Supplementary Material

Template-Stripped, Ultraflat Gold Surface with

Coplanar, Embedded Titanium Micro-Patterns

Nagaiyanallur V. Venkataraman, # Jia Pei,

# Clément V. M. Cremmel,

# Antonella Rossi,

#†

Nicholas D. Spencer #*

# Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich,

Wolfgang-Pauli-Str. 10, CH-8093 Zurich, Switzerland.

† Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Cagliari,

Cittadella Universitaria di Monserrato, I – 09100 Cagliari, Italy

*to whom correspondence should be addressed, e-mail: nspencer@ethz.ch, fax: +41 44 633

10 27

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Hexamethyldisilazane (HMDS) 1H,1H,2H,2H-perfluorooctyltrichlorosilane (PFOTCS)

Figure S1: Representative AFM images of the silicon surfaces silanized with (a) HMDS and

(b) PFTOCS. RMS roughness of the silanized surfaces are 0.19±0.02 nm for HMDS and

0.21±0.03 nm for PFOTCS.

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Figure S2: Histograms of adhesion forces on clean silicon wafer (top) and silicon wafers

silanized with HMDS (middle) and PFOTCS (bottom) measured against a standard Si3N4 tip.

A reduction in adhesion force by up to 70% was achieved with PFOTCS, whereas this value

for HMDS was about 35%.

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Figure S3: Representative AFM images on gold (left) and titanium (right) regions of a

template stripped Ti-Au patterned sample obtained by PFOTCS silanization. The RMS

roughness of the Au region is 0.27 nm and that of the Ti region is 0.29 nm.

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Figure S4: Photograph of template-stripped ultraflat Ti-Au micro-patterned samples

prepared using an appropriately designed photo-mask, with a continuously changing density

of micro-patterned regions, as visible from the color change, resulting in a “gradient”

structure of coplanar titanium within a gold surface. Each pixel is 25-30 µm in size. A more

detailed description of the mask design and photolithography can be found in ref 27.

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(a) (b)

Figure S5: Optical microscopic images obtained with a Zeiss AXIO microscope of (a)

Template-stripped Ti-Au samples with 1 mm Ti circular patterns prepared without any

template passivating silane layer, showing large area of defects on Ti patterns, whereas (b)

displays a well-stripped ca. 1 cm x 1.5 cm sized Ti-Au patterned sample prepared with

HMDS silanization of the silicon template.

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Figure S6: A schematic drawing comparing the use of single- and bi-layer photolithography

process (side view). Partly adapted from the manufacturer’s data sheet for lift-off resist

(http://microchem.com/pdf/PMGI-Resists-data-sheetV-rhcedit-102206.pdf).

Si LOR

S 1818

mask

Develop

Metal

deposi on

Li -off

Si

S 1818

mask Expose

Develop

Metal

deposi on

Li -off

Single-layer photolithography vs Bi-layer photolithography

Backfill with second metal

Template-stripping

Straight

structure “Undercut”

structure

metal layer

in contact

with resist metal layer

not in contact

with resist

Resist

residues “clean”

li -off

Expose

Ultraflat Ti-Au

pa erned surface

Valley-like defect (width

~ 100nm, depth ~10nm)

along Ti-Au boundary

Defect-free (< 1nm)

Ti-Au boundary

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Figure S7: SEM image measured at the boundary of a Ti-Au pattern prepared by 2-layer

photolithography, obtained with two different detectors. No topographical edge is visible on

the secondary electron image on the right (SE2 detector), whereas the chemical contrast is

visible in the backscattered electron image on the left (InLens detector). The Ti-Au boundary

is indicated by arrow marks for clarity.

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Figure S8: A comparison of the spatial resolutions of the two imaging surface analytical

techniques used in the characterization of the Ti-Au micro-patterns. The 80-20 interface as

determined from the ToF-SIMS Au- image (left) is 1.8 µm whereas the interface as

determined from the XPS Au4f map (right) is 18.4 µm. This clearly demonstrates that the

non-vanishing intensity of the Au4f signal measured inside the Ti patterns by XPS (Figure 8)

arises due to the limited spatial resolution of the instrument. Also, the larger value of the

interface obtained from the ToF-SIMS image above compared to that reported in the text

(Figure 7) is due to the greater signal-to-noise ratio for the total-intensity maps.