${\mathrm{Fe}}_{3}$${\mathrm{O}}_{4}$ films were grown on Si, $〈100〉$ and $〈110〉$ MgO, $〈111〉$ Mg${\mathrm{Al}}_{2}$${\mathrm{O}}_{4}$, $〈0001〉{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ by reactive sputter deposition. X-ray diffraction TEM studies of the MgO show they are uniformly strained epitaxial single crystal specimens. Conversion electron M\"ossbauer spectroscopy (CEMS) spectra for all substrates presence only stoichiometric phase, values hyperfine fields isomer shifts $A$ $B$ sites...

We examine ZnSnN2, a member of the class materials contemporarily termed “earth-abundant element semiconductors,” with an emphasis on evaluating its suitability for photovoltaic applications. It is predicted to crystallize in orthorhombic lattice energy gap 2 eV. Instead, using molecular beam epitaxy deposit high-purity, single crystal as well highly textured polycrystalline thin films, only monoclinic structure observed experimentally. Far from being detrimental, we demonstrate that cation...

We have examined the mechanisms of droplet formation and Bi incorporation during molecular beam epitaxy GaAsBi. consider role transition from group-V-rich to group-III-rich conditions, i.e., stoichiometry threshold, in presence Bi. For As-rich GaAsBi growth, acts as a surfactant, leading droplet-free films. films within 10% stoichiometric growth regime, surface Ga droplets are observed. However, for Ga-rich an anti-surfactant, inducing Ga-Bi formation. propose mechanism based upon...

We have investigated the effects of GaAs substrate misorientation on strain relaxation in InxGa1−xAs films and multilayers. Our calculations shear stresses due to misfit strain, resolved glide plane direction, reveal that α β 60° slip systems are influenced a nearly identical fashion, for all directions. Thus, classical models nucleation dislocations predict will not influence degree 〈110〉 asymmetry lattice-mismatched zincblende semiconductor films. Contrary these predictions, our...

Direct epitaxial growth of single-crystalline germanium (Ge) nanowires at room temperature has been performed through an electrodeposition process on conductive wafers immersed in aqueous bath. The crystal is based electrochemical liquid–liquid–solid (ec-LLS) involving the electroreduction dissolved GeO2(aq) water isolated liquid gallium (Ga) nanodroplet electrodes resting Ge or Si supports. were electrodeposited wafer scale (>10 cm2) using only common glassware and a digital potentiostat....

We conducted a study to examine how writing-to-learn assignment influenced student learning of polymer behavior. In particular, we examined the role specific content and rhetorical framework as well structured writing process including peer review revision. The student-generated was analyzed via content-directed rubric. Students' conceptual understanding stress–strain behavior gauged multitiered assessment. Finally, interviews were probe students' experiences during process. Results indicate...

Graphene has a great potential to replace silicon in prospective semiconductor industries due its outstanding electronic and transport properties; nonetheless, lack of energy bandgap is substantial limitation for practical applications. To date, straining graphene break lattice symmetry perhaps the most efficient approach toward realizing tunability graphene. However, weak deformation induced by uniaxial or in-plane shear strain, strained studies have yielded bandgaps <1 eV. In this work,...

We have investigated the vertical organization and evolution of 1-, 5-, 10-, 20-layer stacks molecular beam epitaxially grown self-assembled InAs/GaAs quantum dots using high resolution large-scale cross-sectional scanning tunneling microscopy. report results regarding dot sizes shapes, assembly vertically organized columns stacked dots. As number layers within a stack is increased, average spacing between decreases, corresponding become more uniform in size. The data also suggest that...

The authors demonstrate the formation of pn and nn+ junctions based on silicon supersaturated with sulfur (up to 0.46at.%) using a combination ion implantation pulsed laser melting. Silicon wafers were implanted at 200keV S+32 doses ranging from 1×1015to1×1016ions∕cm2 subsequently melted resolidified by homogenized excimer pulse. Above threshold fluence ∼1.4J∕cm2, process produces single crystal alloy, free extended defects, sharp junction between layer underlying substrate, located near...

We have investigated interdiffusion and surface segregation in molecular-beam-epitaxially-grown stacked self-assembled InAs/GaAs quantum dots. Using high-resolution cross-sectional scanning tunneling microscopy, we observe lateral variations the vertical positions of In atoms both wetting layers dot stacks. some regions, layer thickness is much less than height, while other immersed layer. Ga atom counting, obtain In–Ga 1/e lengths 1.25 2.8 nm, respectively. stacks, significant intermixing,...

This paper presents a pilot project using an educational robotics curriculum that was developed to enhance teaching of standard physics and math topics middle early high school students in inner-city schools New York City. The lessons are centered around the LEGO Mindstorms kit RoboLab graphical programming environment. project, testing two summer programs for students, conducted 2003 at locations Harlem, City, USA.

We compare the suitability of various magnesium-based liquid metal alloy ion sources (LMAISs) for scalable focused-ion-beam (FIB) implantation doping GaN. consider GaMg, MgSO4●7H2O, MgZn, AlMg, and AuMgSi alloys. Although issues oxidation (GaMg), decomposition (MgSO4●7H2O), excessive vapor pressure (MgZn AlMg) were encountered, LMAIS operating in a Wien-filtered FIB column emits all Mg isotopes singly doubly charged ionization states. discuss conditions to achieve &amp;lt;20 nm spot size...

AlScN is a new wide bandgap, high-k, ferroelectric material for RF, memory, and power applications. Successful integration of high quality with GaN in epitaxial layer stacks depends strongly on the ability to control lattice parameters surface or interface through growth. This study investigates molecular beam epitaxy growth transport properties AlScN/GaN multilayer heterostructures. Single Al$_{1-x}$Sc$_x$N/GaN heterostructures exhibited lattice-matched composition within $x$ = 0.09 -- 0.11...

Semiconductor quantum dots (QDs) are nanostructures that can enhance the performance of electronic devices due to their 3D quantization. Typically, heterovalent impurities, or dopants, added semiconducting QDs provide extra electrons and improve conductivity. Since each QD is expected contain a few parent dopants have been difficult locate. In this work, we investigate spatial distribution donors in epitaxial InAs/GaAs using local-electrode atom-probe tomography self-consistent...

We have investigated the evolution of structural and electronic properties highly mismatched InSb films, with thicknesses ranging from 0.1 to 1.5 μm. Atomic force microscopy, cross-sectional transmission electron high-resolution x-ray diffraction show that μm films are nearly fully relaxed consist partially coalesced islands, which apparently contain threading dislocations at their boundaries. As film thickness increases beyond 0.2 μm, island coalescence is complete residual strain reduced....

We have investigated nitrogen incorporation mechanisms in dilute nitride GaAsN alloys grown by plasma-assisted molecular-beam epitaxy. A comparison of nuclear reaction analysis and Rutherford backscattering spectrometry channeling nonchanneling conditions reveals significant composition-dependent N into nonsubstitutional sites, presumably as either N–N or N–As split interstitials. Furthermore, we identify the (2×1) reconstruction surface structure which leads to highest substitutional...

We have investigated the atomic-scale structure and electronic properties of GaN/GaAs superlattices produced by nitridation a molecular beam epitaxially grown GaAs surface. Using cross-sectional scanning tunneling microscopy (STM) spectroscopy, we show that nitrided layers are laterally inhomogeneous, consisting groups defects larger clusters. Analysis x-ray diffraction data in terms fractional area clusters (determined STM), reveals cluster lattice constant similar to bulk GaN. In addition,...

We have used rapid thermal annealing to investigate the influence of N interstitials on electronic properties GaAsN alloys. Nuclear reaction analysis reveals an annealing-induced decrease in interstitial concentration, while total composition remains constant. Corresponding signatures for reduced concentration are apparent Raman spectra. Following annealing, both room-T carrier n, and mobility increase. At higher measurement-Ts, a thermally activated increase n suggests presence trap near...

We report on the propagation of coherent acoustic wave packets in (001) surface oriented Al0.3Ga0.7As/GaAs heterostructure, generated through localized femtosecond photoexcitation GaAs. Transient structural changes both substrate and film are measured with picosecond time-resolved x-ray diffraction. The data indicate an elastic response consisting unipolar compression pulses a few hundred duration traveling along [001] directions that produced by predominately impulsive stress. transmission...

We have investigated the effects of various buffer layers on structural and electronic properties n-doped InSb films. find a significant decrease in room-temperature electron mobility films grown low-misfit GaSb buffers, increase high-misfit InAlSb or step-graded GaSb+InAlSb comparison with those directly GaAs. Plan-view transmission microscopy (TEM) indicates threading dislocation density for Cross-sectional TEM reveals role film/buffer interfaces nucleation (filtering) dislocations...

Coherent time-domain optical experiments on GaAs-AlAs superlattices reveal the existence of an unusually long-lived acoustic mode at $\ensuremath{\sim}0.6\text{ }\text{ }\mathrm{THz}$ which couples weakly to environment by evading sample boundaries. Classical as well quantum states that steer clear surfaces are generally shown occur in spectrum periodic structures, for most boundary conditions. These surface-avoiding waves associated with frequencies outside forbidden gaps and wave vectors...

Ultrafast laser excitation of an $\mathrm{InGaAs}/\mathrm{InAlAs}$ superlattice (SL) creates coherent folded acoustic phonons that subsequently leak into the bulk (InP) substrate. Upon transmission, become ``unfolded'' modes and acquire a wave vector much larger than light. We show time-resolved x-ray diffraction is sensitive to this large-wave in Comparison with dynamical simulations propagating strain supports our interpretation.