Implantation and Activation of Phosphorus in Amorphous and Crystalline Germanium Layers

We have investigated phosphorus implantation and activation in amorphous and crystalline Ge layers, deposited on Si substrates. The structure of the Ge layer has only limited influence on the dopant profile and diffusion after annealing. Surprisingly, crystalline Ge layers show better electrical results after implantation and dopant activation. For the amorphous layer, the solid phase epitaxy process is influenced in the neighborhood of P, leading to point defects, which inhibit electrical activation. This result implies that when a crystalline Ge layer is amorphized during implantation of high doses, the dopant activation can be significantly reduced. Reduced temperature ramping improves activation of P in amorphous Ge layers

Functionality of thermally hydrogen-passivated interfaces of oxidized crystalline arrays of Si nanowires on (100)Si

Electron spin resonance studies have been performed on arrays of single-crystalline Si nanowires (NWs), 375 nm long and of top diameter of about 5 nm, fabricated on (100)Si by top-down etching and final thinning by thermal oxidation in dry O2/N2 at $1150\ ^{\circ}\text{C}$ . The SiO2/SiNW interfaces, showing a density of inherent electrically detrimental $P_{b0}\ (\text{Si}_{3}\equiv{}\text{Si}^{\bullet})$ defects substantially exceeding that of standard technological (100)Si/SiO2, are of inferior electrical quality. An extensive study of the passivation kinetics in H2 and forming gas ambient reveals that, even under optimized conditions, the defect system cannot be inactivated to device grade (at best, $40\times$ improvement in H2), due to the excessive interface stress as exposed by the enhanced spread in activation energy for hydrogen passivation kinetics. The data reveal the inability, of intrinsic nature, to sufficiently suppress $P_{b0}$ defects, preventing to reach device-grade functioning of solar cells using single-crystalline NW arrays on (100)Si in the current state of manufacturing

Multi-frequency ESR analysis of the E′

A multifrequency electron spin resonance study of the E′δ defect in six SiO2 glasses irradiated by UV, VUV, or 60Co γ-rays, points to an electronically rigid structure with no dynamic rearrangement occurring in the temperature range T ≥ 4.2 K. Reassuringly coinciding over all frequencies and T's applied, the average intensity ratio of the 100 G 29Si hyperfine doublet to the central Zeeman signal points to delocalization of the unpaired spin over n = 4 or 5 equivalent Si sites, thus refuting the Si dimer model. A noteworthy revelation is that E′δ is only observed in those (3) silica types studied also showing the Al E′ center in the as γ-irradiated state. This may signify some indirect role of charge compensators/traps in activating/stabilizing E′δ centers, relevant to further theoretical modeling

Size dependence of P

Size-controlled Si nanocrystals (nc's) of ∼ 2 to 5 nm diameter embedded in amorphous (a-)SiO2 are extensively studied by electron spin resonance (ESR) and photoluminescence (PL). The PL quenching Pb-type (Si dangling bond) interface defects ––Pb(0) and Pb1 centers–– are investigated as a function of Si nc's size and effective interface area with the embedding SiO2. It is shown that the effective areal Pb-type defect density at the nc-Si/SiO2 interface remains approximately constant, indifferent of the nc size. While Si nc's larger than ≈3.5 nm are found to house, on average, at least one PL quenching Pb-type defect, about 75% of the as-annealed 2 nm Si nc's appear Pb-free. Additional study on the effect of heat treatment in H2 indicates this step to be more efficient in inactivating Pb(0) than Pb1 for all Si nc sizes

Classification and control of the origin of photoluminescence from Si nanocrystals.

Silicon dominates the electronics industry, but its poor optical properties mean that III–V compound semiconductors are preferred for photonics applications. Photoluminescence at visible wavelengths was observed from porous Si at room temperature in 1990, but the origin of these photons (do they arise from highly localized defect states or quantum confinement effects?) has been the subject of intense debate ever since. Attention has subsequently shifted from porous Si to Si nanocrystals, but the same fundamental question about the origin of the photoluminescence has remained. Here we show, based on measurements in high magnetic fields, that defects are the dominant source of light from Si nanocrystals. Moreover, we show that it is possible to control the origin of the photoluminescence in a single sample: passivation with hydrogen removes the defects, resulting in photoluminescence from quantum-confined states, but subsequent ultraviolet illumination reintroduces the defects, making them the origin of the light again

Scanning electron microscopy or optical coherence tomography for the evaluation of the glass fiber reinforced acrylic resin?

Aesthetics and strength are two major criteria for dental materials today. Objective: Easy evaluation of the bond between acrylic resin and glass fbers. Materials and methods: Pre-impregnated woven E-glass fbres (Stick® Net, Stick Tech Ltd Oy) and unidirectional pre-impregnated E-glass fbres (StickTM) were used to reinforce a conventional heat-curing denture base resin (Meliodent, Heraeus Kulzer GmbH&Co.KG) - ISO 1567:1999 (E). The samples were 12 Stick reinforced, 12 Stick net reinforced (Stick tech, Finland) and 12 were un-reinforced (control). Optical coherence tomography (OCT) investigation was performed in the Department of Applied Optics, School of Physical Sciences University of Kent, UK. SEM micrographs of the fractured specimens were taken using a SEM microscope (TESLA BS 343 A) in the Department of Materials Testing - ISIM Timisoara, Romania. The samples were in vacuum gold plated. Results: The SEM images were taken at 48× 55?, 120× 55?, 240× 55?, 480× 55? magnifcations for each sample. The OCT micrographs were taken at 670 nm and 1300 nm. The penetration depth is in micron range up to 2 mm. For each sample investigated at 670 nm, 61 de slices per stuck were taken and for each sample investigated at 1300 nm, minimum 100 slices per stuck were taken. Conclusions: Both methods are useful for the bond in between acrylic resin and glass fbers evaluation. SEM is more laborious than OCT which is able to obtain many precise images in steps up to 1 ?