Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dislocation-free axial InAs-on-GaAs nanowires on silicon   We report on the growth of axial InAs-on-GaAs nanowire heterostructures on
silicon by molecular beam epitaxy using 20 nm diameter Au catalysts. First, the
growth parameters of the GaAs nanowire segment were optimized to achieve a pure
wurtzite crystal structure. Then, we developed a two-step growth procedure to
enhance the yield of vertical InAs-on-GaAs nanowires. We achieved 90% of
straight InAs-on-GaAs nanowires by further optimizing the growth parameters. We
investigated the composition change at the interface by energy dispersive X-ray
spectroscopy and the nanowire crystal structure by transmission electron
microscopy. The nominal composition of the InAs segment is found to be
In$_{x}$Ga$_{1-x}$As with $x$=0.85 and corresponds to 6% of lattice mismatch
with GaAs. Strain mapping performed by the geometrical phase analysis of
high-resolution images revealed a dislocation-free GaAs/InAs interface. In
conclusion, we successfully fabricated highly mismatched heterostructures,
confirming the prediction that axial GaAs/InAs interfaces are pseudomorphic in
nanowires below 40 nm diameter.

18
The categories of this paper are: econ
3
The categories of this paper are: physics
36
The categories of this paper are: cmp-lg
19
The categories of this paper are: eess
10
The categories of this paper are: q-bio
2
The categories of this paper are: math
25
The categories of this paper are: patt-sol
6
The categories of this paper are: astro-ph
9
The categories of this paper are: nlin
33
The categories of this paper are: plasm-ph
20
The categories of this paper are: acc-phys
14
The categories of this paper are: math-ph
13
The categories of this paper are: quant-ph
21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
15
The categories of this paper are: nucl-ex