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A 1.4-nm decoupled plasma nitrided (DPN) oxide is used to study the response to a 60-MeV proton irradiation of nMOSFETs fabricated in a 65-nm CMOS technology. The correlation observed between the source current before irradiation and the occurrence of a higher radiation-induced gate leakage current prior to irradiation reveals that the preferential breakdown is nucleated at a preexisting weak spot in the gate oxide that overlaps the source region.

MXenes are two-dimensional transition-metal carbides and nitrides with an attractive combination of physicochemical properties, gaining notable potential in many applications. Currently, MXene synthesis is mainly performed from powder precursors whose purity and grain size define the quality and flake size of 2D sheets, typically not exceeding 2–3 μm. In this work, we successfully synthesize macroscopic nanolayered V2CTz MXenes with lateral dimensions larger than 25 μm from a V2AlC single crystal by exploiting a new strategy based on ion implantation. Ne2+ ion implantation of the single-crystal precursor is applied to introduce defects in the crystal structure of V2AlC, which facilitates chemical etching and drastically reduces the etching time down to 8 h (∼10 times lower as compared to conventional synthesis from powder precursors). The quality and morphology of exfoliated macroscopic MXene multilayers have been comprehensively studied by performing detailed analyses based on different kinds of microscopies and spectroscopies. The obtained macroscopic flakes are ideal objects to study the intrinsic physical properties of V2CTz MXenes and explore their potential application, in particular, as membranes. [ABSTRACT FROM AUTHOR]

The structural defects induced by He implantation in GaN epilayer at high fluence (1×1017He/cm2) and elevated temperature (750 °C) have been studied by conventional and high resolution transmission electron microscopy. In addition to the planar interstitial-type defects lying in the basal plane usually observed after high fluence implantation into GaN, a continuous layer of bubbles arranged in rows parallel to the implanted surface is observed in the region of maximum He concentration. This arrangement of bubbles is ascribed to interactions with dislocations. Beyond, one dimensional rod-shaped defects appear perpendicular to the implanted surface. Contrast analysis of high resolution images and atomistic simulations gives converging results in the determination of the nature and structure of these defects, i.e., gas-filled rod-shaped cavities in an overpressurized state. [ABSTRACT FROM AUTHOR]

Combining classical molecular dynamics and first-principles DFT calculations, we perfom an extensive investigation of low energy configurations for [ABSTRACT FROM AUTHOR]

The (Y,REE,U,Th)–(Nb,Ta,Ti) oxides, like euxenite, fergusonite, pyrochlore, zirconolite, are known to contain nanometric spherical cavities or bubbles, interpreted to contain radiogenic helium. In-situ analyses by Scanning Transmission Electron Microscopy (STEM) coupled with Electron Energy Loss Spectroscopy (EELS) inside nano-bubbles from an euxenite crystal, sampled in its host c. 920 Ma old pegmatite in Norway, deliver, for the first time, a positive identification of helium and an estimation of helium pressure in such bubbles. The chemically unaltered euxenite crystal proves amorphous and homogeneously speckled with bubbles ranging from 5 to 68 nm in diameter, around a log-normal distribution centered at 19 nm. The euxenite contains 9.87 wt% UO 2 and 3.15 wt% ThO 2 . It accumulated a theoretical alpha-decay dose of 3.46 × 10 20 α / g (i.e. 170 He/nm 3 ), at a dose rate of 11 926 α / g / s . This corresponds to production of 0.23 wt% He. The density of helium inside the bubbles, estimated from EELS data, ranges from 2 to 45 He/nm 3 , leading to a pressure of 8 to 500 MPa. The proportion of produced helium trapped in bubbles is about 10%. Helium bubbles clearly influence helium diffusion. They may contribute to the swelling of euxenite during amorphization and to the fracturing of the host rock. Our results suggest that dose, dose rate and structural state seem to be important parameters for the nucleation, growth and coalescence of helium bubbles but also demonstrate the crucial need of experimental studies to be able to develop a predictive model of the long term behavior of materials in response to helium irradiation. Furthermore, chemical alteration of euxenite, here materialized by fluid driven dissolution–precipitation towards silica bearing euxenite, removes the bubbles and mobilizes helium into the rock via cracks and grain boundaries. It is then suggested that helium-rich fluid released from such U–Th rich sources may percolate into surrounding rock units, inducing perturbation of the (U–Th)/He systematics of apatite and zircon in these units. [ABSTRACT FROM AUTHOR]

We propose an original method for the determination of the physical properties of nanometer sized helium bubbles using spectrum imaging in an energy-filtered transmission electron microscope. Helium bubbles synthesized by high fluence implantation and thermal annealing in silicon are investigated. The acquisition parameters are determined to optimize both signal/noise ratio and time. The limitations to the extent of observable areas on a typical sample are explained. The necessary data correction and helium K-edge position measurement procedures are detailed and the accuracy of the method is discussed. Finally helium density maps are obtained and discussed. [ABSTRACT FROM AUTHOR]

Abstract: High resolution transmission electron microscopy experiments were performed to investigate nanoplatelets induced by ion implantation into a germanium wafer. Atomistic models were used for image simulation in order to get quantitative information from the experimental images. The geometrical phase shift analysis technique was also employed to measure the strain field induced by such defects. We discuss the limits and artefacts imposed by each approach and show how these approaches can be combined to study the atomic structure of such defects and the strain field they induce. [Copyright &y& Elsevier]

A peeling mechanism exclusively driven by surface diffusion has been experimentally observed for the oxide layer covering circular buckles appearing on the free surface of implanted silicon samples when internal pressure resulting from implantation is present below the buckles. A theoretical analysis by means of a chemical potential calculation has been also performed and the possibility for the blisters to peel by a new mechanism has been analysed as a function of pressure. [Copyright &y& Elsevier]