Patent Application: US-201514606085-A

Abstract:
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 . performance at or above 300 k , as opposed to cryogenic temperatures , is the performance criteria .

Description:
various embodiments will be described in detail with reference to the accompanying drawings . the structures illustrated in the drawings are renderings not photomicrographs . they are intended to be illustrative , not limiting . in contrast , the data of fig2 - 4 is verified , and relied on to demonstrate projected performance . spin diffusion vs . spin polaron transport spin interconnect structures are fabricated as shown in fig5 . these manufacturable structures demonstrate spin transport by two different methods . the most direct approach , as in fig5 a , b , involves the injection / diffusion of discrete spins through graphene [ 4 , 11 - 16 ]. the interconnects illustrate the degree to which such discrete spin transport is affected by both spin diffusion vs . length ( l , fig5 a )) and potential sidewall scattering for decreasing linewidths ( w , fig5 a ), in comparison with existing models [ 7 ]. an alternative inventive approach herein to spin transport involves spin polaron formation [ 9 , 17 ]. coherent spin polarization and transport can arise from strong rkky - type exchange interactions between delocalized carriers and localized spins on metal cations , as in cdte / mn + 2 quantum wells [ 9 , 17 ] and , apparently , in graphene / co 3 o 4 / co structures ( fig4 ) [ 10 ]. because the basic phenomenon here is uniform graphene carrier polarization , rather than injection / diffusion of discrete spins , such structures may exhibit more uniform scaling vs . l and w , without l dependent polarization characteristic of discrete spin diffusion [ 6 ], and without sidewall - induced scattering characteristic of discrete spin transport . ( 1 ) spin injection / diffusion : graphene / bn / ru ( or w ) heterostructures ( fig5 a ) graphene / bn / ru heterostructures are readily manufacturable , based on our existing results using ald to form the bn single layer [ 1 ] or multilayers [ 18 ], on ru , followed by graphene cvd [ 2 ]. literature results [ 19 ] also suggest the viability of mbe or pvd . tungsten affords a cmos - compatible alternative to ru , with potentially useful interfacial chemical interactions and effects on graphene properties . ( 2 ) spin injection / diffusion — integration with sio2 / si ( 100 ) ( fig5 b ) the demonstrated ability to grow ( 111 )- oriented co 3 o 4 on sio 2 / sio ( 100 ) by pecvd [ 20 ] provides a direct route towards the integration of spin interconnects and related structures with si cmos . this structure would still operate by tunneling injection / diffusion of discrete spins , although graphene carrier / co ion rkky - type interactions [ 10 ] may also be observed . ( 3 ) magnetic polaron formation / transport with substrate gating . ( fig5 c ) graphene / bn / fm (= co , ni , fe ) heterojunctions should exhibit strong interfacial orbital hybridization and charge transfer [ 1 , 21 , 22 ], with important consequences for substrate - induced bn and graphene magnetic behavior [ 23 , 24 ], including uninform polarization of graphene charge carriers and coherent magnetic polaron spin transport . such behavior ( without interfacial orbital hybridization ) has been demonstrated for graphene / co 3 o 4 / co structures [ 10 ] and likely will also be observed for graphene on other magnetic oxides such as chromia and alumina . such structures will be fabricated by established methods [ 2 , 18 , 19 ]. these devices will rely on spin transport ( magnetoresistance ) behavior for longer l and smaller w , and we here demonstrate how spin polaron transport scales in a manner fundamentally different from discrete spin injection / diffusion . spin transport in this structure may be gated by the ferromagnetic substrate , which would permit switching between different states with large and small magnetoresistance , leading to hybrid interconnect / device structures without analogy in si - cmos architecture . fabrication of these heterojunctions is accompanied by characterization using an array of surface science methods , including low energy electron diffraction ( leed ), raman , core and valence band photoemission ( xps , ups ), and scanning tunneling microscopy / spectroscopy ( stm / sts ). basic magnetic behavior is also be probed by magneto - optic kerr effect ( moke ) measurements . interconnect structures with varying l and w ( e . g ., fig5 a ) are then produced , coupled with sem / tem characterization , and conductivity measurements . magnetoresistance measurements , coupled with spin - polarized photoemission / inverse photoemission studies will similarly be conducted . previous experience showing that graphene - covered heterostructures are largely inert towards ambient exposure for periods of several weeks or longer , makes this invention possible . incorporation of the interconnect structures permitting shipment of samples between fabrication facilities and assembly points . initially , as reflected in fig5 a and fig5 b — interconnects readily manufacturable based on existing results are made , and spin transport measurements are taken to determine magneto - resistance scaling as a function of interconnect length and width . decreased conductivity with decreasing w is expected [ 7 ]. various graphene / bn or magnetic oxides / co heterostructures ( fig5 c ), including the possibility of co substrate “ gating ” of interconnect performance is explored as well . scaling of magnetoresistance with interconnect behavior is compared to results for structures involving spin tunneling injection and diffusion demonstrating improved performance for the heterostructures of the invention . structures are then optimized for spin transmission at and above room temperature , and comparisons are made of switching , power usage , durability , and other factors , with variations in structure and interface chemistry as predicted by previous results . 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