Ge-rich islands have been grown on Si (100) substrates by molecular beam epitaxy. Their density and size distribution are analysed atomic force microscopy as a function of growth temperature, rate Ge coverage. Overgrown studied transmission electron microscopy, Raman scattering photoluminescence. The first results photocurrent spectroscopy Si/Ge/Si pin diodes show the expected shift energy gap. Based these results, novel device applications in proposed.

Context. Under cosmic irradiation, the interstellar water ice mantles evolve towards a compact amorphous state. Crystalline amorphisation was previously monitored mainly in keV to hundreds of ion energies.

Astrophysical ices are exposed to different radiation fields including photons, electrons and ions. The latter stem from interstellar cosmic rays (CR), the solar stellar winds, shock waves or trapped in magnetospheres of giant planets. We briefly discuss physics energy deposition by ion ir condensed matter experimental methods study induced effects. then present results on effects such as sputtering, amorphisation compaction, dissociation molecules, formation new molecular species after...

Reflection measurements in the near-band-edge region of bulk AlN crystals have been performed as a function temperature. The optical reflectance spectra an $a$-face sample show feature at about 6.029 eV, which we assign to free exciton $A$. observation $A$ first excited state yields estimated values direct band gap and limit electron effective mass. Optical on samples with two different crystallographic orientations allow transitions associated selection rules related so-called $A,B$, $C$...

Deep inside dense molecular clouds and protostellar disks, interstellar ices are protected from stellar energetic UV photons. However, X-rays cosmic rays can penetrate these regions triggering chemical reactions, dissociation, evaporation processes. We present experimental studies of the interaction heavy, highly charged, ions (46 MeV <sup>58<sup/>Ni<sup>13+<sup/>) with ammonia-containing H<sub>2<sub/>O:NH<sub>3<sub/> (1:0.5) H<sub>2<sub/>O:NH<sub>3<sub/>:CO (1:0.6:0.4) in an attempt to...

<i>Context. <i/>Within dense interstellar clouds, from their periphery to regions deep inside, ice mantles on dust grains are exposed cosmic-ray irradiation. Various swift ions contribute protons iron in the keV TeV energy range. Observations show that some lines of sight condensed CO molecules an important component ice.<i>Aims. <i/>We irradiate ices with Ni relatively high (50 and 537 MeV) simulate effects produced by fast heavy grain mantles.<i>Methods. <i/>CO gas is a CsI substrate at 13...

<i>Context. <i/>Ices present in different astrophysical environments are exposed to ion irradiation from cosmic rays (H heavier than Fe) the keV GeV energy range.<i>Aims. <i/>The objective of this work is study effects produced ices by heavy ions at relatively high energies (MeV) electronic loss regime and compare them with those protons.<i>Methods. <i/>C<sup>18<sup/>O<sub>2<sub/> was condensed on a CsI substrate 13 K it irradiated 46 MeV <sup>58<sup/>Ni<sup>11+<sup/> up final fluence...

Context. Cosmic ray ion irradiation affects the chemical composition of and triggers physical changes in interstellar ice mantles space. One primary structural induced is loss porosity, evolve toward a more compact amorphous state. Previously, compaction was monitored at low to moderate energies. The existence threshold stopping power has been suggested.

An experimental study on the interaction of heavy, highly charged, and energetic ions (52 MeV Ni^13+) with pure H2O, CO2 mixed H2O:CO2 astrophysical ice analogs is presented. This analysis aims to simulate chemical physicochemical interactions induced by heavy cosmic rays inside dense cold environments such as molecular clouds or protostellar clouds. The measurements were performed at ion accelerator GANIL (Grand Accelerateur National d'Ions Lourds in Caen, France). gas samples deposited...

The emission of light in the blue-green region from cubic InxGa1-xN alloys grown by molecular beam epitaxy is observed at room temperature and 30 K. By using selective resonant Raman spectroscopy (RRS) we demonstrate that due to quantum confinement effects taking place phase-separated In-rich dots formed layers. RRS data show In content fluctuates across volume We find dot size alloy fluctuation determine wavelengths.

Cathodoluminescence experiments were performed on a high-quality AlN epitaxial film grown by organometallic vapor phase epitaxy large single crystal substrate. The low-temperature near-bandedge spectra clearly show six very narrow lines. thermal quenching behavior of these emission lines provides insight how to assign them free and bound exciton recombination processes. binding energy for the free-exciton-A in was found be nearly twice that GaN. observation first excited state permitted us...

We investigate the room temperature ferromagnetism of nanocrystalline Co-doped $\mathrm{Ce}{\mathrm{O}}_{2}$ films electrodeposited onto Si(001) substrates. The films, containing from $0.5\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}13.2\phantom{\rule{0.3em}{0ex}}\mathrm{at.}\phantom{\rule{0.2em}{0ex}}%$ Co, present oxygen-vacancy formation with a considerable inclusion Co into lattice without evidence metallic clusters or secondary phase formation. correlate robust this...

Laboratory data of CH4 ice radiolysis promoted by fast heavy ions are obtained infrared spectroscopy (FTIR). molecules condensed on a CsI substrate at 15 K, and the layer is bombarded 220 MeV 16O7+ ion beam. The thickness thin enough to be traversed projectiles constant velocity close equilibrium charge state. induced dissociation gives rise formation molecular species CH3, C2H2, C2H4, C2H6, C3H8. Their cross sections determined. C2H6 represent most abundant daughter molecules. carbon budget...

The chemical and physical effects induced by fast heavy ion irradiation on frozen pure methanol (CH3OH) at 15 K were studied. These energetic ions can simulate the energy transfer processes that occur cosmic ray of interstellar ices, comets icy Solar system bodies. analysis was made infrared spectroscopy (Fourier transform infrared) before after irradiation, with 16-MeV 16O5+, 220-MeV 16O7+, 606-MeV 65Zn20+ 774-MeV 86Kr31+ beams. Integrated values absorbance main bands determined. CH3OH...

Methane (CH4) ice is found in the interstellar medium and several bodies of Solar system, where it commonly exposed to cosmic rays stellar winds. The chemical, physical structural effects induced by fast heavy ions thin layers pure CH4 ices at 15 K are analysed mid-infrared spectroscopy (Fourier transform infrared). Different samples were irradiated with 6 MeV 16O2 +, 220 16O7 267 56Fe22 + 606 70Zn26 Grand Accélérateur National d'Ions Lourds/France. Results show that CnHm molecules, n = 2–4...

We studied the effects produced by interaction of heavy ion cosmic rays with interstellar and cometary organic molecules in solid phase. Formic acid (HCOOH) ice at 15 K was irradiated 267-MeV 56Fe22+ ions chemical evolution analysed using Fourier transform infrared spectroscopy. The destruction cross-section HCOOH formation cross-sections molecular species have been determined; sputtering yield values are also discussed. most abundant formed Fe irradiation CO, CO2 H2O. half-life frozen...

An experimental study of the interaction highly charged, energetic ions (52 MeV (58)Ni(13+) and 15.7 (16)O(5+)) with mixed H(2)O : C(18)O(2) astrophysical ice analogs at two different temperatures is presented. This analysis aims to simulate chemical physicochemical interactions induced by cosmic rays inside dense, cold environments, such as molecular clouds or protostellar well surface outer solar system bodies. The measurements were performed heavy ion accelerator GANIL (Grand Accelerateur...

The positive and neutral clusters produced by the impact of approximately 60 MeV (252)Cf fission fragments on a LiF polycrystalline target are analyzed. ion spectrum is dominated (LiF)(n)Li(+) series, n = 0-7, exhibiting total yield 2 orders magnitude higher than that (LiF)(n)(+) series. for dominant series decreases roughly as exp(-kn), where k 0.9 0-3 0.6 heavier (n 4-9), while also exponentially increases with 0.6. Theoretical calculations were performed (LiF)(n)Li(0), (LiF)(n)Li(+),...

Accurate density functional theory (DFT) and coupled-cluster (CCSD) calculations on a series of (LiF)n=2,36 neutral clusters suggest that nanotube structures with hexagonal octagonal transversal cross sections show stability equal to or greater than the typical cubic form large LiF crystals. The was further corroborated by quantum dynamic at room temperature. fact stable were also found for other alkali halides (e.g., NaCl KBr) suggests this geometry may be widely implemented in material sciences.

The interaction of heavy ions with astrophysical ices was studied at different beamlines GANIL by infrared absorption spectroscopy. This allowed simulating in the laboratory physico-chemical modifications induced icy objects space, exposed to radiation fields such as solar wind, magnetospheric particles and interstellar cosmic rays. We briefly discuss sputtering, destruction formation molecules, amorphization compaction, implantation, finally organic molecules. latter topic is related...