2D SnO/In₂O₃ van der Waals Heterostructure Photodetector Based on Printed Oxide Skin of Liquid Metals

Abstract

COMMUNICATION (1 of 8)deployed in the form of van der Waals (vdW) heterostructures that enable fascinating coupled properties from stacked individual layers of 2D sheets which can be exploited in several applications, [2,6,7] including tunneling transistors, [8] quantum hall systems, [9] electrochemical hydrogen evolution reaction, [10] optoelectronics, [4,11] and electronics. [3,12] The p-n junctions are the building blocks of the semiconductor industry, in which the p-n junction heterostructures made from ultrathin materials are of great interest in specialized electronics, optoelectronics, and photonics due to their intriguing coupled properties of the different crystals. [5][6][7]13] Several methods for exfoliation and/or deposition exist such as chemical vapor deposition (CVD), [7] pulsed laser deposition (PLD), [14] molecular beam epitaxy (MBE), [15] pick-and-lift vdW technique, [16] and mechanical exfoliation. [17] These conventional approaches are time consuming and require complicated fabrication processes, [18] yet resulting in devices with small effective areas. [19] Liquid metals are emerging materials which can be used in microfluidics components, [20] sensors, [21] electrodes, [22] phototransistors, [23] flexible and stretchable devices, [24] disease treatment, [22] biomedical field, [22] and in synthesis of low-dimensional materials. [25] Liquid metals have been shown to form a naturally occurring atomically thin layer of oxide at their interface with air, [26][27][28][29] and using liquid metal as a reaction solvent can give access to a sizable portion of oxide elements including oxides which are intrinsically nonlayered crystals. [26] The exfoliated oxides can be converted to sulfides and phosphates. [30] Combination of these atomically thin layers should provide a vast number of vdW heterostructures that are yet to be explored.In this work, atomically thin oxide skin of low melting point liquid metals of tin and indium including p-type tin oxide (SnO) [27] and n-type indium oxide (In 2 O 3 ) [31] are stacked to produce large-area heterostructures with a high degree of homogeneity. Indeed, the p-n vdW heterojunctions feature current rectification properties with exceptionally fast photoresponse times and high sensitivity for UV light. The demonstrated liquid metal synthesis framework offers the possibility of synthesizing and exploring a range of tailored heterostructures for applications in next-generation optoelectronic and photodetection devices.

Liquid Metals: A Novel Possibility of Fabricating 2D Metal Oxides

“…Recently, some research groups tend to utilize vdW stacking to develop advanced electronics and test physics at the 2D limit by stacking ultrathin Ga 2 O 3 with monolayer transition metal dichalcogenides. [ 104 ] Through combining vdW stacking [ 79 ] with dry transfer, different types of heterojunction of 2DMOs and other 2D materials can be achieved. Liquid metals are highly metallic reactive, conductive, and therefore suitable for carrying out electrochemical redox processes on their surfaces.…”

“…[ 78 ] Besides, stacking the skin of different liquid metals can construct large‐area heterostructures of metal oxides. [ 79 ] As demonstrated in Figure 4b, atomically thin skin of Sn and In, namely, SnO and In 2 O 3 were in‐turn transferred to a SiO 2 /Si substrate and stacked, thus producing large‐area, and highly uniform SnO/In 2 O 3 heterostructures. Ultrathin SnO and In 2 O 3 layers were successfully transferred and stacked with each other, as confirmed by the transmission electron microscopy (TEM) images in Figure 4c.…”

Functional Oxides for Photoneuromorphic Engineering: Toward a Solar Brain

“…In metal oxides, the construction of special structures (e.g. low dimensional such as quantum dots, 1D wires and 2D sheets), doping, and taking advantages of the surface plasma resonance effect, the hot electron injection effect and the multiple excitons effect are commonly used methods to enhance the light absorption [927] , [61] . The conceptual change that may be enabled by oxide thin-films with photoactive and resistive switching functionalities would be that the light sensing capabilities of the synaptic devices could be located in the memory and the information itself (photons) can power the neural circuit.…”

Electromagnetic Functions of Patterned 2D Materials for Micro–Nano Devices Covering GHz, THz, and Optical Frequency

“…Alsaif et al used liquid metal van der Waals transfer method to synthesize atomically thin SnO/In 2 O 3 heterostructure photodetector. This is the first time that p–n heterostructures are achieved by liquid metal synthesis …”