We present grazing-incidence Fourier transform infrared and AFM data of Au, Al, and Ti vapor-deposited onto self-assembled monolayers (SAMs) of conjugated mono- and dithiols. SAMs of 4,4'''-dimercapto-p-quaterphenyl, 4,4"-dimercapto-p-terphenyl, and 4,4'-dimercapto-p-biphenyl have reactive thiols at the SAM/vacuum interface that interact with vapor-deposited Au or Al atoms, preventing metal penetration. Conjugated monothiols lack such metal blocking groups, and metals (Au, Al) can penetrate into their SAMs. Vapor deposition of Ti onto conjugated mono- and dithiol SAMs and onto hexadecanethiol SAMs destroys the monolayers.

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We present an in situ infrared spectroscopic study of the interface formation during atomic layer deposition of alternative high-permittivity (high-κ) gate dielectrics. Layer-by-layer oxide growth may be achieved by alternating pulses of a molecular metal precursor (e.g., trimethylaluminum for aluminum oxide growth) and water vapor. Contrary to common belief, we find that the metal precursor, not the oxidizing agent, is the key factor to control Al2O3 nucleation on hydrogen-terminated silicon. Metal surface species catalyze subsurface Si oxidation. These findings have direct implications on growth conditions to optimize semiconductor-dielectric interfaces.

Articles you may be interested inIn 0.53 Ga 0.47 As n -metal-oxide-semiconductor field effect transistors with atomic layer deposited Al 2 O 3 , HfO 2 , and LaAlO 3 gate dielectrics Electrical properties of 0.5 nm thick Hf-silicate toplayer ∕ HfO 2 gate dielectrics by atomic layer deposition Appl. Phys. Lett. 86, 222904 (2005); 10.1063/1.1941455 Effect of NH 3 surface nitridation temperature on mobility of ultrathin atomic layer deposited HfO 2

Epitaxial growth of SrTiO₃ on silicon by molecular beam epitaxy has opened up the route to the integration of functional complex oxides on a silicon platform. Chief among them is ferroelectric functionality using perovskite oxides such as BaTiO₃. However, it has remained a challenge to achieve ferroelectricity in epitaxial BaTiO₃ films with a polarization pointing perpendicular to the silicon substrate without a conducting bottom electrode. Here, we demonstrate ferroelectricity in such stacks. Synchrotron X-ray diffraction and high-resolution scanning transmission electron microscopy reveal the presence of crystalline domains with the long axis of the tetragonal structure oriented perpendicular to the substrate. Using piezoforce microscopy, polar domains can be written and read and are reversibly switched with a phase change of 180°. Open, saturated hysteresis loops are recorded. Thus, ferroelectric switching of 8- to 40-nm-thick BaTiO₃ films in metal-ferroelectric-semiconductor structures is realized, and field-effect devices using this epitaxial oxide stack can be envisaged.

The paper reviews our recent progress and current challenges in implementing advanced gate stacks composed of high-j dielectric materials and metal gates in mainstream Si CMOS technology. In particular, we address stacks of doped polySi gate electrodes on ultrathin layers of high-j dielectrics, dual-workfunction metal-gate technology, and fully silicided gates. Materials and device characterization, processing, and integration issues are discussed.

To identify the nature and the local structure of the surface of supported catalyst nanoparticles, we have performed a detailed comparative study of CO adsorption on two categories of oxide-supported Palladium catalysts:  (1) polycrystalline MgO and γ-Al2O3 supported Pd metal catalysts prepared by impregnation techniques and characterized by different degrees of regularity and perfection and (2) single-crystal based Pd model catalysts prepared under ultrahigh vacuum (UHV) conditions. The assignment of the CO vibrational frequencies to different types of sites on these systems has allowed a detailed structural characterization. For the Pd model catalyst, at low CO coverage, the infrared (IR) reflection absorption spectra closely resemble the expected behavior for terminations by a majority of (111) facets and a minority of (100) facets. The spectral features are indicative of defect sites such as particle steps and edges. Occupation of the defect sites can be affected by surface contaminations such as atomic carbon. Thus the CO spectra at high coverage can be used as both a structural and chemical probe under reaction conditions, provided that complementary information on the particle morphology is available. For the MgO and γ-Al2O3 supported Pd systems, two distinct narrow bands (ν ≅ 2070 and ≅ 1970 cm-1) have been assigned to linearly bonded and bridge-bonded CO species, on Pd (100)/(111) edges or facets, in agreement with the previous results obtained on model catalysts. The broad character of the 2070 cm-1 feature indicates the simultaneous presence of (100) and (111) faces, with edge and corner sites present at their intersection. The high intensity and the small half-width (fwhm) of the band at 1970 cm-1 on a Pd/MgO sample treated at high temperature, assigned to bridge-bonded CO species, suggests that the metal particles expose faces with a high level of regularity. Further spectroscopic features (ν ≅ 1920−1800 cm-1), are ascribed to the presence of different types of 3-fold hollow sites on (111) faces.

We establish the limits of magnetism in thin, electronic grade, hafnium oxide, and hafnium silicate films deposited onto silicon wafers by chemical vapor deposition and atomic layer deposition. To the limits of sensitivity of our measurement techniques, no ferromagnetism occurs in these samples. Contamination by handling with stainless-steel tweezers leads to a measurable magnetic signal. The magnetic properties of this contamination are similar to those attributed to ferromagnetic HfO2 in a recent report, including the magnitude of moment, magnetization field dependence, and spatial asymmetry.