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Thus the mean R In-In is expected to be smaller than a. This is not observed for most of our samples, since locally the chemical
character of the In – N bond, determined by the hybridization, dominates on the stress-induced bondlength distortions.
Therefore, due to the high resistance of the In – N bonds to distortions, which is a result of the high ionicity of InN [4], the
stress – induced changes of the a lattice parameter are accommodated mainly by bond angle distortions. A linear fit of the
dependence of R In – In on the basal plane strain (e || ) determined using the relaxed value of a 0 = 3.535 Å [2] yields the following
equation: R In – In = 3.533(±0.001) + 1.561(±0.337)×e || resulting to an internal strain parameter for the In – In distance equal to
ζ´h= 0.56. The Debye – Waller factors are ranging from 4.3×10 -3 to 5.8×10 -3 (±1.0) Å 2 and from 6.5×10 -3 to 7.4×10 -3 (±0.5)
Å 2 for the In – N and In – In pairs, respectively.
In conclusion, the In – N and In – In distances determined from the EXAFS analysis, are found to resist to changes driven
by the presence of compressive or tensile stress. The dependence of the In – In distance on the basal plane strain (e || ) is
described by a linear equation of the form R In–In =3.533 + 1.561e || .
3.555
compressive
tensile
R In-In
(Å)
3.550
3.545
3.540
3.535
3.530
644
628
643
relaxed (Dimakis et al )
R In-In
=a
385
3.525
3.520
585
631
632
3.515
3.515 3.520 3.525 3.530 3.535 3.540 3.545 3.550 3.555
a(Å)
Figure 2: Dependence of the In – In distance on the a lattice parameter. The dashed line corresponds to the
dichotomous of the axes and the vertical line at a= 3.535 Å corresponds to the relaxed value of a. according to
Dimakis et al [2].
Acknowledgement: The EXAFS measurements were financed by the European Community IA-SFS program under the
Contract RII3-CT-2004-506008 and from the program of GSRT “PYTHAGORAS”.
[1] V. Yu. Davydov, A. A. Klochikhin, R. P. Seisyan et al, phys. stat. sol. (b), 229, R1–R3 (2002).
[2] E. Dimakis, E. Iliopoulos, K. Tsagaraki et al, Appl. Phys. Lett. 88, 191918 (2006).
[3] A. L. Ankudinov, B. Ravel, J.J. Rehr, S.D. Conradson, Phys. Rev. B, 58, 7565 (1998).
[4] A. F. Wright, J. Appl. Phys. 82, 2833 (1997).
[5] F. d’Acapito, F. Boscherini, S. Mobilio, A. Rizzi, R. Lantier, Phys. Rev. B 66, 205411 (2002).
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