Characteristics of ZnO:In thin films prepared by RF magnetron sputtering

In-doped ZnO (ZnO:In) transparent conductive thin films were deposited on glass substrates by RF magnetron sputtering. The effect of substrate temperature on the structural, electrical and optical properties of the ZnO:In thin films was investigated. It was found that higher temperature improves the crystallinity of the films and promotes In substitution easily. ZnO:In thin films with the best crystal quality were fabricated at 300 °C, which exhibit a larger grain size of 29 nm and small tensile strain of 0.9%. The transmittance of all the films was revealed to be over 85% in the visible range independence of the substrate temperatures and the lowest resistivity of ZnO:In thin films is 2.4×10⁻³ Ω cm.     

Controlled visible photoluminescence of ZnO thin films prepared by RF magnetron sputtering

ZnO thin films were prepared by RF magnetron sputtering. The photoluminescence dependence on the growth ambient and annealing temperatures and the atmosphere has been studied. Visible photoluminescence with blue, green, orange, and red emission bands has been demonstrated by controlling the preparation conditions. Complete suppression of the visible emission bands was also realized by annealing the O₂-ambient-grown samples in N₂ atmosphere at higher temperatures, which indicated the preparation of ZnO thin films with high optical quality.     

Seebeck and magnetoresistive effects of Ga-doped ZnO thin films prepared by RF magnetron sputtering

In this paper, Ga-doped ZnO (GZO) films were deposited on glass substrates at different substrate temperatures by RF magnetron sputtering. The effect of substrate temperature on the structural, surface morphological properties, Seebeck and magnetoresistive effects of GZO films was investigated. It is found that the GZO films are polycrystalline and preferentially in the [0 0 2] orientation, and the film deposited at 300 °C has an optimal crystal quality. Seebeck and magnetoresistive effects are apparently observed in GZO films. The thermoelectromotive forces are negative. Decreasing substrate temperature and annealing in N₂ flow can decrease carrier concentration. The absolute value of the Seebeck coefficient increases with decreasing carrier concentration. The maximal absolute value of Seebeck coefficient is 101.54 μV/K for the annealed samples deposited at the substrate temperature of 200 °C. The transverse magnetoresistance of GZO films is related to both the magnetic field intensity and the Hall mobility. The magnetoresistance increases almost linearly with magnetic field intensity, and the films deposited at higher substrate temperature have a stronger magnetoresistance under the same magnetic field, due to the larger Hall mobility.     

射频磁控溅射法制备ZnS多晶薄膜及其性质

实验采用射频磁控溅射法在玻璃衬底上沉积了ZnS多晶薄膜,研究了沉积气压、退火温度和衬底温度对ZnS薄膜质量的影响.利用X射线衍射(XRD)分析了薄膜的微结构,并计算了内应力值.通过紫外-可见光分光光度计测量了薄膜的透过谱,计算了Urbach能量和禁带宽度.利用扫描电子显微镜(SEM)观察了薄膜的表面形貌.结果表明: 衬底温度为室温时沉积的ZnS薄膜具有较大的压应力,并且内应力值随着工作气压增大而增大,在300 ℃下进行退火处理后内应力松弛,衬底温度为350 ℃时制备的ZnS薄膜内应力小,透过率高,经300 ℃退火处理后结晶质量有所提高. 关键词： ZnS薄膜 射频磁控溅射 内应力     

射频磁控溅射制备氧化钒薄膜的研究

氧化钒（VOx）薄膜是一种广泛应用于红外热成像探测的薄膜材料,研究VOx薄膜的制备工艺、获取高电阻温度系数（TCR）的VOx薄膜具有重要意义。以高纯金属钒作靶材,采用射频磁控溅射的方法在室温下制备了VOx薄膜。主要研究了氩氧流量比以及功率等工艺参数对薄膜TCR的影响,获得了较好的工艺参数。采用万用表和X射线光电子能谱仪（XPS）分别测试了不同条件下射频磁控溅射法制备的VOx薄膜的电阻特性和薄膜成分,测试结果表明,采用所获得的较好工艺参数制备的VOx薄膜TCR值大于1.8%。     

Blue luminescence from Ce-doped ZnO thin films prepared by magnetron sputtering

The photoluminescence properties of undoped and Ce-doped ZnO thin films that were prepared by DC magnetron sputtering were investigated. It was found that the incorporation of Ce could intensively affect the structural, optical, and photoluminescence properties of the ZnO thin films. The undoped ZnO thin films showed a sharp UV luminescence, whereas the Ce-doped ZnO thin films showed a broad blue luminescence. The effects of excitation wavelength and annealing atmosphere on the photoluminescence properties of Ce-doped ZnO thin films were also studied. After post-annealing in air and oxygen atmospheres, the blue emissions of the prepared films were drastically suppressed. Our results indicate that the blue emissions of Ce-doped ZnO thin films are related to zinc interstitials and the intrinsic transition of Ce³⁺ ions.     

Effects of hydrogen flow on properties of hydrogen doped ZnO thin films prepared by RF magnetron sputtering

The hydrogen doped ZnO (ZnO:H) thin films were deposited on quartz glass substrates by radio frequency magnetron sputtering. The doping characteristics of ZnO:H thin films with varied hydrogen flow ratio were investigated. At low hydrogen flow ratio (H₂/(H₂+Ar)≤0.02), the ZnO:H thin films exhibited dominant (002) peaks from X-ray diffraction and the lattice constants became smaller. The particles were mainly a columnar structure. The particles’ size became smaller, and the island-like structure appeared on the thin films surface. In addition, the low resistivity properties of ZnO:H thin films was ascribed to the increase of the carriers concentration and carriers mobility; When the hydrogen flow ratio was more than 0.02 (M≥0.02), two absorption bands at 1400–1800 cm^?1 and 3200–3900 cm^?1 were observed from the FT-IR spectra, which indicated that the ZnO:H thin films had typical Zn–H bonding, O–H bonding (hydroxyl), and Zn–H–O bonding (like-hydroxyl). The scanning electron microscope (SEM) results show that a large number of hydroxyl agglomeration formed an island-like structure on the thin films surface. The absorption peak at about 575 cm^?1 in the Raman spectra indicated that oxygen vacancies (V_O) defects were produced in the process of high hydrogen doping. In this condition, the low resistivity properties of ZnO:H thin films were mainly due to the increasing electron concentration resulted from V_O. Meanwhile, the Raman absorption peaks at approximately 98 cm^?1 and 436 cm^?1 became weaker, and the (002) XRD diffraction peak quenched and the lattice constants increased, which shows that the ZnO:H thin films no longer presented a typical ZnO hexagonal wurtzite structure. With the increasing of hydrogen flow ratio, the optical transmittance of ZnO:H thin films in the ultraviolet band show a clear Burstein–Moss shift effect, which further explained that electron concentration was increased due to the increasing V_O with high hydrogen doping concentration. Moreover, the optical reflectance of the thin films decreased, indicating the higher roughness of the films surface. It was noteworthy that etching effect of H plasma was obvious in the process of heavy hydrogen doping.     

Characterization of ZnO thin films grown on various substrates by RF magnetron sputtering

In this study we investigated properties of ZnO thin films deposited on both oxygen-containing substrates and a substrate without oxygen content at various O₂/Ar reactant gas ratios. Deposition of ZnO on indium-tin oxide (ITO) resulted in the best crystallinity, whereas the least degree of crystallization was observed from ZnO deposited on glass. All the films were found to have compressive stress, which was relieved by annealing in O₂ environment. ZnO films deposited on glass revealed p-type conductivity when prepared at O₂/Ar ratio of 0.25 whereas those on SiN_x yielded p-type conductivity when prepared at O₂/Ar ratio of 4. In addition, shallower oxygen interstitial seemed to be found from films with better crystallinity. The largest shift in binding energy of Zn_2p3/2 was observed from ZnO prepared on glass at O₂/Ar ratio of 0.25, whereas that of O_1s was obtained from ZnO deposited on SiN_x at O₂/Ar ratio of 4. A model was proposed in terms of O₂ diffusion and hydrogen desorption in order to account for the observed property variations depending on substrates and O₂/Ar ratios.     

Structure and electrical transport properties of bismuth thin films prepared by RF magnetron sputtering

Bismuth thin films were prepared on glass substrates with RF magnetron sputtering and the effects of deposition temperature on surface morphology and their electrical transport properties were investigated. Grain growth of bismuth and the coalescence of grains were observed above 393 K with field emission secondary electron microscopy. Continuous thin films could not be obtained above 448 K because of the segregation of grains. Hall effect measurements showed that substrate heating yields the decrease of carrier density and the increase of mobility in exponential ways until 403 K. Resistivity of sputter deposited bismuth films has its minimum (about 0.7 × 10⁻³ Ω cm) in range of 403-433 K. Annealing of bismuth films deposited at room temperature was carried out in a radiation furnace with flowing hydrogen gas. The change of resistivity was not significant due to the cancellation of the decrease of carrier density and the increase of mobility. However, the abrupt change of electrical properties of film annealed above 523 K was observed, which is caused by the oxidation of bismuth layer.     

Photocatalytic degradation of methyl orange by nano-TiO_2 thin films prepared by RF magnetron sputtering

Nano-TiO2 thin films are deposited by radio frequency （RF） magnetron sputtering using TiO2 ceramic target and characterized by X-ray diffractometer, atomic force microscope, and ultraviolet-visible spectrophotometer. The photocatalytic activity is evaluated by light-induced degradation of methyl orange solutions （5, 10, and 20 ppm） using a high pressure mercury lamp as the light source. The film is amorphous, and its energy gap is 3.02 eV. The photocatalytic degradation of methyl orange solution is the first-order reaction and the apparent reaction rate constants are 0.00369, 0.0024, and 0.00151 for the methyl orange solution concentrations of 5, 10, and 20 ppm, respectively.     

Fabrication of p-ZnO:ZrN thin films by RF magnetron sputtering

An attempt has been made to fabricate p-ZnO thin films from the ZrN mixed ZnO targets by RF magnetron sputtering. The targets of different ZrN concentrations (0, 1, 2, and 4?mol%) have been prepared by solid-state reaction route. The ZrN-codoped ZnO films grown on semi-insulating Si (100) substrates have been characterized by X-ray diffraction (XRD), photoluminescence (PL), Hall effect measurement, time-of-flight secondary ion mass spectrometer (ToF-SIMS), and atomic force microscopy (AFM). XRD studies reveal that all films are oriented along (002) plane. The Hall measurements showed p-conductivity for 1 and 2?mol% ZrN-codoped ZnO films. Further, it has been found that 1?mol% ZrN-codoped film has low resistivity (7.5?×?10^?2?Ω?cm) and considerable hole concentration (8.2?×?10¹⁸?cm^?3) by optimum incorporation of nitrogen due to best codoping. The red shift in near-band-edge emission observed from PL well acknowledged the p-conduction in 1 and 2?mol% ZrN-codoped ZnO film. The incorporation of N and Zr atoms in the ZnO matrix has been confirmed by ToF-SIMS analysis. The increase in peak to valley roughness (R _pv) with increase of doping concentration has been observed from AFM analysis. ZnO homojunction has also been fabricated with the best codoped p-ZnO film and it showed typical rectification behavior of a diode. The junction parameters have also been determined for the fabricated homojunction.     

Growth characteristics and properties of ZnO:Ga thin films prepared by pulsed DC magnetron sputtering

Transparent conductive ZnO:Ga thin films were deposited on Corning 1737 glass substrate by pulsed direct current (DC) magnetron sputtering. The effects of process parameters, namely pulse frequency and film thickness on the structural and optoelectronic properties of ZnO:Ga thin films are evaluated. It shows that highly c-axis (0 0 2) oriented polycrystalline films with good visible transparency and electrical conductivity were prepared at a pulsed frequency of 10 kHz. Increasing the film thickness also enlarged the grain size and carrier mobility which will subsequently lead to the decrease in resistivity. In summary, ZnO:Ga thin film with the lowest electrical resistivity of 2.01 × 10⁻⁴ Ω cm was obtained at a pulse frequency of 10 kHz with 500 nm in thickness. The surface RMS (root mean square) roughness of the film is 2.9 nm with visible transmittance around 86% and optical band gap of 3.83 eV.     

Influence of negative ion resputtering on Al-doped ZnO thin films prepared by mid-frequency magnetron sputtering

Al-doped ZnO (AZO) films were deposited on glass substrates by mid-frequency magnetron sputtering with a ceramic ZnO:Al₂O₃ (98 wt%:2 wt%) target. The origin of the high resistivity of the films at the substrate position facing the erosion area of the target was investigated. The results indicate a preferential resputtering of Zn atoms caused by the negative ions, which leads to an increase of the oxygen/metal ratio in the films. Then more Al oxides form and result in the decrease of Al_Zn (the main donor in the films) concentration in the films. Thus the free carrier concentration decreases badly. This is the main mechanism responsible for the high resistivity.     

Influence of deposition temperature on the crystallinity of Al-doped ZnO thin films at glass substrates prepared by RF magnetron sputtering method

Al-doped ZnO (AZO) transparent conducting films were successfully prepared on glass substrates by RF magnetron sputtering method under different substrate temperatures. The microstructural, electrical and optical properties of AZO films were investigated in a wide temperature range from room temperature up to 350 °C by X-ray Diffraction (XRD), Field-Emission Scanning Electron Microscopy (FESEM), High-Resolution Transmission Electron Microscopy (HRTEM), Hall measurement, and UV–visible meter. The nature of AZO films is polycrystalline thin films with hexagonal wurtzite structure and a preferred orientation along c-axis. The crystallinity and surface morphologies of the films are strongly dependent on the growth temperature, which in turn exerts a great effect on microstructural, electrical and optical properties of the AZO films. The atomic arrangement of AZO film having an wurtzite structure was indeed identified by the HRTEM as well as the Selected Area Electron Diffraction (SAED). The defect density of AZO film was investigated by HRTEM. The film deposited at 100 °C exhibited the relatively well crystallinity and the lowest resistivity of 3.6 × 10⁻⁴ Ω cm. The average transmission of AZO films in the visible range is all over 85%. More importantly, the low-resistance and high-transmittance AZO film was also prepared at a low temperature of 100 °C.     

用射频磁控溅射法制备金属/半导体颗粒膜

用射频磁控溅射法制备了金属/半导体Fex(In2O3)1-x颗粒膜,研究了该系列颗粒膜的微结构和磁性.实验结果表明:纳米尺度的Fe颗粒均匀地分散在非晶体态In2O3中.室温下样品具有超顺磁性,符合朗之万方程.     

Deposition and properties of B-N codoped p-type ZnO thin films by RF magnetron sputtering

B-N codoped p-type ZnO thin films have been realized by radio frequency (rf) magnetron sputtering using a mixture of argon and oxygen as sputtering gas. Types of conduction and electrical properties in codoped ZnO films were found to be dependent on oxygen partial pressure ratios in the sputtering gas mixture. When oxygen partial pressure ratio was 70%, the codoped ZnO film showed p-type conduction and had the best electrical properties. Additionally, the p-ZnO/n-Si heterojunction showed a clear p-n diode characteristic. XRD results indicate that the B-N codoped ZnO film prepared in 70% oxygen partial pressure ratio has high crystal quality with (0 0 2) preferential orientation. Meanwhile, the B-N codoped ZnO film has high optical quality and displays the stronger near band edge (NBE) emission in the temperature-dependent photoluminescence spectrum, the acceptor energy level was estimated to be located at 125 meV above the valence band.     

Magnetic properties of Er-doped ZnO films prepared by reactive magnetron sputtering

All Zn_1−x Er _x O (x=0.04, 0.05, and 0.17) films deposited on glass substrates by radio-frequency reactive magnetron sputtering exhibit the mixture of ferromagnetic and paramagnetic phases at room temperature. The estimated magnetic moment per Er ion decreases with the increase of Er concentration. The temperature dependence of the magnetization indicates that there is no intermetallic ErZn buried in the films. The ferromagnetism is attributed to the Er ions substitution for Zn²⁺ in ZnO lattices, and it can be interpreted by the bound-magnetic-polaron model.     

射频溅射制备的BST薄膜介电击穿研究

采用射频溅射制备BST薄膜，研究了薄膜的介电击穿特性.实验表明，在电压增大到传统击穿电压(电流密度出现瞬时增大时的电压)之前，薄膜性能已被破坏，发现在传统击穿状态之前存在另一个新状态——初始击穿状态.通过测试各状态的J-V(电流密度-电压)、J-T(电流密度-温度)特性分析其导电机理，建立了薄膜结构、漏电性能随电场强度增大而变化的模型.最后提出了确定实际意义上击穿电压的方法. 关键词： BST薄膜 介电击穿 漏电流