Semiconductor Spintronics

Spintronics refers commonly to phenomena in which the spin of electrons in a solid state environment plays the determining role. In a more narrow sense spintronics is an emerging research field of electronics: spintronics devices are based on a spin control of electronics, or on an electrical and optical control of spin or magnetism. This review presents selected themes of semiconductor spintronics, introducing important concepts in spin transport, spin injection, Silsbee-Johnson spin-charge coupling, and spindependent tunneling, as well as spin relaxation and spin dynamics. The most fundamental spin-dependent nteraction in nonmagnetic semiconductors is spin-orbit coupling. Depending on the crystal symmetries of the material, as well as on the structural properties of semiconductor based heterostructures, the spin-orbit coupling takes on different functional forms, giving a nice playground of effective spin-orbit Hamiltonians. The effective Hamiltonians for the most relevant classes of materials and heterostructures are derived here from realistic electronic band structure descriptions. Most semiconductor device systems are still theoretical concepts, waiting for experimental demonstrations. A review of selected proposed, and a few demonstrated devices is presented, with detailed description of two important classes: magnetic resonant tunnel structures and bipolar magnetic diodes and transistors. In most cases the presentation is of tutorial style, introducing the essential theoretical formalism at an accessible level, with case-study-like illustrations of actual experimental results, as well as with brief reviews of relevant recent achievements in the field.Comment: tutorial review; 342 pages, 132 figure

Abstraction of sulfur from Pt(111) surfaces with thermal H atoms toward adsorbed and gaseous H2S

Sulphur layers on Pt(1 1 1) surfaces with coverages of 0.25 and 0.33 were prepared by H2S adsorption at 85 K and subsequent annealing. If,S adsorption on Pt, S/Pt and H/Pt surfaces and S adsorbate layers were characterized by Auger electron and thermal desorption spectroscopies. Admission of thermal H atoms to S covered Pt(I 1 1) at 85 K leads to formation of gaseous (80%) as well as adsorbed H2S (20%). The yield of adsorbed H2S decreases due to its isothermal desorption above 90 K. The interaction of H(g) with S(a) involves three reaction steps: 1. H(g) + S(a) --> SH(a), 2. H (9) + SH(a) --> H2S(g, a), and 3. H(g) + SH(a) --> H,(g) + S(a) with apparent cross-sections sigma = 0.3 Angstrom(2), sigma(2) = 0.6 Angstrom(2) and sigma(3) = 0.03 Angstrom(2). Above 140 K the hydrogenation of SH toward H2S(a,g) is blocked by thermal decomposition of H2S. Impact of D on coadsorbed S, SH, and H'S leads to desorption of H2S. (C) 2002 Elsevier Science B.V. All rights reserved

Abstraction of sulfur from Pt(111) surfaces with thermal H atoms toward adsorbed and gaseous H2S

Sulphur layers on Pt(1 1 1) surfaces with coverages of 0.25 and 0.33 were prepared by H2S adsorption at 85 K and subsequent annealing. If,S adsorption on Pt, S/Pt and H/Pt surfaces and S adsorbate layers were characterized by Auger electron and thermal desorption spectroscopies. Admission of thermal H atoms to S covered Pt(I 1 1) at 85 K leads to formation of gaseous (80%) as well as adsorbed H2S (20%). The yield of adsorbed H2S decreases due to its isothermal desorption above 90 K. The interaction of H(g) with S(a) involves three reaction steps: 1. H(g) + S(a) --> SH(a), 2. H (9) + SH(a) --> H2S(g, a), and 3. H(g) + SH(a) --> H,(g) + S(a) with apparent cross-sections sigma = 0.3 Angstrom(2), sigma(2) = 0.6 Angstrom(2) and sigma(3) = 0.03 Angstrom(2). Above 140 K the hydrogenation of SH toward H2S(a,g) is blocked by thermal decomposition of H2S. Impact of D on coadsorbed S, SH, and H'S leads to desorption of H2S. (C) 2002 Elsevier Science B.V. All rights reserved

Orientation and interface effects on the structural and magnetic properties of MnAs-on-GaAs hybrid structures

MnAs grows either with the $(1\bar {1}00)$prism-plane on GaAs(001), (113)A and (110) or the (0001) $c$-plane on GaAs(111)B substrates. The strain state of the films determines the phase coexistence of ferromagnetic $\alpha$- and paramagnetic $\beta$-MnAs and their distribution in self-organized structures. The mismatch accommodation mechanisms along the $a$-axis of $\alpha$-MnAs are in principle the same for all substrate orientations, while they are very different along the $c$-axis. Depending on the orientation the Curie temperature can exceed the value for bulk MnAs