New directions in the analysis of buried interfaces for device technology by hard X-ray photoemission.

Photoelectron spectroscopy is a characterization technique which plays a key role in device technology, a field requiring, very often, a reliable and reproducible analysis of buried, critical interfaces. The recent advent of laboratory hard X-ray spectrometers opens new perspectives toward routine studies of technologically-relevant samples for the qualification of processes and materials. In this review, the status of hard X-ray photoelectron spectroscopy (HAXPES) implemented with chromium Kα excitation (5.414 keV) and applied to technological research in nanoelectronics is presented. After an account of the role of synchrotron HAXPES and the specific effects to care about at the practical level, different aspects are developed, first for illustrating the benefits of the technique through specific application cases in the field of resistive memories and power transistors. Then, we provide a status update on quantification in HAXPES, both from core-level intensities and inelastic background analysis. Finally, we present preliminary results in a novel analytical field, operando HAXPES, where a prototypical device is operated in situ during the laboratory HAXPES experiment, opening up the possibility of unravelling the mechanisms occurring at buried interfaces and governing device operation.

Fast growth synthesis of GaAs nanowires with exceptional length.

We report the first synthesis of GaAs nanowires (NWs) by Au-assisted vapor-liquid-solid (VLS) growth in the novel hydride vapor phase epitaxy (HVPE) environment. Forty micrometer long rodlike <111> monocrystalline GaAs nanowires exhibiting a cubic zinc blende structure were grown in 15 min with a mean density of 10(6) cm(-2). The synthesis of such long figures in such a short duration could be explained by the growth physics of near-equilibrium HVPE. VLS-HVPE is mainly based on solidification after direct and continuous feeding of the arsenious and GaCl growth precursors through the Au-Ga liquid catalyst. Fast solidification (170 microm/h) is then assisted by the high decomposition frequency of GaCl. This predominant feeding through the liquid-solid interface with no mass and kinetic hindrance favors axial rather than radial growth, leading to twin-free nanowires with a constant cylinder shape over unusual length. The achievement of GaAs NWs several tens of micrometers long showing a high surface to volume ratio may open the field of III-V wires, as already addressed with ultralong Si nanowires.