Supplementary

Orienting MoS2 flakes into ordered films

S. Appel1,2, A. Volman1,2, L. Houben3, Y. Gelbstein2, M. Bar Sadan1,*

1 Chemistry Department, Ben-Gurion University of the Negev

2 Materials Engineering Department, Ben-Gurion University of the Negev

3 Peter Grünberg Institut 5 and Ernst Ruska Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany

* Corresponding author

XRD pattern of all ball milled MoS2 samples

Fig. S1. MoS2 powder XRD patterns for the six samples depicted in Fig. 1: the pristine MoS2 powder and the five ball milled samples (2-48 h).

Measuring lattice parameters of ball milled MoS2 samples:

Bragg-Brentano detector configuration is such that the higher the diffraction angle, the less the equipment is prone to shifts in instrumental parameters. To reduce that source of potential instrumental error, diffractions from the ball milled samples were conducted at angles ranging from 10-110°. After calibration with an Al2O3 reference sample, the instrumental angle shift was found to be ±0.02°. The process of ball milling at 400 rpm did not create a secondary crystallographic structure of 3R-MoS2. Between 85-110° the two highest peaks of 2H-MoS2 were found to be reflections 118 and 213 at angles of about 88.7° and 100.3°, respectively. Bragg's equation and the formula for the inter-planar distance of the hexagonal lattice: gave the experimental values for the lattice parameters a and c (shown in Table S1).


Table S1. Calculated values of the lattice parameters of the pristine and ball milled samples:

a [nm] / div a [%] / c [nm] / div c [%]
no ball milling / 0.27 / ±0.00 / 1.22 / ±0.00
2 h / 0.27 / ±0.02 / 1.23 / ±0.06
3 h / 0.27 / ±0.02 / 1.23 / ±0.03
12 h / 0.27 / ±0.00 / 1.23 / ±0.03
24 h / 0.27 / ±0.00 / 1.22 / ±0.00
48 h / 0.27 / ±0.02 / 1.23 / ±0.03

Throughout the entire ball milling process, the lattice parameters remain relatively unchanged since the changes measured in lattice parameters are smaller than the instrument's error limit. This also rules out the intercalation of H2O molecules within the samples and the formation of oxides during the process.

Fig. S2. High angle MoS2 powder XRD patterns for the six samples depicted in Fig. 1: the pristine MoS2 powder and the five ball milled samples (2-48 h).

Fig. S3. XRD patterns of MoS2 ball milled for 3 h at 400 rpm: powder (red), exfoliated and restacked on a Si wafer (black)

Fig. S4. XRD patterns of MoS2 pellets: without thermal treatment (black), after 24 h at 300 °C (red), after 72 h at 300 °C (blue).

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