Dissociative adsorption and site specificity in the initial stages of tetraethoxysilane (TEOS) interaction with Si(111)-(7×7)

Spitzmüller, J.; Braun, J.; Rauscher, Hubert; Behm, R. J.

doi:10.1016/s0039-6028(97)00892-3

Cited by 8 publications

(19 citation statements)

References 21 publications

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“…After exposure to 0.5 L TEOS part of the adatoms appear darkened in the STM images (Fig. 1a) [7]. As shown recently, this darkening is caused by an electronic modification, by a reduced local density of states (LDOS) above the adatoms due to termination of their dangling bonds with adsorbed species [7].…”

Section: Methodssupporting

confidence: 51%

“…The concentration of darker adatoms grows with increasing exposure [7], verifying that these adatoms resulted by reaction with the dissociation fragments of TEOS. Counting the reacted center and corner adatoms reveals a preferential occupation of center adatoms as compared to corner adatoms.…”

Section: Methodsmentioning

confidence: 67%

“…1a) [7]. As shown recently, this darkening is caused by an electronic modification, by a reduced local density of states (LDOS) above the adatoms due to termination of their dangling bonds with adsorbed species [7]. Hence real vacancies, which would be indicative of etch processes, are not induced by TEOS adsorption at room temperature.…”

Section: Methodsmentioning

confidence: 72%

“…The former one is attributed to aliphatic C−H bonds (−CH 2 −) or C−C bonds [9], whereas the latter one can be associated with an ether group (−CH 2 −O−) carbon atom [10]. Based on a detailed analysis of combined STM and XPS measurements after room temperature exposure of Si(111)-(7 × 7) to various TEOS exposures, which has been published recently [7], triethoxysiloxane, diethoxysiloxane and ethyl groups as well as intact TEOS molecules, with triethoxysiloxane and ethyl groups being the majority species, were identified as components of the adsorbate layer [7]. Ethyl groups are adsorbed at rest atoms and corner hole atoms and do not show up in the STM images under these conditions, while triethoxysiloxane groups prefer adatom sites, which appear darkened after adsorption.…”

Section: Methodsmentioning

confidence: 99%

“…For a detailed understanding, however, locally resolved structural information on the distribution of the various decomposition products and their thermal evolution is essential, in particular for the first stages of TEOS decomposition, since the structure of the interface between the silicon substrate and the growing oxide is likely to critically influence the further growth and hence the properties of the final oxide. First scanning tunneling microscopy (STM) and XPS results on the adsorption process of TEOS on Si(111)-(7 × 7) at room temperature have been published recently [7]. In that study it was found that TEOS dissociates mainly into triethoxysiloxane and ethyl groups in a highly site selective reaction, with the former species adsorbing on adatoms and the latter on rest atoms/corner hole atoms.…”

Section: Introductionmentioning

confidence: 99%

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Thermal decomposition of tetraethoxysilane (TEOS) on Si(111)-(7×7)

Spitzmüller¹,

Braun²,

Rauscher³

et al. 1998

Applied Physics A: Materials Science & Processing

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We report results of a combined scanning tunneling microscopy and X-ray photoelectron spectroscopy study on the thermal decomposition of tetraethoxysilane (TEOS), a precursor for SiO 2 formation by chemical vapor deposition, on Si(111)-(7 × 7). Annealing after predominantly dissociative adsorption at room temperature, where triethoxysiloxane and ethyl groups are the main adsorbate species, leads to further decomposition with various products evolving, including diethoxysiloxane and further ethyl groups. This goes along with structural changes on the (7 × 7) reconstructed surface. A characteristic new structural element, with a maximum on interstitial sites, is interpreted as the very beginning of surface oxide formation.Over the last few years chemical vapor deposition (CVD) of SiO 2 has emerged as an attractive alternative for producing ultrathin dielectric layers on silicon at relatively low temperatures. One of the most frequently used precursors for this purpose is tetraethoxysilane (TEOS) [1-3]. Because of the complexity of the processes involved in oxide formation via TEOS CVD a microscopic understanding of these steps is essential for a quality improvement of the resulting insulating layers. First studies aiming at the microscopic understanding of TEOS decomposition and oxide growth involving high resolution electron energy loss spectroscopy (HREELS) [4,5], thermal desorption spectroscopy (TDS) [4,5], and X-ray photoelectron spectroscopy (XPS) [5,6], yielded information on the dissociation mechanisms and the oxide composition on Si(100)-(2 × 1). For a detailed understanding, however, locally resolved structural information on the distribution of the various decomposition products and their thermal evolution is essential, in particular for the first stages of TEOS decomposition, since the structure of the interface between the silicon substrate and the growing oxide is likely to critically influence the growth and hence the properties of the final oxide. First scanning tunneling microscopy (STM) and XPS results on the adsorption process of TEOS on Si(111)-(7 × 7) at room temperature have been published recently [7]. In that study it was found that TEOS dissociates mainly into triethoxysiloxane and ethyl groups in a highly site selective reaction, with the former species adsorbing on adatoms and the latter on rest atoms/corner hole atoms. In this work we focus on the thermal decomposition of these adsorbates upon annealing. We will concentrate on microscopic structural changes induced and on the Si(111)-(7 × 7) substrate surface. To this end we mainly evaluate STM topography images obtained after TEOS exposure and various annealing steps, supplemented by XPS results. We will restrict ourselves to the more clear case of rather low TEOS coverages, resulting from exposures of less than or equal 1 L. ExperimentalThe STM and XPS experiments were performed in two different ultra-high vacuum (UHV) systems, equipped with a pocket-size STM and a Fisons CLAM 2 XPS system, respectively, and standard equipment for surfa...

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Section: Methodssupporting

confidence: 51%

Section: Methodsmentioning

confidence: 67%

Section: Methodsmentioning

confidence: 72%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Thermal decomposition of tetraethoxysilane (TEOS) on Si(111)-(7×7)

Spitzmüller¹,

Braun²,

Rauscher³

et al. 1998

Applied Physics A: Materials Science & Processing

Self Cite

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Rapid and alternative fabrication method for microfluidic paper based analytical devices

Malekghasemi

Kahveci

Duman

2016

Talanta

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A major application of microfluidic paper-based analytical devices (µPADs) includes the field of point-of-care (POC) diagnostics. It is important for POC diagnostics to possess properties such as ease-of-use and low cost. However, µPADs need multiple instruments and fabrication steps. In this study, two different chemicals (Hexamethyldisilazane and Tetra-ethylorthosilicate) were used, and three different methods (heating, plasma treatment, and microwave irradiation) were compared to develop µPADs. Additionally, an inkjet-printing technique was used for generating a hydrophilic channel and printing certain chemical agents on different regions of a modified filter paper. A rapid and effective fabrication method to develop µPADs within 10min was introduced using an inkjet-printing technique in conjunction with a microwave irradiation method. Environmental scanning electron microscope (ESEM) and x-ray photoelectron spectroscopy (XPS) were used for morphology characterization and determining the surface chemical compositions of the modified filter paper, respectively. Contact angle measurements were used to fulfill the hydrophobicity of the treated filter paper. The highest contact angle value (141°±1) was obtained using the microwave irradiation method over a period of 7min, when the filter paper was modified by TEOS. Furthermore, by using this method, the XPS results of TEOS-modified filter paper revealed Si2p (23%) and Si-O bounds (81.55%) indicating the presence of Si-O-Si bridges and Si(OEt) groups, respectively. The ESEM results revealed changes in the porous structures of the papers and decreases in the pore sizes. Washburn assay measurements tested the efficiency of the generated hydrophilic channels in which similar water penetration rates were observed in the TEOS-modified filter paper and unmodified (plain) filter paper. The validation of the developed µPADs was performed by utilizing the rapid urease test as a model test system. The detection limit of the developed µPADs was measured as 1unitml(-1) urease enzyme in detection zones within a period of 3min. The study findings suggested that a combination of microwave irradiation with inkjet-printing technique could improve the fabrication method of µPADs, enabling faster production of µPADs that are easy to use and cost-effective with long shelf lives.

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The interaction of silanes with silicon single crystal surfaces: microscopic processes and structures

Rauscher

2001

Surface Science Reports

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Dissociative adsorption and site specificity in the initial stages of tetraethoxysilane (TEOS) interaction with Si(111)-(7×7)

Cited by 8 publications

References 21 publications

Thermal decomposition of tetraethoxysilane (TEOS) on Si(111)-(7×7)

Thermal decomposition of tetraethoxysilane (TEOS) on Si(111)-(7×7)

Rapid and alternative fabrication method for microfluidic paper based analytical devices

The interaction of silanes with silicon single crystal surfaces: microscopic processes and structures

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