Atomic layer growth of epitaxial TiO2 thin films from TiCl4 and H2O on α-Al2O3 substrates

Aarik, Jaan; Aidla, Aleks; Mändar, Hugo; Uustare, Teet; Schuisky, Mikael; Hårsta, Anders

doi:10.1016/s0022-0248(02)01426-4

Cited by 83 publications

(60 citation statements)

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“…• C. When comparing our present Raman studies with earlier XRD studies of TiO 2 thin films grown by ALD on silicon and fused silica substrates [20,25], one can see a significant difference. XRD measurements have revealed very low amounts of crystalline phases in the films that were grown at 425-500 • C and evidently contained the anatase as well as rutile phase.…”

Section: Resultsmentioning

confidence: 57%

“…This effect is due to relatively harmless starting materials needed for synthesis of these materials. For instance, metal chlorides or iodides combined with water vapor [19][20][21][22][23][24][25][26] or oxygen [27] can be used as precursors to prepare thin oxide films. By contrast, highly toxic AsH 3 , H 2 Se, and H 2 S are often the starting materials for the synthesis of III-V and II-VI compounds used in electronic and optoelectronic devices.…”

Section: Introductionmentioning

confidence: 99%

“…For instance, TiO 2 , a very promising material for a number of applications, can be stabilized in the amorphous phase [13,20,21,23] and at least five crystalline phases. Anatase [9, 13-15, 17, 19-21, 23-28] and rutile [19][20][21][24][25][26][27] are the crystalline phases that are usually formed at normal and low pressures. In addition, brookite has been observed in TiO 2 single crystals [31], powders [31], and thin films [32] at normal conditions.…”

Section: Introductionmentioning

confidence: 99%

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Structural study of TiO2 thin films by micro-Raman spectroscopy

et al. 2006

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Abstract:The Raman spectroscopy method was used for structural characterization of TiO 2 thin films prepared by atomic layer deposition (ALD) and pulsed laser deposition (PLD) on fused silica and single-crystal silicon and sapphire substrates. Using ALD, anatase thin films were grown on silica and silicon substrates at temperatures 125-425 • C. At higher deposition temperatures, mixed anatase and rutile phases grew on these substrates. Post-growth annealing resulted in anatase-to-rutile phase transitions at 750 • C in the case of pure anatase films. The films that contained chlorine residues and were amorphous in their as-grown stage transformed into anatase phase at 400 • C and retained this phase even after annealing at 900 • C. On single crystal sapphire substrates, phase-pure rutile films were obtained by ALD at 425 • C and higher temperatures without additional annealing. Thin films that predominantly contained brookite phase were grown by PLD on silica substrates using rutile as a starting material.

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Section: Resultsmentioning

confidence: 57%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structural study of TiO2 thin films by micro-Raman spectroscopy

et al. 2006

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“…Same tendency of the surface morphology change was reported by others. [15][16][17] The effect of nucleus density at the lower temperature is more pronounced than that of grain coalescence, thus causes the larger grain size. 17 On the other hand, much denser nuclei are formed at higher temperatures, which results in smaller grains.…”

Section: A Surface Roughness and Crystallizationmentioning

confidence: 99%

Characterization of low temperature deposited atomic layer deposition TiO2 for MEMS applications

Huang

Pandraud

Sarro

2012

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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TiO 2 is an interesting and promising material for micro-/nanoelectromechanical systems (MEMS/ NEMS). For high performance and reliable MEMS/NEMS, optimization of the optical characteristics, mechanical stress, and especially surface smoothness of TiO 2 is required. To overcome the roughness issue of the TiO 2 films due to crystallization during deposition at high temperatures (above 250 C), low temperature (80-120 C) atomic layer deposition (ALD) is investigated. By lowering the deposition temperature, the surface roughness significantly decreases from 3.64 nm for the 300 C deposited crystalline (anatase phase) TiO 2 to 0.24 nm for the 120 C amorphous TiO 2 . However, the layers deposited at low temperature present different physical behaviors comparing to the high temperature ones. The refractive index drops from 2.499 to 2.304 (at 633 nm) and the stress sharply decreases from 684 to 133 MPa. Superhydrophilic surface is obtained for the high temperature deposited TiO 2 under ultraviolet illumination, while little changes are found for the low temperature TiO 2 . The authors demonstrate that by suitable postdeposition annealing, all the properties of the low temperature deposited films recover to that of the 300 C deposited TiO 2 , while the smooth surface profile (less than 1 nm roughness) is maintained. Finally, micromachining of the low temperature ALD TiO 2 by dry etching is also studied.

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“…Although ALD of TiO 2 from TiCl 4 and water has been intensively investigated since the invention of the ALD method, [14][15][16][17][18][19][20][21][22][23][24][25][26][27] the role of HCl is not clear yet. Here we investigate the role of HCl which may be one of origins for the non-ideality in TiO 2 ALD.…”

Section: Introductionmentioning

confidence: 99%

Role of HCl in Atomic Layer Deposition of TiO₂Thin Films from Titanium Tetrachloride and Water

Leem¹,

Park²,

Li³

et al. 2014

Bulletin of the Korean Chemical Society

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Atomic layer deposition (ALD) of TiO 2 thin film from TiCl 4 and H 2 O has been intensively studied since the invention of ALD method to grow thin films via chemical adsorptions of two precursors. However the role of HCl which is a gaseous byproduct in ALD chemistry for TiO 2 growth is still intriguing in terms of the growth mechanism. In order to investigate the role of HCl in TiO 2 ALD, HCl pulse and its purging steps are inserted in a typical sequence of TiCl 4 pulse-purge-H 2 O pulse-purge. When they are inserted after the first-half reaction (chemisorption of TiCl 4 ), the grown thickness of TiO 2 becomes thinner or thicker at lower or higher growth temperatures than 300 o C, respectively. However the insertion after the second-half reaction (chemisorption of H 2 O) results in severely reduced thicknesses in all growth temperatures. By using the result, we explain the growth mechanism and the role of HCl in TiO 2 ALD.

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Atomic layer growth of epitaxial TiO2 thin films from TiCl4 and H2O on α-Al2O3 substrates

Cited by 83 publications

References 20 publications

Structural study of TiO2 thin films by micro-Raman spectroscopy

Structural study of TiO2 thin films by micro-Raman spectroscopy

Characterization of low temperature deposited atomic layer deposition TiO2 for MEMS applications

Role of HCl in Atomic Layer Deposition of TiO₂Thin Films from Titanium Tetrachloride and Water

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Atomic layer growth of epitaxial TiO2 thin films from TiCl4 and H2O on α-Al2O3 substrates

Cited by 83 publications

References 20 publications

Structural study of TiO2 thin films by micro-Raman spectroscopy

Structural study of TiO2 thin films by micro-Raman spectroscopy

Characterization of low temperature deposited atomic layer deposition TiO2 for MEMS applications

Role of HCl in Atomic Layer Deposition of TiO2Thin Films from Titanium Tetrachloride and Water

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Role of HCl in Atomic Layer Deposition of TiO₂Thin Films from Titanium Tetrachloride and Water