Plasma-enhanced atomic layer deposition of tungsten oxide thin films using (tBuN)2(Me2N)2W and O2 plasma

Balasubramanyam, Shashank; Sharma, Akhil; Vandalon, Vincent; Knoops, Hcm Harm; Kessels, W.M.M.; Bol, Ageeth A.

doi:10.1116/1.4986202

Cited by 32 publications

(27 citation statements)

References 53 publications

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“…As shown in Figure 2b, the optical indirect band gap of the ALD and the sputtered WO3 film were both close to 3.0 eV. The band gap values correspond to the reported band gap range for bulk material in the literature (2.5 -3.1 eV) 40,[42][43][44] .…”

Section: Structural and Optical Propertiessupporting

confidence: 82%

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Physical and Chemical Defects in WO₃ Thin Films and Their Impact on Photoelectrochemical Water Splitting

Zhao

Balasubramanyam

Sinha

et al. 2018

ACS Appl. Energy Mater.

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We evaluate the impact of defects in WO3 thin films on the photoelectrochemical (PEC) properties during water splitting. We study physical defects, such as micro holes or cracks, by two different deposition techniques: sputtering and atomic layer deposition (ALD). Chemical defects, such as oxygen vacancies, are tailored by different annealing atmospheres, i.e. air, N2, and O2. The results show that the physical defects inside the film increase the resistance for the charge transfer and also result in a higher recombination rate which inhibits the photocurrent generation. Chemical defects yield in an increased adsorption of OH groups on the film surface and enhance the PEC efficiency. Excess amount of chemical defects can also inhibit the electron transfer, thus decreasing the photocurrent generation. In this study, the highest performance was obtained for WO3 films deposited by ALD and annealed in air, which have the least physical defects and an appropriate amount of oxygen vacancies.

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Section: Structural and Optical Propertiessupporting

confidence: 82%

“…The main parameters of the ALD process are listed in Table 2. The plasma enhanced ALD process is described in detail in 40 . Table 1 Sputtering process parameters for WO3 deposition.…”

Section: Introductionmentioning

confidence: 99%

Physical and Chemical Defects in WO₃ Thin Films and Their Impact on Photoelectrochemical Water Splitting

Zhao

Balasubramanyam

Sinha

et al. 2018

ACS Appl. Energy Mater.

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“…The tungsten precursor used in this work was previously used to deposit WO 3 in a PEALD process over a wide temperature range from 100 to 400 °C, with little to no carbon impurity incorporation. 55 In the investigated temperature range, the precursor was found to be thermally stable without any signs of thermal decomposition. In this work, depositions were carried out at 300 °C as this was the lowest temperature at which the WS 2 films crystallized.…”

Section: Methodsmentioning

confidence: 90%

Edge-Site Nanoengineering of WS₂ by Low-Temperature Plasma-Enhanced Atomic Layer Deposition for Electrocatalytic Hydrogen Evolution

et al. 2019

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Edge-enriched transition metal dichalcogenides, such as WS 2 , are promising electrocatalysts for sustainable production of H 2 through the electrochemical hydrogen evolution reaction (HER). The reliable and controlled growth of such edge-enriched electrocatalysts at low temperatures has, however, remained elusive. In this work, we demonstrate how plasma-enhanced atomic layer deposition (PEALD) can be used as a new approach to nanoengineer and enhance the HER performance of WS 2 by maximizing the density of reactive edge sites at a low temperature of 300 °C. By altering the plasma gas composition from H 2 S to H 2 + H 2 S during PEALD, we could precisely control the morphology and composition and, consequently, the edge-site density as well as chemistry in our WS 2 films. The precise control over edge-site density was verified by evaluating the number of exposed edge sites using electrochemical copper underpotential depositions. Subsequently, we demonstrate the HER performance of the edge-enriched WS 2 electrocatalyst, and a clear correlation among plasma conditions, edge-site density, and the HER performance is obtained. Additionally, using density functional theory calculations we provide insights and explain how the addition of H 2 to the H 2 S plasma impacts the PEALD growth behavior and, consequently, the material properties, when compared to only H 2 S plasma.

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“…Recipes involve the sequential use of a metal precursor (metal-halide, or metal-organic), a purging mechanism using an inert gas, and an oxygen source (often H 2 O, O 3 , or plasma excited O 2 ) [51][52][53] . Use of plasma results in improved material properties such as high density as well as low-impurity content at lower deposition temperatures, while the growth per cycle is still comparable with non-plasma ALD processes 54 . Xie et al compared precursors tetrakis(dimethylamido) titanium (TDMAT) and titanium tetraisopropoxide (TTIP) in combination with either water vapor, H 2 O plasma, or oxygen plasma 55 .…”

mentioning

confidence: 99%

“…Xie et al compared precursors tetrakis(dimethylamido) titanium (TDMAT) and titanium tetraisopropoxide (TTIP) in combination with either water vapor, H 2 O plasma, or oxygen plasma 55 . Balasubramanyam et al reported use of (tBuN) 2 (Me 2 N) 2 W and O 2 plasma for growth of WO 3 thin films 54 . H 2 O has been used routinely as a precursor in ALD, for example, for alumina and hafnium oxide 56,57 .…”

mentioning

confidence: 99%

Precursor-surface interactions revealed during plasma-enhanced atomic layer deposition of metal oxide thin films by in-situ spectroscopic ellipsometry

Kılıç

Mock

Sekora

et al. 2020

Sci Rep

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We find that a five-phase (substrate, mixed native oxide and roughness interface layer, metal oxide thin film layer, surface ligand layer, ambient) model with two-dynamic (metal oxide thin film layer thickness and surface ligand layer void fraction) parameters (dynamic dual box model) is sufficient to explain in-situ spectroscopic ellipsometry data measured within and across multiple cycles during plasma-enhanced atomic layer deposition of metal oxide thin films. We demonstrate our dynamic dual box model for analysis of in-situ spectroscopic ellipsometry data in the photon energy range of 0.7-3.4 eV measured with time resolution of few seconds over large numbers of cycles during the growth of titanium oxide (TiO 2) and tungsten oxide (WO 3) thin films, as examples. We observe cyclic surface roughening with fast kinetics and subsequent roughness reduction with slow kinetics, upon cyclic exposure to precursor materials, leading to oscillations of the metal thin film thickness with small but positive growth per cycle. We explain the cyclic surface roughening by precursor-surface interactions leading to defect creation, and subsequent surface restructuring. Atomic force microscopic images before and after growth, x-ray photoelectron spectroscopy, and x-ray diffraction investigations confirm structural and chemical properties of our thin films. Our proposed dynamic dual box model may be generally applicable to monitor and control metal oxide growth in atomic layer deposition, and we include data for Sio 2 and Al 2 o 3 as further examples. Transition metal oxides (TMOs) are subject of contemporary interest for many applications. A wide range of interesting electrical, optical, electrochromic, and photocatalytic properties make TMOs attractive for device applications 1-6. TMOs are being exploited, for example, as efficient light absorber materials in photo-voltaic devices 7,8 , as ion-transport, and/or ion-storage materials in rechargeable batteries 9 , as active materials in switchable electrochromic optical windows 10-12 , in low-earth-orbit protective coatings for all-solid-state electrochromic surface heat radiation control devices 13,14 , in gas sensing devices 15,16 , and in photo-catalysis devices 6. TMOs are often fabricated as thin films, where fabrication conditions critically influence the resulting thin film properties 17-19. Various growth processes for the fabrication of TMO thin films have been developed by utilizing physical vapor deposition (PVD) such as magnetron sputtering 20-22 , thermal evaporation 23,24 , and chemical vapor deposition (CVD) 25-27. Thin films deposited by PVD processes are often affected by thickness and composition non-uniformity. Adhesion failure and non-homogeneous coverage across highly-faceted surfaces are often reported 28-30. CVD processes enable deposition of highly uniform thin films in the thickness range of nanometers to many micrometers 31-33. However, CVD growth processes critically depend on reaction conditions such as

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Plasma-enhanced atomic layer deposition of tungsten oxide thin films using (tBuN)2(Me2N)2W and O2 plasma

Abstract: Plasma-enhanced atomic layer deposition of tungsten oxide thin films using (tBuN)2(Me2N)2W and O2 plasma.

Cited by 32 publications

References 53 publications

Physical and Chemical Defects in WO₃ Thin Films and Their Impact on Photoelectrochemical Water Splitting

Physical and Chemical Defects in WO₃ Thin Films and Their Impact on Photoelectrochemical Water Splitting

Edge-Site Nanoengineering of WS₂ by Low-Temperature Plasma-Enhanced Atomic Layer Deposition for Electrocatalytic Hydrogen Evolution

Precursor-surface interactions revealed during plasma-enhanced atomic layer deposition of metal oxide thin films by in-situ spectroscopic ellipsometry

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Plasma-enhanced atomic layer deposition of tungsten oxide thin films using (tBuN)2(Me2N)2W and O2 plasma

Abstract: Plasma-enhanced atomic layer deposition of tungsten oxide thin films using (tBuN)2(Me2N)2W and O2 plasma.

Cited by 32 publications

References 53 publications

Physical and Chemical Defects in WO3 Thin Films and Their Impact on Photoelectrochemical Water Splitting

Physical and Chemical Defects in WO3 Thin Films and Their Impact on Photoelectrochemical Water Splitting

Edge-Site Nanoengineering of WS2 by Low-Temperature Plasma-Enhanced Atomic Layer Deposition for Electrocatalytic Hydrogen Evolution

Precursor-surface interactions revealed during plasma-enhanced atomic layer deposition of metal oxide thin films by in-situ spectroscopic ellipsometry

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Physical and Chemical Defects in WO₃ Thin Films and Their Impact on Photoelectrochemical Water Splitting

Physical and Chemical Defects in WO₃ Thin Films and Their Impact on Photoelectrochemical Water Splitting

Edge-Site Nanoengineering of WS₂ by Low-Temperature Plasma-Enhanced Atomic Layer Deposition for Electrocatalytic Hydrogen Evolution