Journal
NANO LETTERS
Volume 11, Issue 2, Pages 866-871Publisher
AMER CHEMICAL SOC
DOI: 10.1021/nl104265u
Keywords
Nanostructures; nanowires; nucleation and growth; nitrides; molecular beam epitaxy
Categories
Funding
- ONR [N00014-09-1-1153]
- Ohio State University Institute for Materials Research
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Bottom-up nanostructure assembly has been a central theme of rnaterials synthesis over the past few decades. Semiconductor quantum dots and nanowires provide additional degrees of freedom for charge confinement strain engineering, and surface sensitivity properties that are useful to a wide range of solid state optical and electronic technologies. A central challenge is to understand and manipulate nanostructure assembly to reproducibly generate emergent structures with the desired properties. However, progress is hampered due to the interdependence of nucleation, and growth phenomena. Here we show that by dynamically adjusting the growth kinetics, it is possible to separate the nucleation and growth processes in spontaneously formed GaN nanowires using a two-step molecular beam epitaxy technique. First, a growth phase diagram for these nanowires is systematically developed, which allows for control of nanowire density over three orders of magnitude. Next, we show that by first nucleating nanowires at a low temperature and then growing them at a higher temperature, height and density can be independently selected while maintaining the target density over long growth times. GaN nanowires prepared using this two-step procedure are overgrown with three-dimensionally layered and topologically complex heterostructures of (GaN/AIN). By adjusting the growth temperature in the second growth step either vertical or coaxial nanowire superlattices can be formed. These results indicate that a two-step method allows access to a variety of kinetics at which nanowire nucleation and adatom mobility are adjustable.
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