Infrared Proximity Sensors Based on Photo‐Induced Tunneling in van der Waals Integration

Abstract

Infrared (IR) detectors based on photo‐induced tunneling in van der Waals heterostructures (vdWHs) of graphene/h‐BN/graphene or MoS2/h‐BN/graphene exhibit extremely low dark currents owing to a large electron barrier. However, a lack of tunneling barrier materials except for h‐BN for 2D vdWHs limits their further enhancement. In this study, a broadband detection is reported with high sensitivity and fast photoresponse of IR proximity sensor by a vdW integration (2D‐3D) of graphene or MoS2, with NiO/Ni as the IR absorber and hole selective transport layer/counter electrode. The low Schottky barrier height of the reported junctions suppresses dark current with a high detectivity ≈1014 Jones and generates a photocurrent by transporting photo‐excited carriers through a low hole barrier at a wide wavelength. Two types of integrated IR proximity sensor applications are developed: a passive sensor (MoS2/NiO/Ni) for the near‐IR (NIR) range and an active sensor (Gr/NiO/Ni) for the mid‐IR (MIR) range. The former shows a broadband photoresponse to reflect the NIR, while the latter absorbs human body irradiation (2–16 µm wavelength) with a fast photoresponse of 3.5 s (rise time) and 1.8 s (fall time). The fabricated sensors utilize low power, broadband detection, high sensitivity, fast photoresponse, and large‐scale area at room temperature.

Skin-Like Near-Infrared II Photodetector with High Performance for Optical Communication, Imaging, and Proximity Sensing

“…Flexible second-near-infrared (NIR-II) photodetectors and arrays, especially skin-like photodetectors, that can seamlessly integrate with a curved surface have considerable advantages in terms of optical communication, NIR-II imaging, light detection and ranging (LiDAR) sensing, and biological health monitoring. − Specifically, their capability of laminating on three-dimensional (3D) objects makes them a key element in complex environmental conditions to distinguish and acquire extensive information. − Indeed, tremendous efforts have been made to improve the optoelectronic performance and mechanical stability of NIR-II photodetectors. However, most of these devices exhibit either poor sensitivity or slow photoresponse. ,,− The fundamental reason for this lies mostly in the contrary requirements of responsivity and response speed for photocarrier lifetime . Moreover, it is more challenging to maintain an outstanding optoelectronic performance under severe mechanical deformation, which seriously impedes the practical applications of flexible NIR-II photodetectors.…”

SrTiO3/CuNi‐Heterostructure‐Based Thermopile for Sensitive Human Radiation Detection and Noncontact Human–Machine Interaction

“…Along with the in-depth investigations on low-dimensional (LD)-materials-based photodetection, it was found that the photo thermal and thermoelectric properties of LD materials can be integrated together, [21] whose spectral response ranges reach up to LWIR [19,23,24] and even terahertz regions. [25,26] However, when it comes to detecting the weak human radiation, their output signals are usually low in magnitude, [5,27,28] which may be ascribed to the poor absorption, low Seebeck coefficient (S) and/or small absorption area. [21] For instance, under illumination by human finger, graphene detector with asymmetric electrodes (Au/graphene/NiO/Ni) exhibits a current response of ≈0.1 nA, [5] and graphene-based thermopile exhibits a voltage response of ≈15 nV.…”

“…[25,26] However, when it comes to detecting the weak human radiation, their output signals are usually low in magnitude, [5,27,28] which may be ascribed to the poor absorption, low Seebeck coefficient (S) and/or small absorption area. [21] For instance, under illumination by human finger, graphene detector with asymmetric electrodes (Au/graphene/NiO/Ni) exhibits a current response of ≈0.1 nA, [5] and graphene-based thermopile exhibits a voltage response of ≈15 nV. [27] Such low photoresponse means that the complicated low-noise readout circuit is required, which is usually unacceptable for actual noncontact HMI applications.…”

“…

As the input interface of HMI, multiple noncontact sensing techniques have been developed, which can be primarily classified into two categories: active and passive. The active sensors, such as optical [4][5][6] and capacitive [7][8][9] proximity switches, comprise a continuous transmitter and a receiver, which typically require high power consumption. In contrast, the passive sensors which directly detect human-related physical properties, such as spontaneous thermal radiation, [10,11] humidity, [12][13][14][15] and accumulated electric charges, [16,17] are known for their low-power characteristic.

…”

Plasma-assisted three-dimensional lightscribe graphene as high-performance supercapacitors

“…As an alternative approach, FGs could be prepared by a sulfur hexafluoride (SF 6 ) plasma-assisted process instead of F 2 and XeF 2 sources which are also less toxic and more compatible with IC fabrication processes 27 . Another advantage of this method is that the fluorination process is accompanied by partial etching of graphene flakes, which leads to three-dimensional FGs 28 . This 3D structure can dramatically increase electrochemical active sites and surface area of obtained FGs which are excellent for supercapacitor applications.…”