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Ultrafast Intrinsic Photoresponse and Direct Evidence of Sub-gap States in Liquid Phase Exfoliated MoS2Thin Films.

Ghosh S, Winchester A, Muchharla B, Wasala M, Feng S, Elias AL, Krishna MB, Harada T, Chin C, Dani K, Kar S, Terrones M, Talapatra S - Sci Rep (2015)

Bottom Line: 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.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.Our findings provide a fundamental understanding of the photo-physics associated with optically active 2D materials and are crucial for developing advanced optoelectronic devices.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Southern Illinois University Carbondale, Carbondale-IL 62901.

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.

No MeSH data available.


Related in: MedlinePlus

Temperature dependence of photocurrent.Temperature dependence of photocurrent and dark current as seen in thin film MoS2 photo-detectors. A maximum of photocurrent at high temperatures (inset) as well as higher value of photocurrent compared to dark current at lower temperatures.
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f4: Temperature dependence of photocurrent.Temperature dependence of photocurrent and dark current as seen in thin film MoS2 photo-detectors. A maximum of photocurrent at high temperatures (inset) as well as higher value of photocurrent compared to dark current at lower temperatures.

Mentions: In order to understand how the trap states control the photocurrent of these devices over a wide range of temperature, we have measured the dependence of Iph with temperature (25 K < T <320 K) by applying a DC bias of 500 mV, under a constant illumination (λ = 633 nm, E = 1.95 eV) at 575 μW. The data is presented in Fig. 4, where ln(Iph) is plotted as a function of 1/T and it is compared with the value of Idark. Several interesting features of Iph can be seen from this measurement. Firstly, depending on the measurement temperatures, two distinct regions for Iph can be identified: Region I (T <120 K; where Iph> Idark) and Region II (T >120 K; where Iph< Idark). Secondly, at low temperatures (T <50 K), Iph is constant and thirdly, in Region II (T >120 K), Iph shows a maxima at T = Tmax ~ 280 K.


Ultrafast Intrinsic Photoresponse and Direct Evidence of Sub-gap States in Liquid Phase Exfoliated MoS2Thin Films.

Ghosh S, Winchester A, Muchharla B, Wasala M, Feng S, Elias AL, Krishna MB, Harada T, Chin C, Dani K, Kar S, Terrones M, Talapatra S - Sci Rep (2015)

Temperature dependence of photocurrent.Temperature dependence of photocurrent and dark current as seen in thin film MoS2 photo-detectors. A maximum of photocurrent at high temperatures (inset) as well as higher value of photocurrent compared to dark current at lower temperatures.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4502394&req=5

f4: Temperature dependence of photocurrent.Temperature dependence of photocurrent and dark current as seen in thin film MoS2 photo-detectors. A maximum of photocurrent at high temperatures (inset) as well as higher value of photocurrent compared to dark current at lower temperatures.
Mentions: In order to understand how the trap states control the photocurrent of these devices over a wide range of temperature, we have measured the dependence of Iph with temperature (25 K < T <320 K) by applying a DC bias of 500 mV, under a constant illumination (λ = 633 nm, E = 1.95 eV) at 575 μW. The data is presented in Fig. 4, where ln(Iph) is plotted as a function of 1/T and it is compared with the value of Idark. Several interesting features of Iph can be seen from this measurement. Firstly, depending on the measurement temperatures, two distinct regions for Iph can be identified: Region I (T <120 K; where Iph> Idark) and Region II (T >120 K; where Iph< Idark). Secondly, at low temperatures (T <50 K), Iph is constant and thirdly, in Region II (T >120 K), Iph shows a maxima at T = Tmax ~ 280 K.

Bottom Line: 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.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.Our findings provide a fundamental understanding of the photo-physics associated with optically active 2D materials and are crucial for developing advanced optoelectronic devices.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Southern Illinois University Carbondale, Carbondale-IL 62901.

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.

No MeSH data available.


Related in: MedlinePlus