Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Coexistence of negative and positive photoconductivity in few-layer
  PtSe2 field-effect transistors   Platinum diselenide (PtSe_2) field-effect transistors with ultrathin channel
regions exhibit p-type electrical conductivity that is sensitive to temperature
and environmental pressure. Exposure to a supercontinuum white light source
reveals that positive and negative photoconductivity coexists in the same
device. The dominance of one type of photoconductivity over the other is
controlled by environmental pressure. Indeed, positive photoconductivity
observed in high vacuum converts to negative photoconductivity when the
pressure is rised. Density functional theory calculations confirm that
physisorbed oxygen molecules on the PtSe_2 surface act as acceptors. The
desorption of oxygen molecules from the surface, caused by light irradiation,
leads to decreased carrier concentration in the channel conductivity. The
understanding of the charge transfer occurring between the physisorbed oxygen
molecules and the PtSe_2 film provides an effective route for modulating the
density of carriers and the optical properties of the material.

13
The categories of this paper are: quant-ph
16
The categories of this paper are: stat
28
The categories of this paper are: alg-geom
10
The categories of this paper are: q-bio
3
The categories of this paper are: physics
19
The categories of this paper are: eess
27
The categories of this paper are: comp-gas
22
The categories of this paper are: chao-dyn
9
The categories of this paper are: nlin
21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
26
The categories of this paper are: bayes-an
30
The categories of this paper are: q-alg
0
The categories of this paper are: hep-ph
20
The categories of this paper are: acc-phys
14
The categories of this paper are: math-ph