The adsorption and reaction of tetrakis(dimethylamido)hafnium (TDMAH) on hydrogen terminated Si(100) were studied by using in situ attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), transmission IR, and quadrupole mass spectrometry (Q-MS). Surface and gas phase reactions were investigated at temperatures between 25 and 300 °C. Density functional theory (DFT) calculations benchmarked by coupled cluster calculations on small models were performed for gas phase decomposition via intramolecular insertion and β-hydride elimination as well as the adsorption and reaction of TDMAH onto a hydrogen terminated Si(100) surface. N−Si and CH2−Si bonds due to reactions on the Si windows were observed in transmission IR, while N−Ge and CH2−Ge bonds on a Ge internal reflectance element (IRE) were observed by ATR-FTIR at 25 and 100 °C. Also observed were the formation of Hf−H bonds and three-member-ring species on the Si surface; the former was confirmed by a control D2O exchange reaction experiment. Both transmission IR and Q-MS indicated the presence of decomposition products dimethylamine (DMA) and N-methyl methyleneimine (MMI). The calculated bond dissociation energies (BDE) at the CCSD(T)/CBS level roughly follow the order of Hf−O > Hf−N > N−H, C−H, Si−N > Si−H, Si−C > N−C, Hf−H > Hf−Si, and the BDEs of the same chemical bond can vary substantially in different molecules. The interface is predicted by DFT calculations to involve Hf−Si, Hf−N−Si, and/or HfNC-Si bonds. TDMAH decomposition products, such as MMI, can form a C−Si or N−Si bond with the silicon surface. The combined experimental and theoretical results suggest that insertion and β-hydride elimination reactions can occur during bidentate chemisorption on the H−Si(100) surface by forming N−Si bonds.

Using narrow nuclear reaction resonance profiling, aluminum profiles are obtained in ϳ3.5 nm Al 2 O 3 films deposited by low temperature ͑Ͻ400°C͒ chemical vapor deposition on Si͑100͒. Narrow nuclear resonance and Auger depth profiles show similar Al profiles for thicker ͑ϳ18 nm͒ films. The Al profile obtained on the thin film is consistent with a thin aluminum silicate layer, consisting of Al-O-Si bond units, between the silicon and Al 2 O 3 layer. Transmission electron microscopy shows evidence for a two-layer structure in Si/Al 2 O 3 /Al stacks, and x-ray photoelectron spectroscopy shows a peak in the Si 2p region near 102 eV, consistent with Al-O-Si units. The silicate layer is speculated to result from reactions between silicon and hydroxyl groups formed on the surface during oxidation of the adsorbed precursor.

Magnetoelectric heterostructures are being actively investigated for utilization in next generation microwave devices such as tunable filters and phase shifters. For efficient microwave absorption and magnetoelectric coupling, relatively thick (>1 mm) epitaxial spinel ferrite films with smooth topographies are required for the magnetic/ferroelectric heterostructures. Towards this goal, direct liquid injection (DLI)-CVD has been utilized for epitaxial growth of nickel ferrite (NiFe 2 O 4 ) films on MgAl 2 O 4 (100) and MgO (100) substrates with high deposition rates. Anhydrous Ni(acac) 2 and Fe(acac) 3 (acac ¼ acetylacetonate) are used as precursor sources dissolved in N,N-dimethyl formamide for the DLI vaporizer system. The influence of deposition temperature on the film properties has been investigated using optimized process conditions for flow of the injected precursors and oxygen. Epitaxial nickel ferrite films of stoichiometric composition are obtained in the temperature range 500-800 8C on both substrates with growth rates in the range 0.6-1.1 mm h À1. Because of changes in the surface diffusion behavior, the film morphology is found to be dependent on the deposition temperature with atomically smooth films being obtained for deposition in the temperature range 600-700 8C. Magnetic measurements reveal an increase in the saturation magnetization for the films with increasing growth temperature, which correlates well with the trend for improved epitaxial growth as indicated by X-ray and Raman spectroscopy measurements. Nickel ferrite films deposited on MgAl 2 O 4 (100) at 800 8C exhibit saturation magnetization very close to the bulk value of 300 emu cm À3.

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Magnetoelectric interactions as a function of applied electric field have been studied in ferrite-ferroelectric heterostructures at microwave frequencies. The measurements are performed on 1.5–2.0 μm thick nickel ferrite (NiFe2O4) films grown heteroepitaxially on lead zinc niobate-lead titanate and lead magnesium niobate-lead titanate substrates using direct liquid injection chemical vapor deposition. Large shifts in the ferromagnetic resonance profile are observed in these heterostructures due to strong magnetoelectric coupling resulting from electrostatic field induced changes in the magnetic anisotropy field. Theoretical estimates of field shifts are in good agreement with the experimental data.