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

We demonstrate experimentally all-optical switching on a silicon chip at telecom wavelengths. The switching device comprises a compact ring resonator formed by horizontal silicon slot waveguides filled with highly nonlinear silicon nanocrystals in silica. When pumping at power levels about 100 mW using 10 ps pulses, more than 50% modulation depth is observed at the switch output. The switch performs about 1 order of magnitude faster than previous approaches on silicon and is fully fabricated using complementary metal oxide semiconductor technologies.

Photoluminescence lifetimes and optical absorption cross sections of Si nanocrystals embedded in SiO2 have been studied as a function of their average size and emission energy. The lifetimes span from 20 μs for the smallest sizes (2.5 nm) to more than 200 μs for the largest ones (7 nm). The passivation of nonradiative interface states by hydrogenation increases the lifetime for a given size. In contrast with porous Si, the cross section per nanocrystal shows a nonmonotonic behavior with emission energy. In fact, although the density of states above the gap increases for larger nanocrystals, this trend is compensated by a stronger reduction of the oscillator strength, providing an overall reduction of the absorption cross section per nanocrystal for increasing size.

Advanced data encryption requires the use of true random number generators (TRNGs) to produce unpredictable sequences of bits. TRNG circuits with high degree of randomness and low power consumption may be fabricated by using the random telegraph noise (RTN) current signals produced by polarized metal/insulator/metal (MIM) devices as entropy source. However, the RTN signals produced by MIM devices made of traditional insulators, i.e., transition metal oxides like HfO2 and Al2O3, are not stable enough due to the formation and lateral expansion of defect clusters, resulting in undesired current fluctuations and the disappearance of the RTN effect. Here, the fabrication of highly stable TRNG circuits with low power consumption, high degree of randomness (even for a long string of 224 − 1 bits), and high throughput of 1 Mbit s−1 by using MIM devices made of multilayer hexagonal boron nitride (h‐BN) is shown. Their application is also demonstrated to produce one‐time passwords, which is ideal for the internet‐of‐everything. The superior stability of the h‐BN‐based TRNG is related to the presence of few‐atoms‐wide defects embedded within the layered and crystalline structure of the h‐BN stack, which produces a confinement effect that avoids their lateral expansion and results in stable operation.

This paper investigates the interaction between Si nanoclusters ͑Si-nc͒ and Er in SiO 2 , reports on the optical characterization and modeling of this system, and attempts to clarify its effectiveness as a gain material for optical waveguide amplifiers at 1.54 m. Silicon-rich silicon oxide layers with an Er content of 4 -6 ϫ 10 20 at./ cm 3 were deposited by reactive magnetron sputtering. The films with Si excess of 6 -7 at. %, and postannealed at 900°C showed the best Er 3+ photoluminescence ͑PL͒ intensity and lifetime, and were used for the study. The annealing duration was varied up to 60 min to engineer the size and density of Si-nc and optimize Si-nc and Er coupling. PL investigations under resonant ͑488 nm͒ and nonresonant ͑476 nm͒ pumping show that an Er effective excitation cross section is similar to that of Si-nc ͑ϳ10 −17 -10 −16 cm 2 ͒ at low pumping flux ͑ϳ1016 -10 17 cm −2 s −1 ͒, while it drops at high flux ͑Ͼ10 18 cm −2 s −1 ͒. We found a maximum fraction of excited Er of about 2% of the total Er content. This is far from the 50% needed for optical transparency and achievement of population inversion and gain. Detrimental phenomena that cause depletion of Er inversion, such as cooperative up conversion, excited-stated absorption, and Auger deexcitations are modeled, and their impact in lowering the amount of excitable Er is found to be relatively small. Instead, Auger-type short-range energy transfer from Si-nc to Er is found, with a characteristic interaction length of 0.4 nm. Based on such results, numerical and analytical ͑Er as a quasi-two-level system͒ coupled rate equations have been developed to determine the optimum conditions for Er inversion. The modeling predicts that interaction is quenched for high photon flux and that only a small fraction of Er ͑0.2-2 %͒ is excitable through Si-nc. Hence, the low density of sensitizers ͑Si-nc͒ and the short range of the interaction are the explanation of the low fraction of Er coupled. Efficient ways to improve Er-doped Si-nc thin films for the realization of practical optical amplifiers are also discussed.