We have formed SixGe1-x-ySny compounds on Si substrates by ion implantation and annealing and investigated their concentration profiles, crystallization, and optical properties. Ge and Sn ions were implanted in the range (2.5-10) x 10(16) Ge/cm(2) at 65 keV, and (1.0-4.0) x 10(16) Sn/cm(2) at 100 keV, resulting in a peak implant dose at a depth of 50 nm for both species. Epitaxially regrown SixGe1-x-ySny layers (110 nm thick) were produced with Ge and Sn contents that allowed bandgap tuning in the (0.88-1.1) eV range. Shifts in photoelectron binding energies (Si 2p, Ge 3d, and Sn 3d) were consistent with ternary compound formation. Sn segregation was observed for annealing temperatures >= 600 degrees C. A significant increase in the optical absorption coefficient (x10(4) cm(-1) for lambda = (800-1700) nm) was observed for SiGe, SiSn, and SiGeSn alloys, with SiGeSn having coefficients several orders of magnitude higher than for Si. Contributions of segregated Sn to these properties were observed. Metastable SixGe1-x-ySny layers were achieved, which may point to a promising route to mitigate Sn incorporation challenges for near-infrared detectors.

We investigated the formation of SixGe1-x-ySny compounds on Si by ion implantation, and changes in their optical properties in comparison to Si. Ge and Sn ions were implanted in the range 2.5x1016 to 1.0x1017 Ge/cm2 at 65 keV and 1.0x1016 to 4.0x1016 Sn/cm2 at 100 keV respectively. Advantages of Ge and Sn simultaneous diffusion were explored using different annealing strategies. Concentration profiles and crystallization were examined using Rutherford Backscattering Spectroscopy (RBS). Epitaxially regrown SixGe1-x-ySny layers were produced with Ge and Sn contents that allow tuning the bandgap in the 0.88 - 1.1 eV range. X-ray Photoelectron Spectroscopy (XPS) showed shifts in binding energies of Si 2p, Ge 3d and Sn 3d, consistent with the formation of ternary compounds. RBS, XPS, and scanning electron microscopy showed Sn segregation for annealing temperatures ≥600oC. Spectroscopic ellipsometry results indicate significant increase in the light absorption coefficient (x104 cm-1 range for wavelength = 800 - 1700 nm) for all SiGe, SiSn, and SiGeSn compounds, with SiGeSn having coefficients several orders of magnitude higher than for pure Si. Increased Sn substitutionality/solubility was achieved by ion implantation/annealing, which may point to a promising route to mitigate Sn incorporation challenges for near-infrared detectors for optoelectronics and other applications.

Ion implantation has played a significant role in semiconductor device fabrication and is growing in significance in the fabrication of Si photonic devices. In this paper, recent progress in the growth and characterization of Si and Ge quantum dots (QDs) for photonic light-emitting devices is reviewed, with a focus on ion implantation as a synthetic tool. Light emissions from Si and Ge QDs are compared with emissions from other optically active centers, such as defects in silicon oxide and other thin film materials, as well as rare-earth light emitters. Detection of light in silicon photonics is performed via the integration of germanium and other elements into detector structures, which can also be achieved by ion implantation. Novel techniques to grow SiGe- and SiGeSn-on-Si structure are described along with their application as detectors for operation in the short-wave infrared range.

Low energy electron diffraction (LEED) peak intensities were measured to estimate surface Debye temperature for epitaxially-grown silicon thin films and for bulk Si (001). Rutherford backscattering spectroscopy (RBS, random and channeling modes) and positron annihilation spectroscopy (PAS) were used to quantify defect density and distribution in the near-surface layers. The surface Debye temperature of bulk Si (001), and 1.0 mu m, and 0.6 mu m Si on sapphire were measured to be 333 K, 299 K, and 260 K, respectively. RBS and PAS showed that the defect concentration was highest near the film/substrate interface, presumably due to the lattice mismatch, and decreased toward the top surface. The thicker film presented fewer defects in the surface and near-surface layers. We showed that a larger concentration of defects Nd in Si epitaxial films correlates with a lower surface Debye temperature following the empirical relation theta D = (365 +/- 14) - (8.1 +/- 1.5) x 10-13 Nd for our set of samples. Our study suggests the further development of LEED to estimate near-surface defect concentrations.

Amorphous hydrogenated silicon carbonitride (a-SiCN:H) thin films were grown using electron cyclotron resonance chemical vapour deposition using a mixture of methane, nitrogen, and silane as precursors. The origin of the variation of macroscopic properties such as hardness (H), elastic modulus (E), photoluminescence (PL), and the optical band gap was investigated through their correlation with the microscopic features of a-SiCN:H thin films as a function of the process parameters, including the deposition temperature and methane gas flow rate. From a microstructural perspective, the thin films were investigated using x-ray photoelectron spectroscopy, Rutherford backscattering spectrometry, elastic recoil detection, transmission electron microscopy, and x-ray diffraction. It is verified that an increase of the substrate temperature resulted in the substitution of hydrogen atoms mainly by carbon atoms, causing the density of the silicon carbide-related structures to increase in the amorphous structure of the a-SiCN:H thin films. Hardness and elastic modulus were found to increase with the deposition temperature and decreased with an increase of the methane gas flow during the deposition, resulting in higher carbon content in the films. The observed changes are ascribed to the reduced density of the weak hydrogen terminated bonds and the variation of the relative bond density of Si-C to Si-N bonds. In addition, the thin films were depth profiled using a slow positron beam to investigate the role of vacancies. The observed increase of the positronium formation with increasing deposition temperature was found to correlate with the variation of PL, where an enhancement of the visible emission originating from carbon-related defects was observed. A set of optimized process parameters to fabricate a-SiCN:H thin films with improved visible emission and hardness properties is suggested.

Silicon quantum dots (Si-QDs) of various diameters were formed by annealing of Si-rich silicon nitride (Si3Nx) films synthesized using plasma-enhanced chemical vapor deposition. To investigate the effect of annealing temperature on the luminescence of this system, samples were annealed at temperatures from 400 to 1000 °C. Photoluminescence (PL), x-ray absorption near edge spectroscopy, elastic recoil detection, and Fourier-transform infrared spectroscopy measurements were used for characterization. The authors found that luminescence originated from both quantum confinement effects (QCE) and defects, and that hydrogen passivation affects the PL intensity. For lower annealing temperatures, radiative recombination due to the QCE of the Si-QDs films was observed. For higher annealing temperatures (above 600 °C), desorption of hydrogen from the sample caused the PL intensity to decrease significantly. Si3Nx films with a lower Si content were less sensitive to this reduction in PL intensity after annealing at high temperatures (above 600 °C). Our results emphasize the importance of hydrogenation of the silicon nitride matrix if Si QDs are to be used in optoelectronic devices.

We apply perturbative effective mass theory as a broadly applicable theoretical model for quantum confinement (QC) in all Si and Ge nanostructures including quantum wells (QWs), wires (Q-wires) and dots (QDs). Within the limits of strong, medium, and weak QC, valence and conduction band edge energy levels (VBM and CBM) were calculated as a function of QD diameters, QW thicknesses and Q-wire diameters. Crystalline and amorphous quantum systems were considered separately. Calculated band edge levels with strong, medium and weak QC models were compared with experimental VBM and CBM reported from X-ray photoemission spectroscopy (XPS), X-ray absorption spectroscopy (XAS) or photoluminescence (PL). Experimentally, the dimensions of the nanostructures were determined directly, by transmission electron microscopy (TEM), or indirectly, by x-ray diffraction (XRD) or by XPS. We found that crystalline materials are best described by a medium confinement model, while amorphous materials exhibit strong confinement regardless of the dimensionality of the system. Our results indicate that spatial delocalization of the hole in amorphous versus crystalline nanostructures is the important parameter determining the magnitude of the band gap expansion, or the strength of the quantum confinement. In addition, the effective masses of the electron and hole are discussed as a function of crystallinity and spatial confinement.

We look at the relationship between the preparation method of Si and Ge nanostructures (NSs) and the structural, electronic, and optical properties in terms of quantum confinement (QC). QC in NSs causes a blue shift of the gap energy with decreasing NS dimension. Directly measuring the effect of QC is complicated by additional parameters, such as stress, interface and defect states. In addition, differences in NS preparation lead to differences in the relevant parameter set. A relatively simple model of QC, using a 'particle-in-a-box'-type perturbation to the effective mass theory, was applied to Si and Ge quantum wells, wires and dots across a variety of preparation methods. The choice of the model was made in order to distinguish contributions that are solely due to the effects of QC, where the only varied experimental parameter was the crystallinity. It was found that the hole becomes de-localized in the case of amorphous materials, which leads to stronger confinement effects. The origin of this result was partly attributed to differences in the effective mass between the amorphous and crystalline NS as well as between the electron and hole. Corrections to our QC model take into account a position dependent effective mass. This term includes an inverse length scale dependent on the displacement from the origin. Thus, when the deBroglie wavelength or the Bohr radius of the carriers is on the order of the dimension of the NS the carriers 'feel' the confinement potential altering their effective mass. Furthermore, it was found that certain interface states (Si-O-Si) act to pin the hole state, thus reducing the oscillator strength.

D. J. Lockwood, N. L. Rowell, E. G. Barbagiovanni, L. V. Goncharova, P. J. Simpson, I. Berbezier, G. Amiard, L. Favre, A. Ronda, M. Faustini, and D. Grosso National Research Council of Canada, 1200 Montreal Road, Ottawa, ON K1A 0R6, Canada Department of Physics and Astronomy, University of Western Ontario, London, ON N6A 3K7, Canada Institut Matériaux Microélectronique Nanosciences de Provence, UMR CNRS 6137, Avenue Normandie Niemen, 13397 Marseille Cedex 20, France Laboratoire Chimie de la Matière Condensée de Paris, UMR-7574 UPMC-CNRS, Collège de France, 11, place Marcelin Berthelot, 75231 Paris, France

We are developing a Positron Emission Tomography and field-cycled Magnetic Resonance Imaging (PET/FCMRI) dual modality system. The low magnetic field strength of a FCMRI system makes it possible to implement a PET system based upon novel photomultiplier tubes (PMTs), instead of solid-state photodetectors. In this work, the performance of a fine-mesh PMT (Hamamatsu H6153-70) has been investigated. In the static magnetic field, the response of gain, energy resolution, time resolution and efficiency of the mesh PMT, as well as its angular response and positioning uniformity were studied as a function of field strength (from zero up to 24 mT). In the dynamic magnetic field, the short-term recovery behavior and the long-term performance stability of the mesh PMT were studied under three dB/dt configurations (7.3, 11.0 and 14.5 T/s). The relevance of these results to the possible integration of PET with FCMRI systems is discussed.

Abstract not Available.

Using variable energy positron annihilation spectroscopy (VE-PAS) and deep-level transient spectroscopy (DLTS) techniques, a systematic investigation has been made on the annealing behavior of He-irradiation-induced defects in Si with different phosphorus and oxygen concentrations. Annealing temperature dependence of the VE-PAS spectra indicates that the annihilation of the Si defects proceeds through two annealing stages: (i) 150–250°C and (ii) 250–450°C. Taking into account the DLTS results, vacancy-phosphorus complexes and divacancies are found to be significantly annealed out in stages (i) and (ii), respectively. In particular, the annihilation velocity of the divacancies significantly depends on the oxygen concentration in the Si. Furthermore, at the end of stage (ii), the DLTS spectra also revealed that a new defect generates in Si with a relatively low oxygen concentration, which is considered to be associated with the high-order vacancy clusters formed by combination of some vacancies during the anneal-out of the divacancies. This energy level is so deep below the conduction band, that is likely to act as a thermally stable carrier recombination center.

High energy MeV ion implantation of fused silica and Ge- doped silica renders these materials photosensitive. The physical processes involved are closely related to the photosensitization of Ge-doped silica by UV irradiation but present certain characteristics that are different. We discuss the results of studied of the induced absorption and refractive index changes under different preparation conditions, annealing sequences and subsequent bleaching by ArF and KrF excimer radiation. We include the results of a study using positron annihilation spectroscopy of the defects introduced by ion implantation and subsequent annealing and bleaching.