蓝宝石衬底上磁控溅射法室温制备外延ZnO薄膜

在室温条件下,采用磁控溅射方法在蓝宝石(0001)衬底上制备了外延的ZnO薄膜.采用原子力显微镜(AFM)、X射线衍射仪(XRD)、可见-紫外分光光度计系统研究了ZnO薄膜微观结构和光学特性.AFM测量结果表明ZnO薄膜具有较为均匀的ZnO晶粒,表面平整,具有较小的均方根粗糙度(0.9 nm);X射线衍射结果表明制备的ZnO薄膜为具有六角纤锌矿结构的外延薄膜;光学透射谱显示样品在可见光范围内具有较高的透过性,并在370 nm附近出现一个较陡的吸收边,表明在室温下制备出了具有较高质量的ZnO薄膜.     

Specific features of the growth of A II B VI films on (0001)Al2O3 substrates

The structure and orientation of CdTe and ZnO films on sapphire have been investigated for different techniques of pregrowth substrate treatment. Polycrystalline CdTe films are found to grow of substrates unannealed or annealed in vacuum at a residual pressure P < 0.13 Pa. Epitaxial CdTe films with the sphalerite cubic structure, oriented parallel to the substrate by the (111) plane, grow on substrates annealed in air at a temperature of 1000°C or more and having a system of smooth terraces and steps on the surface. For ZnO films with a wurtzite hexagonal structure obtained by magnetron sputtering, a similar correlation between the structural quality and the regime of treatment of sapphire substrates is observed. It is shown that thermal annealing of (0001) sapphire plates in air is the optimal way of substrate preparation for growing epitaxial ZnO films with the base orientation. The obtained epitaxial CdTe films contain a certain amount of structural defects (mosaicity and twins), while the epitaixal ZnO films treated in the same way are close to perfect.     

Influence of ensembles of gold nanoparticles on the growth of ZnO on the sapphire (0001) surface

Gold is deposited on sapphire (0001) substrates by vacuum sputtering to form an ensemble of nanoparticles on the surface. Then the substrates are transferred to a magnetron sputtering chamber to be heated to 650°C and coated by a ZnO layer. The resulting layers are investigated by scanning electron microscopy, atomic force microscopy, electron diffraction, and photoluminescence. It is established that the Au sublayer ensures a higher quality of the ZnO structure and enhances photoluminescence. The differences in the morphology of ZnO structures is explained by the Au aggregation during substrate heating before ZnO deposition.     

不同衬底温度下ZnO外延薄膜的结构及光学特性分析

采用螺旋波等离子体辅助射频溅射沉积技术在Al2O3(0001)衬底上沉积ZnO外延薄膜,通过对其结构及光学性质的分析,探讨了衬底温度对薄膜生长特性的影响.实验结果表明,由于等离子体对反应气体的活化及载能粒子对表面反应的辅助作用,采用该等离子体辅助溅射技术能够在较低的衬底温度下实现较高质量的ZnO薄膜外延生长,然而,较高的衬底温度所引起的表面反应不利于薄膜中的氧空位及锌填隙等缺陷的减少,这将限制薄膜的外延质量及光学特性的进一步提高.     

Deep ultraviolet emission of ZnO films prepared by RF magnetron sputtering at changing substrate temperature

ZnO films with deep ultraviolet emission on (0 0 0 6) sapphire substrates were prepared by RF magnetron sputtering at periodically changing substrate temperature. It is found that the as-prepared ZnO films consist of the obvious multilayered structures from the SEM images of their cross-sections. Room temperature photoluminescence of ZnO films with multilayered structure shows two emissions centered at 332 and 388 nm with 260 nm excited wavelength. The strong deep ultraviolet emission at 332 nm is due to the O 2p dangling-bond state in the multilayered structure of ZnO films. Raman scattering spectrum of sample shows that such structured ZnO film possesses strong compressive stress.     

射频磁控溅射生长ZnO薄膜及性能研究

采用射频磁控溅射技术在玻璃衬底生长ZnO及ZnO∶ Al薄膜,通过改变氩氧比、衬底温度和溅射功率获得样品.用X射线衍射仪、紫外-可见分光光度计、扫描电子显微镜进行表征.结果发现:室温下40W的溅射功率1h的溅射时间,改变氩氧比获得样品.XRD图谱中无明显衍射峰出现;紫外可见光分光光度计测试结果显示400nm波长以下,透光率在90;以上.说明薄膜生长呈无定形.衬底温度高于200℃样品,XRD有明显(002)衍射峰出现,在400～ 800 nm波长范围,透光率在88;以上,衬底温度300℃时,XRD衍射峰半高宽最小,晶粒尺寸大.TEM显示:衬底300℃晶粒尺寸最大,晶体发育好.在200℃掺铝ZnO薄膜,(002)峰不明显,有(101)峰出现.     

Structural and optoelectrical properties of Ga‐doped ZnO semiconductor thin films grown by magnetron sputtering

Transparent conductive gallium‐doped zinc oxide (Ga‐doped ZnO) films were prepared on glass substrate by magnetron sputtering. The influence of substrate temperature on structural, optoelectrical and surface properties of the films were investigated by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), spectrophotometer, four‐point probe and goniometry, respectively. Experimental results show that all the films are found to be oriented along the c‐axis. The grain size and optical transmittance of the films increase with increasing substrate temperature. The average transmittance in the visible wavelength range is above 83% for all the samples. It is observed that the optoelectrical property is correlated with the film structure. The Ga‐doped ZnO film grown at the substrate temperature of 400 °C has the highest figure of merit of 1.25 × 10⁻² Ω⁻¹, the lowest resistivity of 1.56 × 10⁻³ Ω·cm and the highest surface energy of 32.3 mJ/m².     

High rate epitaxial growth of ZnO films on sapphire by planar magnetron rf sputtering system

Single crystal films of (11$\text{2}$0)ZnO are obtained on (01$\text{1}$2) sapphire at a deposition rate of 2 μm/h at a substrate temperature of 210–260°C by using a planar magnetron type high rate and low substrate temperature rf sputtering system. The surface of the film is so smooth that it can be used as an optical waveguide without post-deposition treatment. However, the films so far obtained have considerably higher optical waveguide loss than that of chemically vapor deposited films on the same face of sapphire.     

Influence of substrate and film thickness on structural,optical and electrical properties of ZnO thin films

Transparent Zinc Oxide (ZnO) thin films have been grown on Si (100) and Sapphire (0001) substrates by RF magnetron sputtering for different growth time intervals (10, 30 and 60 min) to study the substrate and thickness effects. All the films have been grown at a substrate temperature of 450 °C. It has been found that the average growth rate on Si (100) substrate (8.6 nm/min) is higher than that on Sapphire (0001) substrate (2.6 nm/min) in an identical growth condition which clearly shows the virtual role of substrates. The lower growth rate on Sapphire (0001) suggests that the increasingly ordered and uniform growth due to less lattice mismatch. The grown films have been characterized by X‐ray diffraction (XRD), Reflectance, Photoluminescence (PL) and Hall measurements. The XRD result (FWHM) reveals that for lower growth time, the films grown on Si (100) is better than on Sapphire (0001). Conversely, for higher growth time, the films grown on Sapphire (0001) is better than on Si (100). The variation of strain behavior due to thickness on both substrates has been justified by UV‐Vis reflectance, photoluminescence and Hall effect measurements. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

衬底温度对直流反应磁控溅射法制备的N掺杂p型ZnO薄膜性能的影响

利用直流反应磁控溅射法(纯金属锌作为靶材,Ar-N2-O2混合气体作为溅射气体)在石英玻璃衬底上制备了N掺杂p型ZnO薄膜.通过XRD、Hall和紫外可见透射谱分别研究了衬底温度对ZnO薄膜结构性能、电学性能和光学性能的影响.XRD结果显示所有制备的薄膜都具有垂直于衬底的c轴择优取向,并且随着衬底温度的增加,薄膜的晶体质量得到了提高.Hall测试表明衬底温度对p型ZnO薄膜的电阻率具有较大影响,400℃下生长的p型ZnO薄膜由于具有较高的迁移率(1.32 cm2/Vs)和载流子浓度(5.58×1017cm-3),因此表现出了最小的电阻率(8.44Ω·cm).     

Microstructural characteristics and crystallographic evolutions of Ga-doped ZnO films grown on sapphire substrates at high temperatures by RF magnetron sputtering

The microstructural characteristics and crystallographic evolutions of Ga-doped ZnO (GZO) films grown at high temperatures were examined by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). The GZO films with various film thicknesses were grown on (0 0 0 1) Al₂O₃ substrates at 750 °C by RF magnetron sputtering using a 2 wt% Ga-doped ZnO single target. The (0 0 0 2) ZnO peaks in the XRD patterns shifted to a higher angle with increasing film thickness and an additional (1 0 1¯ 1) ZnO peak was observed in the final stage of film growth. HRTEM showed the epitaxial growth of GZO films in the initial growth stage and the formation of surface protrusions in the intermediate stage due to elastic relaxation. The surface protrusions consisted of {1 0 1¯ 1}, {1 0 1¯ 3}, and {0 0 0 2} planes. After the surface protrusions had formed, a GZO film with many c-axis tilted grains formed due to plastic relaxation, where the tilted grain boundaries had an angle of 62° to the substrate. The formation of the protrusions and c-axis tilted grains was closely related to the strain status of the film induced by Ga incorporation, high-temperature growth and a high film thickness.     

Analysis of the growth of RF sputtered ZnO thin films using the optical reflective second harmonic generation

Reflective second harmonic generation (RSHG) is used to analyze the growth condition of poly crystal zinc oxide (ZnO) film with a c-axis orientation, grown on the Si substrate by RF magnetron sputtering technique. It elucidates physical phenomena exhibited by growing ZnO thin films. Connecting with analytical results of the characteristic parameters derived from the X-ray patterns and SEM images, the relationship between the RSHG intensity and the substrate temperature reveals that the effect of the grain boundaries is the domination of the RSHG mechanism. The inclined structures of ZnO films on the Si substrate are explained with reference to these RSHG patterns.     

Strong biaxial texture and polymorph nature in TiO2 thin film formed by ex-situ annealing on c-plane Al2O3 surface

Many applications based on TiO₂ thin films are strongly influenced by the film crystalline quality, microstructure and surface morphology. We have utilized x-ray scattering methods for crystal structure study of TiO₂ films, grown by DC reactive magnetron sputtering without heating. We have observed the formation of ordered phases after post-deposition ex-situ annealing in air at 600 °C. The distinct biaxial texture with respect to the c-plane (0001) Al₂O₃ substrate surface, which developed during heating, shows remarkable patterns in pole figures. We have identified epitaxial relationships of anatase A(001)[110]6sub(001)[11?00] and rutile R(100)[001]6sub(0001)[100] within single TiO₂ layer. In addition, within the same sample, we have observed the anatase in (112) orientation with two in-plane relationship options A(112)[11?0]6sub(0001)[21?1?0] and A(112)[11?0]6sub(0001)[11?00].     

Sputter power and sputter pressure influenced structural and optical behaviour of RF sputtered nanocrystalline ZnO films

Zinc oxide thin films were deposited on p‐type (100) silicon and Corning glass substrate by using RF magnetron sputtering at different sputter powers range 100–200 W and sputter pressures range 2–8 Pa. The deposited films were characterized by X‐ray diffraction, atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscope and UV‐Vis‐NIR spectrophotometer. The films formed at sputter power of 100 W consists of weak (100) reflection and then sputter power increased to 150 W additional (110) reflection was present with enhancement in the intensity of (100) peak. Further increase of sputtering power to 200 W the intensity of (100) phase decreased with the presence of additional peaks of (002) and (101) of ZnO. The FTIR analysis confirms the Zn‐O absorption band was located at 414 cm^‐1. The optical band gap of zinc oxide films decreased from 3.28 to 3.07 eV with increase of sputter power from 100 to 200 W. The maximum crystallite size of 21 nm, the root mean square roughness of 7.2 nm was found at films formed at working pressure of 5 Pa. The optical transmittance of the films increased from 88 to 96% and then decreased to 84% with increase of sputter pressure from 2 to 8 Pa.     

衬底温度对磁控溅射法制备掺Ta氧化锌薄膜性能的影响

采用射频磁控溅射法,在不同的衬底温度下制备了钽(Ta)掺杂的氧化锌(ZnO)薄膜,采用X射线能谱(EDS)、X射线衍射(XRD)、扫描电镜(SEM)、紫外-可见分光光度计和光致发光(PL)光谱研究了衬底温度对制备的Ta掺杂ZnO薄膜的组分、微观结构、形貌和光学特性的影响.EDS的检测结果表明,Ta元素成功掺入到了ZnO薄膜;XRD图谱表明,掺入的Ta杂质是替代式杂质,没有破坏ZnO的六方晶格结构,随着衬底温度的升高,(002)衍射峰的强度先增大后降低,在400℃时达到最大;SEM测试表明当衬底温度较高时(400℃和500℃),Ta掺杂ZnO薄膜的晶粒明显变大;紫外-可见透过光谱显示,在可见光范围,Ta掺杂ZnO薄膜的平均透光率均高于80;,衬底不加热时制备的Ta掺杂ZnO的透光率最高;制备的Ta掺杂ZnO薄膜的禁带宽度范围为3.34~3.37eV,衬底温度为500℃时制备的Ta掺杂ZnO薄膜的禁带宽度最小,为3.34eV.PL光谱表明衬底温度为500℃时制备的Ta掺杂ZnO薄膜中缺陷较多,这也是造成薄膜禁带宽度变小的原因.     

两步法溅射中缓冲层厚度对Ge薄膜质量的影响

采用低温缓冲层技术制备Ge薄膜,利用AFM和Raman光谱研究缓冲层厚度对低温Ge缓冲层残余应变弛豫的影响.实验结果显示:随着缓冲层厚度的增加,残余应变弛豫度增大.在30 nm厚的低温Ge缓冲层上生长800nm厚的Ge外延层.Ge薄膜具有良好的结晶性,表面粗糙度RMS为2.06 nm.     

直流反应磁控溅射法制备ZnO: Zr透明导电薄膜

以Zn∶ Zr为靶材,利用直流反应磁控溅射法制备了ZnO∶ Zr透明导电薄薄膜.研究了沉积压强对ZnO∶ Zr薄膜形貌、结构、光学及电学性能的影响.实验结果表明所制备的ZnO∶ Zr为六方纤锌矿结构的多晶薄膜,具有垂直于衬底方向的c轴择优取向.沉积压强对ZnO∶ Zr薄膜的晶化程度、形貌、生长速率和电阻率影响很大,而对其光学性能如透光率、光学带隙及折射率影响不大.当沉积压强为2Pa时,ZnO∶ Zr薄膜的电阻率达到最小值2.0×10-3Ω ·cm,其可见光平均透过率和平均折射率分别为83.2％和1.97.     

Influence of substrate temperature and oxygen/argon flow ratio on the electrical and optical properties of Ga‐doped ZnO thin films prepared by rf magnetron sputtering

Effects of substrate temperature and atmosphere on the electrical and optical properties of Ga‐doped ZnO thin films deposited by rf magnetron sputtering were investigated. The electrical resistivity of Ga‐doped ZnO (GZO) films decreases as the substrate temperature increases from room temperature to 300°C. A minimum resistivity of 3.3 × 10^–4 Ω cm is obtained at 300°C and then the resistivity increases with a further increase in the substrate temperature to 400°C. This change in resistivity with the substrate temperature is related to the crystallinity of the GZO film. The resistivity nearly does not change with the O₂/Ar flow ratio, R for R < 0.25 but increases rapidly with R for R > 0.25. This change in resistivity with R is also related to crystallinity. The crystallinity is enhanced as R increases, but if the oxygen partial pressure is higher than a certain level (R = 0.25 ± 0.10) gallium oxides precipitate at grain boundaries, which decrease both carrier concentration and mobility. Optical transmittance increases as R increases for R < 0.75. This change in transmittance with R is related to changes in oxygen vacancy concentration and surface roughness with R. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

溅射温度对ITO/Ag/ITO多层复合薄膜的结构和光电性能的影响

本文采用直流磁控溅射分层溅射制备了氧化铟锡(ITO)/银(Ag)/ITO多层复合薄膜。系统研究了溅射温度对ITO/Ag/ITO多层复合薄膜的结构和光电性能影响。采用ITO(m(In₂O₃)∶m(SnO₂)=9∶1;直径60 mm)靶材和Ag(纯度99.999%;直径60 mm)靶材分层溅射,使ITO薄膜和Ag薄膜依次沉积在钠-钙玻璃基片上。结果表明,溅射温度对该薄膜的形貌和结构具有显著的影响。在中间Ag薄膜和顶层ITO薄膜的溅射温度均为120 ℃时,薄膜表面晶粒形貌由类球形转变为菱形,此时薄膜方阻为3.68 Ω/Sq,在488 nm处透射率为88.98%,且品质因数为0.03 Ω^-1,实现了低方阻高可见光透射率ITO/Ag/ITO多层复合薄膜的制备。     

Oxygen bombardment effects on average crystallite size of sputter-deposited ZnO films

Zinc oxide (ZnO) film was deposited on a glass substrate by rf magnetron sputtering with O₂/Ar as working gases. Structural properties of the films were characterized by XRD. Average crystallite size in the films was strongly dependent on both the gas flow ratio of O₂/Ar and rf-power at a constant deposition pressure. During the deposition, energetic species in the plasma were in situ monitored using optical emission spectroscopy. An inverse correlation was observed between the average crystallite size and the emission intensity ratio of I_O^∗/I_Ar. Bombardment of atomic oxygen to the growing surface played an important role in determining the average crystallite size in the films. The average crystallite size could be controlled by the emission intensity ratio of I_O^∗/I_Ar.