We report a theoretical study of the spectral statistics of a quasi-one-dimensional surface superlattice in perpendicularly applied magnetic fields. The energylevel-spacing distribution and the Dyson-Mehta 3 statistic of the magnetic band structure of the system are calculated. The calculations show that for the system with inversion symmetry, the magnetic band structure at the wave vector k = 0 is well described by the statistic derived by a superposition of two independent Gaussian orthogonal ensemble (GOE) statistics. This result is consistent with the fact that the system shows a false time-reversal violation and a real-space symmetry. The calculations show also that when the wave vector k is moved away from the k = 0 point, the statistical properties of the magnetic band structure are excellently described by the GOE statistics. The GOE statistics are also found in the magnetic band structure when the inversion symmetry is removed from the system.
As-deposited films were prepared on sapphire substrates at 500 -680 C by alternately sputtering Cu and Al targets in Ardiluted O 2 gas atmosphere. The composition of the as-deposited films corresponded to that of the slightly oxygen-rich region of the CuO-CuAl 2 O 4 -Al 2 O 3 system. The films as-deposited at 500 C had an amorphous structure, while the films asdeposited at 680 C had CuAl 2 O 4 phase but no CuAlO 2 phase. Annealing at 1050 C in nitrogen flow caused a reduction in the molar fraction of oxygen, i.e., the composition of the annealed films with [Cu]=[Al] % 1 corresponded to CuAlO 2 . The annealed films were predominated by the CuAlO 2 phase. The preferential orientation of the films toward the c-axis normal to the substrate surface is due to the small lattice mismatch between the rhombohedral [010] of delafossite-type CuAlO 2 and the hexagonal [1 1100] of the sapphire substrate. The annealed films had an absorption edge corresponding to the energy gap of CuAlO 2 and exhibited p-type conductivity.
A planar mtallization process has been proposed, where contact windows or via holes of a high aspect ratio are refilled with tungsten by selective CVD employing wF6. In tungsten selective CVD, an appropriate choice of substrate material and surface cleaning prior to tungsten deposition is a key factor to success. For selective deposition onto A l , Al surface is coated with p.loSi2 thin layer, and contact resistivities of refilling tungsten with n+ Si and WSi2 coated Al are comparable to those of conventional Al metallization. Combining a interlevel insulator surface planarization process and a planar metallization process, a tri-level aluminum interconnection process of 1 micron feature size has been constructed, which has a scheme extensive to submicron feature size.
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