Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A setup for the study of surface processes under external homogeneous
  electric fields   A setup for studying the influence of external electric fields on dynamic
surface processes is described. Spatially-extended homogeneous electric fields
are realized by applying a DC voltage in between a planar electrode and a
metallic substrate, which are separated by a narrow vacuum gap. The functional
capability of the device is demonstrated by recording the field-emission
characteristic as a function of the applied field up to 2.3 V/nm, revealing
proper Fowler-Nordheim tunneling behavior.

28
The categories of this paper are: alg-geom
9
The categories of this paper are: nlin
10
The categories of this paper are: q-bio
16
The categories of this paper are: stat
37
The categories of this paper are: supr-con
14
The categories of this paper are: math-ph
23
The categories of this paper are: solv-int
2
The categories of this paper are: math
31
The categories of this paper are: ao-sci
36
The categories of this paper are: cmp-lg
26
The categories of this paper are: bayes-an
32
The categories of this paper are: atom-ph
18
The categories of this paper are: econ
34
The categories of this paper are: chem-ph
0
The categories of this paper are: hep-ph
25
The categories of this paper are: patt-sol