Covalent Layer‐by‐Layer Assembly of Conjugated Polymers and CdSe Nanoparticles: Multilayer Structure and Photovoltaic Properties

Hybrid thin films of conjugated polymers and CdSe nanoparticles have been fabricated by using a layer‐by‐layer (LbL) approach driven by covalent coupling reactions. This method permits facile covalent crosslinking of the polymer/nanoparticle interlayers in common organic solvents, which provides a general route for preparing robust and uniform functional thin films. The deposition process is linearly related to the number of bilayers as monitored by UV‐vis absorption spectroscopy and ellipsometry. Characterization of the multilayer structures has been carried out by fluorescence spectroscopy, X‐ray photoelectron spectroscopy (XPS), and grazing‐angle Fourier‐transform infrared spectroscopy (FTIR). Techniques such as atomic force microscopy (AFM) and scanning electron microscopy (SEM) have also been used. A preliminary application of the hybrid films in the development of organic photovoltaics is presented. Upon illumination with white light at 10 mW cm^–2, the self‐assembled multilayer films exhibit steady photocurrent responses with an overall optical‐to‐electrical power conversion efficiency of 0.71 %.     

（英）离子束溅射法制备碳化锗薄膜的红外光学特性和力学特性

采用离子束溅射法通过在CH4和Ar 的混合气体中溅射Ge靶材制备碳化锗(Ge1-xCx)薄膜.分别通过原子力显微镜、拉曼光谱和X射线光电子能谱、傅里叶变换红外光谱以及纳米压痕测试研究了薄膜的表面形貌、化学结构、光学特性和力学特性.同时分析了制备薄膜时的离子源束压和薄膜性质之间的关系.结果表明,薄膜的粗糙度随束压的增大而减小.在较高束压下制备的薄膜含有较少的C元素和较多的Ge-C键.薄膜具有非常好的红外光学特性和力学特性.薄膜在较大波长范围内具有良好的透光性能.C元素含量随着束压的升高而降低,进而导致薄膜的折射率在束压从300 V增大到800 V的过程中逐渐升高.薄膜的硬度大于8 GPa.由于薄膜中的Ge-C键代替了C-C 键和C-Hn键,薄膜的硬度随束压的增加逐渐增加.     

Reactive Imprint Lithography: Combined Topographical Patterning and Chemical Surface Functionalization of Polystyrene‐block‐poly(tert‐butyl acrylate) Films

Here, reactive imprint lithography (RIL) is introduced as a new, one‐step lithographic tool for the fabrication of large‐area topographically patterned, chemically activated polymer platforms. Films of polystyrene‐block‐poly(tert‐butyl acrylate) (PS‐b‐PtBA) are imprinted with PDMS master stamps at temperatures above the corresponding glass transition and chemical deprotection temperatures to yield structured films with exposed carboxylic acid and anhydride groups. Faithful pattern transfer is confirmed by AFM analyses. Transmission‐mode FTIR spectra shows a conversion of over 95% of the tert‐butyl ester groups after RIL at 230 °C for 5 minutes and a significantly reduced conversion to anhydride compared to thermolysis of neat films with free surfaces in air or nitrogen. An enrichment of the surface layer in PS is detected by angle‐resolved X‐ray photoelectron spectroscopy (XPS). In order to demonstrate application potentials of the activated platforms, a 7 nm ± 1 nm thick NH₂‐terminated PEG layer (grafting density of 0.9 chains nm^?2) is covalently grafted to RIL‐activated substrates. This layer reduces the non‐specific adsorption (NSA) of bovine serum albumin by 95% to a residual mass coverage of 9.1 ± 2.9 ng cm^?2. As shown by these examples, RIL comprises an attractive complementary approach to produce bio‐reactive polymer surfaces with topographic patterns in a one‐step process.     

掺N类金刚石薄膜的制备及微观结构分析

采用直流磁控溅射法,在光学玻璃衬底上沉积类金刚石(DLC)和掺N类金刚石薄膜(DLC:N)。用喇曼光谱、X射线光电子能谱(XPS)、傅里叶红外光谱(FTIR)等研究分析了所制备薄膜的微观结构。喇曼光谱的结果表明,掺N类金刚石膜仍具有典型的类金刚石膜结构,在类金刚石薄膜中掺N不仅有助于提高膜中sp3/sp2的比例,而且还能阻止sp2键向石墨相的转化,稳定并优化薄膜的类金刚石属性。FTIR表明,薄膜中N与C原子形成了C—N、CN及C≡N等键合方式。XPS谱表明,掺N类金刚石膜中除了C和N元素外,还出现了少量的O元素,而C1s和N1s的解谱显示,掺N后的类金刚石膜中的C、N结合能发生了明显的移动,由计算得出薄膜中N的含量为13.5%。薄膜的表面形貌图(AFM)表明,在类金刚石薄膜中掺N能够改善其表面形貌。     

Contact Angle Analysis During the Electro‐oxidation of Self‐Assembled Monolayers Formed by n‐Octadecyltrichlorosilane

The electrochemical oxidation process of self‐assembled monolayers formed by n‐octadecyltrichlorosilane (OTS) molecules on silicon wafers has been studied in a droplet of water by means of in situ water contact angle measurements. The application of different bias voltages between the substrate and a counter electrode placed into the droplet resulted in changes of the chemical nature of the monolayer, which yielded a significant alteration of the surfaces properties. Due to the changes of the wetting properties of the monolayer during the electro‐oxidation process a change in the contact angles of the water droplet is concomitantly observed. This allows the in situ monitoring of the electro‐oxidation process for large modified areas of several millimeters in diameter. The chosen approach represents an easy way to screen the major parameters that influence the oxidation process. Afterwards, the oxidized regions are characterized by Fourier‐transform infrared (FT‐IR) spectroscopy, X‐ray photoelectron spectroscopy (XPS) measurements, and atomic force microscopy (AFM) investigations to obtain more information about the electro‐oxidation process. The observations are correlated to experimental results obtained for oxidations performed on a smaller dimension range in the water meniscus of a conductive, biased AFM tip. A good correlation of the results in the different dimension ranges could be found.     

Spin-Crossover Grafted Monolayer of a Co(II) Terpyridine Derivative Functionalized with Carboxylic Acid Groups

The synthesis and characterization of a new Co(II) spin-crossover (SCO) complex based on 4′-(4-carboxyphenyl)−2,2′:6′,2″-terpyridine ligand are reported. This complex can be successfully grafted on silver surface maintaining the SCO behavior. Thus, atomic force microscopy (AFM), matrix assisted laser desorption ionization – time-of-flight mass spectrometry (MALDI-TOF MS), Raman spectroscopy, and XPS measurements, upon surface deposition, evidence the formation of a monolayer of intact molecules grafted through carboxylate groups to the Ag surface. Three different techniques: Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS), supported by first-principles calculations, confirm that the deposited molecules undergo a gradual spin transition with temperature. This phenomenon is unprecedented for a monolayer of molecules directly grafted onto a metallic surface from solution.     

Structural and Electrical Characterization of ZnO Films Grown by Spray Pyrolysis and Their Application in Thin‐Film Transistors

The role of the substrate temperature on the structural, optical, and electronic properties of ZnO thin films deposited by spray pyrolysis using a zinc acetate precursor solution is reported. Analysis of the precursor compound using thermogravimentry and differential scanning calorimetry indicates complete decomposition of the precursor at around 350 °C. Film characterization using Fourier Transform Infrared Spectroscopy (FTIR), photoluminescence spectroscopy (PL), and ultraviolet–visible (UV–Vis) optical transmission spectroscopy suggests the onset of ZnO growth at temperatures as low as 100 °C as well as the transformation to a polycrystalline phase at deposition temperatures >200 °C. Atomic force microscopy (AFM) and X‐ray diffraction (XRD) reveal that as‐deposited films exhibit low surface roughness (rms ≈ 2.9 nm at 500 °C) and a crystal size that is monotonously increasing from 8 to 32 nm for deposition temperatures in the range of 200–500 °C. The latter appears to have a direct impact on the field‐effect electron mobility, which is found to increase with increasing ZnO crystal size. The maximum mobility and current on/off ratio is obtained from thin‐film transistors fabricated using ZnO films deposited at >400 °C yielding values on the order of 25 cm² V^?1s^?1 and 10⁶, respectively.     

Effect of substrate biasing and temperature on AlN thin film deposited by cathodic arc ion

Aluminum nitride (AlN) films have been grown in pure N₂ plasma using cathodic arc ion deposition process. The films were prepared at different substrate bias voltages and temperatures. The aim was to investigate their influence on the Al macro-particles, structural and optical properties of deposited films. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Scanning electron microscope (SEM) and Rutherford backscattering spectrometry (RBS) were employed to characterize AlN thin films. XRD patterns indicated the formation of polycrystalline (hexagonal) films with preferential orientation of (002), which is suppressed at higher substrate bias voltage. FTIR and Raman spectroscopic analysis were used to assess the nature of chemical bonding and vibrational phonon modes of AlN thin films respectively. FTIR spectra depicted a dominant peak around 850 cm^?1 corresponding to the longitudinal optical (LO) mode of vibration. A shift in this LO mode peak towards higher wavenumbers was observed with the increase of substrate bias voltage and temperature, showing the upsurge of nitrogen concentration in the deposited film. Raman spectra illustrated a peak at 650 cm^?1 corresponding to E₂ (high) phonon mode depicting the c-axis oriented (perpendicular to substrate) AlN film. SEM analysis showed the AlN film deposited at higher substrate bias voltage contains fewer amounts of Al macro-particles.     

Characteristics of Amorphous Silicon Nitride Films Deposited by LF-PECVD from SiH_4/N_2

Amorphous silicon nitride films were deposited by low-frequency plasma-enhanced chemical vapor deposition(LF-PECVD) using silane and nitrogen as precursors. Characteristics such as deposition rate, surface morphology, and chemical composition were measured by spectroscopic ellipsometry(SE), atomic force microscope(AFM) and x-ray photoelectron spectroscopy(XPS). It was shown that amorphous silicon nitride film could be prepared by LF-PECVD with good uniformity and even surface. The XPS result indicated that ...     

微测热辐射计氧化钒薄膜工艺研究

用射频磁控反应溅射在石英玻璃和硅片上沉积氧化钒薄膜 .利用X射线衍射 ,X射线光电子谱 ,原子力显微镜 ,分光光度计和电阻测量手段对沉积薄膜结构、形貌和性能进行了测试 .结果表明 ,沉积薄膜的电阻温度系数大于 1.8% /℃ ,方块电阻为 2 2± 5kΩ/□ .     

Electropolymerized Self‐Assembled Monolayers of a 3,4‐Ethylenedioxythiophene‐Thiophene Hybrid System

Self‐assembled monolayers (SAMs) of a conjugated bithiophenic system connected to an alkanethiol chain have been deposited on gold surface. The electroactive bithiophenic system involves a 3,4‐ethylenedioxythiophene (EDOT) unit and a thiophene ring on which an alkanethiol is attached at the internal β‐position via a sulfide linkage. The analysis of the structure of the SAMs by IR spectroscopy, ellipsometry, contact angle measurement and X‐ray photoelectron spectroscopy (XPS) provides consistent results indicating compact monolayers in which the alkyl linkers are arranged in an almost vertical fashion while the bithiophenic‐conjugated systems are essentially parallel to the surface. Cyclic voltammetry shows that application of a few potential scans to SAMs immersed in a medium containing only a supporting electrolyte leads to the typical electropolymerization curves while the CV of the electrooxized monolayer exhibits a reversible cyclic voltammogram characteristic of a stable electroactive extended conjugated system. The characterization of the electropolymerized monolayers by IR spectroscopy, ellipsometry, contact angle measurement, and XPS indicates compact monolayers. The analysis of the current voltage characteristics of the monolayers by conducting AFM before and after electrooxidation shows that the enhancement of the effective conjugation resulting from electropolymerization leads to a significant increase of the transport properties.     

Facile Preparation of a Patterned,Aminated Polymer Surface by UV‐Light‐Induced Surface Aminolysis

Introducing amine functional groups on polymer surfaces is extremely important for studying various processes that involve polymer surfaces. We report a novel and extremely simple method for preparing a tertiary‐amine‐terminated poly(ethylene terephthalate) (PET) surface by using a UV‐light‐induced surface aminolysis reaction. X‐ray photoelectron spectroscopy and attenuated total‐reflection infrared spectroscopy give direct evidence of the incorporation of tertiary amine functionalities and the possible reaction mechanism behind this technique. Tertiary amines are easily protonated, so we have developed an extremely simple method for immobilizing and patterning biomolecules on a soft surface by the electrostatic self‐assembly of proteins, such as immunoglobulin (IgG) and horseradish peroxide (HRP), onto a patterned, aminated surface. An enzyme–substrate reaction, which is followed optically by observing the resulting precipitation on the surface, is used to reveal the patterned immobilization of HRP, where 3‐amino‐9‐ethylcarbazole, as a substrate for HRP, is deposited on the aminated surface after HRP adsorption. Fluorescein isothiocyanate‐labeled IgG (FITC‐IgG) has been immobilized electrostatically onto the ordered aminated spots, and the fluorescence intensity ratio of the IgG‐immobilized region (inside the spot) to the background (outside the spot) is about 5:1, as calculated from a fluorescence image and fluorescence spectra obtained by microlaser confocal Raman spectroscopy. We have found that the background intensity is mainly caused by the autofluorescence of virgin PET, and after subtracting this value from the measured intensity inside and outside the spot, respectively, a much higher intensity ratio between the spot and the background is obtained (about 22:1). The patterned immobilization of FITC‐IgG has been further proven by examining the change in intensity inside the spot after photobleaching the fluorophore.     

Facile and rapid production of conductive flexible films by deposition of polythiophene nanoparticles on transparent poly(ethyleneterephthalate): Electrical and morphological properties

In this work, polythiophene (PTh) nanoparticles were successfully deposited on poly(ethyleneterephthalate) (PET) substrate as thin film by a facile and rapid chemical oxidative deposition method using a binary organic solvent system in the presence of N-cetyl-N,N,N-trimethylammonium bromide (CTAB) as cationic surfactant. The electrical conductivity of PTh nanoparticles deposited on PET was optimized by adjusting the surfactant/oxidant/monomer molar ratio, monomer concentration and time of polymerization. Resulted film was conductive, transparent and flexible which can be used in electronic devices such as OLEDs. Electrical conductivity for the un-doped deposited PTh nanoparticles at oxidant/monomer molar ratio of 5:1 at 0 °C polymerized for 12 min was measured to be 1.18×10⁻² S/cm. The effect of oxidant and monomer concentration on polymerization yield was also investigated. The structural confirmation and transparency of the PTh nanoparticle coated PET films were characterized by FTIR and UV–vis spectroscopy, respectively. Field emission scanning electron microscopy (FESEM), laser particle size analysis and transmission electron microscopy (TEM) were employed for surface morphology and size distribution measurements of PTh nanoparticles. The results showed that the PTh nanoparticles are deposited as globular aggregates with average size of about 50 nm on PET.     

Capillary Force Lithography: Fabrication of Functional Polymer Templates as Versatile Tools for Nanolithography

The implementation of high‐resolution polymer templates fabricated by capillary force lithography (CFL) is explored both in nanoimprint lithography (NIL) and in the wet‐etching of metals. Several different thermoplastic and UV‐curable polymers and types of substrates are incorporated into the general CFL procedure to meet the diverging requirements of these two applications. The mechanical stability of UV‐curable templates for imprinting in polymers, as examined by atomic force microscopy (AFM), and their anti‐adhesive properties are excellent for application in NIL. The conditions for curing the UV‐curable polymer are optimized in order to obtain high‐stability polymer templates. Gold patterns on silicon with a lateral resolution of 150 nm are fabricated by subsequent lift‐off in acetone. Similar patterns with a lateral resolution of 100 nm are fabricated using templates of thermoplastic polymers on gold layers on silicon as an etch mask. The transfer of stamp residues during CFL with these polymer templates is proven by X‐ray photoelectron spectroscopy (XPS) and AFM friction analysis. For poly(methylmethacrylate) (PMMA), the presence of large amounts of silicon‐containing residues is found to compromise the processability of the resulting template in subsequent O₂ reactive‐ion etching (RIE) treatment. The extent of silicon contamination is up to six times less for polystyrene (PS). At this level, the etch performance of the PS etch mask is not affected, as was the case for PMMA. Accurate downscaling of the lateral dimensions of the resulting metal patterns by several factors with respect to the dimensions of the PS etch mask is achieved by over‐etching of the gold. Overall, the results in this paper demonstrate the potential of CFL templates as tools for high‐resolution soft lithography.     

Vertical Phase Separation in Poly(3‐hexylthiophene): Fullerene Derivative Blends and its Advantage for Inverted Structure Solar Cells

A method which enables the investigation of the buried interfaces without altering the properties of the polymer films is used to study vertical phase separation of spin‐coated poly(3‐hexylthiophene) (P3HT):fullerene derivative blends. X‐ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) analysis reveals the P3HT enrichment at the free (air) surfaces and abundance of fullerene derivatives at the organic/substrate interfaces. The vertical phase separation is attributed to the surface energy difference of the components and their interactions with the substrates. This inhomogeneous distribution of the donor and acceptor components significantly affects photovoltaic device performance and makes the inverted device structure a promising choice.     

Thermal and electroless deposition of copper on poly(tetrafluoroethylene-co-hexafluoropropylene) films modified by surface graft copolymerization

Surface modification of Ar plasma-pretreated poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) film via UV-induced graft copolymerization, under atmospheric conditions, with 4-vinylpyridine (4VP), 2-vinylpyridine (2VP) and 1-vinylimidazole (VIDz) was carried out to improve the adhesion with the thermally evaporated and the electrolessly deposited copper. The surface composition and structure of the graft-copolymerized FEP films were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM), respectively. The electroless plating of copper on the graft-copolymerized FEP film could be carried out in the absence of sensitization by SnCl/sub 2/ (the Sn-free activation process). The adhesion strength of the thermally evaporated and the electrolessly deposited copper on the FEP surfaces was affected by the type of monomers used for graft copolymerization and the surface graft concentration. The T-peel adhesion strengths of the electrolessly deposited copper on the 4VP, 2VP and VIDz graft-copolymerized FEP films with 90-s of Ar plasma pretreatment were about 9.8 N/cm, 7.3 N/cm and 4.9 N/cm, respectively.     

RF磁控溅射功率对ZnO:Al薄膜结构和性能的影响

采用RF磁控溅射技术以ZnO:Al2O3(2 wt%Al2O3)为靶材在石英玻璃衬底上制备多晶ZnO:Al(AZO)薄膜,通过XRD、AFM、AES以及Hall效应、透射光谱、折射率等手段研究了RF溅射功率(50～300 W)对薄膜的组织结构和电学,光学性能的影响.分析表明:所制备的AZO薄膜具有c轴择优取向,并且通过对不同功率下薄膜载流子浓度与迁移率的研究发现对于室温下沉积的AZO薄膜,晶粒间界中的O原子吸附是影响薄膜电学性能的主要因素.同时发现当功率为250 W时薄膜的电阻率降至最低(3.995×10-3 Ω·cm),可见光区平均透射率为91%.     

Ar等离子体处理PET在非晶硅太阳电池中的应用

在射频等离子体增强化学气相沉积(RF-PECVD)系统的腔室内,对聚对苯二甲酸乙二醇酯(PET)塑料薄膜进行Ar等离子体预处理,并采用光发射谱(OES)对不同处理参数下的氩气辉光状态进行在线监测。对处理前后PET及PET/ITO进行透过谱、原子力显微镜(AFM)以及扫描电镜(SEM)的测试结果表明,Ar等离子体处理改善了PET塑料薄膜的表面形貌,使之更适合ITO薄膜的生长。以Ar等离子体处理的PET/ITO为衬底,在沉积温度为125℃条件下,制备出效率为5.4%的p-i-n型非晶硅(a-Si)柔性太阳电池。     

在Si(111)上磁控溅射碳化硅薄膜的H2退火效应

用射频磁控溅射法在常温硅衬底上制备了碳化硅薄膜并研究了氢退火对薄膜的影响.用傅里叶红外透射谱(FTIR)、X射线衍射(XRD)、X光电子能谱(XPS)、扫描电镜(SEM)及原子力显微镜(AFM)对薄膜样品进行了结构、组分和形貌分析.结果表明:高温退火后SiC膜的晶化程度明显提高,而且在薄膜中观察到了碳纳米线的形成.     

SiH_4-NH_3-N_2体系LPCVD氮化硅薄膜的研究

通过傅立叶红外光谱(FTIR)和X光电子能谱(XPS)研究了SiH4-NH3-N2体系在不同气体原料比情况下,低压化学气相沉积(LPCVD)SiNx薄膜的化学组成,利用原子力显微镜观察了SiNx薄膜的微观形貌,借助椭圆偏振仪研究了薄膜的折射率。结果表明:当原料气中氨气与硅烷的流量之比(R)较小时(R<2),获得富Si的SiNx薄膜(x<1.33),折射率较高。当氨气远远过量时(R >4),获得近化学计量的的SiNx薄膜(x = 1.33),折射率处于1.95~2.00之间。在适当的工艺条件下,获得的SiNx薄膜H、O含量很低,薄膜表面均匀、平整。