Fabrication of Germanium-on-insulator in a Ge wafer with a crystalline Ge top layer and buried GeO2 layer by Oxygen ion implantation

The paper reports fabrication of Germanium-on-Insulator (GeOI) wafer by Oxygen ion implantation of an undoped single crystalline Ge wafer of orientation (100). Oxygen ions of energy 200 keV were implanted. The implanted wafer was subjected to Rapid Thermal Annealing to 650 C. The resulting wafer has a top crystalline Ge layer of 220 nm thickness and Buried Oxide layer (BOX) layer of good quality crystalline Germanium oxide with thickness around 0.62 micron. The crystalline BOX layer has hexagonal crystal structure with lattice constants close to the standard values. Raman Spectroscopy, cross-sectional HRTEM with SAED and EDS established that the top Ge layer was recrystallized during annealing with faceted crystallites. The top layer has a small tensile strain of around +0.4\% and has estimated dislocation density of 2.7 x 10^{7}cm^{-2}. The thickness, crystallinity and electrical characteristics of the top layer and the quality of the BOX layer of GeO_{2} are such that it can be utilized for device fabrication

GaAs a model system to study the role of electron–phonon coupling on ionization stimulated damage recovery

International audienceAbstract The latent ion tracks observed in various materials after swift heavy ion (SHI) irradiation is often explained in the framework of thermal spike model (TSM). Dominantly, SHIs deposit most of their energy via intense ionization leading to a very high density of localized electronic excitations. The energy transfer from electrons to lattice, within a time of electronic cooling ∼100 fs, is governed by the ‘electron-phonon coupling’ parameter g . In this work, GaAs is used as a model system for studying ionization-stimulated damage recovery. Controlled damage is introduced using 300 KeV Ar ion irradiation, followed by successive irradiation using 100 MeV Ag ions at ∼80 K by varying the fluence (ions cm −2 ). The TSM is utilized to explain the observed recovery. Using the previously published value of g = 3.2 × 10 12 W cm −3 K −1 for GaAs, the existing thermal spike code resulted in melting and quick quenching within ∼10 ps, suggesting the formation of SHI-induced tracks. However, experimental observations do not support the formation of tracks in pristine GaAs. Multiple simulation runs, for different g values, predict that for no melting in GaAs, g should be ⩽ 1.4 × 10 12 W cm −3 K −1 . Finally, the 3D version of the TSM is used to simulate the temperature profiles after an impact of SHI irradiation on an amorphous nano-zone embedded in a crystalline GaAs matrix. Simulations predict that the thermal spike in this zone is confined, indicating melt-flow at the crystalline-amorphous interface that can promote recovery. This lattice recovery is further supported by both RBS/C and TEM results

GaAs a model system to study the role of electron–phonon coupling on ionization stimulated damage recovery

International audienceAbstract The latent ion tracks observed in various materials after swift heavy ion (SHI) irradiation is often explained in the framework of thermal spike model (TSM). Dominantly, SHIs deposit most of their energy via intense ionization leading to a very high density of localized electronic excitations. The energy transfer from electrons to lattice, within a time of electronic cooling ∼100 fs, is governed by the ‘electron-phonon coupling’ parameter g . In this work, GaAs is used as a model system for studying ionization-stimulated damage recovery. Controlled damage is introduced using 300 KeV Ar ion irradiation, followed by successive irradiation using 100 MeV Ag ions at ∼80 K by varying the fluence (ions cm −2 ). The TSM is utilized to explain the observed recovery. Using the previously published value of g = 3.2 × 10 12 W cm −3 K −1 for GaAs, the existing thermal spike code resulted in melting and quick quenching within ∼10 ps, suggesting the formation of SHI-induced tracks. However, experimental observations do not support the formation of tracks in pristine GaAs. Multiple simulation runs, for different g values, predict that for no melting in GaAs, g should be ⩽ 1.4 × 10 12 W cm −3 K −1 . Finally, the 3D version of the TSM is used to simulate the temperature profiles after an impact of SHI irradiation on an amorphous nano-zone embedded in a crystalline GaAs matrix. Simulations predict that the thermal spike in this zone is confined, indicating melt-flow at the crystalline-amorphous interface that can promote recovery. This lattice recovery is further supported by both RBS/C and TEM results

Irradiation Temperature Dependence of Shape Elongation of Metal Nanoparticles in Silica: Counterevidence to Ion Hammering Related Scenario

Irradiation temperature (IT) dependence of the elongation efficiency of vanadium nanoparticles (NPs) in SiO2 was evaluated: The samples were irradiated with 120 MeV Ag9+ ions to a fluence of 1.0 × 1014 ions/cm2 each at ITs of 300, 433, 515, and 591 K, while the measurements were performed at room temperature. The vanadium was selected for the NP species because of the highest bulk m.p. of 1910 °C (2183 K) among all the species of the elemental metal NPs in which the shape elongation was observed. The highest m.p. could contribute negligible size changes of NPs against inevitable exposure to high temperatures for the IT dependence measurements. The elongation of V NPs was evaluated qualitatively by transmission electron microscopy (TEM) and quantitatively by optical linear dichroism (OLD) spectroscopy. The electron microscopy studies showed a pronounced elongation of NPs with ion irradiation at the elevated temperatures. The OLD signal was almost constant, or even slightly increased with increasing the IT from 300 to 591 K. This IT dependence provides a striking contrast to that of the ion hammering (IH) effect, which predicts a steep decrease with increasing IT. Combined with the other two counterevidence previously reported, the IH-related effect is excluded from the origin of the shape elongation of metal NPs in SiO2

Phase transformation of ZnMoO4 by localized thermal spike

We show that ZnMoO4 remains in stable phase under thermal annealing up to 1000 °C, whereas it decomposes to ZnO and MoO3 under transient thermal spike induced by 100 MeV Ag irradiation. The transformation is evidenced by X-ray diffraction (XRD), Raman s

Ion beam-induced shaping of Ni nanoparticles embedded in a silica matrix: from spherical to prolate shape

Present work reports the elongation of spherical Ni nanoparticles (NPs) parallel to each other, due to bombardment with 120 MeV Au(+9 )ions at a fluence of 5 × 10(13 )ions/cm(2). The Ni NPs embedded in silica matrix have been prepared by atom beam sputtering technique and subsequent annealing. The elongation of Ni NPs due to interaction with Au(+9 )ions as investigated by cross-sectional transmission electron microscopy (TEM) shows a strong dependence on initial Ni particle size and is explained on the basis of thermal spike model. Irradiation induces a change from single crystalline nature of spherical particles to polycrystalline nature of elongated particles. Magnetization measurements indicate that changes in coercivity (H(c)) and remanence ratio (M(r)/M(s)) are stronger in the ion beam direction due to the preferential easy axis of elongated particles in the beam direction