Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the Origin of the Two-Dimensional Electron Gas at the CdO (100)
  Surface   Synchrotron-radiation angle-resolved and core-level photoemission
spectroscopy are used together to investigate the origin of the two-dimensional
electron gas on the surface of single crystal CdO (100) films. A reduction in
the two-dimensional electron density of the surface state is observed under the
synchrotron beam during ARPES, which is shown to be accompanied by a
concomitant reduction in the surface-adsorbed species (monitored through the O
1s core level signal). This shows that surface adsorbates donate electrons into
the surface accumulation layer. When the surface is cleaned, the surface
conduction band state empties. A surface doped with atomic H is also studied.
Here, interstitial H increases the two-dimensional electron density at the
surface. This demonstrates that reversible donor doping is possible. The
surface band bending profiles, 2D electron densities, and effective masses are
calculated from subband dispersion simulations.

34
The categories of this paper are: chem-ph
2
The categories of this paper are: math
16
The categories of this paper are: stat
5
The categories of this paper are: gr-qc
9
The categories of this paper are: nlin
31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
13
The categories of this paper are: quant-ph
22
The categories of this paper are: chao-dyn
11
The categories of this paper are: hep-lat
27
The categories of this paper are: comp-gas
0
The categories of this paper are: hep-ph
15
The categories of this paper are: nucl-ex
10
The categories of this paper are: q-bio
7
The categories of this paper are: hep-th
32
The categories of this paper are: atom-ph