Background: Ultraviolet (UV) photodetectors and UV dosimeters are needed across a variety of applying industries: environmental, flame, industrial process control, space/defense and public health exposure tracking purposes. Wide-bandgap semiconductors (ZnO, TiO 2, Ga 2 O 3, Ga N, Al N, Mg Zn O) are the most dominant for UV sensing applications due to their capabilities to suppress the visible response and providing high UV selectivity. However, practical devices often suffer from slow response/recovery due to oxygen adsorption/desorption kinetics, poor interface charge extraction and instability due to the ambient and thermal cycling. Graphene oxide (GO) and reduced GO (rGO) hold attractive characteristics of tunable work function, large-area solution processing and rich interfacial chemistry making it an interesting candidate material for charge transport network and barrier/interface engineering applications in UV detectors. Cesium oxide / cesium (CsOx/Cs) doping- well known since it allows work function modification and the appearance of interface dipole between Cs-exfoliated graphene and the oxide substrate-- has become one of the appealing handles supporting a band alignment control and a carrier transport enhancement in oxide/graphene systems.
Objective: This review is a method and facility study aiming at (i) to synthesize evidences on thin-film processing routes for GO/oxide UV devices, (ii) to investigate the role of Cs-based doping (Cdalscases(ix/entities)(ix)/Cs( hoping inserting CsOxide) inserting CsOxide on the surface, and Cs ( modified graphene) plus GO) and (iii) for revealing performance trends (responsivity, detectivity, response time, on/off ratio and stability).
Methods: Literature was searched according to the guidance of PRISMA 2020. Included in the studies presented: GO/rGO - oxide UV photodetectors, wide band gap oxide UV device reviews, UV sensing interface relevant cesium doping/band alignment studies.
Results: GO/rGO integration leads to a higher and repeated improvement of UV photoresponses by increasing carrier separation/collection, dark current, and it allows for flexible transparent architectures. MSM and Schottky device based on TiO2 -rGO and graphene/ZnO heterostructures exhibit high responsivity and response characteristics in ms scale in optimized configuration. Cesium-based approaches have less direct correspondence to literature on UV GO photodetectors but also great promise through (a) carrier density modulation in Cs-doped ZnO thin films and (b) interface band alignment tuning via CsOx insertion layers.
Conclusion: The next performance jump in GO-based UV sensors is likely to be 3.6. controlled CsOx interfacial dipoles + defect/oxygen kinetics engineeringstud-3.7 Standards 3.8 Facilitated Pop2 ??? 4.0 scal scaling -3.9 Standardized reporting (noise spectra, stability, humidity, cycling).40Standardized processing (temperatures, cycling, scaling).41 Large temperature scale processing.41[MLC].
International Journal of Materials Science
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