Fermi Level

Mixing Mg with Ti leads to a hydride Mg(x)Ti(1-x)H2 with markedly improved (de)hydrogenation properties for x < 0.8, as compared to MgH2. Optically, thin films of Mg(x)Ti(1-x)H2 have a black appearance, which is remarkable for a hydride material. In this paper we study the structure and stability of Mg(x)Ti(1-x)H2, x= 0-1 by first-principles calculations at the level of density functional theory. We give evidence for a fluorite to rutile phase transition at a critical composition x(c)= 0.8-0.9, which correlates with the experimentally observed sharp decrease in (de)hydrogenation rates at this composition. The densities of states of Mg(x)Ti(1-x)H2 have a peak at the Fermi level, composed of Ti d states. Disorder in the positions of the Ti atoms easily destroys the metallic plasma, however, which suppresses the optical reflection. Interband transitions result in a featureless optical absorption over a large energy range, causing the black appearance of Mg(x)Ti(1-x)H2.

In this paper, a two-dimensional electron gas (2DEG) charge-control model for carrier density in the channel is developed for a separated double-gate high-electron-mobility transistor. The model is extended to calculate Id-Vg characteristics of the device. The drain current model uses a polynomial dependence of sheet carrier concentration on the position of a quasi-Fermi energy level to predict the modulation of back carrier concentration due to a front gate bias. The characteristics are investigated for various channel thicknesses and delta doping concentrations in order to study the effect of the back gate on the overall device performance. The analytical results so obtained are verified by comparing them with simulated and experimental results. A good agreement between the results is obtained, thus validating the model.

ABSTRACT We have studied the Fermi surface of copper by angle-resolved photoemission for photon energies between 95.37 and 259.6 eV. Fermi surface images were obtained by scanning the polar emission angle as well as the photon energy while monitoring the photoemission intensity at the Fermi level. Such images are distorted because of the non-conservation of the perpendicular k component in photoemission. However, if the scans are performed such that the k steps parallel to the surface are identical for all photon energies, the distortion can be corrected for using appropriate final states, for example free-electron final states. We find reasonable agreement between our results and the well-known Fermi surface of copper.

D. Takeuchi*, 1, 2, S.-G. Ri1, 2, H. Kato1, 2, CE Nebel1, and S. Yamasaki1, 2 1 Diamond Research Center, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan 2 CREST, Japan Science and Technology ...

Mixing Mg with Ti leads to a hydride Mg(x)Ti(1-x)H2 with markedly improved (de)hydrogenation properties for x < 0.8, as compared to MgH2. Optically, thin films of Mg(x)Ti(1-x)H2 have a black appearance, which is remarkable for a hydride material. In this paper we study the structure and stability of Mg(x)Ti(1-x)H2, x= 0-1 by first-principles calculations at the level of density functional theory. We give evidence for a fluorite to rutile phase transition at a critical composition x(c)= 0.8-0.9, which correlates with the experimentally observed sharp decrease in (de)hydrogenation rates at this composition. The densities of states of Mg(x)Ti(1-x)H2 have a peak at the Fermi level, composed of Ti d states. Disorder in the positions of the Ti atoms easily destroys the metallic plasma, however, which suppresses the optical reflection. Interband transitions result in a featureless optical absorption over a large energy range, causing the black appearance of Mg(x)Ti(1-x)H2.