S. Gąsiorek

Bio: S. Gąsiorek is an academic researcher from University of Göttingen. The author has contributed to research in topics: Ion implantation & Cathodoluminescence. The author has an hindex of 7, co-authored 13 publications receiving 95 citations.

Cathodoluminescence and solid phase epitaxy in Ba -irradiated α -quartz

Abstract: The luminescent properties of quartz and silica doped with photoactive ions depend on the structural and chemical properties of the matrix and doping elements. The dynamic solid phase epitaxy of α-quartz during Ba+-ion implantation at 300–1170K and its relationship to cathodoluminescence emission are investigated in this work. Rutherford backscattering channeling analysis revealed that the amorphous layer created by 1×1015 175keVBaions∕cm2 at 300K almost disappeared when the implantation temperature was raised to 1120K. Between 770 and 1100K the cathodoluminescence spectra taken at room temperature exhibit dramatic changes with the implantation temperature and allow to distinguish between color centers related to quartz, ion-irradiated silica, and implanted Ba ions. After achieving almost complete epitaxial recovery, only a violet band at 3.4eV remained, which we attribute to Ba-related luminescence centers. Samples first implanted with Ba ions and then postannealed in air or O218 atmosphere up to 1320K d...

Cathodoluminescence of α-quartz after hot Ge ion irradiation

Abstract: The fabrication of Ge-doped light-emitting devices in single-crystal α-quartz without destroying its crystal structure via the dynamic solid phase epitaxial regrowth technique is being pursued. This paper presents results on the cathodoluminescence (CL) after 120 keV Ge implantation in α-quartz at 1173 K with fluences between 1 × 10 14 and 1 × 10 16 ions/cm 2 . Rutherford backscattering-channeling analysis showed that the Ge implantation up to 4 × 10 14 ions/cm 2 produced isolated damage zones. The transition to an amorphous layer is accompanied by a strong increase in the CL output. The CL spectra taken at 10–300 K show six bands located at 260 nm (4.9 eV, UV), 288 nm (4.3 eV, UV), 383 nm (3.1 eV, violet), 453 nm (2.7 eV, blue), 511 nm (2.4 eV, green) and 620 nm (2.0 eV, red). Only the violet band is associated with the Ge-related defects or the formation of Ge-clusters; it reaches its maximum intensity at 7 × 10 14 Ge-ions/cm 2 . All the other bands are connected to various defect centers in the SiO 2 network.

Achieving epitaxy and intense luminescence in Ge /Rb-implanted α-quartz

Abstract: The luminescence properties of ion-beam doped silica and quartz depend sensitively on the ion species and fluence and the thermal processing during and after ion implantation. In an attempt to achieve high luminescence intensity and full planar recrystallization of α-quartz, we studied double Ge∕Rb-ion implantation, where the Rb ions serve as a catalyst only. Synthetic α-quartz samples were irradiated with 175 keV Rb ions and subsequently with 120 keV Ge ions with fluences of 1×1014–1×1016ions∕cm2 and postannealed at 1170 K in air. A comparative analysis of the epitaxy, migration of the implanted ions, and cathodoluminescence (CL) were carried out. The CL spectra exhibit three strong emission bands in the blue/violet range at 2.95, 3.25, and 3.53 eV, which were assigned to Rb- and/or Ge-related defect centers. For up to 1015 implanted Geions∕cm2, large fraction (75%) of the Ge atoms reach substitutional Si sites after the epitaxy.

Cathodoluminescence versus dynamical epitaxy of Ba-ion irradiated α-quartz

Abstract: Doping α-quartz with photoactive ions without destroying its crystalline structure appears to be a promising way to tune its luminescent and structural properties. We have achieved dynamic solid phase epitaxial regrowth and cathodoluminescence of 175keV Ba-ion irradiated α-quartz in the temperature range from 300 to 1170K. Rutherford Backscattering Channeling analysis showed that the amorphous layer produced by 1×1015 Baions∕cm2 at 300K had almost disappeared at an implantation temperature of 1123K. Room temperature cathodoluminescence exhibited dramatic changes in the optical spectra as a function of the implantation temperature and allowed to distinguish between color centers related to quartz, ion-irradiated silica and implanted Ba. Between 770 and 1100K, room-temperature cathodoluminescence showed a predominant blue and other weak bands connected to various known defects in the Si-O-Si network. However, after achieving almost complete solid phase epitaxial recovery, only a violet band at 3.4eV remai...

Helium irradiation study on zircon

Abstract: Synthetic ZrSiO4 and (mildly to strongly radiation-damaged) natural zircon samples were irradiated with 8.8 MeV 4He2+ ions (fluences in the range 1 × 1013–5 × 1016 ions/cm2). For comparison, an additional irradiation experiment was done with 30 MeV 16O6+ ions (fluence 1 × 1015 ions/cm2). The light-ion irradiation resulted in the generation of new (synthetic ZrSiO4) or additional (mildly to strongly metamict natural samples) damage. The maximum extent of the damage is observed in a shallow depth range approximately 32–33 μm (8.8 MeV He) and ~12 μm (30 MeV O) below the sample surface, i.e. near the end of the ion trajectories. These depth values, and the observed damage distribution, correspond well to defect distribution patterns as predicted by Monte Carlo simulations. The irradiation damage is recognised from the notable broadening of Raman-active vibrational modes, lowered interference colours (i.e. decreased birefringence), and changes in the optical activity (i.e. luminescence emission). At very low damage levels, a broad-band yellow emission centre is generated whereas at elevated damage levels, this centre is suppressed and samples experience a general decrease in their emission intensity. Most remarkably, there is no indication of notable structural recovery in pre-damaged natural zircon as induced by the light-ion irradiation, which questions the relevance of alpha-assisted annealing of radiation damage in natural zircon.

Spontaneous formation of superconducting NiBi3 phase in Ni-Bi bilayer films

Abstract: We report the spontaneous formation of superconducting NiBi3 phase in thermally evaporated Ni-Bi bilayer films. High reaction-diffusion coefficient of Bi is believed to drive the formation of NiBi3 during the deposition of Bi on the Ni film. Cross sectional transmission electron microscopy and glancing incidence X-ray depth profiling confirmed the presence of NiBi3 throughout the top Bi layer. Superconducting transition at ∼3.9 K, close to the bulk value, was confirmed by transport and magnetization measurements. The bilayers were irradiated with varying fluence of 100 MeV Au ions to study the robustness of superconducting order in presence of large concentration of defects. Superconducting parameters of NiBi3, such as transition temperature and upper critical field, remained unchanged upto an ion dose of 1 × 1014 ions/cm2. The diffusive formation of NiBi3 in Ni opens the possibility of studying superconducting proximity effect at a truly clean superconductor-ferromagnet interface.

Tailoring the crystal growth of quartz on silicon for patterning epitaxial piezoelectric films

Abstract: Epitaxial films of piezoelectric α-quartz could enable the fabrication of sensors with unprecedented sensitivity for prospective applications in electronics, biology and medicine. However, the prerequisites are harnessing the crystallization of epitaxial α-quartz and tailoring suitable film microstructures for nanostructuration. Here, we bring new insights into the crystallization of epitaxial α-quartz films on silicon (100) from the devitrification of porous silica and the control of the film microstructures: we show that by increasing the quantity of devitrifying agent (Sr) it is possible to switch from an α-quartz microstructure consisting of a porous flat film to one dominated by larger, fully dense α-quartz crystals. We also found that the film thickness, relative humidity and the nature of the surfactant play an important role in the control of the microstructure and homogeneity of the films. Via a multi-layer deposition method, we have extended the maximum thickness of the α-quartz films from a few hundreds of nm to the μm range. Moreover, we found a convenient method to combine this multilayer approach with soft lithography to pattern silica films while preserving epitaxial crystallization. This improved control over crystallization and the possibility of preparing patterned films of epitaxial α-quartz on Si substrates pave the path to future developments in applications based on electromechanics, optics and optomechanics.

The influence of the implantation dose and energy on the electroluminescence of Si+-implanted amorphous SiO2 thin films

Abstract: Visible and infrared (IR) electroluminescence (EL) has been observed from a metal–oxide–semiconductor-like (MOS-like) structure with Si nanocrystals (nc-Si) embedded in the gate oxide fabricated with low-energy ion implantation The EL spectra are found to consist of four Gaussian-shaped luminescence bands with their peak wavelengths at ~460, ~600, ~740, and ~1260 nm, respectively, among which the ~600 nm band is the dominant one Different nanocrystal distributions are achieved by varying the implanted Si ion dose and implantation energy The nanocrystal distribution is found to play an important role in the EL The influence of the applied voltage, the implantation dose, and implantation energy on the luminescence bands has been investigated

Stable violet cathodoluminescence of α-quartz after Ge+ implantation at elevated temperature

Abstract: Doping single-crystalline α-quartz with 120keV Ge+-ion implantation under the conditions of dynamic solid phase epitaxial regrowth has been studied as function of ion fluence and substrate temperature. In particular, the light emitting properties possibly suitable for optoelectronic devices have been investigated by measuring cathodoluminescence spectra for implantation temperatures from 300 to 1223K and for analyzing temperatures from 10−300K. Rutherford backscattering channeling analysis showed that the Ge implantation produced amorphous layers varying in depth with temperature. At a fluence of 7×1014Ge-ions∕cm2 and an implantation temperature of 1073K, Ge implantation is accompanied by a strong increase in the luminescence intensity of a violet band, which we associate with Ge-related defects or Ge clusters. This violet band is very stable and has a long lifetime of 6μs. All the other bands observed are connected to known oxygen defect centers in the SiO2 network.