Growth and characteristics of ZnO films on growth side of freestanding diamond substrate dependent on buffer layer thickness

We report the growth and properties of highly c-axis oriented ZnO films, by radio-frequency magnetron sputtering, on the growth side of freestanding chemical vapor deposited diamond film-substrate. Low-temperature ZnO buffer layer is required for the formation of continuous ZnO films. The morphology, structure, and optical properties of the ZnO films deposited are strongly dependent on the thickness of the buffer layer. The optimized thickness of ZnO buffer layer is about 10 nm to realize high-quality ZnO films having small compressive stress and high intensity ultraviolet emission. The ZnO/diamond (growth side) system is available for the applications in numerous fields, especially for high performance surface acoustic wave devices.     

PET纤维基AZO透明导电薄膜溅射工艺参数的优化

室温下,结合正交实验表,用射频磁控溅射在涤纶(PET)非织造布基材上生长AZO(Al2O3:ZnO)纳米结构薄膜.采用四探针测量仪测试AZO薄膜的方块电阻,用原子力显微镜(AFM)分析薄膜微结构;通过正交分析法对实验L9(33)AZO薄膜的性能指标进行分析.实验结果表明:溅射厚度对AZO薄膜导电性能起主导作用,其次为氩气压强和溅射功率;同时,得出制备AZO薄膜的最佳工艺为:溅射功率150W、厚度100m和气压0.2Pa,该参数下样品的方块电阻为1.633×103Ω,AZO纳米颗粒的平均直径约为69.4nm.     

用于高频声表面波器件的CVD金刚石衬底的研究

使用纳米金刚石粉研磨工艺预处理硅片衬底抛光面,在低气压成核的条件下,以丙酮和氢气为反应物,采用传统的热丝辅助化学气相沉积法,制备了自支撑金刚石膜;通过射频磁控溅射法沉积氧化锌薄膜在自支撑金刚石膜的成核面,形成氧化锌/自支撑金刚石膜结构.通过光学显微镜、扫描电镜及原子力显微镜测试自支撑金刚石膜成核面的表面形貌.研究结果表明:成核期的低气压有助于提高成核密度,成核面表面粗糙度约为1.5 nm;拉曼光谱显示1334 cm-1附近尖锐的散射峰与金刚石SP3键相对应,成核面含有少量的石墨相,且受到压应力的作用;ZnO/自支撑金刚石膜结构的XRD谱显示,氧化锌薄膜有尖锐的(002)面衍射峰,是c轴择优取向生长的.     

直流磁控溅射功率对溅射生长GZO薄膜光电性能的影响

本文采用直流磁控溅射沉积系统在玻璃基底上沉积镓掺杂氧化锌(GZO)薄膜,将溅射功率从120W调整到240W,步长为30W,研究功率变化对GZO薄膜的晶体结构、表面形貌、光学性能和电学性能的影响。结果表明,溅射功率对GZO薄膜电阻率有显著的影响。溅射功率为210W时薄膜呈现最低电阻率为3.31×10~(-4)Ω·cm,可见光波段平均光学透光率接近84%。随着溅射功率的增加,薄膜表面形貌和生长形态发生较大变化,并直接得到具有一定凸凹不平的微结构,GZO薄膜的致密性先增加后降低。     

High quality epitaxial ZnO films grown on solid-phase crystallized buffer layers

High quality epitaxial ZnO films on sapphire (110) plane have been fabricated on ZnO homo-buffer layers crystallized via solid-phase epitaxially (SPE). The SPE-ZnO films are fabricated by annealing of amorphous ZnON (a-ZnON) films deposited by RF magnetron sputtering. During annealing, the a-ZnON films are oxidized and converted to ZnO crystal. X-ray diffraction (XRD) analysis shows that the resultant films are epitaxially grown on the sapphire substrates. By using the SPE-ZnO films as homo-buffer layers, the ZnO films with high crystallinity, which are deposited by RF magnetron sputtering, are fabricated. The full width at half-maximum of XRD patterns for 2θ-ω and ω scan of (002) plane are 0.094° and 0.12°, respectively, being significantly small compared with 0.24° and 0.55° for the films without buffer layers. Thus utilizing SPE buffer layers is very promising to obtain epitaxial ZnO films with high crystallinity.     

The role of the Zn buffer layers in the structural and photoluminescence properties of ZnO films on Zn buffer layers deposited by RF magnetron sputtering

Highly c-axis oriented ZnO thin films were grown on Si (100) substrates with Zn buffer layers. Effects of the Zn buffer layer thickness on the structural and optical qualities of ZnO thin films were investigated for the ZnO films with the buffer layers 90, 110, and 130 nm thick using X-ray diffraction (XRD), photoluminescence (PL) and atomic force microscopy (AFM) analysis techniques. It was confirmed that the quality of a ZnO thin film deposited by RF magnetron sputtering was substantially improved by using a Zn buffer layer. The highest ZnO film quality was obtained with a Zn buffer layer 110 nm thick. The surface roughness of the ZnO thin film increases as the Zn buffer layer thickness increases.     

Electrodeposition of ZnO nanowires with controlled dimensions for photovoltaic applications: Role of buffer layer

The role of a ZnO buffer layer on the electrodeposition of ZnO nanowire arrays was analyzed. ZnO buffer layers were deposited on conducting glass substrates by spray pyrolysis and electrodeposition. The electrodeposited ZnO buffer layer resulted in a collection of open-packed small grains (∼ 20 nm), while the sprayed layers were comprised of close-packed grains with size in the range of 15-100 nm. The ZnO nanowire arrays electrodeposited on ZnO buffer layers exhibited increased nanowire density (by factors of 6× and 3×, for electrodeposited and sprayed buffer layers, respectively) compared to arrays deposited directly on naked substrates, demonstrating that ZnO nanocrystalline layers can be used to increase nucleation sites for nanowire growth. On the other hand, nanowire diameters were tailored from 45 to 160 nm as a function of the size of the grains in the buffer layer. The influence of crystallographic orientation of the buffer layer was also analyzed.     

Effect of ZnO buffer layer on AZO film properties and photovoltaic applications

Aluminum-doped ZnO (AZO) transparent conducting films were deposited on glass substrates with and without intrinsic ZnO (i-ZnO) buffer layers by a home made and low cost radio-frequency (RF) magnetron sputtering system at room temperature in pure argon ambient and under a low vacuum level. The films were examined and characterized for electrical, optical, and structural properties for the application of CIGS solar cells. The influence of sputter power, deposition pressure, film thickness and residual pressure on electrical and optical properties of layered films of AZO, i-ZnO and AZO/i-ZnO was investigated. The optimization of coating process parameters (RF power, sputtering pressure, thickness) was carried out. The effects of i-ZnO buffer layer on AZO films were investigated. By inserting thin i-ZnO layers with a thickness not greater than 125 nm under the AZO layers, both the carrier concentration and Hall mobility were increased. The resistivity of these layered films was lower than that of single layered AZO films. The related mechanisms and plasma physics were discussed. Copper indium gallium selenide (CIGS) thin film solar cells were fabricated by incorporating bi-layer ZnO films on CdS/CIGS/Mo/glass substrates. Efficiencies of the order of 7–8% were achieved for the manufactured CIGS solar cells (4–5 cm² in size) without antireflective films. The results demonstrated that RF sputtered layered AZO/i-ZnO films are suitable for application in low cost CIGS solar cells as transparent conductive electrodes.     

Influence of ZnO buffer layers on the optoelectronic properties in Ga-doped ZnO thin films prepared by RF magnetron sputtering on PET substrates

The influence of ZnO buffer layers on the optoelectronic properties in Ga-doped ZnO (GZO) thin films deposited on polyethylene terephthalate (PET) substrates by RF magnetron sputtering was investigated. The resistivity in GZO/ZnO bilayer films decreases significantly more than one order of magnitude than that in GZO film without a ZnO buffer layer. X-ray diffraction results show that the significant improvement of electrical properties is not related to the crystalline quality. Based on X-ray photoelectron spectroscopy analysis, it is suggested that the decrease in resistivity after the introduction of ZnO buffer layers is ascribed to the restraint of diffusion of moisture and gas from PET substrates to GZO thin films. The moisture and gas diffused into GZO films will be absorbed on the films’ surface in the form of negatively charged oxygen species acting as acceptors. Fifty nm buffer layer is thick enough to achieve the best effect, with further increase of the ZnO buffer layer thickness, the resistivity in the samples will increase due to the parallel effect of ZnO and GZO layers. The introduction of ZnO buffer layers has no obvious influence on the average transmittance in the visible range which is ~90 % high for all samples.     

Coalescence of magnetron-sputtered silver islands affected by transition metal seeding (Ni, Cr, Nb, Zr, Mo, W, Ta) and other parameters

Silver thin films were deposited on various base layers using magnetron sputtering. The onset of coalescence of silver islands was evaluated using in situ conductivity measurements. The substrates included glass and silicon, with base layers of ZnO:Al 4 at.% at various thickness and additional thin seed layers of transition metals. It is shown that certain conditions promote coalescence, and in particular the following seed conditions: tungsten (1.0 nm), molybdenum (0.1 nm), zirconium (0.5 nm), and nickel (0.1-0.2 nm). In the absence of transition metal seeding, earlier onset of coalescence occurred at the thinnest of the ZnO:Al 4 at.% base layers (5 nm) and the lowest sputtering power (50 W), indicating that the substrate-film system is not in thermodynamic equilibrium.     

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。     

Effect of LP-buffer on the structure of ZnO thin films prepared on glass substrate using RF magnetron sputtering

The ZnO thin films with preferential C-orientation and smooth surface have been prepared using an RF magnetron sputtering method by the insertion of low-power (LP) sputtered ZnO buffer. The XRD results show that the C-orientation of the ZnO buffer layer deposited under the RF power of 30 W is much better than that deposited under higher RF power. With the increase of the LP-buffer thickness, the C-orientation as well as the crystal quality of ZnO films improves, the surface becomes smooth and the RMS roughness decreases from 88.4 Å to 38.5 Å. The ZnO lattice is independent of the insertion of LP buffer.     

氧氩流量比对ZnO薄膜的微结构及其发光特性的影响

在室温下,利用射频磁控反应溅射法分别在硅片和石英玻璃上制备ZnO薄膜。通过控制O2/Ar流量比,研究O2/Ar流量比对ZnO薄膜的微结构、表面形貌及其光致发光特性的影响。X射线衍射仪和原子力显微镜结果显示,当O2/Ar流量比为3∶4时,所得薄膜结晶度最佳,表面粗糙度为0.725 nm;荧光光谱显示,ZnO薄膜在波长407 nm附近出现紫光发光峰,该发光峰源于氧空位浅施主能级到价带顶的电子跃迁,发射强度随O2/Ar流量比的增加先减小后增加。     

Effect of buffer layer thickness on the growth properties of hydrothermally grown ZnO nanorods

We investigated the effect of ZnO buffer layer thickness on the growth of hydrothermally grown ZnO nanorods. A series of ZnO buffer layers with different thicknesses was deposited on a p-Si (111) substrate using a co-sputtering system. After annealing the ZnO buffer layer, ZnO nanorods grown were grown hydrothermally at 95 degrees C. Unlike ZnO nanorods grown on as-deposited ZnO buffer layer, the diameter and length of ZnO nanorods grown on annealed ZnO buffer layers can be controlled. The structural and optical properties of ZnO nanorods grown on annealed ZnO buffer layers were analyzed by field-emission scanning electron microscopy, X-ray diffraction, and photoluminescence. The influence of ZnO buffer layer thickness on ZnO nanorods growth is discussed.     

Study on ZnO thin films deposited on sol-gel grown ZnO buffer by RF magnetron sputtering

ZnO thin films with preferential C-orientation and dense microstructure have been prepared using RF magnetron sputtering method by the insertion of a sol-gel grown ZnO buffer layer. The XRD results show that the C-orientation of the film deposited on ZnO buffer is obviously better than that deposited directly on lime-glass substrate. With an increase of the RF power from 100 to 380 W, C-orientation of the films with ZnO buffer improves and the grain size increases. When the RF power equals 550 W, the orientation of the film changes to (1 0 0) and the grain size decreases. The crystalline and microstructure quality of the films can be improved after annealing, however, the grain size is not much dependent on the annealing temperature in the range of 560-610 °C.     

Deposition of Al-doped ZnO films on polyethylene naphthalate substrate with radio frequency magnetron sputtering

100 nm Al-doped ZnO (AZO) thin films were deposited on polyethylene naphthalate (PEN) substrates with radio frequency magnetron sputtering using 2 wt.% Al-doped ZnO target at various deposition conditions including sputtering power, target to substrate distance, working pressure and substrate temperature. When the sputtering power, target to substrate distance and working pressure were decreased, the resistivity was decreased due to the improvement of crystallinity with larger grain size. As the substrate temperature was increased from 25 to 120 °C, AZO films showed lower electrical resistivity and better optical transmittance due to the significant improvement of the crystallinity. 2 wt.% Al-doped ZnO films deposited on glass and PEN substrates at sputtering power of 25 W, target to substrate distance of 6.8 cm, working pressure of 0.4 Pa and substrate temperature of 120 °C showed the lowest resistivity (5.12 × 10^− 3 Ω cm on PEN substrate, 3.85 × 10^− 3 Ω cm on glass substrate) and high average transmittance (> 90% in both substrates). AZO films deposited on PEN substrate showed similar electrical and optical properties like AZO films deposited on glass substrates.     

射频磁控溅射沉积高质量ZnO薄膜的工艺研究

在室温下利用射频磁控溅射法在硅(100)基片上制备ZnO薄膜,利用X射线衍射(XRD)和扫描电子显微镜(SEM)对其结晶性能进行分析。研究了制备条件对薄膜沉积速率的影响。分析了薄膜沉积速率对薄膜结晶状况的影响及源气体中的氧气和氩气的流量比对薄膜结晶状况的影响。研究结果表明,薄膜的生长速率强烈依赖于射频功率和工作气压,薄膜的结晶性能强烈依赖于薄膜的沉积速率和反应气体中氧气和氩气的流量比。制备高结晶质量的ZnO薄膜的最佳工艺参数为靶到衬底的距离为4cm,输入功率为250W,源气体中氩气和氧气的流量比n(Ar)∶n(O2)为5∶20,溅射工作气压为2Pa。在最佳工艺条件下所制备的薄膜表面平整致密,接近单晶,在可见光区的透射率高达90%。     

ZnO/SiC/Si异质结构的特性

用MOCVD方法在p型单晶Si（100）基片上外延SiC层,再用直流溅射在SiC层上生长ZnO薄膜,制备出ZnO／SiC／Si异质结构,用XRD和AFM分析了ZnO／SiC／Si和ZnO／Si异质结构中表层ZnO的结构和形貌的差别,研究了这种异质结构的特性．结果表明,在Si（100）基片上外延生长出的是高取向、高结晶质量的SiC（100）层．这个SiC层缓冲层使在Si基片上外延生长出了高质量ZnO薄膜,因为ZnO与SiC的晶格失配比ZnO与Si的晶格失配更低．     

Tin sulfide thin films and Mo/p-SnS/n-CdS/ZnO heterojunctions for photovoltaic applications

Tin sulfide (SnS) is one of the most promising materials for photovoltaics. Here we report on the preparation as well as chemical, structural and physical characterization of the Mo/p-SnS/n-CdS/ZnO heterojunctions. The SnS thin films were grown by hot wall deposition method on the Mo-coated glass substrates at 270-350 °C. The crystal structure and elemental composition were examined by X-ray diffraction and Auger electron spectroscopy methods. The CdS buffer layers were deposited onto the SnS films by chemical bath deposition. The ZnO window layers were deposited by a two step radio frequency magnetron sputtering, resulting in a ZnO bilayer structure: the first layer consists of undoped i-ZnO and the second of Al-doped n-ZnO. The best junctions have an open circuit voltage of 132 mV, a short circuit current density of 3.6 mA/cm², a fill-factor of 0.29 and efficiency up to 0.5%.     

Sputter deposition of ZnO thin films at high substrate temperatures

ZnO thin films have been deposited on GaN and ZnO substrates at substrate temperatures up to 750 °C by radio-frequency sputtering using ZnO ceramic targets in pure argon or in a mixture of argon and oxygen. By optimizing the sputter parameters, such as sputtering power, Ar/O₂ sputtering gas ratio and temperature of the substrates high quality films were obtained as judged from the X-ray rocking curve half width and luminescence line width. The crystallinity of the ZnO films increases with increasing substrate temperature. Yet there are distinct differences between films grown on GaN templates and on O- and Zn-polar ZnO substrates.