Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Structural characterization of as-grown and quasi-free standing graphene
  layers on SiC   We report on a comparative structural characterization of two types of high
quality epitaxial graphene layers grown by CVD on 4H-SiC(0001). The layers
under study are a single layer graphene on top of a buffer layer and a
quasi-free-standing graphene obtained by intercalation of hydrogen underneath
the buffer layer. We determine the morphology and structure of both layers by
different complementary in-situ and ex-situ surface techniques. We found the
existence of large islands in both samples but with different size
distribution. Photoemission electron microscopy (PEEM) measurements were
performed to get information about the chemical environment of the different
regions. The study reveals that monolayer graphene prevails in most of the
surface terraces, while a bilayer and trilayer graphene presence is observed at
the steps, stripes along steps and islands.

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The categories of this paper are: math-ph
32
The categories of this paper are: atom-ph
5
The categories of this paper are: gr-qc
37
The categories of this paper are: supr-con
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The categories of this paper are: plasm-ph
11
The categories of this paper are: hep-lat
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The categories of this paper are: solv-int
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The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
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The categories of this paper are: quant-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: stat
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The categories of this paper are: q-fin