Influence of Annealing on Microstructure and Photoluminescence Properties of Al-Doped ZnO Films

Effect of annealing temperature and time on the microstructure and photoluminescence(PL)properties of Al doped ZnO thin films deposited on Si(100)substrates by sol-gel method was investigated.An X-ray diffraction(XRD)was used to analyze the structural properties of the thin films.All the thin films have a preferential c-axis orientation,which are enhances in the annealing process.It is found from the PL measurement that near band edge(NBE)emission and deep-level(DL)emissions are observed in as-grown ZnO∶Al thin films.However,the intensity of DLE is much smaller than that of NBE.Enhancement of NBE is clearly observed after thermal annealing in air and the intensity of NBE increases with annealing temperature.Results also show that the PL spectrum is dependent not only on the processing temperature but also on the processing time.The DLE related defects can not be removed by annealing,and on the contrary,the annealing conditions actually favor their formation.

Synthesis and photoluminescence properties of single-crystal ZnO hexagonal pyramids by PEG400-assisted thermal decomposition route

Large-scale synthesis of ZnO hexagonal pyramids was achieved by a simple thermal decomposition route of precursor at 240 oC in the presence of PEG400. The precursor was obtained by room-temperature solid-state grinding reaction between Zn（CH3COO）2-2H2O and Na2CO3. Crystal structure and morphology of the products were analyzed and characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and high-resolution transmission electron microscopy （HRTEM）. The results of further experiments show that PEG400 has an important role in the formation of ZnO hexagonal pyramids. Difference between the single and double hexagonal pyramid structure may come from the special thermal decomposition reaction. The photoluminescence （PL） spectra of ZnO hexagonal pyramids exhibit strong near-band-edge emission at about 386 nm and weak green emission at about 550 nm. The Raman-active vibration at about 435 cm-1 suggests that the ZnO hexagonal pyramids have high crystallinity.

Morphology, photoluminescence and gas sensing of Ce-doped ZnO microspheres

Ce-doped ZnO microspheres were solvothermally prepared, and their microstructure, morphology, photoluminescence, and gas sensing were investigated by X-ray diffractometer, field emission scanning electron microscopy, transmission electron microscopy, fluorescence spectrometer and gas sensing analysis system. The results showed that the Ce-doped ZnO microspheres were composed of numerous nanorods with a diameter of 70 nm and a wurtzite structure. Ce-doping could cause a morphological transition from loose nanorods assembly to a tightly assembly in the microspheres. Compared with pure ZnO, the photoluminescence of the Ce-doped microspheres showed red-shifted UV emission and an enhanced blue emission. Particularly, the Ce-doped ZnO sensors exhibited much higher sensitivity and selectivity to ethanol than that of pure ZnO sensor at 320 °C. The ZnO microspheres doped with 6% Ce (mole fraction) exhibited the highest sensitivity (about 30) with rapid response (2 s) and recovery time (16 s) to 50×10?6 ethanol gas.

Effects of high-dose Ge ion implantation and post-implantation annealing on ZnO thin films

This paper reports that ion implantation to a dose of 1 ×10^17 ions/cm^2 was performed on c-axis-orientated ZnO thin films deposited on （0001） sapphire substrates by the sol-gel technique. After ion implantation, the as-implanted ZnO films were annealed in argon ambient at different temperatures from 600 - 900 ℃. The effects of ion implantation and post-implantation annealing on the structural and optical properties of the ZnO films were investigated by x-ray diffraction （XRD）, photoluminescence （PL）. It was found that the intensities of （002） peak and near band edge （NBE） exitonic ultraviolet emission increased with increasing annealing temperature from 600- 900 ℃. The defect related deep level emission （DLE） firstly increased with increasing annealing temperature from 600 - 750 ℃, and then decreased quickly with increasing annealing temperature. The recovery of the intensities of NBE and DLE occurs at ～850℃ and ～750℃ respectively. The relative PL intensity ratio of NBE to DLE showed that the quality of ZnO films increased continuously with increasing annealing temperature from 600 - 900 ℃.

Temperature-dependent photoluminescence on organic inorganic metal halide perovskite CH_3NH_3Pb I_(3-)Cl_ prepared on ZnO/FTO substrates using a two-step method

Temperature-dependent photoluminescence characteristics of organic-inorganic halide perovskite CH3NH3Pb I3-xClx films prepared using a two-step method on ZnO/FTO substrates were investigated. Surface morphology and absorption characteristics of the films were also studied. Scanning electron microscopy revealed large crystals and substrate coverage. The orthorhombic-to-tetragonal phase transition temperature was-140 K. The films＇ exciton binding energy was 77.6 ± 10.9 meV and the energy of optical phonons was 38.8 ± 2.5 meV. These results suggest that perovskite CH3NH3Pb I（3-x）Clx films have excellent optoelectronic characteristics which further suggests their potential usage in perovskitebased optoelectronic devices.

Effect of annealing atmosphere on magnetic properties of pure ZnO and Na:ZnO films

Pure ZnO and Zn0.96Na0.04O films were grown on quartz substrates by sol-gel technology.The XRD analysis revealed that all thin films had hexagonal wurtzite structure and obvious c-axis preferred orientation.Ferromagnetism was precisely measured by an alternating gradient magnetometer (AGM).To explore the nature original ferromagnetism,the effect of annealing atmosphere on magnetic properties of the films was studied.Compared with pure ZnO,magnetic hysteresis loops showed that doping Na atoms enhanced saturation magnetism.The mag-netism of the films annealed in the air atmosphere was significantly better than that in the O2 atmosphere.The photoluminescence (PL) spec-trum analysis suggested that the ferromagnetism was due to the defects in the films.

Effect of annealing treatment on morphologies and gas sensing properties of ZnO nanorods

The high-temperature stabilization of ZnO nanorods synthesized by hydrothermal treatment was investigated. The structure and morphologies of ZnO nanorods were characterized by XRD and SEM, respectively. The thermal stability of ZnO nanorods was also detected by thermal gravity analyzing. Thermal annealing treatment results indicate that ZnO nanorods are fundamentally stable when annealing temperature is lower than 600 ℃. When annealing temperature is beyond 600℃, the diameters of ZnO nanorods obviously decrease and the aggravating tendency of nanorods between each other also increase. Annealing treatment can greatly influence the gas sensing properties of ZnO nanorods. Comparing with ZnO nanorods without annealing treatment, the gas sensing property of ZnO nanorods to H2 with concentration of 2.5×10-6 can increase from 2.22 to 3.56. ZnO nanorods annealed at 400 ℃ exhibit optimum gas sesing property to H2 gas.

Fabrication of ZnO films by radio frequency magnetron sputtering and annealing

ZnO thin films were deposited on Si（111） substrates through a radio frequency （rf） magnetron sputtering system. Then the samples were annealed at different temperatures in air ambience and ammonia ambience respectively. The structure and composition of the ZnO films were studied by X-ray diffraction （XRD） and X-ray photoelectron spectroscopy （XPS）. The morphology of the samples was studied by scanning electron microscopy （SEM）. Measured results show that ZnO films with hexagonal wurtzite structure were grown on Si（111） substrates when annealed in the two ambiences. The volatilization process of ZnO in the ammonia ambience at high temperature was discussed and the mechanism of the reaction was analyzed.

Effect of annealing temperature on the microstructure and optoelectrical properties of ZnO thin films and their application in self-powered accelerometers

This paper reports a piezoelectric nanogenerator(NG) with a thickness of approximately 80 μm for miniaturized self-powered acceleration sensors. To deposit the piezoelectric zinc oxide(ZnO) thin film, a magnetron sputtering machine was used. Polymethyl methacrylate(PMMA) and aluminum-doped zinc oxide(AZO) were used as the insulating layer and the top electrode of the NG, respectively. The experimental results show that the ZnO thin films annealed at 150℃ exhibited the highest crystallinity among the prepared films and an optical band gap of 3.24 eV. The NG fabricated with an AZO/PMMA/ZnO/stainless steel configuration exhibited a higher output voltage than the device with an AZO/ZnO/PMMA/stainless steel configuration. In addition, the annealing temperature affected the open-circuit voltage of the NGs;the output voltage reached 3.81 V when the annealing temperature was 150℃. The open-circuit voltage of the prepared self-powered accelerometer increased linearly with acceleration. In addition, the small NG-based accelerometer, which exhibited excellent fatigue resistance, can be used for acceleration measurements of small and lightweight devices.

Synthesis and photoluminescence study on ZnO nano-particles

A new technique, namely low pressure sputtering, has been developed to fabricate Zn nanoparticles, with a subsequent oxidation to synthesize ZnO nanoparticles in the ambient atmosphere at 500℃. The synthesized ZnO nanoparticle has a size of 6-8 nm with a preferred orientation of c-axis. The produced ZnO nanoparticles have a good UV photoluminescence （PL） emission energy of 3.349 eV with a significant enhancement of donor-acceptor pair emission located at 3.305 eV which implies a number of donor and acceptor bounded excitons existing in the synthesized ZnO nano particles. The near band edge PL emission of the fabricated ZnO is dominated by the bounded excitons at 10 K.

Effect of annealing atmosphere on ferromagnetism in Mn doped ZnO films

This paper reports that Zn0.97Mn0.03O thin films have been prepared by radio-frequency sputtering technology followed by rapid thermal processing in nitrogen and oxygen ambient respectively. Magnetic property investigation indicates that the films are ferromagnetic and that the Curie temperature （Tc） is over room temperature. It is observed that the saturation magnetization of the films increases after annealing in nitrogen ambience but decreases after annealing in oxygen. Room temperature photoluminescence spectra indicate that the amount of defects in the films differs after annealing in the different ambiences. This suggests that the ferromagnetism in Zn0.97Mn0.03O films is strongly related to the defects in the films.

The effects of post-thermal annealing on the optical parameters of indium-doped ZnO thin films

Indium-doped ZnO thin films are deposited on quartz glass slides by RF magnetron sputtering at ambient temperature. The as-deposited films are annealed at different temperatures from 400℃ to 800 ℃ in air for 1 h. Transmittance spectra are used to determine the optical parameters and the thicknesses of the films before and after annealing using a nonlinear programming method, and the effects of the annealing temperatures on the optical parameters and the thickness are investigated. The optical band gap is determined from the absorption coefficient. The calculated results show that the film thickness and optical parameters both increase first and then decrease with increasing annealing temperature from 400℃ to 800℃. The band gap of the as-deposited ZnO：In thin film is 3.28 eV, and it decreases to 3.17 eV after annealing at 400℃. Then the band gap increases from 3.17 eV to 3.23 eV with increasing annealing temperature from 400℃ to 800℃.

Effects of Heat-treatment Temperature on Eu^(3+) and Li^+ Co-doped ZnO Photoluminescence by Sol-gel Process

The photoluminescence （PL） characteristics of Eu^3＋ and Li^＋ co-doped ZnO PL materials against heat-treatment temperature were discussed. The PL xerogel and powder samples were prepared by solgel process. The emission spectra of all samples showed two broad bands peaking at 590 nm and 620 nm under UV-Vis excitation. But the relative intensity of red PL （620 nm） was much greater than that of green PL （590 nm） of the same sample, that s to say, the red color was the main luminescence. With heat-treatment temperature increase, the two kinds of colors PL intensity decreased, and both the red and green PL intensity of the xerogel samples was much greater than those of powder samples respectively. The XRD patterns revealed that Eu^3＋ ions were successfully incorporated in ZnO crystals in xerogel samples. When heat-treatment temperature reached 350 ℃, the Eu^3＋ began to separate out of the ZnO crystals and Eu2O3 crystals came into being. When the powder sample was subjected to UV-Vis excitation, the energy transfered from the host ZnO emission to Eu^3＋ became weaker than the xerogel sample.

Research on the photoluminescence of spectral broadening by rapid thermal annealing on InAs/GaAs quantum dots

Photoluminescence (PL) test was conducted to investigate the effect of rapid thermal annealing (RTA) on the opticalperformance of self-assembled InAs/GaAs quantum dots (QDs) at the temperatures of 16 and 300 K. It was found that after RTAtreatment, the PL spectrum of the QDs sample had a large blue-shift and significantly broadened at 300 K. Compared with theas-grown InAs QDs sample, the PL spectral width has increased by 44.68 meV in the InAs QDs sample RTA-treated at800 ℃. The excitation power-dependent PL measurements showed that the broadening of the PL peaks of the RTA-treatedInAs QDs should be related to the emission of the ground state (GS) of different-sized InAs QDs, the InAs wetting layer (WL)and the In0.15Ga0.85As strain reduction layer (SRL) in the epitaxial InAs/GaAs layers.

Quenching Photoluminescence of Eu(III) by Cu(II) in ZnO:Eu3++Cu2+ Compounds by Solution Combustion Method

In this study Cu2++Eu3+ co-doped ZnO(ZnO/Cu2++Eu3+) solid solution powders were synthesized by solution combustion method using as oxidant agent zinc nitrate hexahydrate and as fuel urea;the Cu2+ concentrations were 0, 1, 2, 3, 10, and 20 %Wt;the Eu3+ ion concentration was fixed in 3%Wt. The samples after were annealed at 900°C by 20 h in air. The structural results showed the largely presence of a wurtzite solid solution of Cu2++Eu3+doped ZnO, at high Cu2+ doping CuO and Eu2CuO4 phases are also present. Morphological properties were analyzed using scanning electron microscopy (SEM) technique. However it is important to remark that the Cu2+ ions suppress the Eu3+ ion photoluminescence (PL) by means of an overlap mechanism between Cu2+ absorption band and Eu3+emission band (e.g. 5D0→7F2) of the Eu3+ emission spectra.

Influence of preparation methods on photoluminescence properties of ZnO films on quartz glass

The influence of preparation methods on the photoluminescence properties of ZnO film was studied.Two methods were applied to fabricate ZnO films in a conventional pulsed laser deposition apparatus.One is high temperature(500-700 ℃)oxidation of the metallic zinc film that is obtained by pulsed laser deposition.The other is pulse laser ablation of Zn target in oxygen atmosphere at low temperature(100-250 ℃).The photoluminescence property was detected by PL spectrum.The room temperature PL spectra of the ZnO films obtained by oxidation method show single violet luminescence emission centered at 424 nm(or 2.90 eV)without any accompanied deep-level emission and UV emission.The violet emission is attributed to interstitial zinc in the films.Nanostructure ZnO film with c-axis(002)orientation is obtained by pulsed laser deposition.The ZnO film deposited at 200 ℃ shows single strong ultraviolet emission.The excellent UV emission is attributed to the good crystalline quality of the film and low intrinsic defects at such low temperature.

Effects of Annealing on Luminescence of ZnO Films Deposited on Si Substrates by RF Magnetron Sputtering

Effects of growth ambience, annealing ambience and temperature on the photolumi nescence (PL) emission properties of ZnO films deposited on Si (100) substrates by RF magnetron sputtering have been investigated. After annealing, the crystal quality of ZnO films was markedly improved, and the intensity of UV emission peak increased obviously. By varying the flow rate ratio of 02/Ar, annealing atmosphere in oxygen-deficient or oxygen-rich ambience and heating temperature during deposition, the evolution of peak intensities and positions for blue and green emission is formed. This is attributed to the deposition and annealing parameters that control the desorptions and adsorptions of oxygen atoms on the films, and leads to the changes of concentrations of Zinc and oxygen vacancies in the films.

Effects of Annealing on the Structural and Photoluminescent Properties of Ag-Doped ZnO Nanowires Prepared by Ion Implantation

ZnO nanowires deposited on Si substrates were prepared by thermal evaporation of a mixture of ZnO and carbon powder. Ag ions with an energy of 63 keV and a dose of 5×1015 ions/cm-2 were implanted into the as-prepared ZnO nanowires. After ion implantation, the Ag-implanted ZnO nanowires were annealed in air at different temperatures from 600℃ to 1000℃. Effects of ion implantation and thermal annealing on the structural and photoluminescent （PL） properties of the ZnO nanowires were investigated by transmission electron microscopy （TEM）, selected area energy dispersive X-ray spectroscopy （SAEDX）, X-ray diffraction （XRD）, and fluorescence spectrophotometry. TEM, HR-TEM, and SAEDX analyses demonstrated that efficient doping of Ag was achieved by ion implantation and the subsequent annealing process. XRD patterns revealed that the hexagonal wurtzite structure of ZnO nanowires was maintained after ion implantation. Photoluminescent emissions of ZnO nanowires were decreased significantly by Ag implantation but could be recovered by thermal annealing. The mechanism of the influence of ion implantation and annealing on the PL intensity was assessed.

Synthesis of ZnO：Dy Nanopowder and Photoluminescence of Dy^3＋ in ZnO

A type of dysprosium-doped ZnO （ZnO：Dy） nanopowder was synthesized by high temperature calcinations. XRD was used to analyze the structure. Photoluminescence spectra were used to study the optical characteristic. PL of ZnO：Dy shows two different spectra which are broad band resulted from the defect of Dy in ZnO and sharp lines from the 4f→4f transition of isolated Dy^3 ＋ luminescence center. The emission and excitation spectra depend on the excitation wavelength and the concentration of Dy^3＋ . The broad bands with peaks at 600 and 760 nm are attributed to the recombination from an electron of the defect Dy in ZnO to a hole in VB.

Novel photoluminescence properties of InAlO_3(ZnO)_m superlattice nanowires

One-dimension InAlO3 （ZnO）m superlattice nanowires were successfully synthesized via chemical vapor deposition. Transmission electron microscopy measurements reveal that the nanowires have a periodic layered structure along the （0001） direction. The photoluminescence properties of InAlO3（ZnO）m superlattice nanowires are studied for the first time. The near-band-edge emissions exhibit an obvious red shift due to the formation of the localized tail states. The two peaks centered at 3.348 eV and 3.299 eV indicate a lever phenomenon at the low-temperature region. A new luminescence mechanism is proposed, combined with the special energy band structure of InAlO3（ZnO）m.