High Luminescence Efficiency in MoS2 Grown by Chemical Vapor Deposition.
One of the major challenges facing the rapidly growing field of two-dimensional (2D) transition metal dichalcogenides (TMDCs) is the development of growth techniques to enable large-area synthesis of high-quality materials. Chemical vapor deposition (CVD) is one of the leading techniques for the synthesis of TMDCs; however, the quality of the material produced is limited by defects formed during the growth process. A very useful nondestructive technique that can be utilized to probe defects in semiconductors is the room-temperature photoluminescence (PL) quantum yield (QY). It was recently demonstrated that a PL QY near 100% can be obtained in MoS2 and WS2 monolayers prepared by micromechanical exfoliation by treating samples with an organic superacid: bis(trifluoromethane)sulfonimide (TFSI). Here we have performed a thorough exploration of this chemical treatment on CVD-grown MoS2 samples. We find that the as-grown monolayers must be transferred to a secondary substrate, which releases strain, to obtain high QY by TFSI treatment. Furthermore, we find that the sulfur precursor temperature during synthesis of the MoS2 plays a critical role in the effectiveness of the treatment. By satisfying the aforementioned conditions we show that the PL QY of CVD-grown monolayers can be improved from ∼0.1% in the as-grown case to ∼30% after treatment, with enhancement factors ranging from 100 to 1500× depending on the initial monolayer quality. We also found that after TFSI treatment the PL emission from MoS2 films was visible by eye despite the low absorption (5-10%). The discovery of an effective passivation strategy will speed the development of scalable high-performance optoelectronic and electronic devices based on MoS2.
Electrical Engineering and Computer Sciences, University of California at Berkeley , Berkeley, California 94720, United States.|Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
Matin
M
Amani
U.S. Army Research Laboratory , 2800 Powder Mill Road, Adelphi, Maryland 20783, United States.
Robert A
RA
Burke
Electrical Engineering and Computer Sciences, Massachusetts Institute of Technology , 77 Mass Avenue, Cambridge, Massachusetts 02139, United States.
Xiang
X
Ji
Electrical Engineering and Computer Sciences, University of California at Berkeley , Berkeley, California 94720, United States.|Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
Peida
P
Zhao
Electrical Engineering and Computer Sciences, University of California at Berkeley , Berkeley, California 94720, United States.|Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
Der-Hsien
DH
Lien
Electrical Engineering and Computer Sciences, University of California at Berkeley , Berkeley, California 94720, United States.
Peyman
P
Taheri
Electrical Engineering and Computer Sciences, University of California at Berkeley , Berkeley, California 94720, United States.|Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
Geun Ho
GH
Ahn
Electrical Engineering and Computer Sciences, University of California at Berkeley , Berkeley, California 94720, United States.|Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
Daisuke
D
Kirya
Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
Joel W
JW
Ager
Electrical Engineering and Computer Sciences, University of California at Berkeley , Berkeley, California 94720, United States.|Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
Eli
E
Yablonovitch
Electrical Engineering and Computer Sciences, Massachusetts Institute of Technology , 77 Mass Avenue, Cambridge, Massachusetts 02139, United States.
Jing
J
Kong
U.S. Army Research Laboratory , 2800 Powder Mill Road, Adelphi, Maryland 20783, United States.
Madan
M
Dubey
Electrical Engineering and Computer Sciences, University of California at Berkeley , Berkeley, California 94720, United States.|Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
Ali
A
Javey
MoS2; biexcitonic recombination; chemical vapor deposition; quantum yield; radiative lifetime; transition metal dichalcogenide