850 nm thick silica on [100] Si was implanted with 300 keV Er ions. RES profiles of as-implanted Er yielded mean depths (d) over bar of 105 nm and 85 nm for doses of 2.1 x 10(16) cm(-2) and 8.2 x 10(16) cm(-2), respectively. Annealing at 1200 degrees C for 4 h gave (d) over bar of 169 nm and 85 nm for low and high dose. After 1275 degrees C 4 h anneal for the high dose (d) over bar was 98 nm, for the low dose 2 peaks developed with (d) over bar of 332 nm and 694 nm, XTEM at the low dose samples showed Er containing inclusions of mean radii 19.2 nm (1200 degrees C) and 27.1 nm (1275 degrees C) with similar Er depth distributions as those measured by RES. A diffusion and transport mechanism of precipitates driven by strain induced by radiation damage during implantation and thermal expansion is proposed. (C) 1999 Elsevier Science B.V.

The channeling technique is an interesting and powerful tool for the determination of impurity lattice sites in single crystals, Since the investigation of light impurities in heavy matrices using the Rutherford backscattering spectrometry/channeling technique is often very difficult or impossible, the combination of particle induced x-ray emission (PIXE) with the channeling effect is an important alternative, Experimental results for various impurities in cubic and non-cubic crystals are presented to show the feasibility of the method, In order to permit the quantitative analysis of such PIXE/channeling data, the computer code CASSIS was developed and successfully applied, Copyright (C) 1999 John Wiley & Sons, Ltd.

The technology and analysis of porous silicon electroluminescent devices and recent developments are described. An increase of efficiency in the blue range is achieved by the introduction of metals into the pores. The technologies to do this are electroplating and coevaporation. Devices with a polysilicon top layer show promising results; a quantum efficiency of 4×10−2% is measured. In order to investigate oxidation, degradation and local porosity, RBS (Rutherford Backscattering Spectroscopy) is used. © 1997 Elsevier Science S.A.

Optical properties and scintillation responses of cerium doped gadolinium-scandium-aluminum garnets (GSAG), pulled by the Czochralski method, were studied with regard to applications in scintillation counters. Scintillation responses were investigated for irradiation with charged particles, γ-rays and neutrons. The observed decay constant (τ = 120 ns) is shorter than in common inorganic scintillators like NaI(T1) and bismuth germanate (BGO). The attenuation coefficient exceeds the value reported for Nal(T1). GSAG(Ce) shows a higher light yield (30% when compared with NaI(T1)) and better energy resolution (12.5% for 662 keV γ-rays from 137Cs) than BGO. To demonstrate the feasibility for neutron detection, crystals were irradiated with slow neutrons (from 14.7 meV to 120 meV) from a neutron diffraction spectrometer at the Grenoble pile Melusine and fast neutrons (≥ 7.9 MeV) from the Stuttgart Dynamitron accelerator using the 9Be(α, n)12C reaction.

Synthetic garnet crystals (gadolinium gallium garnet GGG, yttrium aluminum garnet YAG) have been used to study the behaviour of the crystal lattice after implantation of heavy ions (cerium, praseodymium) with high energy (1.0 to 2.5 MeV) and varying doses. The radiation damage was analyzed using Rutherford backscattering spectrometry (RBS) combined with the channeling effect. Depth profiles of the defects, the amorphization dose and the penetration depth of the damage could be obtained and compared with simulation calculations. In some cases the depth profiles of the implanted ions themselves could be measured. With heat treatment at temperatures up to 1400°C the produced damage can be annealed almost completely.

Nitrogen was implanted in 〈110〉-oriented silicon and in thermally formed silicon dioxide layers. After implantation the systems were annealed to reduce radiation damage. These implanted systems were investigated with ion beam methods as RBS and NRA to determine the depth distribution of the nitrogen and the oxygen with regard to the implantation and annealing parameters.

The lattice site of iron in potassium niobate has been investigated by channeling of He-ions in combination with simultaneous Rutherford backscattering analysis (RBS), nuclear reaction analysis (NRA) and particle induced X-ray emission (PIXE). He-ions with energies of 3.1 MeV were used at the Dynamitron accelerator of the university at Stuttgart. Oxygen was detected by the resonant 16O(α,α)16O nuclear reaction at 3.05 MeV. Two crystals containing 0.12 mol% iron cut perpendicular to the 〈100〉 and 〈110〉 axis directions according to the cubic configuration of the lattice have been examined. Angular PIXE yield profiles of axial channeling close to the 〈100〉, 〈110〉, 〈111〉 and 〈221〉 axes have been compared for iron, niobium and potassium. Also computer simulations have been performed and compared with the measured data. Close resemblance between the angular yield profiles for K and Fe has been found. Therefore we conclude that Fe occupies K lattice sites in Fe:KNbO3. This result is also supported by computer simulations.

The dependence of the Li-7(p, alpha)He-4 minimum yield on the magnesium concentration has been investigated for lithium niobate single crystals doped with MgO (between 0 and 9 mol% in the congruent melt) using proton channeling in combination with NRA. For all experimentally investigated axes - except the [0001]-axis - systematic Mg-concentration dependent variations of the Li-NRA minimum yield have been observed. The comparison of these experimental observations with the results of the evaluations based on the continuum potentials supports the assignments for the lattice sites of Mg from recent IBA-experiments.

Abstract The dependence of the 7 Li(p, α) 4 He minimum yield on the magnesium concentration has been investigated for lithium niobate single crystals doped with MgO (between 0 and 9 mol% in the congruent melt) using proton channeling in combination with NRA. For all experimentally investigated axes — except the 〈0001〉-axis — systematic Mg-concentration dependent variations of the Li-NRA minimum yield have been observed. The comparison of these experimental observations with the results of the evaluations based on the continuum potentials supports the assignments for the lattice sites of Mg from recent IBA-experiments.

The lattice position of magnesium in lithium niobate has been investigated for single crystals doped with MgO (between 0 and 9 mol% in the congruent melt) using a combination of RBS, PIXE and NRA with channeling. Mg seems to be collinear with the niobium and lithium in the c-axis for the whole concentration range. Concentration dependent effects with a threshold of about 1 mol% MgO for other axes have been observed. For low concentrations experimental results and computer simulations performed with our recently developed program CASSIS indicate that magnesium occupies an octahedral site near lithium while for higher concentrations the regular lithium site and an octahedral position near niobium is found to be occupied.

Lattice sites of Ti diffused and doped in LiNbO3 have been determined by ion channeling analysis in combination with Rutherford backscattering, PIXE and NRA. 3 mole% bulk doped Ti (5.6×1020 cm-3) occupies Li sites only, whereas diffused Ti (9 mole%, 1.7×1021 cm-3 surface concentration) resides on Li sites as well as Nb sites.

Buried layers have been produced by implanting carbon with an energy of 100 keV in silicon wafers and subsequent annealing. These layers were used as an etch stop in KOH. The samples were analyzed with RBS, channeling and PIXE with regard to the depth distribution of carbon, the annealing of the silicon layer at the surface and the effect of segregation. Various implanting temperatures and annealing parameters were used. Recrystallisation of the silicon surface layer was observed by channeling measurements. With the PIXE method minor surface contaminations caused by etching and rinsing of the wafers were found. The depth profiles measured by RBS were compared to Monte Carlo calculations with the TRIM program. Furthermore, the thicknesses of the layers were also calculated by measurements of optical interferences in reflectivity. These were in good agreement with the RBS results,

In order to increase the refractive indices of LiNbO3 just beneath the surface, i.e. to produce waveguides, titanium was incorporated into y-cut substrates by two different methods: Evaporated Ti layers were either diffused at 1000°C or mixed into the substrate with a 3 MeV Ti+ beam. Radiation damage caused by ion beam mixing was removed by epitaxial regrowth. The resulting Ti concentration profiles were investigated by means of secondary ion mass spectrometry. The diffused profiles could be fitted by half Gaussians with a diffusion constant ofD = 5.25 × 10−17 m2/s at 1000°C. The ion beam mixed and annealed profiles show a non-zero slope at the surface and differ significantly from Gaussians.

He implanted LiNbO 3 waveguides have been investigated by dark and bright line spectroscopy. The refractive index profiles were reconstructed with an improved inverse WKB procedure. In the region of electronic damage the resulting profiles are very reliable. Likewise the surface-side flank of nuclear damage induced refractive index decrease is reproduced with high accuracy. In contrast with other reconstruction schemes we determine refractive indices close to the surface with an accuracy better than 2 × 10 −4 . However, the full range of nuclear damage cannot be explored. We discuss how the profile parameters depend on ion energy and irradiation dose. At 3.17 MeV the helium enriched layer seems to saturate for doses above 5 × 10 15 cm −2 . Electronic damage increases the ordinary and decreases the extraordinary refractive index, more for higher doses and less for higher energies.

In a KNbO3 single domain substrate crystal a permanent multimode waveguide has been produced for the first time by implantation of 2 MeV He+ ions. Annealing is unnecessary since electronic damage is small. The irradiation flux was controlled such that no unwanted phase transitions or domain formation occured. The refractive index profile was investigated by dark line mode spectroscopy and reconstructed by a new inverse WKB procedure. The waveguiding layer has a thickness of about 3 μm, in the region directly below this layer the refractive index is decreased by more than 0.1.

A severe problem in He+ implanted LiNbO3 waveguides is the tunneling of electromagnetic energy through the ion induced potential barrier of lowered refractive index. We drastically reduced this leakage, especially occuring for higher order modes, by varying the impact angle during the implantation thus producing a broader barrier.