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Local droplet etching (LDE) utilizes metal droplets during molecular beam epitaxy for the self-assembled drilling of nanoholes into III/V semiconductor surfaces. An essential process during LDE is the removal of the deposited droplet material from its initial position during post-growth annealing. This paper studies the droplet material removal experimentally and discusses the results in terms of a simple model. The first set of experiments demonstrates that the droplet material is removed by detachment of atoms and spreading over the substrate surface. Further experiments establish that droplet etching requires a small arsenic background pressure to inhibit re-attachment of the detached atoms. Surfaces processed under completely minimized As pressure show no hole formation but instead a conservation of the initial droplets. Under consideration of these results, a simple kinetic scaling model of the etching process is proposed that quantitatively reproduces experimental data on the hole depth as a function of the process temperature and deposited amount of droplet material. Furthermore, the depth dependence of the hole side-facet angle is analyzed.

In this work, we presented a surface mechanical attrition treatment (SMAT)-assisted approach to the synthesis of one-dimensional copper oxide nanowires (CuO NWs) for nanodevices applications. The as-prepared CuO NWs have diameter and the length of 50 ~ 200 nm and 5 ~ 20 μm, respectively, with a preferential growth orientation along [1 0] direction. Interestingly, nanofield-effect transistor (nanoFET) based on individual CuO NW exhibited typical p-type electrical conduction, with a hole mobility of 0.129 cm2V-1 s-1 and hole concentration of 1.34 × 1018 cm-3, respectively. According to first-principle calculations, such a p-type electrical conduction behavior was related to the oxygen vacancies in CuO NWs. What is more, the CuO NW device was sensitive to visible light illumination with peak sensitivity at 600 nm. The responsitivity, conductive gain, and detectivity are estimated to be 2.0 × 102 A W-1, 3.95 × 102 and 6.38 × 1011 cm Hz1/2 W-1, respectively, which are better than the devices composed of other materials. Further study showed that nanophotodetectors assembled on flexible polyethylene terephthalate (PET) substrate can work under different bending conditions with good reproducibility. The totality of the above results suggests that the present CuO NWs are potential building blocks for assembling high-performance optoelectronic devices.

This year, Italy hosted the VIII ESPS-NIS workshop. It was organized by the L-NESS Inter-University Laboratory (Politecnico di Milano and Universita di Milano Bicocca) in Como (Italy) under the auspices of Prof. Leo Miglio. The program of 10 invited speakers, 30 contributed and numerous posters covered a wide range of topics, all connected with the study of substrate patterning and high index substrate influence on the growth and the control of semiconductor nanostructures. Presentation was given on novel patterning techniques, both top-down and bottom-up, and the effect of patterning on self-organized dots and wires. In particular, wires have recently attracted a wide attention, since they are important both in fundamental physics and in advanced electronics and photonics applications. New concept bottom-up patterning techniques, like metallic droplet nano-drilling and droplet epitaxy local artificial substrates, were presented. Epitaxy of graphene on patterned substrates was also a topic of the workshop. The possibility of controlling, by substrate patterning, the nucleation site and the strain relaxation of self-organized Stranski–Krastanow dots in Ge/Si and InAs/GaAs systems has motivated a strong effort as evidenced by the number and the quality of the contribution presented. Some very interesting features involve strain engineering, position and size control, defectivity reduction. In addition, patterned substrates epitaxy inevitably involves growth on high index planes, which stimulated the understanding the effects of epitaxial growth of semiconductors on non-(100) surfaces. The ESPS-NIS meeting discussed all these aspects, which include material growth, characterization, theory and device topics related to patterned substrates, novel index substrates and low dimensional structures. Once more the meeting achieved its aim of being a forum for lively discussion of up to date work, allowing the interaction of specialist of different fields of semiconductor science and technology put together by the common interest in the effects of patterning and surface orientation on nanostructure fabrication. The vast potential of interrelation of nanotechnology, patterning and surface science was highlighted. The organizing committee would like to thank the speakers for their considerable efforts in making this workshop a success. A fundamental role in the organization was also played by the personnel of the the Centro di Cultura Scientifica Alessandro Volta of Como. Finally, special thanks are due to the University of Milano Bicocca and the Politecnico di Milano, Polo di Como whose sponsorship made this international workshop possible. ESPS-NIS VIII Conference Chair: Prof. Leo Miglio (University of Milano Bicocca) Program committee: Chair: Prof. Stefano Sanguinetti (University of Milano Bicocca) Dr Francesco Montalenti (University of Milano Bicocca) Dr Roman Sordan (Politecnico di Milano) Dr Daniel Chrastina (Politecnico di Milano) Local organizing Committee Dr Giovanni Isella (Politecnico di Milano) Dr Emiliano Bonera (University of Milano Bicocca) Dr Monica Bollani (CNR—Milano) Dr Alessandra Cazzaniga (Centro Volta)