Growth of ferroelectric Ba0.8Sr0.2TiO3 epitaxial films by UV pulsed laser irradiation of
chemical solution derived precursor layers
A. Queraltó1, A. Pérez del Pino*,1, M. de la Mata1, J. Arbiol1,2, M. Tristany1, A.
Gómez1, X. Obradors1, T. Puig1
1
Institut de Ciència de Materials de Barcelona, Consejo Superior de Investigaciones
Científicas (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Catalonia, Spain.
2
Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys,
23, 08010 Barcelona, Catalonia, Spain
SUPPLEMENTAL MATERIAL
1. Photothermal simulation
As a first approximation, the model considers photothermal and not photochemical
mechanisms as the main ones acting on the irradiated materials. The calculations are
performed by numerically solving the heat equation (S1) in combination to the finite
element method (FEM). A two-dimensional BST/LNO/LAO architecture is considered
with thicknesses of BST, LNO and LAO systems of 40 nm, 25 nm and 1 m,
respectively.
 t  

 
T
F 4 Ln ( 2)
C p
 k thT   e
t

2
1  R e z
(S1)
In heat equation, T is the temperature, t the time, ρ is the material density, kth the
thermal conductivity, Cp the specific heat capacity, F is the incident laser fluence which
is assumed to be uniform in the simulation,  is the laser pulse duration (Gaussian
evolution with ~3 ns FWHM), R is the reflectance of the material in normal incidence to
its surface, and  is the optical absorption coefficient at  = 266 nm wavelength. The
values of optical and thermophysical magnitudes for BST, LNO and LAO materials are
presented in Table S1. It should be noted that, due to the lack of experimental data, the
variation of thermophysical properties with temperature is not considered. Moreover, it
is also assumed that all the accumulated laser pulses have the same effect in the
irradiated material. Then, the “incubation effect” is neglected for the sake of simplicity.
FEM method is applied dividing the geometry in small triangle domains (mesh), with
maximum size for each unit of one order of magnitude lower than the optical
penetration depth in each layer. We assumed symmetry along the XY plane, and
negligible convection and radiation losses.
Example of the BST/LNO/LAO meshed geometry used in numerical simulations.
2. Materials parameters used in photothermal simulation.

Melting
kth
Cp
point
Kg/m3
W/m K
J/kg K

m-1
R
%
K
BST
5900 [†] 4.1 [†]
472 [†] 1898 [†]
20.9×106 [+] 7 [+]
LNO
7200
10.0
400
1953 [*]
21.2×106
15
LAO
6500
11.7
448
2373
2.0×104
1
[+] Measured by spectrophotometry of an amorphous BST film.
[*] Melting point of La2NiO4
[†] Data of crystalline BST.
Table S1. Optical and thermal properties of the studied materials used for the numerical
simulations.
3. Optical properties of amorphous BST.
Fig. S1. Reflectance, transmittance, refractive (n) and extinction (k) coefficients,
absorption coefficient () and optical penetration depth (1/) of amorphous BST layers
as a function of the incident wavelength.
4. Additional PFM measurements
Fig. S2. Additional PFM amplitude-electric field butterfly and phase-electric field
hysteresis loops taken at different places of the samples obtained by laser irradiation
with 40 mJ cm-2 and 10000 accumulated pulses per site, and by thermal annealing at
900ºC during 14400 s.