In spite of its excellent electronic properties, the use of graphene in field-effect transistors is not practical at room temperature without modification of its intrinsically semimetallic nature to introduce a bandgap. Quantum confinement effects can create a bandgap in graphene nanoribbons, but existing nanoribbon fabrication methods are slow and often produce disordered edges that compromise electronic properties. Here, we demonstrate the self-organized growth of graphene nanoribbons on a templated silicon carbide substrate prepared using scalable photolithography and microelectronics processing. Direct nanoribbon growth avoids the need for damaging post-processing. Raman spectroscopy, high-resolution transmission electron microscopy and electrostatic force microscopy confirm that nanoribbons as narrow as 40 nm can be grown at specified positions on the substrate. Our prototype graphene devices exhibit quantum confinement at low temperatures (4 K), and an on-off ratio of 10 and carrier mobilities up to 2,700 cm(2) V(-1) s(-1) at room temperature. We demonstrate the scalability of this approach by fabricating 10,000 top-gated graphene transistors on a 0.24-cm(2) SiC chip, which is the largest density of graphene devices reported to date.

The ultimate surface exposure provided by graphene monolayer makes it the ideal sensor platform but also exposes its intrinsic properties to any environmental perturbations. In this work, we demonstrate that the charge carrier density of graphene exfoliated on a SiO2/Si substrate can be finely and reversibly tuned between hole and electron doping with visible photons. This photo-induced doping happens under moderate laser power conditions but is significantly affected by the substrate cleaning method. In particular, it requires hydrophilic substrates and vanishes for suspended graphene. These findings suggest that optically gated graphene devices operating with a sub-second time scale can be envisioned and that Raman spectroscopy is not always as non-invasive as generally assumed.

Ever since the first observation of all-optical switching of magnetization in the ferrimagnetic alloy GdFeCo using femtosecond laser pulses, there has been significant interest in exploiting this process for data-recording applications. in particular, the ultrafast speed of the magnetic reversal can enable the writing speeds associated with magnetic memory devices to be potentially pushed towards tHz frequencies. this work reports the development of perpendicular magnetic tunnel junctions incorporating a stack of tb/co nanolayers whose magnetization can be all-optically controlled via helicity-independent single-shot switching. toggling of the magnetization of the tb/co electrode was achieved using either 60 femtosecond-long or 5 picosecond-long laser pulses, with incident fluences down to 3.5 mJ/cm 2 , for co-rich compositions of the stack either in isolation or coupled to a cofeBelectrode/Mgo-barrier tunnel-junction stack. Successful switching of the cofeB-[tb/co] electrodes was obtained even after annealing at 250 °c. After integration of the [tb/co]-based electrodes within perpendicular magnetic tunnel junctions yielded a maximum tunneling magnetoresistance signal of 41% and RxA value of 150 Ωμm 2 with current-in-plane measurements and ratios between 28% and 38% in nanopatterned pillars. these results represent a breakthrough for the development of perpendicular magnetic tunnel junctions controllable using single laser pulses, and offer a technologically-viable path towards the realization of hybrid spintronic-photonic systems featuring tHz switching speeds. Ferrimagnetic systems based on rare earth (RE)-transition metal (TM) alloys and multilayers have been extensively studied in recent decades, largely due to their potential application in the field of magneto-optical recording 1. The strong perpendicular magnetocrystalline anisotropy inherent to amorphous RE-TM systems have allowed these alloys to play a key role in the historical transition from longitudinal to perpendicular magnetic recording structures 2 , and made them ideal for handling magnetic bit instabilities arising from superparamagnetic effects 3. Binary and ternary RE-TM systems such as GdFeCo, GdCo, TbCo or GdFe are still driving forward new developments pertaining to spintronic devices, including spin valves for magnetic read heads 4 , perpendicular magnetic tunnel junctions (p-MTJs) 5,6 or spin-orbit-torque phenomena 7. Recent works in this field have also revealed that RE-TM-based films (amorphous or multilayered) represent ideal materials for the observation and study of the phenomena of all-optical switching (AOS) 8-10. In these systems, it is possible to switch the magnetization using suitable laser pulses without the application of any external magnetic field. Depending on whether the laser-pulses need to be circularly-polarized, AOS of magnetization can be classed as either helicity-dependent (HD-AOS) or helicity-independent (HI-AOS). Furthermore, subject to the material in question, the switching process can be achieved with either a...