PLD方法生长ZnO/Si异质外延薄膜的研究

用脉冲激光沉积法在Si(111)衬底上制备了ZnO薄膜。RHEED和XRD测试表明,直接沉积在Si衬底上的ZnO薄膜为多晶薄膜,且薄膜的结晶质量随衬底温度的升高而下降。相比之下,生长在一低温同质缓冲层上的ZnO薄膜则展现出规则的斑点状RHEED图像,说明它们都是外延生长的高质量ZnO薄膜。XRD与室温PL谱分析表明,外延ZnO薄膜的质量随衬底温度的升高得到明显的改善。在650℃生长的样品具有最好的结构和发光特性,其(002)衍射峰的半高宽为0.185°,UV峰的半高宽仅为86meV。     

衬底温度对PLD法制备ZnO薄膜结构及发光特性的影响

在60Pa的高氧压气氛中,用脉冲激光沉积法以Si(111)为衬底在不同温度下制备了ZnO薄膜.RHEED和XRD结果表明,所有样品都是c轴高度择优取向的多晶ZnO薄膜.随衬底温度的升高,ZnO薄膜(002)衍射峰的半高宽不断减小,从0.227～0.185°.对(002)衍射峰的2θ值分析表明,650℃下生长的ZnO薄膜几乎处于无应力的状态,而在较低或较高温度下生长的薄膜中都存在着一定程度的c轴压应力.室温PL谱测试说明在650℃生长的ZnO薄膜具有最强的紫外发射峰和最窄的UV峰半高宽(83meV).在700℃得到的样品PL谱中,检测到一个位于3.25eV处的低能发射峰.经分析,该峰可能是来自于施主-受主对(DAP)的跃迁.     

锌膜氧化制备氧化锌薄膜的紫光发射

通过锌膜在金属锌熔点(419℃)以上温度和50Pa的氧气压力下退火氧化的方法制备ZnO薄膜,研究了退火温度对ZnO薄膜组织结构及发光性能的影响.ZnO薄膜的室温光致发光谱是由发光中心在424nm处的单一紫光组成.随着退火温度的升高,紫光的强度增加,当温度超过600℃时紫光的强度反而降低.在50Pa氧气压力下,紫光的发射归因于电子从价带到锌间隙原子(Zni)缺陷之间的跃迁.     

锌膜退火氧化制备ZnO薄膜的单一紫光发射性能

通过锌膜在金属锌熔点以上的温度退火氧化的方法制备ZnO薄膜,研究了氧气压力对ZnO薄膜发光性能的影响.ZnO薄膜的室温光致发光谱是由发光中心在413nm～424nm处的单一紫光组成.随着氧气压力的增加,紫光的强度增加并且发光中心由424nm偏移到413nm.在低氧气压力下(50 Pa～500Pa),紫光的发射归因于电子从价带到锌间隙原子(Zni)之间的跃迁.在高氧气压力下(5000Pa～23000Pa),锌间隙原子(Zni)和锌空位(VZn)缺陷都和紫光发射有关.     

离子束溅射与射频溅射制备的ZnO薄膜的特性分析

分别采用两种不同的方法制备了ZnO薄膜.①离子束溅射法(IBD),在Si(001)衬底上制备锌膜后在氧气氛炉中退火;②射频溅射法(RF),在Si(001)衬底上制备ZnO薄膜后在氧气氛炉中退火.利用X射线衍射仪和原子力显微镜(AFM)以及电感、电容、电阻综合测试仪(LCR)对两种方法制备的ZnO薄膜的结构、形貌和导电性进行了比较研究.结果表明,离子束溅射的锌膜经热氧化后得到的ZnO薄膜生长的单向性较差,表面粗糙度较大,薄膜的电阻率也比较高.     

PLD法在c面蓝宝石衬底上制备纤锌矿ZnS外延薄膜

采用脉冲激光沉积方法以ZnS为靶材c面蓝宝石为衬底制备了一系列的ZnS薄膜,并采用四圆单晶衍射仪研究了薄膜的晶体结构及其与衬底的取向关系。首先研究了沉积温度对ZnS薄膜质量的影响,结果表明,所有制备的ZnS薄膜均为六方纤锌矿结构;在衬底温度为750℃时所制备的薄膜具有较好的晶体质量,并表现出与蓝宝石衬底明确的外延关系[ZnS(001)∥Al_2O_3(001)且ZnS(110)∥Al_2O_3(110)]。进一步研究了在750℃下加入不同厚度的ZnO缓冲层对于ZnS薄膜晶体质量的影响,结果表明在沉积ZnS薄膜前先沉积一层ZnO薄膜缓冲层可以进一步有效提高ZnS薄膜的晶体质量和面外取向性,其中在沉积时间为2min的ZnO缓冲层上制备的ZnS外延薄膜晶体质量最好,其(002)面摇摆曲线半高宽为1.35°。本文结论对于研究ZnS薄膜制备光电器件具有重要的意义。     

Si(111)衬底上多层石墨烯薄膜的外延生长

利用固源分子束外延(SSMBE)技术, 在Si(111)衬底上沉积碳原子外延生长石墨烯薄膜, 通过反射式高能电子衍射(RHEED)、红外吸收谱(FTIR)、拉曼光谱(RAMAN)和X射线吸收精细结构谱(NEXAFS)等手段对不同衬底温度(400、600、700、800℃)生长的薄膜进行结构表征. RAMAN和NEXAFS结果表明: 在800℃下制备的薄膜具有石墨烯的特征, 而 400、600和700℃生长的样品为非晶或多晶碳薄膜. RHEED和FTIR结果表明, 沉积温度在600℃以下时C原子和衬底Si原子没有成键, 而衬底温度提升到700℃以上, 沉积的C原子会先和衬底Si原子反应形成SiC缓冲层, 且在800℃沉积时缓冲层质量较好. 因此在Si衬底上制备石墨烯薄膜需要较高的衬底温度和高质量的SiC缓冲层.     

SiO2/Si衬底制备ZnO薄膜及表征

本文报道了利用脉冲激光沉积技术在热氧化p型硅衬底上生长ZnO外延薄膜.引入高阻非晶SiO2缓冲层,有效地降低了检测过程中单晶衬底对ZnO薄膜的电学性能影响.利用XRD,SEM,Hall和PL对其进行研究.结果表明,在衬底温度为500℃时,生长的ZnO薄膜具有优良的晶体质量,电学性能和发光性能.     

射频溅射ZnO作为GaN厚膜生长缓冲层的工艺研究

采用射频磁控溅射法制备出了适用于HVPE-GaN厚膜生长的ZnO缓冲层,利用X射线衍射(XRD)和原子力显微镜(AFM)和光致发光(PL)等分析方法表征了ZnO缓冲层以及HVPE-GaN厚膜的晶体性能。实验结果表明,采用溅射功率为60W、氩气压强为2.0Pa、蓝宝石衬底为室温条件下的溅射工艺获得了(0002)单一取向、晶界清晰、晶粒尺寸均一的ZnO薄膜,以它为缓冲层获得的GaN厚膜XRD的(0002)衍射峰半高宽(FWHM)为265secarc,室温PL谱未见明显黄光发射带。     

AlN/Si衬底上ZnO薄膜的择优取向生长

当ZnO薄膜直接沉积在Si衬底上时,由于ZnO与Si的晶格失配度大,不易于获得高质量的ZnO薄膜.因此,选择合适的衬底材料沉积ZnO薄膜,对提高其质量非常重要.本文采用射频磁控溅射法,通过在Si(100)衬底上预沉积AlN作为ZnO薄膜生长的缓冲层,获得了择优取向的ZnO薄膜.我们还讨论了ZnO薄膜在AlN/Si衬底上的取向生长机理.     

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.     

Influence of oxygen pressure on the structural, electrical and optical properties of VO2 thin films deposited on ZnO/glass substrates by pulsed laser deposition

The influence of oxygen pressure on the structural and electrical properties of vanadium oxide thin films deposited on glass substrates by pulsed laser deposition, via a 5-nm thick ZnO buffer, was investigated. For the purposes of comparison, VO₂ thin films were also deposited on c-cut sapphire and glass substrates. During laser ablation of the V metal target, the oxygen pressure was varied between 1.33 and 6.67 Pa at 500 °C, and the interaction and reaction of the VO₂ and the ZnO buffer were studied. X-ray diffraction studies showed that the VO₂ thin film deposited on a c-axis oriented ZnO buffer layer under 1.33 Pa oxygen had (020) preferential orientation. However, VO₂ thin films deposited under 5.33 and 6.67 Pa were randomly oriented and showed (011) peaks. Crystalline orientation controlled VO₂ thin films were prepared without such expensive single crystal substrates as c-cut sapphire. The metal-insulator transition properties of the VO₂/ZnO/glass samples were investigated in terms of electrical conductivity and infrared reflectance with varying temperatures, and the surface composition was investigated by X-ray photoelectron spectroscopy.     

Effect of oxygen partial pressure on the structural and optical properties of sputter deposited ZnO nanocrystalline thin films

We report the influence of deposition parameters such as oxygen partial pressure and overall sputtering pressure on the structural and optical properties of the as-grown ZnO nanocrystalline thin films. The films were prepared by dc magnetron sputtering using Zn metal target under two different argon and oxygen ratios at various sputtering pressures. Microstructure of the films was investigated using X-ray diffraction and scanning electron microscopy. Optical properties of the films were examined using UV-Visible spectrophotometer. The results show that the films deposited at low oxygen partial pressure (10%) contain mixed phase (Zn and ZnO) and are randomly oriented while the films deposited at higher oxygen partial pressure (30%) are single phase (ZnO) and highly oriented along the c-axis. We found that the oxygen partial pressure and the sputtering pressure are complementary to each other. The optical band gap calculated from Tauc's relation and the particle size calculation were in agreement with each other.     

氧分压对磁控溅射ZnO薄膜生长行为和光学特性的影响

采用反应射频磁控溅射方法, 在Si(001)基片上制备了具有高$c$轴择优取向的ZnO薄膜. 利用原子力显微镜、X射线衍射、透射光谱和室温光致荧光光谱等分析技术, 研究了氧分压对薄膜的表面形貌和光学特性的影响. 研究结果显示: 0.04～0.23Pa的氧分压范围内, ZnO薄膜存在三个不同的生长模式, 薄膜生长模式转变的临界氧分压分别位于0.04～0.08Pa和0.16～0.19Pa之间; 在0.16Pa以下时, ZnO薄膜的表面岛呈+c取向的竹笋状生长; 当氧分压>0.19Pa时, 薄膜的表面岛以-c取向生长为主; ZnO薄膜的折射率、光学带隙宽度以及PL光谱强度均随着氧分压的增大而增大, 氧分压为0.19Pa时, 薄膜的发光峰最窄, 其半峰宽为88meV.     

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.     

Dependence of ferromagnetic properties on growth oxygen partial pressure in boron-doped ZnO thin films

Boron-doped ZnO films were prepared by pulsed laser deposition technique. Magnetic, electrical, and optical properties of Zn_1?x B _x O films have been studied. It is found that the magnetic properties of the Zn_1?x B _x O films are sensitive to growth oxygen partial pressure. The films deposited under a high oxygen partial pressure of about 10?Pa appear to be ferromagnetic insulators at room temperature (RT). However, when the oxygen partial pressure decreases to 1.2?Pa, the films are non-ferromagnetic conductors at RT. Zn vacancies, which can be controlled by the oxygen partial pressure, are shown to be essential for realizing ferromagnetism (FM); on the other hand, the n-type nature of ZnO has no contribution to the FM observed in the B-doped ZnO films.     

Study of ZnO layers growth by pulsed laser deposition from Zn and ZnO targets

The article deals with structural properties of ZnO thin layers prepared on Si (111) by pulsed laser deposition at different pressures (1-35 Pa) of ambient oxygen in the deposition chamber. The growth temperature was 400 °C and a pulsed Nd:YAG laser was used at a wavelength of 355 nm. Two parallel sets of samples deposited by ablation of different targets (a sintered ceramic pellet of ZnO and a pure metallic Zn target) were examined. The samples were characterized by different analytical methods: scanning electron microscope (SEM), secondary ion mass spectroscopy (SIMS), and X-ray diffraction (XRD). The prepared layers exhibited columnar structure and uniform preferred c-axis orientation. The results showed that deposition of the high quality of ZnO films fabricated from both targets is comparable, except for those obtained at low (1 Pa) pressures.     

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 laser deposition and photoluminescence measurements of ZnO thin films on flexible polyimide substrates

In order to assess the potential of zinc oxide (ZnO) in flexible electronics applications, we created continuous ZnO films on polymeric substrates for evaluation of structural and optical properties. Specifically, we have used pulsed laser deposition to deposit ZnO films with thickness of several microns on flexible free-standing polyimide substrates. A KrF excimer laser (248 nm) operated at fluences of 3.0-6.2 J/cm² was used. ZnO films were deposited at temperatures between room temperature and 300 °C under O₂ atmosphere at a pressure of 50 Pa. Good flexibility characterizes the obtained layers and X-ray diffraction measurements show that films present all reflections of hexagonal ZnO. We discuss luminescence measurements on the films in relation to the complex interface phenomena expected in our samples.