Characterization of metal contacts for two-dimensional MoS2
nanoflakes
Sumeet Walia,1,2,a) Sivacarendran Balendhran,1,2 Yichao Wang,2 Rosmalini Ab Kadir,2
Ahmad Sabirin Zoolfakar,2 Paul Atkin,2 Jian Zhen Ou,2 Sharath Sriram,1,2 Kourosh Kalantarzadeh2,a) and Madhu Bhaskaran1,2,a)
1
Functional Materials and Microsystems Research Group, RMIT University, Melbourne, Victoria
3000, Australia
2
School of Electrical and Computer Engineering, RMIT University, Melbourne, Victoria 3000,
Australia
MATERIALS AND METHODS
A liquid exfoliation technique was employed to synthesize the two dimensional (2D) MoS2
nanoflake suspension. 0.5 mL of N-methyl-2-pyrrolidone (NMP) (99% anhydrous, Sigma
Aldrich) was added to 1 g of commercial MoS2 powder (99% purity, Sigma Aldrich) and the
mixture was subsequently mechanically ground for 30 min. The mixture was allowed to dry
overnight under ambient conditions. The as-dried mixture was re-dispersed in 40 mL
ethanol/water (1:1) solution. This solution was probe-sonicated (Ultrasonic Processor
GEX500) for 90 min at a power of 125 W and the supernatant containing the exfoliated 2D
MoS2 nanoflakes was separated after being centrifuged for 45 min at the speed of 4000 rpm.
The thickness and lateral dimensions of the 2D MoS2 nanoflakes was assessed using atomic
force microscopy (AFM) (Bruker Multimode 8 with PF TUNA). Additionally, high
resolution transmission electron microscopy (HRTEM) (JEOL 2100F) and Raman
microscopy (Horiba TRIAX 320 spectrometer fiber coupled to an Olympus BX41 confocal
microscope with 532 nm 90 µW excitation) were also employed to further characterize the
2D MoS2 nanoflakes. X-ray diffraction (XRD) was carried out using a Bruker D8
DISCOVER microdiffractometer fitted with a General Area Detector Diffraction System
(GADDS). Data was collected at room temperature using CuK radiation ( = 1.54178 Å)
with a potential of 40 kV and a current of 20 mA, and filtered with a graphite monochromator
in the parallel mode (175 mm collimator with 0.5 mm pinholes). Electrical characteristics
were measured at room temperature using an Agilent B2912A Precision Source/Measure
Unit with voltage sweeps in the range –1 to 2 V.
NOTES
a)
Corresponding authors. E-mail: madhu.bhaskaran@rmit.edu.au, kourosh.kalantar@rmit.edu.au and
sumeet.walia@rmit.edu.au