title: Crystal Orientation Controlled Photovoltaic Properties of Multilayer GaAs Nanowire Arrays.
abstract: In recent years, despite significant progress in the synthesis, characterization, and integration of various nanowire (NW) material systems, crystal orientation controlled NW growth as well as real-time assessment of their growth-structure-property relationships still presents one of the major challenges in deploying NWs for practical large-scale applications. In this study, we propose, design, and develop a multilayer NW printing scheme for the determination of crystal orientation controlled photovoltaic properties of parallel GaAs NW arrays. By tuning the catalyst thickness and nucleation and growth temperatures in the two-step chemical vapor deposition, crystalline GaAs NWs with uniform, pure ⟨110⟩ and ⟨111⟩ orientations and other mixture ratios can be successfully prepared. Employing lift-off resists, three-layer NW parallel arrays can be easily attained for X-ray diffraction in order to evaluate their growth orientation along with the fabrication of NW parallel array based Schottky photovoltaic devices for the subsequent performance assessment. Notably, the open-circuit voltage of purely ⟨111⟩-oriented NW arrayed cells is far higher than that of ⟨110⟩-oriented NW arrayed counterparts, which can be interpreted by the different surface Fermi level pinning that exists on various NW crystal surface planes due to the different As dangling bond densities. All this indicates the profound effect of NW crystal orientation on physical and chemical properties of GaAs NWs, suggesting the careful NW design considerations for achieving optimal photovoltaic performances. The approach presented here could also serve as a versatile and powerful platform for in situ characterization of other NW materials.
authors.affiliation: State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences , Beijing, 100190, People's Republic of China.|Center for Excellence in Urban Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences , Xiamen 361021, People's Republic of China.
authors.forename: Ning
authors.initials: N
authors.lastname: Han
authors.affiliation: Department of Physics and Materials Science, City University of Hong Kong , Kowloon, Hong Kong, People's Republic of China.|State Key Laboratory of Millimeter Waves, City University of Hong Kong , Kowloon, Hong Kong, People's Republic of China.|Shenzhen Research Institute, City University of Hong Kong , Shenzhen, 518057, People's Republic of China.
authors.forename: Zai-Xing
authors.initials: ZX
authors.lastname: Yang
authors.affiliation: Cultivation Base for State Key Laboratory, Qingdao University , Qingdao, 266071, People's Republic of China.
authors.forename: Fengyun
authors.initials: F
authors.lastname: Wang
authors.affiliation: Department of Physics and Materials Science, City University of Hong Kong , Kowloon, Hong Kong, People's Republic of China.|State Key Laboratory of Millimeter Waves, City University of Hong Kong , Kowloon, Hong Kong, People's Republic of China.|Shenzhen Research Institute, City University of Hong Kong , Shenzhen, 518057, People's Republic of China.
authors.forename: SenPo
authors.initials: S
authors.lastname: Yip
authors.affiliation: Department of Physics and Materials Science, City University of Hong Kong , Kowloon, Hong Kong, People's Republic of China.|Shenzhen Research Institute, City University of Hong Kong , Shenzhen, 518057, People's Republic of China.
authors.forename: Dapan
authors.initials: D
authors.lastname: Li
authors.affiliation: Department of Physics and Materials Science, City University of Hong Kong , Kowloon, Hong Kong, People's Republic of China.
authors.forename: Tak Fu
authors.initials: TF
authors.lastname: Hung
authors.affiliation: State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences , Beijing, 100190, People's Republic of China.|Center for Excellence in Urban Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences , Xiamen 361021, People's Republic of China.
authors.forename: Yunfa
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Physics and Materials Science, City University of Hong Kong , Kowloon, Hong Kong, People's Republic of China.|State Key Laboratory of Millimeter Waves, City University of Hong Kong , Kowloon, Hong Kong, People's Republic of China.|Shenzhen Research Institute, City University of Hong Kong , Shenzhen, 518057, People's Republic of China.
authors.forename: Johnny C
authors.initials: JC
authors.lastname: Ho
keywords: GaAs nanowire; Schottky contact; X-ray diffraction; contact printing; orientation; photovoltaic