Structural origins of electronic conduction in amorphous copper-doped alumina

We perform an {\it ab initio} modeling of amorphous copper-doped alumina (a-Al$_2$O$_3$:Cu), a prospective memory material based on resistance switching, and study the structural origin of electronic conduction in this material. We generate molecular dynamics based models of a-Al$_2$O$_3$:Cu at various Cu-concentrations and study the structural, electronic and vibrational properties as a function of Cu-concentration. Cu atoms show a strong tendency to cluster in the alumina host, and metallize the system by filling the band gap uniformly for higher Cu-concentrations. We also study thermal fluctuations of the HOMO-LUMO energy splitting and observe the time evolution of the size of the band gap, which can be expected to have an important impact on the conductivity. We perform a numerical computation of conduction pathways, and show its explicit dependence on Cu connectivity in the host. We present an analysis of ion dynamics and structural aspects of localization of classical normal modes in our models

Field trial of a 15 Tb/s adaptive and gridless OXC supporting elastic 1000-fold all-optical bandwidth granularity

An adaptive gridless OXC is implemented using a 3D-MEMS optical backplane plus optical modules (sub-systems) that provide elastic spectrum and time switching functionality. The OXC adapts its architecture on demand to fulfill the switching requirements of incoming traffic. The system is implemented in a seven-node network linked by installed fiber and is shown to provide suitable architectures on demand for three scenarios with increasing traffic and switching complexity. In the most complex scenario, signals of mixed bit-rates and modulation formats are successfully switched with flexible per-channel allocation of spectrum, time and space, achieving over 1000-fold bandwidth granularity and 1.5 Tb/s throughput with good end-to-end performance

Bulk and Surface Nucleation Processes in Ag2S Conductance Switches

We studied metallic Ag formation inside and on the surface of Ag2S thin films, induced by the electric field created with a STM tip. Two clear regimes were observed: cluster formation on the surface at low bias voltages, and full conductance switching at higher bias voltages (V > 70mV). The bias voltage at which this transition is observed is in agreement with the known threshold voltage for conductance switching at room temperature. We propose a model for the cluster formation at low bias voltage. Scaling of the measured data with the proposed model indicates that the process takes place near steady state, but depends on the STM tip geometry. The growth of the clusters is confirmed by tip retraction measurements and topography scans. This study provides improved understanding of the physical mechanisms that drive conductance switching in solid electrolyte memristive devices.Comment: In press for PR

Experimental demonstration of gridless spectrum and time optical switching

An experimental demonstration of gridless spectrum and time switching is presented. We propose and demonstrate a bit-rate and modulation-format independent optical cross-connect architecture, based on gridless spectrum selective switch, 20-ms 3D-MEMS and 10-ns PLZT optical switches, that supports arbitrary spectrum allocation and transparent time multiplexing. The architecture is implemented in a four-node field-fiber-linked testbed to transport continuous RZ and NRZ data channels at 12.5, 42.7 and 170.8 Gb/s, and selectively groom sub-wavelength RZ channels at 42.7 Gb/s. We also showed that the architecture is dynamic and can be reconfigured to meet the routing requirements of the network traffic. Results show error-free operation with an end-to-end power penalty between 0.8 dB and 5 dB for all continuous and sub-wavelength channels

Influence of Cu Diffusion Conditions on the Switching of Cu-SiO\u3csub\u3e2\u3c/sub\u3e-Based Resistive Memory Devices

This paper presents a study of Cu diffusion at various temperatures in thin SiO2 films. Film composition and diffusion products were analyzed using Secondary Ion Mass Spectroscopy, Rutherford Backscattering Spectrometry, X-ray Diffraction and Raman Spectroscopy methods. We found a strong dependence of the diffused Cu concentration, which varied between 0.8 at.% and 10-3 at.%, on the annealing temperature. X-ray diffraction and Raman studies revealed that Cu does not react with the SiO2 network and remains in elemental form after diffusion. Programmable Metallization Cell (PMC) resistive memory cells were fabricated with these Cu-diffused SiO2 films as the active elements and device performance is presented and discussed in the context of the materials characteristics

Two-dimensional electrical characterization of ultrashallow source/drain extensions for nanoscale MOSFETs

Abstract State-of-the-art semiconductor devices require accurate control of the full two-dimensional dopant distribution. In this work, we report results obtained on 2D electrical characterization of ultra shallow junctions in Si using off axis electron holography to study two-dimensional effects on diffusion. In particular, the effect of a nitride diffusion mask on lateral diffusion of phosphorous is discussed. Retardation of lateral diffusion of P under the nitride diffusion mask is observed and compared to the lateral diffusion of P under an oxide diffusion mask. The ultra shallow junctions for the study were fabricated by a rapid thermal diffusion process from heavily P doped spin-on-dopants into a heavily B doped Si substrate. These shallow junctions are needed for fabricating source/drain extensions in nanoscale MOSFETs. One-dimensional electrical characterization of the junction was carried out to determine the electrical junction depth and compared to the metallurgical junction depth from SIMS analysis

High speed chalcogenide glass electrochemical metallization cells with various active metals

We fabricated electrochemical metallization (ECM) cells using a GaLaSO solid electrolyte, a InSnO inactive electrode and active electrodes consisting of various metals (Cu, Ag, Fe, Cu, Mo, Al). Devices with Ag and Cu active metals showed consistent and repeatable resistive switching behaviour, and had a retention of 3 and >43 days, respectively; both had switching speeds of < 5 ns. Devices with Cr and Fe active metals displayed incomplete or intermittent resistive switching, and devices with Mo and Al active electrodes displayed no resistive switching ability. Deeper penetration of the active metal into the GaLaSO layer resulted in greater resistive switching ability of the cell. The off-state resistivity was greater for more reactive active metals which may be due to a thicker intermediate layer

Origin of giant photocontraction in obliquely deposited amorphous Ge_xSe_{1-x} thin- films and the intermediate phase

Obliquely deposited amorphous Ge_xSe{1-x} thin-films at several compositions in the 0.15 < x < 0.333 range, and at several obliqueness angles in the 0 < alpha < 80 range at each x were evaporated on Si and glass substrates. Here alpha designates the angle between film normal and direction of vapor transport. Raman scattering, ir reflectance and optical absorption measurements were undertaken to characterize the vibrational density of states and optical band gaps. Edge views of films in SEM confirm the columnar structure of obliquely (alpha = 80) deposited films. Films, mounted in a cold stage flushed with N2 gas, were irradiated to UV radiation from a Hg-Xe arc lamp, an

COMPARAÇÃO DE DIFERENTES PROTOCOLOS PARA A SINCRONIZAÇÃO DE ESTRO E INSEMINAÇÃO ARTIFICIAL EM TEMPO FIXO EM VACAS DA RAÇA NELORE EM ANESTRO PÓS-PARTO

In this study different methods of estrus synchronization in 139 Nellore cows in November 2006 in Arapoty-PR, was compared.  Four protocols for estrus synchronization was applied. In the first group (G1), was used dispositive vaginal device, impregnated with 360 mg of medroxiprogesterone acetate (MAP) and 2mg of estradiol benzoate (BE). After remotion (day 8), 150 µg of cloprostenol was in the vulva submucosa administered (for all the groups) and 1 mg of estradiol cipionate. In group two (G2) were used as vaginal device impregnated with 360 mg of MAP. After remotion (8th day), 0,75 µg of cloprostenol was injected. In group three (G3), a dispositive intravaginal device re-impregned with 360 mg of MAP was used  and 2mg of BE. After remotion (day 8), the cows received 150 µg of cloprostenol and 1 mg of ecp. In group four (G4), a dispositive intravaginal device re-impregned with 360 mg of MAP was used and after remotion, 0,75 µg of cloprostenol was injected.  For groups G1, G2, G3 the artificial insemination (AI) was performed in a fixed time of 56 hours after the removal of the progestagens. In the group 4, the AI was performed 12 hours after the observation of the estrus. The diagnosis of pregnancy was performed via rectal palpation after two months from the AI. It was concluded that the different protocols used in this research to synchronization of estrus do not influence the rate of pregnancy.Neste estudo comparou-se diferentes métodos de sincronização de estro em 139 vacas da raça Nelore, em novembro de 2006 no município de Arapoti-PR. Foram utilizados quatro protocolos de sincronização de estro. No primeiro grupo (G1), foi utilizado pessário vaginal de poliuretano, impregnada com 360 mg de acetato de medroxiprogesterona (MAP) e 2 mg de Benzoato de Estradiol (BE) (=dia 0). Após a remoção (=dia 8), foi administrado 150 µg de cloprostenol, na submucosa vulvar (para todos os grupos) e 1 mg de cipionato de estradiol (ecp). No grupo dois (G2) foram utilizados pessários vaginais idênticos aos usados no G1. Na remoção (dia 8) foi administrado 0,75 µg de cloprostenol e 1 mg de cipionato de estradiol. No grupo três (G3), foi utilizado dispositivo intravaginal (sob a forma de Y) reaproveitado e impregnado com 360 mg de MAP e 2 mg de BE. Após 8 dias era removido e administrava-se 150 µg  de cloprostenol e 1 mg de cipionato de estradiol. No grupo quatro (G4), foi utilizado identico dispositivo intravaginal ao usado no G3 e após removido(dia 8), aplicava-se 0,75 µg de cloprostenol sem o ecp. Para os grupos G1, G2, G3 a inseminação artificial (IA) foi realizada em tempo fixo às 56 horas após a retirada do pessário vaginal, sem a observação de estro. No G4 a IA era realizada 12 horas após a observação visual de estro. O diagnóstico de gestação foi efetuado por palpação retal após 60 dias. Concluiu-se que os diferentes protocolos de sincronização de estro utilizados não influenciaram a taxa de prenhez