Abstract van der Waals technology, since its creation in 2010, enabled the development of many ma... more Abstract van der Waals technology, since its creation in 2010, enabled the development of many materials, which never existed before, and led to the observation of numerous exciting physical phenomena. Here we present an overview of recent developments in the technology of two-dimensional (2D) crystals and their heterostructures and discuss novel physical phenomena observed in these artificial materials. We discuss the paradigm of tailor-made materials with properties on demand and overview novel phenomena in 2D nanomechanics, valleytronics, superconductivity, ferromagnetism, and novel topological states.
Despite a rich choice of two-dimensional materials, which exists these days, heterostructures, bo... more Despite a rich choice of two-dimensional materials, which exists these days, heterostructures, both vertical (van der Waals) and in-plane, offer an unprecedented control over the properties and functionalities of the resulted structures. Thus, planar heterostructures allow p-n junctions between different two-dimensional semiconductors and graphene nanoribbons with well-defined edges; and vertical heterostructures resulted in the observation of superconductivity in purely carbon-based systems and realisation of vertical tunnelling transistors. Here we demonstrate simultaneous use of in-plane and van der Waals heterostructures to build vertical single electron tunnelling transistors. We grow graphene quantum dots inside the matrix of hexagonal boron nitride, which allows a dramatic reduction of the number of localised states along the perimeter of the quantum dots. The use of hexagonal boron nitride tunnel barriers as contacts to the graphene quantum dots make our transistors reproduc...
— Resistance drift of the amorphous states of multilevel phase change memory (PCM) cells is curre... more — Resistance drift of the amorphous states of multilevel phase change memory (PCM) cells is currently a great challenge for the commercial implementation of a reliable multiple-bit-per-cell memory technology. This paper reports observation of a stable intermediate state for a multilevel PCM cell that is achieved through nonuniform heating with a square current injection top electrode. Drift coefficient of the intermediate state is an order of magnitude lower than reset and has weaker temperature dependence. Using finite-element simulations and an analytical model for the subthreshold current–voltage characteristics, based on thermally activated hopping of charge carriers across Coulombic donor-like traps, we conclude that the defect density is two orders of magnitude larger in the intermediate state. We attribute the low drift coefficient of the intermediate state to a large number of stable interfacial defects which dominate the electron transport. Current findings give way to a more stable ultrahigh-density PCM device. Index Terms— Multiple-bit-per-cell memory, phase change memory (PCM), resistance drift.
Abstract van der Waals technology, since its creation in 2010, enabled the development of many ma... more Abstract van der Waals technology, since its creation in 2010, enabled the development of many materials, which never existed before, and led to the observation of numerous exciting physical phenomena. Here we present an overview of recent developments in the technology of two-dimensional (2D) crystals and their heterostructures and discuss novel physical phenomena observed in these artificial materials. We discuss the paradigm of tailor-made materials with properties on demand and overview novel phenomena in 2D nanomechanics, valleytronics, superconductivity, ferromagnetism, and novel topological states.
Despite a rich choice of two-dimensional materials, which exists these days, heterostructures, bo... more Despite a rich choice of two-dimensional materials, which exists these days, heterostructures, both vertical (van der Waals) and in-plane, offer an unprecedented control over the properties and functionalities of the resulted structures. Thus, planar heterostructures allow p-n junctions between different two-dimensional semiconductors and graphene nanoribbons with well-defined edges; and vertical heterostructures resulted in the observation of superconductivity in purely carbon-based systems and realisation of vertical tunnelling transistors. Here we demonstrate simultaneous use of in-plane and van der Waals heterostructures to build vertical single electron tunnelling transistors. We grow graphene quantum dots inside the matrix of hexagonal boron nitride, which allows a dramatic reduction of the number of localised states along the perimeter of the quantum dots. The use of hexagonal boron nitride tunnel barriers as contacts to the graphene quantum dots make our transistors reproduc...
— Resistance drift of the amorphous states of multilevel phase change memory (PCM) cells is curre... more — Resistance drift of the amorphous states of multilevel phase change memory (PCM) cells is currently a great challenge for the commercial implementation of a reliable multiple-bit-per-cell memory technology. This paper reports observation of a stable intermediate state for a multilevel PCM cell that is achieved through nonuniform heating with a square current injection top electrode. Drift coefficient of the intermediate state is an order of magnitude lower than reset and has weaker temperature dependence. Using finite-element simulations and an analytical model for the subthreshold current–voltage characteristics, based on thermally activated hopping of charge carriers across Coulombic donor-like traps, we conclude that the defect density is two orders of magnitude larger in the intermediate state. We attribute the low drift coefficient of the intermediate state to a large number of stable interfacial defects which dominate the electron transport. Current findings give way to a more stable ultrahigh-density PCM device. Index Terms— Multiple-bit-per-cell memory, phase change memory (PCM), resistance drift.
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Papers by Servet Ozdemir