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The production of negative ions in cesium sputter ion sources is generally considered to be a pure surface process. It has been recently proposed that ion pair production could explain the higher-than-expected beam currents extracted from these ion sources, therefore opening the door for laser-assisted enhancement of the negative ion yield. We have tested this hypothesis by measuring the effect of various pulsed diode lasers on the O − beam current produced from Al 2 O 3 cathode of a cesium sputter ion source. It is expected that the ion pair production of O − requires populating the 5d electronic states of neutral cesium, thus implying that the process should be provoked only with specific wavelengths. Our experimental results provide evidence for the existence of a wavelength-dependent photo-assisted effect but cast doubt on its alleged resonant nature as the prompt enhancement of beam current can be observed with laser wavelengths exceeding a threshold photon energy. The beam current transients observed during the laser pulses suggest that the magnitude and longevity of the beam current enhancement depends on the cesium balance on the cathode surface. We conclude that the photo-assisted negative ion production could be of practical importance as it can more than double the extracted beam current under certain operational settings of the ion source. [ABSTRACT FROM AUTHOR]

Researchers performing radiation testing on electronic components often rely on semi-empirical prediction codes for determining the linear energy transfer (LET) (or electronic stopping force) of ions, without paying much attention to their reliability. However, it is seen that estimations calculated with different codes can have over 10% discrepancies, especially in the case of heavy ions with higher LET (e.g., xenon). As a consequence of the modern component fabrication techniques this has become an important issue when studying the radiation durability of electronics. In order to clarify this inconsistency, LET measurements for [sup.131]Xe and [sup.82]Kr in silicon have been undertaken and obtained results are presented, discussed and compared with earlier predicted data. Index Terms--Electronic stopping force, krypton, linear energy transfer, silicon, time-of-flight, xenon.

A study is conducted to show that the combination of thermal activation and ultraviolet radiation promotes a selective bonding rearrangement of the organosilicate glass matrix. The rearrangement includes a transition of the large angle Si-O-Si bonds towards the more stable small angle or 'network' configuration (~144 degree), as well as an increase in the degree of cross-linking of the matrix through condensation reactions and some minor loss of CH3 groups.

A new study investigates the structural stability of Si-C films prepared using a pulsed cathodic arc discharge method.

We investigate the structural properties of GaAsBi layers grown by molecular beam epitaxy on GaAs at substrate temperatures between 220-315 °C. Irrespective of the growth temperature, the structures exhibited similar Bi compositions, and good overall crystal quality as deduced from X-Ray diffraction measurements. After thermal annealing at temperatures as low as 500 °C, the GaAsBi layers grown at the lowest temperatures exhibited a significant reduction of the lattice constant. The lattice variation was significantly larger for Bi-containing samples than for Bi-free low-temperature GaAs samples grown as a reference. Rutherford backscattering spectrometry gave no evidence of Bi diffusing out of the layer during annealing. However, dark-field and Z-contrast transmission electron microscopy analyses revealed the formation of GaAsBi clusters with a Bi content higher than in the surrounding matrix, as well as the presence of metallic As clusters. The apparent reduction of the lattice constant can be explained by a two-fold process: the diffusion of the excess As incorporated within AsGa antisites to As clusters, and the reduction of the Bi content in the GaAs matrix due to diffusion of Bi to GaAsBi clusters. Diffusion of both As and Bi are believed to be assisted by the native point defects, which are present in the low-temperature as-grown material. [ABSTRACT FROM AUTHOR]

The growth of tungsten nitride carbide (WNxCy) films obtained by atomic layer deposition using triethylboron, tungsten hexafluoride, and ammonia precursors is determined by the density and type of reactive sites. The film properties change as a function of thickness. On silicon dioxide and silicon carbide, growth is initially nonlinear such that the transient regimes are characterized by island formation, as evidenced by a parabolic tungsten growth curve extending to film thicknesses of up to 5 nm. Such films have low densities of ∼4–6 g cm-3 corresponding to only ∼30%–45% of the bulk density of ∼13.1 g cm-3 determined for a WN0.45C0.55 composition. X-ray reflectivity, thermal desorption, and elastic recoil detection spectroscopies reveal surface roughening and compositional and density differences close to the substrate surface. The offset from linear growth in the case of WNxCy films deposited on silicon dioxide is induced by the initial reaction of silanol and siloxane groups with triethylborane resulting in passivating ethylsilyl groups on the surface. A transient regime is not observed for WNxCy growth on hydrogen-terminated silicon with the initial growth being dominated by the reduction of tungsten hexafluoride to tungsten. On silicon nitride a short transient regime is observed relative to the carbide and oxide surfaces attributed to the enhanced binding of the triethylboron precursor. [ABSTRACT FROM AUTHOR]

The solid-phase epitaxial regrowth of 175 keV Rb+-implanted α-quartz during thermal annealing in air or 18O2 was studied as a function of the temperature (<=1170 K) and the implanted Rb fluence [(0.1–6)×1016 ions/cm2]. Rutherford backscattering channeling spectrometry was used to characterize the damage profiles. The role of the oxygen exchange between the annealing gas and the SiO2 matrix was highlighted by measuring the 16O and 18O profiles by means of time-of-flight elastic recoil detection analysis. Complete epitaxial recrystallization of the amorphized layers was observed after a 1 h annealing in air (at 1170 K) or in 18O2 (at 1130 K). The recrystallization rate in air follows a two-step Arrhenius process, with activation energies of 2.7±0.4 and 0.6±0.2 eV above and below an annealing temperature of 1070 K. The three processes, namely, planar recrystallization of the amorphized a-SiO2 layer, alkali ion out-diffusion, and 16O⇔18O exchange, are highly correlated. This correlation is discussed with the help of the concept of the SiO2 network topology. Finally, the surface topography was measured using an atomic force microscope, which gave evidence of swelling of the SiO2 matrix during implantation and recompaction during epitaxy. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Elastic recoil detection with a time of flight discrimination method using [sup 127]I ions has been applied to the simultaneous determination of the H and Li depth profiles as well as of the stoichiometry of the mixed phases formed by thermal annealing in proton-exchanged LiNbO[sub 3] waveguides. For both, as-exchanged and annealed waveguides, a one-to-one local correlation between the H and Li profiles has been obtained so that [H]+[Li]=constant. Moreover, the stoichiometry of the H[sub x]Li[sub 1-x]NbO[sub 3] compound, where x is the exchange rate, has been correlated with x-ray diffraction (rocking curves) data in order to identify the generated phases after the exchange and annealing processes. In as-exchanged guides, the value x≃0.85 is mainly associated with a broad β[sub 2]-phase peak. In annealed guides, a well-defined β[sub 2]-peak is associated with x≃0.5, a broad κ[sub 2]-peak is associated with x≃0.40, a broad κ[sub 1]-peak to x≃0.19 and 0.21, and a α-shoulder to x≃0.09 and 0.12. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The growth of tungsten nitride carbide W[N.sub.x][C.sub.y] films obtained from layer deposition using triethylboron, tungsten hexafluoride, and ammonia precursors is determined by the density and type of reactive sites. A transient regime is not observed for W[N.sub.x][C.sub.y] growth on hydrogen-terminated silicon with the initial growth being dominated by the reduction of tungsten hexafluoride to tungsten.

The solid-phase epitaxial regrowth of 175 ke V Rb(super plus one)-implanted alpha-quartz during thermal annealing in air or O(sub 2)(super 18) was studied as a function of the temperature and the implanted Pb fluence. After the irradiation a continuous amorphous layer grew, which during epitaxy, decreased in thickness by a planar movement of the a/c interface to the surface.

The time of flight elastic recoil detection analysis (TOF-ERDA) technique using [(super 127)I] heavy ions is very useful for the compositional characterization of proton exchange (PE) and annealed PE waveguides. It provides reliable values for the exchange rate of various phases generated during annealing treatment.

In this paper we report a study of the effect of vacuum annealing at 400°C on the properties of normal metal-insulator-superconductor (NIS) tunnel junctions, with manganese doped aluminium (Al:Mn) as the normal metal, aluminum as the superconductor and amorphous aluminum oxide as the tunneling barrier (Al:Mn-AlOx-Al). The annealing treatment improves the stability of the junctions, increases their tunneling resistance and does not have a negative impact on the low-temperature current-voltage characteristics. The measured 1 / f resistance noise of the junctions also changes after annealing, in the best case decreasing by over an order of magnitude. All these observations show that annealing is a viable route to improve NIS junction devices after the sample has been fabricated. [ABSTRACT FROM AUTHOR]

Electron transport properties of titanium nanowires were experimentally studied. Below the effective diameter &gsim;50 nm all samples demonstrated a pronounced broadening ofthe R(T) dependencies, which cannot be accounted for by thermal fluctuations. Extensive microscopic and elemental analyses indicate the absence of structural or/and geometrical imperfections capable of broadening the R(T) transition to such an extent. We associate the effect with quantum fluctuations of the order parameter. [ABSTRACT FROM AUTHOR]

Abstract: Atomic layer deposition (ALD) is currently a widespread method to grow conformal thin films with a sub-nm thickness control. By using ALD for nanolaminate oxides, it is possible to fine tune the electrical, optical and mechanical properties of thin films. In this study the elemental depth profiles and surface roughnesses were determined for Al2O3 +TiO2 nanolaminates with nominal single-layer thicknesses of 1, 2, 5, 10 and 20nm and total thickness between 40nm and 60nm. The depth profiles were measured by means of a time-of-flight elastic recoil detection analysis (ToF-ERDA) spectrometer recently installed at the University of Jyväskylä. In TOF-E measurements 63Cu, 35Cl, 12C and 4He ions with energies ranging from 0.5 to 10MeV, were used and depth profiles of the whole nanolaminate film could be analyzed down to 5nm individual layer thickness. [Copyright &y& Elsevier]

Optical multilayer interference coatings rely on the refractive index differences and specific thicknesses of the low and high refractive index materials used in optical multilayer structures. An accurate control of important parameters such as film thick- nesses, uniformities, and refractive indexes is demanding. Atomic layer deposition (ALD) inherently possesses many characteristics beneficial for obtaining fully conformal and uniform films of specific thicknesses with excellent repeatability. Additionally, the layer-by-layer deposition of the films allows tuning of the film stack properties, such as refractive index, which is an advantage when designing optical filters. By now, Al2O3 has been most often used as a low refractive index material in ALD made interference filters because of a lack of suitable SiO2 ALD processes. To lower the refractive index from that of Al2O3, we have developed and examined various ALD processes of aluminum silicate thin films. We concentrate on reporting the refractive indexes, growth rates, and compositions of the films as these parameters are vital for screening suitable ALD processes for optical applications. By varying the amount of silicon in the AlxSiyOz thin films, the refractive indexes between 1.47 and 1.59 were obtained in this study. - [ABSTRACT FROM AUTHOR]

Collimators are widely used to define MeV ion beams. Recent studies have shown the capability of collimators to define beams of MeV ions with sub-100 nm dimensions. Such nanometer beams have potential applications in MeV ion-beam lithography, which is the only maskless technique capable of producing extremely high aspect-ratio micro- and nanostructrures, as well as in high-resolution MeV ion-beam-based tomography. The ion scattering from the collimator edges that define the beam can be a resolution-restricting factor in these applications. Scattering processes at edges are difficult to study using conventional simulation codes because of the complicated geometry. In this part of the work, the authors used the GEANT4 toolkit as a simulation tool for studying the behavior of ions impinging onto, or in close proximity to, a single straight aperture edge. Results from simulations are presented for realistic beams of 3 MeV He ions with 0.2-1 mrad divergence incident on a 100-μm-thick Ta plate. The contribution from grazing scattering of ions impinging under glancing angles of incidence <1° on the slit-edge surface plane can degrade the beam spot size and shape. Ray-tracing simulations were also performed to investigate the trajectories of ions impinging on the aperture edge and in close proximity to it. [ABSTRACT FROM AUTHOR]

The capability of collimators to define beams of MeV ions with sub-100 nm dimensions has recently been demonstrated. Such nanometer beams have potential applications in MeV ion-beam lithography, which is the only maskless technique capable of producing extremely high aspect-ratio micro- and nanostructrures, as well as in high resolution MeV ion-beam imaging. Ion scattering from the collimator edges can be a resolution-restricting factor in these applications. Scattering processes at edges are difficult to study using conventional simulation codes because of the complicated geometry. In this part of our work, the authors used the GEANT4 toolkit as a simulation tool for studying the behavior of beams of 3 MeV He ions with 0.2-1 mrad divergence impinging onto the programmable proximity aperture comprising four 100-μm-thick Ta plates. The transmission and scattering from the aperture are asymmetric due to the aperture design. For a perfectly parallel beam, the fluence of ions scattered from the aperture edges is spread over large areas. The enhancement of the fluence from the edge-scattered ions is two to three orders of magnitude smaller compared to the incident-beam fluence. Therefore, the edge scattering is not a resolution-restricting factor, and the sub-100 nm resolution is achievable. However, for diverging beams, the significant penumbra broadening of the beam spots restricts the attainable resolution. In lithography applications, the halo associated with penumbra broadening causes pattern edge roughening by producing single ion tracks in close vicinity to the pattern element edges. [ABSTRACT FROM AUTHOR]

Abstract: Low-energy heavy-ion time-of-flight elastic recoil detection analysis (TOF-ERDA) is becoming a mature technique for accurate characterization of thin films. In combination with a small tandem accelerator (∼2MV terminal voltage) and beam energies below 20MeV, it is suitable for routine analysis of key materials in semiconductor technology. In this paper we discuss advantages and drawbacks of low-energy ERDA, compared to high-energy ERDA, in terms of depth and mass resolution, detection efficiency for light elements, sample irradiation damage and quantification accuracy. The results presented are obtained with the time-of-flight telescope recently developed at IMEC. The time-of-flight is measured with timing gates based on electrostatic mirrors and is acquired in coincidence with the energy signal measured by a planar Si detector. [Copyright &y& Elsevier]