The negative phonon confinement effect in nanoscopic sodium nitrite

Atomic layer deposition is a promising technique to deposit conformal, nm-thin metal barriers in high aspect ratio trenches. However, exactly because of its excellent conformality, the deposition can also occur inside the nanopores of the most advanced low-k materials. In this work, the mechanisms of atomic layer deposition on and in low-k, porous dielectric films were studied, using HfO 2 as a test material. Exhaustive analyses showed firstly that the HfCl 4 precursor penetrated uniformly in the pores throughout a 44 nm low-k film. Secondly it is shown that the pores were sealed as function of precursor size, i.e. there are conditions where the pores became inaccessible for HfCl 4 , while the -smaller -H 2 O molecules could still penetrate the pores. From these analyses a deposition model was proposed.

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Properties of BaTiO3 confined in nanoporous Vycor and artificial opal silica

Vaněk

Petzelt

Bovtun

et al. 2010

PAC

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Using the sol-gel technique, BaTiO3 was embedded into nanoporous Vycor and artificial vitreous opal silica for the first time. About 50 vol% of the pores was filled. In case of the Vycor glass (pore diameter 4-6 nm) only amorphous phase was revealed by XRD, IR reflectivity and Raman spectra. After additional gradual annealing, no crystallization was achieved. Chemical reaction with the SiO2 skeleton started at ~1000 K. The room-temperature IR and Raman spectra clearly show characteristic vibrational modes of the ferroelectrically distorted TiO6 octahedra without any long-range order. In case of the opal matrix (densely packed silica spheres, pore diameter up to ~50 nm), crystallization of the ferroelectric BaTiO3 appeared in coexistence with the amorphous phase, but the penetration depth of the crystalline BaTiO3 was limited. From the apparent temperature independence of the effective wide-frequency dielectric response due to the essentially temperature independent effective soft mode stiffened to ~100 cm-1, we can deduce that no macroscopic percolation of the crystalline BaTiO3 has appeared in our opal matrix. Nevertheless, Raman spectra bring evidence of a diffuse ferroelectric phase transition in the opal-BaTiO3 composite.

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The negative phonon confinement effect in nanoscopic sodium nitrite

Cited by 3 publications

References 40 publications

Size Effect in Mechanical Properties of Nanostructured Coatings

Size Effect in Mechanical Properties of Nanostructured Coatings

Fundamental study of atomic layer deposition in and on porous low-k films

Properties of BaTiO3 confined in nanoporous Vycor and artificial opal silica

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