Towards bipolar tin monoxide: Revealing unexplored dopants

Miglė Graužinytė, Stefan Goedecker, and José A. Flores-Livas

Phys. Rev. Materials 2, 104604 – Published 30 October 2018

Abstract

The advancement of transparent electronics, one of the most anticipated technological developments for the future, is currently inhibited by a shortage of high-performance $p$ -type semiconductors. Recent demonstration of tin monoxide as a successful transparent $p$ -type thin-film transistor and the discovery of its potential for ambipolar doping, suggests that tin monoxide—an environmentally friendly earth-abundant material—could offer a solution to this challenge. With the aim of enhancing the electronic properties, an extensive search for useful dopant elements was performed. Substitutional doping with the family of alkali metals was identified as a successful route to increase the concentration of acceptors in SnO and over ten shallow donors, which, to the best of our knowledge, have not been previously contemplated, were discovered. This work presents a detailed analysis of the most promising $n$ -/ $p$ -type dopants—offering new insights into the design of an ambipolar SnO. If synthesized successfully, such a doped ambipolar oxide could open new avenues for many transparent technologies.

Received 21 June 2018
Revised 28 August 2018

DOI:https://doi.org/10.1103/PhysRevMaterials.2.104604

Physics Subject Headings (PhySH)

Charge Density of states Dopants First-principles calculations Optoelectronics Point defects

Transparent conducting oxides

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Miglė Graužinytė^*, Stefan Goedecker, and José A. Flores-Livas^†

Department of Physics, Universität Basel, Klingelbergstr. 82, 4056 Basel, Switzerland

^*migle.grauzinyte@unibas.ch
^†jose.flores@unibas.ch

Article Text (Subscription Required)

Click to Expand

Supplemental Material (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand

Issue

Vol. 2, Iss. 10 — October 2018

Reuse & Permissions

Access Options

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
(Left) The electronic band structure of SnO (HSE06). Arrows show the indirect $(Γ \to M)$ and the direct $(Γ \to Γ)$ band gap. (Middle) The dependence of the indirect electronic energy gap (HSE06) on the lattice parameters of the litharge SnO. (Right) Nomenclature for the different doping sites in crystalline SnO. Oxygen atoms are represented in red, tin atoms in light-purple, yellow spheres highlight the defect sites.
Reuse & Permissions
Figure 2
PBE prescreening results for $p$ -type dopants in SnO. Geometric shapes indicate the energetically favored substitution of the two sites available. $D_{Sn}$ site is marked by a triangle, $D_{O}$ by a rectangle. The color of the shape indicates the charge state (stable when the Fermi level is at the VBM): rose—positive, yellow—neutral, blue—negative. For each element, the energy difference (in eV) between the two substitutional sites is indicated in the bottom right corner. The stable charge state of the alternative site is indicated by the small colored circle. Elements with thermodynamic transition levels to an acceptor state close to the VBM are indicated by a dashed outline. Elements with no stable $D_{Sn}$ substitution are shaded in gray.
Reuse & Permissions
Figure 3
Defect formation energies as a function of the Fermi level inside the band gap of SnO (HSE06). Left panel shows intrinsic defects in SnO, right panel shows the preselected $p$ -type dopants. Sn-rich conditions are assumed. Only the stable charge state is shown.
Reuse & Permissions
Figure 4
PBE prescreening results for $n$ -type dopants in SnO. Geometric shapes indicate the energetically favored substitution of the two sites available. $D_{Sn}$ site is marked by a triangle, $D_{O}$ by a rectangle. The color of the shape indicates the charge state (stable when the Fermi level is at the CBM): rose—positive, yellow—neutral, blue—negative. For each element, the energy difference (in eV) between the two substitutional sites is indicated in the bottom right corner. The stable charge state of the alternative site is indicated by the small colored circle. Elements with thermodynamic transition levels to a donor state close to the CBM are indicated by a dashed outline. Elements with no stable $D_{Sn}$ substitution are shaded in gray.
Reuse & Permissions
Figure 5
Defect formation energies as a function of the Fermi level for preselected $n$ -type dopants (obtained using the HSE06 xc functional). ${Vd}_{Sn}$ here stands for vanadium on a Sn site to avoid confusion with a tin vacancy. Sn-rich conditions are assumed. Only the stable charge state is shown.
Reuse & Permissions
Figure 6
Midgap electronic defects states of dopant elements in SnO. For donors, a charge state of $q = + 1$ is shown, except for tungsten $(q = + 2)$ . For acceptors, a charge state of $q = - 1$ is shown. Black lines indicate the energetic positions of defect states. For defect states close to the valence band, their occupation by spin is shown. Changes in valence and conduction band edges (after band alignment) of the host upon doping are indicated by the edges of the light green and sand colored areas, respectively. Bright blue areas shows the onset of the region below the optical band gap edge in which electronic defect states could not be distinguished. Differences in the spin channel occupation, for structures where spin polarized solutions were found, are indicated by the numbers at the top of the chart.
Reuse & Permissions

Physical Review Materials