Electrical characterization of deep levels existing in fully implanted and rapid thermal annealed p+n InP junctions

In this paper, the deep levels existing in fully implanted and rapid thermal annealed p⁺n junctions obtained by Mg/Si or Mg/P/Si implantations on nominally undoped n-type InP substrates were detected and characterized by the correlation of two electrical techniques: deep level transient spectroscopy (DLTS) and capacitance–voltage transient technique (CVTT). Two ion implantation-induced deep levels (at 0.25 and 0.27 eV below the conduction band) were detected by DLTS. Several characteristics of these traps were derived from CVTT measurements, paying special attention to their physical nature.     

Infrared characterization studies of poly-crystalline silicon annealed in a nitrogen atmosphere

A systematic study of the effect of annealing treatment in a nitrogen atmosphere on the oxygen and carbon impurities present in solar grade polysilicon has been conducted in the spectral region 4000–400 cm^–1 employing infrared spectroscopy. Thermal treatment was provided for 30 min at temperatures varying from 100–1300 °C. Results of the present study are in conformity with the reported annealing results on resistivity and photoconductivity.     

Electrical conductivity and optical properties of ZnO films annealed in hydrogen atmosphere after chemical vapor deposition

The d.c. electrical conductivity and optical properties of polycrystalline zinc oxide films (220–450 nm thick) annealed in hydrogen after chemical vapor deposition are investigated. A minimum film resistivity after the annealing gives 0.31 cm for the film as-deposited at a substrate temperature of 823 K. From the temperature dependence of conductivity, band conduction is confirmed for the films at temperatures above 250 K. The effect of grain-boundary scattering is due to thermionic emission of electrons over grain boundary barriers. At temperatures below 250 K, variable-range hopping transport is found to be dominant. The films are transparent in the wavelength range 400 to 1000 nm and have sharp ultraviolet absorption edges at 380 nm. The absorption edge analysis reveals the optical band gap energy for the films to be 3.18–3.23 eV. The Urbach tail analysis gives the width of localized states E_e=0.06-0.14eV.     

Electrical characterization of Si+ and Si+/P+ implanted N+P+In0.53Ga0.47As junctions

In this communication, we present I–V and admittance spectroscopy measurements of shallow n⁺p junctions into p-InGaAs made by Si⁺ implantation, including a complete study of the conduction mechanisms as a function of temperature. The effect of P⁺ co-implantation is also analysed. The I–V characteristics of both junctions show that recombination in the space-charge zone is the dominant transport mechanism in forward bias, with ideality factors around 1.5 at 300 K that increase with decreasing temperature of measurement. Activation energies of the reverse saturation current are obtained at room temperature, being 0.5 eV and 0.4 eV for Si⁺ and Si⁺P⁺ implanted diodes, respectively, indicating that recombination currents occur through a near midgap center. Reverse current–voltage measurements show a higher conduction in the P⁺ co-implanted junction due to a higher concentration of traps. In both types of junctions, the reverse characteristics can be fitted to a thermally-activated trap-assisted tunneling mechanism at low bias, involving traps at 0.41 eV and 0.44 eV for Si⁺ and P⁺ co-implanted junctions, respectively, whereas different trap-assisted tunneling processes dominate at medium and high bias. The small signal analysis show a clear difference between the two types of junctions. The use of Kramers–Kronig transforms on the admittance spectroscopy data reveals the presence of a defect level at 0.35 eV in both types of junctions, probably assigned to Zn, the native acceptor present in the p-InGaAs. Another trap level at 0.30 eV is detected at the P⁺ co-implanted junctions, not appearing in the Si doped junctions, which could probably be due to damage produced by the co-implantation.     

Surface characterization and biocompatibility of titanium alloys implanted with nitrogen by Hardion+ technology

In this study, the new Hardion+ micro-implanter technology was used to modify surface properties of biomedical pure titanium (CP-Ti) and Ti?C6Al?C4V ELI alloy by implantation of nitrogen ions. This process is based on the use of an electron cyclotron resonance ion source to produce a multienergetic ion beam from multicharged ions. After implantation, surface analysis methods revealed the formation of titanium nitride (TiN) on the substrate surfaces. An increase in superficial hardness and a significant reduction of friction coefficient were observed for both materials when compared to non-implanted samples. Better corrosion resistance and a significant decrease in ion release rates were observed for N-implanted biomaterials due to the formation of the protective TiN layer on their surfaces. In vitro tests performed on human fetal osteoblasts indicated that the cytocompatibility of N-implanted CP-Ti and Ti?C6Al?C4V alloy was enhanced in comparison to that of the corresponding non treated samples. Consequently, Hardion+ implantation technique can provide titanium alloys with better qualities in terms of corrosion resistance, cell proliferation, adhesion and viability.     

Electrical properties of films grown on W and Mo substrates by titanium ion implantation in nitrogen atmosphere

Films consisting of alternating nitride and oxide layers differing in phase composition and structure are grown on polycrystalline tungsten and molybdenum substrates by ion implantation. The resistivity and thermoelectric power of the films are measured as functions of temperature, and the temperature coefficient of their resistance is determined. The phase composition and electrical properties of the films are shown to be governed by the nitrogen-ion dose delivered to the titanium target.Translated from Neorganicheskie Materialy, Vol. 41, No. 3, 2005, pp. 301–304.Original Russian Text Copyright © 2005 by Ignatenko, Badekin.This revised version was published online in April 2005 with a corrected cover date.This revised version was published online in April 2005 with a corrected cover date.     

Spatial carrier distribution in InP/GaAs type II quantum dots and quantum posts

We performed a detailed investigation of the structural and optical properties of multi-layers of InP/GaAs quantum dots, which present a type II interface arrangement. Transmission electronic microscopy analysis has revealed relatively large dots that coalesce forming so-called quantum posts when the GaAs layer between the InP layers is thin. We observed that the structural properties and morphology affect the resulting radiative lifetime of the carriers in our systems. The carrier lifetimes are relatively long, as expected for type II systems, as compared to those observed for single layer InP/GaAs quantum dots. The interface intermixing effect has been pointed out as a limiting factor for obtaining an effective spatial separation of electrons and holes in the case of single layer InP/GaAs quantum-dot samples. In the present case this effect seems to be less critical due to the particular carrier wavefunction distribution along the structures.     

Microstructure and magnetic properties of FeCo/Ti thin film multilayers annealed in nitrogen

Multifunctional nanocomposites consisting of at least one ferromagnetic phase (e.g. FeCo) and one protective, wear resistant phase (e.g. TiN) are of interest for applications as sensors or actuators in harsh environments. This paper reports on the fabrication and characterization of nanocomposite thin films, prepared from FeCo/Ti metallic precursor multilayer composition spreads using a combinatorial sputter-deposition system. After deposition, the composition spread was annealed in nitrogen (5 × 10⁵ Pa pressure) at 850 °C for 1.5 h, leading to preferential nitriding of Ti to TiN, thus forming the protective phase. Automated energy dispersive X-ray analysis, Auger electron spectroscopy, X-ray diffraction measurements, transmission electron microscopy (TEM) and vibrating sample magnetometry were used for the characterization of the as deposited and nitrided composition spreads. As an unexpected result, the appearance of a Heusler phase (Co₂FeSi) in the nanocomposite was observed by TEM. After N₂ annealing, the nanocomposites show reduced saturation magnetization values μ₀M_S between 0.5 and 0.95 T and improved coercive field values μ₀H_c between 4 and 13.8 mT, dependent on the TiN content.     

低浓度氮氧化物的化学发光和检测

针对大气氮氧化合物浓度在线检测要求,研制出低浓度氮氧化合物化学发光检测系统。其中的样气与臭氧的混合用双层喷嘴结构完成,可以使一氧化氮分子与臭氧分子在新型化学反应室内全面迅速发生化学反应,从而提高化学发光效率;将光子计数头冷却至6oC,能使光子计数器的本底信号降低到12cps以下;使用改进的多组臭氧发光器和串行气路基本上消除了臭氧本底信号;采用多点离散光源会聚光路提高了光子探测能力。实验表明,该检测系统的检测灵敏度已达到5count/1ppb。     

Pores in p-type GaN by annealing under nitrogen atmosphere: formation and photodetector

Journal of Materials Science - Mg-doped p-GaN, which cannot be etched and porosified by wet etching, is annealed in a N2 environment to fabricate porous p-GaN for the first time. In the annealing...     

Ultrafast Zn2+ Intercalation and Deintercalation in Vanadium Dioxide

Although rechargeable aqueous zinc‐ion batteries have attracted extensive interest due to their environmental friendliness and low cost, they still lack suitable cathodes with high rate capabilities, which are hampered by the intense charge repulsion of bivalent Zn²⁺. Here, a novel intercalation pseudocapacitance behavior and ultrafast kinetics of Zn²⁺ into the unique tunnels of VO₂ (B) nanofibers in aqueous electrolyte are demonstrated via in situ X‐ray diffraction and various electrochemical measurements. Because VO₂ (B) nanofibers possess unique tunnel transport pathways with big sizes (0.82 and 0.5 nm² along the b‐ and c‐axes) and little structural change on Zn²⁺ intercalation, the limitation from solid‐state diffusion in the vanadium dioxide electrode is eliminated. Thus, VO₂ (B) nanofibers exhibit a high reversible capacity of 357 mAh g^?1, excellent rate capability (171 mAh g^?1 at 300 C), and high energy and power densities as applied for zinc‐ion storage.     

Nanocrystalline diamond films grown in nitrogen rich atmosphere: structural and field emission properties

The field emission behaviour of a series of nanocrystalline N-doped diamond films has been investigated and interpreted on the basis of the structural and compositional characteristics of the layers. The diamond films, formed by crystallites with grain size in the range 20-100 nm were produced from CH4/H2 mixtures using a HF-CVD apparatus. Nitrogen was added to the gaseous reactants in form of both N2 and of Urea. Micro-Raman spectroscopy and cathodoluminescence have been used to define the structure of the deposits on a nanometric scale. The field emission measurements have been carried out under a pressure of 10(-6) mbar using a sphere-to-plane anode-cathode configuration. The characteristics of the emission from the various nanodiamond samples and from different regions of the same sample are discussed in terms of field threshold, current density, current stability.     

Bulk and interface properties of (Zn,Mg)O buffer layers sputtered in hydrogen-containing atmosphere

Sputtered (Zn,Mg)O buffer layers are one of the few promising options for completely dry and cadmium-free manufacturing of chalcopyrite-based solar cells. The performance of a heterojunction solar cell depends critically on the electrostatic charge contained in the interface. In chalcopyrite-based cells this charge can be influenced by redox treatments. In this work we have added hydrogen to the working gas when sputtering the buffer layer in an effort to optimize the interface charge. We report on the unexpectedly complex effects even at low hydrogen flow. They include a reduced deposition rate, significantly altered diffractograms and higher Mg/Zn-ratio in the film. X-ray photoelectron spectroscopy reveals the deposition of a thin layer of metallic zinc in the initial deposition stage which is not observed in the absence of hydrogen. Small hydrogen concentrations appear to be beneficial in terms of cell performance and reproducibility. However, higher concentrations typically cause a loss in blue response which indicates the formation of a homojunction buried within the chalcopyrite absorber.     

Thermal degradation behavior and kinetic analysis of poly(L-lactide) in nitrogen and air atmosphere

The non-isothermal and isothermal degradation behaviors and kinetics of poly(L-lactide) (PLLA) were studied by using thermogravimetry analysis (TGA) in nitrogen and air atmosphere, respectively. At lower heating rate ((5–10)°C/min), PLLA starts to decompose in air at lower temperature than those in nitrogen atmosphere; however, at higher heating rate ((20–40)°C/min), the starting decomposition temperature in air are similar to those in nitrogen atmosphere, not only showing that PLLA has better thermal stability in nitrogen than in air atmosphere, but also suggesting that the faster heating rate will decrease the decomposition of PLLA in thermal processing. Whether in air or in nitrogen atmosphere, the decomposition of PLLA has only one-stage degradation with a first-order decomposed reaction, suggesting that the molecular chains of PLLA have the similar decomposed kinetics. The average apparent activation energy of non-isothermal thermal degradation (Ē_non) calculated by Ozawa theory are 231.7kJ·mol⁻¹ in air and 181.6kJ·mol⁻¹ in nitrogen; while the average apparent activation energy of isothermal degradation (Ē_iso) calculated by Flynn method are 144.0kJ·mol⁻¹ in air and 129.2kJ·mol⁻¹ in nitrogen, also suggesting that PLLA is easier to decompose in air than in nitrogen. Moreover, the decomposed products of PLLA are also investigated by using thermogravimetry-differential scanning calorimetry-mass spectrometry (TG-DSC-MS). In air atmosphere the volatilization products are more complex than those in nitrogen because the oxidation reaction occurring produces some oxides groups.     

Thermal degradation behavior and kinetic analysis of poly(L-lactide) in nitrogen and air atmosphere

The non-isothermal and isothermal degradation behaviors and kinetics of poly(L-lactide) (PLLA) were studied by using thermogravimetry analysis (TGA) in nitrogen and air atmosphere, respectively. At lower heating rate ((5–10)°C/min), PLLA starts to decompose in air at lower temperature than those in nitrogen atmosphere; however, at higher heating rate ((20–40)°C/min), the starting decomposition temperature in air are similar to those in nitrogen atmosphere, not only showing that PLLA has better thermal stability in nitrogen than in air atmosphere, but also suggesting that the faster heating rate will decrease the decomposition of PLLA in thermal processing. Whether in air or in nitrogen atmosphere, the decomposition of PLLA has only one-stage degradation with a first-order decomposed reaction, suggesting that the molecular chains of PLLA have the similar decomposed kinetics. The average apparent activation energy of nonisothermal thermal degradation (Ē _non) calculated by Ozawa theory are 231.7 kJ·mol⁻¹ in air and 181.6 kJ·mol⁻¹ in nitrogen; while the average apparent activation energy of isothermal degradation (Ē _iso) calculated by Flynn method are 144.0 kJ·mol⁻¹ in air and 129.2 kJ·mol⁻¹ in nitrogen, also suggesting that PLLA is easier to decompose in air than in nitrogen. Moreover, the decomposed products of PLLA are also investigated by using thermogravimetry-differential scanning calorimetry-mass spectrometry (TGDSC-MS). In air atmosphere the volatilization products are more complex than those in nitrogen because the oxidation reaction occurring produces some oxides groups.     

改性沸石对电镀废水中Pb2+、Zn2+、Ni2+的吸附

将天然沸石进行处理制备出多孔质改性沸石颗粒。在静态条件下，研究了改性沸石颗粒对重金属离子Pb^2 ,Zn^2 ,Ni^2 的吸附效果及条件，含Pb^2 ,Zn^2 ,Ni^2 的电镀废水经改性沸石颗粒吸附后，废水中Pb^2 ,Zn^2 ,Ni^2 的含量低于国家排放标准。