Donald B Rogers

Bio: Donald B Rogers is an academic researcher from DuPont. The author has contributed to research in topics: Scheelite & Bismuth. The author has an hindex of 12, co-authored 20 publications receiving 1683 citations.

The transition metal dichalcogenides discussion and interpretation of the observed optical, electrical and structural properties

Abstract: The transition metal dichalcogenides are about 60 in number. Two-thirds of these assume layer structures. Crystals of such materials can be cleaved down to less than 1000 A and are then transparent in the region of direct band-to-band transitions. The transmission spectra of the family have been correlated group by group with the wide range of electrical and structural data available to yield useful working band models that are in accord with a molecular orbital approach. Several special topics have arisen; these include exciton screening, d-band formation, and the metal/insulator transition; also magnetism and superconductivity in such compounds. High pressure work seems to offer the possibility for testing the recent theory of excitonic insulators.

P-type electrical conduction in transparent thin films of CuAlO2

Abstract: Optically transparent oxides tend to be electrical insulators, by virtue of their large electronic bandgap (⩾3.1 eV). The most notable exceptions are doped versions of the oxides In2O3, SnO2 and ZnO—all n-type (electron) conductors—which are widely used as the transparent electrodes in flat-panel displays1,2. On the other hand, no transparent oxide exhibiting high p-type (hole) conductivity is known to exist, whereas such materials could open the way to a range of novel applications. For example, a combination of the two types of transparent conductor in the form of a pn junction could lead to a ‘functional’ window that transmits visible light yet generates electricity in response to the absorption of ultraviolet photons. Here we describe a strategy for identifying oxide materials that should combine p-type conductivity with good optical transparency. We illustrate the potential of this approach by reporting the properties of thin films of CuAlO2, a transparent oxide having room-temperature p-type conductivity up to 1 S cm−1. Although the conductivity of our candidate material is significantly lower than that observed for the best n-type conducting oxides, it is sufficient for some applications, and demonstrates that the development of transparent p-type conductors is not an insurmountable goal.

Crystal structures and elastic properties of superhard IrN2 and IrN3 from first principles

Abstract: First principles calculations were performed to investigate the structural, elastic, and electronic properties of IrN2 for various space groups: cubic Fm-3m and Pa-3, hexagonal P3(2)21, tetragonal P4(2)/mnm, orthorhombic Pmmn, Pnnm, and Pnn2, and monoclinic P2(1)/c. Our calculation indicates that the P2(1)/c phase with arsenopyrite-type structure is energetically more stable than the other phases. It is semiconducting (the remaining phases are metallic) and contains diatomic N-N with the bond distance of 1.414 A. These characters are consistent with the experimental facts that IrN2 is in lower symmetry and nonmetallic. Our conclusion is also in agreement with the recent theoretical studies that the most stable phase of IrN2 is monoclinic P2(1)/c. The calculated bulk modulus of 373 GPa is also the highest among the considered space groups. It matches the recent theoretical values of 357 GPa within 4.3% and of 402 GPa within 7.8%, but smaller than the experimental value of 428 GPa by 14.7%. Chemical bonding and potential displacive phase transitions are discussed for IrN2. For IrN3, cubic skutterudite structure (Im-3) was assumed.