We have grown various thickness Ge layers on nominal and 6 • off Si(0 0 1) substrates using a low-temperature/high-temperature strategy followed by thermal cycling. A combination of 'mounds' and a perpendicular cross-hatch were obtained on nominal surfaces. On 6 • off surfaces, three sets of lines were obtained on top of the 'mounds': one along the 1 1 0 direction perpendicular to the misorientation direction and the other two at ∼4.5 • on each side of the 1 1 0 direction parallel to the misorientation direction. The surface root mean square roughness was less than 1 nm for 2.5 μm thick nominal and 6 • off Ge layers. Those slightly tensily strained Ge layers (R ∼ 104%) were characterized by 5 × 10 7 cm −2 (as-grown layers) −10 7 cm −2 (annealed layers) threading dislocation densities, independently of the substrate orientation. We have then described the 550 • C/650 • C process used to passivate nominal Ge(0 0 1) surfaces with Si prior to gate stack deposition. An ∼5 Å thick SiGe interfacial layer is self-limitedly grown at 550 • C and then thickened at 650 • C (5 Å min −1 ) thanks to SiH 2 Cl 2 at 20 Torr. Such a Ge surface passivation yields state-of-the-art p-type metal oxide semiconductor field effect transistors provided that 15 Å Si layer thickness is not exceeded. For higher thickness, elastic strain relaxation (through the formation of numerous 2D islands) occurs, followed by plastic relaxation (for a 35 Å thick Si layer).

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