J. L. Brebner

Fabrication of long-period optical fiber gratings by use of ion implantation

We report the fabrication of long-period optical fiber gratings by use of a refractive-index increase induced by ion implantation. Helium ions were implanted in an optical fiber core through a metal mask that had a 170-microm -pitch grating with spacing of 60 microm . We obtained a wavelength-dependent effective transmission loss by use of the grating.

Refractive-index changes in fused silica produced by heavy-ion implantation followed by photobleaching

The changes in refractive index, optical absorption, and volume of synthetic fused silica resulting from the implantation of germanium and silicon ions at energies of 3 and 5 MeV are reported. Implantation changes the density and generates ultraviolet color centers in the silica, which increases the refractive index at visible wavelengths by ~1%. Irradiation of the implanted samples with 249-nm light from a KrF excimer laser photobleaches the color centers and reduces the index by more than 0.1%. Photobleaching is used to write a 4.3-microm pitch diffraction grating in the implanted silica.

Characterization of reactively evaporated TiN layers for diffusion barrier applications

Thin TiN layers have been successfully produced on Si and SiO2 by reactive evaporation combined with rapid thermal annealing. Results of composition, resistivity, and stress measurements on these layers are reported. The TiN layers have a resistivity around 40 μΩ cm and a high stress of between 1 and 6 GPa. The composition ratio of nitrogen to titanium, measured by elastic recoil detection (ERD), combined with time‐of‐flight, was found to vary between 0.8 and 1.0 depending on the deposition conditions. In addition to the stoichiometry determination, ERD also clearly shows the presence of a TiSi2 layer between the TiN and the Si substrate. It is also shown that good TiN layers can be produced by reactive evaporation for nitrogen partial pressures between 1.0 and 2.0×10−5 mbar and for titanium evaporation rates between 0.3 and 0.5 nm/s.

Correlation between oxygen-deficient center concentration and KrF excimer laser induced defects in thermally annealed Ge-doped optical fiber preforms

Abstract The amplitude of the 5 eV optical absorption band of oxygen-deficient germanium-doped silica samples (3GeO 2 :97SiO 2 ) was varied by annealing in oxygen at 1000°C for different periods of time. Each sample was irradiated with the same dose of 5 eV light from a KrF excimer laser to study the effect of the absorption band amplitude on the photo-induced changes. ESR (Electron spin resonance) and optical absorption measurements were carried out after each annealing and each laser irradiation cycle. We find that samples with an initially higher 5 eV absorption band amplitude exhibit a larger increase in the absorption bands related to the photo-induced paramagnetic Ge E′ and GEC (Germanium Electron Center) when irradiated with the same laser dose. Deconvolution of the measured spectra shows that the concentrations of the photo-induced paramagnetic Ge E′ and GEC defects are well correlated with the concentration of GLPC (germanium lone pair center) defects associated with a 5.14 eV absorption band.

Photorefractive waveguides produced by ion-implantation of fused silica

Abstract The implantation of 5 MeV silicon and germanium ions into silica forms a 4 μm thick optical waveguide near the substrates surface with a refractive index change related to that of the delivered damage. These waveguides are photosensitive due to the presence of color centres created during implantation which can be bleached by laser light illumination. We measure the optical absorption, the compaction and the refractive index of implanted samples as a function of dose. We compare the absorption bleaching efficiency of ArF and KrF excimer laser light on two similar samples and observe an overall efficiency two orders of magnitude higher in the ArF case.

Ion-implantation-induced densification in silica-based glass for fabrication of optical fiber gratings

Ion implantation induces a refractive index increase in silica-based glass, which is mainly due to densification of the glass. The refractive index increase can be used to fabricate optical fiber gratings that are formed with periodic refractive index modulation in the core of an optical fiber. In this article, the generation mechanism of the densification has been investigated through measurements of thickness changes of silica glass induced by proton and He2+ ion implantation. Furthermore, fabrication of the optical fiber grating using the refractive index increase has been demonstrated. From the result, ideal implantation conditions to fabricate the gratings are discussed.

Efficiency of TiN diffusion barrier between Al and Si prepared by reactive evaporation and rapid thermal annealing

TiN layers prepared by reactive evaporation and rapid thermal annealing were tested as diffusion barrier between Al and Si. First, Rutherford backscattering spectroscopy (RBS) analysis of Al/Ti(N)/Ti/Si and Al/Ti(N)/Si multilayer structures showed that Si does not diffuse out up to a sintering temperature of 550 °C. However, as the temperature increases beyond 450 °C, Al starts to react with TiN. This reaction leaves less than half the TiN original thickness after a 30 min anneal at 550 °C. The RBS results indicate that TiN, crystallized at a temperature around 850 °C, forms a good barrier between Al and Si. Electrical measurements on various microelectronic devices were performed to verify this. Annealing of Ti(N) at 900 °C leads to a breakdown of p‐MOS (metal–oxide–semiconductor) devices while n‐MOS devices still work properly. Annealing at 800 °C gives good results on both MOS types except that the contact resistance of a p‐type resistor is higher than desired. The electrical circuit failure is mainly ...

Induction kinetics of delayed light emission in spinach chloroplasts

Induction curves of the delayed light emission in spinach chloroplasts were studied by measuring the decay kinetics after each flash of light. This study differs from previous measurements of the induction curves where only the intensities at one set time after each flash of light were recorded. From the decay kinetics after each flash of light, the induction curves of the delayed light emission measured 2 ms after a flash of light were separated into two components: one component due to the last flash only and one component due to all previous flashes before the last one. On comparing the delayed light induction curves of the two components with the fluorescence induction curves in chloroplasts treated with 3-(3,4-dichlorophenyl)-1,1-dimethylurea and in chloroplasts treated with hydroxylamine and 3-(3,4-dichlorophenyl)-1,1-dimethylurea, the component due to the last flash only is found to be dependent on the concentration of open reaction centers and the component due to all previous flashes except the last is dependent on the concentration of closed reaction centers. This implies that the yield of the fast decaying component of the delayed light emission is dependent on the concentration of open reaction centers and the yield of the slow decaying component is dependent on the concentration of closed reaction centers.

An ERD/RBS/PIXE apparatus for surface analysis and channeling

Abstract A system for surface analysis, lattice localisation of impurities, defect studies in crystalline solids and routine ERD (elastic recoil detection) is described. The apparatus features a high vacuum chamber, a computer controlled precision goniometer and an energy plus time-of-flight mass discrimination system. First results of channeling/ERD experiments using 15–30 MeV 35Cl beams on silicon crystals implanted with B+ and BF2+ are presented, as well as data on the effect of beam induced damage on the boron distribution.

Temperature dependence of photoluminescence in InAsP/InP strained multiple quantum wells

The photoluminescence spectra of InAsP/InP strained multiple quantum wells have been experimentally determined in the temperature range 7–300 K. In order to understand the temperature behavior of the photoluminescence, a theoretical calculation is presented that takes into account the temperature‐induced variations in band gap, carrier effective mass, biaxial strain, and exciton binding energy. The results show that the energy of the transition E1H between the n=1 electron subband and the n=1 heavy‐hole subband changes as a function of temperature, and depends mainly on the evolution of the strained band gap of the InAsP layers. This is because in the temperature range 7–300 K the variations of the electron subband energy and the exciton binding energy are much less than those of the strained band gap, while the variation of the heavy‐hole subband energy can be neglected. These results also explain why, for a lattice‐matched quantum well, the variation of exciton peak energies with temperature follows tha...