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Abstract This work presents a broad study of transparent and conducting Al-doped ZnO (AZO) thin films that could replace indium tin oxide (ITO) as transparent electrode in optoelectronic devices. AZO thin films are deposited by pulsed DC magnetron sputtering at a sputtering power of 80 W with different pulse frequencies in the range 50–100 kHz. Diffraction data confirm formation of doped ZnO and AZO thin films exhibit preferred orientation in the c -direction. The crystallite sizes of Al:ZnO are in the range 16–21 nm. The field emission scanning electron microscopy and atomic force microscopy of AZO thin films reveal nucleation and growth of uniform and dense films with better quality films deposited at a pulse frequency 75 kHz. A simple and non-destructive optical method is adopted to determine thickness and dispersion parameters such as dispersion energy, carrier concentration to effective mass ratio, and plasma frequency. AZO thin films offer excellent visible light transparency and limited transparency in the near-infrared region due to free carrier absorption. The sheet resistance of AZO thin films is recorded in the range 9–45 Ω/sq making these transparent conducting oxides (TCOs) suitable for optoelectronic applications. The figure of merit as high as 1.99 × 10−2 Ω−1 is achieved for AZO thin film deposited at a pulse frequency of 75 kHz. AZO thin film sputtered with a pulse frequency of 75 kHz is quite stable in ambient oxidizing environment and surface adsorption sites might govern the initial oxidation of films when exposed to atmosphere. Excellent figure of merit and good stability of sputtered AZO thin films as TCO fulfill the requirements of a transparent electrode in photovoltaics. Graphical abstract Unlabelled Image Highlights • AZO thin films demonstrate high figure of merit as transparent conductors. • Low sheet resistance in the range 9–45 Ω/sq • Average transmittance in the range 81.4–85.1% for the wavelength range 400–700 nm • Pulsed DC sputtering capable of producing uniform and stable indium free TCO • Pulse frequency has profound effect to manipulate film growth. [ABSTRACT FROM AUTHOR]

This work demonstrates an exploration of the dynamics of the photogenerated electrons and holes in the S-scheme heterojunctions of CuO nanoparticles and ZnO microrods in the presence of plasmonic Ag nanoparticles. Herein, n-type ZnO microrods developed by the cost-efficient thermal decomposition method are decorated with nanoparticles of CuO and Ag deposited by the direct current magnetron sputtering. Microstructural analyses based on XRD, FESEM, and FETEM measurements reveal interfaces of single crystalline wurtzite ZnO with phase pure CuO and polycrystalline Ag nanoparticles. XPS results complement microstructural information from the FETEM measurements, signifying plasmon loss features of Ag nanoparticles and suggest direct electron transfer from Ag to ZnO, where ZnO microrods constitute the major part of the photocatalysts. The plausible schemes of light collection, carrier generation, and transfer have been presented based on the structural and optical properties, which are utilized to explain the photocatalytic degradation of aqueous cationic Rhodamine 6G under UV-Vis-NIR illumination. The optimized CuO-ZnO heterojunction is highly efficient as a photocatalyst with a degradation rate of 89% due to a greater light collection ability and S-scheme based electron-hole separation at multiple junctions. The plasmonic modulation of the photocatalytic activities of the heterojunction-heterostructure systems is critically governed by the structural organizations of the materials. [Display omitted] • Integration of plasmonic Ag and CuO-ZnO S-scheme heterojunction as photocatalysts. • Insights into photoexcited carrier generation, transfer, and utilization in diverse configurations. • XPS analyses of heterojunction-heterostructure photocatalysts. • Plasmon induced modulation of charge separation at multiple interfaces of Ag and CuO with ZnO. [ABSTRACT FROM AUTHOR]

[Display omitted] • A dry method of fabrication of Ag nanoparticles and ZnO microrods heterostructure. • Preferential nucleation of Ag nanoparticles in proximities of ZnO microrods. • Seed assisted growth of ZnO microrods at higher gas pressure and shorter duration. • Near-UV (380 nm) emission enhancement possibly due to exciton-plasmon interaction. • Nearly 3-fold enhancement of near band edge photoluminescence from ZnO microrods. This work presents a physical vapour-based fabrication of an exciton-plasmon system via depositions of ZnO microrods (ZnOµRs) and Ag nanoparticles (AgNPs) on glass and p-type Si substrates. Pulsed DC sputtering of ZnO at a relatively higher Ar pressure and varying applied power enables deposition of ZnOµRs on ZnO seed layers. Sputtering of Ag ensures fabrication of AgNP/ZnOμR heterostructure with good adhesion suitable for device realization. Microstructural analyses confirm formations of wurtzite ZnOμRs and f.c.c. AgNPs. AgNPs are observed as isolated clusters due to preferential nucleation in the proximities of ZnOµRs. UV–vis absorption spectroscopy reveals broad surface plasmon resonance (SPR) of Ag NPs around 538 nm, which experiences a bathochromic shift in AgNP/ZnOμR heterostructure. The photoluminescence (PL) spectra of AgNP/ZnOμR heterostructure suggest a 3-fold enhancement of narrow near band edge (NBE) emission attributed to the exciton-plasmon interaction. [ABSTRACT FROM AUTHOR]

In this work, an attempt has been made to develop thin and flexible transparent conductors based on the interfaces of Ag nanoparticles (AgNP) and Al:ZnO (AZO) deposited by sequential magnetron sputtering. The entire deposition process is completed within 20–28 min without breaking vacuum thereby preventing post-deposition oxidation of Ag NPs. The co-existence of high transmittance and low sheet resistance along with stability under mechanical bending is a bit difficult to achieve in bare AZO thin film having thickness below 200 nm. The resistivity of the optimized AZO/AgNP/AZO composite structure is significantly low at 3.3 × 10−5 Ω cm, which is two orders lower than that of AZO thin film of similar thickness. The figure of merit of the optimized composite structure peaks at 39.0 mΩ−1 corresponding to Ag NPs growth period of 5 min. The novel fabrication of AZO/AgNP interface in a dry and vacuum environment facilitates superior bending stability required for a flexible transparent conductor. The findings suggest that a system of two thin layers of AZO with embedded Ag NPs can be a potential candidate as an indium free transparent conductor for the next generation optoelectronic device. • Al:ZnO (AZO) and Ag nanoparticles (AgNP) based composite transparent conductor. • Flexible and thin AZO/AgNP/AZO composite prepared by magnetron sputtering. • Low sheet resistance of 2.3 Ω/□ with optimal figure of merit of 39.0 mΩ−1. • Marked reduction of resistivity of AZO due to embedded Ag nanoparticles. • Bending stability due to effective AZO/AgNP interface prepared in vacuum environment. [ABSTRACT FROM AUTHOR]