International audienceWe report a study of resistive switching in a silicon-based memristor/resistive RAM (RRAM)device in which the active layer is silicon-rich silica. The resistive switching phenomenon is anintrinsic property of the silicon-rich oxide layer and does not depend on the diffusion of metallicions to form conductive paths. In contrast to other work in the literature, switching occurs inambient conditions, and is not limited to the surface of the active material. We propose a switchingmechanism driven by competing field-driven formation and current-driven destruction offilamentary conductive pathways. We demonstrate that conduction is dominated by trap assistedtunneling through noncontinuous conduction paths consisting of silicon nanoinclusions in a highlynonstoichiometric suboxide phase. We hypothesize that such nanoinclusions nucleate preferentiallyat internal grain boundaries in nanostructured films. Switching exhibits the pinched hysteresis I/Vloop characteristic of memristive systems, and on/off resistance ratios of 104:1 or higher can beeasily achieved. Scanning tunneling microscopy suggests that switchable conductive pathways are10 nm in diameter or smaller. Programming currents can be as low as 2 lA, and transition timesare on the nanosecond scale

Resistive switching offers a promising route to universal electronic memory, potentially replacing current technologies that are approaching their fundamental limits. In many cases switching originates from the reversible formation and dissolution of nanometre-scale conductive filaments, which constrain the motion of electrons, leading to the quantisation of device conductance into multiples of the fundamental unit of conductance, G0. Such quantum effects appear when the constriction diameter approaches the Fermi wavelength of the electron in the medium – typically several nanometres. Here we find that the conductance of silicon-rich silica (SiOx) resistive switches is quantised in half-integer multiples of G0. In contrast to other resistive switching systems this quantisation is intrinsic to SiOx, and is not due to drift of metallic ions. Half-integer quantisation is explained in terms of the filament structure and formation mechanism, which allows us to distinguish between systems that exhibit integer and half-integer quantisation.

Resistive switching in a metal-free silicon-based material offers a compelling alternative to existing metal oxide-based resistive RAM (ReRAM) devices, both in terms of ease of fabrication and of enhanced device performance. We report a study of resistive switching in devices consisting of non-stoichiometric silicon-rich silicon dioxide thin films. Our devices exhibit multi-level switching and analogue modulation of resistance as well as standard two-level switching. We demonstrate different operational modes that make it possible to dynamically adjust device properties, in particular two highly desirable properties: nonlinearity and self-rectification. This can potentially enable high levels of device integration in passive crossbar arrays without causing the problem of leakage currents in common line semi-selected devices. Aspects of conduction and switching mechanisms are discussed, and scanning tunnelling microscopy (STM) measurements provide a more detailed insight into both the location and the dimensions of the conductive filaments.

International audienceInAs quantum-dot (QD) laser structures are grown on (113)B-oriented InP substrate by gas-source molecular-beam epitaxy. Following an optimized growth procedure, a high density of 1.1×1011 cm−2 of uniformly sized QDs is achieved. Broad-area lasers containing three stacked QD layers have been realized and tested. Laser emission on the ground-state transition (λ = 1.59 μm) is obtained at room temperature (RT), at a threshold current density as low as 190 A/cm2. Ground-state modal gain and transparency current density is measured to be 7 cm−1 and 23 A/cm2 per dot layer. Ground-state laser emission is also demonstrated from low temperature (100 K, Jth = 33 A/cm2) to high temperature (350 K), exhibiting an insensitive threshold in the [100, 170] K range, and a 55 K characteristic temperature at RT

Luminescent hybrid copolymers are obtained by copolymerizing in bulk methylmethacrylate with a methacrylic acid (MAC) solution containing [n‐Bu4N]2[Mo6Br8(MAC)6], and aliquots of an Er(TMHD)3 complex (TMHD for 2,2,6,6‐tetramethyl‐3,5‐heptanedione) solution. This leads to novel homogeneous and transparent hybrid materials in which the Er3+ infrared luminescence at 1.55 μm, a standard wavelength for telecommunication applications, is up to six time more intense in the presence of Mo6 clusters when samples are irradiated at 476.5 nm. This work demonstrates the outstanding potential of Mo6 clusters, compounds obtained by high‐temperature solid‐state synthesis, in the design of functional hybrid materials via soft chemistry routes.

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It has been shown recently that the perovskite oxide SrVO3 is a transparent conductor with optical and electrical properties outreaching those of the most used material indium tin oxide (ITO). These properties, observed in the crystalline phase, imply the strong potential of SrVO3 for use as a lower cost alternative to ITO, but the possible integration of this perovskite oxide material in actual electronic devices is still an open question. One of the possible approaches for the integration of oxide materials is the use of amorphous thin films, allowing low thermal budgets to preserve the performances of the electronic device. Therefore, in this study, the electrical and optical properties of amorphous or poorly crystallized thin SrVO3 films are investigated.

of SVO as a TCO is the fact that although the charge density is that of typical metals (in the range of 10 22 cm −3 ), the screened plasma frequency ω p is pushed out of the visible range due to the strong electronic correlations enhancing the effective mass m*. Consequently, the electronic correlations do not only govern the electronic transport properties, but also the optical ones in the visible range.Such interplay between the electronic and optical properties via the electronic correlations may also open a new way for the optimization of the functional properties of SVO. In strongly correlated metals, it is known that strain may influence the correlation characteristics via the related crystal distortions, [3][4][5] which were also predicted theoretically for SVO. [6,7] In a strongly correlated TCO as SVO, it may therefore be possible to not only influence the electrical transport by strain, but also the optical properties. Although the structural and electronic properties of SVO were studied intensely in the thin film [8][9][10][11][12] or in superlattices form, [10,13] no comparative study of SVO films on different substrates inducing variation of strain was published, neither its influence on the optical properties. The aim of this study is therefore to use three substrates, on which epitaxial growth of SVO is possible, in order to elucidate the influence of the strain on both the electronic and the optical properties.However, in the discussion of the relationship between structure and properties in transition metal oxide thin films, the stoichiometry of the films has also to be taken into account. Especially in SVO, it has been shown that both a cationic [9] as also an anionic nonstoichiometry [11,12,14,15] play an important role in the properties. The management of the oxygen content is a special issue in SVO due to the existence of some oxides with higher oxidation state of vanadium such as Sr 3 V 2 O 8 or Sr 2 V 2 O 7 , being thermodynamically more stable than the perovskite structure. [16] This implies that widely used mechanisms to influence on the oxygen stoichiometry of thin films, as the growth in different oxygen pressures or postannealing treatments, are not possible or have to be controlled closely in order to avoid the formation of the orthovanadate, which is transparent but insulating. Even more, recently it has been shown in a closely related system, SrCoO 3 , that strain and oxygen vacancies show a complex interplay: [17] in films undergoing a tensile strain, the density of oxygen vacancies is enhanced, The vanadate SrVO 3 is a transparent conductor perovskite with optical and electrical properties competing with those of the most-used indium tin oxide material. Although its charge density is comparable to that of metals, SrVO 3 shows a plasma frequency below the visible range due to strong electronic correlations characterizing the electronic transport in this material and enhancing the effective mass. Therefore, the well-known interplay between the structure and the electronic properties...