No abstract

Scanning capacitance microscopy ͑SCM͒ is a doping profile extraction using a nanometric probe as a gate of a metal-oxide-semiconductor ͑MOS͒ structure and measuring the differential capacitance. Thanks to the complete MOS equations, the authors propose in this article a description of the differential capacitance calculation. This analytic presentation is based on the solution of the Poisson-Boltzmann equation in the unidimensional mode in silicon and a decomposition of the probe in elementary rings giving capacitance from the surface probe and silicon. As ͓dC͑V g ͒ / dV g ͔␣͑d⌿ s / dV g ͒, this presentation yields to the importance of the surface band bending ⌿ s at the oxide-semiconductor interface. The dC͑V g ͒ / dV g calculation shows that the contact of the probe with the sample has its main contribution over a few nanometers. Results are discussed to obtain a calibration of a SCM probe available in a large range of doping and voltage and to assess the dC͑V g ͒ / dV g signal after erosion of the probe by successive scans.

Hysteresis measurements performed on graded Pt/lead zirconate titanate (PZT)/Pt structures with well oxygenated PZT films do not display any shift along the polarization axis (Voffset) as previously reported. On the other hand, when the PZT graded films were grown under low oxygen pressure, an offset voltage was measured. This shift was systematically enhanced after cycling the film as for fatigue measurements. It was also observed that the Voffset is independent of the value of the reference capacitor used in the Sawyer–Tower circuit. We propose an asymmetry in the leakage current of the structure to be at the origin of the shift along the polarization axis.

Thin films of manganite materials (Pr 0.7 Ca 0.3-x Sr x MnO 3-δ ) have been grown, from a sintered target with the same cationic composition, by rf reactive magnetron sputtering. The film and target compositions have been verified as identical, within experimental errors, by energy-dispersive scattering (EDS) analysis. It is shown for the first time, from X-ray and electron diffraction studies, that the films, grown on LaAlO 3 or SrTiO 3 substrates, are [101] oriented. Nanostructural studies show that the defects are the same as those observed in bulk materials but that the magnetic behavior is different (Curie temperature is decreased from 130 to 50K). From a structural point of view this difference in magnetic behavior is difficult to understand, but the role of the oxygen content, the small grain size observed in such films, and the strains induced by the substrate film interactions is discussed.