Single crystalline octahedral Zn doped Fe 3 O 4 was successfully prepared through a simple hydrothermal method without the assistance of any surfactant or template. Porosity and crystalline properties characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). Results showed as-synthesized Zn doped Fe 3 O 4 are uniform octahedrons with high crystalline. In addition, the possible mechanism for the formation of octahedral products via the time-dependent experiments and the role of hydrazine hydrate in the synthesis process was also discussed. Their photo-Fenton activity in photodegradation of Rhodamine B under visible light was sequentially investigated, indicating the high photocatalytic capacity of as-obtained octahedrons.
Recently, the incorporation of transition metals into magnetite increasing the heterogeneous Fenton catalytic activity of magnetite with high efficiency and interesting magnetic properties applied for degradation of organic pollutants in water purification and wastewater treatment have attracted more and more researchers. In this review, using of one or some metal doped magnetite based systems in heterogeneous Fenton, or photo-Fenton processes are discussed. Then, the role of metal doped species for the enhanced efficiency of degradation process is presented. Finally, possible reaction mechanism for the photo-Fenton degradation pollutants in the present of metal doped magnetite is also given.
We report on the identification of a deep level trap centre which contributes to generation-recombination noise. A n-GaN epilayer, grown by MOCVD on sapphire, was measured by deep level transient spectroscopy (DLTS) and noise spectroscopy. DLTS found 3 well documented deep levels at Ec − 0.26 eV, Ec − 0.59 eV, and Ec − 0.71 eV. The noise spectroscopy identified a generation recombination centre at Ec − 0.65 ± 0.1 eV with a recombination lifetime of 65 μs at 300 K. This level is considered to be the same as the one at Ec − 0.59 eV measured from DLTS, as they have similar trap densities and capture cross section. This result shows that some deep levels contribute to noise generation in GaN materials.
The fabrication of a p-shell/n-core coaxial nanorod ZnO homojunction light-emitting diode by inexpensive solution method is demonstrated. The p-type conductivity of the ZnO shell arises from the incorporation of potassium while the n-type conductivity of the core is due to unintentional doping.
An approach for heterogeneous integration of InGaAs MOSHEMTs and Si-CMOS is proposed and a high quality multi-layer transfer process is demonstrated in 200 mm wafer scale. Heterostructures for In0.30Ga0.70As MOSHEMTs were grown using MOCVD on 200 mm Si substrates with record low threading dislocation density of < 2 × 10 7 cm −2 . Devices with a Si-CMOS compatible front-end process were fabricated and the impact of the heterostructure design and doping on device performance is studied. Low subthreshold swing with minimum (Smin) down to 70 mV/decade was achieved by employing an InGaP top barrier layer and a cap doping of ∼2 × 10 19 cm −3 was obtained with a Si-Te co-doping technique. An effective mobility (μ eff ) of ∼4900 cm 2 /Vs at sheet electron density (N) of 3 × 10 12 cm −2 was achieved which is record among InxGa 1 -xAs (x < 0.53) MOSFETs on Si substrates. In addition, current-gain cut-off frequency f T ) of ∼60 GHz was extracted for 150 nm channel length MOSHEMTs.
The incorporation of new materials into CMOS scaling has become a necessity. Our previous work in SiGe and III-V integration shows promise in allowing further materials integration for increased transistor density. However, a principal concern is that investment returns by further increasing transistor density will likely be negative for all but possibly one or two corporations, and may be negative for all. Moore’s Law metrics for the benefits of incorporating III-V and other materials monolithically into silicon CMOS are not sufficient to determine innovative value for CMOS+X combinations. Such an environment that cannot use traditional metrics is a challenge for all organizations participating in the previous paradigm. Despite these challenging times, we list the likely characteristics of a new innovation path, and describe our efforts to follow it through research into ‘white space’ integrated circuits employing new materials and devices. Initially, we are designing novel integrated circuits, materials and processes incorporating GaN HEMTs, GaN and AlInGaP LEDs, and InGaAs HEMTs monolithically into existing silicon CMOS foundry processes. Both heteroepitaxy and wafer bonding are used in the process flow, and SiGe or Ge buffer layers are used in many processes. A modular process flow is incorporated so that the new devices can be modeled and incorporated into the design kit for a foundry process, allowing us to leverage much of the existing silicon design and manufacturing infrastructure. Our initial focus is on the demonstration of wafer-level integration of III-V devices with foundry 0.18 -micron CMOS devices on 200 mm wafers, and we report on the progress made in materials, device and circuit design towards this goal.
We report on the growth of In 0.30 Ga 0.70 As channel high electron mobility transistor (HEMT) epi-layers on a 200-mm Si substrate by metal-organic-chemical-vapor-deposition. The HEMT layers were grown on the Si substrate by using a ~3- ${\mu }\text{m}$ thick epitaxial buffer composing of a Ge layer, a GaAs layer, and a compositionally graded and strain relaxed InAlAs layer. The optimized epitaxy has a threading dislocation density of less than $2 {\times } 10^{{7}}$ cm −2 and a root mean square surface roughness of ~6.7 nm. The device active layers include a ${ {\delta } }$ -doped InAlAs bottom barrier, a ~15-nm thick InGaAs channel, a ~8-nm InGaP top barrier layer and a heavily doped InGaAs contact layer. MOSHEMTs with channel length down to 130 nm were fabricated. The devices achieve a peak transconductance of ${\sim }450 ~{\mu }\text{S}/ {\mu }\text{m}$ at ${V} _{ D}$ of 0.5 V. The peak effective mobility ( ${\mu }_{\text {eff}}$ ) in a device with a channel length of 20 $ {\mu }\text{m}$ device channel was ~3700 cm 2 / $\text{V} {\cdot }\text{s}$ .
The imaging and surveying ground areas with airborne sensors has important application for disaster monitoring, military application and rescue operation. The proposed solution seeks to explore a new approach in microwave shielding design through coating of high permittivity, hydrophilic oxide materials. To achieve this, multi-stacked metal oxides, Titanium Dioxide (TiO2), Barium Titanium Trioxide (BaTiO3) and Iron Ferrite (Fe) are deposited on the Sapphire ring and optical dome via Unbalanced Magnetron (UBM) sputtering. The complex permittivity (Ɛ' and Ɛ") and permeability (μ' and μ") of oxide-coated substrates are verified through measurement of their Scattering (S-) parameters (S11 and S21) via Vector Network Analyzer (VNA) between 300MHz to 18GHz regime by airline measurement technique for oxide sputtered on sapphire ring substrate. The optimal layers were sputtered on acrylic substrate as well as acrylic domes with arch reflectance result obtained using Pasco Kit measurement kit at 10.5GHz.
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