Adhesion Promotion Layer Research Articles

Study of SU‐8 to make a Ni master‐mold: Adhesion, sidewall profile, and removal

For disposable microfluidic devices, easy and inexpensive fabrication is essential. Consequently, replication of microfluidic devices, using injection molding or hot embossing, from a master-mold is widely used. However, the conventional master-mold fabrication technique is unsatisfactory in terms of time and costs. In this regard, direct Ni growth (electroplating) from a back plate is promising when the photoresist is well-defined. Here, we demonstrate the use of SU-8 as a photoresist to define the Ni-growth region. We accomplish this application by focusing on the adhesion, the sidewall profile, and the removal of SU-8: the adhesion is enhanced by controlling the exposure dose, the soft-baking time, and by choosing the adhesion-promoting layer; the sidewall profile is regulated by selecting the intensity of each exposed wavelength, showing an aspect ratio of up to 20.9; and, easy removal is achieved by choosing a proper photoresist-stripper. Using the master-mold fabricated by this method, we test the mechanical stability of the features according to the aspect ratio and length; in the hot embossing process, the features are stable in the aspect ratio of up to 5.8 at a length of 200 microm. In addition, the plastic devices fabricated from this method are applied to the passive stop valves, showing a capillary pressure (-0.2 to -7.2 kPa).

Effect of porosity and adhesion promoter layer on adhesion energy of nanoporous inorganic low- κ

A four-point bend technique (4PBT) was employed to characterize adhesion strength of nanoporous silica (SiCOH-based low- κ) to a hard mask layer (TEOS). Adhesion energy was analyzed as a function of low- κ porogen loading (3, 6, 9, and 11%). Effect of an adhesion promoter (AP) layer would also be discussed. Low fracture energies (< 5 J/m 2) confirm the weak mechanical properties of such highly porous materials. Fracture energy decreases as the porosity increases for samples without AP. However it becomes slightly higher and independent on the porosity when AP is applied. Low- κ/TEOS interface is the main delamination path for samples without AP. On the other hand, AP/TEOS interface becomes the interface that controls the adhesion for samples with AP hence it becomes independent on the low- κ porosity.

Plasma Graft Copolymerization of 4-Vinylpyridine on Dense and Porous SiLK for Electroless Plating of Copper and for Retardation of Copper Diffusion

Argon plasma-pretreated dense and porous SiLK films coated on Si(100) wafers (Si-SiLK wafers) were subjected to plasma graft polymerization of 4-vinylpyridine (4VP). X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy results revealed that the pyridine functional groups of the plasma graft-polymerized 4VP (pp4VP) could be retained to a large extent under certain grow discharge conditions. The topography of the pp4VP grafted Si-SiLK (Si-SiLK--pp4VP) surface was studied by atomic force microscopy. The preserved pyridine groups were used as the chemisorption sites for the palladium complexes (without prior sensitization by ) to catalyze the electroless deposition of copper. Rutherford backscattering spectrometry and transmission electron microscopy were employed to investigate the extent of copper diffusion into the pristine and graft-modified Si-SiLK substrates after thermal annealing. The grafted pp4VP layer on the dense and porous Si-SiLK surface served effectively as (i) a sensitization layer for the electroless plating of copper, (ii) an adhesion promotion layer for the electrolessly deposited copper, and (iii) a diffusion barrier for the electrolessly deposited copper. These functionalities arose from strong interactions of the metal ions and atoms with the pyridine moieties of the grafted pp4VP layer.

Adhesion of metals to plasma-induced functional groups at polymer surfaces

The peel strength of aluminium to polypropylene and poly(tetrafluoroethylene) was determined in dependence on the type and the concentration of functional groups on the polymer surface. For this purpose the polymer surface was equipped with monotype functional groups. The first method to produce monotype functionalized surfaces was an introduction of O functional groups using an oxygen plasma treatment and converting these groups to OH groups applying a wet chemical reduction. In result of this two-step treatment the hydroxyl group concentration at the polymer surface could be increased from 3–4 to 10–14 OH groups/100 C atoms. The second method consists in the deposition of a 150 nm adhesion-promoting layer of plasmapolymers or copolymers onto the polymer surface using the pulsed plasma technique. For that purpose functional groups carrying monomers as allyl alcohol, allylamine and acrylic acid were used. Applying the plasma-initiated copolymerization and using neutral “monomers” like ethylene or butadiene the concentration of the functional groups was varied.A correlation of peel strength with the ability of forming chemical interactions between Al atoms and functional groups was found: COOH>OH>>NH2>H(CH2–CH2).

Improvement of capacity and cyclability of Fe/Si multilayer thin film anodes for lithium rechargeable batteries

The multilayer films consisting of active (Si) and inactive (Fe) metal elements were investigated as anodes for lithium rechargeable batteries. It has been revealed that the electrochemical performance of as-deposited Fe/Si multilayer films could be improved and optimized by controlling the multilayer structure like the thickness and number of stacked layers as well as post-annealing treatment. It appears that the adhesion between Si film and current collecting substrate is critical for attaining a prolonged cycling stability, which can be effectively achieved by insertion of an adhesion-promoting layer selected based on the chemical affinity between the constituent elements at a given interface. Fe/Si multilayer film electrodes have shown acceptable electrochemical properties as an anode material.

Large-Area Patterning of Coinage-Metal Thin Films Using Decal Transfer Lithography

We describe two new procedures that appear to hold significant promise as means for patterning thin-film microstructures of the coinage metals (Cu, Ag, Au). A feature central to both is the modification of their surfaces to promote the adhesive transfer of PDMS thin-film microstructures, a material suitable for use as resist layers in large-area patterning, using Decal Transfer Lithography (DTL). The present work provides a significant extension of the capabilities of DTL patterning, providing general protocols that can be used to transfer decal resists to essentially any substrate surface. The first method involves the functionalization of a surface, specifically those of gold and silver films with a thiol-terminated silane coupling agent, (mercaptopropyl)trimethoxysilane. This self-assembled monolayer, when hydrolyzed to its silanol form, provides a robust adhesion-promoting layer suitable for use in DTL patterning. The second method exploits the surface chemistry provided by the deposition of a nanoscale silicon dioxide thin-film capping layer using e-beam evaporation. This procedure provides an exceptional method for patterning large-area, thin-film microstructures of Cu-one compatible with micrometer-scale design rules-that are essentially defect free. Both surface modification strategies enable high-quality poly(dimethylsiloxane) decal transfers, and as the current work shows, these structures are suitable for large-area micrometer-sized patterning of gold, silver, and copper thin films via both wet-etching and lift-off procedures.

Reactive Coupling of 4-Vinylaniline with Hydrogen-Terminated Si(100) Surfaces for Electroless Metal and “Synthetic Metal” Deposition

Pristine and resist-patterned Si(100) substrates were etched by aqueous HF to produce hydrogen-terminated silicon (H-Si(100)) surfaces. The H-Si(100) surface was then subjected to UV-induced reactive coupling of 4-vinylaniline (VAn) to produce the VAn monolayer-modified silicon (VAn-Si) surface. The VAn-Si surface was first functionalized with a "synthetic metal" by oxidative graft polymerization of aniline with the aniline moieties of the coupled VAn molecules. The composition and topography of the VAn-Si and polyaniline (PAn)-grafted VAn-Si (PAn-VAn-Si) surfaces were characterized by X-ray photoelectron spectroscopy and atomic force microscopy, respectively. The doping-undoping (protonation-deprotonation) and redox-coupling (metal reduction) behavior, as well as the electrical conductivity, of the surface-grafted PAn were found to be similar to those of the aniline homopolymer. The VAn-Si surface was also funtionalized by the electroless plating of copper. Not only did the VAn layer provide chemisorption sites for the palladium catalyst, in the absence of prior sensitization by SnCl2, during the electroless plating process, it also served as an adhesion promotion layer and a low-temperature diffusion barrier for the electrolessly deposited copper. Finally, micropatterning of the grafted PAn and of the electrolessly deposited copper were demonstrated on the resist-patterned VAn-Si surfaces.

Adhesion, Permeability, and Mechanical Properties of Multilayered Blown Films Using Maleated Low-Density Polyethylene Blends as Adhesion-Promoting Layers

W eh av ef abricated three-layer films, comprising a varying content of ethylene-vinyl alcohol copoly- mer (EVOH) as the internal layer and blends of low-density polyethylene (LDPE) and low-density ethylene grafted with maleic anhydride (LDPE-g-MAH) as the external layers, by ac oextrusion blown-film process. We chose to use blends to promote the adhesion between EVOH and LDPE and to reduce the number of layers in the coextrusion system. The peel strength increased sharply when the amount of LDPE-g-MAH was greater than 12.5 wt% and we associate it with the promotion of adhesion between layers brought about by specific interactions between EVOH and LDPE- g-MAH. FT-IR spectroscopic analysis showed an increase in the intensity of the absorbance of the ester band upon increasing the content of LDPE-g-MAH, which indicates that a chemical reaction occurs that promotes adhesion at the interface. The tensile strength did not change significantly with increasing LDPE- g-MAH content, which had a small effect on elongation and modulus in both the machine direction (MD) and transverse direction (TD). Tear strength decreased continuously with in- creasing LDPE-g-MAH content, in both the MD and TD, as a result of the greater ease of crack propagation in the EVOH layer. The oxygen permeability of the three-layer films remained alm ost constant upon varying the amount of LDPE-g- MAH. These three-layer fi lms all followed the theoretical prediction made by the inverse additivity rule. The water vapor permeabilitie so ft he three-layer films, however, were affected by the degree of hydrogen bonding, which was analyzed by FT-IR spectroscopy. The effects of this hydrogen bonding resulted in a discrepancy between the experimental findings and the theoretical predictions, especially when the EVOH content was increased. Coextrusion is a process in which two or more poly- mers are extruded simultaneously and joined together to form a single structure having different properties in each layer and to achieve a broad range of properties that are not available in any of the individual materi- als alone. In recent years, the packaging and container industries have paid increasing attention to the devel- opment of new or improved products formed by coex- trusion, such as multilayer sheets, multilayer films, and

High density nanostructure transfer in soft molding using polyurethane acrylatemolds and polyelectrolyte multilayers

Here we present an alternative, new, unconventional lithographic technique developedto create dense and multilevel nanostructure pattern transfer using a highly accuratepolyurethane acrylate (PU, MINS101m, Minuta Tech.) mold and a polyelectrolytemultilayer as the adhesion promotion layer. Specifically, we demonstrate the patterntransfer of periodic 80 nm lines with 400 nm height and complex and multilevelnanostructures to a polymer layer on various substrates, such as Si or SiO2wafers, glass and flexible polymer films. This new, unconventional lithographictechnique presented here would open the door to a variety of applications in thefields of electronic, optical and biological devices.

Removal of Resist Materials Using Acetic Acid

Polymer film removal from silicon surfaces was investigated using acetic acid at low temperatures. The polymer materials studied included poly(methyl methacrylate), poly(4-hydroxystyrene), and commercial positive photoresist (Shipley 1813). All polymer films studied were removed by acetic acid at 35°C, apparently by dissolution and in some cases, lift-off from the polymer-silicon interface. If an adhesion-promoting layer such as hexamethyldisilazane was applied to the silicon surface prior to polymer application, a thin carbon-based residue remained on the silicon surface as detected by X-ray photoelectron spectroscopy. A proposed solubility removal mechanism was investigated by using propionic and trifluoroacetic acids, since these acids possess different solubility and reactivity properties than acetic acid. Acetic acid was the most efficient for polymer removal and was capable of removing and ion-implanted photoresist. © 2003 The Electrochemical Society. All rights reserved.

Electroless Plating of Copper on Fluorinated Polyimide Films Modified by Plasma Graft Copolymerization and UV‐induced Graft Copolymerization with 4‐Vinylpyridine

AbstractSurface modification of two types of fluorinated polyimide (FPI) films, either by plasma polymerization and deposition of 4‐vinylpyridine (4VP) or by UV‐induced graft copolymerization with 4VP under atmospheric conditions, was carried out for adhesion enhancement with the electrolessly deposited copper. X‐ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) results revealed that the pyridine groups in the plasma polymerized 4VP (pp‐4VP) layer could be preserved to a large extent under proper glow discharge conditions. The grafted 4VP layer with well‐preserved pyridine groups was used not only as the chemisorption sites for the palladium complexes (without the need for prior sensitization by SnCl2) during the electroless plating of copper, but also as an adhesion promotion layer for the electrolessly deposited copper. The T‐peel adhesion strength of the electrolessly deposited copper with both the 4VP plasma‐polymerized FPI (pp‐4VP‐FPI) film and the 4VP graft‐copolymerized FPI (4VP‐g‐FPI) film was much higher than that of the electrolessly deposited copper with the pristine or the Ar plasma‐treated FPI films. The high adhesion strength between the electrolessly deposited copper and the surface‐modified FPI film was attributed to the fact that the plasma‐polymerized and the UV graft‐copolymerized 4VP chains were covalently tethered on the FPI surfaces, as well as the fact that these grafted 4VP polymer chains were spatially and reactively distributed into the copper matrix. magnified image

Effect of pH and H 2 O 2 on Ta Chemical Mechanical Planarization : Electrochemistry and X-Ray Photoelectron Spectroscopy Studies

Tantalum is used as a diffusion barrier and adhesion promoter layer between the dielectric material and copper interconnects. The present study was intended to investigate the effect of oxidizer and solution pH on chemical mechanical planarization of tantalum. High purity Ta disks were used to study the dissolution and oxidation kinetics under static and dynamic conditions using various solutions in acidic and alkaline pH regimes. The electrochemical measurements during dynamic polishing of a Ta disk were carried out using slurries containing silica and alumina particles with hydrogen peroxide at various pH levels. The affected surface layers of the statically etched Ta disk were investigated using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and secondary ion mass spectrometry (SIMS). Ta metal was observed to oxidize in aqueous solutions at pH 2, 4, and 12 in absence of The oxidation process follows the parabolic kinetic law and oxidation rate was observed to be higher in an alkaline region than in an acidic region. In the presence of however, Ta dissolved in the alkaline region. The dissolution was found to be greater at pH 12 mainly because of enhanced dissociation of in alkaline region. At pH 2, on the contrary, mass gain was observed probably due to an increase in content on the top of Ta oxide formed on the surface as confirmed by XPS and SIMS depth profile studies. XPS study revealed that the oxidation of tantalum takes place at a rapid rate and forms soluble oxotantalate and hydroxotantalate in solution at pH 12 in the presence of hydrogen peroxide. AFM study validates both the XPS and the SIMS results, indicating formation of a thin impervious oxide layer on Ta in a solution at pH 2 with 5% and a porous layer was formed on Ta in solution with 5% at pH 12. Consequently, the dissolution rate in alkaline region was enhanced which was confirmed by dynamic removal rate measurements, electrochemistry, and XPS studies. © 2002 The Electrochemical Society. All rights reserved.

Selective Electroless Plating of Copper on (100)-Oriented Single Crystal Silicon Surface Modified by UV-Induced Coupling of 4-Vinylpyridine with the H-Terminated Silicon

A Sn-free electroless plating process for producing patterned and adherent copper deposits on (100)-oriented single-crystal silicon substrates is described. Pristine and resist-patterned Si(100) substrates were etched, initially, by aqueous HF to produce the hydrogen-terminated silicon surfaces (H−Si(100) surfaces). The H−Si(100) surfaces were further functionalized by the UV-induced reactive coupling of 4-vinylpyridine (4VP). The composition and topography of the modified Si(100) surfaces were characterized by X-ray photoelectron spectroscopy and atomic force microscopy, respectively. The coupled 4VP layer exhibited good stability in boiling chloroform, boiling water, sonicating dichloromethane, aqueous solution of HF and aqueous solution of KOH. Not only did the 4VP layer provide chemisorption sites for the palladium complexes without the need for prior sensitization in SnCl2 solution during the electroless plating process but it also served as the adhesion promotion layer and diffusion barrier for the ...

Electroless Plating of Copper on (100)-Oriented Single Crystal Silicon Substrates Modified by Plasma Graft Polymerization of 4-Vinylpyridine

Plasma graft polymerization of 4-vinylpyridine (4VP) on Ar plasma-pretreated Si(100) surfaces was carried out. The plasma graft-polymerized 4VP films (pp-4VP films) were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, and atomic force microscopy (AFM). XPS and FTIR results revealed that the pyridine functional groups of the grafted pp-4VP films could be retained, to a certain extent, under proper glow discharge conditions, such as a low input radio frequency power. AFM images revealed that the pp-4VP-grafted Si(100) (pp-4VP-Si) surfaces remained relatively smooth. The grafted pp-4VP film on the Si(100) surface was used not only as the chemisorption sites for the palladium complexes (without the need for prior sensitization by during the electroless plating of copper, but also as an adhesion promotion layer for the electrolessly deposited copper. The electrolessly deposited copper on the pp-4VP-Si surface exhibited a 180°-peel adhesion strength above 5 N/cm. The adhesion strength was attributed to the strong interaction of the pyridine functional groups of the pp-4VP layer with palladium and copper, the spatial distribution of the pp-4VP chains on the Si(100) surface and into the metal matrix, and the fact that the pp-4VP chains were covalently tethered on the Si(100) surface. © 2002 The Electrochemical Society. All rights reserved.

Electroless plating of copper on polyimide films modified by plasma graft copolymerization with 4-vinylpyridine

Surface modification of argon plasma-pretreated polyimide (PI, Kapton® HN) films by plasma graft copolymerization with 4-vinylpyridine (4VP) was carried out. The effects of glow discharge conditions on the chemical composition and structure of the plasma-polymerized 4VP (pp-4VP) films were analyzed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy, respectively. The XPS and FTIR results revealed that the pyridine groups in the pp-4VP layer could be preserved to a large extent under proper glow discharge condition. The topography of the modified PI surface was investigated by atomic force microscopy (AFM). The pp-4VP film with well-preserved pyridine groups was used not only as the chemisorption sites for the palladium complexes (without the need for prior sensitization by SnCl2) during the electroless plating of copper, but also as an adhesion promotion layer to enhance the adhesion of the electrolessly deposited copper with the PI film. The T-peel adhesion strength of the electrolessly deposited copper to the pp-4VP grafted PI (pp-4VP-PI) film could reach about 7 N/cm. This adhesion strength was much higher than that of the electrolessly deposited copper to the pristine or the Ar plasma-treated PI film.

Enhancement of isopropanol-based photoresist removal by the addition of aqueous alkaline solutions

Removal of photoresist films along with underlying hexamethyldisilazane (HMDS) layers from SiO2 surfaces was studied using isopropanol (IPA) and IPA/NH4OH/H2O mixtures. Although IPA removed photoresist layers, pure IPA was unable to remove the HMDS layer, even at temperatures above 60 °C and pressures above 50 psi. Addition of NH4OH/H2O to IPA resulted in attack of the Si–O–Si bonds at the Si/HMDS interface. Residual carbon concentrations as low as 2.5 at. % on the posttreated surfaces were observed. IPA/NH4OH/H2O surfaces exhibited hydrophilic contact angles (15°–20°) indicating removal of both photoresist and the adhesion promoter layer from silicon dioxide surfaces. Atomic force microscopy analyses indicated no increase in the SiO2 surface root-mean-square roughness.

Thermal Imidization of Fluorinated Poly(amic acid)s on Si(100) Surfaces Modified by Plasma Polymerization and Deposition of Glycidyl Methacrylate

Plasma polymerization of glycidyl methacrylate (GMA) on pristine and plasma-pretreated Si(100) surfaces was carried out. The epoxide functional groups of the plasma-polymerized GMA (pp-GMA) could be preserved, to a large extent, by controlling the glow discharge parameters. The pp-GMA film was used as an adhesion promotion layer for the thermal imidization of fluorinated poly(amic acid) (FPAA) precursors on Si substrates. The fluorinated polyimide (FPI)/pp-GMA−Si laminates so formed exhibited a 180°-peel adhesion strength as high as 10 N/cm. This value was much higher than the negligible adhesion strength for the FPI/Si laminates obtained from thermal imidization of the FPAAs on either the pristine or the argon-plasma-treated Si surfaces. The high adhesion strengths of the FPI/pp-GMA−Si laminates were attributed to the synergistic effect of coupling the curing of the epoxide groups in the pp-GMA layer with the imidization process of the FPAAs and the fact that the plasma-deposited GMA chains were covalently tethered on the Si(100) surface. Comparison of the adhesion strengths of the FPI/pp-GMA−Si laminates to that of the polyimide (PI)/pp-GMA−Si laminate, formed by thermal imidization of the poly(amic acid) precursor of poly(pyromellitic dianhydride-co-4,4‘-oxydianiline) on pp-GMA−Si, suggests that the presence of fluorine-containing groups, such as −CF3, in the PI chains has a negligible effect on the adhesion property of the FPIs on the Si(100) wafer surface modified by the present interfacial molecular design and lamination technique.

The interface of fluorinated amorphous carbon with copper metallization

We have studied fluorinated amorphous carbon (a-F:C) films, prepared by High Density Plasma Chemical Vapor Deposition (HDP-CVD) methods from CH 4 and C 4F 8, as candidates for low- k inter metal dielectric (IMD) applications. In order to enhance the film's adhesion to the adjacent layers, an adhesion promoter layer was introduced. The samples used for the current research consist of a metal layer (Cu or its diffusion barriers Ta or TaN) and the a-F:C film, with the adhesion promoter sandwiched in between. In order to learn about the film and interfaces stability the samples were annealed at 400 and 500°C for 30 min. Up to 400°C, no metal diffusion into the adhesion promoter was observed. After 30 min of 500°C annealing, no Cu outdiffusion was observed by XPS nor was a change in the Cu2p transition peak's form suggesting that no serious chemical reaction has occurred at the interface. No major Cu diffusion was detected by RBS but SIMS measurements have showed Cu diffusion into the adhesion promoter after 500°C annealing, 30 min. The dielectric constant of the film is ∼2.7 (measured by C– V at 1 MHz) after 400°C annealing and much higher after 500°C annealing. The results obtained so far show that the integration of a-F:C as IMD is possible but there are some problems to be solved.

Study of Ta as a Diffusion Barrier in Cu/SiO2 Structure

AbstractTantalum (Ta) thin films of 35 nm thickness were investigated as diffusion barriers as well as adhesion-promoting layers between Cu and SiO2 using X-ray diffractometry (XRD), Scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). After annealing at 600°C for 1h in vacuum, no evidence of interdiffusion was observed. However, XPS depth profiling indicates that elemental Si appears at the Ta/SiO2 interface after annealing. In-situ XPS studies show that the Ta/SiO2 interface was stable until 500°C, but about 32% of the interfacial SiO2 was reduced to elemental Si at 600°C. Upon cooling to room temperature, some elemental Si recombined to form SiO2 again, leaving only 6.5% elemental Si. Comparative studies on the interface chemical states of Cu/SiO2 and Ta/SiO2 indicate that the stability of the Cu/Ta/SiO2/Si system may be ascribed to the strong bonding of Ta and SiO2, due to the reduction of SiO2 through Ta oxide formation.

Thermal imidization of poly(amic acid) on Si(100) surface modified by plasma polymerization of glycidyl methacrylate

The plasma polymerization of glycidyl methacrylate (GMA) on pristine and Ar plasma-pretreated Si(100) surfaces was carried out. The epoxide functional groups of the plasma-polymerized GMA (pp-GMA) could be preserved, to a large extent, through the control of the glow discharge parameters, such as the radio-frequency (RF) power, carrier gas flow rate, system pressure, and monomer temperature. The pp-GMA film was used as an adhesion promotion layer for the Si substrate. The polyimide (PI)/pp-GMA-Si laminates, formed by thermal imidization of the poly(amic acid) (PAA) precursor poly(pyromellitic dianhydride-co-4,4′-oxydianiline) (PMDA-ODA) on the pp-GMA-deposited Si surface (the pp-GMA-Si surface), exhibited a 180°-peel adhesion strength as high as 9.0 N/cm. This value was much higher than the negligible adhesion strength for the PI/Si laminates obtained from thermal imidization of the PAA precursor on both the pristine and the argon plasma-pretreated Si(100) surfaces. The high adhesion strength of the PI/pp-GMA-Si laminates was attributed to the synergistic effect of coupling the curing of epoxide functional groups in the pp-GMA layer with the imidization process of the PAA, and the fact that the plasma-deposited GMA chains were covalently tethered onto the Si(100) surface. The chemical composition and structure of the deposited films were characterized, respectively, by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy, while the surface morphology of the deposited films was characterized by atomic force microscopy (AFM).