Plasmonic ambient light sensing with MoS 2 -graphene heterostructures Antonio Radoi a , Mircea Dragoman a,n , Daniela Dragoman b,c a National Research and Development Institute in Microtechnology, Str. Erou Iancu Nicolae 126A, 077190 Bucharest, Romania b University Bucharest, Physics Faculty, P.O. Box MG-11, 077125 Bucharest, Romania c Academy of Romanian Scientists, Splaiul Independentei 54, 050094 Bucharest, Romania HIGHLIGHTS  Plasmonic photodetection of MoS 2 -graphene heterostructures.  Hot-carrier plasmonic doping of MoS 2 mechanism behind this photodetector.  Responsivity is in agreement with photopic standards of the luminosity function.  The response time of the detector is less than the eye blinking time, i.e 0.1 s. article info Article history: Received 9 June 2016 Received in revised form 23 July 2016 Accepted 27 August 2016 Available online 29 August 2016 abstract We present experimental results on plasmonic photodetection of ambient light using MoS 2 -graphene heterostructures illuminated with three very-low-power light emitting diodes (LEDs) radiating in blue, green, and red, respectively. The working principle of this photodetector validates the recent predictions of hot-carrier plasmonic doping of MoS 2 . The obtained responsivity for each spectral domain is in agreement with photopic standards of the luminosity function. The response time of the detector is less than the eye blinking time. & 2016 Published by Elsevier B.V. 1. Introduction Sensing ambient light is deeply involved in our daily life. It can be encountered, for example, in automatic brightness control, automatic turn-off in any touch-screen display, including that of mobile phones, or automatic activation of keypad lightning and screen brightness adjustments in laptops. The application list is very long, involving almost all consumer electronics products such as digital cameras, television, printers, games and automotive applications. A good survey of photonic sensors is found in [1], while the applications of sensing ambient light are detailed in [2]. The target of any ambient light detector, that of having a spectral response close to the human eye, prompted the Interna- tional Commission of Illumination (CIE) to establish a standard photopic luminosity function, which imposes certain responsivity values (in A/W) on the entire visible spectrum from 400 nm to 700 nm, in particular for blue, green and red light. The main problem is that nowadays ambient light detection is based on Si devices, which show significant mismatch with the standard curve of CIE luminosities and human eye because the optical response spectrum of Si detectors extends to IR due to the small energy bandgap of this material (1.11eV). The fulfilment of the CIE stan- dard was achieved up to now only with AlGaAs ambient light detectors [3] in a complicated configuration containing 11 vertical heterostructures between the substrate and the metallic contacts. Molybdenum disulfide (MoS 2 )-graphene heterostructures were proposed as an alternative ambient light detector, because the spectral response of mono- and few-layers MoS 2 is located mainly in the visible region [4]. Indeed, the bandgap of bidimensional (2D) MoS 2 is higher than that of Si, monolayer MoS 2 being a direct semiconductor, with a bandgap of about 1.9 eV, the bandgap de- creasing as the number of layers increases until it reaches the value of 1.2 eV corresponding to bulk MoS 2 [5–8]. As such, in an ambient light detector MoS 2 could assure the absorption and thus the generation of charge carriers in a heterostructure comprising also a graphene layer, which mainly enhances the conduction properties of the heterostructure [9]. The state-of-the-art of optical applications of atomically thin MoS 2 monolayers and few-layers MoS 2 , as well as of other 2D materials, can be characterized as a race for higher responsivities, i.e. higher quantum efficiencies. For instance, extraordinary pho- toresponses, of 4  10 2 A/W, were obtained in 2D In 2 Se 3 na- nosheets [10] deposited on interdigitated electrodes and illumi- nated at 2–4 W/m 2 in the spectral range of 300–500 nm, the area Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/physe Physica E http://dx.doi.org/10.1016/j.physe.2016.08.026 1386-9477/& 2016 Published by Elsevier B.V. n Corresponding author. E-mail address: mircea.dragoman@imt.ro (M. Dragoman). Physica E 85 (2017) 164–168