Known as Bellcore after its establishment in the United States in 1983 as part of the break-up of the Bell System, the company's name changed to Telcordia Technologies after a change of ownership in 1996. The business was acquired by Ericsson in 2012, then restructured and rebranded as iconectiv in 2013.A major architect of the United States telecommunications system, the company pioneered many services, including caller ID, call waiting, mobile number portability and toll-free telephone number (800) service. It also pioneered the prepaid charging system and the Intelligent Network.Headquartered in Bridgewater, New Jersey (U.S.), iconectiv provides network and operations management, numbering, registry and fraud prevention services for the global telecommunications industry. It provides numbering services in more than a dozen countries, including serving as the Local Number Portability Administrator (LNPA) for the United States. In that capacity, iconectiv manages the Number Portability Administration Center (NPAC), the system that supports the implementation of local number portability.S.S.
Ferroelectric PbZr0.2Ti0.8O3/YBa2Cu3O7 heterostructures have been grown on single crystal LaAlO3 and on buffered [100] Si. The cuprate superconductors are used as metal-like bottom electrodes for the subsequent growth of the ferroelectric PZT thin film. Structural studies using x-ray diffraction, and transmission electron microscopy show that the PZT layer is free of large angle grain boundaries (i.e., single crystal-like). Rutherford backscattering studies reveal the composition of the PZT layer to be close to that of the target. Ferroelectric hysteresis measurements using both pulsed measurements and a variable frequency Sawyer-Tower circuit yield remnant polarization values (at 5V) in the range of 15–45μC/cm2 (depending on deposition conditions) with a coercive field in the range of 80–120kV/cm. At a cycling voltage of 5V, these heterostructures exhibit a fatigue lifetime of better than 2x1010 at 40kHz (the polarization decays by only 20% of the initial value). Pulsed poling experiments before and after show that the loss of polarization is reversible. These heterostructures also show excellent aging and logic state retention characteristics.
Heterostructures consisting of III-V semiconductors and epitaxial layers of the rare earth monoarsenides can be grown by molecular beam epitaxy. By alloying ErAs with ScAs, lattice match can be achieved with (Al, Ga)As. Using magneto-transport measurements, we show that these layers are semi-metallic with equal electron and hole concentrations, 3.0 x1020 cm−3. Shubnikov-de Haas oscillations are used to confirm the predicted Fermi surface geometry and measure the electron effective mass and the coupling to the 4f spin on the Er3+ ion. Remarkably, the material shows no transition from semimetal to semiconductor as the film thickness is reduced to three monolayers. Below three monolayers the films are not uniform and are believed to consist of islands three monolayers high. This system provides a unique opportunity to explore novel electronics based on controlled transport through semimetal/semiconductor heterostructures. Lateral transport through semimetal islands immersed in a δ-doped layer may provide a fast non-linear material for THz electronics. Vertical transport through thin epitaxial layers may enable resonant tunneling hot electron transistors with a semi-metal base. Preliminary experiments on transistor like test structures measure some transfer through a 10 monolayer thick semimetal base. They also identify overgrowth of the III-V semiconductor on the semimetal layer as the key materials issue.
The plasma-enhanced metalorganic chemical vapor deposition (PE-MOCVD) process has been successfully used to achieve high quality epitaxial growth of BaTiO3 thin films on (001) LaA103 and (001) NdGaO3 substrates at a substrate temperature of 680°C. The PEMOCVD system, which incorporates a 300-Watt microwave cavity, introduces excited species from an oxygen plasma to lower the required deposition temperature, as compared to thermal MOCVD growth of BaTiO3. X-ray diffraction (XRD) θ-20 scan patterns indicate that there are few randomly oriented grains and impurity phases in the epitaxial BaTiO3 films. Results of XRD ϕ-scans of the BaTiO3 (202) reflection show a modulation pattern of peaks every 90°, which demonstrates that the BaTiO3 thin films have no misorientation along the [100] and [010] directions of the substrates. An XRD ω rocking curve of the BaTiO3 (200) reflection had a narrow FWHM of 0.25°, indicating that the films have a high degree of preferred orientation of <100> perpendicular to the substrates. The high degree of epitaxial crystallinity is further confirmed by Rutherford Backscattering Spectrometry which gives a minimum yield of 7.5% and 11% for the films deposited on LaAIO3 and NdGaO3, respectively. Scanning electron micrographs show that these films have very smooth surface morphologies, which are desirable for device applications.
Epitaxial PrBa2Cu3O7 superconductor/ferroelectric bismuth titanate heterostructures grown on [001] oriented LaAlO3 by pulsed laser deposition are being studied. X-ray diffraction studies of the heterostructures have shown that all the layers grow in the c-axis orientation. In this investigation, the early stages of ferroelectric film growth have been studied using transmission electron microscopy (TEM) of crosssectioned samples. High resolution lattice imaging has been carried out to study the atomic structure of the ferroelectric/superconductor growth interface and the defect structure of the ferroelectric film.
The 16 articles in this special section examine both licensed and unlicensed spectrum for 5G/B5G wireless networks. The incredible increase in connected appliances and downloaded applications has pushed mobile operators to the limits of their licensed spectrum bands. This has triggered the idea of evolving the current radio access network to use the underutilized unlicensed spectrum to extend spectrum resources beyond current usage charts. This mode of cellular access has raised a lot of questions about use cases, enabling technologies, and fairness to other native unlicensed users, such as WiFi. Nevertheless, unlicensed access is being accepted as one of the most significant solutions to improve the resource availability and system scalability in future fifth generation (5G)/beyond 5G (B5G) networks.
