M.A.C. Devillers

Electric field induced second harmonic generation spectroscopy on a metal‐oxide‐silicon structure

Spectroscopic electric‐field‐induced second harmonic generation on a Si(111)–SiO2–Cr metal‐oxide‐silicon structure shows a bias‐independent ‘‘interface’’ resonance at 3.25 eV and a ‘‘bulk’’ resonance at 3.43 eV which is strongly bias dependent. The symmetry forbidden bulk dipole contribution becomes observable, and even dominating, due to the bias‐induced band‐bending that breaks the bulk inversion symmetry. The origin of these resonances is discussed, as well as the prospects for using second harmonic generation as a probe of metal‐oxide‐silicon characteristics.

Nonlinear magneto-optical Kerr effect in hyper-Rayleigh scattering from layer-by-layer assembled films of yttrium iron garnet nanoparticles

Magnetization-induced second-harmonic generation (SHG) in layer-by-layer assembled films containing yttrium iron garnet nanoparticles is observed. The SHG intensity, including its magnetoinduced component, linearly increases with the number of self-assembling layers, which indicates along with diffuseness of the SHG radiation that SHG occurs in its incoherent form: hyper-Rayleigh scattering (HRS). The nonlinear magneto-optical Kerr effect in HRS has a noticeable magnetic contrast brought about by the internal homodyne mechanism.

Damage after annealing and aging at room temperature of platinized silicon substrates

Platinum films to be used as a substrate and as a bottom electrode for the growth of ferroelectric materials should be able to withstand the thermal budget specific to the deposition method of the ferroelectric layer without being degraded. Annealing of platinized Si wafers in nitrogen and nitrogen:oxygen ambient conditions was performed in a similar fashion as prior to metalorganic chemical vapor deposition of ferroelectric thin films. The consequent induced modifications of the initial morphology, composition, and structure of the Pt wafers were studied, respectively, by atomic force microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction. The observations were related to the optical properties of the annealed Pt wafer by creating a model fitting ellipsometry data. Using this technique, the roughening at room temperature of a platinized wafer was monitored for 15 months starting shortly after the wafer was being processed. These results indicate that the Pt wafers are also aging at room temperature.

Optical second harmonic generation studies of thin ferroelectric ceramic films

Abstract The microscopic structure of thin PZT films with various Pb concentrations is studied by optical second-harmonic generation. From the azimuthal anisotropic dependence and scattering indicatrices of the nonlinear optical response information about the orientation distribution of microcrystallites is obtained.

Optical second-harmonic generation studies of thin lead-zirconate-titanate ferroelectric films

Abstract Optical second-harmonic generation was used to study the microscopic structure of thin PZT films for various Pb concentrations. From the polarization and angular dependence of the nonlinear response, information about the distribution of microcrystallites can be obtained.

Mocvd growth and characterization of PbTiO3 thin films on Pt/Ti/SiO2/Si substrates

Abstract PbTiO3 thin films were grown by Metalorganic Chemical Vapor Deposition (MOCVD) on 6′′ platinized Si wafers. In a first stage of investigation, the quality of the platinum surface was correlated with the substrate temperature and the composition of the atmosphere of the warming-up procedure in the reactor. The Pt reflectivity and the surface roughness were clearly modified by higher temperatures and by oxygen environments, though no clear diffusion mechanisms could be observed with Auger. In a second stage of investigation, the growth of PbTiO3 was studied. Using a standard PbTiO3 growth procedure, we studied the influence of substrate temperature and gas phase composition. Below 650°C, PbO appears as the main phase; at 650°C, PbTiO3 and PbO coexist; and at 700°C, only PbTiO3 is detected. The morphologies were examined by SEM / AFM and the roughness at the interface was studied by ellipsometry.

Oxide-thickness dependence of second harmonic generation from thick thermal oxides on Si(111)

We show here that the oxide-thickness dependence of the s-polarized SHG from Si(111) covered with a thick thermal oxide is completely described by multiple reflections in the oxide film. For the p-polarized response, a strong enhancement with thickness is observed, which cannot be explained in this way. These measurements show that one should be cautious in analyzing the SHG from a buried interface, and carefully take into account the linear optics involved.

Interfacial layer observed by ellipsometry in MOCVD grown Pb(Zr, Ti)O-3 thin films

Abstract Polycrystalline Pb(Zr, Ti)O3 thin films have been grown by Metalorganic Chemical Vapor Deposition (MOCVD) technique. The characterization of 200 nm thick polycrystalline Pb(Zr, Ti)O3 thin films on 6 inch diameter Pt/Ti/SiO2/Si substrates is reported. XRD reveals good crystalline structure with respect to powder standards. Ellipsometry indicates an interface layer due to substrate roughness induced by the heating-up procedure prior to growth. Ellipsometry is a good tool to evaluate the quality of the grown thin films and the thickness of this observed interfacial layer.

MOCVD PbZrxTi1 - xO3 thin films on platinized silicon wafers and SrTiO3 crystals: growth and optical properties

Abstract PbZrxTi1-xO3 (PZT) thin films were grown on 6” platinized silicon substrates (Pt / Si) and SrTiO3 (STO) crystals by Metal-Organic Chemical Vapor Deposition (MOCVD) as a function of the Zr / (Zr+Ti) ratio in the gas phase. Morphology, optical properties, and crystal structure were investigated by scanning electron microscopy, atomic force microscopy, ellipsometry, and X-ray diffraction. The morphology, structure, and optical properties of the polycrystalline and epitaxial films were compared. The determination of the refractive index by ellipsometry (from 550 nm to 2000 nm) was not sensible for the films grown on (Pt / Si) but successful for the films grown on SrTiO3.

Probing the silicon-silicon oxide interface of Si(111)-SiO2-Cr MOS structures by DC-electric-field-induced second harmonic generation

The buried Si(111)-SiO 2 interface has been studied in transmission through planar Si-SiO 2 -CS MOS structures using DC-electric-field-induced second-harmonic generation (EISHG). The rotational anisotropy and oxide thickness dependence of EISHG have been measured. Multiple reflections in the oxide layer and interference effects between field-dependent and field-independent contributions to the nonlinear polarization are shown to affect the shape of the EISHG bias dependence. From a simple model the relative size of field-dependent and field-independent contributions can be estimated. In this way, information about the interface charge distribution can be obtained.