scholarly journals Tuning the Band Gap and Carrier Concentration of Titania Films Grown by Spatial Atomic Layer Deposition: A Precursor Comparison

2021 ◽  
Author(s):  
Claire Armstrong ◽  
Louis-Vincent Delumeau ◽  
David Muñoz-Rojas ◽  
Ahmed Kursumovic ◽  
Judith MacManus-Driscoll ◽  
...  
Keyword(s):  
Atomic Layer Deposition ◽  
Band Gap ◽  
Carrier Concentration ◽  
Atomic Layer ◽  
Deposition Rates ◽  
Layer Deposition ◽  
Excellent Control ◽  
Titania Films ◽  
Free Films

Spatial atomic layer deposition retains the advantages of conventional atomic layer deposition: conformal, pinhole-free films and excellent control over thickness. Additionally, it allows higher deposition rates and is well-adapted to...

One-Dimensional TiO2@GaON Core-Shell Nanowires with Controlled Shell Thickness from Atomic Layer Deposition for Stable and Efficient Photoelectrochemical Water Splitting

2019 ◽  
Author(s):  
Jiajia Tao ◽  
Hong-Ping Ma ◽  
Kaiping Yuan ◽  
Yang Gu ◽  
Jianwei Lian ◽  
...  
Keyword(s):  
Atomic Layer Deposition ◽  
Band Gap ◽  
Water Splitting ◽  
Atomic Layer ◽  
Photoelectrochemical Water Splitting ◽  
Core Shell ◽  
Photoelectrochemical Performance ◽  
Highly Efficient ◽  
Layer Deposition ◽  
Shell Nanowires

<div>As a promising oxygen evolution reaction semiconductor, TiO2 has been extensively investigated for solar photoelectrochemical water splitting. Here, a highly efficient and stable strategy for rationally preparing GaON cocatalysts on TiO2 by atomic layer deposition is demonstrated, which we show significantly enhances the</div><div>photoelectrochemical performance compared to TiO2-based photoanodes. For TiO2@20 nm-GaON core-shell nanowires a photocurrent density up to 1.10 mA cm-2 (1.23 V vs RHE) under AM 1.5 G irradiation (100 mW cm-2) has been achieved, which is 14 times higher than that of TiO2 NWs. Furthermore, the oxygen vacancy formation on GaON as well as the band gap matching with TiO2 not only provides more active sites for water oxidation but also enhances light absorption to promote interfacial charge separation and migration. Density functional theory studies of model systems of GaON-modified TiO2 confirm the band gap reduction, high reducibility and ability to activate water. The highly efficient and stable systems of TiO2@GaON core-shell nanowires provide a deeper understanding and universal strategy for enhancing photoelectrochemical performance of photoanodes now available. </div>

scholarly journals Effect of Oxygen Source on the Various Properties of SnO2 Thin Films Deposited by Plasma-Enhanced Atomic Layer Deposition

Coatings ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 692
Author(s):  
Jong Hyeon Won ◽  
Seong Ho Han ◽  
Bo Keun Park ◽  
Taek-Mo Chung ◽  
Jeong Hwan Han
Keyword(s):  
Electrical Properties ◽  
Atomic Layer Deposition ◽  
Carrier Concentration ◽  
High Mobility ◽  
Impurity Scattering ◽  
Atomic Layer ◽  
Growth Behavior ◽  
Layer Deposition ◽  
Growth Feature ◽  
O2 Plasma

Herein, we performed a comparative study of plasma-enhanced atomic layer deposition (PEALD) of SnO2 films using Sn(dmamp)2 as the Sn source and either H2O plasma or O2 plasma as the oxygen source in a wide temperature range of 100–300 °C. Since the type of oxygen source employed in PEALD determines the growth behavior and resultant film properties, we investigated the growth feature of both SnO2 PEALD processes and the various chemical, structural, morphological, optical, and electrical properties of SnO2 films, depending on the oxygen source. SnO2 films from Sn(dmamp)2/H2O plasma (SH-SnO2) and Sn(dmamp)2/O2 plasma (SO-SnO2) showed self-limiting atomic layer deposition (ALD) growth behavior with growth rates of ~0.21 and 0.07–0.13 nm/cycle, respectively. SO-SnO2 films showed relatively larger grain structures than SH-SnO2 films at all temperatures. Interestingly, SH-SnO2 films grown at high temperatures of 250 and 300 °C presented porous rod-shaped surface morphology. SO-SnO2 films showed good electrical properties, such as high mobility up to 27 cm2 V−1·s−1 and high carrier concentration of ~1019 cm−3, whereas SH-SnO2 films exhibited poor Hall mobility of 0.3–1.4 cm2 V−1·s−1 and moderate carrier concentration of 1 × 1017–30 × 1017 cm−3. This may be attributed to the significant grain boundary and hydrogen impurity scattering.

scholarly journals Air Annealing Effect on Oxygen Vacancy Defects in Al-doped ZnO Films Grown by High-Speed Atmospheric Atomic Layer Deposition

Molecules ◽  
2020 ◽  
Vol 25 (21) ◽  
pp. 5043
Author(s):  
Chia-Hsun Hsu ◽  
Xin-Peng Geng ◽  
Wan-Yu Wu ◽  
Ming-Jie Zhao ◽  
Xiao-Ying Zhang ◽  
...  
Keyword(s):  
Atomic Layer Deposition ◽  
Band Gap ◽  
Photoelectron Spectroscopy ◽  
High Speed ◽  
Oxygen Vacancies ◽  
Annealing Temperature ◽  
Atomic Layer ◽  
Zno Films ◽  
X Ray ◽  
Layer Deposition

In this study, aluminum-doped zinc oxide (Al:ZnO) thin films were grown by high-speed atmospheric atomic layer deposition (AALD), and the effects of air annealing on film properties are investigated. The experimental results show that the thermal annealing can significantly reduce the amount of oxygen vacancies defects as evidenced by X-ray photoelectron spectroscopy spectra due to the in-diffusion of oxygen from air to the films. As shown by X-ray diffraction, the annealing repairs the crystalline structure and releases the stress. The absorption coefficient of the films increases with the annealing temperature due to the increased density. The annealing temperature reaching 600 °C leads to relatively significant changes in grain size and band gap. From the results of band gap and Hall-effect measurements, the annealing temperature lower than 600 °C reduces the oxygen vacancies defects acting as shallow donors, while it is suspected that the annealing temperature higher than 600 °C can further remove the oxygen defects introduced mid-gap states.

scholarly journals Atomic Layer Deposition of CeOx Nanoclusters on TiO2

2020 ◽  
Author(s):  
Ji Liu ◽  
Saeed Saedy ◽  
Rakshita Verma ◽  
J. Ruud van Ommen ◽  
Michael Nolan
Keyword(s):  
Atomic Layer Deposition ◽  
Band Gap ◽  
Cerium Oxide ◽  
Growth Rates ◽  
Density Functional ◽  
Visible Region ◽  
Atomic Layer ◽  
Hydroxyl Groups ◽  
Powder Materials ◽  
Layer Deposition

Titanium dioxide has a band-gap in the ultra violet region and there have been many efforts to shift light absorption to the visible region. In this regard, surface modification with metal oxide clusters has been used to promote band-gap reduction. CeO<sub>x</sub>-modified<sub> </sub>TiO<sub>2</sub> materials have exhibited enhanced catalytic activity in water gas shift, but the deposition process used is not well-understood or suitable for powder materials. Atomic layer deposition (ALD) has been used for deposition of cerium oxide on TiO<sub>2</sub>. The experimentally reported growth rates using typical Ce metal precursors such as β-diketonates and cyclopentadienyls are low, with reported growth rates of <i>ca. </i>0.2-0.4 Å/cycle. In this paper, we have performed density functional theory calculations to reveal the reaction mechanism of the metal precursor pulse together with experimental studies of ALD of CeO<sub>x</sub> using two Ce precursors, Ce(TMHD)<sub>4</sub> and Ce(MeCp)<sub>3</sub>. The nature and stability of hydroxyl groups on anatase and rutile TiO<sub>2</sub> surfaces are determined and used as starting substrates. Adsorption of the cerium precursors on the hydroxylated TiO<sub>2</sub> surfaces reduces the coverage of surface hydroxyls. Computed activation barriers for ligand elimination in Ce(MeCp)<sub>3</sub> indicate that ligand elimination is not possible on anatase (101) and rutile (100) surface, but it is possible on anatase (001) and rutile (110). The ligand elimination in Ce(TMHD)<sub>4</sub> is via breaking the Ce-O bond and hydrogen transfer from hydroxyl groups. For this precursor, the ligand elimination on the majority surface facets of anatase and rutile TiO<sub>2</sub> are endothermic and not favourable. It is difficult to deposit Ce atom onto hydroxylated TiO<sub>2</sub> surface using Ce(TMHD)<sub>4</sub> as precursor. Attempts for deposit cerium oxide on TiO<sub>2 </sub>nanoparticles that expose the anatase (101) surface show at best a low deposition rate and this can be explained by the non-favorable ligand elimination reactions at this surface.

scholarly journals Carrier Modulation in Bi2Te3-Based Alloys via Interfacial Doping with Atomic Layer Deposition

Coatings ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 572
Author(s):  
Sang-Soon Lim ◽  
Kwang-Chon Kim ◽  
Seunghyeok Lee ◽  
Hyung-Ho Park ◽  
Seung-Hyub Baek ◽  
...  
Keyword(s):  
Atomic Layer Deposition ◽  
Carrier Concentration ◽  
Atomic Layer ◽  
Thermoelectric Performance ◽  
Fine Powders ◽  
Plasma Sintering ◽  
Novel Approach ◽  
Layer Deposition ◽  
Spark Plasma ◽  
Precursor Powders

The carrier concentration in Bi2Te3-based alloys is a decisive factor in determining their thermoelectric performance. Herein, we propose a novel approach to modulate the carrier concentration via the encapsulation of the alloy precursor powders. Atomic layer deposition (ALD) of ZnO and SnO2 was performed over the Bi2Te2.7Se0.3 powders. After spark plasma sintering at 500 °C for 20 min, the carrier concentration in the ZnO-coated samples decreased, while the carrier concentration in the SnO2-coated samples increased. This trend was more pronounced as the number of ALD cycles increased. This was attributed to the intermixing of the metal ions at the interface. Zn2+ substituted for Bi3+ at the interface acted as an acceptor, while Sn4+ substituted for Bi3+ acted as a donor. This indicates that the carrier concentration can be adjusted depending on the materials deposited with ALD. The use of fine powders changes the carrier concentration more strongly, because the quantity of material deposited increases with the effective surface area. Therefore, the proposed approach would provide opportunities to precisely optimize the carrier concentration for high thermoelectric performance.

scholarly journals Systematic Study of the SiOx Film with Different Stoichiometry by Plasma-Enhanced Atomic Layer Deposition and Its Application in SiOx/SiO2 Super-Lattice

Nanomaterials ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 55 ◽  
Author(s):  
Hong-Ping Ma ◽  
Jia-He Yang ◽  
Jian-Guo Yang ◽  
Li-Yuan Zhu ◽  
Wei Huang ◽  
...  
Keyword(s):  
Atomic Layer Deposition ◽  
Band Gap ◽  
Spectroscopic Ellipsometry ◽  
Energy Band ◽  
Electron Spectroscopy ◽  
Atomic Layer ◽  
Film Deposition ◽  
Energy Band Gap ◽  
X Ray ◽  
Layer Deposition

Atomic scale control of the thickness of thin film makes atomic layer deposition highly advantageous in the preparation of high quality super-lattices. However, precisely controlling the film chemical stoichiometry is very challenging. In this study, we deposited SiOx film with different stoichiometry by plasma enhanced atomic layer deposition. After reviewing various deposition parameters like temperature, precursor pulse time, and gas flow, the silicon dioxides of stoichiometric (SiO2) and non-stoichiometric (SiO1.8 and SiO1.6) were successfully fabricated. X-ray photo-electron spectroscopy was first employed to analyze the element content and chemical bonding energy of these films. Then the morphology, structure, composition, and optical characteristics of SiOx film were systematically studied through atomic force microscope, transmission electron microscopy, X-ray reflection, and spectroscopic ellipsometry. The experimental results indicate that both the mass density and refractive index of SiO1.8 and SiO1.6 are less than SiO2 film. The energy band-gap is approved by spectroscopic ellipsometry data and X-ray photo-electron spectroscopy O 1s analysis. The results demonstrate that the energy band-gap decreases as the oxygen concentration decreases in SiOx film. After we obtained the Si-rich silicon oxide film deposition, the SiO1.6/SiO2 super-lattices was fabricated and its photoluminescence (PL) property was characterized by PL spectra. The weak PL intensity gives us greater awareness that more research is needed in order to decrease the x of SiOx film to a larger extent through further optimizing plasma-enhanced atomic layer deposition processes, and hence improve the photoluminescence properties of SiOx/SiO2 super-lattices.

One-Dimensional TiO2@GaON Core-Shell Nanowires with Controlled Shell Thickness from Atomic Layer Deposition for Stable and Efficient Photoelectrochemical Water Splitting

2019 ◽  
Author(s):  
Jiajia Tao ◽  
Hong-Ping Ma ◽  
Kaiping Yuan ◽  
Yang Gu ◽  
Jianwei Lian ◽  
...  
Keyword(s):  
Atomic Layer Deposition ◽  
Band Gap ◽  
Water Splitting ◽  
Atomic Layer ◽  
Photoelectrochemical Water Splitting ◽  
Core Shell ◽  
Photoelectrochemical Performance ◽  
Highly Efficient ◽  
Layer Deposition ◽  
Shell Nanowires

<div>As a promising oxygen evolution reaction semiconductor, TiO2 has been extensively investigated for solar photoelectrochemical water splitting. Here, a highly efficient and stable strategy for rationally preparing GaON cocatalysts on TiO2 by atomic layer deposition is demonstrated, which we show significantly enhances the</div><div>photoelectrochemical performance compared to TiO2-based photoanodes. For TiO2@20 nm-GaON core-shell nanowires a photocurrent density up to 1.10 mA cm-2 (1.23 V vs RHE) under AM 1.5 G irradiation (100 mW cm-2) has been achieved, which is 14 times higher than that of TiO2 NWs. Furthermore, the oxygen vacancy formation on GaON as well as the band gap matching with TiO2 not only provides more active sites for water oxidation but also enhances light absorption to promote interfacial charge separation and migration. Density functional theory studies of model systems of GaON-modified TiO2 confirm the band gap reduction, high reducibility and ability to activate water. The highly efficient and stable systems of TiO2@GaON core-shell nanowires provide a deeper understanding and universal strategy for enhancing photoelectrochemical performance of photoanodes now available. </div>

scholarly journals Low-temperature grown wurtzite InxGa1−xN thin films via hollow cathode plasma-assisted atomic layer deposition

2015 ◽  
Vol 3 (37) ◽  
pp. 9620-9630 ◽  
Author(s):  
Ali Haider ◽  
Seda Kizir ◽  
Cagla Ozgit-Akgun ◽  
Eda Goldenberg ◽  
Shahid Ali Leghari ◽  
...  
Keyword(s):  
Thin Films ◽  
Low Temperature ◽  
Atomic Layer Deposition ◽  
Band Gap ◽  
Hollow Cathode ◽  
Optical Band Gap ◽  
Atomic Layer ◽  
Cathode Plasma ◽  
Layer Deposition ◽  
Wide Range

Hollow cathode plasma assisted atomic layer deposited InxGa1−xN alloys show successful tunability of the optical band gap by changing the In concentration in a wide range.

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