Hydrophobic switching nature of methylcellulose ultra-thin films: thickness and annealing effects

We have studied the thermosensitive property of methylcellulose (MC) thin films supported on Si substrate by static sessile drop contact angle measurements, and their surface properties and thin film structure by x-ray reflectivity (XRR) and atomic force microscopy (AFM) techniques. From the static sessile drop contact angle measurements, the MC thin films showed the characteristic hydrophilic-to-hydrophobic transition at ～70?°C, which is the lower critical solution temperature of the bulk solution volume phase separation transition. For films with thickness d ≤ R(g), the onset of such a transition is affected by the film thickness while very thick films, d ? R(g), yielded higher contact angles. Annealing the MC thin films with thicknesses ～200 ? (near the radius of gyration, R(g), of the polymer) below the bulk glass transition temperature (T(g) ～ 195?° C) would not change the hydrophobic switch nature of the film but annealing 'at' and above the bulk T(g) would change its surface property. From surface topography images by AFM, there were no significant changes in either the roughness or the film texture before and after annealing. With XRR data, we were able to determine that such changes in the surface properties are highly correlated to the film thickness changes after the annealing process. This study, we believe, is the first to examine the thermal annealing affects on the thermal response function of a thermoresponsive polymer and is important for researching how to tailor the hydrophobic switching property of MC thin films for future sensing applications.     

Effect of substrate morphology on the roughness evolution of ultra thin DLC films

The effect of substrate roughness on growth of ultra thin diamond-like carbon (DLC) films has been studied. The ultra thin DLC films have been deposited on silicon substrates with initial surface roughness of 0.15, 0.46 and 1.08 nm using a filted cathodic vacuum arc (FCVA) system. The films were characterized by Raman spectroscope, transmission electron microscope (TEM) and atomic force microscopy (AFM) to investigate the evolution of the surface roughness as a function of the film thickness. The experimental results show that the evolution of the surface morphology in an atomic scale depends on the initial surface morphology of the silicon substrate. For smooth silicon substrate (initial surface roughness of 0.15 nm), the surface roughness decreased with DLC thickness. However, for silicon substrate with initial surface roughness of 0.46 and 1.08 nm, the film surface roughness decreased first and then increased to a maximum and subsequently decreased again. The preferred growth of the valley and the island growth of DLC were employed to interpret the influence of substrate morphology on the evolution of DLC film roughness.     

Properties of Cu film and Ti/Cu film on polyimide prepared by ion beam techniques

Cu film and Ti/Cu film on polyimide substrate were prepared by ion implantation and ion beam assisted deposition (IBAD) techniques. Three-dimension white-light interfering profilometer was used to measure thickness of each film. The thickness of the Cu film and Ti/Cu film ranged between 490 nm and 640 nm. The depth profile, surface morphology, roughness, adhesion, nanohardness, and modulus of the Cu and Ti/Cu films were measured by scanning Auger nanoprobe (SAN), atomic force microscopy (AFM), and nanoindenter, respectively. The polyimide substrates irradiated with argon ions were analyzed by scanning electron microscopy (SEM) and AFM. The results suggested that both the Cu film and Ti/Cu film were of good adhesion with polyimide substrate, and ion beam techniques were suitable to prepare thin metal film on polyimide.     

Effect of temperature on pulsed laser deposition of HgCdTe films

HgCdTe thin films have been deposited on Si(1 1 1) substrates at different substrate temperatures by pulsed laser deposition (PLD). An Nd:YAG pulsed laser with a wavelength of 1064 nm was used as laser source. The influences of the substrate temperature on the crystalline quality, surface morphology and composition of HgCdTe thin films were characterized by X-ray diffraction (XRD), selected area electron diffraction (SAED), atomic force microscopy (AFM) and energy dispersive X-ray spectroscopy (EDS). The results show that in our experimental conditions, the HgCdTe thin films deposited at 200 °C have the best quality. When the substrate temperature is over 250 °C, the HgCdTe film becomes thermodynamically unstable and the quality of the film is degraded.     

聚酰亚胺薄膜表面粗糙度的影响因素

 采用热蒸发气相沉积聚合方法（VDP）制备了聚酰亚胺(PI)薄膜,研究了设备、衬底温度、升温过程和单体配比因素对PI薄膜表面形貌的影响。利用干涉显微镜和扫描电镜对薄膜表面形貌进行了分析;利用原子力显微镜测定了薄膜表面粗糙度。结果表明：设定蒸发源-衬底距离为74 cm时可成连续膜;蒸发源采用一段升温和多段升温时,膜表面均方根粗糙度分别为291.23 nm和61.99 nm;采用细筛网可防止原料的喷溅;均苯四甲酸二酐和4,4′-二氨基二苯醚（PMDA和ODA）单体沉积速率比值为0.9∶1时,膜表面均方根粗糙度值可减小至3.30 nm;沉积衬底温度保持30 ℃左右时,膜表面均方根粗糙度为4.01 nm, 随温度的上升,膜表面质量会逐渐变差。     

基片温度对PLD制备ZnO薄膜光学常数的影响

光谱椭偏仪被用来研究用脉冲激光沉积方法在Si(100)基片上,温度分别为400,500,600,700 ℃制备的ZnO薄膜的特性。利用三层Cauchy散射模型拟合椭偏参数,计算了每个温度下制备的ZnO薄膜在400~800 nm波长范围内的折射率(n)和消光系数(k)。发现基片温度对光学常数有很大的影响。通过分析XRD表征的晶体结构和 AFM表征的薄膜表面形貌,发现折射率的变化归因于薄膜堆积密度的变化。为了获得具有较好的光学和薄膜质量的ZnO薄膜,相比与其他沉积温度600 ℃或许是最佳的沉积温度。     

衬底温度对PLD制备的Mo薄膜结构及表面形貌的影响

 运用脉冲激光沉积(PLD)技术在Si(100)基片上沉积了金属Mo薄膜。在激光重复频率2 Hz,能量密度5.2 J/cm²,本底真空10^－6 Pa的条件下,研究Mo薄膜的结构和表面形貌,讨论了衬底温度对薄膜形貌与结构的影响。原子力显微镜(AFM)图像和X射线小角衍射(XRD)分析表明,薄膜表面平整、光滑,均方根粗糙度小于2 nm。沉积温度对Mo薄膜结构和表面形貌影响较大,在373~573 K范围内随着温度升高,薄膜粗糙度变小,结晶程度变好。     

Annealing effects on the surface morphologies of thin PS/PMMA blend films with different film thickness

The surface morphology evolution of three thin polystyrene (PS)/polymethyl methacrylate (PMMA) blend films (<70 nm) on SiO_x substrates upon annealing were investigated by atomic force microscopy (AFM) and some interesting phenomena were observed. All the spin-coated PS/PMMA blend films were not in thermodynamic equilibrium. For the 67.1 and the 27.2 nm PS/PMMA blend films, owing to the low mobility of the PMMA-rich phase layer at substrate surfaces and interfacial stabilization caused by long-range van der Waals forces of the substrates, the long-lived metastable surface morphologies (the foam-like and the bicontinuous morphologies) were first observed. For the two-dimensional ultrathin PS/PMMA blend film (16.3 nm), the discrete domains of the PS-rich phases upon the PMMA-rich phase layer formed and the secondary phase separation occurred after a longer annealing time.     

Effect of annealing on the surface and band gap alignment of CdZnS thin films

Effects of the annealing temperature on structural, optical and surface properties of chemically deposited cadmium zinc sulfide (CdZnS) films were investigated. X-ray diffraction (XRD) results showed that the grown CdZnS thin films formed were polycrystalline with hexagonal structure. Atomic force microscopy (AFM) studies showed that the surface roughness of the CdZnS thin films was about 60-400 nm. Grain sizes of the CdZnS thin films varied between 70 and 300 nm as a function of annealing temperature. The root mean square surface roughness of the selected area, particular point, average roughness profile, topographical area of roughness were measured using the reported AFM software. The band gaps of CdZnS thin films were determined from absorbance measurements in the visible range as 300 nm and 1100 nm, respectively, using Tauc theory.     

溶胶-凝胶法制备氧化锌薄膜的压电行为

"采用溶胶-凝胶技术在单晶硅Si(111)上制备了ZnO压电薄膜,并以扫描电镜、X射线衍射仪(XRD)和原子力显微镜(AFM)进行了表征．XRD衍射实验表明ZnO薄膜随着膜厚的增大,其(002)取向逐渐增强;AFM研究了薄膜的表面形貌、粗糙度与晶粒大小的结果表明,ZnO压电薄膜的粗糙度与晶粒寸随着薄膜厚度的增大而减小．粗糙度为2.188~0.914 nm．利用PFM研究压电系数,发现随着薄膜厚度的增加,(002)生长方向增强,压电系数逐渐增大;当力参数小于薄膜的表面粗糙度时,压电系数测量不准确且在较大幅度     

Gradients of topographical structure in thin polymer films

We report the fabrication of centimeter-long gradients of topography. Structured polymer thin films were made by spin-coating an immiscible poly(methyl methacrylate)/poly(2-vinylpyridine) (PMMA/P2VP) blend from a common solvent on a substrate presenting a surface-energy gradient. Due to the interplay between polymer-wetting of the substrate and polymer phase-separation, different morphologies were observed along the sample. Atomic force microscopy (AFM) revealed a gradual transition from a flat to a structured morphology as the surface energy of the substrate was reduced. The transition occurred for a well-defined range of surface energies. A selective solvent was used to remove one of the polymer phases, increasing the topographical contrast and providing insight into the different stages of the transition. Image analysis allowed a quantitative characterization of the structure gradient.     

不同衬底温度下PLD法制备的氧化锌薄膜的特性

利用GCR-170型脉冲激光器Nd:YAG的三次谐波(355nm),以蓝宝石Al2O3(0001)为衬底,在不同温度下采用脉冲激光沉积法制备了ZnO薄膜.通过原子力显微镜、Raman谱、光致发光谱、红外透射谱、霍尔效应和表面粗糙度分析仪对制备的ZnO薄膜进行了测试.分析了在不同衬底温度下薄膜的表面形貌、光学特性,同时进行了薄膜结构和厚度的测试.研究表明:衬底温度对ZnO薄膜的表面形貌、光学特性、结构特性都是重要的工艺参量,尤其在500℃时沉积的ZnO薄膜致密均匀,并表现出较强的紫外发射峰.     

Free surfaces cause reductions in the glass transition temperature of thin polystyrene films

The effect of free surfaces on the glass transition temperature (T(g)) of thin polystyrene films was studied. Measurements were performed on films (8 nm相似文献   

Effect of Polymer-Substrate Interactions on the Surface Morphology of Polymer Blend Thin Films: Comparison between Simulation and Experiment

Microphase and macrophase separation phenomena can simultaneously appear in ABA/C copolymer blend systems due to the immiscibility among monomers A, B, and C. In this work, the surface morphologies and compositions of ABA/C blend thin films confined between two walls, which were used to mimic SEBS/PMMA films, have been simulated by a lattice Monte Carlo (MC) method. The effect of the polymer-wall interaction on the surface morphologies and compositions of thin films was investigated as a function of blend composition and film thickness. It is shown that the simulated surface morphologies of thin films resulting from the macrophase separation between copolymer ABA and homopolymer C and the microphase separation between block A and block B in ABA copolymer are similar to the experimental surface morphology of SEBS/PMMA polymer blend films observed by atomic force microscope (AFM). The effect of substrate on the surface morphologies by MC simulation is qualitatively consistent with the experimental results. The composition profiles of thin films are given to characterize the micro- and macrophase separation in thin films. It is indicated that the surface energy of the substrate (substrate/air) plays a crucial role on the surface composition. For a fixed surface, the adsorptions of polymer on the substrate and film thickness are also important.     

用锌有机源和CO2/H2混合气源PECVD沉积ZnO薄膜

在等离子体作用下,以CO2/H2混合气为氧源,Zn(C2H5)2锌为锌源,在单晶硅上生长出高度择优取向的氧化锌薄膜。X射线衍射分析表明,薄膜为六方结构,c轴高度择优;原子力显微镜观察到晶粒是有规律地按六方排布,薄膜的表面粗糙度较小;从光致发光谱还发现在380 nm处有非常强的紫外峰。     

Surface plasmon–exciton transition in ultra-thin silver and silver iodide films

Silver thin films in the thickness range 2–10 nm produced by thermal evaporation onto glass substrates were systematically iodized and carefully characterized by X-ray diffraction, atomic force microscopy (AFM) and optical absorption spectroscopy. While the uniodized films are X-ray amorphous in keeping with their quasi-continuous nature and 2D islanded structure, briefly iodized films showed characteristic beta AgI structure. Most interestingly, AFM of Ag films revealed uniform triangle-shaped embryos whose shape does not change appreciably upon iodization. Optical absorption spectra of uniodized Ag films show intense surface plasmon resonance (SPR) features with maxima at 440, 484 and 498 nm for the films of thicknesses 2, 5 and 10 nm, respectively, with 5 nm films showing properties characteristic of optimally matched dielectric and electronic properties of the substrate and sample, respectively. Finally, an interesting and unique SPR–exciton phase transition is observed as the ultra-thin films are progressively iodized. These Ag and AgI films could be promising candidates for plasmonic and nanophotonic applications. PACS 78.66.-w; 73.20.Mf; 71.35.Cc; 42.70; 68.37.Ps; 42.82.-m     

Effects of oxygen pressures on pulsed laser deposition of ZnO films

Zinc oxide (ZnO) thin films on Si (1 1 1) substrates were deposited by pulsed laser ablation of ZnO target at different oxygen pressures. A pulsed Nd:YAG laser with wavelength of 1064 nm was used as laser source. The deposited thin films have been characterized by X-ray diffraction (XRD), Atomic force microscopy (AFM), and Raman spectroscopy. XRD measurements indicate that the ZnO thin films deposited at the oxygen pressure of 1.3 Pa have the best crystalline quality. AFM results show that the surface roughness of ZnO film increases with the increase of oxygen pressure. The Raman results indicate that oxygen ambient plays an important role in removing defects due to excess zinc.     

Laser-induced forward transfer technique for maskless patterning of amorphous V2O5 thin film

A laser-induced forward transfer technique has been applied for the maskless patterning of amorphous V₂O₅ thin films. A sheet beam of a frequency doubled (SHG) Q-switched Nd:YAG laser was irradiated on a transparent glass substrate (donor), the rear surface of which was pre-coated with a vacuum-deposited V₂O₅ 180 nm thick film was either in direct contact with a second glass substrate (receiver) or a 0.14 mm air-gap was maintained between the donor film and the receiving substrate. Clear, regular stripe pattern of the laser-induced transferred film was obtained on the receiver. The pattern was characterized using X-ray diffraction (XRD), optical absorption spectroscopy, scanning electron microscopy (SEM), energy dispersive analysis of X-ray (EDAX), atomic force microscopy (AFM), etc.     

Surface analytical studies of Ar-plasma etching of thin heptadecafluoro-1-decene plasma polymer films

An audio-frequency plasma polymerization set-up with a planar plasma source was used to deposit thin heptadecafluoro-1-decene (HDFD) plasma polymer films. The morphology and chemical structure of the films after deposition were compared with the state of the film after a subsequent Ar-plasma treatment by means of in situ Fourier transform infrared reflection absorbance spectroscopy (FT-IRRAS), X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and atomic force microscopy (AFM) as well as contact angle measurements. The results revealed the correlation of wettability of the model Teflon-like films with change of surface chemistry and surface topography as a result of Ar-plasma treatment.     

Reversible wettability of nanostructured ZnO thin films by sol-gel method

Nanostructured ZnO thin films were deposited on Si(1 1 1) and quartz substrate by sol-gel method. The thin films were annealed at 673 K, 873 K, and 1073 K for 60 min. Microstructure, surface topography, and water contact angle of the thin films have been measured by X-ray diffractometer, atomic force microscopy, and water contact angle apparatus. XRD results showed that the ZnO thin films are polycrystalline with hexagonal wurtzite structure. AFM studies revealed that rms roughness changes from 2.3 nm to 7.4 nm and the grain size grow up continuously with increasing annealing temperature. Wettability results indicated that hydrophobicity of the un-irradiated ZnO thin films enhances with annealing temperature increase. The hydrophobic ZnO surfaces could be reversibly switched to hydrophilic by alternation of UV illumination and dark storage (thermal treatment). By studying the magnitude and the contact angle reduction rate of the light-induced process, the contribution of surface roughness is discussed.