Heavily B-doped polycrystalline diamond films ([B]≳1019 cm−3) are studied by Raman spectroscopy and electron spin resonance. The formation of an impurity band is accompanied by a Fano-type interference for the one-phonon scattering. Bands at 1200 and 500 cm−1 are observed in Raman spectroscopy for concentrations above 1020 cm−3. They are related to maxima in the phonon density of states, and are ascribed to disordered regions or crystalline regions of very small size. The concentration of defects associated with the paramagnetic signal observed around g=2.0030 increases drastically above 1021 B cm−3. The Mott insulator-metal transition is accompanied by the presence of a new paramagnetic signal (g=2.0007 for 2×1020 B cm−3, g=1.9990 for 1021 B cm−3) ascribed to free holes in the impurity band.

International audienceResistance switching is studied in Au/HfO2 (10 nm)/(Pt, TiN) devices, where HfO2 is deposited by atomic layer deposition. The study is performed using different bias modes, i.e., a sweeping, a quasistatic and a static (constant voltage stress) mode. Instabilities are reported in several circumstances (change in bias polarity, modification of the bottom electrode, and increase in temperature). The constant voltage stress mode allows extracting parameters related to the switching kinetics. This mode also reveals random fluctuations between the ON and OFF states. The dynamics of resistance switching is discussed along a filamentary model which implies oxygen vacancies diffusion. The rf properties of the ON and OFF states are also presented (impedance spectroscopy). © 2010 American Institute of Physic

Metal-insulator-metal capacitors using high-k oxides are known to display nonlinear capacitance-voltage (C-V) characteristics. In the present work it is proposed that such nonlinearities arise from an electrode polarization mechanism. By considering a field activated hopping conduction in the bulk (related to oxygen vacancies), a simple analytical expression is derived which relates the capacitance to the applied bias. The model is able to predict voltage coefficients of capacitance and is found to be in good agreement with experimental C-V.

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