High-resolution x-ray photoelectron spectroscopy (XPS) was applied to characterize the electronic structures for a series of high-k materials (HfO2)x(Al2O3)1−x grown on (100) Si substrate with different HfO2 mole fraction x. Al 2p, Hf 4f, O 1s core levels spectra, valence band spectra, and O 1s energy loss all show continuous changes with x in (HfO2)x(Al2O3)1−x. These data are used to estimate the energy gap (Eg) for (HfO2)x(Al2O3)1−x, the valence band offset (ΔEν) and the conduction band offset (ΔEc) between (HfO2)x(Al2O3)1−x and the (100) Si substrate. Our XPS results demonstrate that the values of Eg, ΔEν, and ΔEc for (HfO2)x(Al2O3)1−x change linearly with x.

In this paper, Fourier transform infrared (FT-IR) spectroscopy is used to study the thermal properties of methyl silsesquioxane (MSQ), an important low-dielectric-constant organic spin-on glass for semiconductor device fabrication. The compositional and structural changes of MSQ with temperature are investigated in detail. The cross-linking process, where the three-dimensional networked structure is formed, is found to start at room temperature, and is almost complete at the typical baking temperature of 250 °C. Further cross-linking occurs during the curing process at 425 °C, and small short-chain clusters can also be driven away at this temperature by sublimation. In this study, we have assigned all the MSQ IR peaks and we have used the long-chain O–Si–O IR peak to calculate the “degree of cross-linking” quantitatively.

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BiVO has been identified as one of the excellent visible light responsive photoanodes for use in photoelectrochemical (PEC) water splitting. However, pristine BiVO usually exhibits relative low photocatalytic properties owing to insufficient charge separation and transport characteristics. Although the marginal n-type doping of higher valence ions can obviously raise the photocurrent value, it by no means improves the PEC stability. In this work, we successfully enhanced the PEC stability of BiVO by doping Fe ions in substitution of Bi. Density functional theory calculations have illustrated that Fe-doping would result in an impurity band in the forbidden gap, and thus narrow its energy gap. More importantly, Fe-doping can synergize with other means to further improve the PEC activities of BiVO . Therefore, we fabricated a nanoporous Fe/W co-doped BiVO photoelectrode, and then loaded the metal-organic framework (MOF) MIL-100(Fe) as cocatalyst to further promote the separation of charge carriers. To the best of our knowledge, MOFs have not yet been utilized as a cocatalyst to facilitate the charge separation, which could increase the photocurrent density of Fe/W co-doped BiVO .

The kinetics of the interfacial layer (IL) growth between Hf aluminates and the Si substrate during high-temperature rapid thermal annealing (RTA) in either N2 (∼10 Torr) or high vacuum (∼2×10−5 Torr) is studied by high-resolution x-ray photoelectron spectroscopy and cross-sectional transmission electron microscopy. The significant difference of the IL growth observed between high vacuum and relatively oxygen-rich N2 annealing (both at 1000 °C) is shown to be caused by the oxygen species from the annealing ambient. Our results also show that Hf aluminates exhibit much stronger resistance to oxygen diffusion than pure HfO2 during RTA in N2 ambient, and the resistance becomes stronger with more Al incorporated into HfO2. This observation is explained by the combined effects of (i) smaller oxygen diffusion coefficient of Al2O3 than HfO2, and (ii) higher crystallization temperature of the Hf aluminates.

Fourier transform infrared spectroscopy (FT-IR) was used to study the cure reaction process of an ester-type photosensitive polyimide, PMDA/ODA films coated on silicon wafer substrates. In the in situ high-temperature FT-IR study carried out in vacuum, all the characteristic peaks of imide and the crosslinkable group were observed to decrease gradually with an increase in temperature. The completion of the imidization reaction is at ∼270 °C. Our result shows that the ester-type photosensitive polyimide can be cured at a much lower temperature than previously reported. The imide peak δas(C, C > NC) at 588 cm−1 was used to follow the imidization process, and the result agrees well with that obtained by using another imide peak v(C–N–C) at 1378 cm−1. The film shrinks by one third during the cure process, and the temperature dependence of the film thickness shows excellent agreement with the “imidization degree”.