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.

Helium irradiation study on zircon

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.

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

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.

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

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

https://iopscience.iop.org/article/10.1088/0957-4484/18/45/455306/pdf

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

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.

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

Even at low fluences doping of quartz by ion implantation results in amorphization. Here we report on the measurement of cathodoluminescence and surface structures during solid phase epitaxy in Na-implanted α-quartz annealed in 18O2 atmosphere. Complete epitaxy was achieved under appropriate conditions of ion fluence, annealing temperature and time. The crystalline structure of the samples was studied by Rutherford backscattering channelling spectroscopy and the 18O–16O exchange between the matrix and 18O2 annealing gas by elastic recoil detection analysis. In the cathodoluminescence spectra taken at room temperature, five bands were identified and assigned to various defect centres. Two of the bands in the violet region at 3.25 and 3.65 eV strongly vary in intensity at 843–1173 K annealing temperature and appear to be intimately correlated with the presence of Na-ions in the implanted region of the matrix. Finally, atomic force microscopy enabled, for the first time, the observation of the correlation of surface structures and epitaxy.

Solid phase epitaxy of Na-ion irradiated α-quartz: Cathodoluminescence, kinetics and surface morphology

Doping of α-quartz by ion implantation leads to amorphization even at low fluences, but subsequent annealing in air or oxygen can restore the crystalline order (chemical epitaxy). Here we report on measurements of RBS channeling and cathodoluminescence (CL) spectra during chemical epitaxy of α-quartz irradiated with 50-keV Na-ions and annealed in 18O2-gas. In particular, the variation of the damage profile and CL spectra (the latter taken at 10 K and 300 K) as functions of the ion fluence will be discussed. The CL spectra at 10 K are dominated by a 2.90-eV band and differ greatly from the ones taken at 300 K; the intensity of this band increases strongly with the Na ion fluence. Some conclusions concerning the underlying photoactive defect structures will be drawn.

/pdf/na-irradiated-alpha-quartz-chemical-epitaxy-and-luminescence-152o1ztw6a.pdf

Na-irradiated alpha-quartz: chemical epitaxy and luminescence

Doping quartz by ion implantation can be an efficient route to achieve a high luminescence output. In our recent studies on cathodoluminescence (CL) after Ge-, Ba- and alkali-ion implantation in crystalline α-quartz, a number of intrinsic and ion-specific CL bands have been observed and associated with specific defects in the amorphous silica or recrystallized quartz matrix. Ion-specific bands whose properties are correlated with the implanted ion species have been studied in their thermal behaviour under the conditions of dynamic, chemical or laser epitaxy. In this review article, we discuss mainly properties of the strong blue–violet CL emission band at 3.25 eV, which occurs after group-IV (Si, Ge, Sn) and alkali-ion implantation and could not unambiguously explained so far. Arguments are presented for its neutral-oxygen-vacancy structure.

S. Gąsiorek

Papers

Solid phase epitaxy of Na-ion irradiated α-quartz: Cathodoluminescence, kinetics and surface morphology

Na-irradiated alpha-quartz: chemical epitaxy and luminescence

Cathodoluminescence of ion-irradiated α-quartz: the 3.25-eV band