title: Ultrafast Intrinsic Photoresponse and Direct Evidence of Sub-gap States in Liquid Phase Exfoliated MoS2Thin Films.
abstract: 2-Dimensional structures with swift optical response have several technological advantages, for example they could be used as components of ultrafast light modulators, photo-detectors, and optical switches. Here we report on the fast photo switching behavior of thin films of liquid phase exfoliated MoS2, when excited with a continuous laser of λ = 658 nm (E = 1.88 eV), over a broad range of laser power. Transient photo-conductivity measurements, using an optical pump and THz probe (OPTP), reveal that photo carrier decay follows a bi-exponential time dependence, with decay times of the order of picoseconds, indicating that the photo carrier recombination occurs via trap states. The nature of variation of photocurrent with temperature confirms that the trap states are continuously distributed within the mobility gap in these thin film of MoS2, and play a vital role in influencing the overall photo response. Our findings provide a fundamental understanding of the photo-physics associated with optically active 2D materials and are crucial for developing advanced optoelectronic devices.
authors.affiliation: Department of Physics, Southern Illinois University Carbondale, Carbondale-IL 62901.
authors.forename: Sujoy
authors.initials: S
authors.lastname: Ghosh
authors.affiliation: Department of Physics, Southern Illinois University Carbondale, Carbondale-IL 62901.
authors.forename: Andrew
authors.initials: A
authors.lastname: Winchester
authors.affiliation: Department of Physics, Southern Illinois University Carbondale, Carbondale-IL 62901.
authors.forename: Baleeswaraiah
authors.initials: B
authors.lastname: Muchharla
authors.affiliation: Department of Physics, Southern Illinois University Carbondale, Carbondale-IL 62901.
authors.forename: Milinda
authors.initials: M
authors.lastname: Wasala
authors.affiliation: Department of Physics and Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, PA 16802.
authors.forename: Simin
authors.initials: S
authors.lastname: Feng
authors.affiliation: Department of Physics and Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, PA 16802.
authors.forename: Ana Laura
authors.initials: AL
authors.lastname: Elias
authors.affiliation: Femtosecond Spectroscopy Unit, Okinawa Inst. of Science &Technology, Graduate University, Onna-son, Okinawa, 904 -0495 Japan.
authors.forename: M Bala Murali
authors.initials: MB
authors.lastname: Krishna
authors.affiliation: Femtosecond Spectroscopy Unit, Okinawa Inst. of Science &Technology, Graduate University, Onna-son, Okinawa, 904 -0495 Japan.
authors.forename: Takaaki
authors.initials: T
authors.lastname: Harada
authors.affiliation: Femtosecond Spectroscopy Unit, Okinawa Inst. of Science &Technology, Graduate University, Onna-son, Okinawa, 904 -0495 Japan.
authors.forename: Catherine
authors.initials: C
authors.lastname: Chin
authors.affiliation: Femtosecond Spectroscopy Unit, Okinawa Inst. of Science &Technology, Graduate University, Onna-son, Okinawa, 904 -0495 Japan.
authors.forename: Keshav
authors.initials: K
authors.lastname: Dani
authors.affiliation: Department of Physics and George J. Kostas Research Institute, Northeastern University, Boston, USA.
authors.forename: Swastik
authors.initials: S
authors.lastname: Kar
authors.affiliation: 1] Department of Physics and Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, PA 16802 [2] Department of Chemistry and Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802.
authors.forename: Mauricio
authors.initials: M
authors.lastname: Terrones
authors.affiliation: 1] Department of Physics, Southern Illinois University Carbondale, Carbondale-IL 62901 [2] Femtosecond Spectroscopy Unit, Okinawa Inst. of Science &Technology, Graduate University, Onna-son, Okinawa, 904 -0495 Japan.
authors.forename: Saikat
authors.initials: S
authors.lastname: Talapatra