tailieunhanh - Báo cáo hóa học: " Concentric Multiple Rings by Droplet Epitaxy: Fabrication and Study of the Morphological Anisotropy"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Concentric Multiple Rings by Droplet Epitaxy: Fabrication and Study of the Morphological Anisotropy | Nanoscale Res Lett 2010 5 1865-1867 DOI s11671-010-9699-6 SPECIAL ISSUE ARTICLE Concentric Multiple Rings by Droplet Epitaxy Fabrication and Study of the Morphological Anisotropy C. Somaschini S. Bietti A. Fedorov N. Koguchi S. Sanguinetti Received 9 July 2010 Accepted 13 July 2010 Published online 1 August 2010 The Author s 2010. This article is published with open access at Abstract 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. Keywords GaAs AlGaAs Molecular beam epitaxy Droplet epitaxy Quantum rings Introduction In recent times Droplet Epitaxy DE 1 2 has extensively been used for the fabrication of III-V semiconductor quantum nanostructures that show a good rotational symmetry. Indeed with this MBE-based technique many different quantum systems with cylindrical symmetry can be grown ranging from quantum rings QRs 3 4 to concentric multiple quantum rings CMQRs 5 to coupled rings disks CRDs 6 . The interest in fabricating such structures is both fundamental for the investigation of quantum interference phenomena 7 8 and practical in the fields of optoelectronics 9 and quantum information C. Somaschini S. Bietti A. Fedorov N. Koguchi S. Sanguinetti LNESS and Dipartimento di Scienza dei Materiali via Cozzi 53 20125 Milan Italy e-mail technology 10 . In GaAs DE the fabrication of the compound semiconductor is basically achieved in two steps first Ga molecular beam is supplied on the substrate in absence of As .