William Angerer - Department of Physics and Astronomy - University ...

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strain induced defect states may be generated at or near the CaN / A1 2 0 3 interface.
Strain is expected to couple most strongly to the components of the susceptibility
elements that are perpendicular to the interface [11]. Thus, this effect may be most
easily observed in X~~;strain and x~;~strain. Note that the film coordinate. the xz plane
is a mirror plane. Therefore, susceptibility elements such as x~;~strain
and x.~~)~stram
are forbidden. )lote, these elements are defined to include only the effect of the strain
induced nonlinearity and do not result from a coordinate transformation.
vVe performed rotational symmetry measurements in the p-in/p-out polarizations
to probe CaN for these elements. vVe simplified our analysis by assuming \~~~stram =
x.~~/tram .
Thus, the second-order susceptibility, including the sample miscut and
strain, transforms as
R(
') R( ) R(A.) (2),strain
+ qJ io ¢ j{3 ~ k..,Xoth . (6.38 )
I . (6 38) (2),crystal (2) (2) d (2) Rmiscut·
n equatlOn . , h .
Xijk represents X.zxx, X xzx , an X. zzz , IS t e matnx
defined bv equation (63) v(2),strain represent v(2),strain and v(2),strain
- • 'Al1k AXZZ '\.zzx·
and R is the
matrix defined by equation (6.2). We deduced the miscut angle of our films from
the rotational symmetry data at an angle of incidence of 15° assuming x.~~~stram = O.
vVe repeated our rotational measurement over a two photon spectral range of 2.6
to 3.4 eV at an angle of incidence of 65° to fit for x~;~stTain
with the miscut angle
fixed from the 15° rotational scan. vVe were unable to detect any strain or miscut
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