23,275 research outputs found

    Self-Powered, Highly Sensitive, High Speed Photodetection Using ITO/WSe2/SnSe2 Vertical Heterojunction

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    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)/WSe2_2/SnSe2_2 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 SnSe2_2 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 11001100 A/W and fast transient response time on the order of 1010 μ\mus. A large built-in field in the WSe2_2 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 WSe2_2 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

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    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

    Harnessing Change to Create Sustainable Growth; The Visitacion/ Guadalupe Valley

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    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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