Buffer layers for superconducting YBaCuO thin films on silicon and SiO2

Reus, R. de; Saris, F.W.; Kolk, G.J. van der; Witmer, C.H.M.; Dam, B.; Blank, Dave H.A.; Adelerhof, Derk Jan; Flokstra, Jakob

doi:10.1016/0921-5107(90)90018-7

“…These data indicate that the introduction of the heat treatment and the UV/O 3 cleaning in the dry-cleaning procedure strongly smoothens the surface. Further annealing of the amorphous Ta 2 O 5 film to form a polycrystalline Ta 2 O 5 surface will probably be unfavorable for the monolayer formation as it is known to increase the surface roughness dramatically. , In conclusion, minor differences were observed for both cleaned Ta/Ta 2 O 5 surfaces. Due to its slightly thicker, denser, and smoother oxide film, the dry-cleaned substrate was concluded to be the favored cleaning method for the formation of a highly ordered and dense ( n -decyl)trichlorosilane SAM.…”

Section: Resultsmentioning

confidence: 76%

Formation of Dense Self-assembled Monolayers of (n-Decyl)trichlorosilanes on Ta/Ta₂O₅

Palma

¹

,

Laureyn

²

,

Frederix

³

et al. 2006

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Tantalum pentoxide (Ta2O5) is a promising material for the realization of biological interfaces because of its high dielectric constant, its high chemical stability, and its excellent passivating properties. Nevertheless, the deposition of highly organized silane SAMs to realize well-defined and tailored Ta2O5-based (bio)interfaces, has not been studied in great detail as of yet. In this work, we have investigated the formation of a highly ordered, dense monolayer of trichlorosilanes on Ta2O5 surfaces. Specifically, two different cleaning procedures for Ta2O5 were compared and (n-decyl)trichlorosilane (DTS) was used to study the effect of both cleaning methods on the silanization of Ta2O5. Both types of cleaning allowed the formation of complete and crystalline DTS monolayers on Ta2O5, in contrast with the incomplete, disordered silane layer assembled on uncleaned Ta2O5. The deposited self-assembled monolayers were studied by means of contact angle goniometry, Brewster angle FTIR, X-ray photoelectron spectroscopy, cyclic voltammetry, and ellipsometry. Infrared analysis exhibited a highly ordered DTS silane film on Ta2O5 and indicated a larger tilt angle of the alkyl chains on this substrate by comparison to DTS on SiO2. Furthermore, with use of ellipsometry and XPS, the silane film thickness on Ta2O5 was determined to be substantially smaller than that reported in the literature for DTS on SiO2, supporting the observations of an increased tilt angle (approximately 45 degrees ) on Ta2O5 than on SiO2 (approximately 10 degrees ). By means of cyclic voltammetry, the formation of a dense, essentially pinhole-free, silane film was observed on the cleaned samples. In conclusion, the fully characterized and optimized procedure for the silanization of Ta2O5 surfaces with trichlorosilanes will allow the formation of well-defined, reproducible, and controllable chemical interfaces on Ta2O5.

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“…[10,11]. There, tantalum thin films were completely oxidised at 500 "C within 1 h with a composition close to that of the stoichiometric Taz05.…”

Section: Morphologymentioning

confidence: 99%

“…This is probably the result of diffusion of the reagents along grain boundaries [10,11], and subsequent etching of the underlying material.…”

Section: Etching Characteristicsmentioning

confidence: 99%

Tantalum oxide thin films as protective coatings for sensors

Christensen¹,

Reus²,

Bouwstra³

1999

J. Micromech. Microeng.

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Reactively sputtered tantalum oxide thin-films have been investigated as protective coatkg for aggressive media exposed sensors. Tantalum oxide is shown to be chemically very robust. The etch rate in aqueous potassium hydroxide with pH 11 at 140 "C is lower than 0.008 &h. Etching in liquids with pH values in the range from pH 211 1 have generally given etch rates below 0.04 &h. On the other hand patterning is possible in hydrofluoric acid. Further, the passivation behaviour of amorphous tantalum oxide and polycrystalline Ta20s is different in buffered hydrofluoric acid. By ex-situ annealing in O2 the residual thin-film stress can be altered from compressive to tensile and annealing at 450 "C for 30 minutes gives a stress-free film. The step coverage of the sputter deposited amorphous tantalum oxide is reasonable, but metallisation lines are hard to cover. Sputtered tantalum oxide exhibits high dielectric strength and the pinhole density for 0.5 pm thick films is below 3 cm-2.

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“…R, increased from 3 as-deposited to 110 8, after annealing at 700 "C. These observations agree well with those reported in Refs. [10,11]. There, tantalum thin films were completely oxidised at 500 "C within 1 h with a composition close to that of the stoichiometric Taz05.…”

Section: Morphologymentioning

confidence: 99%

“…In Figure 3 The difference in passivation behaviour of polycrystalline Ta20S and a-TaO was observed after exposing a film to BHF after exsitu annealing at 600 "C. The formed polycrystalline Ta205 film was "lifted" away from the silicon surface within a few hours. This is probably the result of diffusion of the reagents along grain boundaries [10,11], and subsequent etching of the underlying material.…”

Section: Etching Characteristicsmentioning

confidence: 99%

Tantalum oxide thin films as protective coatings for sensors

Christensen

¹

,

Reus

²

,

Bouwstra

³

1999

Technical Digest. IEEE International MEMS 99 Conference. Twelfth IEEE International Conference on Micro Electro Mechanical Syst

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Reactively sputtered tantalum oxide thin-films have been investigated as protective coatkg for aggressive media exposed sensors. Tantalum oxide is shown to be chemically very robust. The etch rate in aqueous potassium hydroxide with pH 11 at 140 "C is lower than 0.008 &h. Etching in liquids with pH values in the range from pH 211 1 have generally given etch rates below 0.04 &h. On the other hand patterning is possible in hydrofluoric acid. Further, the passivation behaviour of amorphous tantalum oxide and polycrystalline Ta20s is different in buffered hydrofluoric acid. By ex-situ annealing in O2 the residual thin-film stress can be altered from compressive to tensile and annealing at 450 "C for 30 minutes gives a stress-free film. The step coverage of the sputter deposited amorphous tantalum oxide is reasonable, but metallisation lines are hard to cover. Sputtered tantalum oxide exhibits high dielectric strength and the pinhole density for 0.5 pm thick films is below 3 cm-2.

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Buffer layers for superconducting YBaCuO thin films on silicon and SiO2

Abstract: By direct deposition onto hot substrates, using laser ablation, crystalline YBa2Cu307_ 6 (123)

Cited by 13 publications

References 38 publications

Formation of Dense Self-assembled Monolayers of (n-Decyl)trichlorosilanes on Ta/Ta₂O₅

Formation of Dense Self-assembled Monolayers of (n-Decyl)trichlorosilanes on Ta/Ta₂O₅

Tantalum oxide thin films as protective coatings for sensors

Tantalum oxide thin films as protective coatings for sensors

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Buffer layers for superconducting YBaCuO thin films on silicon and SiO2

Abstract: By direct deposition onto hot substrates, using laser ablation, crystalline YBa2Cu307_ 6 (123)

Cited by 13 publications

References 38 publications

Formation of Dense Self-assembled Monolayers of (n-Decyl)trichlorosilanes on Ta/Ta2O5

Formation of Dense Self-assembled Monolayers of (n-Decyl)trichlorosilanes on Ta/Ta2O5

Tantalum oxide thin films as protective coatings for sensors

Tantalum oxide thin films as protective coatings for sensors

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Product

Resources

About

Formation of Dense Self-assembled Monolayers of (n-Decyl)trichlorosilanes on Ta/Ta₂O₅

Formation of Dense Self-assembled Monolayers of (n-Decyl)trichlorosilanes on Ta/Ta₂O₅