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.
Micro-structuration of rare-earth-doped materials by lift-off processing of pulsed laser deposited layers are promising in integrated optics, since they do not require complex processing. However, ...they are so far limited to Y
2
O
3
host and have never been reported for infrared emission, which have many applications in telecommunication, sensing and so on. In this work, we have studied micro-devices made by pulsed laser deposition combined to lift-off processing on Si, with Er-doped materials that have infrared emission at 1.54 µm wavelength, corresponding to the
4
I
1 3/2
→
4
I
1 5/2
Er
3+
transition. Two host materials have been compared: Al
2
O
3
commonly used in integrated optics and Y
2
O
3
, which is a well-known crystalline host for rare earth doping. For both materials, micro-photoluminescence measurements combined with X-ray diffraction showed efficient incorporation of Er
3+
ions into the host matrix, associated with strong emission when the matrix is amorphous for Al
2
O
3
or crystalline for Y
2
O
3
. Thus, this work extends the pulsed laser deposition lift-off processing to other materials and wavelength range, which opens the way of easy realization of infrared micro-emitter for photonics applications.
Exceptional points (EPs), singularities of non-Hermitian physics where complex spectral resonances degenerate, are one of the most exotic features of nonequilibrium open systems with unique ...properties. For instance, the emission rate of quantum emitters placed near resonators with EPs is enhanced (compared to the free-space emission rate) by a factor that scales quadratically with the resonance quality factor. Here, we verify the theory of spontaneous emission at EPs by measuring photoluminescence from photonic-crystal slabs that are embedded with a high-quantum-yield active material. While our experimental results verify the theoretically predicted enhancement, they also highlight the practical limitations on the enhancement due to material loss. Our designed structures can be used in applications that require enhanced and controlled emission, such as quantum sensing and imaging.
We demonstrate that symmetry breaking opens a new degree of freedom to tailor energy-momentum dispersion in photonic crystals. Using a general theoretical framework in two illustrative practical ...structures, we show that breaking symmetry enables an on-demand tuning of the local density of states of the same photonic band from zero (Dirac cone dispersion) to infinity (flatband dispersion), as well as any constant density over an adjustable spectral range. As a proof of concept, we demonstrate experimentally the transformation of the very same photonic band from a conventional quadratic shape to a Dirac dispersion, a flatband dispersion, and a multivalley one. This transition is achieved by finely tuning the vertical symmetry breaking of the photonic structures. Our results provide an unprecedented degree of freedom for optical dispersion engineering in planar integrated photonic devices.
Epitaxial PbZr
Ti
O
(PZT) layers were integrated on Si(001) with single PZT {001} orientation, mosaïcity below 1° and a majority of a-oriented ferroelectric domains (∼65%). Ferroelectric and ...pyroelectric properties are determined along both the out-of-plane and in-plane directions through parallel-plate capacitor and coplanar interdigital capacitor along the
direction. A large anisotropy in these properties is observed. The in-plane remnant polarization (21.5 µC.cm
) is almost twice larger than that measured along the out-of-plane direction (13.5 µC.cm
), in agreement with the domain orientation. Oppositely, the in-plane pyroelectric coefficient (-285 µC.m
.K
) is much lower than that measured out-of-plane (-480 µC.m
.K
). The pyroelectric anisotropy is explicated in term of degree of structural freedom with temperature. In particular, the low in-plane pyroelectric coefficient is explained by a two-dimensional clamping of the layers on the substrate which induces tensile stress (from thermal expansion), competing with the decreasing tetragonality of a-domains (shortening of the polar c-axis lattice parameter). Temperature-dependent XRD measurements have revealed an increased fraction of a-domains with temperature, attesting the occurrence of a partial two-dimensional clamping. These observed properties are of critical importance for integrated pyroelectric devices.
This study compares the erbium emission from different Si-rich silicon oxynitrides matrices fabricated by magnetron sputtering. The Er-doped layers were grown by two different sputtering ...configurations: (i) standard co-sputtering of three confocal targets (Er2O3, Si3N4 and SiO2) under Ar plasma, and (ii) reactive co-sputtering under Ar+N2 plasma of either three (Er2O3, pure Si and SiO2) or two targets (Er2O3 and pure Si). The last reactive configuration was found to offer the best Er3+ PL intensity at 1.5μm. This highest PL intensity was found comparable to the corresponding emission from Er-doped silicon-rich silicon oxide.
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.
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