Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Strain evolution in GaN Nanowires: from free-surface objects to
  coalesced templates   Top-down fabricated GaN nanowires, 250 nm in diameter and with various
heights, have been used to experimentally determine the evolution of strain
along the vertical direction of 1-dimensional objects. X-ray diffraction and
photoluminescence techniques have been used to obtain the strain profile inside
the nanowires from their base to their top facet for both initial compressive
and tensile strains. The relaxation behaviors derived from optical and
structural characterizations perfectly match the numerical results of
calculations based on a continuous media approach. By monitoring the elastic
relaxation enabled by the lateral free-surfaces, the height from which the
nanowires can be considered strain-free has been estimated. Based on this
result, NWs sufficiently high to be strain-free have been coalesced to form a
continuous GaN layer. X-ray diffraction, photoluminescence and
cathodoluminescence clearly show that despite the initial strain-free nanowires
template, the final GaN layer is strained.

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The categories of this paper are: math
28
The categories of this paper are: alg-geom
12
The categories of this paper are: nucl-th
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The categories of this paper are: astro-ph
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The categories of this paper are: q-fin
23
The categories of this paper are: solv-int
32
The categories of this paper are: atom-ph
33
The categories of this paper are: plasm-ph
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
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The categories of this paper are: physics
5
The categories of this paper are: gr-qc
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The categories of this paper are: nlin
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The categories of this paper are: math-ph
37
The categories of this paper are: supr-con
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The categories of this paper are: chem-ph