Guiding the Dewetting of Thin Polymer Films by Colloidal Imprinting

Micropatterned surfaces are important in many biomedical and bioengineering applications, such as the development of biosensors. An approach for the creation of ordered surface patterns, fabricated combining colloidal crystals, consisting of ordered layers of micrometric particles, with dewetting of bilayers of thin polymer films is introduced. The produced patterns are both topographical and chemical in nature, consisting of ordered arrays of microscale holes imprinted in a polymer film, with tunable size. The spontaneous dewetting of the polymer film enables this tunability, with a maximum sevenfold increase in lateral size of the holes and sixfold increase in depth from imprinting to coalescence with neighboring holes. Polymer dewetting and layer inversion are seen to compete during the annealing of the polymer bilayers, and the optimal conditions for hole growth are identified. An in‐depth investigation highlights the effects of UV‐ozone treatment on the long‐range ordering of the colloidal crystals and on preventing the dewetting of the imprinted bilayers. Ordered patterns of different size and depth are produced over large areas by tuning of the colloidal crystal assembly, UV surface treatment and dewetting conditions. Potential applications of the micropatterns produced in the present work include microarrays for single cell studies and biosensors.     

Direct Visualization of Local Spin Transition Behaviors in Thin Molecular Films by Bimodal AFM

Thin films of the molecular spin‐crossover complex [Fe(HB(1,2,4‐triazol‐1‐yl)₃)₂] undergo spin transition above room temperature, which can be exploited in sensors, actuators, and information processing devices. Variable temperature viscoelastic mapping of the films by atomic force microscopy reveals a pronounced decrease of the elastic modulus when going from the low spin (5.2 ± 0.4 GPa) to the high spin (3.6 ± 0.2 GPa) state, which is also accompanied by increasing energy dissipation. This technique allows imaging, with high spatial resolution, of the formation of high spin puddles around film defects, which is ascribed to local strain relaxation. On the other hand, no clustering process due to cooperative phenomena was observed. This experimental approach sets the stage for the investigation of spin transition at the nanoscale, including phase nucleation and evolution as well as local strain effects.     

脉冲激光沉积ZnO及其掺杂薄膜的研究

本文用脉冲激光沉积（PLD）法在SiO2基片上制备了ZnO薄膜和Zn1-xMnxO薄膜。X射线衍射、原子力显微镜、紫外-可见分光光度计对ZnO薄膜的测试结果表明：薄膜具有（103）面的择优取向，表面比较平坦；SiO2基片上制备的薄膜在387nm附近存在明显的吸收边，且薄膜的吸收对基片温度变化不明显。通过对Zn1-xMnxO薄膜的吸收光谱分析得出：Mn离子的掺杂改变了ZnO薄膜的禁带宽度，随Mn离子的掺杂量的增加，薄膜禁带宽度增加；薄膜的光吸收也从直接跃迁过渡为间接跃迁过程。     

有机凝胶法制备Sr0.5Ba0.5Nb2O6铁电薄膜及其电性能研究

采用有机凝胶法制备了Sr0．5Ba0.5Nb2O6(SBN50)铁电薄膜．研究了pH值和EDTA的用量对Sr-Ba-Nb前驱体溶液稳定性的影响，并对不同pH值条件下获得的Sr-Ba-Nb干凝胶的热分解历程进行了对比．计算和实验结果表明，制备Sr-Ba-Nb前驱体溶液的最佳pH=8，EDTA：金属离子(摩尔比)=2：1．在700℃下退火30min所得SBN50薄膜为单一钨青铜结构多晶薄膜．室温下，测试频率1kHz时，薄膜的介电常数为221，介电损耗为0．02，剩余极化强度Pr=8．17μC／cm^2，矫顽场Ec=16．9kV／cm．     

Finite Size Effects on the Switching Dynamics of Spin‐Crossover Thin Films Photoexcited by a Femtosecond Laser Pulse

Using ultrafast optical absorption spectroscopy, the room‐temperature spin‐state switching dynamics induced by a femtosecond laser pulse in high‐quality thin films of the molecular spin‐crossover (SCO) complex [Fe(HB(tz)₃)₂] (tz = 1,2,4‐triazol‐1‐yl) are studied. These measurements reveal that the early, sub‐picosecond, low‐spin to high‐spin photoswitching event, with linear response to the laser pulse energy, can be followed under certain conditions by a second switching process occurring on a timescale of tens of nanoseconds, enabling nonlinear amplification. This out‐of‐equilibrium dynamics is discussed in light of the characteristic timescales associated with the different switching mechanisms, i.e., the electronic and structural rearrangements of photoexcited molecules, the propagation of strain waves at the material scale, and the thermal activation above the molecular energy barrier. Importantly, the additional, nonlinear switching step appears to be completely suppressed in the thinnest (50 nm) film due to the efficient heat transfer to the substrate, allowing the system to retrieve the thermal equilibrium state on the 100 ns timescale. These results provide a first milestone toward the assessment of the physical parameters that drive the photoresponse of SCO thin films, opening up appealing perspectives for their use as high‐frequency all‐optical switches working at room temperature.     

CoFe合金薄膜的制备及原子力表征

室温下采用射频磁控溅射技术在涤纶纺粘非织造布表面沉积钴铁(CoFe)合金薄膜.通过原子力显微镜(AFM)观察了CoFe合金薄膜在无纺织布表面沉积的微观结构,并较为系统地分析了溅射时间、溅射压强及溅射功率对CoFe合金薄膜微观结构的影响.结果表明,磁控溅射的工艺参数配置对CoFe合金薄膜表面形貌的影响很大,溅射时间的长短、溅射功率的大小对成膜的均匀性有很大影响,在一定的溅射压强(0.5Pa)时合金颗粒将会因团聚而急速增大.     

近距离升华制备CdTe掺Te薄膜的结构与电性能研究

采用近距离升华(Close-Spaced-Sublimation,CSS)技术制备CdTe及掺Te薄膜.并利用XRF、XRD、SEM及Hall系统研究了其含量、结构、表面形貌和电性能.结果表明,CSS技术制备的CdTe薄膜晶形好,晶粒度较RF方法制备的薄膜增大约100倍.Te掺入CdTe薄膜后,改变了CdTe膜的结晶特性,适当掺入Te可以促进CdTe晶格的生长,并导致Cdrre膜晶格常数变大.薄膜面电阻率降低,面载流子浓度增大,以及载流子迁移率的增大,表明掺杂Te后CdTe膜的电导性能大大改善.     

YZO薄膜的Sol-gel制备及其性能

采用Sol-gel法在普通载玻片上制备YZO薄膜.研究了陈化时间和Y掺杂量对薄膜晶体结构、表面形貌和光学性能的影响,并分析和探讨了工艺参数与结构和性能之间的关系.实验结果表明,YZO薄膜为纤锌矿结构,呈c轴择优取向生长,平均透光率(380～760nm)超过85%.实验还发现,陈化时间存在最优值,YZO薄膜随着Y掺杂量的增加晶体结晶质量下降.     

Growth and Characterization of YBCO Thin Films by Sequential Deposition and Annealing

A novel thin film growth procedure, sequential deposition and annealing (SDA), which contains the advantages of both in situ and ex situ procedures, was proposed. Y₁Ba₂Cu₃O_{7 – x} (YBCO) high temperature superconducting thin films were grown and characterized by the SDA procedure. Purely c-axis-oriented YBCO thin films with no foreign phases and other oriented grains were successfully prepared. The superconducting transition properties of SDA-grown YBCO thin films were measured by measurement of inductance and resistance. The inductance measurements gave a T _c ^onset of 85 K and a T _c of 5 K. The resistance measurements gave a T _c ^onset of 90 K and a T _c of 5 K. Atomic force microscopy studies showed that SDA-grown YBCO thin films had micrometer-size grains surrounded by many nanometer-size grains. The nanometer-size grains in SDA-grown YBCO thin films are responsible for degradation of superconducting transition properties.     

溅射法制备TiO2薄膜过程中靶中毒现象的消除及样品表征

用氧脉冲直流反应磁控溅射法,在载玻片衬底上制备了不同初始氧浓度和不同断氧时间％的多晶TiO2纳米薄膜,并对薄膜的厚度、晶体结构及表面形貌进行了研究。研究发现,脉冲式通氧能有效消除靶中毒,将薄膜沉积速率最大提高到3～5nm／min,并且当断氧时间大于30s时,沉积速率在2．5nm／min以上;薄膜的晶体结构和形貌随着氧浓度和断氧时间而变化,在初始氧浓度为30％、断氧时间为30s时,金红石结构样品具有最佳结晶程度,并且薄膜的表面平整、晶粒尺寸分布均匀,而锐钛矿结构的最佳结晶条件是氧浓度30％或50％、断氧时间20s.     

Peculiarities of Pinning and Microwave Absorption Hysteresis in Thin Superconducting Films

The results of experimental and theoretical studies of the hysteretic microwave absorption (MWA) in the superconducting Bi₂Sr₂CaCu₂O₈ thin films are presented. It has been found experimentally that the hysteresis loop manifests some unusual features such as the non-monotone hysteresis variation and the change of a hysteresis sign. We have shown that such unusual behavior is due to the special nature of the bulk pinning in a superconducting film with a thickness comparable with the field penetration depth. The theoretical model of the MWA hysteresis has been developed taking into account the inhomogeneous distribution of centers with different symmetry of a pinning potential and their variation with the magnetic field value.     

甩胶喷雾热分解法制备ITO薄膜及光电性能研究

按In:Sn(物质的量比)=9:1,InCl3·4H2O和SnCl4·5H2O为前驱物,采用自制甩胶喷雾热分解制备薄膜装置在普通玻璃衬底上沉积了ITO薄膜,结果表明,采用自制甩胶喷雾热分解制备薄膜新装置成功制备出ITO薄膜。该装置结构简单、操作方便。制备ITO薄膜优化条件为:甩胶转速800r/min、衬底温度250℃、退火温度450℃、载气为空气、流量为7L/min、液体雾化速度0.2ml/min、雾粒速度3.5m/s。薄膜的沉积时间为5min,薄膜厚度约1000nm,最低电阻率为0.75*10-4Ω·cm,薄膜在可见光范围(波长在400-700nm)内平均透光率为87.2%。衬底温度在200℃以上时呈现立方相结构。     

磁控溅射制备铝掺杂氮化铜薄膜的结构及光电性能研究

以高纯铜和铝为靶材,氮气和氩气分别为源气体和工作气体,采用双靶共溅射磁控技术在单晶硅和石英片上制备了铝掺杂氮化铜(Cu₃N:Al)薄膜。对Cu₃N:Al薄膜的表面形貌、晶体结构、光透射性能和电学性能等进行表征、分析。研究结果表明,掺杂Al原子进入Cu₃N晶格空位;随着Al靶的直流溅射功率增大,Cu₃N:Al薄膜中Al含量增加;Al掺杂使得薄膜颗粒尺寸增大,薄膜表面变得粗糙。Cu₃N:Al薄膜表现为半导体特性,其光学带隙范围在1.41-1.80 eV;Al掺杂后,Cu₃N薄膜的光学带隙减小,其原因是掺杂Al原子改变了晶体内非平衡载流子寿命,导致薄膜的光学带隙降低。可见,通过调控Cu₃N薄膜中掺杂金属原子含量,可实现对其光电特性的调制。     

磁控溅射沉积Cu-W薄膜的特征及热处理的影响

采用磁控共溅射法制备含钨1.51%~14.20%(原子分数,下同)的Cu-W合金薄膜,并用EDX、XRD、SEM、显微硬度仪和电阻仪研究了其成分、结构及性能。结果表明,添加W可显著细化Cu-W薄膜基体相晶粒,晶粒尺寸随W含量的增加而减小,Cu-W薄膜呈纳米晶结构。Cu-W薄膜中存在W在Cu中形成的fcc Cu(W)非平衡亚稳过饱和固溶体,固溶度随W含量的增加而提高,最大值为10.65%。与纯Cu膜对比发现,薄膜的显微硬度和电阻率总体上随W含量的增加而显著增大。经200℃、400℃及650℃热处理1h后,Cu-W薄膜基体相晶粒长大,EDX分析显示晶界处出现富W第二相;薄膜显微硬度降低,电阻率下降,降幅与退火温度呈正相关。添加W引起的晶粒细化效应以及退火中基体相晶粒度增大分别是Cu-W薄膜微观结构和性能形成及演变的主要原因。     

Controllable Colloidal Synthesis of Tin(II) Chalcogenide Nanocrystals and Their Solution‐Processed Flexible Thermoelectric Thin Films

A systematic colloidal synthesis approach to prepare tin(II, IV) chalcogenide nanocrystals with controllable valence and morphology is reported, and the preparation of solution‐processed nanostructured thermoelectric thin films from them is then demonstrated. Triangular SnS nanoplates with a recently‐reported π‐cubic structure, SnSe with various shapes (nanostars and both rectangular and hexagonal nanoplates), SnTe nanorods, and previously reported Sn(IV) chalcogenides, are obtained using different combinations of solvents and ligands with an Sn⁴⁺ precursor. These unique nanostructures and the lattice defects associated with their Sn‐rich composition allow the production of flexible thin films with competitive thermoelectric performance, exhibiting room temperature Seebeck coefficients of 115, 81, and 153 μV K^?1 for SnS, SnSe, and SnTe films, respectively. Interestingly, a p‐type to n‐type transition is observed in SnS and SnSe due to partial anion loss during post‐synthesis annealing at 500 °C. A maximum figure of merit (ZT) value of 0.183 is achieved for an SnTe thin film at 500 K, exceeding ZT values from previous reports on SnTe at this temperature. Thus, a general strategy to prepare tin(II) chalcogenide nanocrystals is provided, and their potential for use in high‐performance flexible thin film thermoelectric generators is demonstrated.     

正偏压作用下多弧离子镀ZrO2薄膜的组织结构与力学性能研究

在氧气和氩气的混合气体中,以O2/Ar流量比固定为1/4的条件,通过改变正偏压大小,采用多弧离子镀方法制备了新型高k栅介质——ZrO2薄膜。通过X射线衍射(XRD)和原子力显微镜(AFM)研究了在不同正偏压作用下正偏压值与薄膜的相结构、表面形貌之间的关系,利用纳米压痕仪测量了不同正偏压作用下沉积得到的ZrO2薄膜的硬度及弹性模量,并观察了ZrO2薄膜经不同温度退火处理后的相结构及表面形貌的变化。结果表明,在各个正偏压条件下,薄膜结构呈微晶或非晶;ZrO2薄膜的均方根粗糙度随着正偏压的升高而降低;正偏压为100V时硬度和弹性模量均达到最大值,分别为16.1GPa和210GPa。