Growth,structure and optical characterization of Al‐doped ZnO nanoparticle thin films

Al‐doped ZnO nanoparticle thin films were prepared on glass substrate at the optimum temperature of (410±10) °C by spray pyrolysis technique using zinc nitrate as a precursor solution and aluminium chloride as a dopant. The dopant concentration (Al/Zn at%) was varied from 0 to 2 at%. Structural analysis of the films shows that all the films are of polycrystalline zinc oxide in nature, possessing hexagonal wurtzite structure. The films exhibit variation in peak intensities corresponding to (100), (002) and (101) reflection planes on Al‐doping. The crystallite size calculated by Scherrer formula has been found to be in the range of 35‐65 nm. The optical absorption study shows that the optical band gap in the Al‐doped films varies in the range of 3.11 – 3.22 eV. The width of localized states in the band gap estimated by the Urbach tail analysis has been found to be minimum in case of the 1 at% Al‐doped zinc oxide thin film. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structural and optical properties of Mg‐doped ZnO thin films prepared by a modified Pechini method

ZnO thin films with different Mg doping contents (0%, 3%, 5%, 8%, 10%, respectively) were prepared on quartz glass substrates by a modified Pechini method. XRD patterns reveal that all the thin films possess a polycrystalline hexagonal wurtzite structure. The peak position of (002) plane for Mg‐doped ZnO thin films shifts toward higher angle due to the Mg doping. The crystallite size calculated by Debey‐Scherrer formula is in the range of 32.95–48.92 nm. The SEM images show that Mg‐doped ZnO thin films are composed of dense nanoparticles, and the thickness of Mg‐doped ZnO thin films with Mg doped at 8% is around 140 nm. The transmittance spectra indicate that Mg doping can increase the optical bandgap of ZnO thin films. The band gap is tailored from 3.36 eV to 3.66 eV by changing Mg doping concentration between 3% and 10%. The photoluminescence spectra show that the ultraviolet emission peak of Mg‐doped ZnO thin films shifts toward lower wavelength as Mg doping content increases from 3% to 8%. The green emission peak of Mg‐doped ZnO thin films with Mg doping contents were 3%, 8%, and 10% is attributed to the oxygen vacancies or donor‐acceptor pair. These results prove that Mg‐doped ZnO thin films based on a modified Pechini method have the potential applications in the optoelectronic devices.     

Crystallographic,optical and magnetic properties of Co‐doped ZnO thin films synthesized by sol gel route

ZnO thin films with various Co doping levels (0%, 1%, 3%, 5%, 8%, respectively) have been synthesized by sol gel spin coating method on glass substrates. XRD and XPS studies of the films reveal that cobalt ions are successfully doped into ZnO crystal lattice without changing the hexagonal wurtzite structure. The morphologies are studied by SEM and AFM and show wrinkle network structures with uniform size distribution. With Co doping concentration increasing, the wrinkle network width decreases gradually. The transmittance spectra indicate that Co doping can effectively reduce the optical bandgap of ZnO thin films. Photoluminescence show that all samples have ultraviolet, violet and green emission. When Co doping concentration increases up to 5%, the intensity of violet emission is greatly increased and a strong deep blue emission centered at 439 nm appears. The ferromagnetism of all samples was observed at room temperature. The emission mechanisms and ferromagnetism origination are discussed in detail. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Microstructural and optoelectrical properties of transparent conducting ZnO:Al thin films for organic solar cells

The Al‐doped zinc oxide (ZnO:Al) thin films were grown on glass substrates by the magnetron sputtering technique. The films were characterized with X‐ray diffractometer, four‐point probe and optical transmission spectroscopy, respectively. The dependence of microstructural, electrical and optical properties on deposition temperature was investigated. The results show that all the films have hexagonal wurtzite structure with highly c‐axis orientation. And the microstrural and optoelectrical properties of the films are observed to be subjected to the deposition temperature. The ZnO:Al film prepared at the deposition temperature of 650 K possesses the best optoelectrical properties, with the lowest electrical resistivity (6.1×10⁻⁴ Ω·cm), the highest average visible transmittance (85.3%) and the maximum figure of merit (0.41 Ω⁻¹). The optical energy gap of the films was estimated from Tauc's law and observed to be an increasing tendency with the increment of the deposition temperature. Furthermore, the refractive index of the films was determined by the optical characterization methods and the dispersion behavior was studied by the single electronic oscillator model.     

片状ZnO薄膜的制备及其在DSSC中的光电性能研究

采用均匀沉淀法在导电玻璃基体上制备ZnO前驱体薄膜,然后热分解前驱体制备出ZnO薄膜用作染料敏化太阳能电池(DSSC)的光阳极.使用XRD和SEM对ZnO薄膜的结构和形貌进行表征.讨论了n(尿素)/n(Zn2+)、Zn2+浓度、均匀沉淀反应温度、薄膜焙烧温度等工艺因素对ZnO在DSSC中的光电性能影响.结果表明,均匀沉淀法制备ZnO薄膜为六方纤锌矿结构,ZnO薄膜以片状在基体上生长.优化的ZnO薄膜组装的DSSC在100mW/cm2下的短路电流为5.39 mA/cm2,开路电压为O.516 V.     

Grain boundary defects induced room temperature ferromagnetism in V doped ZnO thin films

Vanadium (V) doped ZnO thin films (Zn_1‐xV_x O, where x = 0, 0.05, 0.10) have been grown on sapphire substrates by RF magnetron sputtering to realize room temperature ferromagnetism (RTFM). The grown films have been subjected to X‐ray diffraction (XRD), resonant Raman scattering, photoluminescence (PL) and vibrating sample magnetometer (VSM) measurements to investigate their structural, optical and magnetic properties, respectively. The full width at half maximum of XRD and Raman scattering peaks increases with V ion concentration indicates that the V ions have been substituted on Zn²⁺ ions in the ZnO matrix. The increase in oxygen vacancies with V concentration is evidenced by PL measurements. Rutherford backscattering spectrometry analysis confirms the presence of the V ions in the films. The room temperature VSM measurements reveal the signature of ferromagnetism in V doped ZnO thin films. It has been observed that the grain boundary defects, i.e., oxygen vacancies play a crucial role in inducing RTFM in V doped ZnO films. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis of ZnO films in different solvents and their photocatalytic activities

ZnO thin films have been successfully synthesized via the chemical bath deposition (CBD) method without using any catalysts or templates. The effects of solvents (such as water, ethanol and n‐propanol) on structure and morphology of ZnO thin films have been studied. XRD analysis showed that all ZnO thin films with wurtzite crystal structure were obtained via various solvents. SEM images showed that ZnO thin films prepared in different solvents have different sizes and morphologies. TEM images showed that crystalline ZnO samples prepared in different solvents have different growth habits. Photoluminescence and photocatalysis properties have been investigated at room temperature. ZnO thin films prepared in water showed superior photocatalytic activity in the degradation of rhodamine B (RhB) compared to other samples.     

PET上沉积Al掺杂ZnO薄膜的光电特性研究

采用脉冲激光沉积技术(PLD),室温下在柔性衬底PET上制备了高度c轴择优取向的Al掺杂ZnO薄膜.XRD分析表明,不同Al掺杂浓度的样品均呈现单一的ZnO相.荧光光谱和透射光谱分析显示,低温低氧压下制备的Al掺杂ZnO薄膜在紫光区域有很强的荧光发射,在可见光区域具有较高的透射率;并且可以通过Al掺杂浓度调节薄膜紫色发光强度和薄膜带隙.薄膜的电阻率随着Al掺杂浓度的增加先降低后增加,在掺杂浓度为3;原子分数时达到最小值.     

Temperature dependence of growth orientation and surface morphology of Li‐doped ZnO thin films on SiO2/Si substrates

ZnO thin films doped with Li (ZnO:Li) were deposited onto SiO₂/Si (100) substrates by direct‐current sputtering technique in the temperature range from room temperature to 500 °C. The crystalline structure, surface morphology and composition, and optical reflectivity of the deposited films were studied by X‐ray diffraction (XRD), Scanning Electron Microscopy (SEM), X‐ray Photoelectron Spectroscopy (XPS) and optical reflection measurements. Rough surface p‐type ZnO thin film deposition was confirmed. The results indicated that the ZnO:Li films growed at low temperatures show c‐axis orientation, while a‐axis growth direction is preferable at high temperatures. Moreover, the optical reflectivity from the surface of the films matched very well with the obtained results. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

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.     

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).     

籽晶辅助化学水浴沉积法制备ZnO纳米棒阵列

采用籽晶辅助化学水浴沉积法,即先用磁控溅射法在硅片上制备c轴取向的ZnO薄膜,以此作为籽晶层,利用化学水浴沉积法制备ZnO纳米棒阵列.利用扫描电子显微镜(SEM)和X射线衍射(XRD),研究了ZnO薄膜籽晶层的沉积温度、水浴温度和前驱体溶液中Zn源的初始浓度等对ZnO纳米棒阵列生长的影响,由此得到了结晶性好且几乎垂直于衬底方向的ZnO纳米棒阵列的生长条件,为制备基于ZnO纳米棒阵列的器件提供了条件.     

氨水浓度对化学浴沉积的Zn(O,S)薄膜形貌、结构和性能的影响

采用化学浴法,以ZnSO4·7H2O和SC( NH2)2作为反应前驱物,C6H5O7 Na3·2H2O作为络合剂,NH3·H2O 作为辅助络合剂和缓冲剂制备Zn(O,S)薄膜.采用SEM、EDS、XPS、XRD和透射光谱分析方法,研究氨水浓度对化学浴法制备的Zn(O,S)薄膜形貌、成分、结构和光学性能的影响以及Zn(O,S)薄膜的形成机理.结果表明:Zn(O,S)薄膜是由ZnO和ZnS纳米颗粒混合组成的,ZnO具有纤锌矿结构,ZnS是以非晶相存在.随着反应溶液中氨水浓度的降低,薄膜中所包含的ZnO逐渐减少,ZnS逐渐增加,S/Zn原子比逐渐增加,透射率和光学带隙也逐渐增大.     

Effect of gallium incorporation on the physical properties of ZnO films grown by spray pyrolysis

Gallium-doped zinc oxide thin films were deposited by the spray pyrolysis technique onto Corning 7059 glass substrates at a temperature of 350°C using a precursor solution of zinc acetate in isopropyl alcohol. The films were prepared using different gallium concentrations keeping the other deposition parameters such as air and solution flow rates and solution concentration constant. The variations of the structural, electrical and optical properties with the doping concentration were investigated. X-ray diffraction data showed that the films were polycrystalline with the (0 0 2) preferred orientation. The texture coefficient and grain size were evaluated for different doping concentrations. The films with 5.0 at% gallium had a resistivity of 1.5×10⁻³ Ω cm and a transmittance of 85% with an energy band gap of 3.35 eV.     

Influence of substrate temperature on the properties of vacuum evaporated InSb films

Indium Antimonide (InSb) thin films were grown onto well cleaned glass substrates at different substrate temperatures (303, 373 and 473 K) by vacuum evaporation. The elemental composition of the deposited InSb film was found to be 52.9% (In) and 47.1% (Sb). X‐ray diffraction studies confirm the polycrystallinity of the films and the films show preferential orientation along the (111) plane. The particle size (D), dislocation density (δ) and strain (ε) were evaluated. The particle size increases with the increase of substrate temperature, which was found to be in the range from 22.36 to 32.59 nm. In Laser Raman study, the presence of longitudinal mode (LO) confirms that the deposited films were having the crystalline nature. Raman peak located at 191.26 cm^–1 shift towards the lower frequencies and narrows with increase in deposition temperature. This indicates that the crystallinity is improved in the films deposited at higher substrate temperatures. Hall measurements indicate that the films were p‐type, having carrier concentration ≅10¹⁶ cm^–3 and mobility (4–7.7) ×10³ cm²/Vs. It is observed that the carrier concentration (N) decreases and the Hall mobility (μ) increases with the increase of substrate temperature. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Studies on optical properties of polycrystalline SnO2:Sb thin films prepared using SnCl2 precursor

Optical properties of spray deposited antimony (Sb) doped tin oxide (SnO₂) thin films, prepared from SnCl₂ precursor, have been studied as a function of antimony doping concentration. The doping concentration was varied from 0‐4 wt.% of Sb. All the films were deposited on microscope glass slides at the optimized substrate temperature of 400 °C. The films are polycrystalline in nature with tetragonal crystal structure. The doped films are degenerate and n‐type conducting. The sheet resistance of tin oxide films was found to decrease from 38.22 Ω/□ for undoped films to 2.17 Ω/□ for antimony doped films. The lowest sheet resistance was achieved for 2 wt.% of Sb doping. To the best of our knowledge, this sheet resistance value is the lowest reported so far, for Sb doped films prepared from SnCl₂ precursor. The transmittance and reflectance spectra for the as‐deposited films were recorded in the wavelength range of 300 to 2500 nm. The transmittance of the films was observed to increase from 42 % to 55 % (at 800 nm) on initial addition of Sb and then it is decreased for higher level of antimony doping. This paper investigates the variation of optical and electrical properties of the as‐deposited films with Sb doping. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

基底温度对ZnO/Cu/ZnO透明导电膜性能的影响

采用射频磁控溅射ZnO陶瓷靶、直流磁控溅射Cu靶的方法在不同基底温度下制备了ZnO/Cu/ZnO多层膜.用X射线衍射仪、原子力显微镜、紫外可见分光光度计和四探针测试仪对样品的性能进行了表征.结果表明,随着基底温度的升高,ZnO层c轴择优取向明显,结晶程度变好,Cu层的结晶性先变好后逐渐变差;多层膜表面均方根粗糙度随基底温度的升高而增加;光学透过率随基底温度的升高逐渐增大,基底温度为300 ℃时最大透过率接近90;;面电阻随基底温度的升高逐渐增加,最小面电阻为12.4 Ω/□.     

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)     

Nanocrystalline transparent SnO2‐ZnO films fabricated at lower substrate temperature using a low‐cost and simplified spray technique

Nanocrystalline and transparent conducting SnO₂‐ ZnO films were fabricated by employing an inexpensive, simplified spray technique using a perfume atomizer at relatively low substrate temperature (360±5 °C) compared with conventional spray method. The structural studies reveal that the SnO₂‐ZnO films are polycrystalline in nature with preferential orientation along the (101) plane. The dislocation density is very low (1.48×10¹⁵lines/m²), indicating the good crystallinity of the films. The crystallite size of the films was found to be in the range of 26–34 nm. The optical transmittance in the visible range and the optical band gap are 85% and 3.6 eV respectively. The sheet resistance increases from 8.74 kΩ/□ to 32.4 kΩ/□ as the zinc concentration increases from 0 to 40 at.%. The films were found to have desirable figure of merit (1.63×10^–2 (Ω/□)^–1), low temperature coefficient of resistance (–1.191/K) and good thermal stability. This simplified spray technique may be considered as a promising alternative to conventional spray for the massive production of economic SnO₂ ‐ ZnO films for solar cells, sensors and opto‐electronic applications. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

热处理工艺对室温制备ZnO:Al薄膜结构与光电性能的影响

采用室温溅射加后续退火工艺制备了ZnO∶ Al透明导电薄膜.研究了热处理工艺对薄膜微观结构和光电性能的影响.研究表明:退火有助于减小Al~(3+)对Zn~(2+)的取代造成的晶格畸变,消除应力,促进晶粒长大,有效提高电子浓度和迁移率,降低电阻率;当溅射功率为80 W、退火温度为320 ℃时,薄膜的电阻率可低至8.6×10~(-4) Ω·cm;退火气氛对薄膜的导电性能有较大影响,真空退火可使吸附氧脱附,大大降低薄膜的方块电阻.而退火温度和退火气氛均对ZnO∶ Al薄膜的透光率没有明显影响,薄膜的透光率在86;以上.