Ti3+ states induced band gap reduction and enhanced visible light absorption of TiO2 nanotube arrays: Effect of the surface solid fraction factor

Aïnouche, L.; Hamadou, L.; Kadri, A.; Benbrahim, N.; Bradai, Djamel

doi:10.1016/j.solmat.2016.03.013

Cited by 32 publications

(10 citation statements)

References 64 publications

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“…10(a) and Table 2, the E g of nanostructured ZnO lms is blue shied from 2.45 to 3.62 eV as the deposition time increased from 2 to 8 h, and then red-shied to 2.78 eV as the deposition time increased to 12 h. The blue shi may be ascribed to the development of a resonance structure in the density of states, as well as a split-off band by introducing deep states in the band gap. 78 Tuning the E g values of ZnO lms by controlling the lm morphology may, therefore, be used for broadening the optoelectronic and photovoltaic applications of these lms. Urbach energy (E U ) refers to the width of the exponential absorption edge (the tail) and can be calculated by the following relations:…”

Section: 76mentioning

confidence: 99%

Nanostructured ZnO thin films for self-cleaning applications

2017

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Controlling the properties of nanostructured zinc oxide (ZnO) is an interesting way to broaden its multifunctionality. ZnO nanostructured films were grown on glass substrates under different conditions by a simple two-step wet chemical method. A low-cost successive ionic layer adsorption and reaction (SILAR) method was used to grow ZnO seed layers at 80 C. Then, different hierarchical based ZnO nanostructured thin films were deposited onto the ZnO seed layers by chemical bath deposition (CBD).The influence of deposition time (t D ) and pH on the surface morphology, wettability behavior, structural and optical properties of the ZnO nanostructured films were systematically investigated. The structural, morphological, optical and wetting properties were studied by X-ray diffraction (XRD), field emission scanning microscopy (FE-SEM), UV-Vis spectrophotometer, and water contact angle (WCA) measurement, respectively. The surface morphology revealed a complex and orientated hierarchical based ZnO nanostructured films with diverse shapes from hexagonal nanorods to hexagonal nanoplates and even much more complex plates/rods and flower-like shapes by changing deposition time and pH of the precursor. XRD results confirm the synthesis of nanostructured ZnO of the hexagonal structure with a preferential orientation along the (002) lattice plane. The average crystallite size, D, is altered between 41.41 to 68.43 nm dependent on the morphology of the ZnO film and pH of the precursor. At pH 6.5, the films are hydrophilic for 10 h # t D # 6 h and hydrophobic for 6 h < t D < 10 h. The wetting properties of the films were enhanced by increasing or decreasing pH around 6.5. Morphology and thickness of the ZnO nanostructure could efficiently control the transmittance, absorbance, optical band gap, and the extinction coefficient of the films. The optical band gap is blue shifted from 2.45 to 3.62 eV@pH 6.5 as the deposition time increased from 2 to 8 h and blue shifted from 2.72 to 3.62 eV@8 h as the pH value increased from 5.5 to 6.5. The existence of stable hydrophobic zinc oxide nanostructured films at room temperature at a large-scale and with band gaps around 3.62 eV supports their use in selfcleaning and gas sensing applications.

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Section: 76mentioning

confidence: 99%

Nanostructured ZnO thin films for self-cleaning applications

2017

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“…The Eg of nanostructured RW is blue-shifted from 3.62 to 1.55 eV as the particle size of natural RW increased from RW 0.03 to RW >0.3 . The blue shift may be related to the development of a resonance structure (state) in the density of states and the split-off band by introducing deep states into the bandgap [79]. From Figures 1B, 4c and 6b, the RW >0.3 nanopowder is the most suitable for application in water splitting.…”

Section: Optical Analysismentioning

confidence: 97%

Fabrication and Characterization of Nanostructured Rock Wool as a Novel Material for Efficient Water-Splitting Application

et al. 2022

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Rock wool (RW) nanostructures of various sizes and morphologies were prepared using a combination of ball-mill and hydrothermal techniques, followed by an annealing process. Different tools were used to explore the morphologies, structures, chemical compositions and optical characteristics of the samples. The effect of initial particle size on the characteristics and photoelectrochemical performance of RW samples generated hydrothermally was investigated. As the starting particle size of ball-milled natural RW rises, the crystallite size of hydrothermally formed samples drops from 70.1 to 31.7 nm. Starting with larger ball-milled particle sizes, the nanoparticles consolidate and seamlessly combine to form a continuous surface with scattered spherical nanopores. Water splitting was used to generate photoelectrochemical hydrogen using the samples as photocatalysts. The number of hydrogen moles and conversion efficiencies were determined using amperometry and voltammetry experiments. When the monochromatic wavelength of light was increased from 307 to 460 nm for the manufactured RW>0.3 photocatalyst, the photocurrent density values decreased from 0.25 to 0.20 mA/mg. At 307 nm and +1 V, the value of the incoming photon-to-current efficiency was ~9.77%. Due to the stimulation of the H+ ion rate under the temperature impact, the Jph value increased by a factor of 5 when the temperature rose from 40 to 75 °C. As a result of this research, for the first time, a low-cost photoelectrochemical catalytic material is highlighted for effective hydrogen production from water splitting.

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“…It is suggested that oxygen vacancies and Ti 3+ species in TiO 2 are responsible for the formation of midgap energy states. [26][27][28][29] For instance, the oxygen vacancies can create impurity energy levels at around 2.0-2.5 eV above the valence band [26] or 0.75-1.18 eV below the conduction band. [27] In addition, Ti 3+ species can contribute to the narrowing of bandgap by creating states 0.17-0.35 eV below the conduction band edge, [29] allowing enhanced visible light absorption.…”

Section: Electrical and Photoresponse Characteristics Of Tio 2 /Igzo ...mentioning

confidence: 99%

Metal‐Oxide Heterojunction Optoelectronic Synapse and Multilevel Memory Devices Enabled by Broad Spectral Photocarrier Modulation

Kim

Song

Lee

et al. 2023

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Broad spectral response and high photoelectric conversion efficiency are key milestones for realizing multifunctional, low‐power optoelectronic devices such as artificial synapse and reconfigurable memory devices. Nevertheless, the wide bandgap and narrow spectral response of metal‐oxide semiconductors are problematic for efficient metal‐oxide optoelectronic devices such as photonic synapse and optical memory devices. Here, a simple titania (TiO2)/indium‐gallium‐zinc‐oxide (IGZO) heterojunction structure is proposed for efficient multifunctional optoelectronic devices, enabling widen spectral response range and high photoresponsivity. By overlaying a TiO2 film on IGZO, the light absorption range extends to red light, along with enhanced photoresponsivity in the full visible light region. By implementing the TiO2/IGZO heterojunction structure, various synaptic behaviors are successfully emulated such as short‐term memory/long‐term memory and paired pulse facilitation. Also, the TiO2/IGZO synaptic transistor exhibits a recognition rate up to 90.3% in recognizing handwritten digit images. Moreover, by regulating the photocarrier dynamics and retention behavior using gate‐bias modulation, a reconfigurable multilevel (≥8 states) memory is demonstrated using visible light.

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Ti3+ states induced band gap reduction and enhanced visible light absorption of TiO2 nanotube arrays: Effect of the surface solid fraction factor

Cited by 32 publications

References 64 publications

Nanostructured ZnO thin films for self-cleaning applications

Nanostructured ZnO thin films for self-cleaning applications

Fabrication and Characterization of Nanostructured Rock Wool as a Novel Material for Efficient Water-Splitting Application

Metal‐Oxide Heterojunction Optoelectronic Synapse and Multilevel Memory Devices Enabled by Broad Spectral Photocarrier Modulation

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