63 research outputs found
Electron transport in gated InGaAs and InAsP quantum well wires in selectively-grown InP ridge structures
The purpose of this work is to fabricate ribbon-like InGaAs and InAsP wires
embedded in InP ridge structures and investigate their transport properties.
The InP ridge structures that contain the wires are selectively grown by
chemical beam epitaxy (CBE) on pre-patterned InP substrates. To optimize the
growth and micro-fabrication processes for electronic transport, we explore the
Ohmic contact resistance, the electron density, and the mobility as a function
of the wire width using standard transport and Shubnikov-de Haas measurements.
At low temperatures the ridge structures reveal reproducible mesoscopic
conductance fluctuations. We also fabricate ridge structures with submicron
gate electrodes that exhibit non-leaky gating and good pinch-off
characteristics acceptable for device operation. Using such wrap gate
electrodes, we demonstrate that the wires can be split to form quantum dots
evidenced by Coulomb blockade oscillations in transport measurements.Comment: 5 pages, 4 figures, additional references and improved Fig. 4c,
MSS-14 conference, submitted to Physica
The effect of VA mycorrhizal fungus (Glomus epigaeus) on the growth of two apple tree clones propagated in vitro
International audienc
The efficacy of student-centered instruction in supporting science learning
Transforming science learning through student-centered instruction that engages students in a variety of scientific practices is central to national science-teaching reform efforts. Our study employed a large-scale, randomized-cluster experimental design to compare the effects of student-centered and teacher-centered approaches on elementary school students' understanding of space-science concepts. Data included measures of student characteristics and learning and teacher characteristics and fidelity to the instructional approach. Results reveal that learning outcomes were higher for students enrolled in classrooms engaging in scientific practices through a student-centered approach; two moderators were identified. A statistical search for potential causal mechanisms for the observed outcomes uncovered two potential mediators: students'understanding of models and evidence and the self-efficacy of teachers
- …