Abstract
Establishing ultimate spin current efficiency in graphene over industry-standard substrates can facilitate research and development exploration of spin current functions and spin sensing. At the same time, it can resolve core issues in spin relaxation physics while addressing the skepticism of graphene’s practicality for planar spintronic applications. In this work, we reveal an exceptionally long spin communication capability of 45 μm and highest to date spin diffusion length of 13.6 μm in graphene on SiO2/Si at room temperature. Employing commercial chemical vapor deposited (CVD) graphene, we show how contact-induced surface charge transfer doping and device doping contributions, as well as spin relaxation, can be quenched in extremely long spin channels and thereby enable unexpectedly long spin diffusion lengths in polycrystalline CVD graphene. Extensive experiments show enhanced spin transport and precession in multiple longest channels (36 and 45 μm) that reveal the highest spin lifetime of ∼2.5–3.5 ns in graphene over SiO2/Si, even under ambient conditions. Such performance, made possible due to our devices approaching the intrinsic spin–orbit coupling of ∼20 μeV in graphene, reveals the role of the D’yakonov–Perel’ spin relaxation mechanism in graphene channels as well as contact regions. Our record demonstration, fresh device engineering, and spin relaxation insights unlock the ultimate spin current capabilities of graphene on SiO2/Si, while the robust high performance of commercial CVD graphene can proliferate research and development of innovative spin sensors and spin computing circuits.
Highlights
Establishing ultimate spin current efficiency in graphene over industry-standard substrates can facilitate research and development exploration of spin current functions and spin sensing
For more than a decade, research in graphene spintronics has shown several advancements, with some top reports displaying a spin diffusion length of ∼10 μm, in the single-crystalline exfoliated graphene built on atomically flat hexagonal boron nitride substrates.[6,8,9]
We demonstrate a record-high performance in commercial chemical vapor deposited (CVD) graphene by investigating multiple longdistance devices fabricated on standard SiO2/Si substrates
Summary
Establishing ultimate spin current efficiency in graphene over industry-standard substrates can facilitate research and development exploration of spin current functions and spin sensing. Spin diffusion lengths λ of ∼7−9 μm and spin lifetimes τ of ∼2−3 ns were reported in special CVD graphene grown over a Pt substrate.[12] This performance is higher than the previously obtained best values in CVD graphene grown on Cu substrates.[3] It has been reported that a platinum substrate facilitates high-temperature (1100 °C) nucleation and crystallization, resulting in millimeter-sized CVD graphene crystals.[13] Large single-crystalline domains could eliminate grain-boundary defects and scattering that could lead to higher spin lifetimes in the nanosecond regime, as observed in highquality exfoliated graphene heterostructures[6,8,9] or singlecrystalline CVD graphene[14] devices.
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