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

Optical functionality of materials used in devices is the basis of modern photonics. It depends on selected photoactive impurities or low-dimensional structures, which can be tailored by ion implantation. The present survey covers cathode-luminescence spectroscopy performed after Ge, Ba, Na, Rb and Cs ion implantation in α-quartz, in connection with dynamic, laser-induced and chemical epitaxy of the surface layers amorphized during the ion irradiation. The correlations, which emerged for various luminescence bands, ion species and thermal processing methods, allows one to classify the bands into ion-specific and intrinsic ones. The microstructural properties measured by ion beam analysis and transmission electron microscopy will be combined with the luminescence data, and the role of photoactive defects in quartz and nanoparticles of the implants will be discussed. The technologically most attractive case of double Rb/Ge implantation will be highlighted, which combines the achievement of full chemical epi...

Luminescence of ion-irradiated α-quartz

Laser-induced epitaxial recrystallization after alkali-ion implantion into α-quartz

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.

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

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 and solid phase epitaxy in Ba -irradiated α -quartz

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...

U. Vetter

Papers

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

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