Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Stabilization of amorphous GaN by oxygen   Ion assisted deposition (IAD) has been investigated for the growth of GaN,
and the resulting films studied by x-ray diffraction and absorption
spectroscopy and by transmission electron microscopy. IAD grown stoichiometric
GaN consists of random-stacked quasicrystals of some 3 nm diameter. Amorphous
material is formed only by incorporation of 15% or more oxygen, which we
attribute to the presence of non-tetrahedral bonds centered on oxygen. The
ionic favourability of heteropolar bonds and its strikingly simple constraint
to even-membered rings is the likely cause of the instability of stoichiometric
a-GaN.

3
The categories of this paper are: physics
2
The categories of this paper are: math
26
The categories of this paper are: bayes-an
24
The categories of this paper are: dg-ga
20
The categories of this paper are: acc-phys
32
The categories of this paper are: atom-ph
12
The categories of this paper are: nucl-th
29
The categories of this paper are: funct-an
33
The categories of this paper are: plasm-ph
28
The categories of this paper are: alg-geom
19
The categories of this paper are: eess
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-fin
30
The categories of this paper are: q-alg
16
The categories of this paper are: stat