Growth behavior and surface topography of different silane coupling agents adsorbed on the silicon dioxide substrate (0001) for vapor phase deposition

The growth behavior and surface topography of the deposited films formed from silane coupling agents on silicon dioxide substrate (0001) via vapor phase deposition was investigated using atomic force microscopy (AFM). The surface topography of the films adsorbed on the silicon dioxide substrates is dissimilar with different silane coupling agents and different deposition conditions: (1) the films adsorbed on the silicon dioxide substrate become smoother with the increasing temperature of the silicon dioxide substrate; (2) the surface roughness of the films increases with the increasing concentration of the silane coupling agent solutions; (3) with the increasing temperature of the carrier gas, the surface roughness of the films decreases firstly and then increases; (4) with the increasing time of deposition, the surface roughness of the films increases firstly, then decreases and subsequently increases again. In experiments, the films adsorbed on the silicon dioxide substrate was rinsed ultrasonically with toluene, the results indicate that the silane coupling agent adsorbed on the substrate by physisorption and chemisorption: the chemisorbed coupling agents present island morphology and the physisorbed coupling agents are deposited on the substrate between the islands to decrease the surface roughness of the film.     

Cold deposition of large-area amorphous hydrogenated silicon films by dielectric barrier discharge chemical vapor deposition

Amorphous hydrogenated silicon films were deposited on glass substrates at room temperature. This cold deposition process was operated in a dielectric barrier discharge CVD reactor with a fixed strip-shaped plasma matched with a moving substrate holder. The maximum film area was 300 × 600 mm². The film deposition rate as a function of applied peak voltage of DBD power was investigated under different hydrogen-diluted silane concentrations, and the film surface smoothness, continuity, and film/glass adherence were also studied. The maximum deposition rate was 12.2 Å/s, which was performed under the applied peak voltage of 16 kV and a hydrogen-diluted silane concentration of 50%. IR measurements reveal that the silane concentration plays a key role in determining the hydrogen-silicon bonding configurations. With increasing hydrogen-diluted silane concentration, the H-Si bonding configurations shift gradually from Si-H₃ to Si-H. The variation of photo/dark conductivity ratio and optical bandgap versus hydrogen-diluted silane concentration were investigated. The use of DBD-CVD for deposition of a-Si:H films offers certain advantages, such as colder substrate, faster film growth rate, and larger deposition area. However, the consumption of silane for the DBD-PECVD procedure is much greater than for the RF-PECVD process.     

Selective laser sintering of barium titanate–polymer composite films

A selective laser sintering process has been used to consolidate electro-ceramic thin films on silicon substrates. Methods of forming pre-positioned layers of barium titanate were investigated by spin-coating the feedstock powder mixed with a commercial polymer photo-resist. The ceramic–polymer composite was deposited directly onto a nickel film which was evaporated onto a silicon substrate, pre-oxidised to form an electrically insulating layer. A range of laser processing parameters was identified in which consolidated barium titanate layers could be formed. The laser power was found to be more influential in forming sintered microstructures than laser exposure time. The microstructure of barium titanate films is sensitive to the SLS laser-processing conditions, with the optimum laser powers for the processing of the BaTiO₃–polymer found to be in the range 17–20 W. This article highlights the possibility of using ‘direct write’ techniques to produce piezoelectric materials upon silicon substrates.     

PECVD法制备非晶硅薄膜及光电性能研究

采用等离子体增强化学气相沉积（PECVD）方法在玻璃衬底上制备出非晶硅薄膜,利用正交试验法对射频功率、气体总压、硅烷比例、沉积时间、退火温度、退火时间因素进行了研究,对透过率和电阻率进行了分析,结果表明,采用PECVD法成功制备出非晶硅薄膜。正交实验表的分析得知,气体总压对透过率影响最大;硅烷比例对电阻率影响最大。制备非晶硅薄膜的优化条件为：射频功率30W、气体总压100Pa,硅烷5％、沉积时间5min、退火温度300℃、退火时间45min。非晶硅薄膜的光透过率93．18％,电阻率为13．238kΩ·cm。     

Non-uniform deposition in the early stage of hot-wire chemical vapor deposition of silicon: The charge effect approach

The deposition behavior in hot-wire chemical vapor deposition (HWCVD) of silicon was investigated, focusing on the thickness uniformity of films deposited on silicon and glass substrates, and based on the previous suggestion that a major depositing flux in HWCVD should be negatively charged nanoparticles. The deposition was performed using a 20%-SiH₄-80%-H₂ gas mixture at a 450 °C substrate temperature under a working pressure of 66.7 Pa (0.5 Torr). Non-uniform depositions for three hot-wire temperatures, 1590 °C, 1670 °C, and 1800 °C, and on the silicon and glass substrates were compared. The non-uniformity was most pronounced at 1800 °C and more pronounced on the glass substrate. On the glass substrate, the deposition rate was highest at the corner and lowest at the center, which was attributed to the fastest charge removal, to a conducting stainless steel substrate holder, at the corner. Once the entire glass substrate was deposited with silicon, the growth rate tended to become uniform, possibly due to the high charge removal rate of silicon. The observed deposition behavior indicated that the major depositing flux is negatively charged.     

The effects of substrates on the thin-film structures of BaTiO3

Barium titanate (BaTiO₃) thin films prepared on magnesia, silicon and strontium titanate substrates by r.f. sputtering has been investigated. As a function of substrate and annealing temperatures, the crystal structure and shape were examined by X-ray diffraction and scanning electron microscopy. Thin films were grown on both MgO and silicon substrates; they were amorphous when deposited on MgO if the substrate temperature was less than 450 °C, while for those grown on silicon the temperature had to be less than 500 °C. Above these elevated temperatures, the films were crystalline, with cubic symmetry. After annealing the thin films on magnesia, the crystal structure changed from cubic to tetragonal phase above 1100 °C; thebe c-axis or annealing thus caused the grain growth of the BaTiO₃. The thin films on SrTiO₃ were found toc-axis oriented tetragonal films for a substrate temperature above 500 °C.     

Process optimization and related material properties of silicon films produced by laser-induced chemical vapour deposition from silane

Laser-induced chemical vapour deposition of silicon films on SiO₂/Si (1 0 0) and Si (1 0 0) substrates was studied using ArF laser irradiation of silane/argon gas mixture in parallel to the substrate. The optimal deposition conditions were specified by examination of film morphology at a wide range of irradiation and process parameters. At optimal conditions, specular films were obtained with no powder formation. The effect of deposition parameters, such as laser energy and repetition rate, on the deposition rate and the related film quality, was investigated.     

Growth and characterization of diamond films deposited at high-pressure using a low-power microwave plasma reactor

Diamond films were deposited on molybdenum substrates from mixtures of methane diluted in hydrogen using a high-pressure microwave plasma reactor. In this reactor, a compressed waveguide structure was used to increase the electric field strength, and accordingly the reactor was able to operate stably with low gas flow rate and microwave power. The films deposited on 12 mm diameter substrates were characterized by film morphology, Raman spectra, growth rate and crystalline quality. The morphology of diamond films deposited in this reactor depends mainly on the substrate temperature. When the deposition pressure was 48 kPa and microwave power was only 800 W, high quality diamond films could be uniformly deposited with a growth rate around 20 μm/h.     

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.     

用ECRCVD方法制备优质氮化硅钝化膜

利用电子回旋共振等离子体化学气相沉积(ECR—CVD)技术，以SiH4和N2为反应气体进行了氮化硅钝化薄膜的低温沉积技术的研究。采用原子力显微镜、傅立叶变换红外光谱和椭圆偏振光检测等技术对薄膜的表面形貌、结构、厚度和折射率等性质进行了测量。结果表明，采用ECR—CVD技术能够在较低的衬底温度条件下以较高的沉积速率制备厚度均匀的氮化硅薄膜，薄膜中H含量很低。薄膜沉积速率随微波功率和混合气体中硅烷比例的增加而增大。折射率随微波功率的增大而减小，随混合气体中硅炕比例的增大而增大。在相同气体混合比和微波功率条件下，较高衬底温度条件下制备的薄膜折射率较大。     

Influence of dopant concentration and type of substrate on the local organization of low-pressure chemical vapour deposition in situ boron doped silicon films from silane and boron trichloride

The deposition of in situ boron doped silicon films from boron trichloride BCl₃ and silane SiH₄ in a conventional low-pressure chemical vapour deposition reactor has been studied for high boron doping levels and two kinds of substrates (SiO₂ and Si₃N₄). On the basis of transmission electron microscopy and X-ray photoelectron spectroscopy results, these films appear to be highly sensitive to the local electronic environment of both substrate and deposited atoms. Indeed, beyond a critical doping level, this material becomes more and more amorphous, due to the occurrence of a particular organization of boron atoms in the silicon matrix. This behaviour results in a lowering of the well-known boron enhancement effect for deposition rate and crystalline fraction.     

Growth of polycrystalline-silicon thin films on glass

Borosilicate glass was chosen as a substrate for solution growth of silicon due to its potential role as the superstrate of a solar module. The deposition of polycrystalline silicon on glass from solutions containing aluminium or magnesium is reported. Island growth was usually obtained when the deposition temperature was below 750 C. Large-grain, continuous, silicon thin films with an area of 10 cm² were grown on glass substrates at temperatures around the softening points of the glass. The growth of silicon on glass can be explained on the basis that the presence of aluminium and magnesium in the solution reduces SiO₂ and exposes silicon on the glass surface. The silicon-rich surface improves the wetting of the glass by the solution and acts as seeding sites for silicon nucleation. The periodic-regrowth technique was used to improve the quality of the polycrystalline silicon thin films deposited on the glass substrates. Periodic repetition of the melt-back and regrowth procedures removed the small-grained crystals, suppressed the rapid growth of crystals perpendicular to the substrate and enhanced the growth of slower-growing crystals in the lateral direction. This process markedly improved the smoothness, the grain size, the crystal quality and the (1 1 1) preferred orientation of the silicon thin films. Diode characteristics were obtained for p-n junction devices made on these polycrystalline silicon thin films deposited on glass substrates.     

Quality improvement of organic thin films deposited on vibrating substrates

Most of the Organic Light-Emitting Diodes (OLEDs) have a multilayered structure composed of functional organic layers sandwiched between two electrodes. Thin films of small molecules are generally deposited by thermal evaporation onto glass or other rigid or flexible substrates. The interface state between two organic layers in OLED device depends on the surface morphology of the layers and affects deeply the OLED performance. The morphology of organic thin films depends mostly on substrate temperature and deposition rate. Generally, the control of the substrate temperature allows improving the quality of the deposited films. For organic compounds substrate temperature cannot be increased too much due to their poor thermal stability. However, studies in inorganic thin films indicate that it is possible to modify the morphology of a film by using substrate vibration without increasing the substrate temperature. In this work, the effect of the resonance vibration of glass and silicon substrates during thermal deposition in high vacuum environment of tris(8-quinolinolate)aluminum(III) (Alq₃) and N,N′-Bis(naphthalene-2-yl)-N,N′-bis(phenyl)-benzidine (β-NPB) organic thin films with different deposition rates was investigated. The vibration used was in the range of hundreds of Hz and the substrates were kept at room temperature during the process. The nucleation and subsequent growth of the organic films on the substrates have been studied by atomic force microscopy technique. For Alq₃ and β-NPB films grown with 0.1 nm/s as deposition rate and using a frequency of 100 Hz with oscillation amplitude of some micrometers, the results indicate a reduction of cluster density and a roughness decreasing. Moreover, OLEDs fabricated with organic films deposited under these conditions improved their power efficiency, driven at 4 mA/cm², passing from 0.11 lm/W to 0.24 lm/W with an increase in their luminance of about 352 cd/m² corresponding to an increase of about 250% in the luminance with respect to the same OLEDs fabricated in the same way and with the same conditions without substrate vibration.     

Crystallization of β-FeSi2 droplets on silicon substrates by room-temperature pulsed laser deposition

This paper reports the fabrication process of β-FeSi₂ droplets on silicon substrates at room temperature by ArF excimer pulsed laser deposition (PLD). The chemical treatment of substrate could compensate the thermal treatment of the deposited droplets. Observations with the transmission electron microscopy revealed that the crystallization of droplet began from the surface of droplet rather than from the interface between the melt and the substrate.     

Atomic layer deposition of SiO2 thin films using tetrakis(ethylamino)silane and ozone

We examined the atomic layer deposition (ALD) of silicon dioxide thin films on a silicon wafer by alternating exposures to tetrakis(ethylamino)silane [Si(NHC2H5)4] and O3. The growth kinetics of silicon oxide films was examined at substrate temperatures ranging from 325 to 514 degrees C. The deposition was governed by a self-limiting surface reaction, and the growth rate at 478 degrees C was saturated at 0.17 nm/cycle for Si(NHC2H5)4 exposures of 2 x 10(6) L (1 L = 10(-6) Torr x s). The films deposited at 365-404 degrees C exhibited a higher deposition rate of 0.20-0.21 nm/cycle. However, they contained impurities, such as carbon and nitrogen, and showed poor film qualities. The concentration of impurities decreased with increasing substrate temperature. It was found that the films deposited in the high-temperature regime (478-514 degrees C) showed excellent physical and electrical properties equivalent to those of LPCVD films.     

Temperature behaviour of the substrate surface during growth of nanocrystalline silicon carbide films by deposition of 120 eV carbon and silicon ions

Changes in the temperature of nanocrystalline SiC film surface were measured during film growth by direct deposition of carbon and silicon ions onto substrates at ∼800 °С. It has been found that the initial stage of the film growth is characterized by uncontrolled variations of the surface temperature, which are observed for constant values of the deposition parameters. The energy components of the temperature balance on the film surface during its growth under conditions of direct ion deposition are analyzed. It is shown that magnitudes of temperature variations depend on the energy and current density of the deposited ions and on the ratio of the emissivity coefficients of the substrate material and silicon carbide. If this ratio is 1:6, the temperature rise at the initial growth stage reaches 160 °С when using 120 eV ion energy. For ion deposition onto silicon carbide substrates these uncontrolled temperature deviations at the initial stage of film growth were not observed.     

Electrochemical corrosion behavior of amorphous carbon nitride thin films

The corrosion behavior along with biocompatibility and mechanical properties plays an important role in determining of biomedical implants feasibility. Diamond-like carbon seems to be the promising material in which all these three requirements can be achieved. In this study nitrogen doped amorphous carbon (a-C:N) films were deposited on silicon and medical CoCrMo alloy substrates by vacuum glow discharge sputtering technique using different deposition conditions from graphite target. Potentiodynamic polarization tests were employed to assess the corrosion performances of the films at room temperature in 0.89 wt. % NaCl solution. The influence of substrate bias on the electrochemical corrosion behavior was investigated. The highest value off E_corr for CoCrMo substrate was measured on the coating deposited with substrate bias around −0.6 kV. The shift of E_corr to more positive values was about 350 mV.     

Low-temperature plasma-enhanced chemical vapor deposition of tungsten and tungsten nitride

Tungsten and tungsten nitride layers have been deposited by plasma-enhanced chemical vapor deposition (PECVD). Tungsten layers deposited at low deposition temperatures T150 °C using this method showed good uniformity over dielectric and silicon substrate areas. As the deposition temperature decreased, the silicon consumed during the deposition reaction decreased, at T150 °C no silicon consumption was measurable. PECVD tungsten nitride layers were deposited directly on oxidized silicon substrates with no requirement for a nucleation layer. As the NH₃ flow rate was increased, whilst maintaining all other parameters constant, deposited layers were found to change from metal tungsten to tungsten-rich amorphous layer to W₂N. The resistivity of the layers was found to be high compared to published literature for higher-temperature deposited layers. The high resistivity is attributed to the incorporation of fluorine into the layer at low deposition temperatures. A deposition process was established for smooth amorphous tungsten-rich W _x N layers at 150 °C.     

Growth of textured LiNbO3 thin film on Si (111) substrate by pulsed laser deposition

Highly c-axis oriented LiNbO₃ thin films have been deposited on Si (111) substrates by pulsed laser deposition. A stoichiometric sintered LiNbO₃ is used as the target. The c-axis orientation and stoichiometry of LiNbO₃ films are strongly influenced by substrate temperature and oxygen pressure. The substrate temperature 600 °C and oxygen pressure 20–30 Pa are found to be optimized parameters for the growth of textured film. The results showed that the size and the density of droplets decreased with increasing substrate temperature, and droplets would disappear when substrate temperature is increased above 600 °C. The surface microstructures of LiNbO₃ films under optimized conditions are fine, uniform and dense. The AFM images ensured that the as-grown films are good enough to be integrated with the semiconductor devices.     

硅碳氧薄膜光学性能研究

硅碳氧(SiCO)薄膜是一种三元玻璃状化合物材料,具有热稳定性好、能带宽、折射率大、硬度高等特性,是一种具有潜在应用价值的新颖光学薄膜材料。本文采用射频磁控溅射技术在Si(100)及K9玻璃上制备了硅碳氧薄膜。利用椭圆偏振仪、紫外/可见/近红外光度计及X射线光电子能谱测试表征了薄膜的光学性能及薄膜组分。研究发现,通过改变基片温度、工作压强及溅射功率等工艺参数,所制备的硅碳氧薄膜均具有高折射率(大于1.80),相比之下,K9玻璃基硅碳氧薄膜的折射率有着更大的变化范围(1.84~2.20)。通过对K9玻璃基硅碳氧薄膜的光学透射性能研究表明,以硅碳氧陶瓷作为溅射靶材,采用射频磁控溅射技术在K9玻璃基上可以制备出,在可见光及近红外区域有着较好光学透射性能,平均透过率能到达83%的硅碳氧薄膜。