High-energy-spectroscopy studies of a charge-transfer insulator: X-ray spectra of α-Fe2O3

Effect of defects on the small polaron formation and transport properties of hematite from first-principles calculations

“…We first optimized the initial geometry of pristine hematite with a variable cell relaxation which obtained cell parameters of a = 5.13Å and c = 13.99Å with bond lengths and angles of Fe-O = 1.99, 2.14Å, O-Fe-O = 90.7, 86.0, 78.6 • , which agree well with other work in both experiment [16] and theory [17]. The pristine structure and fundamental values that we obtained are collected in Table I Hematite is a charge transfer insulator [20,21] and in accordance with the strong correlation of electrons in 3d orbitals we apply the Hubbard correction [22] to the Fe 3d orbitals in the form of Eq.1. Here, E DFT is the energy obtained from standard Density Functional Theory methods which is corrected by the following term which includes the occupation matrix λ Iσ i (I ranges over all Fe ions, i ranges over 3d orbitals and σ is for spin up or down).…”

Electronic structures of iron(III) and manganese(IV) (hydr)oxide minerals: Thermodynamics of photochemical reductive dissolution in aquatic environments

“…In the solid state physics literature, these minerals are viewed as "charge-transfer insulators" as opposed to "Mott insulators" (e.g., Drager et al, 1992). To a chemist, this means that the band gap corresponds to a ligand-to-metal charge-transfer (LMCT) transition, O(2p) ¡Fe(3d) or O(2p) ¡Mn(3d).…”

Controlled p- and n-type doping of Fe2O3 nanobelt field effect transistors

“…Therefore, the electron concentration is estimated to be n = 1.59ϫ 10 8 cm −1 , which corresponds to a bulk concentration of 5.3ϫ 10 18 cm −3 , and the mobility is calculated to be e = 2.8ϫ 10 −3 cm 2 /V s. The native n-type behavior for semiconducting metaloxide nanostructures, such as ZnO and In 2 O 3 nanobelts, has been well documented and attributed to the oxygen vacancies. 6,8 Although in some context, ␣-Fe 2 O 3 is regarded as a charge-transfer insulator, 9 it tends to be an n-type semiconductor in the presence of oxygen vacancies. 10 In addition, ␣-Fe 2 O 3 has demonstrated its peculiar behavior of the n-to p-type transition under certain conditions due to its narrower band gap ͑E g = 2.2 eV͒ compared with In 2 O 3 ͑E g = 3.6 eV͒ and ZnO ͑E g = 3.4 eV͒.…”