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Dec 28, 2010

New High Temperature Transistor

Electronic spin transport (spin transport electronics), electronics, based on their backs (spin-based electronics), or simply a spin-electronics (spin-electronics). In our time exploring spintronics, magnetic and magneto-optical interaction in semiconductor structures, dynamics and coherence properties of spins in condensed matter and quantum magnetic phenomena in nanometer-scale structures Currently, active work on the creation of magnetic semiconductors, which would satisfy all the requirements of spintronics.First, the materials of which will be produced spintronic elements, should not change their properties under the influence of humidity, pressure and temperature. Secondly, they must be "powerful", for example, to allow application of ohmic contacts and to be integrated with modern silicon electronics.
Third, the central question of spintronics is the question of the spin coherence. If this time is too small, the disorientation of the spins leads to a loss of information carried by each spin. Fourth, the materials used must have high charge carrier mobility and be ferromagnetic at room temperature.

The semiconductor spintronics, in contrast to spintronics "organ metallic" largely satisfies the above requirements. Unique physical properties of magnetic semiconductors due to the presence in their band structure of the singular the third zone, which is formed by electronic d-and f-shells of the atoms of transition or rare earth elements. Currently, there is an intensive search for new ferromagnetic semiconductors with a high Curie temperature Nano wires are optically transparent semiconductors II, VI groups, such as CdS, CdSe, ZnS, have been well studied because of their unique optical properties. Doping with transition metals such as nanowires would manage their optical properties with the magnetic field.

To date, synthesize various metal-oxide nanowires are doped with transition metals such as Mn, Co, Ni. Nanowires of magnetic semiconductors p-and n-types on the basis of Zn1-xMxO (where M = Mn, Co, Ni) opens the possibility of creating a bipolar spin transistor. To create such a realistic device indicates ferromagnetic nanowires Zn1-xMxO, grown by CVD. It is due to indirect exchange interaction due to spin transfer mobile carriers - holes and electrons. Based on the nanowires TiO2, doped with cobalt, and on the basis nanokabelya type of core-shell ZnO/Zn1-xCoxO can be created by spin-FET (spin field-effect transistor - a spin field-effect transistor).

Magnetic conductors III, V groups are well studied, both theoretically and experimentally. The most famous are the diluted magnetic semiconductors based on gallium arsenide doped with Mn. Manganese was the most suitable magnetic impurity due to its high solubility, and diffusion capacity. To date, magnetic semiconductors with TC ~ 160 K, based on p-(Ga1-xMnx) As. In wide-gap materials p-(Ga, Mn) P, and p-and n-(Ga, Mn) N ferromagnetism observed at temperatures above room temperature. The magnetic and magneto transport properties of nanowires Ga1-xMnxP and Ga1-xMnxN, grown by CVD, showed that the nanowires are
magnetically hard ferromagnetic with Curie temperature TC = 330 K, in addition, the magneto resistance of the wire is negative. On the basis of MP III, V groups have already created a prototype
spin-FET and spin-LED (spin light-emitting diode - spin LED).

In the spin-FET source and drain are ferromagnetism, connected by a narrow semiconductor channel. The spins of electrons injected into the semiconductor, are set parallel to the magnetization source. Thus, from its source to the drain flowing spin-polarized current. If the drain and source are magnetized in one direction, that is between them an electric current. In the spin-LED spin-polarized carriers are injected from the contact, combined with composite materials such as nanowires Ga1-xMnxN. Spin-LED can be used to transmit information using the spin-codes. Emitting light of a certain polarization depending on the orientation of the spin, spin-LED allows you to encode the information carried by polarized light. Mentioned devices require the nanoscale wires to implement them.

Along with the nanowires on the basis of magnetic semiconductors creates a thin magnetic film, a practical interest in which is due to the fact that the method of lithographs of them can be prepared ordered ensembles of nanostructures that are used to store information. To date, the technique of production and certification of nanocomposites containing ordered arrays of ferromagnetic semiconductor nanowires in anodized aluminum oxide membranes. This technique allows obtaining the inverse images of microchips based on oriented nanowires with an easily adjustable and reliably reproducible geometrical parameters of the elementary memory cells.

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