Flat metamorphic InAlAs buffer layer on GaAs(111)A misoriented substrates by growth kinetics control

We have successfully grown, through the detailed control of the growth kinetics, flat InAlAs metamorphic buffer layers on 2 degrees -off GaAs(111)A substrates using molecular beam epitaxy. Almost full plastic relaxation is obtained for a layer thickness > 40 nm. The control of an adatom diffusion length and a step ejection probability from the bunches permits a reduction of the InAlAs epilayer root-mean-square surface roughness to 0.55 nm

Antioxidant activities of hydroxylated naphthalenes: the role of aryloxyl radicals

Herein is delineated a first systematic framework for the definition of structure-antioxidant property relationships in the dihydroxynaphthalene (DHN) series. The results obtained by a combined experimental and theoretical approach revealed that 1,8-DHN is the best performing antioxidant platform, with its unique hydrogen-bonded peri-hydroxylation pattern contributing to a fast H atom transfer process. Moreover, the comparative analysis of the antioxidant properties of DHNs carried out by performing DPPH and FRAP assays and laser flash photolysis experiments, revealed the higher antioxidant power associated with an α-substitution pattern (i. e. in 1,8- and 1,6-DHN) with respect to DHNs exhibiting a β-substitution pattern (i. e. in 2,6- and 2,7-DHN). DFT calculations and isolation and characterization of the main oligomer intermediates formed during the oxidative polymerization of DHNs supported this evidence by providing unprecedented insight into the generation and fate of the intermediate naphthoxyl radicals, which emerged as the main factor governing the antioxidant activity of DHNs

Photoluminescence Study of Low Thermal Budget III–V Nanostructures on Silicon by Droplet Epitaxy

We present of a detailed photoluminescence characterization of high efficiency GaAs/AlGaAs quantum nanostructures grown on silicon substrates. The whole process of formation of the GaAs/AlGaAs active layer was realized via droplet epitaxy and migration enhanced epitaxy maintaining the growth temperature ≤350°C, thus resulting in a low thermal budget procedure compatible with back-end integration of the fabricated materials on integrated circuits

Control of the lateral growth morphology in GaAs Droplet Epitaxy

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Wurtzite nanowires strain control by DC electrical stimulation

Nanomechanics is a highly developed area of research, given the significant reported changes in material properties at the nanometer scale, requiring the development of new theories to explain the underlying mechanisms. Such theories must be based on measurements that are as accurate as possible, but unfortunately, conventional experimental techniques do not apply to such small components. Here we present a unique new method to control electro-mechanical forces on quasi −1D nanostructures through static electric fields with multiple ways of control of GaAs nanowires’ strain directly on the growth substrate

Optical characterization of individual GaAs quantum dots grown with height control technique

We show that the epitaxial growth of height-controlled GaAs quantum dots, leading to the reduction of the inhomogeneous emission bandwidth, produces individual nanostructures of peculiar morphology. Besides the height controlled quantum dots, we observe nanodisks formation. Exploiting time resolved and spatially resolved photoluminescence we establish the decoupling between quantum dots and nanodisks and demonstrate the high optical properties of the individual quantum dots, despite the processing steps needed for height control.Sarti, F.; Muñoz Matutano, G.; Bietti, S.; Vinattieri, A.; Sanguinetti, S.; Gurioli, M. (2013). Optical characterization of individual GaAs quantum dots grown with height control technique. Journal of Applied Physics. 114(2):1243011-1243014. doi:10.1063/1.4821901S124301112430141142Shields, A. J. (2007). Semiconductor quantum light sources. Nature Photonics, 1(4), 215-223. doi:10.1038/nphoton.2007.46Koguchi, N. (1993). New selective molecular-beam epitaxial growth method for direct formation of GaAs quantum dots. Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 11(3), 787. doi:10.1116/1.586789Watanabe, K., Koguchi, N., & Gotoh, Y. (2000). Fabrication of GaAs Quantum Dots by Modified Droplet Epitaxy. Japanese Journal of Applied Physics, 39(Part 2, No. 2A), L79-L81. doi:10.1143/jjap.39.l79Sanguinetti, S., & Koguchi, N. (2013). Droplet epitaxy of nanostructures. Molecular Beam Epitaxy, 95-111. doi:10.1016/b978-0-12-387839-7.00004-xKeizer, J. G., Bocquel, J., Koenraad, P. M., Mano, T., Noda, T., & Sakoda, K. (2010). Atomic scale analysis of self assembled GaAs/AlGaAs quantum dots grown by droplet epitaxy. Applied Physics Letters, 96(6), 062101. doi:10.1063/1.3303979(s. f.). doi:10.1021/nl048192Lee, J. H., Wang, Z. M., Abuwaar, Z. Y., Strom, N. W., & Salamo, G. J. (2006). Evolution between self-assembled single and double ring-like nanostructures. Nanotechnology, 17(15), 3973-3976. doi:10.1088/0957-4484/17/15/061Somaschini, C., Bietti, S., Koguchi, N., & Sanguinetti, S. (2011). Coupled quantum dot–ring structures by droplet epitaxy. Nanotechnology, 22(18), 185602. doi:10.1088/0957-4484/22/18/185602Somaschini, C., Bietti, S., Koguchi, N., & Sanguinetti, S. (2009). Fabrication of Multiple Concentric Nanoring Structures. Nano Letters, 9(10), 3419-3424. doi:10.1021/nl901493fReyes, K., Smereka, P., Nothern, D., Millunchick, J. M., Bietti, S., Somaschini, C., … Frigeri, C. (2013). Unified model of droplet epitaxy for compound semiconductor nanostructures: Experiments and theory. Physical Review B, 87(16). doi:10.1103/physrevb.87.165406Bietti, S., Somaschini, C., & Sanguinetti, S. (2013). Crystallization kinetics of Ga metallic nano-droplets under As flux. Nanotechnology, 24(20), 205603. doi:10.1088/0957-4484/24/20/205603Jo, M., Mano, T., & Sakoda, K. (2010). Morphological control of GaAs quantum dots grown by droplet epitaxy using a thin AlGaAs capping layer. Journal of Applied Physics, 108(8), 083505. doi:10.1063/1.3493262Ohtake, A. (2008). Surface reconstructions on GaAs(001). Surface Science Reports, 63(7), 295-327. doi:10.1016/j.surfrep.2008.03.001Mano, T., Abbarchi, M., Kuroda, T., Mastrandrea, C. A., Vinattieri, A., Sanguinetti, S., … Gurioli, M. (2009). Ultra-narrow emission from single GaAs self-assembled quantum dots grown by droplet epitaxy. Nanotechnology, 20(39), 395601. doi:10.1088/0957-4484/20/39/395601Adorno, S., Bietti, S., & Sanguinetti, S. (2013). Annealing induced anisotropy in GaAs/AlGaAs quantum dots grown by droplet epitaxy. Journal of Crystal Growth, 378, 515-518. doi:10.1016/j.jcrysgro.2012.11.006Horikoshi, Y., Kawashima, M., & Yamaguchi, H. (1988). Migration-Enhanced Epitaxy of GaAs and AlGaAs. Japanese Journal of Applied Physics, 27(Part 1, No. 2), 169-179. doi:10.1143/jjap.27.16

Ordered array of Ga droplets on GaAs(001) by local anodic oxidation

The authors present a procedure to obtain uniform, ordered arrays of Ga droplets on GaAs(001) substrates. The growth process relies on an interplay between the substrate patterning, in form of a two dimensional array of nanoholes periodically modulated obtained via local anodic oxidation, and self-assembly of Ga droplets in a molecular beam epitaxy environment. The formation of site controlled Ga droplets, characterized by atomic force microscopy, is the outcome of the combined effects of capillary condensation and nucleation kinetics

Erratum to: Concentric Multiple Rings by Droplet Epitaxy: Fabrication and Study of the Morphological Anisotropy

We present the Molecular Beam Epitaxy fabrication of complex GaAs/AlGaAs nanostructures by Droplet Epitaxy, characterized by the presence of concentric multiple rings. We propose an innovative experimental procedure that allows the fabrication of individual portions of the structure, controlling their diameter by only changing the substrate temperature. The obtained nanocrystals show a significant anisotropy between [110] and [1–10] crystallographic directions, which can be ascribed to different activation energies for the Ga atoms migration processes

Electroproduction, photoproduction, and inverse electroproduction of pions in the first resonance region

Methods are set forth for determining the hadron electromagnetic structure in the sub-$N\bar{N}$-threshold timelike region of the virtual-photon ``mass'' and for investigating the nucleon weak structure in the spacelike region from experimental data on the process $\pi N\to e^+e^- N$ at low energies. These methods are formulated using the unified description of photoproduction, electroproduction, and inverse electroproduction of pions in the first resonance region in the framework of the dispersion-relation model and on the basis of the model-independent properties of inverse electroproduction. Applications of these methods are also shown.Comment: The revised published version; Revtex4, 18 pages, 6 figure