11 research outputs found
Nanosecond spin lifetimes in bottom-up fabricated bilayer graphene spin-valves with atomic layer deposited AlO spin injection and detection barriers
We present spin transport studies on bi- and trilayer graphene non-local
spin-valves which have been fabricated by a bottom-up fabrication method. By
this technique, spin injection electrodes are first deposited onto
Si/SiO substrates with subsequent mechanical transfer of a
graphene/hBN heterostructure. We showed previously that this technique allows
for nanosecond spin lifetimes at room temperature combined with carrier
mobilities which exceed 20,000 cm/(Vs). Despite strongly enhanced spin and
charge transport properties, the MgO injection barriers in these devices
exhibit conducting pinholes which still limit the measured spin lifetimes. We
demonstrate that these pinholes can be partially diminished by an oxygen
treatment of a trilayer graphene device which is seen by a strong increase of
the contact resistance area products of the Co/MgO electrodes. At the same
time, the spin lifetime increases from 1 ns to 2 ns. We believe that the
pinholes partially result from the directional growth in molecular beam
epitaxy. For a second set of devices, we therefore used atomic layer deposition
of AlO which offers the possibility to isotropically deposit more
homogeneous barriers. While the contacts of the as-fabricated bilayer graphene
devices are non-conductive, we can partially break the oxide barriers by
voltage pulses. Thereafter, the devices also exhibit nanosecond spin lifetimes.Comment: 6 pages, 4 figure
Spin lifetimes exceeding 12 nanoseconds in graphene non-local spin valve devices
We show spin lifetimes of 12.6 ns and spin diffusion lengths as long as 30.5
\mu m in single layer graphene non-local spin transport devices at room
temperature. This is accomplished by the fabrication of Co/MgO-electrodes on a
Si/SiO substrate and the subsequent dry transfer of a graphene-hBN-stack on
top of this electrode structure where a large hBN flake is needed in order to
diminish the ingress of solvents along the hBN-to-substrate interface.
Interestingly, long spin lifetimes are observed despite the fact that both
conductive scanning force microscopy and contact resistance measurements reveal
the existence of conducting pinholes throughout the MgO spin
injection/detection barriers. The observed enhancement of the spin lifetime in
single layer graphene by a factor of 6 compared to previous devices exceeds
current models of contact-induced spin relaxation which paves the way towards
probing intrinsic spin properties of graphene.Comment: 8 pages, 5 figure
Nanosecond spin lifetimes in single- and few-layer graphene-hBN heterostructures at room temperature
We present a new fabrication method of graphene spin-valve devices which
yields enhanced spin and charge transport properties by improving both the
electrode-to-graphene and graphene-to-substrate interface. First, we prepare
Co/MgO spin injection electrodes onto Si/SiO. Thereafter, we
mechanically transfer a graphene-hBN heterostructure onto the prepatterned
electrodes. We show that room temperature spin transport in single-, bi- and
trilayer graphene devices exhibit nanosecond spin lifetimes with spin diffusion
lengths reaching 10m combined with carrier mobilities exceeding 20,000
cm/Vs.Comment: 15 pages, 5 figure
Nanosecond spin lifetimes in bottom-up fabricated bilayer graphene spin-valves with atomic layer deposited Al2O3 spin injection and detection barriers
Nanosecond spin lifetimes in bottom-up fabricated bilayer graphene spin-valves with atomic layer deposited Al2O3 spin injection and detection barriers
Localized recrystallization and cracking of lead-free solder interconnections under thermal cycling â ERRATUM
Thermal sprayed aluminum coatings A199 and AlSi12 on carbon fiber reinforced magnesium-alloy AZ91 for integration in aluminum-cast processes
Cast aluminum materials have limited strength and stiffness and tend to brittle fracture behavior under fatigue loading. For the significant increase of these material properties, the reinforcement of cast aluminum materials by the integration of carbon fiber-reinforced magnesium structures (magnesium based metal matrix composites - Mg-MMC) was investigated within this work. In order to obtain a bond between the cast aluminum and Mg-MMC, thermally sprayed functional coatings based on aluminum alloys (A199 and AlSi12) were used in both high velocity oxy fuel spraying (HVOF) and atmospheric plasma spraying processes (APS). The mechanical properties of the bonding were studied in single-lap shear and adhesive tensile tests, accompanied by optical microsection analyses. In order to evaluate and investigate the requested composite concept, the hybrid casting integration of coated Mg-MMC structures in the alumina alloy AlSi10Mg was examined on a test specimen level and on a generic component
Localized recrystallization and cracking of lead-free solder interconnections under thermal cycling
Nanosecond Spin Lifetimes in Single- and Few-Layer GrapheneâhBN Heterostructures at Room Temperature
We present a new fabrication method
of graphene spin-valve devices
that yields enhanced spin and charge transport properties by improving
both the electrode-to-graphene and graphene-to-substrate interface.
First, we prepare Co/MgO spin injection electrodes onto Si<sup>++</sup>/SiO<sub>2</sub>. Thereafter, we mechanically transfer a grapheneâhBN
heterostructure onto the prepatterned electrodes. We show that room
temperature spin transport in single-, bi-, and trilayer graphene
devices exhibit nanosecond spin lifetimes with spin diffusion lengths
reaching 10 ÎŒm combined with carrier mobilities exceeding 20â000
cm<sup>2</sup>/(V s)