Dry Etched III-V Semiconductors for Nanoelectronics

The purpose of this work was to try to identify the amount, degree and physical nature of the damage caused on both the surface and sidewalls of reactive ion etched GaAs and AlGaAs nanostructures using a variety of complimentary characterisation techniques, and to develop low damage high resolution dry etch processes for GaAs and AlGaAs. The gases investigated included SiCl4, CH4/H2 and CCl2F2/He. Two new methods of etching GaAs anisotropically by magnetron radio-frequency and electron cyclotron resonance radio-frequency reactive ion etching employing CCl2F2/He, and the use of a novel gas mixture CH4/H2 to reactive ion etch GaAs in the conventional radio-frequency mode were developed. It was found to be important to distinguish between surface and sidewall damage, and both were characterised using electrical, optical as well as analytical techniques. In particular, two novel processes were developed using high resolution fabrication techniques for the construction of sidewall Schottky diodes and electron transparent thin wire specimens to allow the amount of sidewall damage to be estimated and its nature to be realised through diode characteristic measurements and transmission electron microscopy analysis. To investigate the surface damage caused after etching, techniques such as Schottky diode performance, integrated band-gap photoluminescence, Raman scattering and X-ray photoelectron spectroscopy were employed; and for the first time, the usefulness of specular X-ray reflectivity for the identification of surface damage was explored. Sidewall damage was examined using room and low temperature conductivity, and low temperature magnetoconductance of n+ GaAs quantum wires, sidewall Schottky diode characteristics and transmission electron microscopy on thin wire specimens. The dependence of surface and sidewall damage on etch time and etch power was also studied

Reflections on Developing a Cross-Institutional Team

Today’s educators need to develop the knowledge, skills, and disposition to support all students in deeper learning. Educator Preparation Laboratory (EdPrepLab) works to strengthen educator preparation in the United States by building the collaborative capacity of preparation programs, school districts, and state policymakers. Through cross-programmatic sharing of innovative practices, including models and artifacts of educator preparation practice, EdPrepLab’s network of preparation programs helps build leadership and high-quality practice through collaboration, research, and documentation.https://educate.bankstreet.edu/gse/1001/thumbnail.jp

Reflections on Developing a Cross-Institutional Inquiry Project

Jennifer Robinson, Executive Director of the Center for Pedagogy at Montclair State University and Rebecca Cheung, Director of the Principal Leadership Institute at the University of California, Berkeley, are helping to lead a collaborative inquiry group comprised of three different institutions: Montclair State University, University of California, Los Angeles (UCLA), and University of California, Berkeley (UC Berkeley). This brief captures protocols and processes they used to support effective collaboration in the design of their inquiry project proposal.https://educate.bankstreet.edu/gse/1002/thumbnail.jp

Adapting a Critical Friends Consultancy to a Virtual Environment

This inquiry brief explores how a cross-institutional consultancy project examining anti-racist teacher and leader preparation adapted to a virtual environment amid COVID-19.https://educate.bankstreet.edu/gse/1006/thumbnail.jp

Performance Assessment of Aspiring School Leaders Grounded in an Epistemology of Practice: A Case Study

There is increasing interest in the field of leadership preparation about the opportunities that robust performance assessments may provide to capture and evaluate the complexity of school administrators’ work. Heretofore, the conversation about administrator performance assessment in leadership preparation has mainly centered on the development and impact of large statewide assessments that grow out of a Cartesian epistemology of individual knowledge possession, in which individuals must demonstrate mastery of a set of static knowledge and skills. We analyzed the characteristics of a performance assessment system that deliberately accounts for the organizational complexity of practice and knowledge generation in its design. Candidates are assessed by faculty and coaches on state-wide and program standards, but instead of producing evidence of their practice as individuals, they are assessed within simulated practice-based scenarios that require them to both draw on their extant individual and collective knowledge and build and act on new knowledge as they move through the simulation. Our analysis enables us to dimensionalize issues related to state mandated performance assessments and their implementation by preparation programs.https://educate.bankstreet.edu/faculty-staff/1051/thumbnail.jp

Delamination of polyimide in hydrofluoric acid

Wet etching is a critical fabrication step for the mass production of micro and nanoelectronic devices. However, when an extremely corrosive acid such as hydrofluoric (HF) acid are used during etching, an undesirable damage might occur if the device includes a material that is not compatible with the acid. Polyimide thin films can serve as sacrificial/structural layers to fabricate freestanding or flexible devices. The importance of polyimide in microelectronics is due to its relatively low stress and compatibility with standard micromachining processes. In this work, a fast delamination process of a 4-μm-thin film of polyimide from a silicon substrate has been demonstrated. The films’ detachment has been performed using a wet-based etchant of HF acid. Specifically, the effect of HF concentration on the delamination time required to detach the polyimide film from the substrate has been investigated. This study is intended to provide the information on the compatibility of using polyimide films with HF, which can help in the design and fabrication of polyimide-based devices

PDMS-ZnO Piezoelectric Nanocomposites for Pressure Sensors

The addition of piezoelectric zinc oxide (ZnO) fillers into a flexible polymer matrix has emerged as potential piezocomposite materials that can be used for applications such as energy harvesters and pressure sensors. A simple approach for the fabrication of PDMS-ZnO piezoelectric nanocomposites based on two ZnO fillers: nanoparticles (NP) and nanoflowers (NF) is presented in this paper. The effect of the ZnO fillers’ geometry and size on the thermal, mechanical and piezoelectric properties is discussed. The sensors were fabricated in a sandwich-like structure using aluminium (Al) thin films as top and bottom electrodes. Piezocomposites at a concentration of 10% w/w showed good flexibility, generating a piezoelectric response under compression force. The NF piezocomposites showed the highest piezoelectric response compared to the NP piezocomposites due to their geometric connectivity. The piezoelectric compound NF generated 4.2 V while the NP generated 1.86 V under around 36 kPa pressure. The data also show that the generated voltage increases with increasing applied force regardless of the type of filler

Mechanical Properties and Applications of Two-dimensional Materials

Two-dimensional (2D) materials have attracted increasing attention recently due to their extraordinarily different material properties compared with conventional bulk materials. The 2D materials possess ultralow weight, high Young’s modulus, high strength, outstanding carrier mobility, as well as high anisotropy between the in-plane and out-of-plane mechanical properties. The nearby atoms in the same plane of layered 2D materials are connected via covalent bonding, while the interlayers are stacked together via weak van der Waals interactions. In this article, we review the in-plane mechanical properties (including the in-plane Young’s modulus, pretension, breaking strength/strain) and out-of-plane mechanical properties (including the perpendicular-to-plane Young’s modulus, shear force constant, and shear strength) of different 2D materials, varying from conductors, semiconductors, to insulators. The different fabrication methods for suspended 2D material structures are presented. The experimental methods and principles for mechanical properties characterization are reviewed. A comparison of the mechanical properties among different 2D materials is summarized. Furthermore, electrical output change as a result of mechanical deformation (piezoresistive and piezoelectric effects) is introduced briefly. By exploiting the unique mechanical and mechanoelectric transduction properties, 2D materials can be used in wide-ranging applications, including flexible electronics, strain sensors, nanogenerators, and innovative nanoelectromechanical systems (NEMS)