A Hard Oxide Semiconductor with A Direct and Narrow Bandgap and Switchable p–n Electrical Conduction

Abstract

An oxide semiconductor (perovskite-type Mn2 O3 ) is reported which has a narrow and direct bandgap of 0.45 eV and a high Vickers hardness of 15 GPa. All the known materials with similar electronic band structures (e.g., InSb, PbTe, PbSe, PbS, and InAs) play crucial roles in the semiconductor industry. The perovskite-type Mn2 O3 described is much stronger than the above semiconductors and may find useful applications in different semiconductor devices, e.g., in IR detectors.

Dramatic Changes in Thermoelectric Power of Germanium under Pressure: Printing n–p Junctions by Applied Stress

“…1d). Using a standard expression for absorption edges in semiconductors with nearly parabolic energy bands, as follows25: (where α is the absorption coefficient, α 0 is a constant, E is the energy, C is an instrumental shift, and n ∼ 1 / 2 and ∼ 2 for direct and indirect band gaps, respectively), we established the direct band gap as of 0.8 eV (Fig. 1d).…”

“…For instance, it has been established that conventional silicon, slightly doped with Ge (of ~1–3 at.%) acquires the pronounced properties of a ‘smart’ material and enables a simple and elegant p–n switching of its electrical conduction type by applied stress up to 3 GPa24. A recently discovered perovskite-type ζ -Mn 2 O 3 semiconductor with a direct band gap of 0.45 eV also demonstrated a possibility of p–n switching under applied high pressure above 10–15 GPa25. Whereas, undoped silicon and other semiconductors for optoelectronics, such as GaAs, ZnSe and ZnTe did not reveal such effects26272829.…”

Strategies and challenges of high-pressure methods applied to thermoelectric materials

“…However, this is a challenging requirement for high-pressure studies. To date, several different types of cells or setups combining electrical and thermoelectric measurements have been devised, [45][46][47][48][49][50][51][52][53] and techniques that enable measurements of all relevant thermoelectric properties under the same conditions have been recently developed. 4,5,[54][55][56] All of these methods have their merits and limitations, but in any case there is still a need for more refined and accurate techniques.…”

Spin-induced multiferroicity in the binary perovskite manganite Mn2O3

“…Recently, the first binary perovskite oxide, Mn 2 O 3 , was synthesized under high-pressure and high-temperature (HP-HT) conditions 11,12 . It is worth mentioning that it was found by a single-crystal X-ray diffraction technique that Fe 2 O 3 also adopts a perovskite structure at HP-HT conditions being, however, not quenchable to ambient pressure 13 .…”

“…The Mn cations show variable charge states (e.g., Mn 2+ , Mn 3+ , and Mn 4+ ) with ionic radii, and, in particular, the Mn 2+ cation is sufficiently large to be accommodated in the A -position of the perovskite structure. Using synchrotron X-ray diffraction (SXRD), electron diffraction, annular bright-field scanning transmission electron microscopy (ABF-STEM), and electron energy loss spectroscopy (EELS) 11,12 , we demonstrated that the perovskite-type Mn 2 O 3 can be represented as (Mn 2+ Mn 3+ 3 )Mn 3.25+ 4 O 12 , given different oxidation states of Mn depending on the crystallographic position.…”