Ti-doped ZnO Research Articles

The role of synthesizing time on the optoelectronic properties of TiO2-ZnO nanocomposite on PTFE substrate fabricated by the chemical bath deposition method

ZnO-based ultraviolet photodetectors have been employed in advanced applications, including environmental monitoring, space exploration, and secured optical communication. In this work, TiO2-ZnO nanocomposite that included Ti-doped ZnO nanorods was synthesized using chemical bath deposition method at 96 °C on PTFE substrates for ultraviolet photodetectors. ZnO nanorods grew for 3 hours, followed immediately by the synthesis of TiO2 for 2 hours. The characterizations revealed several distinguished structural, optical, and electrical properties compared with reference ZnO-only samples deposited for 3 h and 5 h respectively. The indirect band gap of the produced nanocomposite was 3.09 eV. The fabricated ultraviolet photodetector revealed outstanding results: a responsivity of 673.667 mA/W, a detectivity of 5.121×108 Jones, and an external quantum efficiency of 229.44%. The results showed the potential of the nanocomposite for photodetector applications on flexible substrate.

Effect of Annealing and Doping Process of the Zn1-xTixO Films

In this study, undoped and Ti-doped ZnO thin films grown by SILAR (Successive Ionic Layer Adsorption and Reaction) method were investigated using XRD, SEM, linear absorbance and electrical characterization. The effect of doping ratio was determined changing Ti ratios from 0.05 to 0.20. In addition, the films with the same additive ratio were annealed at 300°C for 15 minutes in nitrogen environment. Thus, the effects of both annealing and doping ratio on the thin films produced were examined in detail. When the current-voltage graphs are examined, it is observed that there is a decrease in the resistance values with doping. The best additive effect was observed for Zn0.90Ti0.10O film and the structures formed after this additive ratio returned to their initial morphology.

A study of the UV photodetectors properties based on the effect of TiO2 on ZnO nanorods grown via the chemical bath deposition method on p-type Si (100) substrates

In this study, a heating composition process was used to construct Ti-doped ZnO (Ti/ZnO) nanocomposites to serve as an active layer in UV detection devices. Prior to synthesis, a ZnO seed layer was deposited on p-type Si (100) substrates (p-Si substrates) using radio frequency (RF) sputtering. Afterward, Ti/ZnO thin films (TFs) were successfully grown using the chemical bath deposition method (CBD) by combining different amounts of TiO2 nanofluid with ZnO precursor solutions. The volume of the TiO2 nanofluid ranged from 12.5% to 50% with respect to the total volume. FE-SEM, EDX, and AFM were employed to examine the morphological, elemental, and topographical characteristics of the formed nanocomposites. Thermo-evaporation was used to print Ag interdigitated electrodes (IDE) on the nanocomposites to fabricate UV photodetectors. The (002) Ti/ZnO peak along the z-axis on the substrate, which increases with increasing amounts of TiO2, provides evidence of the crystallinity and the hexagonal wurtzite structure of the samples. UV–Vis spectroscopy showed high diffuse reflectance curves with indirect energy bandgaps from 3.1969 eV to 3.2203 eV. The TiO2 nanofluid used in the growth impacted the synthesized Ti/ZnO, which affected the performance of the photodetectors. A responsivity, photosensitivity, gain, detectivity, rise time, and decay time of 0.107495 AW−1, 3833.67%, 39.34, 6.75 × 108 jones, 0.19 s, and 0.24 s were recorded when 50% of the TiO2 was used during the synthesis process of the ZnO nanorods. Based on the findings, the nanocomposites grown on p-Si substrates are suitable for use as thin films in optoelectronics, especially UV detection devices.

NO Gas Sensor Based on Ti-Doped ZnO Thin Films Prepared by SILAR Method

In this study, Ti-doped ZnO films with flower-rod-like nanostructures were synthesized by the SILAR method for enhanced NO gas sensing applications. The stoichiometric ratio of Ti in the host ZnO lattice was confirmed by atomic absorption and energy-dispersive X-ray spectroscopies. All the synthesized films exhibited a pure wurtzite hexagonal structure that seemed to deteriorate at high Ti doping contents as it was manifested by the measured X-ray diffraction patterns. Scanning electron microscopy images of ZnO revealed the coexistence of porous flower- and rod-like structures, and became finer, denser and more compact with Ti doping. By UV-Vis measurements, the transmittance of the synthesized pure ZnO thin film in the visible region (~75%) increased by about 10% with Ti doping, and the energy bandgap seemed to decrease up to a some limit of Ti content. Among the fabricated sensors (based on pure ZnO, 1% Ti-doped, 3% Ti-doped and 5% Ti-doped ZnO films), the best sensing performance was observed for the 1% Ti-doped ZnO film. At first, this was associated with its high density of oxygen vacancies present on the surface of the film and ionized oxygen vacancies present in the ZnO lattice (confirmed respectively by X-ray photoelectron and photoluminescence spectroscopies). Nonetheless, this may be also due to its increased crystallinity (confirmed by X-ray diffraction and photoluminescence spectroscopy), high area-to-volume ratio (confirmed by scanning electron microscopy images), high specific surface area (confirmed by Brunauer-Emmett-Teller measurements) as well as high mobility and carrier concentration (confirmed by Hall measurements). The sensor was highly selective to NO gas and showed notable stability as well as very short response and recovery times which makes it eligible for the early detection of any indoor or outdoor NO gas leakages. Keywords : SILAR, Ti-doped ZnO, Structural properties, Optical properties, Electrical properties, Gas sensor. Acknowledgement This research was supported by the research grant 021220FD2201 “Development of highly sensitive MOS based nano-film gas sensors” from Nazarbayev University. Figure 1

Investigation of microstructure and optical characteristics of Ti-doped ZnO thin films as an effective solar collector in photovoltaic solar cell applications using digitally controlled spray pyrolysis

Investigation of microstructure and optical characteristics of Ti-doped ZnO thin films as an effective solar collector in photovoltaic solar cell applications using digitally controlled spray pyrolysis

Ultrasensitive nitric oxide gas sensors based on Ti-doped ZnO nanofilms prepared by RF magnetron sputtering system

It is aimed to explore the advantages of titanium doping and magnetron sputtering as opposed to chemical-based methods on the surficial and electrical characteristics of ZnO films and their gas sensing performance in particular. RF magnetron sputtering was employed to synthesize a pure ZnO nanofilm as a reference and Ti-doped ZnO nanofilms with various Ti contents. The doping process was done by sputtering Ti-doped ZnO targets developed through solid-state reaction, and doping content was determined by EDS analysis. All nanofilms exhibited pure hexagonal wurtzite structure and relatively flat and homogenous surfaces with a clear distribution of nanoparticles in the Ti-doped samples. The observed enhancement in the properties of the nanofilms was reflected in the ultimate performance of the gas sensor. In this regard, the sensor with 1 wt% Ti content showed the best gas sensing performance with an ultra-sensitivity of 1.72 for 1 ppm and 0.9 for 1 ppb NO gas at a relatively low working temperature of 167 °C. The sensor also acquired outstanding stability, quick responsivity, reproducibility and superior selectivity required for NO monitoring.

Biosynthesis, characterization, and antibacterial activity of Ti-doped ZnO (Ti/ZnO) using mediated Aspergillus niger

This study presents a biosynthetic route for TiO2-doped ZnO (Ti/ZnO) using the primary metabolite component of the Aspergillus niger fungi as a source of the capping agent. The effect of biosynthetic variables based on the extracellular (Ti/ZnO) and intracellular (Ti/ZnO) enzymatic cycles of Aspergillus niger during the 3–4 days growth period was analyzed. The morphological differences between the extracellular and intracellular Ti/ZnO produced were characterized using Fourier Transform Infrared (FTIR) spectroscopy, Ultraviolet-Visible Spectrometry (UV–Vis), X-ray Diffraction (XRD), and Scanning Electron Microscope equipped with Energy Dispersive X-ray spectroscopy (SEM-EDX). Analyzing Ti/ZnO with different biosynthetic variables exhibited the same crystal structure, namely hexagonal Wurtzite, but with different morphology and crystal sizes of 27.42–28.99 nm. Furthermore, Ti/ZnO has a pattern of a rod with a length and diameter of 287–455 nm and 126 - 156 nm, respectively. In vitro antimicrobial activity testing against Staphylococcus epidermidis bacterial cells was performed under exposure to ultraviolet light with the wavelength of λ = 385 nm. The results indicated that the increase in bacterial activity was influenced by the effect of biosynthetic variables based on differences in morphology, size, the shape of Ti/ZnO, enzymatic cycle, and growth time of Aspergillus niger.

Ammonia gas detection by solution combustion-processed pristine & Ti-doped ZnO transparent films: a reverse effect of doping on gas response

Ammonia gas detection by solution combustion-processed pristine & Ti-doped ZnO transparent films: a reverse effect of doping on gas response

Preparation of Ti-Doped ZnO/Bi2O3 Nanofilm Heterojunction and Analysis of Microstructure and Photoelectric Properties

Ti-doped ZnO (TZO) and Bi2O3 thin films were designed and deposited by magnetron sputtering successively on ITO glass substrate to form a Ti-doped ZnO/Bi2O3 (TZO/Bi2O3) heterojunction. Microstructure and photoelectric properties of TZO, Bi2O3, and TZO/Bi2O3 films were tested and characterized. The results showed that TZO film with a hexagonal wurtzite structure was preferentially grown along the crystal plane (002), had a good crystallization state, and was an N-type semiconductor film with high transmittance (90%) and low resistivity (4.68 × 10−3 Ω·cm). However, the Bi2O3 film sputtered in an oxygen-containing atmosphere and was a polycrystalline film that was preferentially grown along the crystal plane (111). It had a lower crystallization quality than TZO film and was a P-type semiconductor film with low transmittance (68%) and high resistance (1.71 × 102 Ω·cm). The I–V curve of TZO/Bi2O3 composite films showed that it had an obvious heterojunction rectification effect, which indicates that the PN heterojunction successfully formed in TZO/Bi2O3 films.

Enhanced Photocatalytic Degradation of Methylene Blue Using Ti-Doped ZnO Nanoparticles Synthesized by Rapid Combustion.

ZnO and Ti-doped ZnO (Ti-ZnO) nanoparticles were synthesized using rapid combustion. The morphology of ZnO and Ti-ZnO featured nanoparticles within cluster-like structures. The ZnO and Ti-ZnO structures exhibited similar hexagonal wurtzite structures and crystal sizes. This behavior occurred because Zn2+ sites of the ZnO lattice were substituted by Ti4+ ions. The chemical structure characterization implied the major vibration of the ZnO structure. The physisorption analysis showed similar mesoporous and non-rigid aggregation structures for ZnO and Ti-ZnO using N2 adsorption-desorption. However, Ti-ZnO demonstrated a specific surface area two times higher than that of ZnO. This was a major factor in improving the photocatalytic degradation of methylene blue (MB). The photocatalytic degradation analysis showed a kinetic degradation rate constant of 2.54 × 10-3 min-1 for Ti-ZnO, which was almost 80% higher than that of ZnO (1.40 × 10-3 min-1). The transformation mechanism of MB molecules into other products, including carbon dioxide, aldehyde, and sulfate ions, was also examined.

Rational engineering of morphology modulated Ti-ZnO thin films coupled monolayer Ti3C2 MXene for efficient visible light PEC water splitting activity

• Morphology modulated Ti 3 C 2 /Ti-ZnO composite constructed. • Well-dispersed grain-like morphology of Ti-ZnO anchored on monolayer Ti 3 C 2 MXene. • Ti 3 C 2 /Ti-ZnO composite show improved visible light PEC activity. • Ti 3 C 2 /Ti-ZnO composite promote the long-term PEC activity for 21 min. • The charge transport mechanism under visible light PEC activity is evaluated. Novel morphology modulated monolayer 2D Ti 3 C 2 MXene coupled Ti-doped ZnO (Ti 3 C 2 /Ti-ZnO) photoelectrode developed for exploring interfacial charge transfer and visible-light photoelectrochemical (PEC) water splitting. Here, we altered the flake-like ZnO into grain-like morphology by selective Ti (2 at.%) doping into ZnO under simultaneous radio frequency (RF) and direct-current (DC) magnetron sputtering. This study describes the versatility of the Ti 3 C 2 /Ti-ZnO (monolayer/grain-like) interface. Transmission electron microscopy findings suggest that Ti 3 C 2 MXene developed in a monolayer. Moreover, scanning electron microscopy proved a consistent grain-like Ti-ZnO thin film interface with monolayer Ti 3 C 2 MXene. We also find Hall effect measurements to uncover the interfacial impact on charge carrier generation. The fabricated monolayer/grain-like interface modulated the band gap towards visible region. With all the above benefits, Ti 3 C 2 /Ti-ZnO achieved stable visible water splitting for 21 min. Overall, these findings provide the potentiality of Ti 3 C 2 /Ti-ZnO photoelectrode to extend the PEC activity towards the visible region.

Quick NO Gas Sensing by Ti-Doped Flower-Rod-like ZnO Structures Synthesized by the SILAR Method.

In this study, Ti-doped ZnO films with flower-rod-like nanostructures were synthesized by the successive ionic layer adsorption and reaction (SILAR) method for enhanced NO gas-sensing applications. The stoichiometric ratio of Ti in the host ZnO lattice was confirmed by atomic absorption and energy-dispersive X-ray spectroscopies. All of the synthesized films exhibited a pure wurtzite hexagonal structure that seemed to deteriorate at high Ti doping contents as was manifested by the measured X-ray diffraction patterns. Scanning electron microscopy images of ZnO revealed the coexistence of porous flower- and rod-like structures, which became finer, denser, and more compact with Ti doping. By UV-vis measurements, the transmittance of the synthesized pure ZnO thin film in the visible region (∼75%) increased by about 10% with Ti doping, and the energy band gap seemed to decrease up to some limit of Ti content. Among the fabricated sensors (based on pure ZnO, 1% Ti-doped, 3% Ti-doped, and 5% Ti-doped ZnO films), the best sensing performance was observed for the 1% Ti-doped ZnO film. At first, this was associated with its high density of oxygen vacancies present on the surface of the film and ionized oxygen vacancies present in the ZnO lattice (confirmed, respectively, by X-ray photoelectron and photoluminescence spectroscopies). Nonetheless, this may also be due to its increased crystallinity (confirmed by X-ray diffraction and photoluminescence spectroscopy), high area-to-volume ratio (confirmed by scanning electron microscopy images), high specific surface area (confirmed by Brunauer-Emmett-Teller measurements) as well as high mobility and carrier concentration (confirmed by Hall measurements). The sensor was highly selective to NO gas and showed notable stability as well as very short response and recovery times, which makes it eligible for the early detection of any indoor or outdoor NO gas leakages.

Structural, Optical, and Photoluminescence Studies of Ti-Doped ZnO Nanopowders by a Simple Solution Method

Structural, Optical, and Photoluminescence Studies of Ti-Doped ZnO Nanopowders by a Simple Solution Method

Relaxation of residual stress-controlled thermopower factor in transparent-flexible Ti-doped ZnO thin films

Transparent-flexible thermoelectric materials are attractive for future small-sized consumer electronics, the internet of things, and wearable devices. The microstructural evolution and subsequent thermoelectric properties of Ti 1%.at-doped ZnO thin films, grown on polyimide flexible substrates, are presented. The thin films were grown using radio frequency a magnetron sputtering method followed by annealing for 60 min at temperatures of 200–400 °C under vacuum atmosphere. Post-annealed films demonstrate a hexagonal Wurtize structure. It is found that the annealing helped to relax residual stresses in the thin films, subsequently leading to enhanced charge concentration, carrier mobility, mean free path, and density-of-states effective mass. The thin film, annealed at 300 °C, illustrates the highest power factor of the films measured at room temperature at 19.10 μW m−1 K−2. Further increases in the annealing temperature suggest Ti2+ diffuses into the ZnO lattice and in turn disturbs the crystalline structure; this results in a reduction of the power factor to 9.32 μW m−1 K−2 at an annealing temperature of 350 °C.

Enhanced Nitrogen Monoxide Gas-Sensing Performance of Ti-Doped ZnO Nanostructures By SILAR

Fig. 1. Schematic illustration of SILAR fabrication process [1].The use of semiconducting metal oxides to develop highly sensitive NO gas sensors remains an important approach in the field of gas sensing applications [2]. In this research, we describe the synthesis, characterization, and application of a very promissing NO gas sensing material ZnO doped with different atomic percentages of Ti and prepared by a simple SILAR [3] method. Synthesized specimens were structurally and morphologically characterized. The NO sensing characteristics of pristine ZnO and Ti-doped ZnO were compared using a gas sensing measurement system. The sensitivity, operating temperature, and response/recovery time were systematically investigated based on the change in electrical resistance of the materials in the presence of NO. Experimental results confirmed that 50 at% Ti-doped ZnO showed a maximum response to NO gas at an operating temperature. The sensing mechanism of the pristine and Ti-doped ZnO nanostructures is discussed in detail. We believe that the Ti-doped, flower-like ZnO nanostructure is a potential material for semiconductor-oxide-based NO gas sensors. Key words: NO gas sensor, SILAR method, flower-like, Ti-doped ZnO. Acknowledgement This research was supported by the research grant 021220FD2201 “Development of highly sensitive MOS based nano-film gas sensors” from Nazarbayev University. Reference [1] B. Soltabayev, M.A. Yıldırım, A. Ateş, S. Acar, The effect of indium doping concentration on structural, morphological and gas sensing properties of IZO thin films deposited SILAR method, Mater. Sci. Semicond. Process. 101 (2019) 28–36. https://doi.org/10.1016/j.mssp.2019.05.026.[2] V.S. Bhati, M. Hojamberdiev, M. Kumar, Enhanced sensing performance of ZnO nanostructures-based gas sensors: A review, Energy Reports. 6 (2020) 46–62. https://doi.org/10.1016/j.egyr.2019.08.070.[3] T. Çorlu, I. Karaduman, M.A. Yildirim, A. Ateş, S. Acar, Effect of Doping Materials on the Low-Level NO Gas Sensing Properties of ZnO Thin Films, J. Electron. Mater. 46 (2017) 3995–4002. https://doi.org/10.1007/s11664-017-5503-z. Figure 1

Effect of deposition temperature on the properties of F and Ti co-doped zinc oxide films

ZnO + 1.5 wt.% TiO2 powder is calcined at [Formula: see text] and sintered at [Formula: see text] to prepare the Ti-doped ZnO ceramic target, and RF sputtering is used to deposit F and Ti co-doped ZnO (FTZO) films by introducing Ar + CF4 mixing gas (CF4 flow rate is 0.2%) into the deposition chamber. The deposition temperature is changed from room temperature to [Formula: see text], and the thicknesses of all deposited FTZO films are controlled at about 320 nm. After FTZO films are deposited, X-ray diffraction pattern is used to analyze their crystalline properties, field-effect scanning electron microscope is used to observe their surface morphologies and confirm their thicknesses. n&k analyzer is used to measure the transmittance spectra in the wavelength range of 300–1100 nm and we find that the absorption edge of FTZO films is shifted to lower wavelength as the deposition temperature increases. The optical energy band gap of FTZO films is calculated using the transmittance spectra and the electrical properties of FTZO films are measured using a Hall equipment. Finally, secondary-ion mass spectrometry is used to analyze the C, O, F, Si and Ti elements with different deposition temperatures for confirming the existence and distribution of [Formula: see text] ions and non-existence of C element.

Enhanced optoelectronic properties of Ti-doped ZnO nanorods for photodetector applications

We report the effect of Ti-doping on structural, morphological, photoluminescence, optical and photoconductive properties of ZnO thin films. Pure and Ti(1, 3 and 5%)-doped ZnO thin films are deposited by the successive ionic layer adsorption and reaction (SILAR) method. The X-ray diffraction analysis revealed the single-phase hexagonal wurtzite ZnO structure of all the films. Scanning electron microscope images suggest the formation of rod shaped particles in Ti-doped ZnO thin films. Photoluminescence spectra of all the films show emission peaks centered at 398 nm, 413 nm, 438 nm, 477 nm and 522 nm wavelengths. Optical properties support the semiconducting nature of all the films. The optical bandgap values are estimated to be 3.29 eV, 3.26 eV, 3.19 eV and 3.23 eV for ZnO, ZnO:Ti(1%), ZnO:Ti(3%) and ZnO:Ti(5%) thin films, respectively. Photoconductivity study indicates that ZnO:Ti(3%) thin film exhibits high responsivity, external quantum efficiency and detectivity of 0.30 AW-1, 97% and 5.49 × 1010 Jones, respectively, among all the films. The enhanced photoconductivity of Ti-doped ZnO thin films make them useful for optoelectronic applications.

Structural, morphological, optical and electrical properties of the Ti doped-ZnO (TZO) thin film prepared by RF sputter technique

In this study, the structural, morphological, optical, as well as electrical properties of the titanium doped (wt 5%) ZnO (TZO) thin film grown with the RF sputtering system was examined. TZO thin films were deposited on both corning glass (CG) and n–type Si substrates. It was determined that the TZO thin film deposited on CG has crystallinity, good surface homogeneity, low surface roughness as well as suitable band gap value from X–Ray diffraction (XRD), atomic force microscopy (AFM) as well as UV–Vis analysis. In addition, TZO thin film deposited on the n–Si substrate was used to determine the electrical properties. The current–voltage (I–V) measurements of the Au/TZO/n–Si structure was done at 80 K and 300 K. Capacitance–voltage (C–V) and conductance–voltage (G/ω–V) measurements of the Au/TZO/n–Si structure was examined for 0.3, 0.5 and 1 MHz.

In Situ Resistance Monitoring during Flame-Aerosol Deposition of Metal Oxide Gas Sensing Layers

Introduction Chemo-resistive sensors are highly promising for the detection of trace-level compounds in medical diagnostics[1] or indoor air monitoring[2]. In particular, gas sensors made by direct flame-aerosol synthesis are attractive due to their highly porous and crack-free sensing films[3]. They are composed of high-surface area nanoparticles with diverse composition tuned for ppb-level sensitivity and high selectivity towards key analytes such as Si-doped WO3 for acetone[1] or Ti-doped ZnO for isoprene[4]. Fabrication development has also led to the ability to process flame-made sensors by techniques compatible with standard silicon-wafer micromachining[5]. This enables the preparation of low power sensors that are attractive for portable handheld devices. So far, the development of such sensors has been focused mostly on material composition and, to a lesser extent, on film morphology and design. However, optimizing the latter could improve the sensor sensitivity as well as response and recovery times. Measuring the resistance during flame-deposition of nanostructured films in situ offers fabrication control by providing immediate feedback when an interconnected film is created[6]. This ultimately allows the fabrication of sensing films of minimal thickness and optimal resistance in a reproducible and economical manner. In situ resistance monitoring This work focuses on in situ monitoring the resistance of nanostructured films fabricated by direct deposition of flame-made Sb-doped SnO2 nanoparticles[6]. The sensing film morphology was tuned by a substrate-impinging particle flame, fed by a precursor solution containing varying metal ion concentrations. In situ resistance monitoring enabled control over final film resistance as well as direct insight into network formation and nanoparticle growth, necking and coalescence. The performance of these films as ethanol vapor sensors was assessed and related to their in situ resistance and nanoparticle film characteristics. Method Gas sensing nanoparticle films were prepared by direct deposition of flame-made Sb-doped (12 at%) SnO2 onto alumina substrates with interdigitated platinum electrodes. Deposition was carried-out for up to 6 min. Substrate preheating, film deposition and cooling to room temperature was closely monitored by the in situ resistance (Ri) between the interdigitated electrodes with a multimeter (Tektronix DMM4050). Nanoparticle sensing films were imaged by scanning electron microscopy (Hitachi S-4800 FE-SEM) after particle deposition for 2 min. Results and Conclusions Figure 1a shows the formation of Sb-doped SnO2 nanoparticles in a flame, followed by direct deposition onto the sensor substrate and in situ film resistance (Ri) read out. Figure 1b shows the in situ film resistance as a function of deposition duration using 1 (red squares), 10 (blue circles) or 100 (green triangles) mM FSP precursor solution concentrations (PSC). At low PSC (1 mM), the Ri remains at first (up to ca. 1 min) rather indifferent to nanoparticle deposition as it takes some time to build the interconnected particle bridges. But as deposition is prolonged (t >1.5 min), the Ri starts to drop. This clearly indicates the formation of an interconnected network of nanoparticles. Also quite notable is the strong oscillation of Ri by more than an order of magnitude during network formation. This stems from the constant formation (by deposition) and break-up of necked nanoparticles (by coalescence) on the substrate (i.e., repeatedly from lace-like to cauliflower-like structures) during flame-deposition. Increasing the PSC from 1 to 10 mM or 100 mM leads naturally to a higher generation rate of nanoparticles and, therefore, faster drop in resistance. This is confirmed by SEM imaging after 2 minute deposition time for 1, 10 and 100 mM (Figure 2 a-c). As expected, nanoparticles are assembled more densely at higher PSC. As a result, the film formation and morphology of Sb-doped SnO2 can be monitored during direct flame-deposition. This monitored Ri is correlated to its evolving particle size and necking, enabling the ability to optimize material quantity, fabrication time and the final film resistance. This leads to the ability to rapidly synthesize thin flame-made gas sensors with improved sensitivity and reduced response/recovery times.

Self-Organized In-Depth Gradients in Highly Ti-Doped ZnO Films: Thermal Versus MW Plasma Annealing

Highly Ti-doped ZnO films have been produced by a spin-casting sol-gel process. The spin-casted films show high in plane homogeneity and optical quality. However, when inspected in depth, the surface composition is Ti rich. We show that two possible annealing processes can be considered depending on the properties to exploit. To promote in-depth homogenization, thermal annealing processes have been applied. Meanwhile, the gradients can be exacerbated, thanks to a non-negligible surface sputtering, by applying microwave (MW) plasma treatments with Ar discharges at different pressures. The microstructural properties of the differently processed films have been obtained prior to a study by grazing incidence X-ray fluorescence (GI-XRF) spectroscopy, which reveals the in-depth composition trends induced by the two alternative annealing procedures. The final wetting, electrical and optical properties of the films are described in accordance with the Ti distribution pattern revealed by GI-XRF. The study underlines for the first time how MW plasma annealing processes can be used to exacerbate self-induced atomic gradients in sol-gel films with potential implications in catalytic and biomedical applications.