Behaviour of Charge Carriers in As-Deposited and Annealed Undoped TCO Films

We examine the structures,cut-off points of transmittance spectra and electric properties of undoped ZnO,SnO_(2) and CdO films by scanning electron microscopy,x-ray diffraction,spectrophotometer and Hall-effect measurements,respectively.The films are deposited by using an rf magnetron sputtering system from powder targets in argon and then annealed in vacuum.The structures and properties of the as-deposited films are compared with those of the annealed one.We try to explain the behaviour of charge carriers based on the semiconductor physics theory.

Room Temperature Visible Photoluminescence from Thermally Annealed Hydrogenated Amorphous Silicon Films

A visible photoluminescence from a thermally annealed boron doped hydrogenated amorphous silicon(a-Si:H)film has been observed at room temperature.The wavelength at the peak of the photoluminescent spectra is about 600nm.The intensity of photoluminescence is dependent on the annealing temperature strongly and relative to the deposition technology parameters of the films,especially to the hydrogen dilution of the boron doped silane and the deposition rate of the films.There exists a quantum size effect of nanometer-scale porosity on the surface of the annealed a-Si:H film.The quantum-confined structures may form due to the evolution of hydrogen from the surface of the films during the annealing procedure.The density of the porosity is relative to the quantity of evolved hydrogen from the film and the evolution rate of the hydrogen.

Transmission Spectral Characteristics of Photonic Crystals Milled in Annealed Proton-Exchange LiNbO_3 Waveguide

Transmission spectra of triangular lattice photonic crystals milled in the top surface of an annealed protonexchange waveguide are numerically simulated.The effects of the finite depth,conical shape,trapezoidal shape and hybrid shape of holes are theoretically analyzed.Due to the difficulty of milling high aspect-ratio cylindrical holes in lithium niobate(LiNbO_3),a compromised solution is proposed to improve the overlap between shallow holes and the waveguide mode,and useful transmission spectra with strong contrast and sharp band edges are achieved.

STUDY OF HYDROGEN IN ANNEALED AMORPHOUS SILICON AND IMPLANTED AMORPHOUS CARBON

Hydrogen contents and its depth profiles, obtained by nuclear reaction induced by fluorine ion, have been investigated for a series of thermal annealed amorphous silicon and implanted amorphous carbon (diamond-like carbon) films. For dual layer amorphous silicon films, it is shown that hydrogen of either a-Si:H or a-SiNx:H sublayer moves obviously at different annealing conditions. For diamond-like carbon (DLC) films, measurements show that, by argon implantation, hydrogen contents decrease obviously with the increase of implanting dose. The decrease of hydrogen contents results in the decrease of diamond- like (SP3) and graphite-like (SP2) components of DLC films. But, the ratios of SP2 and SP3 increased, and the resistivities decrease with the increase of implanting dose.

Ordering of the α-Fe(Si) Crystallization Phase in Annealed Fe_(73.5)Cu_1Mo_3Si_(13.5)B_9 Alloy

The ordering of the α-Fe(Si) crystallization phase in annealed Fe73.5Cu1Mo3Si13.5B9 alloy has been studied using XRD method. The α-Fe(Si) phase in Fe73.5Cu1Mo3Si13.5B9 alloy annealed at 460℃ for 1 h consists of the DO3-type ordered region with spherical shape and disordered region. The size of DO3 ordered region increases with the annealing temperature. When the annealing temperature is 560℃, the size of the ordered region in the α-Fe(Si) grain is 14.0nm,which is nearly as large as that of the α-Fe(Si) grain (14.2 nm) and the degree of order of the α-Fe(Si) phase is about 0.78. When Fe73.5Cu1 Mo3Si13.5B9 amorphous alloy is annealed at 520℃， with the increment of the annealing time, the shape of the DO3 ordered region in the α-Fe(Si) phase is spheroidal at the beginning of the annealing and becomes spherical and has asize of 12.8 nm when the annealing time is 60 min. In addition, the DO3 superlattice lines of the α-Fe(Si) phase will vanish if Fe73.5Cu1Mo3Si13.5 B9 amorphous alloy is annealed for 1 h at 750℃.

Microstructure of Differently Annealed NanocrystallineFe_(72.7)Cu_1Nb_(1.8)Mo_2Si_(13)B_(9.5) Alloy

The microstructure of differently annealed nanocrystalline Fe72.7Cu1Nb1.8Mo2Si13B9.5 alloy was investigated by using Mssbauer spectroscopy and transmission electron microscope. The specimens were isochronally annealed at temperatures between 480℃ and 600℃ for 0.5 h. The experimental results show that the microstructure mainly consists of the nanoscale bcc α-Fe(Si) grains and the residual amorphous matrix phase. A trace paramagnetic phase was found for annealing about above 500℃. The volume fraction of cr-Fe(Si) grain increases with increasing annealing temperature, whereas the average size of grain is almost unchanged above 480℃ up to 580℃. The calculated thickness of the intergranular layer of the residual amorphous matrix clearly decreases with increasing annealing temperature.

High Resolution Electron Microscopy Observations of Structural Changes in Iron Nitride Films Annealed in Vacuum

Iron-nitride films were prepared by reactive sputtering, and the effect of annealing treatment on the structures was investigated by means of in-situ electron microscopy and high resolution electron microscopy (HREM). As-deposited films were observed to be a mixed structure of a few ultrafine ε-Fe2-3N particles existing in the amorphous matrix. lt was found that the structurerelaxation in the amorphous occurred at 473 K, and the ultrafine grains began to grow at the higher annealing temperatures. The transition of the amorphous to ε-Fe2-3N was almost completed at 673 K. It is considered that the formation of the ideal ε-Fe3N is originated from the ordering of the nitrogen atoms during the annealing in vacuum. On the other hand, γ’-phase (Fe4N) was seen to precipitation of ε-phase at 723 K. Two possible modes are proposed in the precipitation of γ’-phase, depending on the heating rate and crystallographic orientation relationships. i.e. [121]ε [001]γ, (210)ε(110)γ and [100]ε[110]γ, (001)ε(111)γ. In addition,α-Fe particles were observed to form from the γ’-phase at high temperatures. We assumed that these structural changes are due to the diffusion of nitrogen and iron atoms during the annealing,except for the case of the precipitation of the γ’-phase as depicted above. The results obtained in this work are in a good agreement with the assumption.

Giant Magneto-Impedance Effect in Amorphous and Current Annealed Fe73.5Cu1Nb3Si13.5B9 Wire

The magneto-impedance (MI) effect in amorphous and current annealed Fe73.5Cu1Nb3Si13.5B9 wires has been measured to investigate the influence of DC annealing, high-current-density electropulsing annealing and tensile stress applied during annealing process. The results showed that the MI of DC annealed sample exhibits a sharp maximum. The Maximum MI ratio of 60 % was observed in the sample of high-current-density electropulsing annealed under applied tensile stress.

FERROELECTRIC CHARACTERISTICS OF SrBi_2Ta_2O_9 THIN FILMS ANNEALED IN FORMING GAS

The degradation behavior of SrBi2 Ta2O9 (SBT) thin films annealed in forming gas (5%H2 +95%N2) was investigated. The ferroelectric remnant polarization P. of SBT had a severe decrease in the containing H2 atmosphere at 400℃. SEM results showed that Bi could be reduced from SBT thin films for the effect of H2. The reduction role increased with a rise of annealing temperature. SBT thin films lost their ferroelectricity when the annealing temperature was above 450℃. It implied that the degradation of P. value or the disappearance of ferroelectricity in SBT thin films had the relationship with the reductive amounts of Bi in SBT. H2 played an important role in degradation of ferroelectric SBT thin films. This role could be attributed to its strong reduction activity during forming gas annealing.

Adsorption and desorption phenomena on thermally annealed multi-walled carbon nanotubes by XANES study

The multi-walled carbon nanotubes(MWCNTs) studied in this work were synthesized by the catalytic chemical vapor deposition(CCVD) process, and were thermally annealed by the hot filament plasma enhanced(HF PE) method at 550℃ for two hours.The x-ray absorption near edge structure(XANES) technique was used to investigate the adsorption and desorption phenomena of the MWCNTs at normal and grazing incidence angles.The adsorbates were found to have different sensitivities to the thermal annealing.The geometry of the incident beam consistently gave information about the adsorption and desorption phenomena.In addition, the adsorption of non-intrinsic potassium quantitatively affected the intrinsic adsorbates and contributed to increase the conductivity of the MWCNTs.The desorption of potassium was almost 70% greater after the thermal annealing.The potassium non-intrinsic adsorbates are from a physisorption mechanism whereas the intrinsic adsorbates result from chemisorption.

Thermally annealed gamma irradiated Ni/4H-SiC Schottky barrier diode characteristics

Thermal annealing effects on gamma irradiated Ni/4 H-SiC Schottky barrier diode(SBD) characteristics are analyzed over a wide range of temperatures(400–1100 °C). The annealing induced variations in the concentration of deep level traps in the SBDs are identified by thermally stimulated capacitance(TSCAP). A little decrease in the trap density at E_C – 0.63 eV and E_C –1.13 eV is observed up to the annealing temperature of 600 °C. Whereas, a gamma induced trap at E_C – 0.89 eV disappeared after annealing at 500 °C, revealing that its concentration(< 1013 cm-3) is reduced below the detection limit of the TSCAP technique.The electrical characteristics of irradiated SBDs are considerably changed at each annealing temperature. To understand the anomalous variations in the post-annealing characteristics, the interface state density distribution in the annealed SBDs is extracted.The electrical properties are improved at 400 °C due to the reduction in the interface trap density. However, from 500 °C, the electrical parameters are found to degrade with the annealing temperature because of the increase in the interface trap density.From the results, it is noted that the rectifying nature of the SBDs vanishes at or above 800 °C.

Influence of carrier gas H2 flow rate on quality of p-type GaN epilayer grown and annealed at lower temperatures

In this work, we study the influence of carrier gas H_2 flow rate on the quality of p-type GaN grown and annealed at lower temperatures. It is found that the concentration of H atoms in Mg-doped GaN epilayer can effectively decrease with appropriately reducing the carrier gas H_2 flow rate, and a high-quality p-type GaN layer could be obtained at a comparatively low annealing temperature by reducing the carrier gas H_2 flow rate. Meanwhile, it is found that the intensity and wavelength of DAP peak are changed as the annealing temperature varies, which shows that the thermal annealing has a remarkable effect not only on the activation of acceptors but also on the compensation donors.

Transformation of Nitrogen State in High-Level N-Doped Gem-Quality Diamond Crystal Annealed at High Temperature and High Pressure

The colourless IaA-type gem-quality diamond crystals containing a high concentration of nitrogen(1500–1700 ppm)were successfully prepared by annealing the as-grown Ib-type N-doped diamonds at a high temperature and high pressure in China-type cubic anvil high-pressure apparatus.Experiments were carried out at pressures of 6.5–7.0 GPa and temperatures from 1900 K to 2100 K.Annealing treatment on high-level N-doped diamond crystals shows that the colour of the diamond crystals is obviously reduced from green to colourless after annealing treatment within 1 h at a higher temperature,which is induced by nitrogen aggregation in the diamond lattice indicated by infrared(IR)spectroscopy.It is further revealed that active energy of the nitrogen atom transforming from the dispersed form to the aggregated form is much lower than that in the standard Ib-type diamond crystals with nitrogen concentration less than 300 ppm.The colourless IaA-type diamond crystal prepared by annealing at 2100 K displays the same properties in IR spectra as the high-quality natural diamonds which are classified into the IaA type.

Magnetic Properties and Oxygen Content of Nanocrystaline FeCuNbSiB Alloy Annealed in Hydrogen and Air

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Effect of Typical Elements on the Heredity of Hot-rolled and Annealed Texture in Non-oriented Electrical Steel

Macroscopic texture and microscopic orientation in hot-rolled and annealed sheets of nonoriented electrical steel were studied by XRD and EBSD techniques. The microstructure of hot-rolled and annealed samples was studied by OM. Experimental results indicate that a strong heredity is observed in texture evolution between hot-rolled texture and annealed texture. Typical elements have a large effect on the recrystallization microstructure and texture distribution. The texture distribution through thickness is highly affected by recrystallization in hot rolled sheets. The recrystallization is boosted by Si and Al. Goss grains originate from cracked initial <100> columnar grains. {110}<112>, {112}<111> and {111}<112> grains are related to Goss grains. In subsurface lay of hot rolled sheets, Al can strengthen Goss texture and weaken copper-type texture. {112}<111> texture and {110}<112> texture are strengthened by Si. In the central layers, {100}<001> texture and {111}<121> texture are weakened by Al. {100}<011> texture is increased by Al. Si can increase the proportion of γ-fiber texture and decrease that of {100}<011> texture. In annealed texture, {100}<001> texture and Goss texture are decreased by Al and Si. γ-fiber texture is increased by Si and {111}<121> texture is preferentially increased by Al. The recrystallized grain size is increased and iron loss of annealed sheets is reduced by Al and Si, which means that the magnetic properties are optimized by the Al and Si content.

Oxygen-Diffusion and Structural Modification in Air-Annealed Superconducting Bi_(2)Sr_(2)CaCu_(2)O_(y) Single Crystals

Bi_(2)Sr_(2)CaCu_(2)O_(y) single crystals were air-annealed at 300,400,600 and 750℃ for 20h in consequence.Measurements of ac susceptibility and x-ray diffraction showed that at annealing temperature below 400℃,the change of Tc was dominated by oxygen-diffusion involved in pervoskite unit and was strongly sample-dependent.This diffusion from pervoskite unit occurred earlier than that from Bi-O layers.At annealing temperature over 400℃,with the intercalation of excess oxygen into Bi-O layers,the hole concentration in the crystal was redistributed so that Bi-O reservoir fully determined superconductivity.From the changes of non-uniform strain in annealing process,it was found that structural modification was also closely correlated to superconductivity.

Effect of Nb on the Microstructure and Properties of Cold Rolled and Annealed Mo Microalloyed Bainitic Steel

Two kinds of low carbon bainitic steels,Nb-free Mo bearing and Nb + Mo addition steels,were cold rolled and annealed to investigate the effect of micro-alloying element Nb on the microstructure and properties of Mo microalloyed low carbon high strength bainitic steel. No precipitates were observed in Nb-free Mo bearing steel,whereas,two types of precipitates,i.e.,Nb( C,N) and composite( Nb,Mo)( C,N),were observed in the Nb + Mo microalloyed steel,resulting in precipitation strengthening. The strength of Mo bearing steel was improved by addition of Nb under the same annealing conditions. The grain size of Nb addition steel was almost the same as Nb-free steel. Unlike the obvious grain refinement and precipitation strengthening in hot rolling,the increase in yield strength of Nb addition steels in cold rolling and annealing mainly results from the precipitation strengthening,while the effect of grain refinement strengthening can be almost ignored.

Phase Evolution of Cubic ZnS Annealed in Mild Oxidizing Atmosphere

ZnS thin films are prepared by thermal evaporation of high-purity ZnS powder on quartz glass substrates.The samples were annealed in floating argon at temperatures from 300℃to 900℃.The effects of annealing temperature on the structural and optical properties were investigated by x-ray diffraction(XRD),scanning electron microscope(SEM)and optical absorption.The results show that annealing below 500℃is beneficial to improve the quality of ZnS films.When the annealing temperature exceeds 500℃,ZnS is gradually oxidized into ZnSO4,which has evident influences on the structural and optical properties of ZnS films.

Comparative Study of Earing Behavior in Cold Rolled-batch Annealed and Cold Rolled-Continuous Annealed of DoubleReduced (DR) Tinplate Steels

Two double cold reduction-drawn and redrawn(DRD) tinplate steels of the same chemistries that have been processed by continuous and batch annealing line have been researched. The composition of fibers were studied through X-ray diffraction. The results indicate that a strong intensity of {114}<110> was formed in the continuous annealing steel and a strong intensity of {111}<112> was formed in the batch annealing steel; not only that but the γ fiber slowly rotated to the low angel α fiber with the angel being about 30° nearly {112}<110>texture owing to the higher second reduction.

Effects of post-annealed floating gate on the performance of AlGaN/GaN heterostructure field-effect transistors

AlGaN/GaN heterostructure field-effect transistors(HFETs) with different floating gate lengths and floating gates annealed at different temperatures, are fabricated. Using the measured capacitance–voltage curves of the gate Shottky contacts for the AlGaN/GaN HFETs, we find that after floating gate experiences 600?C rapid thermal annealing, the larger the floating gate length, the larger the two-dimensional electron gas electron density under the gate region is. Based on the measured capacitance–voltage and current–voltage curves, the strain of the AlGaN barrier layer in the gate region is calculated, which proves that the increased electron density originates from the increased strain of the AlGaN barrier layer.