Due to its chemical specificity, the near edge X-ray absorption fine structure spectroscopy is an interesting technique to study the changes in hybrid organic-inorganic photoresists. In this work, we analyzed the chemical changes occurring in photoresists synthesized from organically modified precursors and transition metal alkoxides by sol-gel route. These systems are nonchemically amplified resists for ultraviolet, extreme ultraviolet, and electron beam lithography. They are based on Si, Zr, and Ti oxides or a combination of these. The experiments were conducted at the PolLux beamline of the Swiss Light Source, by a scanning transmission X-ray microscopy, which combines the spatially-resolved microscopy and fine structure spectroscopy at once. The absorption spectra were collected in the energy range of the carbon edge (≈ 290 eV) before and after in situ exposure of the photoresists to 500 eV photons. The variations in peak intensity after exposure reveal the changes in the chemical environment of carbon and the chemical configuration of the organic ligands, regardless of the inorganic part. It was found that the photon exposure induced sizable photodegradation or photopolymerization of organic groups (phenyl or methyl methacrylate, respectively). These mechanisms contribute to the foundation for the exposure reaction in negative-tone hybrid photoresists. Interestingly, it was also found that the detachment of the phenyl ligand occurs in a variety of possible pathways to condensation. We believe that our results and approach can provide a better understanding of photochemistry of resists, in particular for extreme ultraviolet lithography.
Nanoporous TiO2 anatase film has been investigated as sensitive layer in Surface Plasmon Resonance sensors for the
detection of hydrogen and Volatile Organic Compounds, specifically methanol and isopropanol. The sensors consist of a
TiO2 nanoporous matrix deposited above a metallic plasmonic grating, which can support propagating Surface Plasmon
Polaritons. The spectral position of the plasmonic resonance dip in the reflectance spectra was monitored and correlated
to the interaction with the target gases.
Reversible blue-shifts of the resonance frequency, up to more than 2 THz, were recorded in response to the exposure to
10000 ppm of H2 in N2 at 300°C. This shift cannot be explained by the mere refractive index variation due to the target
gas filling the pores, that is negligible.
Reversible red-shifts were instead recorded in response to the exposure to 3000 ppm of methanol or isopropanol at room
temperature, of magnitudes up to 14 THz and 9 THz, respectively. In contrast, if the only sensing mechanism was the
mere pores filling, the shifts should have been larger during the isopropanol detection.
We therefore suggest that other mechanisms intervene in the analyte/matrix interaction, capable to produce an injection
of electrons into the sensitive matrix, which in turn induces a decrease of the refractive index.
In this work, three TiO2 thin films with thicknesses of 22.7, 48.5 and 102.9 nm were grown on Si (100) substrates by the technique of electron beam evaporation. The films were deposited at a substrate temperature of 150°C with a deposition rate of 0.3 - 0.5 A/sec. The films thicknesses were characterized by spectroscopic ellipsometry and profilometry. The surface roughness was measured by AFM obtaining RMS of less than 0.7nm. Investigations performed by XPS method have shown that stoichiometric TiO2 was obtained on all the samples with no suboxide presences. Reflectance measurements of the samples were performed in EUV and SX spectral regions from 25.5 to 454.2eV using synchrotron radiation. Analyzing the refractive index N=n+ik of TiO2 thin films, optical constants (n,k) in this energy range were both determined by fitting the Fresnel equations with least-square fitting methods.
Engineered organic-inorganic hybrid materials, HyMat, offer new opportunities for the easy, fast and cheap development
of miniaturized functional devices. The integration of inorganic oxide networks, organic functional groups and optically
active molecules or nanoparticles allows to obtain combinations of properties and structures otherwise impossible with
traditional materials.
In particular, a simple and highly versatile synthesis platform enabling preparation of HyMat is presented, which is built
up by a bottom-up sol-gel approach at low processing temperatures. A few types of key building blocks pave the way for
accessing HyMat and make up their formulation, providing a means to synthesize innovative materials enabling to get:
- optically active micro and nanostructures;
- miniaturized sensors for analytes in gaseous or liquid media;
- direct patternability with a range of lithographic techniques;
- variable inorganic and organic compositions, and controlled porosity.
Examples of micro and nanostructures based on these spin-on materials with ceramic (i.e. SiO2, GeO2, Al2O3, ZrO2,
TiO2,) and hybrid compositions will be presented for different applications including plasmonic or fluorescent sensors,
dry-etching masks with outstanding resistance, optically active micro and nanostructured platforms and high resolution
patterns.
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