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Linear arrays of high-quality quantum dots (QD) integrated in Si are an ideal platform in exploring the manipulation and transmission of quantum information. Understanding QD self-organization mechanisms on substrates compatible with Si technology is therefore of great practical importance. Here we demonstrate the epitaxial growth of linear arrays of InAs and InGaAs QDs from As2 and In molecular beams on bare and GaAs-coated Si(0 0 1) substrates, patterned by high-resolution laser interference nanolithography. Atomic force microscopy, in combination with high-resolution scanning and transmission electron microscopies, show that these arrays exhibit an improvement in growth selectivity, lateral order and size uniformity of the QDs when a pseudomorphic 1 nm-thick GaAs buffer layer is grown prior to InAs deposition. In addition, preferential nucleation of InxGa1-xAs QDs along the 〈1 1 0〉 -oriented edges of the nanostructured GaAs-on-Si(0 0 1) substrate results from In adatom migration from (1 1 1) to (0 0 1) nanofacets and the erosion of the wetting and buffer layers caused by the Ga-In intermixing at the step edge during the Stranski-Krastanov transition. These are key elements in the formation of linear arrays of coherent QDs, which differ in morphology and structure from those obtained on both GaAs(0 0 1) and Si(0 0 1) planar surfaces

The efficiency of quantum dot (QD) to convert sunlight to electricity is based on the principle of multiple exciton generation (MEG), such that a single photon produces more than one electron-hole pair. The zero-dimensional structure of QD leads to spatial confinement of electronic energies. The energy levels of electrons in QDs depends on their size – the smaller the quantum dot, the greater the amount of energy required to excite electrons to the next level. This allows quantum dots to be tuned to absorb different wavelengths of light just by changing their size. The tuning of band in Quantum dot (QD) structures offers potential applications in the field of photovoltaics and optoelectronic devices. In this paper, we have presented the finite element method simulation results of solar cell based on InP pyramidal QDs in an InGaP matrix. We have found the ground state energies using time independent Schrodinger equation (SE) with effective mass approximation. We show that ground state energies are affected by the dimension of the QDs as well as by the presence of a quantum well wetting layer associated with the QDs.

The efficiency of Quantum Dots (QDs) devices, is strongly related to their distribution, density and size, and shape in a QD array. The small size of the QD structure leads to a three-dimensional confinement of the electronic energies. The energy levels of electrons in QDs depends on their size – the smaller the quantum dot, the greater the amount of energy required to give electrons transitions to the next level. In this paper, we report the simulation results of pyramidal InAs/GaAs QDs coupled to Wetting Layer (WL). To investigate the effects of the InAs/GaAs QDs size on the electronic states and the transition energy. In the first part, we calculate the strain distribution to find the band edges, while the second one concerns the variation of the electronic transition energy as a function of quantum dots size by solving the stationary Schrodinger equation. This work shows clearly that the structural properties of QDs have strong effects on optoelectronic properties devices based on these nanostructures.

Quantum entropy under spontaneously generated coherence (SGC) was modeled and studied in a double quantum dot (DQD) structure. This system becomes after including the wetting layer (WL) as a ladder-plus-Y- system. The results show that the high probe field under high SGC can give good entanglement between states of the DQD system. Under the high SGC component, the optical pump was more efficient than the probe signal in increasing entanglement. The application of optical fields into WL reduces quantum entropy.

The dewetting process is crucial for several applications in nanotechnology. Even though not all dewetting phenomena are fully understood yet, especially regarding metallic fluids, it is clear that the formation of nanometre-sized particles, droplets, and clusters as well as their movement are strongly linked to their wetting behaviour. For this reason, the thermodynamic stability of thin metal layers (0.1–100 nm) with respect to their free energy is examined here. The decisive factor for the theoretical considerations is the interfacial energy. In order to achieve a better understanding of the interfacial interactions, three different models for estimating the interfacial energy are presented here: (i) fully theoretical, (ii) empirical, and (iii) semi-empirical models. The formation of nanometre-sized gold particles on silicon and silicon oxide substrates is investigated in detail. In addition, the strengths and weaknesses of the three models are elucidated, the different substrates used are compared, and the possibility to further process the obtained particles as nanocatalysts is verified. The importance of a persistent thin communication wetting layer between the particles and its effects on particle size and number is also clarified here. In particular, the intrinsic reduction of the Laplace pressure of the system due to material re-evaporation and Ostwald ripening describes the theoretically predicted and experimentally obtained results. Thus, dewetting phenomena of thin metal layers can be used to manufacture nanostructured devices. From this point of view, the application of gold droplets as catalysts to grow germanium nanowires on different substrates is described.

A template-guided, self-assembly patterning technique called discontinuous dewetting (DD) and liquid bridge transfer (LBT) was applied to successfully pattern single-walled carbon nanotubes (SWCNTs): the first 1D nanomaterials patterned using the technique. The technique could efficiently and simply pattern SWCNTs with 2.5-10 mu m resolution using little energy, low temperature (

International audience; We exhibit both experimentally and theoretically a novel growth mode for the epi-taxy of AlGaN quantum dots (QD), where they are eventually produced without their usual surrounding wetting layer. If the generic evolution of QD is ruled by the elastic relaxation and capillary effects, evaporation occurs here on a time scale similar to that of growth. Using a dedicated surface diffusion model accounting for elasticity, wetting and anisotropy, we evidence numerically different kinetic regimes as a function of the evaporation flux, that rationalize the experimental outcome. The resulting QD are characterized by enhanced optical properties compared to the common QD with a wetting layer. These nanostructures are promising candidates for deep ultraviolet light emitting diodes.

The structure and stability of a molecular wetting layer of the rodlike organic semiconductor molecule para-hexaphenyl grown at room temperature on atomically flat titanium dioxide TiO2(110) surfac...

Electrically conductive polymer fibers with high woven properties are in demand by broad application fields. The design of these materials for massive production requires high electrical conductivity, efficient fabrication yield, and economic accessibility. Here, we proposed a technique for fabricating continuous polymer fibers coated with 1D materials. By alternately coating conducting carbon black/polyurethane (PU) composites, single-walled carbon nanotubes (SWCNTs), and/or Ag nanowires (AgNWs) on Nylon-6 continuous fiber, lamellar cladding forms a compact conducting shell on the core fiber. The conductive fiber was continuously fabricated using the coaxial micro-painting technique of a 1D material solution. By keeping the size of the droplet constant at the vicinity of the tip of the flexible micro-painter, the Plateau-Rayleigh (P-R) instability of the wetting layer was depressed at fiber velocity far beyond inertial wetting. The fiber with a 2 μm-thick shell exhibits a conductivity of 53 ± 8 Ω/cm at a coating weight ratio of ∼6 wt % silver corresponding to a fiber conductivity of about 1665 S/cm. The much higher strain durability of the fiber coated with SWCNTs and AgNWs' lamellar structure than the fiber coated with only silver nanowires was explained by the local interlayer conducting paths from the AgNW layer to the SWCNT layer. The fiber maintains 90% conductivity after 105 repeated folding or knotting on the monofilament. The conducting yarns were designed and fabricated into electric circuits in textile. As a typical biomedical and flexible electronic application, a low-frequency electrocardiogram (ECG) signal on these circuits was demonstrated.

Recently, it has been reported, through using an in-situ laser exposure, nano holed structures can be created on the GaAs surface that is pre-capped by a thin InAs wetting layer and such nano holes were further proven to well serve as the preferential nucleation sites of InAs quantum dots (QDs). In this paper, we presented a study of how to further modify the morphology of the nano holes. First homo-deposition of 500nm GaAs buffer layer on GaAs (100) substrate and after capping of 0.5ML InAs, the as-prepared surface was in-situ exposed by a laser shot with energy of 20mJ. Then four different samples (A-D) were prepared, respectively corresponding to directly finishing the growth for sample A, for sample B repeating one cycle of “0.3ML InAs wetting layer capping + in situ laser exposure” before finishing the whole growth, two cycles for sample C and three cycles for sample D. It is found the density of nano holes on sample A is merely 5.5×108/cm2 with relatively small size possessing an average depth and width at 0.9nm and 36.6nm. After one cycle of “0.3ML InAs wetting layer capping + in situ laser exposure”, the density of nano holes on sample B increases by nearly one order of magnitude to 4.33×109/cm2 and the average depth and width become 1.0nm and 44.6nm. Further after two and three cycles, the resulting density would rise to 8.53 × 109/cm2 (sample C) and 1.12 × 1010/cm2 (sample D), correspondingly, the average depth/width are magnified to 1.1nm/54.2nm and 1.3nm/59.7nm. Hence, we have demonstrated an effective approach to modify the in-situ laser nano-holed patterning of GaAs surface which is supposed to have promising applications in controlled growth of QDs.

This erratum corrects the value of the wetting layer thickness provided in our Article [Opt. Express 29, 34024 (2021)10.1364/OE.438708]. This misprint does not influence the results and conclusions presented in the original Article.

Two-dimensional atomic layers composed of metallic atoms with a high principal quantum number in valence shells are promising materials for applications in state-of-the-art magnetic devices due to the presence of a strong spin-orbit coupling. In this work we experimentally explored the effects of triggering perpendicular magnetic anisotropy (PMA) of ferromagnetic (FM) films by applying a series of $6p$-Pb, Bi and $4d$-Pd (reference) atomic layers with high-level atomic orbital and low-level lattice strain. Our research indicates that, compared with Pd atoms, Pb and Bi atoms can produce higher-strength PMA on adjacent FM films through orbital hybridization at the interface. Moreover, we demonstrate that the PMA induced by Pb and Bi atoms is highly sensitive to the ordering degree of the wetting layer which is determined by the interplay of surface free, cohesive, and strain energies within the grown materials; the Pb(Bi) atoms added on the wetting layer can enhance the PMA of the adjacent FM film only when the wetting layer maintains an ordered structure. This work clarifies the critical interface effects of $6p$-HMs on the FM layer, thus providing important clues to increase control over the spin-orbit interaction engendered by HMs through the interface.

International audience; Picosecond ultrasonics, which studies laser-induced high-frequency strain waves, is a reliable and versatile method for nondestructive materials' characterization. Strain waves are generated through a light interaction with charges and their subsequent relaxation, and these waves conceal a wealth of information on the material. However, strain waves are detected through their convolution with a sensitivity function, which blurs much of this information. Here, we show that the reflection of strain waves at a free surface leads to the appearance of a Fano resonance in the reflectivity spectrum, accompanied by a drastic increase in the detection bandwidth. We take advantage of this feature to provide a method for the reconstruction of strain waves. We apply it to unambiguously highlight the exact origin of the generation of coherent acoustic phonons in Stranski-Krastanov grown quantum dots, revealing that both the wetting layer and quantum dots are responsible for the generation. Our results will offer the possibility to understand better the interaction of light with charges and their interactions with the lattice.

Stranski-Krastanov (SK) Quantum dots (QDs) based lasers and detectors are now used in many fields because of the plentiful advantages they offer, some of which are normal incident absorption and phonon bottleneck. In order to optimize the properties of the devices, growth parameters have to be tuned properly. The effects of growth temperature (GT) and growth rate (GR) variations on the QD devices have been studied here by comparing simulations and experiments. In this study, InAs QDs are grown on GaAs substrates with four different temperatures, from 480°C to 510°C, and with five different GRs, from 0.15 ML/s to 0.025ML/s. To observe the grown heterostructures' structural and optical properties photoluminescence (PL) and PL excitation (PLE) have been performed on the samples. The size, shape, and composition of the QDs ultimately decide the energy levels in the heterostructure. Hence, it determines the optical and electrical properties of the devices. Here we simulated 3-D strain profiles of the QD and compared the results with PL and PLE. The trends in simulated biaxial strain and heavy hole (HH) - light hole (LH) band splitting, observed in the PLE, match pretty well. We observed that the change in GT drastically affects the composition of the dots and the wetting layer, whereas a change in GR only changes the lateral size of the QDs, and do not affect the strain or composition. These studies can be beneficial for p-i-p short-wave infrared (SWIR) detectors since their spectral response is tuned by the HH-LH band splitting.

The analytical and numerical analyses as well as prediction with artificial neural network (ANN) for chaos-based artificial intelligence applications of quantum dot light emitting diode (QDLED) are investigated in this paper. The system of equations describing QDLED has three, or one equilibrium points depending on the capture rate from wetting layer into the dot and the injection current. The stability analysis of the equilibrium points reveals the existence of Pitchfork and Hopf bifurcations. The different dynamical behaviors (including steady state, periodic and chaotic behaviors) found in QDLED are illustrated in two parameters bifurcation diagrams, phase portraits and time series. Finaly, the QDLED system is predicted using ANN for chaos-based artificial intelligence applications.

Ultrathin gold films are attractive for plasmonic and metamaterial devices, thanks to their useful optical and optoelectronic properties. However, deposition of ultrathin continuous Au films of a f...

We analyzed the experiments of Rubio-Zuazo and Castro [J. Electron Spectrosc. Relat. Phenom. 184 (2011) 384] who reported measurements of effective attenuation lengths (EALs) of gold for electron energies between 1 keV and 15 keV. They deposited thin films of gold on a copper substrate and measured the intensities of various Cu and Au photoelectron lines excited by synchrotron X-rays. Their derived EALs were based on the assumption that their films were of uniform thickness (i.e., layer-by-layer film growth). We considered two other forms of film growth: island formation (Volmer-Weber film growth) and island growth on a continuous monatomic wetting layer (Stranski-Krastanov film growth). We utilized the National Institute of Standards and Technology Database for the Simulation of Electron Spectra for Surface Analysis (SESSA) to determine the fractional Au island areas for each Au film thickness that would give the same intensity changes of Cu and Au photoelectron lines that were observed in the experiments. These results showed that growth of the Au film as islands provided a better description of the experimental results than uniform film growth. We could also distinguish Stranski-Krastanov film growth from Volmer-Weber growth and believe that the former is more likely.

The poor thermoplastic formability is one of the bottlenecks in restricting the wide application of Ti-based bulk metallic glasses. In this study, alloying method was adopted to improve the thermoplastic formability of a lightweight Ti–Zr–Be bulk metallic glass (BMG). Different combinations of alloying elements, alloying routes and alloying contents have been tried to optimize the alloy composition. S parameter was found to be an effective indicator for evaluating the thermoplastic formability of the studied Ti-based bulk metallic glasses. A Ti45Zr20Be30Fe5 alloy, which possesses unique thermoplastic formability, has been successfully developed. A nanomoulding processing map for Ti45Zr20Be30Fe5 alloy has been constructed. To reduce the capillary effect, a wetting layer has been introduced during the nanomoulding process. Finally Ti-based BMG nanorods have been successfully fabricated in air, which further confirms the effectiveness of the proposed processing map and the superior thermoplastic formability of developed Ti45Zr20Be30Fe5 BMG.

This study models quantum dot (QD) plasmonic nanolaser. A metal/semiconductor/metal (MSM) structure was considered to attain plasmonic nanocavity. The active region (semiconductor layers) contains the following: QD, wetting layer (WL), and barrier layers. Band alignment between layers was used to predict their parameters. Momentum matrix element for transverse magnetic (TM) mode in QD structure was formulated. Waveguide Fermi energy was introduced and formulated, for the first time, in this work to cover the waveguide contribution (Ag metal layer) in addition to the active region. The high net modal gain was obtained when the waveguide Fermi energy was considered which meant that the increment comes from the material gain, not from the confinement factor. The obtained results were reasoned the high gain due to the change in waveguide Fermi energy in the valence band, where the valence band QD states are fully occupied that are referring to an efficient hole contribution.

A model was presented for linear susceptibility in ladder-plus-Y configuration of double quantum dot system using density matrix theory and including spontaneously generated coherence of Λ-type system. Wetting layer and quantum dot inhomogeneity were considered in the calculations, which gives a practical description of double quantum dot structures well. With increasing spontaneously generated coherence from Λ-component, the dispersion was increased and shifted under spontaneously generated coherence. The inclusion of wetting layer under spontaneously generated coherence increases gain which coincides with the published results. A possibility of slow light was predicted.

Shear strength between Sn–3.0Ag–0.5Cu (SAC) solders and Cu/Ti in under bump metallization (UBM) samples aged using two solid-state aging processes was investigated. One method aged the samples at 200 °C for up for five 1-h intervals; the other aged the samples at 200 °C continuously for up to 5 h in a convection oven. After reflow, all samples showed scallop-shaped Cu6Sn5 intermetallic compounds (IMCs) at the interfaces between SAC solder and Cu substrate. After aging, the Cu layers of all samples were gradually depleted, and lump-shaped Cu6Sn5 was observed to be separated from the SAC/Cu interfaces. The shear strength of all samples was gradually decreased with increased aging due to depletion of the Cu wetting layer, formation of IMCs with solder, and separation of the IMCs from the interfaces during aging. Quantitative analysis revealed that exposed Ti area is an effective predictor of decrease in shear strength generated by the spalling phenomenon.

Growth of ultra-thin Au films on Si(1 1 1)√3 × √3-Bi surfaces was studied using low energy electron diffraction, scanning tunneling microscopy and in situ measurements of surface conductivity. The Si(1 1 1)√3 × √3-Bi surfaces were represented either by the Si(1 1 1)-α-√3 × √3-Bi phase with 0.33 ML (monolayers) of Bi adatoms or by the Si(1 1 1)-β-√3 × √3-Bi phase with 1.0 ML of Bi atoms arranged into trimers. Structure of the template surface was found to affect greatly the growth mode and conductance of the overgrown Au films in the thickness range from 0.1 to 3.0 ML of Au. Growth of Au films on Si(1 1 1)-β-√3 × √3-Bi follows the Vollmer-Webber mode, while in case of Au films on Si(1 1 1)-α-√3 × √3-Bi the complicated multi-stage growth occurs where formation of Stranski-Krastanov wetting layer is successively followed by island growth and vice versa. Surface conductivity of the samples was found to be dictated by Au film morphology. In the Au/Si(1 1 1)-β-√3 × √3-Bi sample, surface conductivity remains essentially unchanged due to lacking of electrical connections between Au islands. In the Au/Si(1 1 1)-α-√3 × √3-Bi sample, surface conductivity grows with Au thickness starting from overcoming of percolation threshold at ∼0.6 ML of Au.

III-V materials have yet proved to be promising candidates for photovoltaic applications. Solar cell technologies based on III-V semiconductors are competitive in term of fabrication cost but also have the potential to reach the highest photovoltaic efficiencies. To overcome the 30% conversion limitation established for a single junction, the Shockley Queisser limit [1], due to different losses that cannot be avoided (transmission, thermalization, emission…), different solar cell architectures have been proposed. One of them, multi-junctions, are using a stack of absorbing materials enabling to cover a wider part of the solar spectrum with high efficiency due to their optimized bang-gaps. Among other recent concepts, intermediate band solar cells have gained interest with predicted efficiency greater than 60% (under maximum concentration) and almost 48.2% under one sun [2], similar to the efficiency potential of a 3 material stack, but with a single material. By implementing quantum dots at the surface of a III-V single layer, an intermediate band can be generated [3, 4] and tuned by changing the quantum dots nature, size and shape. More complex structures with multi-stacked quantum dots have also been studied [5]. The present work focuses on the preparation of III-V quantum dots surfaces using wet chemistry. Not only dots evolution but also the development of a specific soaking to eliminate the wetting layer, detrimental for optoelectronic properties, will be shown. Numerous studies and formulation have been reported for chemical etching of III-V semiconductors [6]. Nevertheless, the remaining challenge concerns the implementation of this chemical engineering at nanometric scale [7], in consistency with the miniaturization trend and requirements of the materials, structures and devices. The study is carried out on InAs and InGaAs quantum dots grown by MBE on GaAs substrates. They present different surface densities. The structure of the samples is presented figure 1 where the wetting layer, essential for the quantum dots epitaxial growth, is illustrated. A multi-technique methodology combining XPS, AFM and nano-Auger is employed to precisely determine the surface chemical and morphologic modifications from micrometric to nanometric scale. Thanks to XPS, the evolutions of the fine chemistries of quantum dots and their surface are accessible, giving crucial information about the dissolution processes and enabling to re-adjust the experimental conditions. In Figure 1 b, the In3d photopeak evolution with the chemical treatment employed on a sample presenting only the wetting layer is shown. Indium atoms are only present in the wetting layer in this case. Thus it represents the tracking element indicative of the maintenance, thinning or elimination of this layer. The complementary use of AFM brings the evidence of the dots conservation or disappearance as illustrated Figure 1c. Nano-Auger provides additional information on local chemistry. Various formulations, in acidic or base media, are developed to enable a differential dissolution between the wetting layer and the quantum dots. Both oxidation-deoxidation cycling and direct dipping procedures were experimented and optimized taking account the differences in oxides solubility. The various scenarios likely to occur during deoxidation are presented Figure 1a, the elimination of QD being also possible by the dissolution of the wetting layer below. Finally, a comparison of capabilities for nano-etching and possible selectivity of the different solutions considered here will be presented. References [1] W. Shockley and H.J. Queisser, J. Appl. Phys. 32 (1961), 510. [2]A. Luque, A. Marti, Phys. Rev .Lett. 78 (1997) 5014-5017. [3] T. Sogabe, Y. Shoji, M. Ohba, K. Yoshida, R.Tamaki, H.-F. Hong, C.-H. Wu, C.-T. Kuo, S. Tomić, and Y. Okada, Scientific Reports (Nature Publishing Group), 4, (2014)/4/25. doi:10.1038/srep04792. [4] E. Lopez, A. Datas, I. Ramiro, P.G. Linares, E. Antolin, I. Artacho, A. Marti, A. Luque, Y. Shoji, T. Sogabe, A. Ogura, Y. Okada, Sol. Energy Mater Sol. Cells 149 (2016) 15-18. [5] T. Kada, S. Asahi, T. Kaizu, Y. Harada and T. Kita, Phys. Rev. B 91 (2015) 201303(R). [6] A.R. Clawson, Reports: a review journal, Mater. Sci. Eng. 31 (2001) 1-438. [7] D. H. van Dorp, S. Arnauts, M. Laitinen, T. Sajavaara, J. Meersschaut, T. Conard and John J. Kelly, Appl. Surf. Sci. 465, (2018), Pages 596-606. Figure 1

International audience; We perform numerical simulations of hexagonal quantum dots of AlGaN semiconductors. We show that the competition between surface mass diffusion and evaporation rules the morphology of the quantum dots. The system displays three different behaviors: presence of separated islands without a wetting layer, islands dissolving into the wetting layer, or islands that do not evolve. The first behavior is of special interest because its optoelectrical properties are significantly improved in comparison with quantum dots with a wetting layer.; Nous effectuons une simulation numérique des boîtes quantiques hexagonales de semiconducteurs AlGaN. Nous montrons que la compétition entre la diffusion de masse en surface et l'évaporation détermine la morphologie des boîtes quantiques. Le système montre trois comportements différents : des îlots séparés sans couche de mouillage, des îlots se dissolvant dans la couche de mouillage ou des îlots ne pouvant évoluer. Le premier comportement présente un intérêt particulier, car les propriétés optoélectriques sont considérablement améliorées par rapport aux boîtes quantiques avec une couche de mouillage.

Two-dimensional arrays of nanoparticles (NPs) have widespread applications in optical coatings, plasmonic sensors, and nanocomposites. Current bottom-up approaches that use homogeneous NP templates, such as silane self-assembled monolayers or homopolymers, are typically plagued by NP aggregation, whereas patterned block copolymer (BCP) films require specific compositions for specific NP distributions. Here, we show, using polystyrene- b-poly(4-vinylpyridine) (PS- b-P4VP) and gold NPs (AuNPs) of various sizes, that a nanothin PS- b-P4VP brushlike coating (comprised of a P4VP wetting layer and a PS overlayer), which is adsorbed onto flat substrates during their immersion in very dilute PS- b-P4VP tetrahydrofuran solutions, provides an excellent template for obtaining dense and well-dispersed AuNPs with little aggregation. These non-close-packed arrays have similar characteristics regardless of immersion time in solution (about 10-120 s studied), solution concentration below a critical value (0.1 and 0.05 mg/mL studied), and AuNP diameter (10-90 nm studied). Very dilute BCP solutions are necessary to avoid deposition, during substrate withdrawal, of additional material onto the adsorbed BCP layer, which typically leads to patterned surfaces. The PS brush coverage depends on immersion time (adsorption kinetics), but full coverage does not inhibit AuNP adsorption, which is attributed to PS molecular rearrangement during exposure to the aqueous AuNP colloidal solution. The simplicity, versatility and robustness of the method will enable applications in materials science requiring dense, unaggregated NP arrays.

Fe-Cu low-carbon steels play significant roles in a rich variety of applications. The high strength of Fe-Cu steels originates from the strengthening effect of Cu precipitates. Further optimization of mechanical properties of Fe-Cu and Fe-Cu based steels requires an understanding of precipitation process of Cu particles. In this study, a comprehensive phase field model is developed which captures the microstructure evolution process during the nucleation and growth of BCC Cu precipitates followed by the BCC → 9R phase transformation. Results generated by phase field simulations agree well with previous experimental reports. In addition, the pseudo-spinodal decomposition theory is adopted to analyze the kinetic process of precipitation. Our simulation results and theoretical analyses jointly demonstrate that the kinetic process of precipitation and the initial Cu concentration of precipitates are ageing temperature and composition dependent, which is helpful in solving the mystery of the Cu concentration in precipitates of early stage. Moreover, interfacial energy and internal stress are found to be responsible for the temperature and composition dependence of critical nucleation size of the 9R phase, respectively. The nature of wetting layer and the mechanism that regulates the thickness of wetting layers are revealed as well. The comprehensive phase field model developed in this study offers a powerful tool for investigating precipitations in Fe-Cu alloys. The findings of this study provide new insights on the evolution process of Cu precipitates in Fe-Cu alloys.

In this work we investigated the electronic states of InAsP/GaAs QDs using photoluminescence (PL) and photomodulated transmission (PT) experiments. PL measurements were performed as a function of temperature and excitation power. As the recombination energy of the InAsP/GaAs QDs resides in between the extremes InAs/GaAs and InP/GaAs QDs, these two materials were also analyzed. From PL experiments we could identify the recombination from the QDs ground state and the contribution of the InAsP and InP wetting layer (WL) with a macro PL technique. PL measurements of annealed samples allowed us to to clearly identify the WL electronic states. Specifically for the InP/GaAs QDs, the WL and QD recombination overlap as a single PL band. Photomodulated transmission spectroscopy (PT) showed spectral structure consistent with the QD and WL assignments given after the PL analysis.

Direct embedding of Cu nanoparticles into the PVA surface is detected by AFM and a fresh embedding mechanism submitted via the change of the annealing temperatures (Tannealing). When the Tannealing goes above the glass transition temperature of PVA, Cu nanoparticles are rapidly sinked by a thin wetting layer of PVA. In order to it makes capillary pressure on a Cu nanoparticles, suggested, this wetting layer is accountable for Cu embedding. Also, study of the thermal and mechanical properties of the nanocomposites during the embedding of Cu into the PVA. The XRD patterns show that the presence of the Cu nanoparticles in the PVA matrix. The DSC studies show an increase in the glass temperature (Tg) from 344.4 K for the green PVA to 354.2 K for the annealing temperature 423 K. Also shows two melting points for the composites (PVA/Cu nano) with thermal annealing temperature below the glass temperature (Tg) and one melting point with annealing above the glass temperature (Tg). The study shows that Young’s modulus (Y) increases with increasing the thermal annealing temperatures from 0.20 × 109 Pa for the green PVA to 3.75 × 109 Pa for the annealing temperature 423 K. In addition to, the strength at the break increases, while the elongation at break decreases with increasing the thermal annealing temperatures.

Initial growth process of pentacene molecules on clean Si(001)-2 × 1 substrate was investigated by scanning tunneling microscopy. It is found that the wetting layer, which is not crystalline but disordered, forms before the growth of a first crystalline layer. The wetting layer consists of double layer of the flatly adsorbed pentacene molecules. The formation of the wetting double layer is discussed. The first crystalline layer that is grown on the disordered wetting layer with standing-up pentacene molecules consists of some domains that differ in their crystal structures. Among them, a new pentacene crystal structure is found that can form only on the first layer. In contrast, the second crystalline layer has only single domain. Moreover, we investigated the electronic properties of the pentacene layers by the current–voltage measurements. The pentacene layers are semiconducting with a band gap of about 4 eV.

Ferroelectric topological configurations confined in nanostructures have attracted intensive interest both in fundamental physics and potential applications in non-volatile nanoelectronic devices. However, the preparation approaches such as chemical synthesis and template or electron beam etching inevitably induce damage and contamination; also, these are complicated processes. Herein, by a delicate design of the wetting layer and growth temperature, self-assembled ferroelectric nanoislands were achieved with the BiFeO3/(La,Sr)MnO3/LaAlO3 heterostructure. Based on the thermodynamic analysis, the much lower surface energy (∼0.47 J m-2) of the (La,Sr)MnO3 (∼2-12 nm)/LaAlO3 system than that (∼1.0 J m-2) of BiFeO3 provides the probability for the transformation of layered morphology into nanoislands. From the dynamic perspective, the high growth temperature (∼650-680 °C) helps to step over the energy barrier (∼50 meV per atom) by stimulating the formation of periodically arrayed dislocations at the BiFeO3/(La,Sr)MnO3 interface, which on the one hand releases the epitaxial elastic energy and on the other hand evokes the nucleation of the R-phase nanoisland array. More excitingly, this approach with a wonderful new growth mechanism can also be employed in other ferroelectric model systems such as BaTiO3, which provides a new strategy for the design of novel nanoelectronic devices based on ferroelectric perovskite nanostructures.

The surface phonon dispersion curves of ultrathin (3–6 ML) Pb layers grown on Si(111) and Ge(111) substrates, measured with inelastic He atom scattering, reveal shallow Kohn anomalies in the surface acoustic branches. Ab-initio calculations based on density functional perturbation theory for the 3–6 monolayers of Pb on a rigid substrate, besides reproducing well the observed dispersion curves, allow for the assignment of the anomalies to well defined flat segments of the Fermi contours. Unlike Pb films grown on Cu(111), where both the optical surface and the interface phonon branches above the bulk frequency maximum are observed, for Si(111) and Ge (111) only the surface-localized branch is observed, indicating the comparatively weaker film-substrate interaction. Consistently with the observation of superconductivity in ultrathin Pb films on Si(111) down to one monolayer (wetting layer), the mass-enhancement factor derived from the specular scattering intensity dependence on the film thickness is found for both substrates in the range of unity, however with slightly larger values for the Ge(111) substrate.