Wafer-scaled monolayer WO₃ windows ultra-sensitive, extremely-fast and stable UV-A photodetection

Highlights: • Monolayer WO₃-based photodetectors were fabricated for the first time. • The device has ultrafast response time of ∼40 μs and responsivity of ∼0.329 A W⁻¹. • The response time is 400-fold improvement over any other WO₃ UV photodetectors. • The device has better characteristics than many 2D materials-based photodetectors. • This proposed strategy has great potential for commercialization of photodetectors. - Abstract: The monolayer WO₃-based UV-A photodetectors, fabricated by atomic layer deposition (ALD) technique at the large area of SiO₂/Si wafer, have demonstrated vastly improved functional capabilities: extremely fast response time of less than 40 μs and photoresponsivity reaching of ∼0.329 A W⁻¹. Their ultrafast photoresponse time is at least 400-fold improvement over the previous reports for any other WO₃-based UV photodetectors that have ever been fabricated, and significantly faster than most of other photodetectors based on two-dimensional (2D) nanomaterials reported-to-date. Moreover, their measured long-term stability exceeds more than 200 cycles without any visible degradation. The ALD-deposited WO₃ monolayer has also exhibited wider bandgap of 3.53 eV and the UV-A photodetector based on it is environmentally friendly, highly reliable, with excellent reproducibility and long-term stability. Thus, the shift to mono-layered semiconductors, which possess completely new quantum-confined effects, has the greatest potential in creating a new class of nano-materials, which in return windows new functional opportunities for various opto-electronic instruments built on semiconductor monolayer and, more importantly, can result in new strategy for fabrication highly-flexible, inexpensive and extremely-sensitive devices. This strategy also opens up the great opportunities for industrialization and commercialization of the photodetectors and other optoelectronic devices based on monolayer or few-layered 2D nanomaterials.