Electrical behaviour of discontinuous silver films deposited on compatible Polystyrene/Poly (2-vinylpyridine) composite

Polystyrene (PS) and Poly (2-vinylpyridine) (P2VP) was melt blended. The compatibility of PS/P2VP was investigated by differential scanning calorimetry (DSC), Fourier transmission Infrared (FTIR) and scanning electron microscopy (SEM). The results indicated the single glass transition temperature for the blend. Results of the studies carried out on the electrical behaviour of silver island films deposited on the composite of PS and P2VP are presented here. The substrates were held at 457 K, much above the glass transition temperature of the polymers to ensure sufficient polymer fluidity during deposition, to obtain a sub-surface particulate film. A constant deposition rate of 0.4 nm/s was used through out the study. Silver films deposited on softened PS give rise to a very high room temperature resistance approaching that of the substrate resistance due to the formation of a highly agglomerated structure. On the other hand, films on softened P2VP gives rise to a room temperature resistance in the range of tens to a few hundred MΩ/□ which is desirable for device applications. The composite of PS and P2VP show resistances at room temperature. The films show an increase in resistance, when they are exposed to atmosphere. This is attributed to the oxidation of silver islands. The film resistances in the desired range could be obtained even, after exposure to atmosphere with PS concentration of 50%.     

Preparation and characterization of silver particulate films on softened polystyrene and poly(4-vinylpyridine) blends

Results of the investigations carried out on the optical properties of silver particulate films deposited at a rate of 0.4 nm/s on softened polystyrene and poly(4-vinylpyridine) (P4VP) blends held at 455 K are reported. Under the conditions of deposition, a sub-surface particulate structure is expected. It had been shown earlier that the morphology of the sub-surface particulate structure is dependent on polymer-metal interaction. In the present studies, an inert polymer like polystyrene (PS) is blended with an interacting polymer P4VP. The optical studies on the silver particulate films deposited on softened blends of PS/P4VP have been carried out. The results show a shift in plasmon resonance to higher wavelength with increasing P4VP concentration of the blends in comparison to that of the films deposited on pure PS. An X-ray photoelectron spectroscopy study at two different electron take off angles indicates the formation of subsurface particulate structures for films deposited on blends.     

Optical properties of sub-surface silver nanoparticulate films on 8 MeV electron beam irradiated polymer blends

Results of the investigations carried out on the optical properties of silver nanoparticulate films deposited on the electron beam irradiated blends of polystyrene (PS) and poly(4-vinylpyridine) (P4VP) are reported. Sub-surface silver particulate films are deposited at a constant deposition rate of 0.4 nm/s on irradiated blends held at 455 K in a vacuum of 8 × 10^?6 torr. The optical absorption studies indicate that the morphology of the nanoparticulate films can be tuned by electron beam irradiation of polymer blends. The change observed due to irradiation is attributed to the formation of free radicals, thereby altering the polymer–metal interaction. A shift in the plasmon resonance peak towards longer wavelengths is observed for 50 nm thick silver particulate films deposited on softened 8 MeV electron irradiated P4VP as compared to unirradiated P4VP. The shift is more in the case of P4VP than for PS, possibly due to the combined effect of free radicals produced by irradiation and the lone pair of electrons present in P4VP in enhancing the metal–polymer interaction. The saturation of free radicals takes place in P4VP at doses higher than 25 kGy. Further, the results also indicate that the free radical creation due to irradiation is more in PS than in P4VP, as the saturation takes place at lower doses in a PS/P4VP blend as compared to P4VP and in a blend with higher PS content. X-ray diffraction studies on silver films deposited on unirradiated and irradiated, softened polystyrene substrates do not show any significant change due to irradiation.     

Electrical behaviour of discontinuous silver films deposited on softened polystyrene and poly (4-vinylpyridine) blends

Results of the studies carried out on the electrical behaviour of silver island films deposited on the blends of polystyrene (PS) and poly (4-vinylpyridine) (P4VP) are presented here. The substrates were held at 457 K, much above the glass transition temperature of both the polymers to ensure sufficient polymer fluidity during deposition, to obtain a sub-surface particulate film. A constant deposition rate of 0.4 nm/s was used throughout the study. Films on softened PS gives rise to a very high room temperature resistance approaching that of the substrate resistance due to the formation of a highly agglomerated structure. On the other hand, films on softened P4VP gives rise to a room temperature resistance in the range of a few tens to a few hundred MΩ/, which is desirable for device applications. The blends of PS and P4VP show room temperature resistances in the desirable range even at a PS/P4VP ratio of 75:25. The films show an increase in resistance when they are exposed to atmosphere. This is attributed to the oxidation of silver islands. The film resistances in the desired range could be obtained even after exposure to atmosphere up to a PS concentration of 50%.     

Electrical behavior of silver particulate films deposited on 8 MeV electron beam irradiated softened polystyrene substrates

Results of the investigations carried out on the electrical behavior of silver particulate films deposited on electron beam irradiated polystyrene (PS) coated substrates held at a temperature of 455 K in a vacuum of 8 × 10⁻⁶ torr at a constant deposition rate of 0.4 nm/s are reported. It is known that when metals are evaporated on to softened polymer substrates, subsurface particulate structures are formed whose morphology is dependent on deposition parameters. Further, it was shown that the morphology is dependent on polymer-metal interaction. The present work demonstrates that the polymer-metal interaction can be brought about in inert polymers like PS by electron irradiation. The results indicate that the films deposited on PS irradiated to a dose of 20 and 25 kGy gives rise to smaller clusters with smaller inter-cluster separation, better suited for sensor applications. The induced polymer-metal interaction is attributed to the creation of free radicals due to the 8 MeV electron irradiation.     

Effect of oxygen plasma treatment on bonding states for columnar structured a-CNx thin films prepared by reactive sputtering

Amorphous carbon nitride (a-CN) thin films were deposited on silicon single crystal substrates by rf-reactive sputtering method using a graphite target and nitrogen gas. The substrate temperature was varied from room temperature (RT) to 853 K. After deposition, the effect of oxygen plasma treatment on bonding structures of the film surface has been studied by using an oxygen discharge at 16 Pa and rf power of 85 W. The chemical bonding states and film composition were analyzed by X-ray photoelectron spectroscopy (XPS), while film thickness was obtained from scanning electron microscopy (SEM) and ellipsometer. XPS study revealed that the films have NO₂ and NO₃ bonding structures when the films are deposited at temperatures higher than 673 K. After exposure to oxygen plasma, carbon in the film surface was etched selectively and this phenomenon was observed in all films. In contrast, the surface concentration of nitrogen was ket at constant values before and after oxygen plasma treatment. The NO₃ bonding state had dramatically increased after oxygen plasma treatment for films deposited at higher deposition temperatures. The film surfaces have been observed to change the function from hydrophobic to hydrophilic after oxygen plasma treatment.     

The effect of substrate temperature on the oxidation behavior of erbium thick films

The effect of substrate temperature on the oxidation behavior of erbium thick films, fabricated by electron-beam vapor deposition (EBVD), was investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The erbium thick film is black when it is deposited at substrate temperature below 450 °C and turns gray at higher substrate temperature in a vacuum pressure of approximately 1.5 × 10⁻⁶ Torr, which indicates that the thickness of erbium oxide layer formed on the surface of erbium films increases with the decreasing substrate temperature. XPS depth profile results demonstrate that the thickness of the surface erbium oxide layer of erbium film deposited at substrate temperature of 550 and 350 °C are about 50 and 75 nm, respectively. The thicker oxide layer at lower substrate temperatures may be attributed to grain size and the dynamic vacuum condition around the substrates. Other possible factors involved in the oxidation behavior are also discussed.     

Microstructural and optical properties of BN films deposited by inductively coupled plasma CVD

Boron nitride films were deposited at different substrate temperatures (400-600 K) on Si (100) substrates by RF plasma CVD technique using a mixture of borane-ammonia, argon and nitrogen as the precursor gases. No intentional bias was applied during deposition to modulate the ion energy. The surface textures of the films were obtained by Atomic Force Microscope studies (AFM). X-ray Photoelectron Spectroscopy (XPS) studies were carried out to determine the bonding environment in the coatings. Fourier Transformed Infra-Red (FTIR) spectrums indicated that the films deposited at lower substrate temperature contained h-BN phases and the percentage of c-BN content in the films increased with the substrate temperature. Films deposited at temperature ∼553 K were predominantly c-BN in nature.     

Surface morphology and composition of films grown by size-selected Cu nanoclusters

We report the investigation of morphology and composition of copper nanocluster films deposited on Si substrates. The nanoclusters are formed in an aggregation tube at room temperature and magnetron sputtering source is used to get negatively charged Cu-clusters' beam which is subsequently mass-filtered to get size-selected cluster on the substrates as soft-landing process of deposition. For composition of the films, X-ray photoelectron spectroscopy (XPS) technique is used. For morphological changes of the films both scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses are carried out. Additionally, Energy Dispersive X-ray (EDX) spectra support the compositional and structural informations of the film. The analysis of Cu nanoclusters' films reveals that initial nucleation of Cu clusters takes place in the form of isolated islands and the arrival of subsequent Cu clusters onto Si substrates has preferential aggregation around the preceding clusters forming a mound structure.     

Influence of process parameters on the microstructure of scandium films deposited by electron-beam evaporation

Microstructures of scandium films deposited on molybdenum (Mo) substrates by electron-beam evaporation are investigated. Influences of substrate temperatures and deposition rates are considered. It is found that the microstructural changes of scandium films with the substrate temperatures are consistent with the reported structure-zone models. Sc films, deposited at 5 nm/s with the temperature range of 373-923 K, as well as deposited at 923 K with the deposition rate from 0.5 to 5 nm/s, show a (002) preferred orientation. Both the texture coefficients of (002) peaks and the grain sizes increase with the substrate temperature. For films deposited at various deposition rates, the films show smoother surfaces at the lower deposition rate. Moreover, the grain sizes first increase with the increasing deposition rate and then decrease with it. The largest grain size (∼246 nm) is obtained at the deposition rate of 5 nm/s. The texture coefficients of the (002) preferred orientation decrease when the deposition rate increases from 0.5 nm/s to 5 nm/s. And the preferred growth of the film disappears at deposition rate of 10 nm/s.     

In-situ X-ray investigations of quench-condensed thin gold films

Thin gold films were deposited on float glass substrates held at cryogenic temperatures down to 77 K and investigated in-situ using X-ray reflectometry and surface sensitive reflection mode X-ray absorption spectroscopy (XAFS). The combination of these in-situ X-ray methods with simultaneous electrical resistivity measurements yields information about the surface and volume microstructure of the deposited films as a function of the deposition temperature and their changes induced by a subsequent annealing treatment. The surface sensitive XAFS experiments clearly proved that the films exhibit a polycrystalline structure throughout the temperature range studied here. The data were fitted using a correlated Debye-model. The results show that for film deposition at low substrate temperatures < 130 K, a significantly decreasing Debye-temperature was found, reaching values of about 100 K in comparison to 165 K for the polycrystalline bulk material. This decrease was interpreted to be predominantly related to defective film regions with an increased static disorder.     

Structural properties of silver particulate films deposited on softened polymer blends of polystyrene/poly (2-vinyl pyridine)

Results of the structural studies of silver particulate films deposited at a rate of 0.4 nm/s on polymeric blends of polystyrene/poly (2-vinyl pyridine), PS/P2VP held at a temperature 457 K by evaporation in a vacuum of 8 × 10⁻⁶ Torr are reported here. The morphology of silver particulate films, characterized by their size, size distribution, shape and inter-particle separation, was observed to modify due to blending of PS with P2VP and amount of silver deposited. The red shift in the plasmon resonance indicates the effect of blending P2VP with PS. Scanning electron microscopy was used to study the change in morphology of the silver nanoparticles in correlation with the optical properties of silver particulate films on PS/P2VP blends. The silver nanoparticles on the thin layers of polymer blends exhibited much smaller, narrower dispersion and wide size distribution due to blending of PS with P2VP.     

SiC/C薄膜的制备及其力学性能

以SiC 超细粉为原料、采用热等离子体物理气相沉积( TPPVD) 技术快速制备出了高质量SiC/ C 薄膜, 最大沉积速度达到225 nm/ s, 高于常规物理气相沉积( PVD) 和化学气相沉积(CVD) 法两个数量级。用扫描电子显微镜、高分辨透射电子显微镜和X 射线光电子谱对薄膜的形貌和微结构进行了观察和分析, 并用纳牛力学探针测定了薄膜的力学性能。研究结果表明, 向等离子体中导入CH₄, SiC/ C 薄膜沉积速度增大, 薄膜中C 含量增加, 薄膜断面呈现柱状结构。薄膜硬度和弹性模量随薄膜中C 含量增加而降低, 在接触深度为40 nm 时由纳牛力学探针测得沉积薄膜的最大硬度达到38 GPa。     

Nano-particle thin films of tin oxides

Nano-particle thin films of tin oxides were deposited on SiO₂ substrates by using radio frequency (RF) magnetron sputtering with various substrate temperatures, sputtering powers and oxygen partial pressures. The tin oxides thin films were then investigated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). XPS data suggested that the deposited tin oxides thin films are almost made up of half of SnO₂ and half of SnO. The oxygen partial pressure nearly does not affect the chemical stoichiometry of the thin films in our deposition conditions. SEM results showed that the tin oxides thin films were formed by nano-particles with size of about 60 nm. Sputtering power has a strong influence on the particle size of the thin films. Increase of sputtering power will enlarge the size of the particles.     

Effects of deposition temperature on the microstructure of MOCVD Y1Ba2Cu3O7−x thin films

The effects of deposition temperature on the microstucture and composition of Y₁Ba₂Cu₃O_7–x films deposited on MgO and SrTiO₃ substrates by the metal-organic chemical vapour deposition (MOCVD) method were investigated. As the deposition temperature decreased from 900 to 700 °C, the Cu content in the deposited film increased. SEM micrographs of the films showed that the growth direction of the film was changed from c axis to a axis perpendicular to the substrate surface, and then to random orientation, as the deposition temperature decreased. The superconducting transition temperature and the transition width of films deposited on SrTiO₃ substrates at temperatures higher than 810 °C were over 90 K and within 1 K, respectively.     

Chemical vapor deposition of aluminum from methylpyrrolidine alane complex

Chemical vapor deposition of aluminum from a recently developed precursor, methylpyrrolidine alane complex, has been studied. Aluminum films deposited on conducting surfaces (titanium nitride, copper, gold), but not on insulating surfaces (silicon, silicon dioxide, glass) at low substrate temperatures, showing deposition selectivity, while the deposition selectivity was lost at high substrate temperatures (> 210 °C). Al deposition rates on TiN and Cu were very close, but much higher than on Au. Deposition rates on all conducting substrates increased with the temperature and reached maximum at 180 °C. Al films deposited on as-sputtered TiN or Cu have no preferred orientations. Al–Au alloys and intermetallics were observed in the films deposited on Au. Surface morphology observation revealed that the film growth on TiN or Cu is different from that on Au. The surface roughness of Al films increased with the deposition time or the film thickness.     

A study of electron-beam-evaporated MgO films using electron diffraction,optical absorption and cathodoluminescence

Reflection high energy electron diffraction, optical absorption and cathodoluminescence were used to study MgO films deposited onto fused silica, single- crystal silicon and LiF substrates at various temperatures. Results showed that some of the same optical absorption and emission bands observed in X- or UV- irradiated, additively colored or mechanically deformed MgO crystals were observed in evaporated MgO films. The peak positions and the relative peak intensities of the optical absorption and emission bands depended on the substrate temperature during film deposition as well as on the structure of the film. The effect of heating the films in air and vacuum on the optical absorption and emission bands is also discussed.     

Influence of deposition temperature on the growth of vacuum evaporated V2O5 thin films

V₂O₅ films were deposited on silicon (111) substrates by vacuum evaporation technique at various deposition temperatures of 300, 473, 573, 623 and 673 K. X-ray characterization revealed that the films deposited at T_s≤473 K are amorphous and the film deposited at T_s≥573 K is polycrystalline. It is interesting to note that the film deposited at T_s=573 K is strongly oriented with (001) planes parallel to the substrate and the degree of preferred orientation towards (001) planes found to decrease with further increase in the deposition temperature. The influence of deposition temperature on the growth of the V₂O₅ films has been studied by Raman scattering spectroscopy. The films deposited on the silicon substrates maintained at 573 K are found to have better structural quality.     

High quality ZnO films deposited by radio-frequency magnetron sputtering using layer by layer growth method

Three-layered ZnO films were deposited on Si substrates by radio-frequency magnetron sputtering using layer by layer growth method. The Raman scattering confocal analysis confirms that ZnO film quality is improving at increasing the number of ZnO layers at film deposition.Applied method of deposition was used to realize homoepitaxial growth of ZnO films on c-Al₂O₃, Si, SiN_x/Si, glass and ITO/glass substrates. In order to improve the film quality we increased the number of deposition stages up to 5. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmittance measurements were used to testify the quality of grown five-layered ZnO films. XRD results showed that all five-layered ZnO films have (002) texture. The second order diffraction peak (004) on XRD spectra additionally testifies to the high quality of all five-layered ZnO films. SEM results demonstrated that no defects such as cracks and dislocations caused by interruption of deposition ZnO films were observed. Transmittance measurement results showed that ZnO films deposited on transparent substrates have abrupt absorption edge and high optical transmission in the visible region of the spectrum.     

Structural and electrical properties of RuO2 thin films prepared by rf-magnetron sputtering and annealing at different temperatures

Conductive ruthenium oxide (RuO₂) thin films have been deposited at different substrate temperatures on various substrates by radio-frequency (rf) magnetron sputtering and were later annealed at different temperatures. The thickness of the films ranges from 50 to 700 nm. Films deposited at higher temperatures show larger grain size (about 140 nm) with (200) preferred orientation. Films deposited at lower substrate temperature have smaller grains (about 55 nm) with (110) preferred orientation. The electrical resistivity decreases slightly with increasing film thickness but is more influenced by the deposition and annealing temperature. Maximum resistivity is 861 μΩ cm, observed for films deposited at room temperature on glass substrates. Minimum resistivity is 40 μΩ cm observed for a thin film (50 nm) deposited at 540°C on a quartz substrate. Micro-Raman investigations indicate that strain-free well-crystallized thin films are deposited on oxidized Si substrates.