Quantum confinement in Si and Ge nanostructures: Effect of crystallinity

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.Comment: arXiv admin note: substantial text overlap with arXiv:1111.201

Ion Beam Modification for Si Photonics

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

Ion Beam Modification for Si Photonics

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.Science, Irving K. Barber Faculty of (Okanagan)Non UBCComputer Science, Mathematics, Physics and Statistics, Department of (Okanagan)ReviewedFacult

Stopping cross sections of protons in Ti, TiO

Stopping cross sections of protons in Ti, Si, and TiO2 films in the energy range 50–170 keV were determined from medium energy ion scattering (MEIS) spectra by an iterative procedure. The energy loss of protons was investigated for pure Ti and Si films, deposited by molecular beam epitaxy (MBE) onto n-Si(100) and diamond-like carbon (DLC) substrates respectively. Consecutive annealing of Ti at 200 °C in O2 resulted in stoichiometric TiO2 thin-films. Thickness and composition of the films and the interfacial properties were determined using Rutherford backscattering spectroscopy (RBS), MEIS, and X-ray photoelectron spectroscopy (XPS). Calculated stopping cross sections of Ti, Si, and TiO2 in the range of energies were compared with the commonly used SRIM2003 values. For Ti and Si, SRIM2003 values appear to be overestimated over the entire energy range. The new stopping cross sections explain deviations from previously reported values for SrTiO3. We note that the stopping cross sections of O in a gaseous phase, used in Bragg’s rule calculations, cannot be applied for accurate quantitative ion beam analysis in solid compounds in the medium ion energy range

“MakerSpace in university science education: Learning the art of creating, innovating, and collaborating”

MakerSpace is an active learning, independent thinking, hands-on, and creative environment to facilitate practical solutions to open-ended problems. It involves product design through collaborative learning, enhances problem solving skills, innovation, and self-expression. It instills creativity and confidence in students to meet the challenges in their careers. This presentation will discuss the importance of providing a MakerSpace environment in Physics, show what is involved to run it, and describe how the learning outcomes are achieved. Typically, a MakerSpace employs specialist staff, contain 3D printers, computers, access to other specialized tools and offers facilities to conduct coursework, individual and collaborative projects. Our approach involves a variation, making use of existing faculty and staff support, a dedicated MakerSpace area, and incorporating learning within an undergraduate laboratory course that focuses on digital electronics and modern day physics problems. We will also share the experiences of our recent students. We view our MakerSpace to be a hub where undergraduates and graduates have the opportunity to collaborate on projects, develop cross-disciplinary skills along with sharing unique learning experiences. In future we anticipate enhancing the use of the MakerSpace by creating a new Advanced Industrial Physics Project course, in which participating students will be selected through the Western Science Internship program to work on projects related to selected industrial partners

MakerSpace environment in science education: Preparing for the challenges of an ever changing future

MakerSpaces provide hands-on experiences for active learning, collaboration, problem solving, innovation and self-expression. They instill creativity and confidence for meeting the challenges that students may face in their careers. Typically, MakerSpaces employ specialist staff, use 3D printers, computers, access to specialized tools and facilities to conduct coursework projects, individually or collaboratively. Our approach involves a variation, making use of existing faculty and staff support from the 2nd year Physics laboratory at the Department of Physics and Astronomy, a dedicated MakerSpace area and access to specialized machines (mills, lathes, water jet cutter, drill presses, etc). In the last two years students have been trained in using the MakerSpace for projects, as part of their lab experience. This has provided exposure to independent learning, being resourceful, engaging in teamwork, and learning to problem solve open-ended issues, as in an industry setting. We will share the outcomes from recent student experiences. In future we anticipate enhancing the use of the MakerSpace by creating a new Advanced Industrial Physics Project course, in which participating students will be selected through the Western Science Internship program to work on projects related to selected industrial partners. Participants in this hands-on workshop will use 3D graphical design software (Fusion360) collaboratively to design and fabricate a MakerSpace initiative. Participants will be in groups of two or more sharing and interacting on ideas to create and design a 3D geometry of a key chain tag, adding the letters WCSE and their initials, using Fusion360. Their product will be 3D printed by the end of the conference. Participants (max number 24) are encouraged to bring their own laptops with Fusion360 pre-installed. For a free version go to https://www.autodesk.com/products/fusion-360/students-teachers-educators Some computers with Fusion360 pre-installed will be available for participants

Optical Properties of Si Quantum Dots in Silica via an Implantation Mask

ABSTRACT We studied photoluminescent properties and luminescent decay dynamics in Si quantum dots (QDs) produced by Si implantation in SiO 2 , and their modification by the application of an implantation mask. Silicon quantum dots were prepared by ion implantation, followed by high temperature annealing leading to nanocrystal nucleation and growth. The mask was prepared by spin-coating silica microspheres to achieve laterally-selective implantation, to control QD size and separation. Transmission electron microscopy (TEM) images were obtained to verify the diameter of the quantum dots. We observe a noticeable peak shift and narrowing in the photoluminescence spectra with the application of the implantation mask. Observed maxima in the photoluminescence spectra are compared with a quantum field theoretical model using an infinite confining 1D potential for Si quantum dots. We comment on the role of excitation transfer by observing a change in the dispersion exponent of the luminescent decay dynamics due to the mask

Quantum confinement in Si and Ge nanostructures: Theory and experiment

The role of quantum confinement (QC) in Si and Ge nanostructures (NSs) including quantum dots, quantum wires, and quantum wells is assessed under a wide variety of fabrication methods in terms of both their structural and optical properties. Structural properties include interface states, defect states in a matrix material, and stress, all of which alter the electronic states and hence the measured optical properties. We demonstrate how variations in the fabrication method lead to differences in the NS properties, where the most relevant parameters for each type of fabrication method are highlighted. Si embedded in, or layered between, SiO2, and the role of the sub-oxide interface states embodies much of the discussion. Other matrix materials include Si3N4 and Al2O3. Si NSs exhibit a complicated optical spectrum, because the coupling between the interface states and the confined carriers manifests with varying magnitude depending on the dimension of confinement. Ge NSs do not produce well-defined luminescence due to confined carriers, because of the strong influence from oxygen vacancy defect states. Variations in Si and Ge NS properties are considered in terms of different theoretical models of QC (effective mass approximation, tight binding method, and pseudopotential method). For each theoretical model, we discuss the treatment of the relevant experimental parameters.Peer reviewed: YesNRC publication: Ye

Reticular Growth of Silicon Ridges: Random Walk in Two Dimensions

We report an observation of arrays of self-assembled Si ridges grown by vapor–liquid–solid mechanism in a molecular beam epitaxy (MBE) chamber. The growth experiments are conducted on Si(100) substrates using Au droplets as seeds for growth of Si ridges. We show that at a sufficiently low flux of Si atoms, gold droplets are propelled forward along two orthogonal ⟨011⟩ directions by the growing silicon ridges. The reticular growth closely resembles a self-avoiding random walk in two dimensions, as we confirmed by using Monte Carlo simulation. The result is a formation of a network of Si ridges with a topological complexity and connectivity that depends on the growth time as well as the starting diameter of the Au droplets. On the basis of our experimental results, we elaborate on the role of diffusion in the MBE growth of Si ridges