University of North Texas

Quantum Devices, Inc.

Sandia Corporation

Jeffry A Kelber

Peter A Dowben

Christian Binek

Scott A Chambers

Kirill D Belashchenko

Dwight R Jennison

Alexander Bogicevic

Jipu Lei

Mi Zhou

Noel P Magtoto

Peter Arnold Bowden

Sergei Rudenja

Sneha Sen Gaddam

Cameron L Bjelkevig

Manufacturable spin and spin-polaron interconnects are disclosed that do not exhibit the same increase in resistivity shown by Cu interconnects associated with decreasing linewidth. These interconnects rely on the transmission of spin as opposed to charge. Two types of graphene based interconnect approaches are explored, one involving the injection and diffusive transport of discrete spin-polarized carriers, and the other involving coherent spin polarization of graphene charge carriers due to exchange interactions with localized substrate spins. Such devices are manufacturable as well as scalable (methods for their fabrication exist, and the interconnects are based on direct growth, rather than physical transfer or metal catalyst formation). Performance at or above 300 K, as opposed to cryogenic temperatures, is the performance criteria.

Manufacturable spin and spin-polaron interconnects

Graphene FETs exhibit low power consumption and high switching rates taking advantage of the excellent mobility in graphene deposited on a rocksalt oxide (111) by chemical vapor deposition, plasma vapor deposition or molecular beam epitaxy. A source, drain and electrical contacts are formed on the graphene layer. These devices exhibit band gap phenomena on the order of greater than about 0.5 eV, easily high enough to serve as high speed low power logic devices. Integration of this construction technology, based on the successful deposition of few layer graphene on the rocksalt oxide (111) with SI CMOS is straightforward.

Graphene field effect transistor

Direct growth of graphene on CoO(111) at 1000 K was achieved by molecular beam epitaxy from a graphite source. Auger spectroscopy shows a characteristic spcarbon lineshape, at average carbon coverages from 0.4-3 monolayers. Low energy electron diffraction (LEED) indicates (111) ordering of the spcarbon film with a lattice constant of 2.5 (&#xb1;0.1) &#x212b; characteristic of graphene. Six-fold symmetry of the graphene diffraction spots is observed at 0.4, 1 and 3 monolayers. The LEED data also indicate an average domain size of &#x2dc;1800 &#x212b;, and show an incommensurate interface with the CoO(111) substrate, where the latter exhibits a lattice constant of 2.8 (&#xb1;0.1) &#x212b;. Core level photoemission shows a characteristically asymmetric C(1s) feature, with the expected lr to lr* satellite feature, but with a binding energy for the three monolayer film of 284.9 (&#xb1;0.1) eV, indicative of substantial graphene-to-oxide charge transfer.

Direct graphene growth on metal oxides by molecular epitaxy

A voltage switchable coherent spin field effect transistor is provided by depositing a ferromagnetic base like cobalt on a substrate. A chrome oxide layer is formed on the cobalt by MBE at room at UHV at room temperature. There was thin cobalt oxide interface between the chrome oxide and the cobalt. Other magnetic materials may be employed. A few ML field of graphene is deposited on the chrome oxide by molecular beam epitaxy, and a source and drain are deposited of base material. The resulting device is scalable, provides high on/off rates, is stable and operable at room temperature and easily fabricated with existing technology.

Coherent spin field effect transistor

A coherent spin field effect transistor is provided by depositing a ferromagnetic base like cobalt on a substrate. A magnetic oxide layer is formed on the cobalt by annealing at temperatures on the order of 1000&#xb0; K to provide a few monolayer thick layer. Where the gate is cobalt, the resulting magnetic oxide is CoO(111). Other magnetic materials and oxides may be employed. A few ML field of graphene is deposited on the cobalt (III) oxide by molecular beam epitaxy, and a source and drain are deposited of base material. The resulting device is scalable, provides high on/off rates, is stable and operable at room temperature and easily fabricated with existing technology.

A Tunnel Magnetic Junction of high magnetoresistance is prepared at temperatures and pressure consistent with Si CMOS fabrication and operation. A first metal layer of cobalt or nickel is grown on an interconnect or conductive array line of e.g., copper. The metal layer is formed by electron beam irradiation. Annealing at UHV at temperatures below 700K yields a carbon segregation that forms a few layer thick (average density 3.5 ML) graphene film on the metal layer. Formation of a second layer of metal on top of the graphene barrier layer yields a high performance MTJ.

Graphene magnetic tunnel junction spin filters and methods of making

The invention relates to a magneto-electric spin-FET including a gate film of chromia and a thin film of a conductive channel material which may be graphene, InP, GaAs, GaSb, PbS, MoS, WS, MoSe, WSeand mixtures thereof. The chromia, or other magneto-electric, and conduction channel material are in intimate contact along an interface there between. The resulting magneto-electric device may be voltage-controlled and provide non-volatile memory.

Magneto-electric voltage controlled spin transistors

We have demonstrated controlled growth of epitaxial h-BN on a metal substrate using atomic layer deposition. This permits the fabrication of devices such as vertical graphene transistors, where the electron tunneling barrier, and resulting characteristics such as ON-OFF rate may be altered by varying the number of epitaxial layers of h-BN. Few layer graphene is grown on the h-BN opposite the metal substrate, with leads to provide a vertical graphene transistor that is intergratable with Si CMOS technology of today, and can be prepared in a scalable, low temperature process of high repeatability and reliability.

Controlled epitaxial boron nitride growth for graphene based transistors

Boron carbide polymers prepared from orthocarborane icosahedra cross-linked with a moiety A wherein A is selected from the group consisting of benzene, pyridine. 1,4-diaminobenzene and mixtures thereof give positive magnetoresistance effects of 30%-80% at room temperature. The novel polymers may be doped with transitional metals to improve electronic and spin performance. These polymers may be deposited by any of a variety of techniques, and may be used in a wide variety of devices including magnetic tunnel junctions, spin-memristors and non-local spin valves.

Boron carbide films exhibits extraordinary magnetoconductance and devices based thereon

Novel semiconducting polymers have been formed via the electron-induced cross-linking of orthocarborane B10C2H2 and 1,4-diaminobenzene. The films were formed by co-condensation of the molecular precursors and 200 eV electron-induced cross-linking under ultra-high vacuum (UHV) conditions. Ultraviolet photoemission spectra show that the compound films display a shift of the valence band maximum from &#x2dc;4.3 eV below the Fermi level for pure boron carbide to &#x2212;1.7 eV below the Fermi level when diaminobenzene is added. The surface photovoltage effect decreases with decreasing B/N atomic ratio. A neutron detector comprises the polymer as the p-type semiconductor to be paired with an n-type semiconductor.

Semiconducting alloy polymers formed from orthocarborane and 1,4-diaminobenzene

A voltage switchable non-local spin-FET is disclosed which provides a layer of chromia over a ferromagnetic substrate, such as cobalt. A film of graphene overlays the chromia, with a protective layer of metal oxide like cobalt oxide or iron oxide there between to prevent catalytic degradation of the graphene, which may occur. The graphene is provided with a contact, or source and drain, depending on the application. The spin-FET, which exhibits magnetic remanence, may be provided with a top gate of, e.g., cobalt or other ferromagnet such as iron. As an alternative to the ferromagnetic substrate, the device may be formed on a silicon or gallium arsenide base, or directly on a metal interconnect of an integrated circuit.

Voltage switchable non-local spin-FET and methods for making same

Disclosed is a substrate-mediated assembly for graphene structures. According to an embodiment, long-range ordered, multilayer BN(111) films can be formed by atomic layer deposition (ALD) onto a substrate. The subject BN(111) films can then be used to order carbon atoms into a graphene sheet during a carbon deposition process.

Graphene (multilayer) boron nitride heteroepitaxy for electronic device applications

Methods of forming a graphene-based device are provided. According to an embodiment, a graphene-based device can be formed by subjecting a substrate having a dielectric formed thereon to a chemical vapor deposition (CVD) process using a cracked hydrocarbon or a physical vapor deposition (PVD) process using a graphite source; and performing an annealing process. The annealing process can be performed to temperatures of 1000 K or more. The cracked hydrocarbon of the CVD process can be cracked ethylene. In accordance with one embodiment, the application of the cracked ethylene to a MgO(111) surface followed by an annealing under ultra high vacuum conditions can result in a structure on the MgO(111) surface of an ordered graphene film with an oxidized carbon-containing interfacial layer therebetween. In another embodiment, the PVD process can be used to form single or multiple monolayers of graphene.

Growing community of inventors

Plano, TX, United States of America

Jeffry A Kelber