Thin high-dielectric TiO2 films prepared by low pressure MOCVD

Rausch, N.; Burte, Edmund P.

doi:10.1016/0167-9317(92)90531-u

Cited by 40 publications

(26 citation statements)

References 3 publications

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“…8 In addition, studies of TiO 2 as a gate dielectric have shown that TiO 2 can be "leaky" with respect to electronic conduction, which has often been attributed to high concentrations of Ti 3+ or other electronic defects. [20][21][22][23][24] TiO 2 is a versatile material that features a stable amorphous structure as well as various crystalline phases, of which anatase and rutile are the most common. As in many metal oxides, the concentration of oxygen vacancies (which can vary depending on fabrication methods and processing conditions) controls the concentration of free carriers and thus the conductivity.…”

Section: Introductionmentioning

confidence: 99%

The Influence of Structure and Processing on the Behavior of TiO₂ Protective Layers for Stabilization of n-Si/TiO₂/Ni Photoanodes for Water Oxidation

McDowell

Lichterman

Carim

et al. 2015

ACS Appl. Mater. Interfaces

118

158

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Light absorbers with moderate band gaps (1−2 eV) are required for high-efficiency solar fuels devices, but most semiconducting photoanodes undergo photocorrosion or passivation in aqueous solution. Amorphous TiO 2 deposited by atomic-layer deposition (ALD) onto various n-type semiconductors (Si, GaAs, GaP, and CdTe) and coated with thin films or islands of Ni produces efficient, stable photoanodes for water oxidation, with the TiO 2 films protecting the underlying semiconductor from photocorrosion in pH = 14 KOH(aq). The links between the electronic properties of the TiO 2 in these electrodes and the structure and energetic defect states of the material are not yet wellelucidated. We show herein that TiO 2 films with a variety of crystal structures and midgap defect state distributions, deposited using both ALD and sputtering, form rectifying junctions with n-Si and are highly conductive toward photogenerated carriers in n-Si/TiO 2 /Ni photoanodes. Moreover, the photovoltage of these electrodes can be modified by annealing the TiO 2 in reducing or oxidizing environments. All of the polycrystalline TiO 2 films with compact grain boundaries investigated herein protected the n-Si photoanodes against photocorrosion in pH = 14 KOH(aq). Hence, in these devices, conduction through the TiO 2 layer is neither specific to a particular amorphous or crystalline structure nor determined wholly by a particular extrinsic dopant impurity. The coupled structural and energetic properties of TiO 2 , and potentially other protective oxides, can therefore be controlled to yield optimized photoelectrode performance.

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Section: Introductionmentioning

confidence: 99%

The Influence of Structure and Processing on the Behavior of TiO₂ Protective Layers for Stabilization of n-Si/TiO₂/Ni Photoanodes for Water Oxidation

McDowell

Lichterman

Carim

et al. 2015

ACS Appl. Mater. Interfaces

118

158

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“…RF magnetron sputtering [10][11][12] is one of the most utilized methods for obtaining uniform and dense TiO 2 thin films with well-controlled stoichiometry. In this paper, we present the influence of the growth temperature on the properties of TiO 2 thin films deposited on glass and p-Si substrates.…”

Section: Introductionmentioning

confidence: 99%

“…It is found to exhibit interesting properties (high permittivity and refractive index [1,2], good durability, biocompatibility etc. ), which makes it a promising material for gas sensors [3,4], solar cells [5,6] antireflection coatings [7], multilayer optical coatings [8], optical wave guides [9], dielectrics in memory cell capacitors [10] for static random access memory (SRAM) applications [11,12] and more recently as the body oxide of tunnel transistors or of metal oxide semiconductor transistor (MOS) [3,4,10]. As pure material, stoichiometric TiO 2 can absorb a small percentage of the sunlight.…”

Section: Introductionmentioning

confidence: 99%

Effect of the substrate temperature on the properties of the RF sputtered TiO₂ thin films

Mbarek

Chaabouni

Selmi

et al. 2010

Phys. Status Solidi (c)

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Titanium dioxide (TiO2) thin films were deposited by RF magnetron sputtering on glass and silicon substrates at different substrate temperatures (20, 100, 200 and 300 °C). The structural and morphological characteristics of the films were investigated by X ray Diffractometry (XRD) and Atomic Force Microscopy (AFM) while the optical properties of the films were studied by optical spectroscopy. It was shown that at room temperature, TiO2 films grown on glass were amorphous following the substrate structure. At higher temperatures, XRD detected only a nanocrystalline rutile TiO2 structure. This indicated that the transition temperature toward the most stable TiO2 phase was obtained from 100 °C and the crystallinity was enhanced at higher growth temperature. For TiO2 films grown on Si substrates, only a nanocrystalline anatase TiO2 structure was obtained at room temperature. At higher temperatures, we noticed the appearance of other secondary phases related to rutile, anatase and brookite structures. From AFM images, we noticed that at room temperature, the films were porous. With increasing the temperature, the structure of the films became crystallized showing a columnar structure. Film growth and structural properties were discussed in terms of the Thornton model. From optical analysis, the films were transparent with an indirect band gap and a refraction index which reached 3.09 eV and 2.7, respectively. The reflectance and transmittance spectra showed, not only that there was a little translation from UVB to UVA and near‐visible range, but also a decrease of reflection with a temperature increase indicating that the films could be used as anti‐reflection coatings. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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“…6,7 With its extraordinarily high dielectric constant, TiO 2 thin films are a leading candidate for both memory and thin-film transistor applications. 8,9 A variety of synthesis techniques have been used, including chemical vapor deposition ͑CVD͒, 8,10 sputtering, 1,2 plasma-enhanced CVD ͑PECVD͒, 11,12 and atomic layer deposition ͑ALD͒. 4,5,[13][14][15][16][17][18] Emerging applications demand improved quality and control.…”

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confidence: 99%

Self-Limiting Deposition of Anatase TiO[sub 2] at Low Temperature by Pulsed PECVD

Kubala

Rowlette

Wolden

2009

Electrochem. Solid-State Lett.

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The self-limiting deposition of anatase TiO 2 was accomplished by pulsed plasma-enhanced chemical vapor deposition ͑PECVD͒ using a simultaneous delivery of TiCl 4 and O 2 . The amorphous to anatase phase transition was examined as a function of temperature, plasma power, and film thickness. Films deposited at T = 120°C, with the plasma power set at 100 W were amorphous, containing residual amounts of chlorine. At 200 W, the films displayed an anatase structure, and no chlorine was detected by X-ray photoelectron spectroscopy. Spectroscopic ellipsometry, Fourier transform infrared, and X-ray diffraction measurements concur that a minimum film thickness of ϳ25 nm is required for the formation of the anatase phase.Titanium dioxide ͑TiO 2 ͒ thin films are of major technological interest due to their versatile physical and chemical attributes. Titania's high refractive index makes it a common component in optical filters and coatings. 1,2 TiO 2 is a leading photocatalyst 3-5 and serves as a critical component in emerging photovoltaic technology. 6,7 With its extraordinarily high dielectric constant, TiO 2 thin films are a leading candidate for both memory and thin-film transistor applications. 8,9 A variety of synthesis techniques have been used, including chemical vapor deposition ͑CVD͒, 8,10 sputtering, 1,2 plasma-enhanced CVD ͑PECVD͒, 11,12 and atomic layer deposition ͑ALD͒. 4,5,13-18 Emerging applications demand improved quality and control. ALD imparts digital control over film thickness and composition, as well as exceptional film quality. The main drawback of ALD is its low rate, which precludes its use for the commercial synthesis of mesoscale structures ͑100-1000 nm͒ for single-wafer processing such as optical components. ALD typically requires temperatures Ͼ200°C to produce the anatase phase, which is desired for photocatalyst applications. In this article, we describe the selflimiting production of anatase films by pulsed PECVD at temperatures well below 200°C.Our group has established pulsed PECVD as an alternative to ALD for the self-limiting growth of metal oxide thin films, including Ta 2 O 5 , 19,20 Al 2 O 3 , 21,22 and ZnO. 23 The process has been described in detail previously 24,25 and is briefly reviewed here. In pulsed PECVD, O 2 and the metal precursor are mixed and delivered simultaneously. To be self-limiting, the precursor must be unreactive with O 2 so that no deposition occurs with the plasma off. TiCl 4 is unreactive with O 2 below 400°C, 10 but other precursors such as TiI 4 that are reactive with O 2 26 would not produce self-limiting growth by this technique. Purge steps are eliminated, and growth occurs discretely by modulating the plasma power at low frequency ͑ap-proximately in hertz͒. The nature of the self-limiting growth is fundamentally different from ALD. Instead of relying on surface chemistry, growth terminates during each plasma step due to the consumption of the precursor. The process is self-limiting in the sense that no deposition occurs with the plasma off or with the plas...

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Thin high-dielectric TiO2 films prepared by low pressure MOCVD

Cited by 40 publications

References 3 publications

The Influence of Structure and Processing on the Behavior of TiO₂ Protective Layers for Stabilization of n-Si/TiO₂/Ni Photoanodes for Water Oxidation

The Influence of Structure and Processing on the Behavior of TiO₂ Protective Layers for Stabilization of n-Si/TiO₂/Ni Photoanodes for Water Oxidation

Effect of the substrate temperature on the properties of the RF sputtered TiO₂ thin films

Self-Limiting Deposition of Anatase TiO[sub 2] at Low Temperature by Pulsed PECVD

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Thin high-dielectric TiO2 films prepared by low pressure MOCVD

Cited by 40 publications

References 3 publications

The Influence of Structure and Processing on the Behavior of TiO2 Protective Layers for Stabilization of n-Si/TiO2/Ni Photoanodes for Water Oxidation

The Influence of Structure and Processing on the Behavior of TiO2 Protective Layers for Stabilization of n-Si/TiO2/Ni Photoanodes for Water Oxidation

Effect of the substrate temperature on the properties of the RF sputtered TiO2 thin films

Self-Limiting Deposition of Anatase TiO[sub 2] at Low Temperature by Pulsed PECVD

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The Influence of Structure and Processing on the Behavior of TiO₂ Protective Layers for Stabilization of n-Si/TiO₂/Ni Photoanodes for Water Oxidation

The Influence of Structure and Processing on the Behavior of TiO₂ Protective Layers for Stabilization of n-Si/TiO₂/Ni Photoanodes for Water Oxidation

Effect of the substrate temperature on the properties of the RF sputtered TiO₂ thin films