ZnO薄膜的性质对水热生长ZnO纳米线阵列的影响

用水热法在ZnO薄膜上制备了直径、密度及取向可控的ZnO纳米线阵列。ZnO薄膜是通过原子层沉积(ALD)方法制备并在不同温度下退火处理得到的,退火温度对ZnO薄膜的晶粒尺寸、结晶质量和缺陷性质有很大的影响。而ZnO薄膜的性质对随后生长的ZnO纳米线的直径、密度及取向能起到调节控制的作用。通过扫描电子显微镜(SEM)、X射线衍射(XRD)仪和光致发光(PL)测试对ZnO薄膜和ZnO纳米线进行了表征。最后得到的垂直取向的ZnO纳米线阵列适合在发光二极管和太阳能电池等领域使用。     

等离子增强原子层沉积低温生长AlN薄膜

采用等离子增强原子层沉积技术在单晶硅基体上成功制备了AlN晶态薄膜, 利用椭圆偏振仪、原子力显微镜、小角掠射X射线衍射仪、高分辨透射电子显微镜、 X射线光电子能谱仪对样品的生长速率、表面形貌、晶体结构、薄膜成分进行了表征和分析, 结果表明, 采用等离子增强原子层沉积制备AlN晶态薄膜的最低温度为200 ℃, 薄膜表面平整光滑, 具有六方纤锌矿结构与(100)择优取向, Al_2p与N_1S的特征峰分别为74.1 eV与397.0 eV, 薄膜中Al元素与N元素以Al-N键相结合, 且成分均匀性良好. 关键词： 氮化铝 等离子增强原子层沉积 低温生长 晶态薄膜     

Study on crystalline to amorphous structure transition of Cr coatings by magnetron sputtering

The influence of deposition rate on crystalline to amorphous microstructure transition of Cr coatings was studied through preparation of Cr coatings deposited onto silicon wafers using magnetron sputtering technique. The microstructure and morphology of Cr coatings were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Results show that Cr coating prepared at 400 W exhibits dense columnar crystalline structure and the crystallite size and crystallization rate are increased expressly in the initial 5 min. When the deposition rate achieved to the maximum, Cr coating shows a case of infinite periodic renucleation where new crystals are assumed to be nucleated periodically on the surfaces of growing crystals and strong persistence of the columnar growth morphology is apparent. However, Cr coating exhibits overall microstructure of amorphous phase mixed with a few nano-crystal grains as the deposition rate decreases to the minimum.     

Transmission electron microscopy study of epitaxial La0.8MnO3 thin films on SrTiO3

The structure and microstructure of La_0.8MnO₃ thin films on SrTiO₃ substrates, fabricated by pulsed laser deposition at substrate temperatures of 873?K and 1073?K, have been studied by transmission electron microscopy. In both films, columnar growth morphology has been observed. The columnar grain size is found to increase with increasing substrate temperature. In the film deposited at a substrate temperature of 1073?K, there is only one rhombohedral phase. However, two phases, a rhombohedral one and an orthorhombic one, have been observed in the film deposited at 873?K.     

Photoelectrochemical properties of texture‐controlled nanostructured α‐Fe2O3 thin films prepared by AACVD

Nanostructured α‐Fe₂O₃ thin film electrodes were deposited by aerosol‐assisted chemical vapour deposition (AACVD) for photoelectrochemical (PEC) water splitting on conducting glass substrates using 0.1 M methanolic solution of Fe(acac)₃. The XRD analysis confirmed that the films are highly crystalline α‐Fe₂O₃ and free from other iron oxide phases. The highly reproducible electrodes have an optical bandgap of ～2.15 eV and exhibit anodic photocurrent. The current–voltage characterization of the electrodes reveals that the photocurrent density strongly depended on the film morphology and deposition temperature. Scanning electron microscopy (SEM) analysis showed a change in the surface morphology with the change in deposition temperature. The films deposited at 450 °C have nanoporous structures which provide a maximum electrode/electrolyte interface. The maximum photocurrent density of 455 µA/cm² was achieved at 0.25 V vs. Ag/AgCl/3M KCl (～1.23 V vs. RHE) and the incident photon to electron conversion efficiency (IPCE) was 23.6% at 350 nm for the electrode deposited at 450 °C. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Effects of deposition temperature and thickness on the structural properties of thermal evaporated bismuth thin films

Bismuth (Bi) thin films of different thicknesses were deposited onto Si(1 0 0) substrate at various substrate temperatures by thermal evaporation technique. Influences of thickness and deposition temperature on the film morphologies, microstructure, and topographies were investigated. A columnar growth of hexahedron-like grains with bimodal particle size distribution was observed at high deposition temperature. The columnar growth and the presence of large grains induce the Bi films to have large surface roughness as evidenced by atomic force microscopy (AFM). The dependence of the crystalline orientation on the substrate temperature was analyzed by X-ray diffraction (XRD), which shows that the Bi films have completely randomly oriented polycrystalline structure with a rhombohedral phase at high deposition temperature (200 °C) and were strongly textured with preferred orientation at low deposition temperatures (30 and 100 °C).     

金属诱导生长与超高真空化学气相沉积方法相结合制备多晶锗硅薄膜

采用金属Ni诱导与超高真空化学气相沉积(UHVCVD)相结合的方法，在热氧化硅衬底上生长了多晶锗硅薄膜.利用X射线衍射(XRD)、场发射扫描电镜(SEM)等对多晶锗硅薄膜的质量、表面形貌进行了测试分析，并就生长参数以及金属Ni对薄膜性能的影响进行了研究.结果表明：1)在420—500℃范围内，金属Ni具有明显的诱导作用；2)Ni层厚度对薄膜质量及形貌的影响使得晶粒尺寸随Ni厚度增加存在一极大值.在Ni层厚度为60nm时，能够获得晶粒尺寸均匀，晶粒大小为500—600nm，结晶质量良好的多晶锗硅薄膜. 关键词： 超高真空化学气相沉积 金属诱导 镍 多晶锗硅     

Effect of structure variation on thermal conductivity of hydrogenated silicon film

Hydrogenated silicon film was fabricated by using plasma enhanced chemical vapor deposition method. The influence of crystalline volume fraction variation on the thermal conductivity was investigated. The relation between crystalline volume and film thickness was characterized by using spectroscopic ellipsometry with Bruggeman effective medium (BEMA) model. The thermal conductivity of silicon film was measured based on Fourier thermal transmitting law using sputtering platinum as electrode. The results demonstrate that the thermal conductivity of silicon film is proportional to the volume fraction of crystalline silicon, and there is crystalline and thermal conductive gradient between surface and bottom in the microcrystalline film.     

Bicontinuous network of electron donor-acceptor composites achieved by additive-free sequential deposition for efficient polymer solar cells

We report that sequential deposition of a highly crystalline polymer donor and a soluble fullerene acceptor leads to a well-defined interpenetrating network and enhanced power conversion efficiencies in bilayer polymer solar cells. Even without the use of solvent additives, layered thin films of poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3‴-di(2-octyldodecyl)-2,2’; 5′,2’’; 5″,2‴-quaterthiophen-5,5‴-diyl)] (PffBT4T-2OD) and [6,6]-phenyl C₇₁-butyric acid methyl ester (PC₇₁BM), as electron donor and acceptor materials, respectively, showed bicontinuous networks similar to those of a PffBT4T-2OD:PC₇₁BM bulk-heterojunction (BHJ) thin film processed with 1,8-diiodooctane (DIO) as a solvent additive. Transmission electron microscopy results confirmed the BHJ-like morphology of the bilayered PffBT4T-2OD/PC₇₁BM thin films. Bilayer solar cells fabricated without the DIO additive produced a power conversion efficiency of η ≈ 7.65%, which is even higher than that of a BHJ solar cell fabricated with the DIO additive (η ≈ 7.04%). These results demonstrate that a highly crystalline polymer donor and an electron-accepting small molecule can be a good combination for efficient bilayer polymer solar cells.     

Humidity controlled crystallization of thin CH3NH3PbI3 films for high performance perovskite solar cell

Control of crystallization of a solution‐processed perovskite layer is of prime importance for high performance solar cells. In spite of the negative effect of water on perovskite solar energy conversion in several previous works, we observed that humidity plays a critical role to develop a thin uniform, dense perovskite film with preferred crystals, in particular, in a device with architecture of ITO/PEDOT:PSS/CH₃NH₃PbI₃/ PC₇₁BM/LiF/Al fabricated by two‐step sequential spin‐coating process. Humidity controlled spin‐coating of CH₃NH₃I on the pre‐formed PbI₂ layer was the most influential process and systematic structural investigation as a function of humidity revealed that grains of CH₃NH₃PbI₃ perovskite crystals increase in size with their preferred orientation while film surface becomes roughened as the humidity increases. The performance of a device was closely related to the humidity dependent film morphology and in 40% relative humidity, the device exhibited the maximum power conversion efficiency of approximately 12% more than 10 times greater than that of a device fabricated at 20% humidity. The results suggest that our process with controlled humidity can be another efficient route for high performance and reliable perovskite solar cells. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Structure and mechanical properties of reactive sputtering CrSiN films

CrSiN films with various Si contents were deposited by reactive magnetron sputtering using the co-deposition of Cr and Si targets in the presence of the reactive gas mixture. Comparative studies on microstructure and mechanical properties between CrN and CrSiN films with various Si contents were carried out. The structure of the CrSiN films was found to change from crystalline to amorphous structure as the Si contents increase. Amorphous phase of Si₃N₄ compound was suggested to exist in the CrSiN film. The growth of films has been observed from continuous columnar structure, granular structure to glassy-like appearance morphology with the increase of silicon content. The film fracture changed from continuous columnar structure, granular structure to glassy-like appearance morphology with the increase of silicon content. Two hardness peaks of the films as function of Si contents have been discussed.     

High‐Pressure Evaporation‐Based Nanoporous Black Sn for Enhanced Performance of Lithium‐Ion Battery Anodes

Increasing the surface area to improve chemical activity is an unending task from conventional catalysis to recently emerging electrochemical energy conversion and storage. Here, a simple, vacuum‐deposition‐based method to form nanoporous structures of metals is reported. By utilizing thermal evaporation at a high pressure, fractal‐like nanoporous structures of Sn with porosity exceeding 98% are synthesized. The obtained nanostructure consists of nanoparticle aggregates, and the morphology can be controlled by adjusting the working pressure. The formation of the nanoporous structure is explained by homogeneous nucleation and diffusion‐limited aggregation, where nanoparticles produced by the repeated collisions of evaporated atoms adhere to the substrate without diffusion, forming porous aggregates. Due to the easy oxidation of Sn, the constituent nanoparticles are covered with amorphous SnO_x and crystalline SnO phases. When the nanoporous Sn/SnO_x aggregates are applied to a lithium‐ion battery anode through direct deposition on a Cu foil current collector without binders or conducting additives, the nanoporous Sn/SnO_x anode shows greatly enhanced cyclability and exceptional rate performance compared to those of a dense Sn thin film anode. The approach investigated in this work is expected to provide a new platform to other fields that require highly porous structures.     

Morphology of open films of discotic hexagonal columnar liquid crystals as probed by grazing incidence X-ray diffraction

The structure and the orientation of thermotropic hexagonal columnar liquid crystals are studied by grazing incidence X-ray diffraction (GIXD) for different discotic compounds in the geometry of open supported thin films. Whatever the film deposition mode (either spin-coating or vacuum evaporation) and the film thickness, a degenerate planar alignment with the liquid crystalline columns parallel to the substrate is found. However, if a specific thermal process is applied to the liquid crystal film, homeotropic anchoring (columns normal to the interface) can be stabilized in a metastable state.     

Structural evolution and epitaxial stabilisation of pulsed laser deposited Sm0.55Nd0.45NiO3 solid solution nanostructured films on undoped Si (1 0 0) and NdGaO3 substrates

We report on the effects of substrate, ambient oxygen pressure and deposition time on the crystal structure, and morphology of Sm_0.55Nd_0.45NiO₃ solid solution nanostructured films synthesized by pulsed-laser deposition. In each film the structure was found to be consistent with a perovskite structure with preferential planes growth and reveals a strong orientation along the orthorhombic (2 1 0) plane of the perovskite subcell for the film deposited on NdGaO₃ where highly crystalline films were obtained within 15 min deposition time with a low surface roughness of 8.79 nm. Similar structure is observed on Si (1 0 0) substrate only at O₂ pressure of 0.4 mbar. The surface morphology of the different samples shows a net dense film structure with several droplets population. The nano-scaled droplets are in general spherical in shape; a detailed analysis indicates that the laser ablation of this nickelate family is governed to a certain extent by a heat transfer phenomenon.     

Pulsed electron beam deposition of highly oriented thin films of polytetrafluoroethylene

Thin films of polytetrafluoroethylene (PTFE) were deposited by pulsed electron deposition (PED) technique. The transmission electron microscopy (TEM) image of the RT fabricated (20 Å thick) film on carbon coated copper grid shows crystalline nature. Infrared spectra show one to one correspondence between PED ablated film and the PTFE bulk target. The asymmetrical and symmetrical -CF₂- stretching modes were observed at 1220 and 1156 cm⁻¹, respectively. The -CF₂- wagging and bending modes occur at 644 and 512 cm⁻¹, respectively. X-ray diffraction patterns of the film deposited at room temperature (RT) show oriented film along (1 0 0) plane of hexagonal structure and the crystalline nature is retained up to 300 °C on vacuum annealing. The room temperature fabricated film shows smooth and pin hole free surface whereas post-annealing brings discontinuity, roughness and pin holes.     

高择优取向铌酸锶钡薄膜的射频磁控溅射制备

采用溶胶-凝胶法在(100)Si单晶上预先制备出掺钾(K)的铌酸锶钡(SBN)缓冲层,利用射频磁控溅射法在缓冲层KSBN上沉积出高择优取向的铌酸锶钡薄膜,获得了磁控溅射法制备择优取向铌酸锶钡薄膜的相关工艺参数,研究发现,KSBN缓冲层能够很有效地克服衬底与SBN薄膜之间较大的晶格失配,在氧气氩气的比例为1∶2,工作气压为10 Pa,溅射功率300 W,衬底温度300℃,退火温度为800℃的工艺条件下,能够获得c轴高度择优取向的铌酸锶钡铁电薄膜.利用X射线衍射仪,原子力显微镜等仪器分析了薄膜 关键词： 磁控溅射 高择优取向 p-n结效应     

Strain evolution and morphological transition of magnetron-sputtered CeO2 thin films induced by deposition parameters

Cerium dioxide (CeO₂) films were fabricated on yttria-stabilized zirconia (YSZ) single crystals using unbalanced radio frequency (RF) magnetron sputtering. X-ray diffraction measurements revealed film strain discrepancies under different deposition parameters. Strain evolution was induced by varying sputtering pressure, RF power, and sputtering gas. A distinct morphological transition from a granular surface to an interwoven surface was also realized by varying the above parameters. On the basis of the “atomic peening” mechanism, the influence of different parameters on film strain was discussed. The film surface characteristics were revealed to be highly correlated with film strain. YBa₂Cu₃O_7−δ (YBCO) films were post-deposited on the as-grown CeO₂/YSZ(001) stack by using the trifluoroacetate metal-organic deposition (TFA-MOD) method. The superconducting property of the YBCO layer varied significantly with the morphology of the CeO₂ buffer films.     

Biaxial Orientation Mechanism of Drawn Natural Rubber. II. Quantitative Analysis of the Biaxial Orientation

Natural rubber film was prepared from triple centrifuged latex. The film was uniaxially drawn at room temperature and the induced crystalline orientation was quantitatively studied by wide angle X‐ray diffraction. The intensity distribution of 200 and 120 reflections confirmed that the induced crystals have a biaxial orientation with the c‐axis parallel to the draw direction. The orientation of the a‐axis was evaluated by using an orientation function of the (200) plane. The function (F ₂₀₀) indicated that the crystalline a‐axis is parallel to the film surface depending on the draw ratio and on positions in the film. The experimental results are possible to explain by shish‐kebab‐like crystallization developed from a highly oriented fibril. The secondary crystallization grows perpendicularly to the draw direction along the a‐axis. The population of the secondary crystals is controlled by an ellipsoidal free space. The shape of the ellipsoid is changed by the fibril distribution depending on width and thickness of the sample film. In this study, the quantitative biaxial orientation is consistently explained by the shish‐kebab‐like crystallization and the ellipsoidal free space.     

Improving organic field-effect transistors based on double active layers structure

Organic field-effect transistors (OFETs) were fabricated based on double active layers structure. Different substrate temperatures and thermal treatment were adopted to prepare double active layers and optimize film morphology. The grain size of organic films can be effectively controlled by the change in substrate temperature in the process of deposition. An improved device performance was obtained compared with conventional single layer devices. This result is attributed to the introduction of double active layers. We believe that this kind of optimization will simultaneously improve charge injection and transportation of OFETs.