chemical vapour deposition of zeolitic imidazolate framework … · 2016-02-24 · 1 supplementary...

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Supplementary information accompanying

Chemical vapour deposition of zeolitic imidazolate framework thin films

Ivo Stassen1,2, Mark Styles3, Gianluca Grenci4, Hans Van Gorp5, Willem Vanderlinden5, Steven De Feyter5, Paolo Falcaro3, Dirk De Vos1, Philippe Vereecken1,2, Rob Ameloot1*

1Department of Microbial and Molecular Systems, Centre for Surface Chemistry and Catalysis, KU Leuven – University of Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium. 2imec, Kapeldreef 75,

B-3001 Leuven, Belgium. 3CSIRO Manufacturing Flagship, Clayton, Victoria 3168, Australia. 4MBI, National University of Singapore T-Lab, 5A Engineering Drive 1, Singapore. 5Department of Chemistry,

KU Leuven – University of Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium.

*To whom correspondence should be addressed: [email protected]

Contents

1. Photographs .................................................................................................................................. 3

2. X-ray diffraction ............................................................................................................................. 4

3. ATR-FTIR ........................................................................................................................................ 6

4. Scanning electron microscopy ....................................................................................................... 7

5. Atomic force microscopy ............................................................................................................... 9

6. Cross-sectional analysis by FIB-TEM ............................................................................................ 12

7. EDS cross-sectional line scan ....................................................................................................... 13

8. TOF-SIMS analysis ........................................................................................................................ 14

9. Surface roughness evolution of zinc oxide films before and during reaction ............................. 17

10. Influence of the substrate on coverage and adhesion ................................................................ 19

11. Cross-sectional FIB-TEM for verification of ZIF-8 film thickness calculated from BET ................ 20

12. Krypton physisorption isotherms of samples used for adsorption kinetics experiment ............ 21

Chemical vapour deposition of zeolitic imidazolateframework thin films

SUPPLEMENTARY INFORMATIONDOI: 10.1038/NMAT4509

NATURE MATERIALS | www.nature.com/naturematerials 1

© 2015 Macmillan Publishers Limited. All rights reserved

http://dx.doi.org/10.1038/nmat4509

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13. Krypton physisorption after additional vapour-solid reaction .................................................... 22

14. In situ powder X-ray diffraction ................................................................................................... 23

15. Proposed structure for HT-HmIM phase ..................................................................................... 27

16. Influence of increased temperature on film morphology ........................................................... 31

17. Exploratory experiments with altered ligands, metals and topologies....................................... 32

18. Lift-off patterning of ZIF-8 ........................................................................................................... 35

19. ZIF-8 coated elastomeric pillar arrays ......................................................................................... 36

20. References ................................................................................................................................... 37


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1. Photographs

Figure 1. Photographs of ALD zinc oxide films with different thicknesses, before (a) and after (b) 30

min vapour-solid reaction with HmIM. ZnO thicknesses are estimated from the per cycle ALD growth

rate. ZIF-8 thickness estimations are averaged thicknesses from TEM cross sections (Supplementary

Section 6).


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2. X-ray diffraction

Figure 2. X-ray diffraction of 15 nm zinc oxide film before and after 30 min vapour-solid reaction

with HmIM.

Figure 3. X-ray diffraction of 6 nm zinc oxide film before and after 30 min vapour-solid reaction with

HmIM.


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Figure 4. X-ray diffraction of 3 nm zinc oxide film before and after 30 min vapour-solid reaction with

HmIM.


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3. ATR-FTIR

Figure 5. ATR-FTIR spectra of a 2-methylimidazole (HmIM) powder sample, a reference HmIM film

deposited on a titanium oxide substrate by physical vapour deposition, ZIF-8 films resulting from 30

min vapour-solid reaction of a 6 nm zinc oxide film on a titanium oxide substrate, after vapour-solid

reaction, after a subsequent activation step at 110°C under nitrogen flow for 10 min to remove possible

unreacted ligand and a ZIF-8 powder sample synthesized using a literature procedure1. Peak

identification is based on literature2. Note that the C-C, C=C and C=N bonds in the region between 1000

and 1600 cm-1 are clearly observed in the ZIF-8 film and no peaks related to the N-H bond are observed.

The additional peaks in the fingerprint region relative to the powder reference have previously been

observed for ZIF-8 in literature.3–5 The HmIM PVD reference sample was prepared by suspending a room

temperature reference sample for 2 minutes in a reactor vessel containing a HmIM powder bed

preheated at 120°C.


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4. Scanning electron microscopy

Figure 6. SEM cross-sectional imaging of 15 nm zinc oxide film after 30 min vapour-solid reaction

with HmIM. a, tilted view. b, perpendicular view. Scale bars 1 µm.

Figure 7. SEM cross-sectional imaging of 6 nm zinc oxide film after 30 min vapour-solid reaction with

HmIM. a, tilted view. b, perpendicular view. Scale bars a, 2 µm and b, 500 nm.


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Figure 8. SEM cross-sectional imaging of 3 nm zinc oxide film after 30 min vapour-solid reaction with

HmIM. a, tilted view. b, perpendicular view. Scale bars a, 1 µm and b, 500 nm.


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5. Atomic force microscopy

Figure 9. AFM analysis of 15 nm zinc oxide film after 30 min vapour-solid reaction with HmIM.

Surface roughness calculated over 2 × 2 µm area: Ra = 26.0 nm; Rq = 31.3 nm. Axes top: X and Y [-1, 1

µm], Z [0 nm, 200 nm], axes bottom: X and Y [-250, 250 nm], Z [0 nm, 100 nm], scale bars 500 nm (top)

and 100 nm (bottom).


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Figure 10. AFM analysis of 6 nm zinc oxide film after 30 min vapour-solid reaction with HmIM. Surface

roughness calculated over 2 × 2 µm area: Ra = 24.9 nm; Rq = 32.5 nm. Axes top: X and Y [-1, 1 µm], Z [0

nm, 200 nm], axes bottom: X and Y [-250, 250 nm], Z [0 nm, 125 nm], scale bars 500 nm (top) and 100

nm (bottom).


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Figure 11. AFM analysis of 3 nm zinc oxide film after 30 min vapour-solid reaction with HmIM. Surface

roughness calculated over 2 × 2 µm area: Ra = 15.1 nm; Rq = 20.1 nm. Axes top: X and Y [-1, 1 µm], Z [0

nm, 100 nm], axes bottom: X and Y [-250, 250 nm], Z [0 nm, 25 nm], scale bars 500 nm (top) and 100

nm (bottom).


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6. Cross-sectional analysis by FIB-TEM

Figure 12. TEM cross section of 15 nm zinc oxide film after 30 min vapour-solid reaction with HmIM.

The average thickness of the film over the full range of the cross section is ca. 124 nm.






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7. EDS cross-sectional line scan

Figure 15. Energy dispersive X-ray spectroscopy cross-sectional line scan of the interface of titanium

oxide and ZIF-8. a, HAADF cross sectional image showing the line profile that was analysed. b, Atomic

concentration profiles of carbon, nitrogen, zinc, oxygen and titanium in the film calculated from the

EDS signals.


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8. TOF-SIMS analysis

Figure 16. TOF-SIMS surface spectrum of ZIF-8 film obtained by 30 min vapour-solid reaction

transformation of a 3 nm ALD zinc oxide film.

Table 1: TOF-SIMS surface spectrum peak identification

Ion Mass (u) Counts

H+ 1.0074 19471

CH3+ 15.0231 37703

Si+ 27.975 138982

CH2N+ 28.0201 33740

C2H5+ 29.0395 123611

CH4N+ 30.0368 13338

CH3O+ 31.0186 5539

K+ 38.9639 1374

C3H3+ 39.0225 74745

C3H5+ 41.0395 198536

C2H4N+ 42.0362 137272


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C4H3+ 51.0227 17816

C3H4N+ 54.0367 57255

64Zn+/TiO+ 63.9295 40278

68Zn+ 67.9257 17217

C4H4N2+ 80.0468 14779

C4H5N2+ 81.0475 152411

C4H6N2+ 82.0554 138546

C4H7N2+ 83.0617 165583


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Figure 17. TOF-SIMS depth profile of a ZIF-8 film on a TiOx substrate obtained by 30 min vapour-solid

reaction transformation of a 3 nm ALD zinc oxide film. Ions from the ZIF-8 film are observed roughly in

the first 400 s of the measurement. The HmIM signal is an accumulated signal for all C4N2 containing

fragments. The 64Zn+ signal showed a partial overlap with the TiO+ signal and could not be fully

resolved. The gradual signal increase in the ZIF-8 film is hence mainly attributed to an increase in TiO+

ions sputtered from the substrate. The HmIM and 68Zn+ signals do not indicate major fluctuations of 2-

methylimidazole and zinc in the film and at the interface with the titanium oxide substrate.


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9. Surface roughness evolution of zinc oxide films before and during

reaction

Figure 18. AFM analysis of ALD zinc oxide films with different thicknesses: a, 3 nm, b, 6 nm, c, 15 nm.

Surface roughness calculated over 2 × 2 µm area: a, Ra = 1.07 nm; Rq = 1.37 nm, b, Ra = 1.54 nm; Rq =

1.97 nm, c, Ra = 1.34 nm; Rq = 1.66 nm. Axes: X and Y [-1, 1 µm], Z [-5 nm, 5 nm], scale bars 500 nm.


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Figure 19. Surface roughness of a 6 nm zinc oxide film during vapour-solid reaction with HmIM for

different times. AFM topographs after a, 120 s, b, 200 s, c, 300 s and d, 600 s vapour-solid reaction. e,

Evolution of the average surface roughness calculated for 2 × 2 µm areas (with standard deviations,

calculated for measurement of 9 different areas on each sample). Axes: X and Y [-1, 1 µm], Z [-5 nm, 5

nm] (a), [-25 nm, 25 nm] (b), [-50 nm, 50 nm] (c and d).


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10. Influence of the substrate on coverage and adhesion

Figure 20. SEM images of ZIF-8 films on different substrates after 30 min vapour-solid reaction with

HmIM. Substrates: a, 6 nm zinc oxide on titanium oxide, b, 6 nm zinc oxide on silicon oxide and c, zinc

oxide (50 nm, partial conversion). Scale bars: 2 µm.


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11. Cross-sectional FIB-TEM for verification of ZIF-8 film thickness

calculated from BET

Figure 21. TEM cross section of ZIF-8 film obtained by 30 min vapour-solid reaction of a 50 nm zinc

oxide film. The average thickness of the film over the full range of the cross section is ca. 71 nm. The

thickness calculated from the BET surface area of an equivalent MOF-CVD pillar array is 59 nm.


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12. Krypton physisorption isotherms of samples used for adsorption

kinetics experiment

Figure 22. Krypton adsorption isotherms (absolute sample uptake) measured at 77K for the flat (blue

crosses) and coated pillar array (red diamonds) samples used for single-pulse krypton adsorption

kinetics experiment. Insets show SEM cross sections of both samples and an indication of the average

film thickness that was calculated from the respective isotherms (2500 nm and 85 nm for the flat film

and coated pillar array, respectively).


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13. Krypton physisorption after additional vapour-solid reaction

Figure 23. Krypton adsorption isotherms measured at 77 K for pillar array samples after an additional

15 min vapour-solid reaction with HmIM. The initial isotherms of the samples are displayed in the main

paper (Fig. 3f). 15+15 min (red crosses), 30+15 min (blue diamonds) and 45+15 min (yellow squares)

vapour-solid reaction with HmIM.

Table 2. BET specific surface area of the films before and after the additional reaction time.

Sample BET (m² m-²) BET after additional 15 min reaction (m² m-²) [change]

15 min CVD 41 59 [+ 44 %]

30 min CVD 74 73 [- 1 %]

45 min CVD 88 91 [+ 3 %]


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14. In situ powder X-ray diffraction

Figure 24. Time-resolved diffractograms (3D plot and 2D heat map) showing the transformation of

crystalline phases in a 1:2 stoichiometric physical mixture of crystalline zinc oxide and HmIM powder

at 130 °C. Temperature program: room temperature to 130 °C from 0 to 12.2 min, 130 °C to room

temperature starting from 72.2 min.


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at 115°C. Temperature program: room temperature to 115 °C from 0 to 10.6 min, 115 °C to room

temperature starting from 70.6 min.


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at 115°C under humid nitrogen flow. Temperature program: room temperature to 115 °C from 0 to

10.2 min, 115 °C to room temperature starting from 70.2 min.


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at 115°C under dry nitrogen flow. Temperature program: room temperature to 115 °C from 0 to 10.2

min, 115 °C to room temperature starting from 68.2 min.


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15. Proposed structure for HT-HmIM phase

The crystal structure of 2-methylimidazole at room temperature (LT-HmIM) has been reported by Hachula et al.2, and the structure is shown in Figure 16 a and b. The space group of LT-HmIM is orthorhombic, P212121. In this study, the refined lattice parameters for this phase at room temperature were a = 6.225 Å, b = 8.166 Å, and c = 9.716 Å, which are slightly larger than those reported by Hachula. As the samples were heated above ~80°C, the HmIM underwent a solid-solid phase transition to a high temperature phase (HT-HmIM). The peaks were indexed to the space group Fdd2, with lattice parameters a = 16.278 Å, b = 12.605 Å, and c = 4.894 Å at a temperature of ~90°C. To the authors’ best knowledge, this phase has not

been reported before. An attempt was made to determine the structure of the HT-HmIM phase from the in situ XRD data, using a simulated annealing approach combined with a rigid body representation of the HmIM molecule derived from the LT-HmIM phase. The crystal structure model which produced the best agreement with the observed data is shown in Figure S26 c and d (the agreement with the diffraction data is shown in Figure 17). Viewed down the c axis of the unit cell, the HT-HmIM phase has a similar stacking arrangement to the LT-HmIM phase. However, the orientation of the HmIM molecules on the lattice site is now disordered, with 50% of the molecules facing one direction, and the other 50% rotated by 180° as a result of the symmetry of the space group. In reality, only one molecule can sit on each site and, due to thermal vibrations, will likely adopt a range of orientations about the plane of the molecule, resulting in an averaging of the electron density observed by XRD. A detailed study of the phase transitions in pure 2-methylimidazole is currently underway and will be reported elsewhere, however, the atomic co-ordinates for the HT-HmIM phase are given in Table 3.


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Figure 28. HmIM crystalline phases. LT-HmIM crystal structure reported by Hachuła, viewed along a) the c axis, and b) the b axis. Note the regular alternation of the HmIM molecule along the c direction in the LT-HmIM phase. The preliminary crystal structure for the HT-HmIM phase based on the in situ XRD data, viewed along c) the c axis, and d) the b axis. In this case, the HmIM molecules no-longer regularly alternate along the c direction, and instead adopt a more random orientation about the plane of the molecule. A column of HmIM molecules are highlighted in brown in d).


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Figure 29. Comparison between the observed (blue) and calculated (red) diffraction patterns for the HT-HmIM phase (difference shown in grey), obtained using the preliminary structure reported in Table 3.


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Table 3 Crystal structure parameters for the HT-HmIM phase, determined from the in situ XRD data. Site occupation factors were set to 50%, to achieve a realistic density. Atomic displacement parameters (Beq) were not refined due to limited number of peaks observed at high diffraction angles.

Phase HT-HmIM Space

group

Fdd2

a 16.278 Å b 12.605 Å c 4.894 Å Density 1.09 g/cm3

Site Atom x y z Occupanc

y Beq (Å2)

1 C 0.08035

0.39482

0.97884 0.5 4.0

2 C 0.02650

0.49372

0.98150 0.5 4.0

3 C 0.95063

0.62984

0.10806 0.5 4.0

4 C 0.95076

0.63056

0.82850 0.5 4.0

5 N 0.99830

0.54348

0.20387 0.5 4.0

6 N 0.99928

0.54365

0.75120 0.5 4.0

7 H 0.04685

0.32828

0.00385 0.5 4.0

8 H 0.10923

0.39112

0.80335 0.5 4.0

9 H 0.12047

0.39994

0.12768 0.5 4.0

10 H 0.01044

0.51887

0.58758 0.5 4.0

11 H 0.92295

0.68093

0.71157 0.5 4.0

12 H 0.92214

0.68086

0.21967 0.5 4.0


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16. Influence of increased temperature on film morphology

Figure 30. SEM images of 15 nm zinc oxide film after 30 min vapour-solid reaction at 100 °C (a, c) and

120 °C (b, c). The film resulting from the reaction at 100°C is thicker and less confined to the substrate.

Scale bars: 2 µm for a-b and 1 µm for c-d.


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17. Exploratory experiments with altered ligands, metals and

topologies

Figure 31. X-ray diffraction of 10 nm cobalt (II) oxide film after 1 h vapour-solid reaction with HmIM

at 120°C. The obtained material matches the ZIF-67 (CCDC GITTOT) framework.

Figure 32. X-ray diffraction of 15 nm zinc oxide film after 12 h vapour-solid reaction with 4,5-

dichloroimidazole (HdcIM) at 90°C. The obtained material matches the ZIF-72 (CCDC GIZJUV)

framework.


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Figure 33. X-ray diffraction of 50 nm zinc oxide film after 12 h vapour-solid reaction with 2-

trifluoromethyl-1H-imidazole (HtFmIM) at 100°C. The obtained material matches the CCDC EHETER

framework.

Figure 34. X-ray diffraction of 15 nm zinc oxide film after 12 h vapour-solid reaction with 1H-imidazole

(HIM) at 90°C. The obtained material matches the ZIF-61 (CCDC GITTAF) framework..


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Figure 35. X-ray diffraction of copper hydroxide film after 12 h vapour-solid reaction with fumaric acid

(HFUM) at 250°C. The obtained material matches the CCDC NIFMIY coordination polymer.

Figure 36. X-ray diffraction of copper hydroxide film after 12 h vapour-solid reaction with 1,4-

benzenedicarboxylic acid (HBDC) at 250°C. The obtained material demonstrates a reasonable similarity

with literature coordination polymers (CCDC BIGDIF and KEQTEF).


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18. Lift-off patterning of ZIF-8

Figure 37. ZIF-8 pattern, 25 µm dots with 100 µm interspacing, obtained by ZIF-8 vapour deposition

and lift-off patterning. a, optical microscopy image. b and c, SEM images. d, Surface profile obtained

by stylus profilometry (Bruker DektakXT), showing the film thickness of approximately 120 nm. Scale

bars: 100 µm for a and b, 10 µm for c.

Lift-off patterning or additive photolithography of in situ grown MOF films has previously not been demonstrated in literature. Related concepts that have been demonstrated include: subtractive (etch) photolithography6, lift-off patterning of ex situ synthesized and subsequently deposited crystals7 and soft lithography microcontact printing8.


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19. ZIF-8 coated elastomeric pillar arrays

Figure 38. Polydimethylsiloxane pillar array before (a and c) and after (b and d) ZIF-8 vapour

deposition. Scale bars: 1 µm for a and b, 5 µm for c and d.


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20. References

1. Cravillon, J. et al. Rapid Room-Temperature Synthesis and Characterization of Nanocrystals of a Prototypical Zeolitic Imidazolate Framework. Chem. Mater. 21, 1410–1412 (2009).

2. Hachuła, B., Nowak, M. & Kusz, J. Crystal and molecular structure analysis of 2-methylimidazole. J. Chem. Crystallogr. 40, 201–206 (2010).

3. Hu, Y., Kazemian, H., Rohani, S., Huang, Y. & Song, Y. In situ high pressure study of ZIF-8 by FTIR spectroscopy. Chem. Commun. 47, 12694 (2011).

4. Ordoñez, M. J. C., Balkus, K. J., Ferraris, J. P. & Musselman, I. H. Molecular sieving realized with ZIF-8/Matrimid® mixed-matrix membranes. J. Memb. Sci. 361, 28–37 (2010).

5. Eslava, S. et al. Metal-Organic Framework ZIF-8 Films As Low-κ Dielectrics in Microelectronics. Chem. Mater. 25, 27–33 (2013).

6. Lu, G., Farha, O. K., Zhang, W., Huo, F. & Hupp, J. T. Engineering ZIF-8 thin films for hybrid MOF-based devices. Adv. Mater. 24, 3970–4 (2012).

7. Hod, I. et al. Directed growth of electroactive metal-organic framework thin films using electrophoretic deposition. Adv. Mater. 26, 6295–300 (2014).

8. Ameloot, R. et al. Direct Patterning of Oriented Metal-Organic Framework Crystals via Control over Crystallization Kinetics in Clear Precursor Solutions. Adv. Mater. 22, 2685–2688 (2010).


chemical vapour deposition of zeolitic imidazolate framework … · 2016-02-24 · 1 supplementary...

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