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Tuyển tập các báo cáo nghiên cứu về hóa học được đăng trên tạp chí hóa hoc quốc tế đề tài : Critical aspects of substrate nanopatterning for the ordered growth of GaN nanocolumns | Barbagini et al. Nanoscale Research Letters 2011 6 632 http www.nanoscalereslett.eom content 6 1 632 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Critical aspects of substrate nanopatterning for the ordered growth of GaN nanocolumns o -s rpi s z t I 1 I A -s o r-1 f Z X z c r s L r 1fCb z Al L srh1 I V z I Z r K I zb I r Ĩ 1 f Francesca Barbagini Ana Bengoechea-Encabo Steven Albert Javier Martinez Miguel Angel Sanchez García1 f Achim Trampert21 and Enrique Calleja1 f Abstract Precise and reproducible surface nanopatterning is the key for a successful ordered growth of GaN nanocolumns. In this work we point out the main technological issues related to the patterning process mainly surface roughness and cleaning and mask adhesion to the substrate. We found that each of these factors process-related has a dramatic impact on the subsequent selective growth of the columns inside the patterned holes. We compare the performance of e-beam lithography colloidal lithography and focused ion beam in the fabrication of hole-patterned masks for ordered columnar growth. These results are applicable to the ordered growth of nanocolumns of different materials. Keywords GaN nanocolumns ordered growth molecular beam epitaxy surface cleaning roughness adhesion ebeam lithography colloidal lithography focused ion beam Background The unique properties of III-nitride nanocolumns NCs in contrast to thin film structures derive from the reduced footprint on the substrate that enables essentially dislocation- and strain- free growth on a variety of substrates 1 . Defect-free NCs exhibit excellent electronic transport and optical properties for the fabrication of high-efficiency optoelectronic nanodevices such as photodetectors light-emitting diodes and solar cells 2-5 . Moreover the controlled coalescence of III-nitride NCs would lead to strain-free pseudosubstrates with reduced defect densities 6 . During the past years III-nitride NCs have been grown in the .
