Understanding the growth of III-­V nanowires through microscopy analyses by Dr Jennifer Wong-­Leung, ANU

by Dr Jennifer Wong-Leung (ANU, Canberrra Australien)

Wednesday 25 Mar 2015, 13:30 → 14:30 Europe/Stockholm

K-rummet (Q179) (Fysiska institutionen-Physics Department)

Nanowires offer potential applications for the next generation of electronics and photonics devices. III-V nanowires are successfully grown using two main techniques (i) the vapour-liquid-solid (VLS) technique with catalyst particles such as Au or self-catalysis with Ga in GaAs growth or (ii) selected area epitaxy (SAE). In this talk, I will give an overview of our recent work at the ANU on MOCVD grown III-V nanowires.
We present detailed transmission electron microscopy (TEM) and scanning transmission electron microscopy studies (STEM) of both III-V nanowires and core-shell nanowires grown by metal organic chemical vapour deposition (MOCVD). In particular, we concentrate on understanding the radial growth of Al_xGa_1-xAs shells grown radially on GaAs core nanowires. The core nanowires were grown using the Au-catalysed VLS technique by the two temperature growth method previously described [1]. Time-resolved photoluminescence studies of the best core shell nanowires show significant improvement in the carrier lifetime and the effectiveness of the AlGaAs shell to minimise surface recombination [2,3]. High angle annular dark field images of cross-sections of these core-shell nanowires show the presence of a GaAs core faceted along the {110} planes with a hexagonal shape, an Al_xGa_1-xAs shell showing similar faceting with intriguing radial Al rich bands along the {112} directions [4]. A trigonal symmetry involving these bands is revealed and discussed with regards to the polarity of the nanowire structure. The microstructure is discussed with regards to the remarkable optical properties of these nanowires. Other examples of polarity driven issues affecting the true morphology of the core nanowires [5], surfaces and interfaces in other III-V nanowires grown studied will also be discussed.
A brief overview of recent SAE growth analyses of InP nanowires [6] and VLS InGaAs grown core nanowires [7] will also be included.
[1] H. J. Joyce, Q. Gao, H. H. Tan, C. Jagadish, Y. Kim, X. Zhang, Y. N. Guo, and J. Zou, Nano Lett. 7, 921 (2007).
[2] N. Jiang, P. Parkinson,Q. Gao Q, H.H. Tan, J. Wong-Leung, C. Jagadish , Appl. Phys. Lett. 101, 023111 (2012).

[3] N. Jiang, Q. Gao, P. Parkinson, J. Wong-Leung, S. Mokkapati, S. Breuer, H. H. Tan, C. L. Zheng, J. Etheridge, and C. Jagadish, Nano Letters 13 (11), 5135-5140 (2013).

[4] C. Zheng, J. Wong-Leung, Q. Gao, H.H. Tan, C. Jagadish, and J. Etheridge, Nano Lett. 13 (8), 3742 (2013).
[5] Nian Jiang, Jennifer Wong-Leung, Hannah J. Joyce, Qiang Gao, Hark Hoe Tan, and Chennupati Jagadish, Nano Letters 14 (10), 5865-5872 (2014).
[6] Qian Gao, Dhruv Saxena, Fan Wang, Lan Fu, Sudha Mokkapati, Yanan Guo, Li Li, Jennifer Wong-Leung, Philippe Caroff, Hark Hoe Tan, and Chennupati Jagadish, Nano Lett. 14 (9), 5206-5211 (2014).
[7] Amira S. Ameruddin, H. Aruni Fonseka, Philippe Caroff, Jennifer Wong-Leung, Roy LM Op het Veld, Jessica L Boland, Michael B. Johnston, Hark Hoe Tan, and Chennupati Jagadish, submitted to Nanotechnology (2015).