Supplemental Information:
Coexistence of epitaxial lattice rotation and twinning tilt induced by surface symmetry
mismatch
L. Qiao1, H. Y. Xiao2,3, W.J. Weber2, and M. D. Biegalski1
1
Center for Nanophase Materials Sciences, Oak Ridge National Laboratory,
Oak Ridge, TN 37831, USA
2
School of Physical Electronics, University of Electronic Science and Technology of China,
Chengdu 610054, China
3
Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN
37996, USA
I. Experiments and theory details:
IrO2 films were epitaxially grown on Al2O3(0001) substrates by pulsed laser deposition (PLD)
using a metal iridium target. Laser ablation was performed at a repetition rate of 10 Hz and
energy density of 1.51 J/cm with a 248 nm KrF excimer. The Al2O3(0001) substrates were
annealed at 1075 °C for 2 hours in air to produce a high quality crystal surface for film epitaxy.
The films were grown in 200 mTorr oxygen, at a substrate temperature of 650 °C, and cooled
down to room temperature in 200 Torr O2 to ensure full oxidation. RuO2 and TiO2 films were
grown from stoichiometric ceramic targets using the same laser and oxygen conditions, but at
different substrate temperature, e.g. 500 °C for RuO2 and 800 °C for TiO2. These growth
conditions are optimized based on structural quality and phase purity. Crystal structure and
epitaxial relationship were determined by high-resolution monochromatic x-ray diffraction
(XRD) using a PANalytical 4-circle diffractometer with a goniometer head in 2θ-ω, rocking
curve and ϕ scan modes, as well as reciprocal space mapping. Typical film thicknesses for this
study are in the range of 10 to 200 nm; however, as XRD indicated that the structure of these
films were independent of film thickness, the following discussions are focusing on films with
200 nm thickness. Density functional theory calculations were performed using the generalized
gradient approximation (GGA) with Perdew-Burke-Ernzerhof functional based on the Vienna Ab
initio simulation package (VASP). All atoms were relaxed under geometrical optimization. An
8×8×8 k-point sampling in reciprocal space and plane-wave basis set with an energy cutoff of
500 eV were used, and total energy was minimized to ensure the force on each ion were
converged to less than 0.01 eV/Å.
1
II. Illustration of domain distribution
FIG. S1. Constructed In-plane domain configurations for coexisted (a) non-twinning and (b)
twinning domains for epitaxial IrO2/Al2O3(0001).
2
III. Crystal structure data for some of rutile-type metal dioxide oxide
d-blocks
AO2
a = b (Å)
c (Å)
dfilm (Å)
θ( )
3d
TiO2
4.593
2.958
5.463
32.7
3d
VO2
4.53
2.869
5.362
32.5
3d
CrO2
4.419
2.915
5.294
33.4
3d
MnO2
4.399
2.874
5.255
33.1
4d
RuO2
4.492
3.107
5.462
34.7
4d
RhO2
4.486
3.804
5.444
34.5
4d
PdO2
4.483
3.101
5.451
34.7
5d
TaO2
4.752
3.088
5.667
33
5d
OsO2
4.503
3.184
5.515
35.3
5d
IrO2
4.510
3.184
5.494
35
5d
PtO2
4.485
3.130
5.469
34.9
Table S1. A list of lattice constants and crystal acute angles for common 3d, 4d and 5d transition
metal dioxides. dfilm is the diagonal length of film (100) plane, please refer to Fig. 1f of the
manuscript for detail information.
3