S1
Supporting Information for:
Pre-Seeded Optical Scatterers as a Template for Enhancing
Order in Inorganic Phototropic Growth
Ethan Simonoff
†,‡
, Jonathan R. Thompson
§,‡
, Madeline C. Meier
†
, Kathleen Kennedy
§
,
Kathryn R. Hamann
†
, Nathan S. Lewis
†,‖,*
†
Division of Chemistry and Chemical Engineering
§
Division of Engineering and Applied Sciences
‖
Beckman Institute
‡
These authors contributed equally
California Institute of Technology
Pasadena, CA 91125
*Corresponding Author:
nslewis@caltech.edu
S2
Contents
S1.
Fourier analysis and peak-fitting methodology
S2.
Cross-sectional SEM images of phototropically grown Se-Te films
S3.
Simulated phototropically grown Se-Te on non-templated Pt substrates
S3
S1. Fourier analysis and peak-fitting methodology
Figure S1:
Pattern period was measured via analysis of the primary peaks in the 2D Fourier
transform (FT) spectra of low-magnification SEM images. An example 2D FT spectrum is
provided in (a). An associated plot of the horizontal (perpendicular to illumination polarization)
cross-section through the origin, integrated vertically over 30 pixels, is provided in (b). Pattern
period was defined as the average inter-lamellar spacing in phototropically grown films and was
measured by determining and inverting the centroid frequency,
ν
o
, of the primary peak. As
demonstrated in (b), the peaks in the 2D FT were fitted using a Lorentzian function. The fit domain
was chosen to minimize the residual between the peak intensity and the fitted curve.
Angular Averaging
a
b
S4
Figure S2:
Pattern fidelity in phototropically grown films was quantified by using a figure-of-
merit calculated as the vertical (parallel to illumination polarization) full width at half maximum
(FWHM) of the primary peak in the 2D FT spectra of low-magnification SEM images of respective
films. An example 2D FT is provided in (a) and the associated surface profile is provided in (b).
As in Figure S1, a Lorentzian function was used to fit 2D FT peak intensity. Using Equation S1,
the frequency value of the vertical FWHM was converted to radial coordinates to yield the angular
FWHM. Phototropically grown films demonstrating higher pattern fidelity consistently
demonstrated narrower vertical FWHM.
Equation S1:
Vertical FWHM (
o
)
=
ퟐ
풕풂풏
―
ퟏ
(
Vertical FWHM
ퟐ
⋅
흂
풐
)
a
b
S5
S2. Cross-sectional SEM images of phototropically grown Se-Te films
1 μm
4 μm
a
b
Figure S3:
Representative cross-sectional SEM images of a phototropically grown Se-Te film
deposited on physically templated Pt-coated n
+
-Si substrates with a Ti interlayer at (a) high and
(b) low magnification. The film was grown under polarized 630 nm excitation from a narrow-band
LED.
S6
S3. Simulated phototropically grown Se-Te on non-templated Pt substrates
Figure S4:
Simulated phototropic growth on non-templated Pt substrates with vertically polarized
illumination with
λ
= 630 nm. Simulations were performed with periodic boundary conditions. (a),
(b), and (c) are simulated under identical conditions and were used to demonstrate reproducibility
and measure pattern period. Following the procedure in Figure S1, the average pattern period for
these simulated patterns was 239 ± 13 nm, in excellent agreement with the expected trend of ~242
nm.
Angular Averaging
a
c
b
6 μm