Incorporation of La in epitaxial SrTiO3 thin films grown by atomic layer deposition on SrTiO3-buffered Si (001) substrates

McDaniel, Martin D.; Posadas, Agham; Ngo, Thong Q.; Karako, Christine M.; Bruley, J.; Frank, Martin M.; Narayanan, V.; Demkov, Alexander A.; Ekerdt, John G.

doi:10.1063/1.4883767

Cited by 18 publications

(5 citation statements)

References 46 publications

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“…The binding energy of Sr 3d 5/2 is 134.2 eV, which is between the energy of pure SrO (133.7 eV) and SrCO 3 (134.9 eV) . For Si 2p spectra, the doublet peaks (cutoff) at low binding energies are from the Si substrate, while the peak located at 103.6 eV is attributed to SiO 2 . , The peak with intermediate binding energy (101.8 eV) represents the formation of Sr silicate, which is similar to bonding observed in molecular beam epitaxy studies. , Growth at 350 °C also leads to spontaneous silicate formation, which is included in Figureb. The silicate peak is larger for the same number of cycles due to the increased GPC, as shown in Figure.…”

Section: Resultssupporting

confidence: 54%

“…The growth of metal oxides is one of the most extensively studied and promising areas for application of ALD. In particular, SrO ALD is used for the ALD of the ternary strontium titanate (STO), which is of major interest for use with high-density metal–insulator–metal (MIM) capacitors. , SrO is also of interest for the growth of epitaxial perovskite oxides on semiconductors where it acts as a buffer layer between the reactive semiconductor and metal oxide layers. − …”

Section: Introductionmentioning

confidence: 99%

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Nucleation, Hydroxylation, and Crystallization Effects in ALD SrO

Wang

Jiang

et al. 2013

J. Phys. Chem. C

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The atomic layer deposition (ALD) of SrO thin films from strontium bis(tri(isopropyl)cyclopentadienyl) (Sr-(C 5 i Pr 3 H 2 ) 2 ) and H 2 O was studied by using in situ real-time spectroscopic ellipsometry (RTSE), ex situ X-ray photoelectron spectroscopy (XPS), and grazing-incidence X-ray diffraction (GI-XRD). It is found that with H 2 O as the oxidant, deposition temperature strongly affects film composition. At 250°C films consist of polycrystalline Sr(OH) 2 while at 350°Cpolycrystalline SrO is observed. The growth per cycle (GPC) is found to be sensitive not only to the crystalline phase (Sr(OH) 2 vs SrO) but also the crystalline orientation. For films prepared at high temperatures and subsequently cooled for continued growth at lower temperatures, an unusual transient growth per cycle (GPC) enhancement of over 160% for more than 100 cycles is observed. The enhancement is found to be related to the orientation of the Sr(OH) 2 phase, which is influenced by the underlying crystal texture of the substrate. Substrate nucleation effects were also observed for growth on SiO 2 /Si substrates. A Sr silicate layer with stoichiometry close to Sr 2 SiO 4 forms spontaneously during ALD growth and transiently enhances the GPC. ■ INTRODUCTIONAtomic layer deposition (ALD) has attracted much attention in thin film deposition due to its capability for accurate thickness control and superior conformal growth. 1 Challenges for ALD include nonideal nucleation and substrate effects often encountered at the interfaces between dissimilar materials. 2−4 These substrate effects are particularly problematic for the growth of more complicated materials like ternary systems because of the difficulty encountered in achieving steady, predictable growth. 5 The growth of metal oxides is one of the most extensively studied and promising areas for application of ALD. In particular, SrO ALD is used for the ALD of the ternary strontium titanate (STO), which is of major interest for use with high-density metal−insulator−metal (MIM) capacitors. 6,7 SrO is also of interest for the growth of epitaxial perovskite oxides on semiconductors where it acts as a buffer layer between the reactive semiconductor and metal oxide layers. 8−12 Atomic layer deposition (ALD) of strontium oxide (SrO) has been demonstrated to show nonideal growth characteristics, and properties such as ALD growth window and precursor decomposition temperatures are controversial. 3,6,13,14 The strong basicity of SrO makes ALD-grown SrO films chemically unstable if exposed to air (moisture and CO 2 ). Moreover, traces of Sr(OH) 2 were reported by Vehkamaki et al. in films deposited at 250°C. 13 For films grown at 300°C, crystalline SrO was demonstrated by Rahtu et al. with preferred (111) orientation. 15 At deposition temperatures higher than 300°C, whether the strontium precursor thermally decomposes is still an open question. For example, Rahtu et al. reported that the growth per cycle (GPC) did not saturate as a function of strontium precursor pulse time at 325°C. 3 However, usi...

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Section: Resultssupporting

confidence: 54%

Section: Introductionmentioning

confidence: 99%

Nucleation, Hydroxylation, and Crystallization Effects in ALD SrO

Wang

Jiang

et al. 2013

J. Phys. Chem. C

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“…Both the Sr and Hf metalorganic precursors are commercially available, reactive with water, and have been previously used for ALD. [38][39][40][41][42][43][44][45][46][47][48] Alternating subcycles of Sr and Hf are used to deposit stoichiometric to slightly Sr-rich (56%) films. During each subcycle the metalorganic is dosed for 2 s to ensure complete saturation of the surface, and subsequently purged for 15 s with ultrahigh purity Ar.…”

Section: Methodsmentioning

confidence: 99%

Atomic layer deposition of crystalline SrHfO3 directly on Ge (001) for high-k dielectric applications

McDaniel

et al. 2015

Journal of Applied Physics

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The current work explores the crystalline perovskite oxide, strontium hafnate, as a potential high-k gate dielectric for Ge-based transistors. SrHfO3 (SHO) is grown directly on Ge by atomic layer deposition and becomes crystalline with epitaxial registry after post-deposition vacuum annealing at ∼700 °C for 5 min. The 2 × 1 reconstructed, clean Ge (001) surface is a necessary template to achieve crystalline films upon annealing. The SHO films exhibit excellent crystallinity, as shown by x-ray diffraction and transmission electron microscopy. The SHO films have favorable electronic properties for consideration as a high-k gate dielectric on Ge, with satisfactory band offsets (>2 eV), low leakage current (<10−5 A/cm2 at an applied field of 1 MV/cm) at an equivalent oxide thickness of 1 nm, and a reasonable dielectric constant (k ∼ 18). The interface trap density (Dit) is estimated to be as low as ∼2 × 1012 cm−2 eV−1 under the current growth and anneal conditions. Some interfacial reaction is observed between SHO and Ge at temperatures above ∼650 °C, which may contribute to increased Dit value. This study confirms the potential for crystalline oxides grown directly on Ge by atomic layer deposition for advanced electronic applications.

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“…35,36 Additional possibilities include the potential gate oxide, SrZr x Ti 1-x O 3 . 37 Finally, building on previous studies of ALD perovskite growth on a four-unit cell STO film on Si (001) [29][30][31][32][33][34] suggests that any film that could be grown on the STO/Si platform could be grown on an ALD-grown STO buffer film on Ge, such as LaAlO 3 and LaCoO 3 . 32,38 The multitude of properties available to oxide heterostructures and remarkable similarity between perovskite oxides suggest this procedure could be utilized to study previously difficult or impossible growth combinations with such an industrially viable technique.…”

Section: Introductionmentioning

confidence: 98%

Epitaxial Growth of Perovskite Strontium Titanate on Germanium via Atomic Layer Deposition

Lin

Edmondson

et al. 2016

JoVE

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Atomic layer deposition (ALD) is a commercially utilized deposition method for electronic materials. ALD growth of thin films offers thickness control and conformality by taking advantage of self-limiting reactions between vapor-phase precursors and the growing film. Perovskite oxides present potential for next-generation electronic materials, but to-date have mostly been deposited by physical methods. This work outlines a method for depositing SrTiO3 (STO) on germanium using ALD. Germanium has higher carrier mobilities than silicon and therefore offers an alternative semiconductor material with faster device operation. This method takes advantage of the instability of germanium's native oxide by using thermal deoxidation to clean and reconstruct the Ge (001) surface to the 2×1 structure. 2-nm thick, amorphous STO is then deposited by ALD. The STO film is annealed under ultra-high vacuum and crystallizes on the reconstructed Ge surface. Reflection high-energy electron diffraction (RHEED) is used during this annealing step to monitor the STO crystallization. The thin, crystalline layer of STO acts as a template for subsequent growth of STO that is crystalline as-grown, as confirmed by RHEED. In situ X-ray photoelectron spectroscopy is used to verify film stoichiometry before and after the annealing step, as well as after subsequent STO growth. This procedure provides framework for additional perovskite oxides to be deposited on semiconductors via chemical methods in addition to the integration of more sophisticated heterostructures already achievable by physical methods.

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Incorporation of La in epitaxial SrTiO3 thin films grown by atomic layer deposition on SrTiO3-buffered Si (001) substrates

Cited by 18 publications

References 46 publications

Nucleation, Hydroxylation, and Crystallization Effects in ALD SrO

Nucleation, Hydroxylation, and Crystallization Effects in ALD SrO

Atomic layer deposition of crystalline SrHfO3 directly on Ge (001) for high-k dielectric applications

Epitaxial Growth of Perovskite Strontium Titanate on Germanium via Atomic Layer Deposition

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