23,275 research outputs found
Self-Powered, Highly Sensitive, High Speed Photodetection Using ITO/WSe2/SnSe2 Vertical Heterojunction
Two dimensional transition metal di-chalcogenides (TMDCs) are promising
candidates for ultra-low intensity photodetection. However, the performance of
these photodetectors is usually limited by ambience induced rapid performance
degradation and long lived charge trapping induced slow response with a large
persistent photocurrent when the light source is switched off. Here we
demonstrate an indium tin oxide (ITO)/WSe/SnSe based vertical double
heterojunction photoconductive device where the photo-excited hole is confined
in the double barrier quantum well, whereas the photo-excited electron can be
transferred to either the ITO or the SnSe layer in a controlled manner. The
intrinsically short transit time of the photoelectrons in the vertical double
heterojunction helps us to achieve high responsivity in excess of A/W
and fast transient response time on the order of s. A large built-in
field in the WSe sandwich layer results in photodetection at zero external
bias allowing a self-powered operation mode. The encapsulation from top and
bottom protects the photo-active WSe layer from ambience induced
detrimental effects and substrate induced trapping effects helping us to
achieve repeatable characteristics over many cycles
Asymmetrically Encapsulated vertical ITO/MoS2/Cu2O photodetector with ultra-high sensitivity
Strong light absorption, coupled with moderate carrier transport properties,
makes two-dimensional (2-D) layered transition metal dichalcogenide (TMD)
semiconductors promising candidates for low intensity photodetection
applications. However, the performance of these devices is severely
bottlenecked by slow response with persistent photocurrent due to long lived
charge trapping, and nonreliable characteristics due to undesirable ambience
and substrate effects. Here we demonstrate ultra-high specific detectivity (D*)
of 3.2x10^14 Jones and responsivity (R) of 5.77x10^4 AW-1 at an optical power
density (P_op) of 0.26 Wm-2 and external bias (V_ext) of -0.5 V in an indium
tin oxide (ITO)/MoS2/copper oxide (Cu2O)/Au vertical multi-heterojunction
photodetector exhibiting small carrier transit time. The active MoS2 layer
being encapsulated by carrier collection layers allows us to achieve negligible
trap assisted persistent photocurrent and repeatable characteristics over large
number of cycles. We also achieved a large D*>10^14 Jones at zero external bias
due to the built-in field of the asymmetric photodetector. Benchmarking the
performance against existing reports in literature shows a pathway for
achieving reliable and highly sensitive photodetectors for ultra-low intensity
photodetection applications.Comment: Accepted in Small, Wile
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Photochemically Induced Phase Change in Monolayer Molybdenum Disulfide.
Monolayer transition metal dichalcogenide (TMDs) are promising candidates for two-dimensional (2D) ultrathin, flexible, low-power, and transparent electronics and optoelectronics. However, the performance of TMD-based devices is still limited by the relatively low carrier mobility and the large contact resistance between the semiconducting 2D channel material and the contact metal electrodes. Phase-engineering in monolayer TMDs showed great promise in enabling the fabrication of high-quality hetero-phase structures with controlled carrier mobilities and heterojunction materials with reduced contact resistance. However, to date, general methods to induce phase-change in monolayer TMDs either employ highly-hostile organometallic compounds, or have limited compatibility with large-scale, cost-effective device fabrication. In this paper, we report a new photochemical method to induce semiconductor to metallic phase transition in monolayer MoS2 in a benign chemical environment, through a bench-top, cost-effective solution phase process that is compatible with large-scale device fabrication. It was demonstrated that photoelectrons produced by the band-gap absorption of monolayer MoS2 have enough chemical potential to activate the phase transition in the presence of an electron-donating solvent. This novel photochemical phase-transition mechanism advances our fundamental understanding of the phase transformation in 2D transition metal dichalcogenides (TMDs), and will open new revenues in the fabrication of atomically-thick metal-semiconductor heterostructures for improved carrier mobility and reduced contact resistance in TMD-based electronic and optoelectronic devices
Harnessing Change to Create Sustainable Growth; The Visitacion/ Guadalupe Valley
A Regional Perspective is a report authored by Visitacion Valley Community Development Corporation and Asian Neighborhood Design as the first steps in efforts to create a regional planning perspective, collecting and analyzing data to assist in planning efforts towards sustainable growth, building relationships between regional stakeholders and decision-makers, and providing community outreach to inform and encourage community participation
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