Surface morphology of PECVD fluorocarbon thin films from hexafluoropropylene oxide, 1,1,2,2‐tetrafluoroethane,and difluoromethane

Atomic force microscopy (AFM) measurements have been made on a series of fluorocarbon films deposited from pulsed plasmas of hexafluoropropylene oxide (HFPO), 1,1,2,2‐tetrafluoroethane (C₂H₂F₄), and difluoromethane (CH₂F₂). All of the films give images showing nodular growth (cauliflower‐like appearance), with the size and distribution of the nodules dependent on both the precursor, the degree of surface modification to which the growing film is exposed, and the substrate surface. Films deposited from C₂H₂F₄ showed clusters of smaller nodules around larger nodules, whereas films deposited from CH₂F₂ were characterized by a uniform distribution of smaller nodules, and films deposited from HFPO had the largest observed nodules. Movchan and Demchishin's structure zone model was applied to the observed films, which were all found to be zone 1 structures, indicating that film growth is dominated by shadowing effects. Increased substrate temperature and incident power per nm of film deposited results in decreased rms roughness, consistent with greater atomic mobility during deposition. Larger nodules in the fluorocarbon films developed on silicon wafer substrates than on rougher Al‐coated substrates. Advancing contact angles for all of the films were found to be higher than that of PTFE (108°), indicating both hydrophobic and rough surfaces. Specifically, contact angles of films deposited from HFPO were found to increase with pulse off‐time, the same trend observed for both the CF₂ fraction of the film and the rms roughness. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2439–2447, 1999     

Characteristics of nitrogen doped diamond-like carbon thin films grown by microwave surface-wave plasma CVD

Nitrogen doped diamond-like carbon (DLC:N) thin films were deposited on p-type silicon (p-Si) and quartz substrates by microwave (MW) surface-wave plasma (SWP) chemical vapor deposition (CVD) at low temperature (< 100 °C). For films deposition, argon (Ar: 200 sccm), acetylene (C₂H₂:10 sccm) and nitrogen (N: 5 sccm) were used as carrier, source and doping gases respectively. DLC:N thin films were deposited at 1000 W microwave power where as gas composition pressures were ranged from 110 Pa to 50 Pa. Analytical methods such as X-ray photoelectron spectroscopy (XPS), UV-visible spectroscopy, FTIR and Raman spectroscopy were employed to investigate the chemical, optical and structural properties of the DLC:N films respectively. The lowest optical gap of the film was found to be 1.6 eV at 50 Pa gas composition pressure.     

Direct synthesis and characterization of optically transparent conformal zinc oxide nanocrystalline thin films by rapid thermal plasma CVD

We report a rapid, self-catalyzed, solid precursor-based thermal plasma chemical vapor deposition process for depositing a conformal, nonporous, and optically transparent nanocrystalline ZnO thin film at 130 Torr (0.17 atm). Pure solid zinc is inductively heated and melted, followed by ionization by thermal induction argon/oxygen plasma to produce conformal, nonporous nanocrystalline ZnO films at a growth rate of up to 50 nm/min on amorphous and crystalline substrates including Si (100), fused quartz, glass, muscovite, c- and a-plane sapphire (Al2O3), gold, titanium, and polyimide. X-ray diffraction indicates the grains of as-deposited ZnO to be highly textured, with the fastest growth occurring along the c-axis. The individual grains are observed to be faceted by (103) planes which are the slowest growth planes. ZnO nanocrystalline films of nominal thicknesses of 200 nm are deposited at substrate temperatures of 330°C and 160°C on metal/ceramic substrates and polymer substrates, respectively. In addition, 20-nm- and 200-nm-thick films are also deposited on quartz substrates for optical characterization. At optical spectra above 375 nm, the measured optical transmittance of a 200-nm-thick ZnO film is greater than 80%, while that of a 20-nm-thick film is close to 100%. For a 200-nm-thick ZnO film with an average grain size of 100 nm, a four-point probe measurement shows electrical conductivity of up to 910 S/m. Annealing of 200-nm-thick ZnO films in 300 sccm pure argon at temperatures ranging from 750°C to 950°C (at homologous temperatures between 0.46 and 0.54) alters the textures and morphologies of the thin film. Based on scanning electron microscope images, higher annealing temperatures appear to restructure the ZnO nanocrystalline films to form nanorods of ZnO due to a combination of grain boundary diffusion and bulk diffusion.PACS: films and coatings, 81.15.-z; nanocrystalline materials, 81.07.Bc; II-VI semiconductors, 81.05.Dz.     

Synthesis and characterization of Teflon‐like macromolecular structures from dodecafluorocyclohexane and octadecafluorodecalin under RF‐cold‐plasma conditions

The chemical inertness, thermal stability, and low dielectric constant characteristics of polytetrafluoroethylene make this polymer very attractive for advanced technology applications. Current production technologies are not adequate for the deposition of often desired, thin‐layer Teflon coatings. In this article the synthesis and characterization of Teflon‐like macromolecular structures from dodecafluorocyclohexane and octadecafluorodecaline vapors under RF‐cold‐plasma conditions is discussed. It was demonstrated, based on high‐resolution ESCA, ATR‐FTIR, and LD‐FT‐ICR‐MS investigations, that the deposited Teflon‐like layers are built of CF, CF₂, CF₃, and ex situ origin C O groups with an over 60% fluorine content, and that they have a branched and/or crosslinked nature. These structures have a relatively high thermal stability (340°C) and are characterized by a low dielectric constant (2.1). Plasma‐enhanced coatings of Teflon‐like layers can be performed at room temperatures at large substrate areas. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1627–1639, 1999     

Annealing and ultraviolet treatment of plasma fluorocarbon films for enhanced cohesion and stability

Stents, commonly used for the treatment of cardiovascular diseases, are mainly made of 316L stainless steel. They are, however, prone to corrosion when they are in contact with human body fluid. To prevent this corrosion process and to ameliorate their patencies, in this study, we used a strategy to cover stent materials with a protective fluorocarbon layer deposited by plasma polymerization. In an approach to optimize its cohesion properties and stability, posttreatments, namely, thermal annealing and UV irradiation, were applied on the ultrathin fluorocarbon film. A combination of X‐ray photoelectron spectroscopy, polarized near‐edge X‐ray absorption fine‐structure spectroscopy, and time‐of‐flight secondary ion mass spectrometry demonstrated that UV treatment led to chain scission and film crosslinking and, in this way, decreased the amount and/or size of nanoscaled defects originally present in the films. Annealing on the other hand induced a film reorganization in favor of longer, well‐ordered fluorocarbon chains. However, a deformation process that was applied to study the film adhesion properties induced chain scissions with reorganization. Aging tests exhibited an oxidation of the top‐most layer for both the as‐deposited and posttreated samples. Finally, the film stability was improved after UV treatment for both the nondeformed and deformed samples. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of nitrogen incorporated diamond-like carbon thin films using microwave surface-wave plasma CVD

Nitrogenated diamond-like (DLC:N) carbon thin films have been deposited by microwave surface wave plasma chemical vapor deposition on silicon and quartz substrates, using argon gas, camphor dissolved in ethyl alcohol composition and nitrogen as plasma source. The deposited DLC:N films were characterized for their chemical, optical, structural and electrical properties through X-ray photoelectron spectroscopy, UV/VIS/NIR spectroscopy, Raman spectroscopy, atomic force microscope and current–voltage characteristics. Optical band gap decreased (2.7 to 2.4 eV) with increasing Ar gas flow rate. The photovoltaic measurements of DLC:N / p-Si structure show that the open-circuit voltage (V_oc) of 168.8 mV and a short-circuit current density (J_sc) of 8.4 μA/cm² under light illumination (AM 1.5 100 mW/cm²). The energy conversion efficiency and fill factor were found to be 3.4 × 10^{− 4}% and 0.238 respectively.     

Structural properties of amorphous carbon thin films deposited by LF (100 kHz), RF (13.56 MHz), and pulsed RF (13.56 MHz) plasma CVD

Amorphous carbon thin films were deposited by LF (100 kHz), RF (13.56 MHz), and pulsed RF (13.56 MHz) plasma CVD with DC self-bias voltage of?300 V and 50 mTorr on Si wafers at 15 ?C using a mixture of methane and hydrogen for comparing structural properties of the deposited films in an asymmetric plasma reactor. The surface morphologies of the deposited films were observed by Atomic force microscopy (AFM). The average roughness (Ra) analyzed by AFM data was 4.03, 1,84, 1.52 å at LF (100 kHz), RF (13.56 MHz), and pulsed RF (13.56 MHz) plasma, respectively. From these results, the films deposited by pulsed RF plasma have more smooth and dense surface compared with those deposited by LF (100 kHz), and RF (13.56 MHz) plasma. The ratios of I_D/I_G obtained from Raman data were 2.69, 0.76 and 0.44 at LF (100 kHz), RF (13.56 MHz), and pulsed RF (13.56 MHz) plasma, respectively. It is concluded that the film deposited by pulsed RF plasma has more diamond-like properties compared with that deposited by LF (100 kHz), and RF (13.56 MHz) plasma.     

Pulsed plasma deposition from 1,1,2,2‐tetrafluoroethane by electron cyclotron resonance and conventional plasma enhanced chemical vapor deposition

Pulsed electron cyclotron resonance (ECR) plasmas from 1,1,2,2‐C₂H₂F₄ are used to deposit fluorocarbon films. The deposited films have a F : C ratio of 1, with only slight variations in % CF_x as the deposition pressure is decreased. The optical emission (OES) spectra of the pulsed C₂H₂F₄ plasmas show high intensity peaks for H, C₂, and C₃, with lower intensity CF₂ and F peaks. The dominant OES peak shifts from H_α to C₂ when the pressure is reduced, most likely a result of the increased electron temperature at the lower pressure. Gas‐phase recombination reactions may be occurring between the OES sampling region and the deposition substrate (～ 8‐in. distance), producing fluorocarbon molecular deposition species, thus accounting for the high degree of fluorination in the deposited films. Parallel plate plasma deposited films from C₂H₂F₄ show less fluorination than their ECR counterparts, as well as vastly different OES spectra, with CF₂ peaks dominating the spectra versus H and C₂. The presence of ion bombardment in the parallel plate system tends to defluorinate the depositing films, and thus can account for the less fluorinated films deposited in the parallel plate versus ECR systems. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2084–2092, 2001     

The role of pressure on thin amorphous carbon films deposited using microwave surface wave plasma CVD

We report the effects of gas composition pressure (GCP) on the optical, structural and electrical properties of thin amorphous carbon (a-C) films grown on p-type silicon and quartz substrates by microwave surface wave plasma chemical vapor deposition (MW SWP CVD). The films, deposited at various GCPs ranging from 50 to 110 Pa, were studied by UV/VIS/NIR spectroscopy, atomic force microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and current–voltage characteristics. The optical band gap of the a-C film was tailored to a relatively high range, 2.3–2.6 eV by manipulating GCPs from 50 to 110 Pa. Also, spin density strongly depended on the band gap of the a-C films. Raman spectra showed qualitative structured changes due to sp³/sp² carbon bonding network. The surfaces of the films are found to be very smooth and uniform (RMS roughness < 0.5 nm). The photovoltaic measurements under light illumination (AM 1.5, 100 mW/cm²) show that short-circuit current density, open-circuit voltage, fill factor and photo-conversion efficiency of the film deposited at 50 Pa were 6.4 μA/cm², 126 mV, 0.164 and 1.4 × 10^− 4% respectively.     

Synthesis,characterization and nonlinear optical properties of plasma‐prepared poly(4‐biphenylcarbonitrile) thin films

A novel conjugated polymer, poly(4‐biphenylcarbonitrile) (PBPCN), was prepared using a plasma polymerization technique. The effect of the discharge power on the chemical structure and surface compositions of PBPCN thin films was investigated using Fourier transform infrared, UV‐visible absorption and X‐ray photoelectron spectroscopies. A femtosecond time‐resolved optical Kerr effect technique was applied to investigate the third‐order nonlinearity of the obtained plasma PBPCN thin films. For the first time, a non‐resonant optical Kerr effect and ultrafast response for the PBPCN thin films were observed. Copyright © 2006 Society of Chemical Industry     

Variable‐energy positron lifetime study of silicon‐oxide films plasma deposited from hexamethyldisiloxane and oxygen mixtures

Mixtures of hexamethyldisiloxane [HMDSiO, (CH₃)₃SiOSi(CH₃)₃] and oxygen are plasma polymerized at different oxygen pressures (P = 1.3–11.4 Pa) and a fixed monomer pressure (P_m = 2.6 Pa). The discharge power is kept at 100 W throughout the work. Nanometer‐size holes in the deposited films are characterized by variable‐energy positron annihilation lifetime spectroscopy (PALS). Additional information on the film composition and structure is obtained by X‐ray photoelectron spectroscopy and IR absorption spectroscopy. The ortho‐positronium lifetime τ₃ and intensity I₃ increase with the P up to 6.2 Pa and then decrease with the P. PALS measurements after annealing at 400°C show that films prepared at high oxygen pressure have a less stable structure than a film deposited at a lower oxygen pressure. These results are discussed in comparison with plasma deposition of pure HMDSiO, as are the possible effects of oxygen radicals on the film structure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 974–980, 2001     

远程等离子体处理对聚四氟乙烯表面的功能化改性

采用远程氩等离子体对聚四氟乙烯(PTFE)膜进行了表面改性研究,通过接触角测定仪、扫描电子显微镜(SEM)和X射线光电子能谱仪(XPS)等手段,分析研究了改性后材料表面结构、性能的变化。结果表明:PTFE表面经远程氩等离子体处理后,表面微观形态和表面化学成分均发生了变化,且处理效果优于常规氩等离子体。远程氩等离子体可以在一定程度上抑制电子、离子的刻蚀作用,强化自由基反应,使材料表面获得更好的改性效果。经远程氩等离子体短时间(100s)处理后,PTFE表面的F/C比例从1.97降至1.44,O/C比例从0.015增至0.086;表面的水接触角从108°减小到53°;表面自由能从22.4×10-5N·cm-1增加至52.3×10-5N·cm-1。     

XPS and IR analysis of thin barrier films polymerized from C2H4/CHF3 ECR-plasmas

Thin fluorocarbon polymer films are prepared on PE-foils in low-pressure electron cyclotron resonance plasmas using ethylene (C₂H₄) and trifluoromethane (CHF₃) as monomers. The thin fluorinated hydrocarbon layers strongly reduces the permeability of polyethylene to alkanes. For example, the permeation of toluene was decreased by a factor of about 100 by a single, thin fluorocarbon layer. A further reduction of the permeation down to a factor of 1600 can be obtained by a multilayer coating. X-ray photoelectron spectroscopy and Fourier transform IR spectroscopy are used to characterize the plasma polymerized films. It is shown that the addition of CHF₃ to a C₂H₄ plasma leads to an increase of CF₃—, CF₂—, and CF— groups and to a decrease of CH₃— and CH₂— groups in the film. The chemical composition of the polymer layers and their toluene permeabilities are discussed. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 717–722, 1997     

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     

Preparation and characterization of YAG:Ce thin phosphor films by pulsed laser deposition

We report the use of YAG:Ce phosphor as the raw material to make thin and transparent phosphor films with pulsed laser deposition including the effects of heating temperature, target–substrate distances, annealing times, and annealing atmosphere on the YAG:Ce³⁺ phosphor film crystal types and spectral properties. The results indicated that at a coating temperature of 350°C, the YAG:Ce³⁺ phosphor film had the best crystallinity with an intact film and maximum fluorescence emission. The crystallinity and fluorescence emission intensity of the film gradually decreased as a function of increasing target–substrate distances. As the annealing time increased, the crystallinity and the fluorescence emission intensity of the film first increased and then decreased. The film made with 5 h of annealing had the best crystallinity and the highest fluorescence emission intensity. The crystallinity of the film annealed under air was higher than that made under nitrogen; the fluorescence intensity of the film under air was slightly lower than the film under nitrogen. The emission peak of the prepared film was at 523 nm when excited at 450 nm. This is slightly blue‐shifted versus the emission of commercial phosphor powders. This study offers a theoretical basis for the development of transparent phosphor films.     

Preparation and characterization of nano‐SiO2 reinforced alginate‐based nanocomposite films (II)

Crosslinked alginate‐based nanocomposites at different SiO₂ contents were prepared successfully by blending the nano‐SiO₂ solution into low concentration alginate solution (0.5 wt %), with the alginate concentration increased step by step to the resulted concentration, in this course glycerol was used as plasticizer and 5 wt % CaCl₂ as crosslinker. The combined effect of SiO₂ content (1.5–8 wt %) on the microstructural, physical, mechanical, and optical properties of the nanocomposite films were investigated. The results showed that tensile strength and elongation was improved by about 40.33% and 89%, respectively, upon increasing the SiO₂ content to 4.5 wt %. In addition, water vapor permeability and swelling degree decreased by 19% and 16% with increasing SiO₂ content up to 8 and 4.5 wt %, respectively with respect to pure crosslinked alginate film. Thermogravimetric analysis also revealed that nano‐SiO₂ can improve the thermal stability of sodium alginate films produced by this method. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45286.     

Analysis of annealed thin polymer films prepared from dichloro(methyl)phenylsilane by plasma polymerization

Thin plasma polymer films were deposited from a mixture of dichloro(methyl)phenylsilane (DCMPS) vapor and gaseous hydrogen in an rf (13.56 MHz) capacitive coupling deposition system on pieces of silicon wafers. Some of samples were annealed in a vacuum to temperatures ranging from 450 to 700°C. The chemical composition, structure, and surface morphology of the annealed samples and those stored in air at room temperature were studied by FTIR, XPS, SEM, and optical microscopy. The thermal stability and decomposition of the plasma polymer with increasing temperature were characterized using thermogravimetry together with mass spectrometry. The plasma polymer was stable to a temperature of 300°C. Above that temperature, the material started to decompose together with additional crosslinking due to the incorporation of extra oxygen atoms forming new siloxane bonds. The plasma polymer was tough at room temperature but much more brittle after annealing. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2106–2112, 2001     

Investigation of plasma polymerized benzene and furan thin films for application in opto‐electronic devices

Conjugated polymers are among the most promising organic materials for opto‐electronic devices. In such applications, the main fabrication problem is to get uniform, defect‐free, and reproducible thin films of these materials. In this investigation, an RF plasma reactor was used to produce cross‐linked organic thin films from benzene and furan precursors. Uniform thin films of desired thickness were fabricated using this plasma polymerization technique. The composition of the plasma‐polymerized films was determined with X‐ray photoelectron spectroscopy. Fourier transform infrared spectra of the monomers and plasma‐polymerized thin films prepared were compared to analyze the chemical structure of the films. Ultraviolet–visible absorption spectroscopy shows a red shift of 45 nm in λ_max for the case of plasma‐polymerized benzene films and 52 nm in the case of plasma‐polymerized furan films when compared to their respective monomer spectra. Photo luminescence spectra of these films show a blue emission with a broad peak at 460 nm for the plasma‐polymerized benzene films and 445 nm for the plasma‐polymerized furan films. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 523–528, 2003     

New approach to chemical functionalization of poly(2‐chloroxylylene) thin films

3‐(8‐Octenyl)thiophene was used for successful preparation of functionalized poly‐(2‐chloro‐xylylene) (PCX) layers in the course of CVD process. The set of spectral methods used has allowed us to conclude that such modification is based on the chemical reaction of double bonds with xylylene radicals. Functionalized films were used for further chemical transformation in the course of polycondensation of 3‐octylthiophene. Resulted samples are bilayer films and polythiophene layer is chemically connected with PCX one. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Crystal behavior of semicrystalline polystyrene‐block‐poly(l‐lactide) diblock copolymer in thin films with various structures

The crystal behavior of a semicrystalline polystyrene‐block‐poly(l ‐lactide) diblock copolymer in phase‐separated thin films with various thicknesses at different crystal temperatures has been investigated using atomic force microscopy and transmission electronic microscopy. Parallel and perpendicular lamellae could be obtained by annealing the thin films for different periods of time as reported previously (Chen et al., Macromolecules 40:6631 (2007)). At different temperatures, crystallization in thin films with parallel lamellar structure in the melt state gives dendrite crystals with orthorhombic structure, and the ordered structure in the melt is destroyed after crystallization. When crystallization occurs in thin films with perpendicular lamellar structure, crystal morphology and structure are greatly affected by the crystallization temperature (T_c). When T_c < T_g,ps, where T_g,ps is the glass transition temperature of a polystyrene block, crystallization is hardly confined within the lamellae. The morphology is preserved but the long period of the perpendicular lamellae is increased after crystallization. When T_c > T_g,ps, rod‐like crystals dominate the final morphology, and crystallinity destroys completely the structure in the melt.© 2012 Society of Chemical Industry