Infrared study of surface species arising from ammonia adsorption on oxide surfaces

Цыганенко, А. А.; Pozdnyakov, Dmitriy; Филимонов, В. Н.

doi:10.1016/0022-2860(75)85038-1

Cited by 255 publications

(125 citation statements)

References 29 publications

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“…Although NH 3 is thermodynamically unstable at 1100°C, its homogeneous gas-phase decomposition to N 2 and H 2 is kinetically very slow so that most of NH 3 remains intact and can adsorb on the surface. 39 At high temperatures (Ͼ300°C), NH 3 adsorbs dissociatively on sapphire surface according to: 40,41 NH 3 ⇔NH x(a) ϩ͑3Ϫx ͒H (a) . ͑3͒…”

Section: Proposed Nitridation Mechanismmentioning

confidence: 99%

X-ray photoelectron spectroscopic study on sapphire nitridation for GaN growth by hydride vapor phase epitaxy: Nitridation mechanism

Dwikusuma

Kuech

2003

Journal of Applied Physics

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The nitridation of c-plane sapphire within the hydride vapor phase epitaxy system was systematically studied as a function of time and ammonia partial pressure using ex situ x-ray photoelectron spectroscopy, reflection high-energy electron diffraction, and atomic force microscopy. During the nitridation process, nitrogen was incorporated into the sapphire surface. There were two different nitrogen chemical bonding states, which can be attributed to N-Al bonds and nitrogen in oxygen-rich environment ͑'N-O'͒. As the nitridation continued, the N 1s intensity increased while the O 1s intensity decreased indicating the growth of a nitrogen-rich layer. The sapphire nitridation process can be modeled as a diffusion couple of AlN and Al 2 O 3 , where N 3Ϫ and O 2Ϫ interdiffuse in the rigid Al 3ϩ framework. Nitrogen diffuses into sapphire and substitutes for oxygen to bond with aluminum. The bond substitution is accompanied by structural changes where the AlN in-plane direction is rotated 30°with respect to the sapphire direction. The replaced oxygen diffuses out to the surface, combines with hydrogen and desorbs as H 2 O. The overall nitridation rate is determined by the slower of the two moving anions. From the x-ray photoelectron spectroscopy data, the chemical diffusion coefficient of nitrogen (D N ) and oxygen (D O ), were estimated. D N was found to be higher than D O , which suggested that the overall nitridation rate was controlled by the diffusion of oxygen to the surface. After nitridation, no protrusions were observed on the surface and no significant changes in the surface roughness were measured when compared to the as-received sapphire.

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Section: Proposed Nitridation Mechanismmentioning

confidence: 99%

X-ray photoelectron spectroscopic study on sapphire nitridation for GaN growth by hydride vapor phase epitaxy: Nitridation mechanism

Dwikusuma

Kuech

2003

Journal of Applied Physics

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“…1963, Pimentel et al 1962. The band around 3410 cm -~ in the IR spectra of the samples without NH3 seems to indicate that a shift occurs due to a perturbation in the-OH stretching vibration owing to an interaction between the NH3 molecule and the structural -OH of the substrate (Tsyganenko et al 1975). Finally, the P-NH symmetric stretching vibration around 3440 cm -I (Peri 1971), could also contribute to the intensity of the above mentioned band.…”

Section: Ir Spectramentioning

confidence: 95%

Acidity Of Montmorillonite-(Ce or Zr) Phosphate Cross-Linked Compounds

Rey-Bueno

Garcı́a-Rodrı́guez

Mata-Arjona

et al. 1995

Clays and clay miner.

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Abstract--The nature and number of acid sites per unit weight on a series of materials obtained by interaction of a montmorillonite with zirconium or cerium hydrogenphosphates precipitated in situ by reaction between their precursors have been investigated.The quantitative determination of the surface acidity has been carried out by three different methods: titration with triethanolamine in aqueous media; TG analysis of the samples after n-butylamine treatment and vacuum desorption; and chemisorption of NH3 at 239.8 K. Additional information about the nature of the surface acid sites has been obtained from the IR spectra of the samples with bases adsorbed.Results show that the acid site density on the montmorillonite-cerium or zirconium phosphate crosslinked compounds is greater than on the parent montmorillonite and increases as the content in tetravalent metal phosphate rises throughout the different series. Also the number of acid sites for the cerium phosphate-montmorillonite materials is lower than for zirconium ones and the characteristics obtained depend on the bases used for their evaluation.The presence of two IR adsorption bands at 1400 and 3145 cm -1, assigned to the NH4 + ion, and the absence of the 1170-1361 cm-l bands, characteristic of the NH3 adsorbed on a Lewis site, strongly suggest the Brrnsted character of the acidity of these compounds.

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“…Microcalorimetric adsorption of NH 3 and CO 2 showed that the surface acidity and basicity of the mixed oxides after calcination at 673 K are similar despite the different Mg/Fe ratios. Increasing calcination temperature from 673 to 773 K significantly decreased the surface area of the 3 Mg/Fe oxide, but the densities of both the acid and base sites were not changed.…”

mentioning

confidence: 94%

“…Infrared spectroscopy is an effective technique used for identifying the nature of acid and base sites when probe molecules such as ammonia and carbon dioxide are adsorbed (2,3). There are several methods employed in the determination of strength and number of acid/base sites (4).…”

Section: Introductionmentioning

confidence: 99%

Microcalorimetric Studies of Surface Acid/Base Properties of Magnesium Iron Catalysts Prepared from Hydrotalcite-Type Precursors

Shen

Chen

1997

Journal of Solid State Chemistry

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Infrared study of surface species arising from ammonia adsorption on oxide surfaces

Cited by 255 publications

References 29 publications

X-ray photoelectron spectroscopic study on sapphire nitridation for GaN growth by hydride vapor phase epitaxy: Nitridation mechanism

X-ray photoelectron spectroscopic study on sapphire nitridation for GaN growth by hydride vapor phase epitaxy: Nitridation mechanism

Acidity Of Montmorillonite-(Ce or Zr) Phosphate Cross-Linked Compounds

Microcalorimetric Studies of Surface Acid/Base Properties of Magnesium Iron Catalysts Prepared from Hydrotalcite-Type Precursors

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