偏压对磁控溅射ZnO薄膜的成核机制及表面形貌演化动力学的影响

利用反应射频磁控溅射技术,通过对基体施加负偏压溅射ZnO薄膜,探讨了固定偏压下ZnO薄膜的表面形貌随沉积时间的演化以及不同偏压对ZnO薄膜表面形貌的影响. 研究结果表明,在-100V的偏压下,随着沉积时间的增加,ZnO薄膜的表面岛尺寸不断减小,密度逐渐变大. ZnO在基片表面成核过程中的本征缺陷成核阶段和轰击缺陷成核阶段的生长指数分别为(0.45±0.03)和(0.22±0.04),低速率成核过程基本消失;随着偏压增大,表面岛的尺寸变大,表面起伏增加. 偏压不但可以改变ZnO薄膜的成核和生长过程,而且影响薄膜的晶体取向.     

沉积气压对磁控溅射制备ZnO薄膜的结构与光学性能影响

采用CS-400型射频磁控溅射仪在Si(111)和石英基底上成功的制备了ZnO薄膜,分别用XRD、SEM、紫外-可见光分光光度计和荧光分光光度计表征样品的结构和光学性质.实验表明,采用射频磁控溅射制备的ZnO薄膜具有六角纤锌矿结构的(002)峰和(101)峰的两种取向.在沉积气压>1.0Pa时所制备的ZnO薄膜具有(002)择优取向,并且十分稳定.SEM图表明,ZnO薄膜颗粒大小较为均匀,晶粒尺寸随着气压升高而变小,沉积气压不同时,薄膜样品的生长方式有所差异.在400～1000nm范围内,可以看出除O.5Pa下制备的ZnO薄膜外,其余ZnO薄膜在可见光区域的平均透过率超过80%,吸收边在380nm附近,所对应的光学带隙约为3.23～3.27eV,并随着沉积气压上升而变大.ZnO薄膜的PL谱上观察到了392nm的近紫外峰和419nm的蓝峰;沉积气压对Zno薄膜的发光峰位和峰强有影响.     

氧分压对直流磁控溅射制备 ZnO:Ga透明导电薄膜特性的影响

通过直流反应磁控溅射法在玻璃衬底上制备了掺镓ZnO（ZnO：Ga）透明导电薄膜，研究了氧分压对ZnO：Ga透明导电薄膜结构和电光学性能的影响．X射线衍射结果表明所制备的薄膜具有c轴择优取向的六角多晶结构．ZnO：Ga透明导电薄膜的晶粒尺寸强烈依赖于氧分压的大小，随着氧分压的增大薄膜的晶粒尺寸先增大后减小，在氧分压为0．30Pa时沉积的ZnO：Ga薄膜半高宽最小，晶粒尺寸最大．薄膜的电阻率随着氧分压的增大先减小后增大，沉积薄膜的最低电阻率可达3．50×10^-4Ω·cm．此外，所有ZnO：Ga薄膜在可见光范围内的平均透射率均超过90％．     

衬底离子束表面氮化对ZnO薄膜性质的影响

采用射频磁控溅射法在抛光硅片上沉积了一系列ZnO薄膜样品.通过对薄膜样品X射线衍射谱的分析、原子力显微图的观察、吸收光谱和荧光光谱的研究,发现Si衬底的离子束表面氮化对ZnO薄膜的晶体结构、表面形貌和光学性质有重要影响.在衬底温度为200℃、高纯氩氧比例为3:1、压强为1.5Pa的条件下,在经离子束表面氮化预处理的Si衬底上溅射沉积的ZnO薄膜,经450℃真空退火,成为高(0002)晶面取向的ZnO薄膜,并具有良好的光学性质.     

离子束反应溅射ZnO薄膜的晶体结构及光学、电学性质研究

采用离子束反应溅射法在玻璃基片上沉积了一系列ZnO薄膜样品.通过对薄膜样品XRD谱的分析,发现基片温度和溅射氧分压是同时影响ZnO薄膜沿c轴择优取向生长的重要因素.在基片温度350 ℃,氧分压1.3 的溅射条件下,得到了完全沿c轴取向生长的只有(002)晶面的ZnO薄膜.薄膜的吸收光谱测量结果表明,基片温度和氧分压对ZnO薄膜的光学禁带宽度有重要影响.不同氧分压、不同基片温度制备的薄膜电阻率相差很大.     

氩气压强对直流磁控溅射法制备ZnO:Nb透明导电薄膜性质的影响

室温下,利用直流磁控溅射法在玻璃衬底上制备了铌掺杂氧化锌(NZO)薄膜,研究了溅射压强(2～12 Pa)对薄膜结构、残余应力、表面形貌及其光电性能的影响.X射线衍射测量结果表明,所有样品都具有c轴择优取向的六角纤锌矿多晶结构,薄膜应力随压强的增大而减小.扫描电镜表明,随着溅射压强的增大,薄膜表面逐步趋向平整光滑、均匀致密.当溅射压强为10 Pa时,制备的ZnO∶Nb薄膜的最低电阻率可达3.52× 10-4 Ω·cm,残余应力为-0.37 GPa.压强由2Pa增大到12 Pa时,光学带隙由3.29eV增大到3.43 eV.紫外-可见透射光谱表明,所有薄膜在可见光范围内平均透过率均超过87％.     

RF溅射稀土掺杂ZnO薄膜的结构与发光特性

通过射频磁控溅射技术在Si(111)衬底上制备了未掺杂和La、Nd掺杂ZnO薄膜.XRD分析表明,ZnO薄膜具有c轴择优生长,La、Nd掺杂ZnO薄膜为纳米多晶薄膜.AFM观测,La、Nd掺杂ZnO薄膜表面形貌较为粗糙.从薄膜的室温光致光谱中看到,所有薄膜都出现了395 nm的强紫光峰和495 nm的弱绿光峰,La掺杂ZnO薄膜的峰强度增大,Nd掺杂ZnO薄膜的峰强度减弱,分析了掺杂引起PL峰强度变化的原因.     

多组分掺杂ZnO薄膜的微观结构及电学性能研究

采用射频磁控溅射法在Si(111)衬底上制备多组分掺杂ZnO薄膜,研究了衬底温度和氧分压对Bi、Cr、Sb、Mn和Co掺杂ZnO薄膜的晶体结构、表面形貌及电学性能的影响。结果表明:随着衬底温度的升高,ZnO(002)衍射峰相对强度先增强后减弱;薄膜表面粗糙度先减小后增大。随着氧分压的增大,ZnO的(101)、(102)和(103)衍射峰消失,薄膜呈优异的(002)择优取向生长。在衬底温度为300℃、氧分压为50%时,Bi、Cr、Sb、Mn和Co所引起的缺陷和氧过剩引起的本征缺陷,共同形成受主态的复合缺陷,导致晶界势垒激增。此时,薄膜有最优化的压敏电压、非线性常数和漏电流,分别达到7.05V、20.83和0.58μA/mm~2。     

沉积速率对ZnO薄膜生长过程和微结构影响的分子反应力场方法研究

应用基于反应力场的分子动力学方法研究了ZnO薄膜(001)表面作为衬底的薄膜沉积生长过程,初步讨论了500K时,沉积速率(1.5、2.5和3.5m/s)变化对沉积薄膜质量的影响。结果表明沉积速率约3.5m/s时,衬底结构最稳定,沉积原子结构径向分布函数曲线特征峰尖锐、明显,有序度较高;每原子层密度分析表明优化的沉积温度和沉积速率下,沉积形成的薄膜结构稳定而又致密。在预置衬底表面平坦的情况下薄膜呈现一种岛状的生长模式,近衬底区Zn—O键呈现理想的生长取向,而近表面区则两种生长取向共存,导致其生长前锋交汇处形成新的有序缺陷及氧空位。     

基底温度对磁控溅射制备ZnO薄膜性能的影响

利用射频磁控溅射,在Si基底上制备了ZnO薄膜.采用电子薄膜应力分布测试仪、X射线衍射和傅立叶变换红外光谱仪等检测手段研究了基底温度对其应力、微结构及光学性能的影响.ZnO薄膜在(002)晶面具有良好的c轴取向.在基底温度为200～300 ℃范围内,ZnO薄膜具有良好的结晶性能和较均匀的应力分布.红外光谱在430cm-1附近出现了Zn-O键的振动吸收峰.     

Effect of the oxygen pressure on the photoluminescence properties of ZnO thin films 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 1064 nm was used as laser source. The experiments were performed at laser energy density of 31 J/cm², substrate temperature of 400 °C and various oxygen pressures (5–65 Pa). X-ray diffraction was applied to characterize the structure of the deposited ZnO films and the optical properties of the ZnO thin films were characterized by photoluminescence with an Ar ion laser as a light source using an excitation wavelength of 325 nm. The influence of the oxygen pressure on the structural and optical properties of ZnO thin films was investigated. It was found that ZnO film with random growth grains can be obtained under the condition of oxygen pressure 5–65 Pa. It will be clearly shown that the grain size and the formation of intrinsic defects depend on the oxygen partial pressure and that high optical quality of the ZnO films is obtained under low oxygen pressure (5 Pa, 11 Pa) conditions.     

Effects of oxygen pressure on the structure and photoluminescence of ZnO thin films

A series of ZnO thin films were deposited on silicon (100) substrate at 473 K by using facing target RF magnetron sputtering system at different oxygen pressure in this paper. The structure, surface morphology and photoluminescence of the ZnO thin films were characterized by X-ray diffraction, atomic force microscopy (AFM), and photoluminescence spectra (PL), respectively. The results showed that only a (002) peak of hexagonal wurtzite appeared in all ZnO thin films, indicating that ZnO films exhibited strong texture. With increasing the oxygen pressure, the results indicated that the ZnO film deposited at 1.2 Pa Ar pressure and 0.6 Pa oxygen pressure had the best preferential C-axis orientation and the weakest compressive stress. Meanwhile, AFM observation showed that ZnO film deposited at pure Ar had the highest surface roughness. With the increment of oxygen pressure, the surface roughness decreased gradually. In addition, PL measurement showed that the ZnO film deposited at 1.2 Pa Ar pressure and 0.6 Pa oxygen pressure had the strongest ultraviolet emission and the weakest blue emission.     

PLD工艺制备高质量ZnO/Si异质外延薄膜

采用脉冲激光沉积工艺在不同条件下以Si(111)为衬底制备了Zno薄膜.通过对不同氧压下(0～50Pa)沉积的样品的室温PL谱测试表明,氧气氛显著地提高了薄膜的发光质量,在50Pa氧气中沉积的ZnO薄膜具有最强的近带边UV发射.XRD测试说明在氧气氛中得到的薄膜结晶质量较差,没有单一的(002)取向.利用-低温(500℃)沉积的ZnO薄膜作缓冲层,得到了高质量的ZnO外延膜.与直接沉积的ZnO膜相比,生长在缓冲层上的ZnO膜展现出规则的斑点状衍射花样,而且拥有更强的UV发射和更窄的UV峰半高宽(98meV).对不同温度下沉积的缓冲层进行了RHEED表征,结果表明,在600～650℃之间生长缓冲层,有望进一步改善ZnO外延膜的质量.     

Effect of the oxygen partial pressure on the microstructure and optical properties of ZnO:Cu films

Cu-doped zinc oxide (ZnO:Cu) films were deposited on Si substrates using radio frequency reactive magnetron sputtering at different oxygen partial pressures. The effect of oxygen partial pressure on the microstructures and optical properties of ZnO:Cu thin films were systematically investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and fluorescence spectrophotometer. The results indicated that the grain orientation of the films was promoted by appropriate oxygen partial pressures. And with increasing oxygen partial pressure, the compressive stress of the films increased first and then decreased. The photoluminescence (PL) of the samples were measured at room temperature. A violet peak, two blue peaks and a green peak were observed from the PL spectra of the four samples. The origin of these emissions was discussed and the mechanism of violet emission of ZnO:Cu thin films were suggested.     

Pulsed electron beam deposition of transparent conducting Al-doped ZnO films

Good quality transparent conducting Al-doped ZnO films were deposited on quartz substrates from a high purity target using pulsed electron deposition (PED). Two series of films were made, one deposited at room temperature but at four pressures, viz., 0.7, 1.3, 2.0 and 2.7 Pa of oxygen and one deposited at 1.3 Pa oxygen pressure but at the substrate temperature ranged from room temperature to 600 °C. In order to evaluate the effect of substrate temperature and oxygen pressure on the properties of obtained films, various characterization techniques were employed including X-ray diffraction, stylus profiler, scanning electron microscope, optical spectrophotometer and electrical resistivity. For the first series films, the optimal oxygen pressure of 1.3 Pa was found to bring about the appropriate energetic deposition atoms which results in the best crystallinity. For the second series films, the lowest resistivity was obtained in the film grown at 400 °C. An attempt was made to reduce the resistivity by lowering the oxygen pressure to 0.5 Pa which was the lower limit of working pressure of the PED system. The obtained results indicate that PED is a suitable technique for growing transparent conducting ZnO films.     

Property variations of direct-current reactive magnetron sputtered copper oxide thin films deposited at different oxygen partial pressures

Cuprous oxide (Cu₂O) and cupric oxide (CuO) thin films were deposited on glass substrates at different oxygen partial pressures by direct-current reactive magnetron sputtering of pure copper target in a mixture of argon and oxygen gases. Oxygen partial pressure was found to be a crucial parameter in controlling the phases and, thus, the physical properties of the deposited copper oxide thin films. Single-phase Cu₂O thin films with cubic structure were obtained at low oxygen partial pressure between 0.147 Pa and 0.200 Pa while higher oxygen partial pressure promoted the formation of CuO thin films with base-centered monoclinic structure. Polycrystalline Cu₂O thin films deposited with oxygen partial pressure at 0.147 Pa possessed the lowest p-type resistivity of 1.76 Ω cm as well as an optical band gap of 2.01 eV. On the other hand, polycrystalline CuO thin films deposited with oxygen partial pressure at 0.320 Pa were also single phase but showed a n-type resistivity of 0.19 Ω cm along with an optical band gap of 1.58 eV.     

Effects of annealing atmosphere on thermoelectric signals from ZnO films

Zinc oxide epilayer films were grown on vicinal cut sapphire substrates by pulsed laser deposition with in situ annealing oxygen pressures varied from 0 to 10 × 10³ Pa. The best crystalline quality was obtained for ZnO layer with annealing oxygen pressure of 6 × 10³ Pa. Laser induced thermoelectric voltage (LITV) were observed along the tilting angle orientation of the substrate when the pulsed KrF excimer laser of 248 nm were irradiated on the films. The largest LITV signal was measured for the film grown at 6 × 10³ Pa annealing oxygen pressure. According to the measured LITV signals, Seebeck anisotropy was evaluated and was found to range from 3 to 12 μV/K for ZnO films annealed at different oxygen pressures from 2 to 10 × 10³ Pa. It is suggested that oxygen ambient plays an important role in the electronic properties of the ZnO films.     

Structural, Morphological and Optical Properties of ZnO Thin Films Grown on γ-LiAlO2 Substrate by Pulsed Laser Deposition

ZnO thin films were deposited on the substrates of (100) γ-LiAlO2 at 400, 550 and 700℃ using pulsed laser deposition (PLD) with the fixed oxygen pressure of 20 Pa, respectively. When the substrate temperature is 400℃, the grain size of the film is less than 1 μm observed by Leitz microscope and measured by X-ray diffraction (XRD). As the substrate temperature increases to 550℃, highly-preferred c-orientation and high-quality ZnO film can be attained.While the substrate temperature rises to 700℃, more defects appears on the surface of film and the ZnO films become polycrystalline again possibly because more Li of the substrate diffused into the ZnO film at high substrate temperature. The photoluminescence (PL) spectra of ZnO films at room temperature show the blue emission peaks centered at 430 nm. We suggest that the blue emission corresponds to the electron transition from the level of interstitial Zn to the valence band. Meanwhile, the films grown on γ-LiAlO2 (LAO) exhibit green emission centered at 540 nm, which seemed to be ascribed to excess zinc and/or oxygen vacancy in the ZnO films caused by diffusion of Li from the substrates into the films during the deposition.     

Influence of oxygen partial pressure on the structure and photoluminescence of direct current reactive magnetron sputtering ZnO thin films

The effects of oxygen partial pressure on the structure and photoluminescence (PL) of ZnO films were studied. The films were prepared by direct current (DC) reactive magnetron sputtering with various oxygen concentrations at room temperature. With increasing oxygen ratio, the structure of films changes from zinc and zinc oxide phases, single-phase ZnO, to the (002) orientation, and the mechanical stresses exhibit from tensile stress to compressive stress. Films deposited at higher oxygen pressure show weaker emission intensities, which may result from the decrease of the oxygen vacancies and zinc interstitials in the film. This indicates that the emission in ZnO film originates from the oxygen vacancy and zinc interstitial-related defects. From optical transmittance spectra of ZnO films, the plasma edge shifts towards the shorter wavelength with the improvement of film stoichiometry.     

Influence of oxygen pressure on structural,optical and magnetic properties of pure ZnO films

In this paper, we study the influence of oxygen pressure on structural, optical and magnetic properties of pure ZnO films. The chemical compositions and thickness of the film were estimated by Rutherford backscattering spectrometry measurements. X-ray diffraction patterns show all the films are in single phase and preferred along (002) orientation. With an increase of oxygen pressure, grain growth and average root mean square roughness is found to be increased. It is found that the intensity of UV emission peak increases whereas visible emission peak decreases in intensity with an increase of oxygen pressure. From the magnetization measurements, it is observed that ZnO film grown without oxygen pressure shows an enhanced ferromagnetic behaviour than that of the films grown with oxygen pressure of 0.05 and 0.1 mbar.