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An electron donor–acceptor complex strategy that enabled photoactivation of aryl chlorides has been reported with the toluene anion or tBuOK as the electron donor.

We report the use of halogen bonding (XB) for the generation of aryl radicals from aryl halides under blue light irradiation and applied it in radical generation/1,5-hydrogen-atom transfer/radical cyclization cascade reactions for the synthesis of oxindoles and isoindolinones. On the basis of experimental studies, we propose that DBU can serve as a suitable XB acceptor with aryl halides for the formation of a photoactive electron donor and acceptor complex.

Postoperative nausea and vomiting (PONV) remains a significant clinical problem for surgical patients. Amisulpride is a well-studied D2/D3 antagonist that has the potential to be used for preventing and treating PONV. Our aim was to assess the efficacy and safety of amisulpride for prevention and treatment of PONV through a systematic review and meta-analysis. A systematic literature search was performed using MEDLINE, EMBASE, PUBMED, clinicaltrials.gov, and the Cochrane Central Register of Controlled Trials from their inception to Feb 15th, 2019. The efficacy outcome was the incidence of complete response, defined as no emesis and no rescue antiemetic use in a 24-h period after study drug administration. The safety outcomes were the adverse effects associated with amisulpride. Five studies comprising 3243 patients met inclusion critieria. Compared with placebo, amisulpride showed a significantly improved incidence of complete response [relative risk (RR): 1.30; 95% confidence interval (CI): 1.20–1.41; P

The characterization and control of atomic substitution process is crucial in fabricating high-quality two-dimensional layered compound materials and tuning their physical properties. With intensity-voltage low energy electron microscopy (IV-LEEM), we found that the concentration of copper in the topmost copper silicide monolayer on Si (111) substrates varies gradually from 1.7 to 1.0 ML while preserving it's unique ′5 × 5′ incommensurate phase in a transition region as large as 1000 nm. This gradual variation of the copper concentration is due to the incomplete substitution of the Si with Cu, as revealed by atomic-resolved scanning tunneling microscopy with a tip that nicely resolved the ′5 × 5′ periodicity. Our experiments indicate that besides the widely-accepted phase of Cu2Si with both substitutional and interstitial Cu atoms, another type of precursor copper silicide CuSi3 with only interstitial Cu atoms also plays important roles in the substitutional diffusion and reaction processes during the formation of the topmost copper silicide monolayer. This precursor phase might exist in the growth of other two-dimensional layered materials with potential applications in integrated optoelectronics, spintronics or low dissipative devices.

The effects of space charge, aberrations and relativity on temporal compression are investigated for a compact spherical electrostatic capacitor (α-SDA). By employing the three-dimensional (3D) field simulation and the 3D space charge model based on numerical General Particle Tracer and SIMION, we map the compression efficiency for a wide range of initial beam size and single-pulse electron number and determine the optimum conditions of electron pulses for the most effective compression. The results demonstrate that both space charge effects and aberrations prevent the compression of electron pulses into the sub-ps region if the electron number and the beam size are not properly optimized. Our results suggest that α-SDA is an effective compression approach for electron pulses under the optimum conditions. It may serve as a potential key component in designing future time-resolved electron sources for electron diffraction and spectroscopy experiments.

The adsorption of di-meta-cyano azobenzene (DMC) cis and trans isomers on non-passivated and passivated Si (111) (7 × 7) surfaces is studied using density functional theory (DFT) calculations. Our results reveal that on the non-passivated surface the 12 Si adatoms are accessible to form chemical bonds with DMC molecules. Interestingly, the trans isomer forms two chemical bonds near the corner hole atom in Si (111) (7 × 7) surface, which is not observed in the widely studied metallic surfaces. The DMC isomers show significant structural distortion in the chemisorption case. The strong chemical bonds (and high bonding energy) could be detrimental to conformation switching between these two isomers under external stimuli. The physisorption case is also examined. Monte Carlo (MC) simulations with empirical force fields were employed to search about 106 different adsorption positions and DMC molecule orientations to identify the stable adsorption sites (up to six). The DFT-PBE and DFT-D2 calculations were then carried out to obtain the relaxed atomistic structures and accurate adsorption energy. We find that it is imperative to take van der Waals (vdW) interaction into account in DFT calculations. Our results show that the adsorption sites generally are encompassed by either the Si adatoms or the passivated H atoms, which could enhance the long-range dispersion interaction between DMC molecules and Si surfaces. The molecular structures of both isomers remain unchanged compared with gas phase. The obtained adsorption energy results ΔEads are moderate (0.2–0.8 eV). At some adsorption sites on the passivated surface, both isomers have similar moderate ΔEads (0.4–0.6 eV), implying promises of molecular switching that should be examined in experiments.

s We present experimental observations of high order phase contrast in aberration corrected low energy electron microscopy (AC-LEEM). Phase contrast produced by atomic steps on a Ag (111) surface exhibits prominent high order interference fringes, which have not been reported before. These phase contrast features depend upon defocus and incident electron energy, similar to the prominent first order fringes observed previously and in agreement with Fourier optics (FO) model predictions. The comparison of experimental results and FO model simulations demonstrates that fringe amplitudes are strongly affected at large defocus by the source divergence. This effect is exploited to quantitatively determine the divergence, 0.055 ± 0.005 mrad, of the field emission source in AC-LEEM under the imaging conditions used. Although the divergence determines the spatial coherence of the illumination in microscopy, it has not been possible to characterize this key instrumental parameter in LEEM before.

Composition-controlled growth of two-dimensional layered semiconductor heterostructures is crucially important for their applications in multifunctional integrated photonics and optoelectronics devices. Here, we report the realization of composition completely modulated layered semiconductor MoS2–MoS2(1–x)Se2x (0 < x < 1) lateral heterostructures via the controlled layer-selected atomic substitution of pregrown stacking MoS2, with a bilayer located at the center of a monolayer. Through controlling the reaction time, S at the monolayer MoS2 at the peripheral area can be selectively substituted by Se atoms at different levels, while the bilayer region at the center retains the original composition. Microstructure characterizations demonstrated the formation of lateral heterostructures with a sharp interface, with the composition at the monolayer area gradually modulated from MoS2 to MoSe2 and having high-quality crystallization at both the monolayer and the bilayer areas. Photoluminescence and Raman mapping...

A compact setup with a planar-cathode and grid-anode plus free field drift distance configuration (momentatron) has provided a new way to measure the transverse momentum and, hence, the emittance of the electron beam from a photocathode. This method has been used for analysis of the transverse momentum and emittance of the photoemitted electron beam from the photocathode in a stepwise manner during the fabrication process. The errors caused by the lensing effect from opening holes of the grid anode and misalignments caused by tilting and curving have been systematically analyzed. An analytical method has been developed, and a full three-dimensional electrostatic field particle tracing simulation has been performed to validate this measurement technique. The results show that a momentatron can provide an accurate measurement of transverse momentum and emittance of the photoemitted electrons. The reasonable experimental errors that may be encountered will only have a modest (few %) effect on the emittance measurement.

Spin Polarized Low Energy Electron Microscopy (SPLEEM) is a powerful tool to reveal the magnetic structure of ferromagnetic surfaces on the atomic depth scale level[1-3]. With aberration corrected LEEM and a high brightness spin polarized electron gun, high spatial resolution will provide more details for ultra-thin ferromagnetic film studies. This study reports the first realization of aberration corrected SPLEEM (AC-SPLEEM). The performance of the setup was tested on ferromagnetic Fe nanoscale islands on a W(110) single crystal, with spatial resolution of 3.3 nm in spin asymmetry images.

We report the discovery of room temperature in-plane ferroelectricity in van der Waals In2Se3 with β′ phase., Van der Waals (vdW) assembly of layered materials is a promising paradigm for creating electronic and optoelectronic devices with novel properties. Ferroelectricity in vdW layered materials could enable nonvolatile memory and low-power electronic and optoelectronic switches, but to date, few vdW ferroelectrics have been reported, and few in-plane vdW ferroelectrics are known. We report the discovery of in-plane ferroelectricity in a widely investigated vdW layered material, β′-In2Se3. The in-plane ferroelectricity is strongly tied to the formation of one-dimensional superstructures aligning along one of the threefold rotational symmetric directions of the hexagonal lattice in the c plane. Surprisingly, the superstructures and ferroelectricity are stable to 200°C in both bulk and thin exfoliated layers of In2Se3. Because of the in-plane nature of ferroelectricity, the domains exhibit a strong linear dichroism, enabling novel polarization-dependent optical properties.

Low energy electron microscopy and photoemission electron microscopy (LEEM/PEEM), as powerful in-situ surface-sensitive electron microscopy, find wide applications in surface physics, chemistry and catalysis. The high reflectivity of incident low-energy electrons (0–100 eV), allows it to image the surface structures in the topmost few atomic layers within less than one second, while the sample can be heated up to 1200 ℃ in real time which is potentially very useful in metallurgy and materials fields. A unique three-prism aberration correction (ac-) LEEM was commissioned successfully in Chongqing University, with a lateral resolution below 2 nm. A multiple gas source in the ac-LEEM system was installed as well, which allowed us to observe chemical reactions of nanoscale mineral powders on metallic substrates. In this paper, the latest results on the applications of this three-prism ac-LEEM on oxidation and reduction processes on copper and iron polycrystalline surfaces are demonstrated.

The numerical simulation of elastic wave propagation through a grating in a homogeneous medium shows the characteristic Talbot self-imaging effect. The size of the imaging and patterns can be controlled by changing the periodicity of grating and wavelength, respectively. It provides a novel route to modulate elastic wave distributions in solids with inclusions. Time dependent simulation suggests a long-distance elastic-wave-based interconnection in solids. An interferometer based on the elastic wave Talbot effect is discussed.

We describe the design and commissioning of a novel aberration-corrected low energy electron microscope (AC-LEEM). A third magnetic prism array (MPA) is added to the standard AC-LEEM with two prism arrays, allowing the incorporation of an ultrafast spin-polarized electron source alongside the standard cold field emission electron source, without degrading spatial resolution. The high degree of symmetries of the AC-LEEM are utilized while we design the electron optics of the ultrafast spin-polarized electron source, so as to minimize the deleterious effect of time broadening, while maintaining full control of electron spin. A spatial resolution of 2nm and temporal resolution of 10ps (ps) are expected in the future time resolved aberration-corrected spin-polarized LEEM (TR-AC-SPLEEM). The commissioning of the three-prism AC-LEEM has been successfully finished with the cold field emission source, with a spatial resolution below 2nm.

Using in situ surface electron microscopy, we show that the surface chemical potential of GaAs (001), and hence the surface phase, can be systematically controlled by varying temperature with liquid Ga droplets present as Ga reservoirs. With decreasing temperature, the surface approaches equilibrium with liquid Ga. This provides access to a regime where we find phases ultrarich in Ga, extending the range of surface phases available in this technologically important system. The same behavior is expected to occur for similar binary or multicomponent semiconductors such as InGaAs.

We extend the theory of Laplacian image contrast in mirror electron microscopy (MEM) to the case where the sample is illuminated by a parallel, collimated beam. This popular imaging geometry corresponds to a modern low energy electron microscope equipped with a magnetic objective lens. We show that within the constraints of the relevant approximations; the results for parallel illumination differ only negligibly from diverging MEM specimen illumination conditions.

Different cell line with increased thioredoxin-1 (Trx-1) showed a decreased or increased sensitivity to cell killing by cisplatin. Recently, several studies found that the subcellular localization of Trx-1 is closely associated with its functions. In this study, we explored the association of the nuclear Trx-1 with the cisplatin-mediated apoptosis of breast cancer cells MCF-7. Firstly, we found that higher total Trx-1 accompanied by no change of nuclear Trx-1 can not influence apoptosis induced by cisplatin in MCF-7 cells transferred with Trx-1 cDNA. Secondly, higher nuclear Trx-1 accompanied by no change of total Trx-1 can protect cells from apoptosis induced by cisplatin. Thirdly, high nuclear Trx-1 involves in the cisplatin-resistance in cisplatin-resistive cells. Meanwhile, we found that the mRNA level of p53 is closely correlated with the level of nuclear Trx-1. In summary, we concluded that the nuclear Trx-1 is required to resist apoptosis of MCF-7 cells induced by cisplatin, probably through up-regulating the anti-apoptotic gene, p53.

The kinetic regime of step motion on the Si(111) (1 × 1) surface is determined from observations of island decay with low-energy electron microscopy (LEEM). We have investigated the island decay on the tops of mounds fabricated by a photolithographic method. Prefabricated mounds serve as controllable and reproducible island sources and platforms for decay. Island area during decay exhibits the expected power-law dependence on time, with exponent, a, that is indicative of the kinetic regime. In order to overcome the basic problem of realizing the thermodynamic limit of island decay on an infinite terrace, the power-law decay exponent is extrapolated to vanishing island (r) - to - terrace (R) radius ratio, r/R = 0. The dependence of a upon r/R suggests that island decay kinetics is intermediate between the diffusion-limited (DL) and attachment/detachment-limited (ADL) regimes.

Daintain is a 17-kDa polypeptide originally purified from porcine intestine. This polypeptide is associated with insulin secretion and inflammatory responses. Daintain is highly similar in amino acid sequence to allograft inflammatory factor-1 (AIF-1). Here we report the preparation and identification of monoclonal antibodies (MAbs) against daintain. To enhance its immunogenicity, daintain was coupled to carrier protein bovine serum albumin (BSA) by a two-step glutaraldehyde method. Using conventional procedures, we obtained four stable hybridoma cell lines that can produce and secret anti-daintain MAbs. We further analyzed their isotypes, titer, and affinity, and found that those MAbs belong to the G1 subclass with kappa light chains. The MAbs were capable of recognizing daintain as determined by Western blotting. The produced MAbs will be a useful tool for further investigation of daintain functions in organisms.

Droplet epitaxy of GaAs is studied in real time using in situ surface electron microscopy. The resulting movies motivate a theoretical model for quantum ring formation which can explain the origin of nanoscale features such as double rings observed under a variety of experimental conditions. Inner rings correspond to GaAs deposition at the droplet edge, while outer rings result from the reaction of Ga and As atoms diffusing along the surface. The observed variety of morphologies primarily reflects relative changes in the outer rings with temperature and As flux.

Single-crystal Fe films of 4 to 33 monolayers (ML) on GaAs (100) prepared by molecular-beam epitaxy were studied by ferromagnetic resonance (FMR). The evolution of both in-plane and out-of-plane anisotropies was observed. The FMR data show a predominant in-plane uniaxial magnetic anisotropy in the films with the thickness t less than 12.7 ML, with an easy axis along the 〈11_0〉 direction. An in-plane fourfold anisotropy due to cubic magnetocrystalline anisotropy starts to appear and coexists with uniaxial magnetic anisotropy when t=8.4 ML, and increases with increasing film thickness. For t=33 ML, the cubic anisotropy constant K1 reaches 28.2×104 erg/cm3, which is 60% of the value for bulk bcc Fe. A strong perpendicular anisotropy in the ultrathin Fe films was observed. For t=4 ML, the perpendicular anisotropy constant is as high as 14.6×106 erg/cm3. It decreases with increasing the thickness t and reaches about 2.1×106 erg/cm3 for 33 ML, while a small fourth-order perpendicular anisotropy appears and incr...

To explore the efficacy and safety of tandospirone for adolescents with anxiety disorder.In this multicenter open-label 12-week study, a total of 169 adolescents met the criteria of DSM-IV for anxiety disorder were treated with flexible dose of tandospirone. The effects and safety of treatment were assessed by the Hamilton anxiety scale (HAMA), state-trait anxiety inventory (STAI), clinical global impression (CGI) and side effects at baseline and Weeks 2, 4, 8 and 12.In 151 cases completing the 12-week treatment, the scores of HAMA decreased by 18% ± 12%, 38% ± 16%, 54% ± 20% and 63% ± 17% at Weeks 2, 4, 8 and 12. Significant reductions in HAMA scores were seen at Weeks 2-12 (P0.01) and marked improvement appeared in 81.5% cases at Week 12 (reduction rate of HAMA: 50%). At Week 12, the HAMD(17) scores were markedly lower versus baseline (7 ± 2 vs 13 ± 3, P0.01). Adverse effect of tandospirone was scarcely found (9.9%).Tandospirone is an effective and safe anti-anxiety drug for adolescents.

We propose a spin-polarized Talbot effect for an electron beam scattered from a grating of magnetic nanostructures. Existing periodic magnetic nanostructures can be used in conjunction with electron-beam illumination to create a spin-polarized replica of the transversely periodic exit surface beam a Talbot length away. Experiments have been proposed to verify the effect in a two-dimensional electron gas and an atomically flat surface by spin-polarized scanning probe microscopy. This effect provides a new route to modulate electron spin distributions in two-dimensional space.

Coalescence of droplets during reactive wetting is investigated for the liquid Ga/GaAs(001) system. In situmirror electron microscopy reveals that coalescence predominantly involves the motion of one reactive droplet relative to the other. This behaviour differs significantly from coalescence in non-reactive systems and is associated with contact line pinning at a ridge/etch pit edge which is identified using atomic force microscopy and selective etching. A simple geometrical model is presented to describe the pinning.

Epitaxial growth of Ni thin films on GaAs(0 0 1) and their magnetic property have been investigated using reflection high energy electron diffraction and magneto-optical Kerr effect. The result shows that a body-centered-cubic (BCC) phase of Ni which does not exist in nature can grow epitaxially up to 2.5 nm on the GaAs(0 0 1) substrate, and it is determined to be ferromagnetic showing a four-fold in-plane magnetic anisotropy with the easy axes along the 〈1 0 0〉 directions.

We apply Lloyd's mirror photoemission electron microscopy (PEEM) to study the surface shape of Ga droplets on GaAs(001). An unusual rectangular-based droplet shape is identified and the contact angle is determined in situ. It is shown that quenching does not appreciably affect droplet shape and ex situ measurements of the contact angle by atomic force microscopy are in good agreement with Lloyd's mirror PEEM. Extension of Lloyd's mirror technique to reconstruct general three-dimensional (3D) surface shapes and the potential use of synchrotron radiation to improve vertical resolution is discussed.

It was realized at the very beginning of the development of the quantum theory of condensed matter that, although solids are composed of atoms, they cannot be described using atomic properties only. The reason lies in the collective phenomena that appears in solids. They should undoubtedly be taken into account when excitations are studied. Collective excitations in solids can be described by their representative quasiparticles. For instance, the collective modes of the latticevibrations arewell described by phonons. Phonons are characterized by their dispersion relation, which links the energies of the excitations to their propagating wave vectors. In magnetic solids there is another kind of collective excitation that originates from the precession of the atomic spins around their equilibrium position. Such excitations have a totally different nature and are called spin waves or magnons. Spin waves are also characterized by their dispersion relation and more importantly they carry a spin of 1 @. The above mentioned

We discuss a new interpretation of mirror electron microscopy (MEM) images, whereby electric field distortions caused by surface topography and/or potential variations are sufficiently large to create caustics in the image contrast. Using a ray-based trajectory method, we consider how a family of rays overlaps to create caustics in the vicinity of the imaging plane of the magnetic objective lens. Such image caustics contain useful information on the surface topography and/or potential, and can be directly related to surface features. Specifically we show how a through-focus series of MEM images can be used to extract the contact angle of a Ga droplet on a GaAs (001) surface.

When GaAs is heated in vacuum, it decomposes into Ga and As as it evaporates. Real-time in situ surface electron microscopy reveals striking bursts of “daughter” droplet nucleation and growth when coalescence of large “parent” droplets exposes nonplanar surface regions. We analyze the behavior, predicting a morphology-dependent congruent evaporation temperature. Based on this we propose a new approach for the self-assembly and positioning of quantum structures via droplet epitaxy, which we demonstrate at the proof-of-concept level.

High-temperature annealing of gallium arsenide in vacuum causes excess evaporation of arsenic, with accumulation of gallium as liquid droplets on the surface. Using real-time in situ surface electron microscopy, we found that these droplets spontaneously run across the crystal surface. Running droplets have been seen in many systems, but they typically require special surface preparation or gradient forces. In contrast, we show that noncongruent evaporation automatically provides a driving force for running droplets. The motion is predicted and observed to slow and stop near a characteristic temperature, with the speed increasing both below and above this temperature. The same behavior is expected to occur during the evaporation of similar III-V semiconductors such as indium arsenide.

We report the first observation of high wave vector magnon excitations in a ferromagnetic monolayer. Using spin-polarized electron energy loss spectroscopy, we observed the magnon dispersion in one atomic layer (ML) of Fe on W(110) at 120 K. The magnon energies are small in comparison to the bulk and surface Fe(110) excitations. We find an exchange parameter and magnetic anisotropy similar to that from static measurements. Our results are in sharp contrast to theoretical calculations, indicating that the present understanding of magnetism of the ML Fe requires considerable revision.

Thioredoxin (Trx) is a member of the thioredoxin protein family and has a conserved catalytic domain (-Trp-Cys-Gly-Pro-Cys-Lys-) with reduction/oxidation (redox) activity. There are two main members in this family, Trx-1, a cytosolic and nuclear form, and Trx -2, a mitochondrial form. Trx-1 is a 104 amino acid multifunctional protein that has been extensively studied. Here we report the preparation of monoclonal antibodies (MAb) against recombinant human Trx-1(hTrx). To enhance its immunogenicity, Trx-1 was coupled to carrier protein bovine serum albumin by a two-step glutaraldehyde method. Using conventional procedures, we prepared three stable hybridoma cell lines that can produce and secret anti-Trx MAbs. We further analyzed their isotypes, titer, and affinity and found that those MAbs belong to the G1 subclass with kappa light chains, respectively. The MAbs were capable of recognizing hTrx-1, as determined by Western blotting.

Monoclonal antibodies (MAbs) against insulin are useful for insulin assays because of their specificity and plentiful supply. We have produced four monoclonal cell strains stably secreting the monoclonal antibodies against insulin; further established subpopulation, titer, affinity; and identified the antibodies as being of subclass IgG(2b)(kappa), one strain, or IgG(1)(kappa), three strains. The smallest detectable level of human insulin by ELISA using this IgG(1) was 1.25 microg/L. The monoclonal antibodies have been used for analyzing insulin content from the sera of type 2 diabetes patients and normal subjects.

We present the first surface spin-wave (SW) dispersion measurements up to the surface Brillouin zone boundary of a two monolayer Fe film on W(110) by using spin-polarized electron energy loss spectroscopy. Pronounced features of SW peaks are observed in the spectra at room temperature. We found that the SW energies in the Fe film are strongly reduced compared to spin waves in bulk Fe and to theoretical predictions. Our results suggest that this reduction is caused by the reduction of exchange interaction within the 2 ML Fe on W(110) as compared to bulk Fe.

We present an experimental study of high-wave-vector spin waves in 8 monolayer (ML) thick hexagonal closed-packed (hcp) Co films performed by spin-polarized electron energy loss spectroscopy (SPEELS). Using inelastic electron scattering, we were able to follow the spin wave dispersion up to the surface Brillouin zone boundary ((K) over bar), i.e., up to a wave-vector transfer of 1.64 A(-1). The spin wave dispersion was found to agree surprisingly well with the dispersion relation of a surface spin wave calculated by a nearest-neighbor Heisenberg model. From this description, we obtain a value for the product of the exchange coupling constant (J) and the magnetic moment (S) of JS=14.8 +/- 1 meV. This value, within the error bar, is identical to our results obtained on thin fcc Co films on Cu(001). We also find that the spin wave features measured by SPEELS at high-wave-vectors are strongly broadened. This is in agreement with expectations from nonadiabatic theoretical descriptions in which the broadening is ascribed to a strong damping of these high-wave-vectors spin waves by Stoner excitations. Similar to the observations in previously studied systems, we also observe a strong dependence of the measured spin wave intensities on the kinetic energy of the incident electrons (E-kin). Highest spin wave intensities were found for low kinetic energies (E-kin< 10 eV).

The capabilities of spin polarized electron energy loss spectroscopy are demonstrated with results obtained on ultrathin Co-films. Co is investigated in two crystalline phases, the fcc- and the hcp-phase. In both cases, the spin-wave signals for wave-vector transfers up to the surface Brillouin zone for film thickness of only a few atomic layers are measured. In both systems, a pronounced dispersion of the spin waves is found. The measured data is in good agreement with the calculated dispersions of surface spin waves within a nearest neighbor Heisenberg model. From the fits of the calculated to the measured dispersions, a value for the product of the exchange coupling constant and the magnetic moment (JS) of about 15 meV for both crystalline phases is obtained. Due to the similar values of JS, the spin-wave energies are similar for wave-vector transfers much smaller than the surface Brillouin zone boundary. For high wave-vector transfers, the spin-wave energies differ significantly reflecting the larger surface Brillouin zone for the hcp Co-lattice caused by the different arrangement of atoms at the surface.

The body-centered-cubic (bcc) phase of Ni, which does not exist in nature, has been achieved as a thin film on GaAs(001) at 170 K via molecular beam epitaxy. The bcc Ni is ferromagnetic with a Curie temperature of 456 K and possesses a magnetic moment of 0.52 +/- 0.08 mu(B)/atom. The cubic magnetocrystalline anisotropy of bcc Ni is determined to be +4.0x10(5) ergs center dot cm(-3), as opposed to -5.7x10(4) ergs center dot cm(-3) for the naturally occurring face-centered-cubic (fcc) Ni. This sharp contrast in the magnetic anisotropy is attributed to the different electronic band structures between bcc Ni and fcc Ni, which are determined using angle-resolved photoemission with synchrotron radiation.

Kinetic limitations related to the Schwoebel-Ehrlich (SE) diffusion barrier are examined in two-(2D) and three-dimensional (3D) growth. It is shown that the realization of step instabilities in 2D growth, possibly caused by the SE barrier, may be hindered by other factors such as step permeability and the relative importance of diffusion and step attachment. Growth shapes of Ag crystallites are also determined that reveal the impact of kinetic limitations. Dramatic changes of growth shape caused by In codeposition suggest that surfactants can modify the 3D SE barrier.

A maskless method of electron beam lithography is described which uses the reflection of an electron beam from an electrostatic mirror to produce caustics in the demagnified image projected onto a resist–coated wafer. By varying the electron optics, e.g. via objective lens defocus, both the morphology and dimensions of the caustic features may be controlled, producing a range of bright and tightly focused projected features. The method is illustrated for line and fold caustics and is complementary to other methods of reflective electron beam lithography.

The displacive adsorption of As on 1 × 1 Si(111) is examined using surface electron microscopy. High temperature adsorption experiments are used to reduce the As chemical potential and identify regions of enhanced As incorporation in the vicinity of steps. This is explained by a reduction in tensile surface stress associated with 1 × 1 As:Si(111). Cycling the incident As flux on and off creates surface roughening via respective displacive adsorption and evaporation of As. This roughness facilitates increased 1 × 1 As:Si(111) coverage during As deposition due to surface stress relief at steps.

High wave-vector magnon excitations in ferromagnetic Fe monolayer and double-layer grown on W(110) are investigated using spin-polarized electron energy loss spectroscopy. The magnon dispersion relation is obtained up to the Brillouin zone boundary. A direct comparison among different systems shows that the magnons in the Fe monolayer are extremely soft and are even softer than the acoustic surface mode of Fe(110). By measuring the spectra in both energy loss and gain regions on a double-layer Fe film at room temperature and by reversing the sample magnetization, it is demonstrated that the magnon dispersion is asymmetric with respect to the sign of the wave-vector. The asymmetric dispersion relation is attributed to the degeneracy breaking of the magnons due to the presence of the Dzyaloshinskii-Moriya interaction.

The time evolution of the Ga droplet size distribution is measured by in situ surface electron microscopy during Langmuir evaporation of GaAs. With a minimum of complexity, we are able to reproduce and explain the major features of the droplet size distribution by a simple Monte Carlo model. Guided by the experiment, the model includes droplet formation in response to coalescence events.

The congruent evaporation temperature Tc is a fundamental surface characteristic of GaAs and similar compounds. Above Tc the rate of As evaporation exceeds that of Ga during Langmuir (free) evaporation into a vacuum. However, during molecular beam epitaxy (MBE) there is generally an external As flux F incident on the surface. Here we show that this flux directly controls Tc. We introduce a sensitive approach to measure Tc based on Ga droplet stability, and determine the dependence of Tc on F. This dependence is explained by a simple model for evaporation in the presence of external flux. The capability of manipulating Tc via changing F offers a means of controlling congruent evaporation with relevance to MBE, surface preparation methods, and droplet epitaxy.

Molecular dynamics (MD) simulations were used to investigate the mechanical strain energy release of a bent single wall carbon nanotube (CNT) and its mechanical collision with a circular graphene sheet that is fixed at its edges. The MD simulations show that the CNT is able to store a vast amount of mechanical strain energy because of the formation of kinks on its wall at the regions of maximum curvature. The sudden release of the strain energy upon releasing the bent CNT can cause its tip to approach a speed of 7000 m/s. Even with such a high speed collision with a monolayer graphene sheet, the CNT and the monolayer graphene sheet remain completely intact and do not suffer any damage. The instantaneous average impact pressure between the CNT and the graphene sheet is calculated to be in the range of 1-10 GPa for different temperatures and aspect ratios of the CNT. These results indicate the promising application of a CNT and a graphene sheet as a nanoknife and a nanocutting board, respectively, for nanocleavage processes such as sequence-specific DNA cleaving processes.

Kinetically limited growth shapes of Ag crystallites on the Si(111) surface have been studied by low energy electron microscopy and diffraction. Triangular hexagons are predominant with the (111) plane parallel to the substrate. The major side facets are determined by facet diffraction spot analysis to be {100}. Absence of facet diffraction spots from the minor side facets suggests that they may be the more steeply inclined {111} or {121} orientations. Preliminary evidence is also obtained that codeposition of In causes the steeper side facets to dominate the growth shape.