Browsing by Author "Dombovari, Aron"

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    High photoresponse of individual WS2 nanowire-nanoflake hybrid materials
    (AIP Publishing LLC, 2018) Asres, Georgies Alene; Järvinen, Topias; Lorite, Gabriela S.; Mohl, Melinda; Pitkänen, Olli; Dombovari, Aron; Tóth, Geza; Spetz, Anita Lloyd; Vajtai, Robert; Ajayan, Pulickel M.; Lei, Sidong; Talapatra, Saikat; Kordas, Krisztian
    van der Waals solids have been recognized as highly photosensitive materials that compete conventional Si and compound semiconductor based devices. While 2-dimensional nanosheets of single and multiple layers and 1-dimensional nanowires of molybdenum and tungsten chalcogenides have been studied, their nanostructured derivatives with complex morphologies are not explored yet. Here, we report on the electrical and photosensitive properties of WS2 nanowire-nanoflake hybrid materials we developed lately. We probe individual hybrid nanostructured particles along the structure using focused ion beam deposited Pt contacts. Further, we use conductive atomic force microscopy to analyze electrical behavior across the nanostructure in the transverse direction. The electrical measurements are complemented by in situ laser beam illumination to explore the photoresponse of the nanohybrids in the visible optical spectrum. Photodetectors with responsivity up to ∼0.4 AW−1 are demonstrated outperforming graphene as well as most of the other transition metal dichalcogenide based devices.
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    Self-assembled large scale metal alloy grid patterns as flexible transparent conductive layers
    (Nature Publishing Group, 2015) Mohl, Melinda; Dombovari, Aron; Vajtai, Robert; Ajayan, Pulickel M.; Kordas, Krisztian
    The development of scalable synthesis techniques for optically transparent, electrically conductive coatings is in great demand due to the constantly increasing market price and limited resources of indium for indium tin oxide (ITO) materials currently applied in most of the optoelectronic devices. This work pioneers the scalable synthesis of transparent conductive films (TCFs) by exploiting the coffee-ring effect deposition coupled with reactive inkjet printing and subsequent chemical copper plating. Here we report two different promising alternatives to replace ITO, palladium-copper (PdCu) grid patterns and silver-copper (AgCu) fish scale like structures printed on flexible poly(ethylene terephthalate) (PET) substrates, achieving sheet resistance values as low as 8.1 and 4.9 Ω/sq, with corresponding optical transmittance of 79% and 65% at 500 nm, respectively. Both films show excellent adhesion and also preserve their structural integrity and good contact with the substrate for severe bending showing less than 4% decrease of conductivity even after 105 cycles. Transparent conductive films for capacitive touch screens and pixels of microscopic resistive electrodes are demonstrated.