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We show that the micro-scale variations in the relaxation state of amorphous silicon (a-Si) can be well-identified by Raman mapping over hundreds or thousands of μm2 in 1–2 h. Pure and relaxed a-Si is obtained by self-implantation in crystalline silicon (c-Si) followed by anneal at 500 °C. It is then locally re-implanted over micro-sized patterns to produce unrelaxed a-Si zones. Raman mappings are obtained by pointwise confocal μ-Raman and hyperspectral Raman imaging. We also measure the depth profiles of the relaxation state in re-implanted a-Si by scanning the edge of a re-implanted sample. We infer from the depth profiles that the minimal damage dose to fully de-relax a-Si is 0.04 displacements per atoms, which is an order of magnitude smaller than the fluence needed to fully amorphize c-Si. [ABSTRACT FROM AUTHOR]

We have investigated the effect of Yb substitution on the Pauli-limited, heavy-fermion superconductor, CeCoIn5. Yb acts as a non-magnetic divalent substituent for Ce throughout the entire doping range, equivalent to hole doping on the rare-earth site. We found that the upper critical field in (Ce,Yb)CoIn5 is Pauli limited, yet the reduced (H,T) phase diagram is insensitive to disorder, as expected in the purely orbitally limited case. We use the Pauli-limiting field, the superconducting condensation energy and the electronic specific-heat coefficient to determine the Wilson ratio (RW), the ratio of the specific-heat coefficient to the Pauli susceptibility in CeCoIn5. The method is applicable to any Pauli-limited superconductor in the clean limit. © EPLA, 2010.

Ge:Mn thick films (t ≈ 3 μ m) with low average Mn concentration (< 0.3 %) were prepared by ion implantation at 77 K followed by either conventional or flashlamp annealing. The films were characterized by x-ray diffraction, secondary ion mass spectrometry, magnetometry, and infrared transmission (100–6500 cm − 1 ). Post-annealing at a high enough temperature recrystallizes the amorphous Ge:Mn films without significant migration of Mn to the surface, while solid phase epitaxy does not occur, resulting in polycrystalline films. Annealing causes an estimated 50%–80% of the implanted Mn to migrate to Mn-rich clusters or form Mn 5 Ge 3 , while the remainder enters the Ge lattice substitutionally creating free holes. Evidence for free holes comes from the structure in the mid-infrared absorption coefficient that is similar to previous observations in p-type Ge. The data suggest that the maximum solubility of Mn in the Ge crystalline lattice has an upper limit of < 0.08 %. [ABSTRACT FROM AUTHOR]

A study presents a concept for the implementation of a compliant substrate by using a buried layer of nanocavities. The findings of the results show that strain relaxation are enhanced for hetrostructures grown on substrates with nanocavities.

Impurity profiles of Cu and Ag in amorphous silicon were studied before and after one year storage at room temperature and found to be indistinguishable. Since just before storage, hydrogen had been ion implanted into the uniformly metal doped layer, a diffusivity in excess of 3 x [10.sup.-24] [m.sup.2]/s would have led to an observable change in the impurity profile. Therefore the room-temperature diffusivity must be less than that (3 x [10.sup.-24] [m.sup.2]/s), which in turn implies one of two possibilities: either the interstitial diffusivity is much lower than previously determined, or the metal impurities were not fully detrapped by the implanted hydrogen. A subsequent thermal anneal at 450°C confirmed that the detrapping and diffusion of Ag and Cu in H-implanted amorphous Si conforms to its normal behaviour. The low value of the room-temperature diffusivity is important for the interpretation of forthcoming measurements on high-energy ion tracks in amorphous Si. PACS Nos.: 66.30.J-, 71.55.Jv, 61.72.uf, 81.05.Gc Nous avons etudie les profils d'impurete de Cu et de Ag dans du silicium amorphe, avant et apres remisage d'un an a la temperature de la piece et nous observons qu'ils sont indiscernables. L'implantation ionique d'hydrogene dans la couche dopee metalliquement aurait cause un changement observable dans les profils d'impurete si le coefficient de diffusion avait ete plus grand que 3 x [10.sup.-24] [m.sup.2]/s. Ce coefficient est donc plus petit que 3 x [10.sup.-24] [m.sup.2]/s, ce qui implique deux possibilites. Soit que la diffusivite est plus faible que determinee precedemment, soit que les impuretes metalliques n'ont pas ete liberees de leur piege par l'hydrogene. Un recuit subsequent a 450°C confirme que la liberation et la diffusion de Ag et Cu dans du Si amorphe avec implantation de H sont conformes au comportement normal. La basse valeur du coefficient de diffusion a la temperature de la piece est importante dans l'interpretation de mesures a venir de trajectoires d'ions de haute energie dans du Si amorphe. [Traduit par la Redaction], Introduction Metals such as Cu, Ag, and Au are known to be very fast diffusers in crystalline (c-) Si [1] and Ge [2]. In the study of amorphous silicon (a-Si), [...]

The structural properties in InAs nanocrystals formed in Si by sequential implantation of In and As ions are studied in detail. The result has a significant impact on the optical properties of the resulting samples.

A new study investigates C incorporation and lattice sites on Ge1-yCy alloy layers (y< or = 0.02) grown on Ge(001) at temperatures between 200 and 550 deg C.

A new study investigates the evolution of the magnetic behavior and microstructure of Co/Ag multilayer mixtures caused by 1 MeV Si+ ion bombardment.

A new study uses x-ray diffraction and transport and magnetic measurements to investigate the magnetic, structural and transport properties of rf sputtered Co/Ag multilayers with differing Co-layer thicknesses.

The structural and electrical defects in amorphous silicon were investigayted using positron annihilation spectroscopy and free carrier lifetime measurements. The results showed that thermal annealing at 500 degrees celsius decreased the defect density and reduced the band gap state density in the material. Some of the defects were associated with positron-trapping and vacancy-type structural defects.

We have studied the structural, chemical, and magnetic properties of InP following coimplantation with high energy P and Mn ions to fluences in excess of 1016 cm-2 and subsequent annealing above 600 °C. Rutherford backscattering spectrometry, x-ray diffraction, secondary ion mass spectrometer, and transmission electron microscopy measurements reveal that rapid thermal annealing causes only a partial epitaxial recrystallization of the layer amorphized by the implantations; the remaining region up to the surface crystallizes incoherently but retains most of the implanted Mn. Magnetic measurements demonstrate that fully three quarters of the Mn has been incorporated into MnP nanoparticles embedded into this polycrystalline InP region. The remaining Mn is most probably incorporated into the InP lattice but gives only a paramagnetic response that can be described by a simple Brillouin function at temperatures down to 5 K. [ABSTRACT FROM AUTHOR]

We have studied the structural and magnetic properties of Mn implanted (1–5×1016 cm-2, 200 keV) into InP and GaP substrates, before and after rapid thermal annealing. As revealed by Rutherford backscattering spectrometry, secondary ion mass spectrometry, and transmission electron microscopy measurements, implantation results in an amorphous surface layer 300 nm deep, and subsequent annealing gives rise to epitaxial recrystallization of this layer accompanied by a segregation of most of the Mn into clusters about 60 nm in diameter at the surface. Magnetic measurements indicate ferromagnetic behavior only for the annealed samples with TC close to 290 K, characteristic of bulk MnP, whose presence is confirmed by diffraction data. In addition, there is no evident dependence of the magnetic and structural properties on the doping type or level of the substrates. [ABSTRACT FROM AUTHOR]

Co/Cu multilayers with composition wavelength ranging from 2 to 10 nm have been deposited and irradiated at various doses from 1×10[sup 14] to 3×10[sup 16] ions/cm[sup 2] using 1 MeV Si[sup +] ions. The ion-beam-induced variation in structural properties such as interfacial mixing, interface roughness, crystallographic texture, and grain size, are characterized by a variety of x-ray scattering techniques. Irradiating Co/Cu multilayers generate metastable Co–Cu alloys whose electrical and magnetic properties have been found to be very similar to the Co–Cu alloys fabricated by other nonequilibrium methods. Fitting to the low-angle x-ray reflectivity spectra using a standard optical model yields a mixing efficiency comparable to the prediction of a ballistic ion-beam mixing model, and interfacial mixing widths consistent with the values estimated from saturation magnetization measurements. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have studied the effects of ion irradiation at low doses (<5×10[sup 14] ions/cm[sup 2]) on the structural properties, giant magnetoresistance (GMR), and interlayer magnetic coupling in Co/Cu multilayers. X-ray analysis combined with magnetic and resistivity measurements reveal that intermixing is promoted by ion irradiation while the periodic structure and crystallographic properties of the multilayers are not significantly altered. The GMR ratio of a multilayer decreases monotonically with ion dose. However, thermal annealing on an irradiated multilayer results in sharp recovery of the reduced GMR, and can be associated with a backdiffusion process in metastably intermixed regions. Hence, using ion irradiation and subsequent annealing, the GMR of a single multilayer can be altered reversibly over a wide range. The variation of GMR upon irradiation (or annealing) is accompanied by significant suppression (or improvement) of the antiferromagnetic interlayer coupling. The correlation between GMR and AF coupling, as well as the role of enhanced electron scattering at interfaces during these processes are discussed. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The formation of nanocavities in InP(001) by room-temperature He implantation and subsequent thermal annealing was studied using a combination of high-resolution x-ray diffraction (HRXRD) and cross-sectional transmission electron microscopy (XTEM) analyses. The nanocavities size and depth distributions were measured as a function of He ion dose [lowercase_phi_synonym][sub He] (1×10[sup 16] to 9×10[sup 16] cm[sup -2]) and ion energy E (25 to 70 keV), as well as annealing temperature T[sub a] (600 to 750 °C) and time t[sub a] (5 to 25 min). HRXRD scans from annealed samples indicate an expansion of the InP lattice, contrary to what is usually observed following heavy-ion implantation. The critical [lowercase_phi_synonym][sub He] and T[sub a] values for the formation of nanocavities were found by XTEM analysis to be between 1 and 2×10[sup 16] cm[sup -2] and between 600 and 620 °C, respectively. Cavities of diameter 4–50 nm with {110}, {101}, and {001} facets were obtained. Increasing T[sub a] and t[sub a] resulted in larger cavities and increasing [lowercase_phi_synonym][sub He] produced a larger number of cavities. Furthermore we find that nanocavities are metastable as their size first increases with annealing temperature and time but then decreases until they disappear for t[sub a]>25 min at T[sub a]=640 °C or t[sub a]>10 min at T[sub a]=750 °C. Results are compared with similar work carried out on He-implanted silicon and differences between the two materials are explained in terms of defect diffusivity and surface energy, higher diffusivity enhancing cavity collapse and lower surface energy enhancing cavity growth. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The structural properties of InAs nanocrystals formed in Si by sequential implantation of In and As ions are studied in detail. We use a combination of x-ray diffraction, Rutherford backscattering spectroscopy, channeling, and transmission electron microscopy analyses to demonstrate that, regardless of the order in which ion species are implanted, InAs nanocrystals can be produced in Si (100) by means of sequential ion implantation complemented by subsequent thermal annealing. Whichever the order of implantation is, the nanocrystals are facetted and terminated by (111) planes, the epitaxial relationship being cube-on-cube, (100)[SUBInAs]&verbar; (100)[SUBSi] with [001][SUBInAs]&verbar; [001][SUBsi], for most InAs nanocrystals. The size distribution of nanocrystals is much affected by the sequence of implantation. With As ions implanted first, nanocrystals of different sizes are concentrated within one and the same layer under the sample's surface. In contrast, when In ions are implanted first, nanocrystals of different sizes are produced separately in space, forming a three-layer structure. As a consequence, inverting the order of implantation entails considerable changes in the morphology of the InAs nanocrystals obtained, affecting both their concentration profile and their size distribution. The result has a significant impact on the optical properties of the resulting samples. [ABSTRACT FROM AUTHOR]