Fabrication of columnar structured lanthanum zirconate films by laser CVD

Columnar lanthanum zirconate (LZ) films were deposited by laser chemical vapor deposition (LCVD). The effects of deposition conditions, preheat temperature and laser power, on crystal structure, morphology, and deposition rate were investigated. A large region in the terms of preheat temperature and laser power for the formation of cubic pyrochlore‐structured LZ films was mapped under a fixed total pressure of 950 Pa. The morphology of LZ films without laser irradiation showed a dense and glass‐like structure with a flat cauliflower surface. It was changed into a columnar structure with an unflat cauliflower surface by low‐power laser irradiation during deposition process. The transformation occurred once a critical laser power beyond 16 W/cm². Thus, the effect of laser on the deposition of LZ films was a result of double‐side action including both pyrolytic effect and photolytic effect. Plasma gas around the substrate resulted in significant increases in deposition temperature and deposition rate due to self‐propagating high‐temperature reactions between the precursors and O₂. The maximum deposition rate can reach 250 μm/h by LCVD.     

Templated synthesis of urchin-like zinc oxide particles by micro-combustion

Micro-combustion initiated by dielectric barrier discharge plasma has been applied for the removal of carbon template to prepare urchin-like ZnO particles. The combustion is operated at atmospheric pressure and low gas temperature (less than 150 °C), and the template is fully decomposed and rapidly removed. The obtained urchin-like ZnO possesses two distinct morphologies: nanosheets and sub-micro rods. The unique morphologies form on ZnO hexagonal nuclei with the template effect of activated carbon.     

Controlled synthesis of Mg(OH)2 thin films by chemical solution deposition and their thermal transformation to MgO thin films

The chemical solution deposition of Mg(OH)₂ thin films on glass substrates and their transformation to MgO by annealing in air is presented. The chemical solution deposition consists of a chemical reaction employing an aqueous solution composed of magnesium sulfate, triethanolamine, ammonium hydroxide, and ammonium chloride. The as-deposited films were annealed at different temperatures ranging from 325 to 500?°C to identify the Mg(OH)₂-to-MgO transition temperature, which resulted to be around 375?°C. Annealing the as-deposited Mg(OH)₂ films at 500?°C results in homogeneous MgO thin films. The properties of the Mg(OH)₂ and MgO thin films were analyzed by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, UV–Vis spectroscopy, and by circular transmission line model. Results by X-ray diffraction show that the as-deposited thin films have a brucite structure (Mg(OH)₂), that transforms into the periclase phase (MgO) after annealing at 500?°C. For the as-deposited Mg(OH)₂ thin film, a nanowall surface morphology is found; this morphology is maintained after the annealing to obtain MgO, which occurred with the evident formation of pores on the nanowall surface. The assessed chemical composition from X-ray photoelectron spectroscopy yields Mg_0.36O_0.64 (O/Mg ratio of 1.8) for the as-deposited Mg(OH)₂ film, where the expected stoichiometric composition is Mg_0.33O_0.67 (O/Mg ratio of 2.0); the same assessment yields Mg_0.60O_0.40 (O/Mg ratio of 0.7) for the annealed thin film, which indicates the obtainment of a MgO material with oxygen vacancies, given the deviation from the stoichiometric composition of Mg_0.50O_0.50 (O/Mg ratio of 1.0). These results confirm the deposition of Mg(OH)₂ films and the obtainment of MgO after the heat-treatment. The energy band gap of the films is found to be 4.64 and 5.10?eV for the as-deposited and the film annealed at 500?°C, respectively. The resistivity of both Mg(OH)₂ and MgO thin films lies around 10⁸?Ω·cm.     

Nonlinear growth of zinc tin oxide thin films prepared by atomic layer deposition

Zinc tin oxide (ZTO) thin films can be deposited by atomic layer deposition (ALD) with adjustable electrical, optical and structural properties. However, the ternary ALD processes usually suffer from low growth rate and difficulty in controlling film thickness and elemental composition, due to the interaction of ZnO and SnO₂ processes. In this work, ZTO thin films with different Sn levels are prepared by ALD super cycles using diethylzinc, tetrakis(dimethylamido)tin, and water. It is observed that both the film growth rate and atom composition show nonlinear variation versus [Sn]/([Sn]+[Zn]) cycle ratio. The experimental thickness measured by spectroscopic ellipsometry and X-ray reflectivity are much lower than the expected thickness linearly interpolated from pure ZnO and SnO_x films. The [Sn]/([Sn]+[Zn]) atom ratios estimated by X-ray photoelectron spectroscopy have higher values than that expected from the cycle ratios. Hence, to characterize the film growth behavior versus cycle ratio, a numerical method is proposed by simulating the effect of reduced density and reactivity of surface hydroxyls and surface etching reactions. The structure, electrical and optical properties of ZTO with different Sn levels are also examined by X-ray diffraction, atomic force microscope, Hall measurements and ultraviolet–visible–infrared transmittance spectroscopy. The ZTO turns out to be transparent nanocrystalline or amorphous films with smooth surface. With more Sn contents, the film resistivity gets higher (>1 Ω cm) and the optical bandgap rises from 3.47 to 3.83 eV.     

高频热等离子体制备特种粉体研究进展

高频感应热等离子体具有能量密度大、温度高和冷却速率快等特点,是制备特种粉体的重要手段之一. 本工作介绍了过程所在高频热等离子体制备特种粉体方面的研究进展. 利用热等离子体的高温和快速冷却过程,粗颗粒经等离子体弧高温气化,通过控制冷却速率能得到纳米粉体,利用该方法制备了纳米球形硅、铁、钴和镍等粉体,纳米硅粉可用于锂离子电池负极材料. 具有固定熔点的不规则颗粒在等离子体弧中经熔融形成球形液滴,快速冷却能获得规则致密的球形颗粒,通过等离子体球化制备了高熔点的钨、钼、铌、铬等规则致密的球形粉体. 利用活性氢的瞬时强化还原反应,采用化学气相沉积能制备超细钨、钼、镍和铜等球形金属超细粉体. 活性氧有助于调控颗粒的氧化生长过程,采用金属等的氧化反应可获得多种特殊形貌的氧化物.     

不同碳酸盐沉淀剂热分解法制备纳米氧化锌

以硝酸锌为锌源,分别以碳酸钠和碳酸氢铵为沉淀剂,采用热分解碱式碳酸锌工艺制备纳米氧化锌。通过热重分析、晶型测试、平均粒径测试、微观形貌观察等系列对比,分析了以两种碳酸盐为沉淀剂制备氧化锌的过程,建立了生长动力学方程,对比了微观形貌和分散状态。实验结果表明,以碳酸氢铵为沉淀剂制备的前驱体在煅烧温度为200 ℃后直接生成纳米氧化锌,而以碳酸钠为沉淀剂制备的前驱体在煅烧温度为200~250 ℃时先生成碳酸锌然后在300 ℃时完全转变为氧化锌;两种沉淀剂制备纳米氧化锌的生长过程符合不同指数方程生长关系,以碳酸钠为沉淀剂制备纳米氧化锌的生长满足方程y=2.775 04e^{0.004 76x},而以碳酸氢铵为沉淀剂制备纳米氧化锌的生长满足方程y=5.152 96e^{0.002 85x},对比来看以碳酸氢铵为沉淀剂制备纳米氧化锌在相同温度下得到的晶粒尺寸要小;从粒度分布和透射电镜观察分析,在相同温度下也是以碳酸氢铵为沉淀剂制备的纳米氧化锌的粒径较小。     

Improvement in growth yield of single-walled carbon nanotubes with narrow chirality distribution by pulse plasma CVD

A pulse plasma chemical vapor deposition (CVD) technique was developed for improving the growth yield of single-walled carbon nanotubes (SWNTs) with a narrow chirality distribution. The growth yield of the SWNTs could be improved by repetitive short duration pulse plasma CVD, while maintaining the initial narrow chirality distribution. Detailed growth dynamics is discussed based on a systematic investigation by changing the pulse parameters. The growth of SWNTs with a narrow chirality distribution could be controlled by the difference in the nucleation time required using catalysts comprising relatively small or large particles as the key factor. The nucleation can be controlled by adjusting the pulse on/ofF time ratio and the total processing time.     

高频热等离子体热解水氯镁石沉积氧化镁薄膜

我国盐湖资源丰富,其中位于青海的察尔汗盐湖是我国最大的钾肥生产基地。然而在钾肥生产过程中副产的大量水氯镁石（MgCl₂·6H₂O）目前尚得不到有效的利用,“镁害”已经成为盐湖卤水提钾后的首要问题。本文提出以高频热等离子体为高温热源,强化水氯镁石的热解过程,同时将热解产物沉积得到高附加值的MgO薄膜。研究结果表明,该工艺热解效率高,热解得到高纯的MgO薄膜,沉积效率可达到3.2 mm·min^-1,薄膜颗粒粒径处于10～60 nm之间,具有良好的光致发光性能;同时沉积工艺过程简单,适合大规模连续化生产。     

Improving optical and electrical performances of aluminum-doped zinc oxide thin films with laser-etched grating structures

A laser etching method was performed to achieve the dual purpose of fabricating grating structures and laser annealing on aluminum-doped zinc oxide (AZO) thin films, and thus improve the film photoelectric performances. Different line spacings and laser fluences were adopted to systematically explore the optimal laser etching condition. Too narrow line spacings or too high laser fluences led to light reflections at the grating external surface to cause more light dissipation, and too wide line spacings or too low laser fluences resulted in relatively small total grating lateral areas being detrimental to multiple internal light reflections. Moreover, too narrow line spacings brought about laser-caused lattice disorder and too high laser fluences produced laser-ablated spots or overburned traces. Therefore, using the medium line spacing and laser fluence, e.g. 40 μm and 0.6 J/cm² in the present work, was more suitable for synchronously realizing grating structure fabrication and laser annealing. The corresponding AZO film exhibited the maximum figure of merit of 2.89 × 10^?2 Ω^?1, which was 1.6 times that of the untreated AZO film. This study is expected to expand performance improvement methods of TCO films and promote the application of laser-etched grating structures.     

Effect of rapid thermal annealing on the properties of zinc tin oxide films prepared by plasma-enhanced atomic layer deposition

The effect of rapid thermal annealing treatments on the microstructure, surface morphology, and optical characteristics of zinc tin oxide (ZTO) films produced by plasma-enhanced atomic layer deposition was investigated. The ZTO films were annealed in oxygen atmosphere for 2 min at four selected temperatures from 500 to 800 °C. The X-ray diffraction showed that the annealing temperature has a great influence on the crystalline characteristics of ZTO films. The film shows complete amorphous structure for as-deposited ZTO film. Meanwhile, the spinel zinc stannate Zn₂SnO₄ was obtained for the samples annealed from 500 to 800 °C, which shows polycrystalline nature. The X-ray photoelectron spectroscopy proved that the annealing process in oxygen gas can effectively can reduce the oxygen vacancy defects in the films. In addition, the photoluminescence spectroscopy manifests an ultraviolet emission with a broad peak range from 345 to 385 nm. Moreover, the ultraviolet luminescence intensity increases continuously with the increase of annealing temperature. Spectroscopic ellipsometry analyses demonstrate that the refractive index of annealed films increases as the increase of annealing temperature, while the extinction coefficient decreases gradually with the increase of annealing temperature in the visible light range.     

Growth and characterization of fluorocarbon thin films grown from trifluoromethane (CHF3) using pulsed‐plasma enhanced CVD

Trifluoromethane (CHF₃) was used as a precursor gas in pulsed‐plasma enhanced CVD to deposit fluorocarbon films onto Si substrates. The film composition, as measured by X‐ray photoelectron spectroscopy (XPS) of the C1s peak, was observed to change as the plasma duty cycle was changed by varying the plasma off‐time; this offers a route to control the molecular architecture of deposited films. FTIR results indicate that the film is primarily composed of CF_x components, with little or no C H incorporation into the film. The rms roughness of the films is extremely low, approaching that of the Si substrate; the low growth rate and consequent high‐power input/thickness is believed to be partly responsible. CHF₃ produces films with higher % CF₂ compared to other hydrofluorocompound (HFC) monomers (CH₂F₂ and C₂H₂F₄). However, the deposition kinetics for all three HFC gases display similar trends. In particular, at a fixed on‐time of 10 ms, the deposition rate per pulse cycle reaches a maximum at an off‐time of approximately 100 ms. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 842–849, 2000     

溶胶-凝胶法制备掺铝氧化锌薄膜及其近红外反射性能研究

采用溶胶-凝胶法制备了掺铝氧化锌(ZAO)薄膜,用X射线衍射(XRD)、紫外-可见光-近红外分光光度计等分析测试手段对薄膜进行了表征;通过正交试验探讨了镀膜层数、溶胶浓度、铝离子的摩尔分数以及退火温度等因素时掺铝氧化锌(ZAO)薄膜近红外反射率的影响,优选了制备具有高近红外反射率的薄膜的工艺参数.研究结果表明,当溶胶浓...     

超声场中沉淀法纳米氧化锌的制备与表征

将超声辐射应用于以硫酸锌(ZnSO4·7H2O)和草酸(H2C2O4·2H2O)为原料的沉淀法制备纳米氧化锌粉体的工艺过程,制备了平均晶粒尺寸为26nm的氧化锌粉体。通过XRD,DTA—TG和SEM等技术研究了纳米氧化锌的合成过程及粉体性能。结果表明:超声辐射引入普通沉淀法,超声波的空化作用可使前驱体颗粒细化,抑制其团聚并延缓其向凝胶转变,从而可制备出氧化锌纳米粉体。这种方法所得纳米氧化锌粒子外貌为球形,粒度分布均匀,分散性好。     

Rapid thermal annealing effect of transparent ITO source and drain electrode for transparent thin film transistors

We investigated the rapid thermal annealing (RTA) sequence effect on the electrical, optical, morphological, and structural properties of transparent thin film transistors (TTFTs) with an indium gallium zinc oxide (IGZO) channel and an indium tin oxide (ITO) source/drain. The electrical and optical properties of the IGZO channel and the ITO source/drain electrodes were compared as a function of RTA temperature in ambient air. The performance of a TTFT with only an RTA-processed IGZO channel was compared with that of a TTFT with an RTA-processed IGZO channel and ITO source/drain electrodes. Using the circular transmission line measurement (CTLM) method, we suggest a possible mechanism that explains the effect of the RTA process on the performance of the TTFT with only an annealed IGZO channel vs. that with an annealed IGZO/ITO multilayer. The TTFT with an RTA-processed IGZO/ITO multilayer showed a threshold voltage shift, an improved on/off ratio of 3.54 × 10¹¹, a subthreshold swing of 0.33 V/decade, and a high mobility of 8.69 cm²/V·s. This indicates that simultaneous RTA processing for an IGZO channel and an ITO electrode is beneficial for the fabrication of high-performance TTFTs.     

Ferroelectric enhancement of Al-doped HfO2 thin films by rapid electron beam annealing in a low thermal budget

In past few years, there was a great amount of research on ferroelectric Al-doped HfO₂ (HAO) thin films which suffer from the need of high annealing temperatures to achieve significant ferroelectricity. In this work, we realize pronounced remnant polarization 2P_r~29μC/cm² of HAO using rapid electron beam annealing (EBA) with a large area. The simulation of electron beam trajectories reveals that the effect of EBA concentrates on the region ~20 nm below the sample surface, which highly benefits the process integration where a low thermal budget is required. The energy-dispersive X-ray and high-angle annular dark-field analyses reveal the interdiffusion between Al and Hf in the HAO layer treated by EBA. The pronounced ferroelectricity of HAO can be accounted for by the lattice strain, which facilities the formation of the orthorhombic phase, due to the substitution of Al for Hf as supported by the fast Fourier transformation diffraction pattern.     

Preparation by chemical solution deposition and transparent conducting properties of LaRh1-xNixO3 thin films

Transparent conducting thin films have been widely used in lots of fields. The absence of high-performance hole-type transparent conducting thin films, however, seriously limits the wider applications. LaRhO₃ as a type of perovskite material shows hole-type conduction with semiconductor-like properties and no investigations have been carried out about transparent conducting properties on LaRhO₃ thin films. Here, LaRh_1-xNi_xO₃ (x = 0, 0.05, 0.1) thin films were firstly deposited by chemical solution deposition, showing epitaxial growth on single crystal SrTiO₃ (001) substrates with the epitaxial relationship of LaRhO₃(001)[110]||SrTiO₃(001)[110]. With the doping of Ni element, the surface morphology became denser. Hall measurements confirmed that the hole concentration was enhanced with Ni doping, resulting in the decreased resistivity. Low resistivity of 17.3 mΩ cm at 300K was obtained for the LaRh_0.9Ni_0.1O₃ thin films. The electrical transport mechanisms were investigated, showing thermal activation at high temperatures and variable range hopping model for the doped thin films at low temperatures. The transmittance within the visible range for all thin films was higher than 50%. The results will provide a feasible route to deposit hole-type transparent conducting LaRhO₃-based thin films.     

Template-directed synthesis of boron nitride nanotube arrays by microwave plasma chemical reaction

Highly-ordered boron nitride (BN) nanotube arrays have been synthesized by microwave plasma-enhanced chemical vapor deposition (MW-PECVD) below 520 °C under the confinement of anodic aluminum oxide (AAO) template with borane/argon and ammonia/nitrogen as precursors. The low growth temperature and aligned arrangement of the BN nanotubes are beneficial to practical applications despite of the amorphous nature of the product. Novel morphology of Y-branching and dendriform BN nanotubes were also observed when the branching AAO template was used.     

Direct current electrical characterization of plasma polymerized pyrrole-N,N,3,5 tetramethylaniline bilayer thin films

The direct current conduction mechanism in plasma polymerized pyrrole-N,N,3,5 tetramethylaniline (PPPy-PPTMA) bilayer thin films has been discussed in this article. A parallel plate capacitively coupled glow discharge reactor was used to deposit PPPy, PPTMA, and PPPy-PPTMA thin films at room temperature onto glass substrates. The Fourier Transform Infrared analyses showed that the PPPy-PPTMA bilayer thin films contained the structural characteristics of both the PPPy and PPTMA. The current density-voltage characteristics of PPPy-PPTMA bilayer thin films of different deposition time-ratios indicated an increase in electrical conductivity as the proportion of PPTMA was increased in the bilayer films. It is also observed that the conductivity of the bilayer thin film is reduced compared with its component thin films. It is seen that in the low voltage region the current conduction obeys Ohm's law, while the charge transport phenomenon appears to be the space charge limited conduction in the higher voltage region. The mobility of the charges, the free charge carrier density, and the permittivity of the PPPy, PPTMA and PPPy-PPTMA bilayer thin films have been calculated. The permittivity for PPPy, PPTMA and PPPy-PPTMA bilayer thin films were found to be 1.07 × 10⁻¹⁰, 2.2 × 10⁻¹¹, and 1.26 × 10⁻¹⁰ C² N⁻¹ m⁻², respectively; the free charge carrier density were (3.56 ± 0.01) × 10²², 2 × 10²¹ and (5.19 ± 0.02) × 10²² m⁻³ respectively; and the mobility of the charges were found to be (4.4 ± 0.01) × 10⁻¹⁹, 1.3 × 10⁻¹³ and (2.1 ± 0.01) × 10⁻¹⁹ m² V⁻¹ s⁻¹ respectively. PACS: 72.80.Le, 73.21.Ac, 73.40.Rw, 73.50.Gr, 73.61.Ph. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of Ni doping on the structural,electrical, and optical properties of transparent CuCrO2 films grown using pulsed laser deposition

In this study, the structural, electrical, and optical properties of CuCr_1?xNi_xO₂ epitaxial films (x?=?0, 0.01, 0.03, 0.05), which exhibited p-type properties, were investigated. The (001)-oriented epitaxial films were deposited on c-plane α-Al₂O₃ substrates using pulsed laser deposition at a growth temperature of 700?°C and oxygen pressure of 10 mTorr. The optical energy band gap of the CuCr_0.95Ni_0.05O₂ film was determined to be 3.22?eV. The hole carrier concentration of the CuCrO₂ film increased from 5.1?×?10¹⁴ to 2.2?×?10¹⁷ cm^?3 upon doping with 5?at% Ni. Based on Hall measurement and X-ray photoelectron spectroscopy results, it was suggested that the substituted Ni²⁺ dopants at Cr³⁺ sites formed an acceptor level without any charge compensation with Cu²⁺ and/or Cr⁴⁺.