2000, 64, 83–87.
◦
temperature should ideally have been the same (260 C) in these
experiments. However, although there is some uncertainty with
regard to the precision in the temperature control of the reaction
chamber, it seems safe to conclude that temperature variations
are not the cause of the unveiled differences in UM -ratio triplets.
More likely sources may then rather be different positioning in
the reaction chamber, or signal the need for a different elemental
correction procedure for different types of substrates. For the
present purpose it does not, in practice, really matter which of
the UM -ratio triplets one chooses. We used 0.568 : 1 : 0.348 for the
case-study example in Table 3 and for other simulations of relative
composition and pulsing stoichiometry.
Proceeding down Table 3, the simulated pulsing ratios are
seen to agree quite well with the practical pulsing ratios. (Note
that the pulsing in practice has to be performed in whole-
numbered sequences.) The simulated metal content also agrees
reasonably well with the analyzed metal content, and when it
comes to the ultimate check of the usefulness of the proposed
composition–adjustment procedure the obtained composition
La0.49Sr0.50Fe1.01O3 is in excellent agreement with the planned
composition La0.50Sr0.50FeO3.
The same approach has been used to construct Fig. 10 which
illustrates the conversion of pulsed composition into deposited
composition for all La1-xSrxFeO3 films subject to this study. The
22 M. Rajendran, M. G. Krishna and A. K. Bhattacharya, Mod. Phys.
Lett. B, 2000, 14, 801.
488 | Dalton Trans., 2009, 481–489
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