Defect-controlled conductivity in As₂Se₃ single crystals

Pairing of Electrons by a Point Defect inc−As2Se3

“…At the growth temperature 650 K, 15 this results in 10 15±1 defects/cm 3 . However, it is important to note that it is difficult to prepare a crystal under precise stoichiometric conditions, so that either type of antisite may be more probable than the other.…”

“…Since the onefold-coordinated non-bonding orbital falls about midgap, the Fermi level should be pinned above midgap, in agreement with experiment. 15 Furthermore, there should be no paramagnetic centers associated with the pinning of the Fermi level. 16 On the other hand, if one had a material in which there are more As antisites than Se antisites, the Fermi level would be pinned below midgap at the As nonbonding level (Fig.…”

Computational prediction of high thermoelectric performance in As2Se3 by engineering out-of-equilibrium defects

“…6 However, very little has been done regarding the transport properties of its crystalline phase from the experimental point of view. [7][8][9] These experiments have shown very small electrical conductivity and the attempts to improve its thermoelectric properties by doping the material have failed because of the pinning of the Fermi level. 9 The understanding of these experimental results is highly desirable in order to attain a material for thermoelectric applications.…”

“…As 2 Se 3 is a semiconductor with a band gap of 2.0 eV. 12 The measurements of electrical conductivity [7][8][9] exhibit an Arrhenius behavior, indicating that carrier transport is a thermally activated process. The activation energies obtained from the experimental results are similar, however, the measured values of the electrical conductivity showed large variation among the experiments.…”

“…13 Aside from that, the similar behavior of different samples indicates that these defects cannot arise from accidental impurities. 9 Thus, antisites have been considered to be the predominant point defects in the material. These defects can be thermally created, that means that, even under strict stoichiometric conditions, at finite temperature there would be an equilibrium concentration of these defects, which are created in pairs.…”