## 1 Introduction  
Over the past decades, transparent conducting electrodes (TCEs) have played a significant role in developing electronic and optoelectronic devices, such as solar cells [1; 2], thin-film transistors [3], and field emission displays [4]. In particular, low-dimensional materials, such as Ag nanowires (NWs) and graphene, have recently been researched to replace traditional TCE materials, i.e., indium-tin-oxide (ITO) thin films, owing to their possible advantages, such as higher electrical conductivity and optical transmittance and improved flexibility. Thin films with a network of Ag NWs exhibit a sheet resistance (\(R_{\text{s}}\)) less than 100 \(\Omega\)/sq with an optical transmittance higher than 90% in the visible range. However, Ag NW thin films have inevitable weaknesses, such as substantial diffused scattering and light absorption [5]. In contrast, graphene has been investigated as a potential flexible TCE as well, specifically owing to its superior optical properties and unique electrical transport properties,which include the room-temperature quantum Hall effect and the mass-less Dirac-fermion behavior of its charge carriers [6; 7]. However, the lack of stability and low electrical conductivity of graphene thin films have been major obstacles to their industrial applications [2; 6; 7]. Other polymeric transparent electrodes based on conjugated polymers and polypyrrole/polyol-borate networks were recently suggested as well [8; 9]. Meanwhile, ruthenium (Ru)-based oxide (RuO\({}_{2}\)) nanosheets (NSs) were suggested as a promising candidate for their application in flexible TCEs owing to their ability to exhibit relatively high electrical conductivity and optical transmittance [10; 11; 12; 13]. Additionally, oxide NSs are reported to be chemically stable under ambient conditions and can be synthesized on a large scale using the chemical exfoliation process; all of these are highly advantageous for their implementation on an industrial scale. Despite the advantages of RuO\({}_{2}\) NSs, the major obstacle to their TCE application is their poor electrical conductivity after fabricating thin films [14; 15]. In our prior work [10], the Ag-doping effect and layer number dependence in individual RuO\({}_{2}\) NSs devices, which were fabricated via electron-beam lithography methods, were the main factors investigated to enhance electrical conductivity in individual RuO\({}_{2}\) NSs. However, the Ag-doping method is not suitable for large-scale NS films due to difficulties in the doping process. Moreover, low electrical transport properties in oxide NS films are primarily caused by the contact resistance between the surfaces of the NSs due to residual organic materials [14; 15]. Considering this, research on methods for decreasing the contact resistance becomes crucial for increasing the possibility of industrial applications of RuO\({}_{2}\) NSs.  
Herein, we propose a facile treatment that can improve the electrical contact and percolation between oxide NSs during the fabrication of transparent and electrically conducting RuO\({}_{2}\) NS films by removing the residual organic materials from their surface. Between every coating procedure of the RuO\({}_{2}\) NSs, ultraviolet-ozone (UVO) irradiation was executed, and it was found that this industrially friendly, easy process significantly improved the sheet resistance \(R_{\rm s}\) of the fabricated multilayer films of the RuO\({}_{2}\) NSs, as well as their optical transmittance.