Supplementary Information

Atomic-Scale Dynamic Observation Reveals

Temperature-Dependent Multistep Nucleation

Pathways in Crystallization

Junjie Lia,b

*, Yunping Lic, Qiang Li

d, Zhongchang Wang

e, Francis Leonard Deepak

a*

a Nanostructured Materials Group, Department of Advanced Electron Microscopy, Imaging and

Spectroscopy, International Iberian Nanotechnology Laboratory (INL), Avenida Mestre Jose

Veiga, Braga 4715-330, Portugal

b CAS Key Laboratory of Functional Materials and Devices for Special Environments, Xinjiang

Technical Institute of Physics & Chemistry, CAS; Xinjiang Key Laboratory of Electronic

Information Materials and Devices, 40-1 South Beijing Road, Urumqi 830011, China.

c State Key Lab for Powder Metallurgy, Central South University, Changsha 410083, China

d School of Mechanical Engineering, University of Shanghai for Science and Technology,

Shanghai 200093, China

e Department of Quantum and Energy Materials, International Iberian Nanotechnology

Laboratory (INL), Avenida Mestre Jose Veiga, 4715-330 Braga, Portugal

Email: junjie.li@inl.int and leonard.francis@inl.int

Electronic Supplementary Material (ESI) for Nanoscale Horizons.This journal is © The Royal Society of Chemistry 2019

Experimental Section

Sample preparation and characterization: A molten salt route was used to prepare the

SrBi2Ta2O9 (SBTO) nanoplatelets1. In a typical synthesis process, the stoichiometric strontium

nitrate (Sr(NO3)2, 99.5%), bismuth oxide (Bi2O3, 99.9%) and tantalum oxide (Ta2O5, 99.9%)

were used as starting materials. 1.1g starting materials were mixed with 1.240 g potassium

chloride (KCl, 99.9%) and 0.974 g sodium chloride (NaCl, 99.9%) in an agate mortar for 0.5 h.

The mixtures were loaded into an alumina crucible and heated at 850oC for 3 h in air, followed

by natural cooling to room temperature in a tube furnace. The resultant white samples were

washed with deionized water three times to remove the KCl and NaCl solvent, and dried at 60°C

for 2 h in an oven. The chemical composition of the obtained products was identified by powder

X-ray diffraction (XRD) (X’Pert PRO diffractometer, PANalytical).

In-situ TEM/STEM observation and EDS analysis: The obtained SBTO samples were dispersed

in ethanol by ultrasonication for 1 h, and a drop of the white suspension was transferred onto

carbon support or heating device. TEM/STEM imaging and EDS mapping were carried out on

the Titan Themis TEM equipped with both probe and image Cs corrector and super-X EDS

detector at 200 kV, which offered an unprecedented opportunity to probe ultra-small structures

with sub-Ångström resolution. The heating experiments were carried out in the TEM using a

disposable, micro-electromechanical system (MEMS) device which serves as both support grid

for the sample and the heating element by connecting the heating stage to an external power

supply2,3

. The Videos were recorded using Tecnai Imaging and Analysis (TIA) software.

The calculations of electron beam induced temperature rise at different electron doses in

TEM.

The electron dose induced maximum temperature rise based on the Bethe theory and Fisher’s

model4,5

,

Δ T =𝐼 𝛥 𝐸 𝑎2

4 𝑘 𝑑 (1 + 2 ln

b

𝑎)

where Δ T represents the temperature rise induced by electron beam, I is the beam dose, ĸ is

thermal conductivity, Δ E is energy loss of per electron, d is the thickness of sample, b and a

represent the radius of conductor and beam radius, respectively. In the thin sample, the electron

energy loss is small even for electrons ~200 keV6. Here, the energy loss per electron is

considered as 6.41×10-16 J, ĸ =1.0 W/K/m7-8

, d = 20 nm, b = 300 nm. For the electron dose of

25000 e/A2S in Figure 1, the temperature rise Δ T is about 208 K, 187 K and 41 K for Figure 2

and 3. The room temperature is kept at 20 oC. Therefore, the calculated temperatures (T = Δ T +

Trm) of the Bi nanoparticles in Figure 1 to 3 heated by electron beam are about 228 oC, 207

oC,

and 61 oC , respectively.

References

1. Y. Li, et al. Chem. Mater. 2013, 25, 2045-2050.

2. J. Li, Z. Wang, F. L. Deepak, J. Phys. Chem. Lett. 2018, 9, 961-969.

3. M. A. Asoro, D. Kovar, P. J. Ferreira, ACS nano 2013, 7, 7844-7852.

4. H.A. Bethe, Handbuch der Physik. vol. 4, 273, Julius Springer (Berilin) (1933).

5. Fisher, S. On the temperature rise in electron irradiated foils. Radiat. Eff. 5, 239-243 (1970).

6. Kim, G.-S. et al. Reduction in thermal conductivity of Bi thin films with high-density ordered

nanoscopic pores. Nanoscale Res. Lett. 8, 371 (2013).

7. Song, D. et al. Thermal conductivity of nanoporous bismuth thin films. Appl. Phys. Lett. 84,

1883-1885 (2004).

8. Tachibana, M. Thermal conductivity of Aurivillius compounds Bi2WO6, SrBi2Ta2O9, and

Bi4Ti3O12. Solid State Commun. 211, 1-3 (2015).

Supplementary Figure 1. XRD analysis. XRD results for the obtained powder samples

revealing the successful preparation of pure SrBi2Ta2O9 with an orthorhombic structure (JCPDS

card no. 05-0519).

10 20 30 40 50 60 70 80 90 100 110 120

(4

2 1

4)

(3

3 1

7)

(0

0 1

0)

(4

3 7

)

(3

4 0

)

(3

1 1

5)

2 (degree)

(4

2 2

)

(1

1 9

)

(3

3 5

) (

3 1

13

)

(4

0 2

)

(2

0 8

)

(1

1 3

)

(1

1 1

3)

(3

2 0

) (2

2 0

)

(0

0 1

0)

(2

0 1

0)

(3

1 5

)

(2

00

) (

1 1

5)

Inte

nsi

ty (

a.u

.)

Supplementary Figure 2. Morphology of the sample. a,c, Low magnification TEM (a) and

HAADF-STEM (b) images for the obtained SrBi2Ta2O9 product. b,d, High resolution TEM and

HAADF-STEM images confirming the orthorhombic structure of the SrBi2Ta2O9. Inset image in

Figure b is the diffraction pattern, confirming the single crystal structure.

a b

c d

SBTO

SBTO

Supplementary Figure 3. Chemical mapping of Bi nanocrystal on SBTO surface. a,

HAADF- STEM image. b–e, Corresponding energy-dispersive x-ray spectroscopy mapping of

Bi (b), Sr (c), Ta (d), and O (e). f, Corresponding EDS spectrum of the Bi nanocrystal taken in

the area marked by an orange square in a.

0 10 20 30 40

Co

un

ts (

a.u

.)

Energy (kev)

a b c

d e f

HAADF-STEM Bi Sr

Ta O

Bi

Bi Bi

Bi

Cu

Cu

Supplementary Figure 4. Morphology of the segregated Bi nanocrystals. High resolution

TEM image showing the formation of the Bi nanocrystals under electron beam irradiation.

Bi nanocrystal

SBTO

Supplementary Figure 5. Image and line profile for a Bi liquid droplet on SrBi2Ta2O9. a, A

typical HRTEM image of a Bi droplet on surface of SrBi2Ta2O9. b, Line profile showing image

intensity along the arrow in (a), illustrating local ordering.

0 10 20 30 40 50 60120

130

140

150

160

170

180

190

No

rmal

ize

d In

ten

sity

Position perpendicular to interface (nm)

b a

Interface ordering

Interface ordering

Bi droplet

SBTO

Liquid

Interface ordering

Surface ordering

Supplementary Figure 6. Size-dependent melting point of Bi nanocrystal based on the in-

situ heating experiment. Error bar is 1nm in Figure S9a, and the scale bar is 10 nm in Figure

S9b-k.

Supplementary Figure 7. Schematic of the electron beam induced Bi nanocrystal growth

under different electron dose.

Supplementary Figure 8. Fast Fourier transformation (FFT) analyses. Corresponding FFT

analyses during the surface and interface ordering droplet to crystal nucleus two-step nucleation

pathway (Video S1). The green and orange colors indicate the liquid and crystal phases,

respectively.

40.0 s 40.8 s 41.6 s 42.4 s

44.8 s

43.2 s 44.0 s

45.6 s 46.4 s 47.2 s 48.0 s 48.8 s

49.6 s 50.4 s 51.2 s 52.0 s 52.8 s 53.6 s

56.8 s 54.4 s 55.2 s 56.0 s 57.6 s 58.4 s

60.8 s 59.2 s 60.0 s 61.6 s

Supplementary Figure 9. Fast Fourier transformation (FFT) analyses. Corresponding FFT

analyses during the surface and interface ordered droplet-interior local ordered solid structure-

crystal nucleus three-step nucleation pathway (Video S2). The green, blue and orange colors

indicate the local ordered solid and crystal phases, respectively.

35.2 s 33.6 s 36.8 s 38.4 s 40.0 s 41.6 s

43.2 s 46.4 s 44.8 s 48.0 s 49.6 s 51.2 s

52.8 s 57.6 s 54.4 s 56.0 s 60.8 s 59.2 s

68.8 s 67.2 s 65.6 s 64.0 s 62.4 s

Supplementary Figure 10. Fast Fourier transformation (FFT) analyses. Corresponding FFT

analyses during the local ordered cluster structure to crystal nucleus two-step nucleation pathway

(Video S3). The blue and orange colors indicate the local ordered cluster and crystal phases,

respectively.

44.0 s 45.6 s 47.2 s 48.8 s 50.4 s

52.0 s 55.2 s 53.6 s 56.8 s 60.0 s 58.4 s

42.4 s

64.8 s 63.2 s 66.4 s 68.0 s 69.6 s

72.8 s 74.4 s 71.2 s

61.6 s

Supplementary Figure 11. Statistical analyses of nucleation dynamics during the multistep

nucleation pathways. a-c, Statistical analyses of the height as a function of time (Video S1, S2

and S3). The green, blue and red lines in d-f represent liquid, local ordered solid and crystal

phase, respectively.

10 20 30 40 50 600

3

6

9

12

Heig

ht

(nm

)

Time (s)0 20 40 60 80 100

0

3

6

9

He

igh

t (n

m)

Time (s)40 50 60 70

0

3

6

9

Heig

ht

(nm

)

Time (s)

a b c

Video Information

Video S1. Two-step nucleation pathway (surface and interface ordered liquid droplet to crystal

nucleus). The Video plays at 2 times the normal speed. The electron dose rate is ~2.5 ×104 e/Å

2s.

Video S2. Three-step nucleation pathway (surface and interface ordered liquid droplet to interior

ordered structure to crystal nucleus). The Video plays at 2 times the normal speed. The electron

dose rate is ~1.8 ×104 e/Å

2s.

Video S3. Two-step nucleation pathway (local ordered cluster structure to crystal nucleus). The

Video plays at 2 times the normal speed. The electron dose rate is ~5.0 ×103 e/Å

2s.