Link between Gas Phase Reaction Chemistry and the Electronic Conductivity of Atomic Layer Deposited Titanium Oxide Thin Films

Babadi, Aein Shiri; Tang‐Kong, Robert; McIntyre, Paul C.

doi:10.1021/acs.jpclett.1c00115

Cited by 8 publications

(7 citation statements)

References 53 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Considering the significantly low resistivity values we have observed, it is reasonable to infer that the subsequent layer of 98 nm of Al 2 O 3 is not being evaluated, as Al 2 O 3 typically exhibits much higher resistivity values, reaching as high as 10 15 Ω cm . The obtained resistivity values are consistent with those of a semiconductor like TiO 2 grown by ALD, as corroborated by previous findings in the literature …”

Section: Resultssupporting

confidence: 90%

“…55 The obtained resistivity values are consistent with those of a semiconductor like TiO 2 grown by ALD, as corroborated by previous findings in the literature. 56 Figure 7b offers a comparative analysis of crystallite size and resistivity with reference to various TiO 2 thin-film literature data. 57−59 Our findings reveal a clear trend where the resistivity of TiO 2 decreases as the grain size increases.…”

Section: Elemental Analysismentioning

confidence: 99%

See 1 more Smart Citation

O₃-Annealing Effect on the Etching Resilience of a TiO₂/Al₂O₃ filter Prepared by Atomic Layer Deposition

Vazquez,

López,

Bohórquez

et al. 2023

ACS Appl. Mater. Interfaces

View full text Add to dashboard Cite

This research investigates the improvements of ozone (O 3 ) annealing on the optical and etching characteristics of TiO 2 /Al 2 O 3 multilayer band-pass filters designed for potential optoelectronic applications. The band-pass filters were fabricated using atomic layer deposition (ALD), and their performance was systematically analyzed after the addition of O 3 annealing at moderate temperatures (up to 300 °C). Results reveal that O 3 annealing improves the optical transmittance of the multilayers by approximately 40% without significant spectral changes (∼6 nm). The observed enhancement in the transmittance is attributed to the improved stoichiometry of TiO 2 . By filling in the oxygen vacancies created during the fabrication process, it reduces its extinction coefficient. Furthermore, the O 3 annealing enhances the stability of TiO 2 against wet etching, improving the uniformity of etched surfaces. Etching on the ozoneannealed multilayer was up to 8 times more homogeneous, as observed in the roughness. The relatively short duration of the O 3 annealing process, approximately 1.6 h, makes it a cost-effective alternative compared to using ozone in the ALD process, which can last several hours for thick optical coatings.

show abstract

Section: Resultssupporting

confidence: 90%

Section: Elemental Analysismentioning

confidence: 99%

O₃-Annealing Effect on the Etching Resilience of a TiO₂/Al₂O₃ filter Prepared by Atomic Layer Deposition

Vazquez,

López,

Bohórquez

et al. 2023

ACS Appl. Mater. Interfaces

View full text Add to dashboard Cite

show abstract

“…Indeed, the most common TiO 2 defect is oxygen vacancies which create unpaired electrons or Ti 3+ centers [25]. In 2021, Babadi et al sought to identify the cause of increased electronic conductivity in TDMAT-TiO 2 thin films [26]. Babadi et al found that the reaction by-product from the TDMAT/H 2 O ALD process, dimethylamine (DMA), can act as a reducing agent for TiO 2 .…”

Section: Introductionmentioning

confidence: 99%

“…Babadi et al found that the reaction by-product from the TDMAT/H 2 O ALD process, dimethylamine (DMA), can act as a reducing agent for TiO 2 . Increased exposure of TiO 2 thin films to DMA caused an increase in electrical conductivity and an increase in the concentration of Ti in the 3+ oxidation state [26]. Finally, in 2022, Saari et al reported a comprehensive electron and optical absorption spectroscopy study finding that the concentration of intrinsic Ti 3+ defects in amorphous TiO 2 -ALD films can be controlled by varying deposition temperatures from 100 to 200 °C [27].…”

Section: Introductionmentioning

confidence: 99%

Crystalline as-deposited TiO 2 anatase thin films grown from TDMAT and water using thermal atomic layer deposition with in situ layer-by-layer air annealing

Wooding,

Kalaitzidou,

Losego

2024

ALD

View full text Add to dashboard Cite

We report a new thermal atomic layer deposition (thermal-ALD) process including an air exposure as a third precursor to deposit crystalline TiO2 anatase thin films from tetrakis(dimethylamido)titanium(IV) (TDMAT) and water at deposition temperatures as low as 180 °C and film thicknesses as low as 10 nm. This ALD process enables TiO2-antase crystal growth during the deposition at low temperatures (< 220 °C). This additional oxidant pulse is used to fully oxidize the Ti to a 4+ state in the amorphous film, lowering the barrier to crystalline anatase formation. This new approach is informed by preliminary studies of post-deposition annealing (PDA) of thermal ALD films in both nitrogen and air atmospheres, which demonstrate the importance of having an oxidizing atmosphere to achieve the nucleation of the crystalline anatase phase. This oxidizing atmosphere is subsequently introduced into the ALD cycle as a third precursor and is shown to be more effective and efficient in promoting the crystalline transformation than even by post-deposition annealing. The crystalline anatase phase is verified by Raman spectroscopy and grazing incidence X-ray diffraction (GIXRD). The mechanism for crystallization during the TDMAT/H2O/air ALD cycle is probed by chemical state analysis via X-ray photoelectron spectroscopy (XPS). We propose that sub-oxidation in TiO2 thin films deposited by the thermal-ALD process inhibits crystallization during ALD from TDMAT/H2O chemistry. Scanning electron microscopy (SEM) is used to investigate the microstructure of these TiO2 thin films as a function of thickness (5 nm to 50 nm) and deposition temperature (180 °C to 220 °C). The reported layer-by-layer air anneal process is found to crystallize entire films in shorter total process times than thermal-ALD with ex situ post deposition annealing at identical temperatures, presumably due to the improved surface diffusion kinetics accessed during the deposition process.

show abstract

“…However, TDMAT/H 2 O films are nearly always amorphous as-deposited, [18,20,21] given that the ALD deposition temperature window is limited by TDMAT's decomposition temperature of approximately 220 °C. [22] Studies on ALD TiO 2 deposited from TDMAT/H 2 O report a variety of electronic properties, [7,23] inspiring a report from Babadi et al probing the gas phase reactions and ALD cycle time [24]. However, few studies exist on post-deposition crystallization of TDMAT/H 2 O-based ALD TiO 2 thin films, [25 ,26 ,27, 28] and these studies do not go into microstructural detail at low annealing temperatures.…”

Section: Introductionmentioning

confidence: 99%

Transformation kinetics for low temperature post-deposition crystallization of TiO 2 thin films prepared via atomic layer deposition (ALD) from tetrakis(dimethylamino)titanium(IV) (TDMAT) and water

Wooding¹,

Gregory²,

Atassi³

et al. 2023

ALD

View full text Add to dashboard Cite

Background: We report on the fundamental crystallization kinetics of atomic layer deposited (ALD) TiO2 thin films undergoing a post-deposition anneal (PDA) at low temperatures to probe differences in the as-deposited film microstructure. Methods: The system of study is ALD TiO2 thin films prepared from tetrakis(dimethylamino)titanium(IV) (TDMAT) and water at 120 °C, 140 °C and 160 °C followed by ex situ low temperature annealing at temperatures ranging from 140 °C to 220 °C. All as-deposited TiO2 thin films are amorphous by X-ray diffraction (XRD). Post-deposition annealing (PDA) produces large grain anatase crystals, confirmed by XRD and top-view scanning electron microscopy (SEM). A detailed SEM study is performed to quantify the nucleation and growth kinetics by fitting microstructural data to the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation. Finally, a time-temperature-transformation (TTT) diagram is constructed to summarize the differences in crystallization behavior at different ALD deposition temperatures. Results and conclusions: Fitting microstructural data to the JMAK equation reveals an Avrami exponent close to 3 with continuous nucleation, suggesting two-dimensional, plate-like crystal growth. Applying an Arrhenius relationship to the phase transformation data, the combined activation energy for nucleation and growth is found to be 1.40–1.58 eV atom-1. Nucleation rates are determined, and an Arrhenius relationship is used to calculate the critical Gibbs free energy for nucleation (~1.3–1.4 eV atom-1). As such, nucleation is the rate-limiting step for the amorphous to anatase phase transformation. ALD growth temperature is found to dictate film microstructure with lower deposition temperatures reducing the nucleation rate and leading to larger grain sizes irrespective of PDA conditions. The nucleation rate pre-exponential frequency factor increases with increasing deposition temperature, thereby increasing the likelihood for nucleation. Interestingly, it is this difference in the vibrational modes of the amorphous structure, as indicated by the variation in the nucleation rate pre-exponential frequency factor, that alters the phase transformation rates and not a change in the activation energies for the transformation.

show abstract

Link between Gas Phase Reaction Chemistry and the Electronic Conductivity of Atomic Layer Deposited Titanium Oxide Thin Films

Cited by 8 publications

References 53 publications

O₃-Annealing Effect on the Etching Resilience of a TiO₂/Al₂O₃ filter Prepared by Atomic Layer Deposition

O₃-Annealing Effect on the Etching Resilience of a TiO₂/Al₂O₃ filter Prepared by Atomic Layer Deposition

Crystalline as-deposited TiO 2 anatase thin films grown from TDMAT and water using thermal atomic layer deposition with in situ layer-by-layer air annealing

Transformation kinetics for low temperature post-deposition crystallization of TiO 2 thin films prepared via atomic layer deposition (ALD) from tetrakis(dimethylamino)titanium(IV) (TDMAT) and water

Contact Info

Product

Resources

About

Link between Gas Phase Reaction Chemistry and the Electronic Conductivity of Atomic Layer Deposited Titanium Oxide Thin Films

Cited by 8 publications

References 53 publications

O3-Annealing Effect on the Etching Resilience of a TiO2/Al2O3 filter Prepared by Atomic Layer Deposition

O3-Annealing Effect on the Etching Resilience of a TiO2/Al2O3 filter Prepared by Atomic Layer Deposition

Crystalline as-deposited TiO 2 anatase thin films grown from TDMAT and water using thermal atomic layer deposition with in situ layer-by-layer air annealing

Transformation kinetics for low temperature post-deposition crystallization of TiO 2 thin films prepared via atomic layer deposition (ALD) from tetrakis(dimethylamino)titanium(IV) (TDMAT) and water

Contact Info

Product

Resources

About

O₃-Annealing Effect on the Etching Resilience of a TiO₂/Al₂O₃ filter Prepared by Atomic Layer Deposition

O₃-Annealing Effect on the Etching Resilience of a TiO₂/Al₂O₃ filter Prepared by Atomic Layer Deposition