With digital equipment becoming increasingly networked, either on wired or wireless networks, for personal and professional use alike, distributed software systems have become a crucial element in information and communications technologies. The study of these systems forms the core of the ARLES' work, which is specifically concerned with defining new system software architectures, based on the use of emerging networking technologies. In this context, we concentrate on the study of distributed systems which bring to life the vision of ubiquitous computing systems, also known as ambient intelligence.

반도체 공정 overview

High-performance gas sensors prepared using p-type oxide semiconductors such as NiO, CuO, Cr2O3, Co3O4, and Mn3O4 were reviewed. The ionized adsorption of oxygen on p-type oxide semiconductors leads to the formation of hole-accumulation layers (HALs), and conduction occurs mainly along the near-surface HAL. Thus, the chemoresistive variations of undoped p-type oxide semiconductors are lower than those induced at the electron-depletion layers of n-type oxide semiconductors. However, highly sensitive and selective p-type oxide-semiconductor-based gas sensors can be designed either by controlling the carrier concentration through aliovalent doping or by promoting the sensing reaction of a specific gas through doping/loading the sensor material with oxide or noble metal catalysts. The junction between p- and n-type oxide semiconductors fabricated with different contact configurations can provide new strategies for designing gas sensors. p-Type oxide semiconductors with distinctive surface reactivity and oxygen adsorption are also advantageous for enhancing gas selectivity, decreasing the humidity dependence of sensor signals to negligible levels, and improving recovery speed. Accordingly, p-type oxide semiconductors are excellent materials not only for fabricating highly sensitive and selective gas sensors but also valuable additives that provide new functionality in gas sensors, which will enable the development of high-performance gas sensors.

Highly sensitive and selective gas sensors using p-type oxide semiconductors: Overview

A laminated structure comprises a first layer comprising a crystal with six-fold symmetry, and a second layer comprising a metal oxynitride crystal formed on the first layer, wherein the second layer comprises at least one element selected from the group consisting of In, Ga, Si, Ge and Al, N, O and Zn, as main elements, and wherein the second layer has in-plane orientation.

Substrate for growing wurtzite type crystal and method for manufacturing the same and semiconductor device

Harnessing solar energy for the production of clean hydrogen fuels by a photoelectrochemical (PEC) cell represents a very attractive but challenging alternative This review focuses on recent developments of some promising photoelectrode materials, such as BiVO4, a-Fe2O3, TaON, and Ta3N5 for solar hydrogen production Some strategies have been developed to improve PEC performances of the photoelectrode materials, including: (i) doping for enhancing visible light absorption in the wide bandgap semiconductor or promoting charge transport in the narrow bandgap semiconductor, respectively; (ii) surface treatment for removing segregation phase or surface states; (iii) electrocatalysts for decreasing the overpotentials; (iv) morphology control for enhancing the light absorption and shortening transfer distance of minority carriers; (v) other methods, such as sensitization, passivating layer, and band structure engineering using heterojunction structures, and so on Photochemical durability of the photoelectrodes is also discussed, since any potential PEC technology must balance efficiency against cost and photochemical durability Photochemical durability may be amended by optimizing the photoelectrode, electrocatalyst, and electrolyte at the same time In addition, solar seawater splitting is briefly introduced because it has received attention recently Finally, trends in research in PEC cells for solar hydrogen production are detailed

Photoelectrochemical cells for solar hydrogen production: current state of promising photoelectrodes, methods to improve their properties, and outlook

Wide-band-gap GaN and Ga-rich InGaN alloys, with energy gaps covering the blue and near-ultraviolet parts of the electromagnetic spectrum, are one group of the dominant materials for solid state lighting and lasing technologies and consequently, have been studied very well. Much less effort has been devoted to InN and In-rich InGaN alloys. A major breakthrough in 2002, stemming from much improved quality of InN films grown using molecular beam epitaxy, resulted in the bandgap of InN being revised from 1.9 eV to a much narrower value of 0.64 eV. This finding triggered a worldwide research thrust into the area of narrow-band-gap group-III nitrides. The low value of the InN bandgap provides a basis for a consistent description of the electronic structure of InGaN and InAlN alloys with all compositions. It extends the fundamental bandgap of the group III-nitride alloy system over a wider spectral region, ranging from the near infrared at ∼1.9 μm (0.64 eV for InN) to the ultraviolet at ∼0.36 μm (3.4 eV for GaN...

When group-III nitrides go infrared: New properties and perspectives

NiO crystallites based nanowires with different aspect ratios have been synthesized by a hydrothermal reaction of NiCl 2 with NaC 2 O 4 and H 2 O in the presence of ethylene glycol (EG) and subsequent annealing at 400 °C in air. Control over the aspect ratios of NiC 2 O 4 ·2H 2 O precursor nanowires in the range of 11–1050 was achieved by adjusting the hydrothermal reaction temperature and time. The formation of the NiC 2 O 4 ·2H 2 O nanowires results from the selective adsorption of EG molecules on ( 1 0 1 ¯ ) , ( 1 ¯ 0 1 ) , (0 1 0) and ( 0 1 ¯ 0 ) prismatic faces of NiC 2 O 4 ·2H 2 O with a monoclinic structure. The gas-sensing performance of the as-prepared NiO nanowires with different aspect ratios was investigated towards toluene, ethanol, acetone, triethylamine and methanol. It was found that the gas-sensing performance was improved with an increase on the aspect ratios of NiO nanowires.

Synthesis and enhanced gas-sensing properties of ultralong NiO nanowires assembled with NiO nanocrystals

Hollow sea urchin-like α-Fe 2 O 3 nanostructures were successfully synthesized by a hydrothermal approach using FeCl 3 and Na 2 SO 4 as raw materials, and subsequent annealing in air at 600 °C for 2 h. The hollow sea urchin-like α-Fe 2 O 3 nanostructures with the diameters of 2–4.5 μm consist of well-aligned α-Fe 2 O 3 nanorods with an average length of about 1 μm growing radially from the centers of the nanostructures, have a hollow interior with a diameter of about 2 μm. α-Fe 2 O 3 nanocubes with a diameter of 700–900 nm were directly obtained by a hydrothermal reaction of FeCl 3 at 140 °C for 12 h. The response S r ( S r  =  R a / R g ) of the hollow sea urchin-like α-Fe 2 O 3 nanostructures reached 2.4, 7.5, 5.9, 14.0 and 7.5 to 56 ppm ammonia, 32 ppm formaldehyde, 18 ppm triethylamine, 34 ppm acetone, and 42 ppm ethanol, respectively, which was excess twice that of the α-Fe 2 O 3 nanocubes and the nanoparticle aggregations. Our results demonstrated that the hollow sea urchin-like α-Fe 2 O 3 nanostructures were very promising for gas sensors for the detection of flammable and/or toxic gases with good-sensing characteristics.

Controlled synthesis and gas-sensing properties of hollow sea urchin-like α-Fe2O3 nanostructures and α-Fe2O3 nanocubes

In this paper, we present a comprehensive, correlative study of the structural, transport, optical and thermoelectric properties of high-quality VO2 thin films across its metal-insulator phase transition. Detailed x-ray diffraction study shows that it's textured polycrystalline along [010]M1, with in-plane lattice orienting along three equivalent crystallographic directions. Across the metal-insulator transition, the conductivity increases by more than 3 orders of magnitude with a value of 3.8 × 103 S/cm in the metallic phase. This increase is almost entirely accounted for by a change in electron density, while the electron mobility changes only slightly between the two phases, yet shows strong domain boundary scattering when the two phases coexist. Electron effective mass was determined to be ∼65m0 in the insulating phase. From the optical and infrared reflection spectra in the metallic phase, we obtained the plasma edge of VO2, from which the electron effective mass was determined to be ∼23m0. The bandg...

Comprehensive study of the metal-insulator transition in pulsed laser deposited epitaxial VO2 thin films

Uniform spherical flowerlike SnO2 architectures with the diameters of 1.7–2.0 μm were synthesized by a hydrothermal reaction of SnCl4 with NaOH and H2O in the presence of polyvinylpyrrolidone (PVP). These flowerlike architectures are assembled from submicron rods with the diameters of 300–600 nm. The constituent submicron rods are single crystalline SnO2 with the tetragonal structure, and grow along the direction perpendicular to (1 0 1) facet. The spherical flowerlike architectures constructed with SnO2 submicron rods are formed via the oriented attachment process. The response performance of the sensors based on the SnO2 spherical flowerlike architectures toward ethanol and triethylamine is better than that of SnO2 powders and can be further enhanced by improving their crystallinity. The sensor response is 3.65 and 2.97 when the concentration of ethanol and triethylamine is 105 and 45 ppm, respectively.

Synthesis and sensing properties of spherical flowerlike architectures assembled with SnO2 submicron rods

ZnO nanocrystals with various (0 0 2) orientations were synthesized via a solvothermal reaction of zinc acetate with n-butylamine (BA) and tetrahydrofuran at 140 °C for 12 h by varying the molar ratio of BA to Zn(II). The formation of the ZnO nanocrystals with various (0 0 2) orientations and shapes results from the selective adsorption of different amount of BA molecules on ZnO (0 0 1) surface. Photocatalytic activity of the as-prepared ZnO nanocrystals with various (0 0 2) orientations in degradation of methyl orange was studied, it was found that the exposed {0 0 1} facets are reactive facets. The structure and atomic charge distribution of the {0 0 1} facets were studied by periodic density functional theory calculations. Based on polar structure of the exposed {0 0 1} surfaces, a charge separation model between polar ZnO {0 0 1} surfaces was proposed. There is an internal electric field between positive Zn-ZnO (0 0 1) and negative O-ZnO ( 0 0 1 ¯ ) planes due to the spontaneous polarization. The internal electric field provides the driving force for charge separation. The reduction and oxidation reactions take place on the positive (0 0 1) and negative ( 0 0 1 ¯ ) polar planes, respectively. The charge separation model can deepen understanding of charge transfer in the semiconductor nanocrystal with highly photocatalytic activities and offer guidance to design more effective photocatalysts as well as new type solar cells, photoelectrodes or photoelectric devices.

Bin Liu

Papers

Synthesis and enhanced gas-sensing properties of ultralong NiO nanowires assembled with NiO nanocrystals

Controlled synthesis and gas-sensing properties of hollow sea urchin-like α-Fe2O3 nanostructures and α-Fe2O3 nanocubes

Comprehensive study of the metal-insulator transition in pulsed laser deposited epitaxial VO2 thin films

Synthesis and sensing properties of spherical flowerlike architectures assembled with SnO2 submicron rods

Charge separation between wurtzite ZnO polar {0 0 1} surfaces and their enhanced photocatalytic activity