tailieunhanh - Báo cáo hóa học: " Investigation of pre-structured GaAs surfaces for subsequent site-selective InAs quantum dot growth"

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: Investigation of pre-structured GaAs surfaces for subsequent site-selective InAs quantum dot growth | Helfrich et al. Nanoscale Research Letters 2011 6 211 http content 6 1 211 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Investigation of pre-structured GaAs surfaces for subsequent site-selective InAs quantum dot growth 1 2 2 3 3 Mathieu Helfrich Roland Groger Alexander Forste Dimitri Litvinov Dagmar Gerthsen Thomas Schimmel Daniel M Schaadt1 Abstract In this study we investigated pre-structured 100 GaAs sample surfaces with respect to subsequent site-selective quantum dot growth. Defects occurring in the GaAs buffer layer grown after pre-structuring are attributed to insufficient cleaning of the samples prior to regrowth. Successive cleaning steps were analyzed and optimized. A UV-ozone cleaning is performed at the end of sample preparation in order to get rid of remaining organic contamination. Introduction Quantum dots QDs are promising candidates for quantum information devices such as quantum bits in quantum computers or quantum memories. Selfassembled QDs were investigated in this context during the past decade. They can produce single photons and can be coupled to microcavity resonators 1 2 . However for large-scale applications it is essential to transfer the aforementioned schemes to well-positioned QDs in order to obtain a defined device architecture. One approach to site-selective QD growth utilizes substrate pre-structuring 3 4 . Small holes are created on the substrate surface in order to alter the surface chemical potential which leads to an increased growth rate at the hole sites. Thus QDs preferentially nucleate at the defined locations. Various tools such as electron beam lithography EBL or local oxidation are available to pre-structure substrates 5 6 . In most cases the procedure of prestructuring involves several process steps including different chemicals which influence the substrate surface. For subsequent QD growth however it is necessary to provide a clean surface in order to .