Electroless Nickel Plating and Electroplating on FBG Temperature Sensor

Metal-coated fiber Bragg grating（FBG）temperature sensors were prepared via electroless nickel（EN）plating and tin electroplating methods on the surface of normal bare FBG.The surface morphologies of the metal-coated layers were observed under a metallographic microscope.The effects of pretreatment sequence,pH value of EN plating solution and current density of electroplating on the performance of the metal-coated layers were analyzed.Meanwhile, the Bragg wavelength shift induced by temperature was monitored by an optical spectrum analyzer.Sensitivity of the metal-coated FBG（MFBG）sensor was almost two times that of normal bare FBG sensor.The measuring temperature of the MFBG sensor could be up to 280℃,which was much better than that of conventional FBG sensor.

Influence of Annealing on Properties of ZnO Films Grown via Plasma-enhanced MOCVD

The structural and the optical properties of ZnO films with high quality grown via plasma-enhanced metal\|organic chemical vapour deposition(MOCVD) on C-plane sapphire substrate were studied. The crystallinity and the optical properties of the films are greatly improved having been annealed in oxygen plasma atmosphere. The structure, the band gap and the binding energy of O 1s electrons, and the molar ratio of O to Zn were determined by X-ray diffraction(XRD), photoluminescence(PL) and X-ray photoelectron scan methods. For both the annealed and the as-grown films, the exciton peak features were observed at room temperature. The band-edge photoluminescence of the annealed film is much stronger than that of the as-grown film, and the exciton peak relating to the deep level at 439 nm disappears. The molar ratio of O to Zn in the annealed film is 0 91, while it is 0 78 for the as-grown film.

Preparation of Copper Phthalocyanine Crystals Using Solvothermal Synthesis

A novel solvothermal synthesis method for the direct growth of B-form crystals of copper phthalocyanine（CuPc） is presented in this article. With quinoline as solvent, crystals were grown after cooling the reaction mixture of 1,3-diiminoisoindoline and copper oxide, heated for 9 h at 270 ℃, to room temperature in an autoclave. These high quality crystals were suitable for characterization measurements. The single-crystal diffraction data show a monoclinic system unit cell： a=1.4668（3） nm, b=0.48109（10） nm, c=1.9515（7） nm, a=90°, B=121.04（2）°, r=90°, where the corresponding cell volume is 1.17991 nm^3. Needle-like single crystals of CuPc up to 10.5 mm in length were obtained. The influences of different temperatures, reaction time and solvent volume on the crystal yields were also discussed. Optimum reaction conditions were 10 mL of quinoline, at 270 ℃ for 8 h.

Influence of Transparent Anode on Luminescent Performance of Near-infrared Organic Light-emitting Diodes

The optical transmission（200--2000 nm）, sheet resistance and work functions of indium-tin oxide（ITO）（100 Ω/）, ITO（12 Ω/）, zinc-oxide（ZnO）, aluminum-doped ZnO（AZO） and polyaniline（PANI） films were investigated. Near-infrared organic light-emitting diodes（NIR-OLEDs） emitting around 1.54 μm based on Er（DBM）3Phen with ITO（100 Ω/）, ITO（12 Ω/） and PANI as anodes, respectively, were fabricated. The device structure was anode/4＂-tris（N-3-methylphenyl-N-phenyl-amino）-triphenylamine（m-MTDATA）/ N,N＇-di-l-naphthyl- N,N＇-diphenylbenzidine（NPB）/Er（DBM）3Phen/tris-（8-hydroxyquinoline） aluminum（Alq3）/A1. The results suggest that the performance of NIR-OLEDs with ITO（100 Ω/）, which has a lower Sn content, as anodes appear to be better than that of NIR-OLEDs with ITO（12 Ω/） and PANI as anodes, respectively. The high N1R transmittance of ITO（100 Ω/） is a major reason for the relatively high NIR EL efficiency. The more balanced holes and electrons in the device based on ITO（100 Ω/） are another reasons.

Effects of ZnO Buffer Layer Thickness on Properties of Mg_xZn_(1-x)O Thin Films Deposited by MOCVD

High-quality MgxZn1-xO thin films were grown on sapphire（0001 ） substrates with a ZnO buffer layer of different thicknesses by means of metal-organic chemical vapor deposition. Diethyl zinc, bis-cyclopentadienyl-Mg and oxygen were used as the precursor materials. The crystalline quality, surface morphologies and optical properties of the Mg, Zn1-xO films were investigated by X-ray diffraction, atomic force microscopy and photoluminescence spectrometry. It was shown that the quality of the MgxZn1-xO thin films depends on the thickness of the ZnO buffer layer and an Mg, Zn1-xO thin film with a ZnO buffer layer whose thickness was 20 nm exhibited the best crystal-quality, optical properties and a flat and dense surface.

Studies on Crystal Orientation of ZnO Film on Sapphire Using High-throughout X-ray Diffraction

The orientation of the nano-columnar ZnO films grown on sapphire using the technique of metal-organic chemical vapor deposition （MOCVD） exhibits deviation because of the mismatch between the crystal lattices of the films and the sapphire substrate. A high-throughout X-ray diffraction method was employed to determine the crystal orientation of the ZnO films at a time scale of the order of minutes based on the general area detection diffraction system （GADDS）. This rapid, effective, and ready method, adapted for characterizing the orientation of the nano-columnar crystals is used to directly explain the results of observation of the X-ray diffraction images, by the measurements of the orientations of the crystal columns of the ZnO films along c-axis and in parallel to ab plane.

Photoluminescence Properties of Two-dimensional Planar Layer and Three-dimensional Island Layer for ZnO Films Grown Using MOCVD

ZnO（002） films with different thicknesses ranging from 7 to 300 nm were grown on sapphire（006） substrates via metal-organic chemical vapor deposition （MOCVD）. The two-dimensional（2D） planar layer and the three-dimensional（3D） island layer were studied by using of X-ray diffraction（XRD） rocking curves and atomic force microscopy （AFM）. The room temperature photoluminescence （PL） spectra show a blue shift of the peak positions of the uhraviolet（UV） emission with increasing film thickness. The blue shift is remarkably high（393-380 nm） when an increase in film thickness（7-15 nm） is accompanied by the change of structure from a 2D planar layer to a 3D island layer. The PL spectra at 77 K also indicate that there are different transition mechanisms in the film thickness from a 2D planar layer to a 3D island layer near the 2D layer region.

Structural and Optical Properties of ZnO Films with Different Thicknesses Grown on Sapphire by MOCVD

ZnO（002） films with different thicknesses, grown on Al2O3 （006） substrates by metal-organic chemical vapor deposition（ MOCVD）, were etched by Ar ion beams. The samples were examined by D8 X-ray diffraction, scanning electron microscopy（SEM）, and photoluminescence（PL） spectrometry. The structural properties vary with the increasing thickness of the films. When the film thickness is thin, the phi（Φ） scanning curves for ZnO（103） and sapphire（116） substrate show the existence of two kinds of orientation relationships between ZnO films and sapphire, which are ZnO（002）//Al2O3 （006）, ZnO（ 100）//Al2O3 （110） and ZnO（002）//Al2O3 （006）, ZnO（ 110）//Al2O3 （110）. When the thickness increases to 500 nm there is only one orientation relationship, which is ZnO（002）// Al2O3 （006）, ZnO [ 100]//Al2O3 [ 110]. Their photoluminescence（PL） spectra at room temperature show that the optical properties of ZnO films have been greatly improved when increasing the thickness of films is increased.

Properties of p-NiO/n-GaN Diodes Fabricated by Magnetron Sputtering

The p-NiO thin film is prepared by radio frequency magnetron sputtering on the n-GaN/sapphire substrate to form p-NiO/n-GaN heterojunction diodes.The structural,optical and electrical properties of the p-NiO thin film are investigated.The results indicate that the NiO film has good crystal qualities and stable p-type conductivities.The current-voltage measurement of the p-NiO/n-GaN diode exhibits typical rectifying behaviour with a turn-on voltage of about 2.2 V.Under forward bias,a prominent ultraviolet emission centered at 375 nm is observed at room temperature.Furthermore,the mechanism of the light emission is discussed in terms of the band diagrams of the heterojunction in detail.

Improvement of the Quality of a GaN Epilayer by Employing a SiN_(x) Interlayer

GaN epilayers with a porous SiN_(x) interlayer were grown by metal-organic chemical vapor deposition on c-plane sapphire substrates.It is found that the crystalline qualities are significantly improved with SiN_(x) growth.The improvement is attributed to the reduction of the density of threading dislocations(TDs)by an over-growth process of GaN grown on a SiN_(x) interlayer.The influence mechanism of SiN_(x) interlayers on GaN growth mode is also discussed.

A Study of GaN Grown on SiH_(4) Pre-Treated 6H-SiC Substrates

GaN thin films are grown on Si-terminated (0001) 6H-SiC substrates pre-treated with SiH_(4) in a metal organic chemical vapor deposition system.The influence of the SiH_(4) pre-treatment conditions on the SiC surface is carefully investigated.It is found that SiH_(4) could react with the SiC surface oxide,which will change the surface termination.Moreover,our experiments demonstrate that SiH_(4) pre-treatment can distinctly influence the AlGaN nucleation layer and the basic characteristics of GaN.

Ultraviolet-Visible Electroluminescence of a p-ZnO:As/n-Si Device Formed by the GaAs Interlayer Doping Method

Arsenic doped p-type ZnO films were grown on n-type silicon substrates using the GaAs interlayer doping method.Under our growth conditions the main doping element is arsenic,which was confirmed by x-ray photoelectroscopy.X-ray diffraction measurements revealed that the p-ZnO:As film was still in the(002)preferred orientation.The Hall test showed that the hole concentration of the p-ZnO:As film was 2.6×1017 cm−3.The acceptor level was located at 135 meV above the valance band maximum,according to the low-temperature photoluminescence results.We then fabricated a p-ZnO:As/n-Si heterojunction light-emitting device.Its current-voltage curve showed the typical rectifying behavior of a p–n diode.At forward current injections,the electroluminescence peaks,which cover the ultraviolet-to-visible region,could be clearly detected.

Crystalline, Optical and Electrical Properties of NiZnO Thin Films Fabricated by MOCVD

NiZnO thin films are grown on c-plane sapphire substrates by using a photo-assisted metal organic chemical vapor deposition(MOCVD)system.The effect of the Ni content on the crystalline,optical and electrical properties of the films are researched in detail.The NiZnO films could retain a basic wurtzite structure when the Ni content is less than 0.18.As Ni content increases,crystal quality degradation could be observed in the x-ray diffraction patterns and a clear red shift of the absorption edge can be observed in the transmittance spectrum.Furthermore,the donor defects in the NiZnO film can be compensated for effectively by increasing the Ni content.The change of Ni content has an important effect on the properties of NiZnO films.

Effects of GaAs on Photoluminescence Properties of Self-Assembled InAs Quantum Dots

Room temperature photoluminescence(PL)spectra of InAs self-assembled quantum dots(QDs)deposited on a GaAs/InP and InP substrate are investigated.From the PL spectra,we find that the peak position of InAs QDs appears red-shift from 0.795 to 0.785 eV after we insert a thin tensile GaAs layer between InAs QD layer and InP buffer layer.In order to explain this phenomenon in theory,we examine the strain tensor in InAs quantum dots by using a valence force field model and use a five-band k.p formalism to obtain the electronic structure.The calculated results show that the ground transition energy decreases from 0.789 to 0.780 eV when the thin GaAs layer is inserted.Therefore,the PL peak position should appear red-shift as shown in the experiment.