Surface morphology and photoluminescence properties of ZnO thin films obtained by PLD

ZnO thin films on Si(111) substrate were deposited by laser ablation of Zn target in oxygen reactive atmosphere, Nd-YAG laser with wavelength of 1 064 nm was used as laser source. XRD and FESEM microscopy were applied to characterize the structure and surface morphology of the deposited ZnO films. The optical properties of the ZnO thin films were characterized by photoluminescence. The UV and deep level (yellow-green) light were observed from the films. The UV light is the intrinsic property and deep level light is attributed to the existence of antisite defects (OZn). The intensity of UV and deep level light depends strongly on the surface morphology and is explained by the surface roughness of ZnO film. A strongly UV emission can be obtained from ZnO film with surface roughness in nanometer range.

Growth of n-type ZnO thin films by using mixture gas of hydrogen and argon

High-quality oxide semiconductor ZnO thin films were prepared on single-crystal sapphire and baAlO3 substrates by pulsed laser deposition （PLD） in the mixture gas of hydrogen and argon. Low resistivity n-type ZnO thin films with smoother surface were achieved by deposition at 600℃ in 1Pa of the mixture gas. in addition, ferromagnetism was observed in Co-doped ZnO thin films and rectification Ⅰ - Ⅴ curves were found in p-GaN/n-ZnO and p-CdTe/n-ZnO heterostructure junctions. The results indicated that using mixture gas of hydrogen and argon in PLD technique was a flexible method for depositing high-quality n-type oxide semiconductor films, especially for the multilayer thin film devices.

Effect of Substrates on the Properties of ZnO Thin Films Grown by Pulsed Laser Deposition

Polycrystalline zinc oxide (ZnO) thin films have been deposited at 450°C onto glass and silicon substrates by pulsed laser deposition technique (PLD). The used source was a KrF excimer laser (248 nm, 25 ns, 5 Hz, 2 J/cm2). The effects of glass and silicon substrates on structural and optical properties of ZnO films have been investigated. X-ray diffraction patterns showed that ZnO films are polycrystalline with a hexagonal wurtzite—type structure with a strong (103) orientation and have a good crystallinity on monocrystalline Si(100) substrate. The thickness and compositional depth profile were studied by Rutherford Backscattering spectrometry (RBS). The average transmittance of ZnO films deposited on glass substrate in the visible range is 70%.

Structural, Optical and Luminescence Properties of ZnO Thin Films Prepared by Sol-Gel Spin-Coating Method： Effect of Precursor Concentration

Transparent zinc oxide（ZnO） thin films are fabricated by a simple sol-gel spin-coating technique on glass substrates with different solution concentrations（0.3-1.2 M） using zinc acetate dehydrate [Zn（CH_3COO）_2·2H_2O] as precursor and isopropanol and monoethanolamine（MEA） as solvent and stabilizer, respectively. The molar ratio of zinc acetate dehydrate to MEA is 1.0. X-ray diffraction, ultraviolet-visible spectroscopy and photoluminescence spectroscopy are employed to investigate the effect of solution concentration on the structural and optical properties of the ZnO thin films. The obtained results of all thin films are discussed in detail and are compared with other experimental data.

Electrical and optical properties of Sb-doped ZnO thin films synthesized by sol–gel method

Sb-doped ZnO thin films with different values of Sb content （from 0 to 1.1 at.%） are deposited by the sol-gel dip- coating method under different sol concentrations. The effects of Sb-doping content, sol concentration, and annealing ambient on the structural, optical, and electrical properties of ZnO films are investigated. The results of the X-ray diffraction and ultraviolet-visible spectroscopy （UV-VIS） spectrophotometer indicate that each of all the films retains the wurtzite ZnO structure and possesses a preferred orientation along the c axis, with high transmittance （〉 90%） in the visible range. The Hall effect measurements show that the vacuum annealed thin films synthesized in the sol concentration of 0.75 mol/L each have an adjustable n-type electrical conductivity by varying Sb-doping density, and the photoluminescence （PL） spectra revealed that the defect emission （around 450 nm） is predominant. However, the thin films prepared by the sol with a concentration of 0.25 mol/L, despite their poor conductivity, have priority in ultraviolet emission, and the PL peak position shows first a blue-shift and then a red-shift with the increase of the Sb doping content.

Optical and Micro-Structural Properties of ZnO Thin Films Grown on Silicon Substrate by Pulsed Laser Deposition

ZnO thin films were deposited on n-Si (111) at various substrate temperatures and oxygen pressures by pulsed laser deposition (PLD) using a Nd∶YAG laser with the wavelength of 1064 nm. X-ray diffraction (XRD), photoluminescence (PL), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to analyze the microstructure, optical property and morphology of the ZnO thin films. A comparatively optimal crystallized ZnO thin film was obtained at the substrate temperature of 600 ℃ in oxygen pressure of 50 mTorr. The intensity of the luminescence strongly depends on the stoichiometry of the film as well as the crystalline quality.

Gap States of ZnO Thin Films by New Methods:Optical Spectroscopy,Optical Conductivity and Optical Dispersion Energy

The optical reflectance and transmittance spectra in the wavelength range of 300-2500 nm are used to compute the absorption coefficient of zinc oxide films annealed at different post-annealing temperatures 400, 500 and 600°C.The values of the cross point between the curves of the real and imaginary parts of the optical conductivity ɑ_1 and ɑ_1 with energy axis of films exhibit values that correspond to optical gaps and are about 3.25-3.3 eV. The maxima of peaks in plots dR/dλ and dT/dλ versus wavelength of films exhibit optical gaps at about 3.12-3.25 eV.The values of the fundamental indirect band gap obtained from the Tauc model are at about 3.14-3.2 eV. It can be seen that films annealed at 600°C have the minimum indirect optical band gap at about 3.15 eV. The films annealed at 600°C have Urbach＇s energy minimum of 1.38 eV and hence have minimum disorder. The dispersion energy d of films annealed at 500°C has the minimum value of 43 eV.

Crystallization Behavior and Properties of B-Doped ZnO Thin Films Prepared by Sol-Gel Method with Different Pyrolysis Temperatures

Boron-doped zinc oxide transparent （BZO） films were prepared by sol-gel method. The effect of pyrolysis temperature on the crystallization behavior and properties was systematically investigated. XRD patterns revealed that the BZO films had wurtzite structure with a preferential growth orientation along the c-axis. With the increase of pyrolysis temperature, the particle size and surface roughness of the BZO films increased, suggesting that pyrolysis temperature is the critical factor for determining the crystallization behavior of the BZO films. Moreover, the carrier concentration and the carrier mobility increased with increasing the pyrolysis temperature, and the mean transmittance for every film is over 90% in the visible range.

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 ℃.

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.

Induced growth of high quality ZnO thin films by crystallized amorphous ZnO

This paper reports the induced growth of high quality ZnO thin film by crystallized amorphous ZnO. Firstly amorphous ZnO was prepared by solid-state pyrolytic reaction, then by taking crystallized amorphous ZnO as seeds （buffer layer）, ZnO thin films have been grown in diethyene glycol solution of zinc acetate at 80 ℃. X-ray Diffraction curve indicates that the films were preferentially oriented [001] out-of-plane direction of the ZnO. Atomic force microscopy and scanning electron microscopy were used to evaluate the surface morphology of the ZnO thin film. Photoluminescence spectrum exhibits a strong ultraviolet emission while the visible emission is very weak. The results indicate that high quality ZnO thin film was obtained.

衬底温度对PLD方法生长Si(111)基ZnO薄膜结晶质量和发光特性的影响

在不同衬底温度下用脉冲激光沉积法(PLD)在n型硅(111)衬底上生长ZnO薄膜。通过对薄膜进行的X射线衍射(XRD)、傅里叶红外吸收(FTIR)、光致发光谱(PL)、透射电子显微镜(TEM)和选区电子衍射(SAED)的测量,研究了衬底温度对PLD方法制备的ZnO薄膜的结晶质量、发光性质以及微观结构的影响。发现在600℃的衬底温度下可以得到结晶质量最佳的ZnO薄膜。随着晶粒直径的减小,出现量子限制效应,在红外吸收和光致发光中的峰位均产生了蓝移。

PLD法生长硅基ZnO薄膜的特性

用脉冲激光沉积法(PLD)在n型硅(111)平面上生长ZnO薄膜。XRD在2θ为34°处出现了唯一的衍射峰,半高宽仅0.85°;傅里叶红外吸收(FTIR)在413.08cm–1附近出现了对应Zn—O键的红外光谱的特征吸收峰;光致发光(PL)测量发现了位于330,368,417和467nm处的室温光致发光峰;SEM和TEM显示了薄膜的表面形貌以及结晶程度。ZnO单晶薄膜具有c轴取向高度一致的六方纤锌矿结构。

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℃.

Angle-sensitive and fast photovoltage of silver nanocluster embeded ZnO thin films induced by 1.064-μm pulsed laser

Silver nanocluster embedded ZnO composite thin film was observed to have an angle-sensitive and fast photovoltaic effect in the angle range from -90° to 90° , its peak value and the polarity varied regularly with the angle of incidence of the 1.064-μm pulsed Nd：YAG laser radiation onto the ZnO surface. Meanwhile, for each photovoltaic signal, its rising time reached -2 ns with an open-circuit photovoltage of -2 ns full width at half-maximum. This angle-sensitive fast photovoltaic effect is expected to put this composite film a candidate for angle-sensitive and fast photodetector.

退火对用PLD法制备ZnO薄膜的发光影响

用脉冲激光沉积(PLD)方法在Si(111)和蓝宝石衬底上制备的氧化锌薄膜,在不同的退火温度和不同的退火氛围中进行了退火处理.退火温度及退火氛围对ZnO薄膜的结构和发光特性的影响用X射线衍射(XRD)谱和光致发光谱进行了表征.实验结果表明,随着退火温度的提高,ZnO薄膜的压应力减小,并向张应力转化.在不同的退火温度退火的薄膜的光致发光谱表明,随着退火温度的提高,薄膜的紫外发射逐渐增强,缺陷发射逐渐减小.在不同退火条件下的退火实验表明,在蓝宝石衬底上、氧气氛围中退火的薄膜,在700℃时呈现无应力,紫外发射强度对可见发射强度的比例最大.

Photoluminescence properties of ZnO thin films prepared by DC magnetron sputtering

ZnO thin films were prepared by direct current(DC)reactive magnetron sputtering under different oxygen partial pressures.And then the samples were annealed in vacuum at 450℃.The effects of the oxygen partial pressures and the treatment of annealing in vacuum on the photoluminescence and the concentration of six intrinsic defects in ZnO thin films such as oxygen vacancy(VO),zinc vacancy(VZn),antisite oxygen(OZn),antisite zinc(ZnO),interstitial oxygen(Oi)and interstitial zinc(Zni)were studied.The results show that a green photoluminescence peak at 520 nm can be observed in all the samples,whose intensity increases with increasing oxygen partial pressure;for the sample annealed in vacuum,the intensity of the green peak increases as well.The green photoluminescence peak observed in ZnO may be attributed to zinc vacancy,which probably originates from transitions between electrons in the conduction band and zinc vacancy levels,or from transitions between electrons in zinc vacancy levels and up valence band.

PLD法薄膜沉积条件对ZnO薄膜特性的影响

介绍了基于PLD方法制备的ZnO薄膜,在衬底温度(200-400℃)改变的情况下,分别对薄膜的表面结构和光致发光的情况做了研究,发现其相关特性并得出了制备薄膜的最佳条件。

Structure distortion, optical and electrical properties of ZnO thin films co-doped with Al and Sb by sol-gel spin coating

ZnO thin films co-doped with A1 and Sb with different concentrations and a fixed molar ratio of AlCl3 to SbCl3 at 1：2, are prepared by a sol-gel spin-coating method on glass annealed at 550 ℃ for 2 h in air. The x-ray diffraction results confirm that the ZnO thin films co-doped with Al distortion, and the biaxial stresses are 1.03× 10^8. 3.26× 10^8 and Sb are of wurtzite hexagonal ZnO with a very small 5.23 × 10^8, and 6.97× 10^8 Pa, corresponding to those of the ZnO thin films co-doped with Al and Sb in concentrations of 1.5, 3.0, 4.5, 6.0 at% respectively. The optical properties reveal that the ZnO thin films co-doped with Al and Sb have obviously enhanced transmittance in the visible region. The electrical properties show that ZnO thin film co-doped with Al and Sb in a concentration of 1.5 at% has a lowest resistivity of 2.5 Ω·cm.

Synthesis Sol-Gel Derived Highly Transparent ZnO Thin Films for Optoelectronic Applications

In this work, ZnO thin films were derived by sol-gel using two different techniques;dip coating and spin coating technique. The films were deposited onto glass substrate at room temperature using sol-gel composed from zinc acetate dehydrate, monoethanolamine, isopropanole, and de-ionized water, the films were preheated at 225?C for 15 min. The crystallographic structures of ZnO films were investigated using X-ray diffraction (XRD);the result shows that the good film was prepared at dip coating technique, it was polycrystalline and highly c-orientation along (002) plane, the lattice constant ratio (c/a) was calculated at (002), it was about 1.56. The structure of thin films, prepared by spin coating technique, was amorphous with low intensity and wide peaks. The optical properties of the prepared film were studied using UV-VIS spectrophotometer with the range 190 - 850 nm, and by using the fluorescence spectrometer. The optical characterization of ZnO thin films that were prepared by the dip coating method have good transmittance of about 92% in the visible region, it can be noted from the fluorescence spectrometer two broad visible emission bands centered at 380nm and 430 nm. The optical energy gaps for the direct and indirect allowed transitions were calculated, the values were equal 3.2 eV and 3.1 eV respectively. Dip coating technique create ZnO films with potential for application as transparent electrodes in optoelectronic devices such as solar cell.