Nanorod Thin Films Research Articles

Electrical properties and field emission characteristics of ITO nanorod thin films synthesized by electron beam physical vapor deposition

Electrical properties and field emission characteristics of ITO nanorod thin films synthesized by electron beam physical vapor deposition

Enhancement of electrochromic efficiency of TiO2 nanorods

In this study, the rutile TiO2 nanorods thin films were deposited via hydrothermal method on fluorine-doped tin oxide (FTO) substrate. To form a porous morphology layer, a thin film of amorphous titanium oxide (TiOx) was deposited on the TiO2 nanorods through sputtering at high pressure. The samples were annelid at 450ᵒC to transform the amorphous surface to anatase phase. Structural, optical, morphology and electrochemical properties of the samples were examined via X-ray diffraction (XRD), Raman scattering, UV–Vis NIR and photoluminescence (PL) spectroscopies, field-emission scanning electron microscopy (FE-SEM) and Potentiostat device respectively. The samples exhibited a large optical bandgap of 3.35–3.40 eV and high transparency of over 77 % at a wavelength of 555 nm. Raman analysis confirmed the formation of anatase phase on the rutile nanorods under thermal treatment. PL analysis indicated that the oxygen vacancies reached their maximum after sputtering, while the intensity of PL emission significantly increased after annealing. Investigation of the electrochromic properties revealed an increase in coloration efficiency from 2.6 C−1cm2 for bare nanorods to 10.0 C−1cm2 for nanorods after sputtering deposition, which decreased to 5.4 C−1cm2 after thermal treatment.

Oxygen plasma treatment WO3 nanorods for Improvement H2S gas sensing

Herein, the oxygen (O2) plasma has been used to post-treat tungsten oxide (WO3) nanorods to improve the sensing performance of the H2S gas sensor. The reactive DC magnetron sputtering process with the glancing-angle deposition (GLAD) technique was used to prepare the WO3 nanorods. After deposition, the WO3 nanorod thin films were treated with O2 plasma at different treatment power from 100 – 200 W. The physical structure of as-deposition and treated WO3 nanorod thin films was investigated crystal structure and morphology by grazing incident X-ray diffraction (GIXRD), field-emission scanning electron microscope (FE-SEM), and high-resolution transmission electron microscope (HRTEM). The result indicated that the WO3 nanorod structure transformed to the monoclinic polycrystalline phase. FE-SEM and HRTEM observed slight changes in the shape of the WO3 nanorods. The H2S sensing properties were measured at 10 ppm at 150 – 350°C operating temperatures. At an operating temperature of 200 °C, the response to H2S of O2 plasma treated WO3 nanorods is increased by a factor of 5 – 15, and the maximum response to H2S is 15. The results showed that the O2 plasma treatment process improved the sensing response of the WO3 nanorods.

Transient Photocurrents and Defect States in Hierarchically Structured ZnO Nanowires

ZnO‐nanostructured thin films can be used as electron transport layers in ordered heterojunction quantum‐dot solar cells. An increased interface between electron and hole‐transporting layers allows for a fast separation of the electron–hole pairs preventing their recombination. Consequently, an improvement of the overall solar cell efficiency is expected. ZnO hierarchical nanorod thin films can provide the desired increase in interface area. In this work, their properties are studied and compared with simple ZnO nanorod films. The ZnO nanorod films are synthesized hydrothermally by placing the quartz/indium‐tin‐oxide substrates in a solution of zinc nitrate hexahydrate and sodium hydroxide at 90 °C. Hierarchical structures are obtained through a second deposition step. Scanning electron microscopy is used to characterize the size and shape of the nanorods. Simple ZnO films display hexagonal nanorods with a diameter of around 150 nm while hierarchical films show additional 40 nm diameter nanorods growing on the side surfaces of the primary 150 nm nanorods. Optical transmittance spectroscopy reveals a bandgap around 3.35 eV. Current–voltage measurements in the high‐field regime of 104 V cm−1 are used to determine the density of trap states Nt through the application of trap‐filled limit current theory.

Near IR light sensitization modulated to self-assembled CuO–CuxS nanorods thin films

An assembled CuO-CuxS nanorods heterostructure has been produced by liquid chemical conversion and wet etching of the Cu thin film. The chemical etching and anionic exchange modify and convert the Cu thin film to self-assembled CuO/CuxS random nanorods. The enhanced near infrared (NIR) light absorption capability and the effective separation of electron–hole pairs generated by the conjugated CuO-CuxS nanorods complement high visible (especially red) light driven photocatalytic activities as well as NIR photodetecting performances.The surface morphology, chemical content, crystalline analysis and structural vibrations of the CuO/CuxS nanorods were characterized using field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and Raman scattering, respectively. Diffuse reflectance spectroscopy was utilized to evaluate optical properties of the CuO-CuxS nanorods. The assembled CuO–CuxS nanorods thin film exhibits good crystallinity with superior reproducibility and high selectivity for NIR absorption. The CuxS coupling into CuO is also responsible to surface enhanced Raman scattering. The static and high frequency dielectric constant, Urbach tail, optical carrier density and nonlinear refractive index have been estimated. The bandgap energy and optical carrier density are estimated around 1.22 eV and 1027 m−3, respectively. The photoharvesting performance was characterized using under sunlight illumination, and green, red and NIR laser irradiation. The CuO–CuxS hetero-interface manipulate charge transferring of the photoinduced carriers, which promotes the photodegradation efficiency of Methylene blue (MB) and NIR photosensitization.

Amplifying bactericidal activity: Surfactant-mediated AgBr thin film coating over two-dimensional vertically aligned ZnO nanorods for dark-light dual mode disinfection

Thin film coatings with potent antibacterial properties find critical applications in diverse domains such as medical devices, frequently touched surfaces, and food packaging for combating microbial proliferation across diverse scenarios. Two-dimensional photocatalytic antimicrobial coatings, offering a substantial actual-to-apparent surface ratio, hold immense potential for achieving this objective. However, realizing antibacterial performance not just under light but also in dark conditions remains a challenge. To address this, we present AgBr-coated vertically aligned ZnO nanorods (NRs) thin film architecture, employing a unique surfactant-mediated solution-phase spin-coating approach for achieving uniform deposition of AgBr onto ZnO NRs. The resulting ZnO NRs/AgBr heterojunction architectures have been characterized for their microstructural, morphological, elemental, optical, and wettability attributes. The studies have ascertained the tunability of AgBr content by modulating the concentration of its surfactant-based precursor solution. Further, valence band (VB) analyses revealed an increase in the electron density near to the VB edge. The dual role of AgBr as an antimicrobial agent and a photosensitizer, effectively enhancing the visible-light photodisinfection efficacy of ZnO NRs, has been evident through the dark-light dual mode antibacterial studies. Electron paramagnetic resonance measurements have shown hydroxyl radicals being majorly responsible for the visible-light photodisinfection performance. Encouragingly, reusability assessments showcase significant promise, while artificial sweat-wiping studies on the structures unveil heightened photodisinfection efficacy. This enhancement could be attributed to components like urea and lactic acid, speculated to augment the photocatalytic efficiency by minimizing charge recombination.

Controlling the grain formation process with oleylamine and 4-dimethylaminopyridine additives for efficient and stable MAPbI3 solar cells

MAPbI3-based perovskite solar cells (PSC) prepared on one-dimensional structured electron transport layers (ETL) have been widely investigated due to excellent photovoltaic properties. However, they have displayed lower stability and power conversion efficiencies compared to other perovskite solar cells such as FAPbI3 and mixed halide perovskites. To improve the quality of perovskite film, we treat MAPbI3 perovskite layer with oleylamine (OAm) and 4-dimethylaminopyridine (DMAP) during preparation. Modified MAPbI3 layers are prepared by spin coating OAm-added precursor solution on ETLs and the DMAP solution is dripped on the rotating substrate during spin coating process. The OAm additive not only enhances significantly the perovskite crystallinity but also reduces the number of pin-holes inside perovskite thin films. The drip starting time of DMAP solution strongly affects the nanostructures of perovskite layer and the PSC performances. The best efficiency of PSC in this study is 20.49 % and is the highest cell performance compared to other MAPbI3-based PSCs using TiO2 nanorod thin films as ETLs in literature. The remarkable enhancement of PSC performance is assigned to the synergetic effects of both DMAP and OAm at the grain boundaries of MAPbI3 layer. Furthermore, the use of OAm and DMAP leads to significant enhancement of device's stability under ambient conditions.

GLAD Fabricated Self-Powered Photodetector Based on WO3 with SiO2 as Interfacial Layer

Photodetectors based on one-dimensional structures have recently attracted great interest due to their high surface-to-volume ratio and light-trapping efficiency. In this study, a self-powered photodetector based on vertically aligned WO3 nanorod with SiO2 as an interfacial layer has been fabricated using glancing angle deposition. Scanning electron microscope (SEM) analysis confirms the successful growth of WO3 nanorod and SiO2 thin film with a thickness of ~125 nm and ~70 nm, respectively. The device’s optical properties were also analysed using UV-visible spectroscopy, which revealed a wide bandgap and an intense absorption peak in the ultraviolet region. The electrical analysis showed a nonlinear rectifying current-voltage behaviour with high photosensitivity. Additionally, the photodetector exhibits a fast response of 0.31 s rise time and 0.32 s fall time at 0 V. Moreover, the devices possess a high detectivity and a responsivity of 0.68 mA/W. Thus, the obtained finding reveals a potential candidate for self-powered photodetector application.

Gas sensing performance of Tungsten doped V2O5 nanorod thin-films deposited by hot filament CVD combined with DC sputtering

High-quality polycrystalline tungsten doped vanadium pentoxide thin-films were prepared using Hot Filament Chemical Vapor Deposition technique (HFCVD) combined with sputtering by changing target to substrate distance and reaction duration. Scanning electron microscopy and X-ray diffraction revealed that the morphologies and crystalline structures of the films are depending on the deposition parameters such as target to substrate distance and deposition time. Raman spectroscopy is also used to analyse the oxidation states of the vanadium-based films. The deposited nanorod thin-film was exposed to ammonia and ethanol gases to test their gas sensing performance. It exhibits a sensing response of 1.8 and 1.65 at a concentration of 200 ppm ammonia and ethanol and has a recovery time of 44 and 31 s, respectively.

Rapid synthesis of nickel–iron-oxide (NiFeOx) solid-solution nano-rods thin films on nickel foam as advanced electrocatalyst for sustained water oxidation

The development of earth-rich, noble-metal-free, and highly electroactive catalysts to accelerate the oxygen evolution reaction (OER) is a formidable challenge for the establishment of water-splitting technologies. Here, a solid-solution nickel-iron oxide (NiFeOx) electrocatalyst is readily grown on a Ni-foam (NF) substrate by a rapid and economical aerosol-assisted chemical vapor deposition process. In particular, the NiFeOx thin film fabricated in 40 min acquires a distinctive nanorod structure and proves to be stable and efficient for OER in alkaline solutions. It is shown that the catalyst needs a low over-potential of 226 mV to reach the typical current density of 10 mA/cm2, and it can approach a remarkable current density level of 1000 mA/cm2 by taking a slightly higher over-potential of 139 mV. The small Tafel slope of 64 mv.dec−1 and splendid electrochemical stability of 40 h at high current densities outperform many known FeNi-based anodes as well as commercial IrO2 and RuO2. The unique structure of the thin film offers many electroactive sites and a high surface area in combination with an improved electrical conductivity of NF, which is believed to play an imperative role in the excellent activity of the catalyst. The cost-effective and simple strategy to fabricate NiFeOx nano-fibrous is very attractive for the development of electrocatalysts for water splitting.

Comparative analysis of the effect of post-annealing on CeO2 and DC Magnetron Sputtered WO3/ CeO2 nanorods thin films for smart windows

This study investigates and evaluates thin films of WO3 (Tungsten Oxide) coated CeO2 (Cerium Oxide) Nanostructure (NR) for electrochromic applications. Using CH4N2O (Urea) and Ce(NO3)3.6H2O (Cerium Nitrate Hexahydrate) on a fluorine-doped tin oxide (FTO) base, cerium oxide nanorods were produced hydrothermally. Cerium Oxide nanorods were coated with a thin coating of WO3 using DC magnetron sputtering under argon gas at room temperature. In a three-electrode electrochemical system, thin sheets of manufactured WO3/CeO2 nanorods (NRs) served as the working electrode, saturated Hg/HgCl2 served as the reference electrode, and platinum wire served as the counter electrode. To produce the 0.5 M electrolyte, the H2SO4 solution was diluted in deionized (DI) water. Electrochromic tests revealed a 12.15 cm2/C coloring efficiency for annealed 10 µL HCl CeO2/WO3 film. A scanning electron microscope (SEM), an electrochemical analyzer, an X-ray diffraction spectrometer, and an ultraviolet-visible spectrometer were used to study the optical properties, composition, surface morphology, and electrochromic property of the generated thin films. Due to its high charge capacity and optical transmission properties, CeO2 nanorods with WO3 coating have proven to be a practical material for electrochromic devices (ECD).

Enhanced visible and IR light-sensing performance of photoconductive VO2 (M1) nanorods thin film

In this article, we report on the enhanced photo-response of VO2 (M1) nanorods (NRs) thin film upon exposure to visible and near Infrared (NIR) light. The growth of photoconductive VO2 (M1) NRs thin film has been carried out using a pulsed laser deposition (PLD) technique. Field emission scanning electron microscopy (FESEM) showed the formation of NRs-like structures on the deposited thin film. The semiconductor-to-metal transition (SMT) properties at ∼64.8 °C and ∼59.8 °C during the heating and cooling cycle respectively confirm the deposition of VO2 (M1) thin film. The formation of VO2 (M1) thin film is also validated by Raman spectroscopy and X-ray diffraction (XRD) techniques. The photoconductivity of the pulsed laser deposited VO2 (M1) NRs thin film has been studied using the simple planar geometry upon exposure to the visible light (650 nm) and NIR light (980 nm) at 2 V and 5 V bias voltages. The estimated rise time and fall time of the photoconductive VO2 (M1) NRs thin films were about 1.88 ms and 1.9 ms upon exposure to the visible light and 1.89 and 2.4 ms upon exposure to the NIR light respectively. The photo-responsivity values of ∼1120 mA/W and ∼138 mA/W have been achieved for the visible and NIR light respectively at 5 V bias voltage. The photoconductive VO2 (M1) NRs thin film reveals highly responsive and fast visible and NIR light-sensing performance with simple planar geometry (Ag/ VO2 (M1) NRs thin film/Ag).

Intergranular Spin Dependent Tunneling Dominated Magnetoresistance in Helimagnetic Manganese Phosphide Thin Films.

Helical magnets are emerging as a novel class of materials for spintronics and sensor applications; however, research on their charge- and spin-transport properties in a thin film form is less explored. Herein, we report the temperature and magnetic field-dependent charge transport properties of a highly crystalline MnP nanorod thin film over a wide temperature range (2 K < T < 350 K). The MnP nanorod films of ~100 nm thickness were grown on Si substrates at 500 °C using molecular beam epitaxy. The temperature-dependent resistivity ρ(T) data exhibit a metallic behavior (dρ/dT > 0) over the entire measured temperature range. However, large negative magnetoresistance (Δρ/ρ) of up to 12% is observed below ~50 K at which the system enters a stable helical (screw) magnetic state. In this temperature regime, the Δρ(H)/ρ(0) dependence also shows a magnetic field-manipulated CONE + FAN phase coexistence. The observed magnetoresistance is dominantly governed by the intergranular spin dependent tunneling mechanism. These findings pinpoint a correlation between the transport and magnetism in this helimagnetic system.

Structure, functional groups, and optical properties of Al doped ZnO nanorods thin films

Zinc oxide (ZnO) in the form of thin films is a semiconductor that has a direct energy gap of 3.37 eV and an exciton binding energy of 60 meV. These attractive properties make ZnO widely used as a transparent conducting material application in liquid crystal displays, solar cells, etc. Undoped and doped ZnO thin films are widely used in transparent conductor layers due to their better thermal resistance and resistance. In this study, thin films of Al doped ZnO (Zn1-xAlxO) nanorods (x = 1 wt% and 3 wt%) were synthesized by hydrothermal method. The effect of Al doping on microstructure, binding vibration, and optical properties was characterized by XRD (X-Ray Diffraction), SEM (Scanning Electron Microscopy), FTIR (Fourier Transform Infra Red) and UV–Vis (Ultraviolet–visible light) Spectroscopy. Furthermore, the (002) peak of ZnO was shifted because of Al doped ZnO. The diameter of hexagonal is around 78 nm. The binding vibrations found are Zn-O (531, 512, 985, 911 cm−1), Al-O (812 cm−1), Zn-hydroxyl group (1132, 1107 cm−1), CH3 group (2167, 2837, 2861 cm−1), and the hydroxyl group (3560, 3547 cm−1). The energy gap had a moderate drop from 2.97 eV to 2.95 eV.

Structural, optical, photoluminescence, and magnetic properties of Mo0.6−xTi0.3Zn0.1ErxO3 nanorods films fabricated by sol–gel/spin coating technique

Er3+-incorporated Mo0.6−xTi0.3Zn0.1 nanorods thin films were prepared on glass substrates via controlled sol–gel method. The Mo, Zn, Ti, and Er solutions were prepared using ammonium dimolybdate, titanium isopropoxide, zinc acetate dehydrate, and erbium nitrate as the starting material. Ethylene glycol, monoethanolamine, and HCl acid are solvents and solution stabilizers in the sol–gel process. The effect of the Er3+ concentration (0 ≤ x ≤ 0.3 mol%) on the films structure, optical, photoluminescence, and magnetic properties of the nanorods films was investigated by XRD, SEM, Pl, and magnetic measurement. XRD analysis proved that the samples with Er doping = 0.0 and 0.1 consists of single-phase MoO3. By increasing erbium doping to 0.2 and 0.3, bi-phasic were obtained, one of them MoO3 and the other was related to Ti6O11. These results indicate that MoO3 (two-dimensional) can control the internal growth of the Mo0.6−xTi0.3Zn0.1ErxO3 film's structure as supported by SEM and FTIR results. The reflectance of doped films exhibits high values that are increasing with the Er ratio, which adapted an increase in the Eg values from 2.85 to 3.25 eV. The presence of Er3+ in the films is found to sense the photoluminescence process that reveals two emission lines at 1477 and 1543 nm for Er ions. Magnetization behavior for samples exhibits antiferromagnetic behavior with weak ferromagnetic and unsaturated characteristics, where the magnetization at the maximum field (Mmax) increases with increase in Er content.

Structural characteristics and gas sensing response of V2O5 nanorod thinfilms deposited by hot filament CVD

Using the novel hot filament chemical vapor deposition (HFCVD) technique, thinfilms of vanadium pentoxide (V2O5) were deposited under various conditions. The structural characteristics and gas sensing response of the thinfilms were investigated. X-ray diffraction shows that the thinfilms are orthorhombic V2O5 with (001) preferred orientation. Scanning electron microscopy observation reveals that nanorod thinfilms could be obtained under optimized oxygen content and substrate to filament distance. The sensing response of the nanorod thinfilm towards ammonia and ethanol were tested. It exhibits a sensing response of 1.557 and 1.721 towards 200 ppm ammonia and ethanol, respectively, with a response time of 14 s and 20 s after the exposure to ethanol and ammonia and a corresponding recovery time of 26 s and 38 s respectively.

Toward High-Power Output of Generators: High-Power-Factor Ag2Te-Ag Thermoelectric Thin Films Using a Layer-by-Layer Method.

The power factor is key to improving the performance of thin-film thermoelectric generators as power sources. The expected large power factor of Ag2Te testifies to its application potential. In this study, Ag2Te-Ag thin films were fabricated using a layer-by-layer method for controlling their composition and improving their thermoelectric properties. In contrast to the traditional low-temperature monoclinic structure, orthorhombic Ag2Te thin films with Ag nanoparticles on top were obtained by the reaction between Ag and Te nanorod thin films. Analysis of the structural and thermoelectric properties showed increased carrier concentration and enhanced electrical properties of the films, while the structural transition between the orthorhombic structure and the face-centered cubic structure improved the films' electrical stability over a wide range of temperatures. Owing to the special structure, a competitive high power factor of 4.66 mW m-1 K-2 at 668 K was achieved. The proposed approach improves the electrical properties of n-type Ag2Te thin films, owing to the special Ag2Te-Ag structure, and provides guidance for designing high-output-power thin-film thermoelectric generators.

Synthesis, characterizations, and electrochromic studies of WO3 coated CeO2 nanorod thin films for smart window applications

In this work, Cerium oxide nanorods were synthesized on Fluorine doped Tin oxide (FTO) substrate by a hydrothermal technique involving Ce(NO3)3·6H2O (Cerium Nitrate Hexahydrate) and CH4N2O (Urea). The DC magnetron sputtering was used to deposit a thin layer of WO3 on Cerium Oxide nanorods in the presence of argon gas at room temperature. With the prepared CeO2/WO3 thin films as the working electrode, saturated AgCl2 as the reference electrode, and platinum mesh as the counter electrode, a three-electrode electrochemical cell was developed with 0.5 M H2SO4 solution diluted in deionized (DI) water as the electrolyte. The electrochromic studies displayed a coloration efficiency of 10.14 cm2/C for 0.1 M film. SEM, UV–Visible, XRD, and electrochemical analyzer were used to investigate the surface morphology, optical properties, composition, and electrochromic performance of the prepared thin films. A combination of CeO2 nanorods and WO3 coating has been proved to be a potential material for Electro Chromic Devices (ECD), because of its large charge capacity and optical transmission behavior.

Effect of activation temperature of Yttria Stabilized Zirconia (YSZ)/ZnO nanorods thin film on photoelectrochemical cell performance

A photoelectrochemical cell (PEC) is a device that converts solar energy into electrical energy stored in the form of hydrogen and oxygen. The n-type semiconductor that shows promising potential as a PEC cell device is known as ZnO. ZnO in the form of nanorods (NRs) is considered capable of increasing the conversion efficiency of PEC performance due to the large surface area. However, in the energy conversion process, the photoactive layer of the PEC cell corrode easily in the electrolyte solution, reducing the stability of the current produced and shortening the lifetime of the PEC cell. In this study, the stability improvement using solid electrolytes in photoelectrochemical technology was studied. Yttria Stabilized Zirconia is a type of solid electrolyte that has high mechanical properties and ionic conductivity. Activation of YSZ powder at various temperatures is considered very instrumental to the efficiency of the PEC cell device. XRD, SEM-EDX, and UV–Vis characterized the samples. For efficiency measurement through I–V testing, it is equipped with photodetectors such as photoresponse of current and voltage as well as photostability. The higher the YSZ activation temperature, several results were obtained, the larger ZnO NRs/YSZ particle size, the lower the thickness of the film, the higher the absorbance value, and the smaller the band gap. In addition, sample agglomeration occurs at the temperature with the lowest activation and sample response when irradiated enough. Finally, the efficiency of the cell increases, namely at the YSZ activation temperature of 1400 °C, where 1% is produced.

ZnFe2O4/ ZnO 0D-1D heterojunction for efficient photoelectrochemical water splitting

In this work, both ZnO nanorods (NRs) thin films and ZnO NRs powder were successfully synthesized by open aqueous solution bath technique. Further, the residual ZnO nanorods (NRs) powder was used to synthesize ZnFe2O4 (ZFO) nanoparticles (NPs) by hydrothermal method. Finally, ZFO/ZnO heterojunction thin films were prepared and tested for photoelectrochemical water splitting application. The ZFO loading was controlled and tuned by drop-casting various numbers of drops (10, 20, 30 and 40) on the ZnO NRs films keeping the area constant. An improved photocurrent density ∼0.82 mA/cm2 was observed for optimized 30 ZFO/ZnO NRs thin films as compared to ∼0.19 mA/cm2 for pristine ZnO NRs thin films at 1.23 V vs RHE under 100 mW/cm2 light in a 0.1 M Na2SO4 neutral electrolyte. This remarkable enhancement in photocurrent for 30 ZFO/ZnO heterojunction compared to pure ZnO NRs array is attributed to increased light absorption induced electron-hole pairs generation, effective charge transfer and better charge separation at the ZFO/ZnO interface due to a favorable band alignment. This was confirmed with the incident photon to current conversion efficiency (IPCE) measurements which exhibit a significantly high value (∼14%) for 30 ZFO/ZnO films than pristine ZFO and ZnO thin films. It is worthy to note that ZFO NPs coated ZnO thin films deliver long term stability of the electrode against photocorrosion.