Polycrystalline Au nanomembrane as a tool for two-tone micro/nanolithography

Transcription

1 Supporting information for Polycrystalline Au nanomembrane as a tool for two-tone micro/nanolithography Chang Mok Oh, Ki Hong Park, Jin Hyun Choi, Seongpil Hwang, Heeso Noh, Young Moon Yu, and Jae Won Jang*, Department of Physics, Pukyong National University, Busan, 48513, Republic of Korea Department of Advanced Materials Chemistry, Korea University, Sejong, 30019, Republic of Korea. Department of Nano and Electronic Physics, Kookmin University, Seoul, 02707, Republic of Korea. LED Marine Convergence Technology R&BD Center, Pukyong National University, Busan 48547, Republic of Korea. * jjang@pknu.ac.kr 1

2 1. Occurrence of H 2 gas bubbles in positive-tone micro/nanolithography In positive-tone micro/nanolithography, a KOH aqueous solution (1 M) is poured onto a line-shaped PDMS micro-stamp. The PDMS is then stamped onto an Au nanomembrane with an indicating Al layer of 200 nm. Here, H2 gas is emitted due to an acidic reaction between the Al and OH -, as shown in Figure S1. Figure S1 Snap shot images captured during positive-tone micro/nanolithography. The images were taken at (a) 0 sec and (b) 30 sec. A H2 gas bubble was observed during an acidic reaction within the confined volume of the line-shaped PDMS. 2

3 2. Invariant ph of a reaction solution during negative-tone micro/nanolithography To measure the change in ph during the etching reaction of the KOH solution on an open surface, 1 M KOH (1 μl) was dropped onto a 30 nm Au nanomembrane with an indicating Al layer of 200 nm deposited over a glass substrate. Snap shot images with increasing loading time of the KOH solution are displayed in Figure S2. Meanwhile, the ph of the reaction solution was measured using ph test paper (Whole Range Paper, Advantec) at 0 min, 1 min, 2 min, and 3 min during the loading time of the KOH solution [the inset of Figure S2(c)]. The color of the ph test papers looked equivalently blue, indicating that the ph of the loaded KOH solution remained strongly basic (ph 14), and was unchanged by the reaction. Alternatively, a reaction on an open surface was carried out within a relatively large volume of KOH solution. Here, a decrease in ph resulted from a reaction in the PDMS stamps. The volumes of KOH solution used in the PDMS stamps and on the open surface are shown in Table S1. To be practical, a volume of KOH solution, loaded in case the reaction on the open surface, is ten times greater than that used in the PDMS stamps. Figure S2 Snap shot images of the KOH solution etching processes on an open surface. The images were captured at (a) 0 min, (b) 1 min, and (c) 3 min, respectively. Inset: images of ph test papers during the KOH solution etching process, with reactions at (1) 0 min., (2) 1 min., (3) 2 min., and (4) 3 min, respectively. 3

4 Table S1. Volumes of KOH solution used for reactions in the PDMS stamps and on an open surface. Line PDMS [ l] Dot PDMS [ l] Rectangle PDMS [ l] Open surface [ l]

5 3. Electron diffraction measurement of Au nanomembranes Similar to the 10 nm thick Au nanomembrane shown in Figure 3(a), relatively thicker Au nanomembranes (20 nm, 30 nm, and 40 nm) show polycrystallinity. Figures S3 shows randomly oriented Au lattices in the high resolution (HR) TEM images (a-c), and also shows polyscrystalline sine (concentric circles) in electron diffraction patterns (d-f). Lattice constant of Au nanomembranes with 20 nm, 30 nm, and 40 nm thickness is about 2.3 Å as same as that of 10 nm thick Au nanomembrane. Figure S3 (a-c) HR-TEM images and (d-f) electron diffraction patterns of Au nanomembranes with thicknesses of (a, d) 20 nm, (b, e) 30 nm, and (c, f) 40 nm. 5

6 4. Configuration for measurement of pore size and number of Au nanomembranes For a convenient display, intensity of TEM images of the Au nanomembrane were inverted; the darkest part of the TEM images represents pores in the Au nanomembrane with this configuration. We have measured size and number of pores of the 10 nm thickness Au nanomembrane at first. As the next step, intensity of TEM images of the other Au nanomembranes has been equivalently adjusted to match with that of the 10 nm of Au nanomembrane. Thereafter, measurements of pores of the other Au nanomembranes were carried out. In detail, contrast of TEM images of the Au nanomembranes has been modified by ImageJ software using Threshold function in Adjust/Image category. Minimum and maximum values of the TEM images brightness were equivalently adjusted to have same magnitude and baseline. Cut-off value of Threshold function was selected as 95% of histogram of brightness values in the TEM image of 10 nm thickness Au nanomembrane. Then, the same cut-off value of Threshold function was used in the TEM images of the other Au nanomembranes. 6

7 5. Mechanism of thickness dependent porosity in Au nanomembranes The 10 nm Au nanomembrane can be regarded not to fully cover substrate s surface owing to Volmer-Weber mode. Until substrate s surface is fully covered, Au grains are randomly deposited with filling empty space of the Au nanomembrane with progressive nucleation and growth of seeds; which process can be called as mono-layer deposition process. During the mono-layer deposition process, both pore size and number decrease as deposition of Au grains increases. After the substrate s surface is fully covered, then Au grains will mainly pile up on the first layer of Au grains rather than filling empty space of the Au nanomembrane; which process can be named as multi-layer deposition process. During the multi-layer deposition process, pore size will be determined by gap between the deposited Au grains. Hence, only pore number decreases while pore size is not remarkably changed as deposition of Au grains increases. We regard that the mono-layer deposition process is dominant until 20 nm of Au nanomembrane, then multi-layer deposition mainly happens more than 20 nm deposition. In Figure S4(a), 3D morphology of Au nanomembranes with 10 nm, 20 nm, and 30 nm of thickness is displayed, and schemes of mono-layer and multi-layer deposition processes are displayed in Figure S4(b). The number of pores will relatively rapidly decreases when the Au thickness increases from 20 nm to 30 nm, because deposited Au grains only contribute to piling up on the first layer of Au grains. On the other hand, deposited Au grains contribute to both piling up and filling empty space of the Au nanomembrane when the Au thickness increases from 10 nm to 20 nm; the deposited Au grains influence on decreasing both pore size and number. When the Au thickness increases from 30 nm to 40 nm, decrease of pore number seems to lessen, which can be regarded as a saturation behavior. 7

8 Figure S4 (a) 3D morphology images of Au nanomembranes with 10 nm, 20 nm, and 30 nm of thickness, respectively. The scale bar denotes maximum and minimum thickness of the every Au membrane. (b) Scheme of two different deposition process. Mono-layer deposition dominantly happens until 20 nm of thickness, and multi-layer deposition will be dominant deposition from 20 nm to 30 nm of thickness. 8

9 6. Details for the measurement of KOH etching rate on the indicating Al layer The etching rate of KOH, shown in Figure 2(g), has been calculated from the etched volume of an indicating Al layer underneath Au nanomembranes with thicknesses of 10 nm, 20 nm, 30 nm, and 40 nm. The expansion rate of the etched volume of Au nanomembranes was measured by direct observation of the etching process of the underlying Al indicator layer, as shown in Figure S5. Figure S5(a) is a captured image just after dropping KOH solution (1 M, 0.4 L) onto an Au nanomembrane (30 nm) deposited onto a 200 nm-thick Al layer. The etching area of the indicating Al layer can be measured from sequentially captured snapshot images at 40 s intervals [the red dashed circle in Figure S5(b)]. The etched area of the Al layer gradually grew as the KOH loading time increased. The etched volume of the Al layer was obtained from multiplying the etching area and the Al layer thickness. The expansion rate of etched volume of the Al layer (mm 3 /s) was determined by dividing the etched volume by the KOH loading time. Figure S5 Snap shot images of an Au nanomembrane (30 nm thickness) deposited onto an Al layer (200 nm thickness) after dropping KOH solution (1 M, 0.4 l) onto the surface. The images were taken at (a) 0 sec.; (b) 40 sec.; (c) 1 min., 20 sec.; (d) 2 min.; (e) 2 min., 40 sec.; and (f) 3 min., 20 sec., respectively. Scale bars are 1 mm. 9

10 7. KOH etching with a 50 nm Au nanomembrane Etching an indicating Al layer (200 nm thickness) underneath a 50 nm-thick Au nanomembrane using aqueous KOH (1 M) solution was carried out with a droplet loading and a PDMS stamping, as shown in Figures S6(a) and (b), respectively. After a given number of hours or days of reaction (KOH solution loading time), Al layer etching was examined by observation using an optical microscope with sequential DI washing of the samples. Noticeable etching of an indicating Al layer was not observed in both cases, as shown in Figure S6. Hence, it can be concluded that OH - ions did not effectively penetrate into the 50 nm-thick Au nanomembrane. Figure S6 Experimental schemes and optical microscopic images after reaction with the KOH solution (1 M) on a 50 nm-thick Au nanomembrane. These reactions were carried out by (a) droplet and (b) PDMS stamping, respectively. 10

11 8. Electrical properties of Au nanomembranes The electrical properties of Au nanomembranes with thickness of 20 nm, 30 nm, and 40 nm, respectively, were characterized by current voltage (I V) measurements with a source meter (2400, Keithley Instruments Inc.) using a two probe method. Silver wires (diameter: mm, GoodFellow) were line contacted at mm lengths, with approximately 1 mm gaps on the Au nanomembranes using a silver paste. Resistivity ( ) of the Au nanomembranes (Inset table of Figure S7) were obtained from the following equation: ρ, where V/I is a linearly fitted slope from the I V curves, t is thickness of the Au nanomembrane, l is length of the line-contact of the silver wires, and d is gap distance between the two-line contacts. The of the Au nanomembranes gradually decreased as thickness increased. Figure S7 I-V characteristics of the Au nanomembranes. 11

12 9. Toluene permeability of Au nanomembranes Toluene permeability of an Au nanomembrane (30 nm thickness) deposited on a 200 nmthick poly(3-octylthiophene-2,5-diyl) (P3OT) film is shown in Figure S8. The P3OT film was spin-coated onto a glass substrate at 1500 rpm for 35 s. Then, a 30 nm-thick Au nanomembrane was deposited on the P3OT spin-coated substrate. A toluene droplet was loaded onto the Au P3OT spin-coated substrate, then the P3OT film was dissolved by penetrating toluene molecules through the Au nanomembrane. The permeability (K) of toluene has been obtained by a linear fitting of toluene reaction time (loading time)-dependent dissolving rate using Darcy s law, as a similar parametric setting has been executed for measuring OH - ion permeability. The toluene permeability on a 30 nm-thick Au nanomembrane was 46 times smaller than that of an OH - ion. The smaller K of toluene could have been due to the fact that the toluene molecule was larger than the OH - ion. Figure S8 Dissolving volume of P3OT film (200 nm thickness) by toluene penetrating through a 30 nm-thick Au nanomembrane. The permeability (K) of the toluene molecule was obtained by a linear fitting using Darcy s law. 12

13 10. Au nanomembrane based two-tone lithography with Cu layer Positive and negative tone Au nanomembrane based lithography has been carried out with Cu layer to substitute for Al layer. Au/Cu (20 nm/100 nm) multi-film was thermally deposited on thoroughly cleaned pieces of cover class. While 2 M KOH aqueous solution was used for the positive tone lithography, nitrate based aqueous Cu etchant, which is composed of nitric acid (6%), ceric ammonium nitrate (20%), and water (74%), was used for the negative tone lithography. Figure S9 shows result of positive tone lithography with a line shape PDMS stamp (width: 10 m, gap: 5 m). As shown in Figure S9(a), array of protruded micro-walls (the dark part of the image) are clearly fabricated in over an millimeter scale [the inset of Figure S9(a)], and the micro-walls are assumed as copper hydroxide [Cu(OH)2] and copper oxide (CuO) due to assigning of XRD spectrum of the sample [Figure S9(b)]. AFM image and cross sectional line profile of the micro-walls clearly show that the fabricated patterns are protruded structures. Figure S9 (a) A microscopic image of array of micro-walls fabricated by positive tone Au nanomembrane based lithography. Inset: An entire picture of the fabricated sample. (b) XRD spectrum of the sample. (c) AFM image of the micro-walls and a line profile of the AFM image of the micro-walls (obtained by the red line from the AFM image). 13

14 Figure S10 shows result of negative tone lithography. To know whether the Cu etchant penetrates an Au nanomembrane and etches away the Cu layer under the Au nanomembrane, a droplet of the Cu etchant was put on an Au/Cu (20 nm/100 nm) multi-film coated piece of cover glass. After reaction time for 10 min, the sample was gently washed by distilled water and pictures were taken as shown in Figure S10(a), (b), and (c). It is notified that etching of the Cu layer under the Au nanomembrane obviously works on. Therefore, array of micro-tunnel fabrication was carried out with an Au/Cu (20 nm/100 nm) multi-film coated piece of cover glass by negative tone Au nanomembrane based lithography. By means of photolithography, array of trenches of 3 m width was fabricated with photoresist (PR) on the sample surface. The Cu etchant solution were loaded for 10 min and microscopic images of the samples were obtained as shown in Figure S10(d), (e), (f) and (g). It is assumed that the Cu layer under the Au nanomembrane is etched and tunnel like structures are fabricated; the bottom view images show space underneath the cover glass substrate. 14

15 Figure S10 (a-c) Snap shot pictures of an Au/Cu (20 nm/100 nm) multi-film coated piece of cover glass after loading a droplet of Cu etchant and a sequential washing: (a) top and (b, c) bottom view images of the sample. Unit of scales show in (a) and (b) is mm. (d-g) Au/Cu (20 nm/100 nm) multi-film coated pieces of cover glass are also used in negative tone Au nanomembrane based lithography. Microscopic images of array of micro-tunnels fabricated by the negative tone lithography: (d, e) top and (f, g) bottom view images of the sample captured by (d, f) bright field and (e, g) dark field mode optical microscope. 15

16 11. XPS spectrum of protruded micro-walls fabricated by positive-micro/ nanolithography X-ray photoelectron spectroscopy (XPS) was carried out for chemical characterization of the patterned micro-walls. Figure S11 represents the Al 2p XPS spectrum of the micro-wallpatterned sample shown in Figure 3(b). The XPS spectrum peak shown in Figure S11 was assigned two components. The XPS spectrum could have been fitted with the main Al(OH)3 peak and an additional Al peak. XPS characterization confirms Al(OH)3 formation by the suggested mechanism, shown in Scheme 1. The additional Al peak would originate from the remaining Al element in the indicating Al layer, after the protruded Al(OH)3 pattern array fabrication. Figure S11 Al 2p XPS spectrum of the micro-wall-patterned sample fabricated by positivetone micro/nanolithography. 16

17 12. Proof of the absence of salt on Al(OH) 3 patterns fabricated using positivemicro/nanolithography An absence of salt generation during positive-tone micro/nanolithography using an Au nanomembrane was confirmed upon checking the dissolution of Al(OH)3 micro-walls by soaking the samples in DI water for several hours. For the dissolution experiments, Al(OH)3 micro-walls with 5 m width and 1 m thickness were fabricated with a 10 m gap, as shown in Figures S12(a) and (a-1). If salts were included in the Al(OH)3 micro-walls, dimensional changes in the Al(OH)3 micro-walls would be expected due to the dissolution of salts during DI water soaking. After overnight dissolution with DI water (16 hours), significant changes were observed in the Al(OH)3 micro-walls [Figure S12(b)]. Even after 67 hours of soaking in DI water, observable dimensional changes in the Al(OH)3 micro-walls were not measured, as shown in Figures S12(c) and (c-1). Therefore, there was no indication that salts were generated during positive-tone Au nanomembrane micro/nanolithography. Figure S12 Optical microscopic images of Al(OH)3 micro-walls captured (a) before and after soaking in DI water for (b) 16 and (c) 67 hours. Scale bars are 10 μm. SEM images of an Al(OH)3 micro-wall (a-1) before and (c-1) after soaking in DI water for 67 hours. Scale bars are 1 μm. 17

18 13. Yield of positive tone lithography with PDMS stamps of same contact area and different volumes The etching rate of KOH, We are thankful to the valuable reviewer s comment. We have done additional experiments for positive tone lithography with dot patterned PDMS stamps of same contact area and different volumes; dot stamp #1 (dot-300, : 4 m, interval: 6 m, depth: 300 nm) and dot stamp #2 (dot-700, : 4 m, interval: 6 m, depth: 700 nm). Figure S13 shows the yield of fabricated pattern volumes and the volume of space of the PDMS stamps (Vspace of PDMS), including data from the manuscript: Line, Dot, and Rectangle denote the PDMS stamps in Figure 3(f) [A-Line, B-Dot, and C-Rectangle shown in Figure 3(f), respectively]. Because the yield of fabricated pattern volumes saturate at 2 M of KOH concentration, the yield data of Figure S13 are chosen at 2 M of KOH. The yield is definitely inversely proportional to the Vspace of PDMS as shown in Figure S13. Especially, the dependence between the yield and Vspace of PDMS is still observed in cases of patterns by the PDMS stamps of same contact area and different volumes (dot-300 and dot-700). Figure S13 The yield of fabricated pattern volumes and the volume of space of the PDMS stamps (Vspace of PDMS), including data from the manuscript 18

19 14. A control experiment: positive tone lithography without Au nanomembrane Control experiment about positive tone lithography using a PDMS without Au nanomembrane is carried out. We observed that more constructed (uniform and flat) patterns can be fabricated by positive tone lithography with the Au nanomembrane than the lithography without the Au nanomembrane. Figure S14 shows that cross-sectional SEM images of the protruded patterns fabricated by the positive tone lithography with and without Au nanomembrane, respectively. The protruded patterns (with the Au nanomembrane) shown in Figure S14(a) are more uniform than the patterns fabricated by the control experiment (without the Au nanomembrane) [Figure S14(b)]. In addition, the protruded pattern by the control experiment shows rougher top-surface of the protruded patterns and surface of the substrate. In detail, arithmetic average of absolute values of the surface roughness (Ra) at top of the protruded patterns and the substrate are measured from the zoomed images of Figure S14. In case of the lithography with the Au nanomembrane, Ra of the protruded patterns and substrate are ~21.6 nm and ~15.4 nm, while Ra of the control experiment are ~79.9 nm and ~34.0 nm, respectively (Figure S14). Hence, the rougher surface of substrate in case of the control experiment would result from uneven etching by the freely leaked out etching solution. 19

20 Figure S14 Optical SEM images of a control experiment by the positive tone lithography (a) with and (b) without Au nanomembrane 20

21 15. Observation on Al layer etching under Au nanomembrane in the fabricated patterns by positive tone lithography Careful observation on Al layer etching under Au nanomembrane in the fabricated patterns by positive tone Au nanomembrane based lithography is carried out. Etching of the Al layer under Au nanomembrane will result in decrease of the thickness of the Al layer, which can be observed in back scattering electron (BSE) mode cross sectional SEM image of the pattern. The Al and Au layers are distinguishable in BSE mode SEM image. As shown in Figure S15, it turns out that thickness of Al layer under Au nanomembrane decreases from 200 nm to about 110 nm after the positive tone lithography. Figure S15 Secondary electron (SE) and back scattering electron (BSE) mode SEM images of a micro-wall after positive tone lithography done by 1 M KOH.. 21

22 16. Fabrication of a freestanding THz responsive photonic microstructure Figure 4(a)iii shows that Al(OH)3/Au slab with an array of micro-cavities on an Al layerdeposited glass substrate. Polystyrene (PS) was spin-coated onto the sample shown in Figure 4(a)iii. Then, a freestanding THz responsive photonic microstructure was obtained by placing the PS spin-coated sample into a KOH solution, as shown in Figure S16. As the Al layer was removed by the KOH solution, the glass substrate dropped down into the KOH solution, and the PS-coated Al(OH)3/Au slab with an array of micro-cavities was floating on the KOH solution, as shown in the inset of Figure S16. The floating, freestanding PS-coated Al(OH)3/Au slab (i.e. freestanding THz responsive, photonic microstructure) could be conveniently picked up by a tweezer or transferred to a substrate of interest. Figure S16 Scheme for the fabrication of a freestanding THz responsive, photonic microstructure. Inset: a snap-shot image of the freestanding microstructure after Al layer removal by KOH solution. 22

23 17. Diffraction modes of an Al(OH) 3 slab with an array of micro-cavities The absorption spectra displayed in Figure 4(e) were measured using an attenuated total reflection (ATR) method. Through an ATR crystal (Germanium, n = 4), an IR beam impinged onto a sample surface with in = 70, as shown in Figure S17(a). The direction of the incident IR beam and the Al(OH)3 slab with an array of micro-cavities (2D hcp with 8 m) were configured as shown in Figure S17(b). In Figure S17(c), Ewald spheres (spheres of diffraction) and a reciprocal lattice of the sample are displayed in a kx ky plane view and kx kz plane view. The red and blue circles represent Ewald spheres in the ATR crystal and air, respectively. The incident IR beam was diffracted by the array of micro-cavities. Diffraction occurred when the reciprocal lattice points lied on an Ewald sphere surface. In our structure, the reciprocal lattice seemed to be composed of dots along the kx ky plane. However, the dots seemed to form lines with a direction along kz [Figure S17(c)]. Therefore, the black dots inside the red and blue circles indicate all possible diffraction modes [Figure S17(c)]. Although some diffraction modes cannot go out of the ATR crystal due to total internal reflection, others can escape. The black dots in the red area indicate the diffraction modes which cannot go out of the ATR crystal, while the dots in the blue area represent the diffraction modes which can escape the ATR crystal. Due to this diffraction, it was expected that when a reciprocal lattice touched an Ewald sphere, the diffraction modes marked as dotted lines in Figure 4(e) could be characterized by drawing Ewald spheres with wavelengths at the diffraction modes. Figure S18(a) shows Ewald spheres at 6.52 m in the reciprocal lattice of the sample. Here, the reciprocal lattice meets the blue Ewald sphere surface at two points along the kx ky plane. It is apparent that relatively strong diffractions along the kx ky plane exist in this diffraction condition. 23

24 Similarly, Figures S18(c), (d), (f), and (g) show relatively strong diffractions along the kx ky plane. In other words, the reciprocal lattice meets the blue Ewald sphere along kx ky plane. On the other hands, Figure S18(e) and (h) show that the reciprocal lattice point is located at the center of the blue Ewald sphere. That is, the reciprocal lattice point meets the blue Ewald sphere along the kz axis. Under this diffraction condition, a relatively strong diffraction along the kz axis would be expected. In particular, both specific diffraction conditions (along the kx ky plane and along the kz axis) are shown in Figure S18(b). Based upon this characterization, we conclude that the diffraction modes marked as dotted lines in Figure 4(e) represent specific diffraction conditions of the samples (relatively strong diffractions along the kx ky plane or along the kz axis). Figure S17 (a) Schemes of the apparatus for a sample stage of the ATR spectrometer and (b) configuration between the sample and incident IR beam. (c) Ewald spheres (red: ATR crystal; blue: air) and reciprocal lattice of the sample. kin aims toward the origin of the reciprocal lattice (marked as thicker than the others). 24

25 Figure S18 (a) Ewald spheres at a wavelength of 6.52 m Figure S18 (b) Ewald spheres at a wavelength of 6.72 m 25

26 Figure S18 (c) Ewald spheres at a wavelength of 7.05 m Figure S18 (d) Ewald spheres at a wavelength of 7.96 m 26

27 Figure S18 (e) Ewald spheres at a wavelength of 9.03 m Figure S18 (f) Ewald spheres at a wavelength of 9.88 m 27

28 Figure S18 (g) Ewald spheres at a wavelength of m Figure S18 (h) Ewald spheres at a wavelength of 13.5 m 28

29 The shifted absorption peaks is observed in Figure 4(e)iv. The PS spin-coated flexible Al(OH)3/Au slab with an array of micro-cavities (THz photonic structure) could be bend (or extended) during the measurement since it is tightly pressed by a tip to contact on ATR crystal. Therefore, we assume that the shifted absorption peaks resulted from distorted lattice constant by extending of the flexible sample. In order to assign the peaks at 6.09 m, 7.28 m, and 12.5 m of the flexible sample [Figure 4(e)iv], diffraction modes in the 2D hcp lattice with distorted lattice constant are examined. As the first step, we presumed that lattice constant of the flexible sample is elongated to direction of the incident light by pressure applied to the sample. Then, we examine how specific diffraction modes are available at the wavelength of the absorption peaks in the flexible sample, examining by Ewald spheres and a reciprocal lattice of the sample with the elongated lattice constant. Figure S19(a) shows scheme how the flexible sample can be distorted during the absorption measurements. We have determined the degree of elongation as the specific diffraction condition (meeting points between Ewald spheres and the reciprocal lattice) are remarkably counted; specific diffraction conditions along the kx ky plane with the distorted lattice constant (4.8% elongation to direction of the incident light) at 6.09 m, 7.28 m, and 12.5 m of wavelength are represented by the green circles in Figure S19(b), (c), and (d), respectively. In the result, the shifted absorption peaks result from distortion of the flexible sample during the absorption measurement; that is 4.8% elongation of the sample to direction of the incident light. 29

30 Figure S19 (a) Scheme about elongation of the flexible sample during absorption measurements. Ewald spheres at wavelength of (b) 6.09 m, (b) 7.28 m, and (c) 12.5 m. The green-circles denote specific diffraction points. 30

31 18. Fabrication of micro-tunnels using negative-tone Au nanomembrane-based micro/nanolithography Micro-tunnels underneath an Au nanomembrane were fabricated as shown in Figure S20. An array of micro-scaled trenches on an Au nanomembrane was manufactured by conventional photolithography using a positive PR, as shown in Figure S20(a). The individual trench of a positive PR was 3 m in width and 1 m in height. As a next step, a 200 nm-thick Au film was thermally deposited [Figure S20(b)]. After lifting off the positive PR, an array of Au levees were obtained as shown in Figure S20(c). Because the positive PR was dissolved by KOH, Au levees were necessary for etching an Al layer underneath the Au membrane without spreading [Figure S20(d)]. By dropping 1 M KOH onto the Au nanomembrane for 1 2 min and sequential washing of the sample, an array of micro-tunnels surrounded by all solids (Au-Alglass) could be obtained, as shown in Figure S20(e). Figure S20 Scheme of the fabrication process for micro-tunnels using negative-au nanomembrane-based micro/nanolithography. 31