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1.
The oxidation of clean crystalline silicon surfaces is self-limiting at moderate oxygen pressures (10− 5 Pa) and temperatures (500 °C), forming 0.7-0.8 nm thick oxide layers. This study looks at the oxidation of a surface of a thin amorphous silicon film to establish if a similar mechanism is active in this case. We have devised a special experimental procedure to check the oxidation mechanism of thin amorphous silicon films. For the spectroscopic investigations we used photoemission with synchrotron radiation with the highest possible surface sensitivity and resolution. This permits a detailed decomposition of the Si 2p spectral details, using a mathematical decomposition procedure. The results clearly show that the oxidation mechanism of the surface of an amorphous silicon film under similar conditions is severely hindered compared to cases of crystalline substrates, indicating less reactivity at the surface and less transport of oxygen into the amorphous material.  相似文献   

2.
Surface effects are important to predict the mechanical behavior of nanostructures. In this paper, the wrinkling of a stiff thin film bonded to a compliant substrate is studied using an energy method accounting for surface elasticity and residual surface tension. The wavelength, critical buckling strain and amplitude are obtained analytically. These results provide valuable guide to the precise design and control of the wrinkling profile in many applications ranging from stretchable electronics to micro/nano scale surface patterning and precision metrology.  相似文献   

3.
C.K. Chung  B.H. Wu 《Materials Letters》2009,63(27):2369-2372
Effects of an amorphous silicon underlayer on the evolution of microstructure and hardness of an amorphous carbon film annealed at 900 °C for 0.5-1.5 h were investigated. The two-layer carbon/silicon film after annealing resulted in higher sp2/sp3 bonding ratio but lower hardness reduction compared to the single carbon film at the same total film thickness. The improved hardness reduction of the high-temperature annealed carbon film is attributed to the formation of polycrystals of the amorphous silicon together with the residual compressive stress of the two-layer C/Si films.  相似文献   

4.
Large grained polycrystalline silicon thin films have been prepared by low-temperature solid phase crystallisation of sputter-deposited hydrogenated amorphous silicon (a-Si:H), with relatively short processing times, and a considerably low thermal budget. Various a-Si:H samples, deposited under different conditions and with varying hydrogen concentrations and hydrogen bonding configurations, were simultaneously annealed. Only a particular set of deposition conditions led to crystallisation. The a-Si:H thin film which was successfully crystallised was prepared in an argon-hydrogen mixture, in which the last few minutes of film deposition occurred in a hydrogen-rich atmosphere. For that film, the hydrogen concentration profile resulted in a much higher hydrogen content on the sample surface than in the bulk, and H-Si bonds were predominantly of the weak type. Crystallisation was accomplished by low-temperature stepwise annealing from 200°C to 600°C at 100°C steps, with samples being cooled down to room-temperature between each annealing step. This resulted in large grained (> 10 μm range) polycrystalline silicon after the 600°C annealing step for a 1.1 μm thick sample. Fourier transform infrared (FTIR) spectroscopy, elastic recoil detection analysis (ERDA) and scanning electron microscopy (SEM) techniques were used to analyse samples before and after crystallisation.  相似文献   

5.
Stresses in thin films or coatings control the reliability of the thin film/substrate structure. By considering a circular thin film/substrate system subjected to gradient temperature, we derive relations between the non-uniform stresses in film and temperature, and between the non-uniform system curvatures and temperature. These relations featured a “local” part that involves a direct dependence of the stress or curvature components on the temperature at the same point, and a “non-local” part which reflects the effect of temperature of other points on the location of scrutiny. Furthermore, the deformation bifurcation behavior of the thin film/substrate system is analyzed. As the thermo-mismatch strain in the thin film increases, the system may transit to a biaxial curvature state (non-spherical deformation), in other words, the bifurcation of curvature will occur.  相似文献   

6.
T. Fu  Y. Zheng  Y.G. Shen 《Materials Letters》2008,62(17-18):2685-2687
Amorphous carbon nitride (CNx, x = 0.05) films were reactively sputtered on Si(100) substrate, and the interface structure was studied by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). In cross-sectional TEM a gray interlayer about 5 nm thick between the bulk CNx film and silicon substrate is observed, and the interface is dense. A little Si impurity (< 1 at.%) is revealed in the films deposited for short time (7 s and 17 s) by XPS measurement. The in-depth XPS analyses indicate that there exists an interlayer with Si impurity above, and a sub-surface layer with C and N below the original surface of silicon substrate. The two layers have different chemical composition and bonding state.  相似文献   

7.
Fourier transform infrared absorption spectroscopy (FTIR), optical emission spectroscopy (OES), self-bias voltage and plasma impedance controls were applied as in situ process diagnostics during the deposition of amorphous silicon thin-films. The diagnostic abilities of OES and FTIR are compared. The FTIR in-situ direct measurement of silane concentration in exhaust line is more precise than OES control. All in situ process diagnostics clearly indicates the inconsistency of plasma properties and therefore of deposition conditions. The drifts are comparable with the film deposition time. The FTIR measurement of reactant concentration in the process chamber evidence that the strong silane concentration drop (about 50%) in a plasma is the cause of the short-term drift of OES signals (SiH? emission), plasma impedance and self-bias voltage signals. The influences of the deposition chamber geometry and technological parameters on process drifts are considered. The decrease of the gas residence time in the reactor leads to a decrease of Initial Transient State phenomena. Finally, the improvement of solar cell performance based on thin silicon films is demonstrated when drifts are reduced.  相似文献   

8.
This paper presents the study on characterizing the mechanical and interfacial properties of ruthenium dioxide (RuO2) film on silicon substrate using nanoindentation tests. RuO2 film is deposited by DC reactive magnetron sputtering; the structure and morphology of the film are characterized using X-ray diffraction and scanning electron microscopy, and elastic modulus and hardness are determined by nanoindentation with a standard Berkovich indenter and found to be 232.74 ± 22.03 GPa and 20.43 ± 2.37 GPa, respectively. In addition, the interfacial adhesion properties of RuO2 film on Si substrate are studied. Spontaneous interfacial delamination is induced by indentations with wedge (90° and 120°) and conical indenter tips. The relationship between the indentation load-displacement (P-h) curves and the interfacial crack initiation and propagation are analyzed by combining FIB sectioning and SEM imaging. Through this analysis, the interface toughness of as-deposited RuO2 film is found to be 0.046 ± 0.003 J/m2 for 90° wedge indentation, 0.050 ± 0.004 J/m2 for 120° wedge indentation, and 0.051 ± 0.003 J/m2 for conical indentation.  相似文献   

9.
X-ray diffraction analysis of GaSe thin films used in the present investigation showed that the as-deposited and the one deposited at higher substrate temperature are in amorphous and polycrystalline state, respectively. The alternating current (ac) conduction properties of thermally evaporated films of GaSe were studied ex situ employing symmetric aluminium ohmic electrodes in the frequency range of 120-105 Hz at various temperature regimes. For the film deposited at elevated substrate temperature (573 K) the ac conductivity was found to increase with improvement of its crystalline structure. The ac conductivity (σac) is found to be proportional to (ωs) where s < 1. The temperature dependence of ac conductivity and the parameter, s, is reasonably well interpreted by the correlated barrier-hopping (CBH) model. The maximum barrier heights Wm calculated from ac conductivity measurements are compared with optical studies of our previous reported work for a-GaSe and poly-GaSe thin films. The distance between the localized centres (R), activation energy (ΔEσ) and the number of sites per unit energy per unit volume N(EF) at the Fermi level were evaluated for both a-GaSe and poly-GaSe thin films. Goswami and Goswami model has been invoked to explain the dependence of capacitance on frequency and temperature.  相似文献   

10.
The structure and spectroscopic properties of nano-structured silicon carbide (SiC) thin films were studied for films obtained through deposition of decomposed ethylene (C2H4) on silicon wafers via hot filament chemical vapor deposition method at low temperature followed by annealing at various temperatures in the range 300-700 °C. The prepared films were analyzed with focus on the early deposition stage and the initial growth layers. The analysis of the film's physics and structural characteristics was performed with Fourier transform infrared spectroscopy and Raman spectroscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy, and X-ray diffraction. The conditions for forming thin layer of cubic SiC phase (3C-SiC) are found. X-ray diffraction and Raman spectroscopy confirmed the presence of 3C-SiC phase in the sample. The formation conditions and structure of intermediate SiC layer, which reduces the crystal lattice mismatch between Si and diamond, are essential for the alignment of diamond growth. This finding provides an easy way of forming SiC intermediate layer using the Si from the substrate.  相似文献   

11.
Thin (1 μm) a-Si:H films have been deposited on glass at high-deposition rate (8 nm/s) and high substrate temperature (400 °C) by the expanding thermal plasma technique (ETP). After a Solid Phase Crystallization treatment at 650 °C for 10 h, many crystal grains are found to extend over the entire thickness (1 μm) of the polycrystalline silicon (poly-Si) films. This result indicates that the scalable, high-deposition rate ETP method can contribute to increase the potential for a widespread diffusion of poly-Si based thin film solar cells on glass.  相似文献   

12.
Quantitative estimation of the specific contact resistivity and energy barrier at the interface between transparent conducting oxide (TCO) and hydrogenated p-type amorphous silicon carbide (a-Si1 − xCx:H(p)) was carried out by inserting an interfacial buffer layer of hydrogenated p-type microcrystalline silicon (μc-Si:H(p)) or hydrogenated p-type amorphous silicon (a-Si:H(p)). In addition, superstrate configuration p-i-n hydrogenated amorphous silicon (a-Si:H) solar cells were fabricated by plasma enhanced chemical vapor deposition to investigate the effect of the inserted buffer layer on the solar cell device. Ultraviolet photoelectron spectroscopy was employed to measure the work functions of the TCO and a-Si1 − xCx:H(p) layers and to allow direct calculations of the energy barriers at the interfaces. Especially interface structures were compared with/without a buffer which is either highly doped μc-Si:H(p) layer or low doped a-Si:H(p) layer, to improve the contact properties of aluminum-doped zinc oxide and a-Si1 − xCx:H(p). Out of the two buffers, the superior contact properties of μc-Si:H(p) buffer could be expected due to its higher conductivity and slightly lower specific contact resistivity. However, the overall solar cell conversion efficiencies were almost the same for both of the buffered structures and the resultant similar efficiencies were attributed to the difference between the fill factors of the solar cells. The effects of the energy barrier heights of the two buffered structures and their influence on solar cell device performances were intensively investigated and discussed with comparisons.  相似文献   

13.
W.J. Zheng  M.H. Huang 《Thin solid films》2012,520(7):2841-2845
The possibility of the use of polydimethylsiloxane to align liquid crystals is studied. The polydimethylsiloxane thin films coated on glass substrates exhibit a very low surface free energy, and are found to be capable of vertical liquid crystal alignment. Comparing to thin films made using a typical polyimide polydimethylsiloxane films possess a more stable surface energetic state. The pretilt angle of the calamitic liquid crystal molecules sandwiched between the silicon elastomer thin films was virtually 90°, and the molecular tilt can be maintained in a wide temperature range. Liquid crystal sandwiched between the silicon-based polymer thin films can operate in the in-plane-switching mode.  相似文献   

14.
SmS optical thin films were deposited on the surface of ITO glass with an electrodeposition method using aqueous solution containing SmCl3·6H2O and Na2S2O3·5H2O. The phase composition was analyzed by X-ray diffraction (XRD) and microstructure of the film was characterized by atomic force microscope (AFM). It is showed that SmS thin film could be obtained in the solution with n(Sm)/n(S) = 1:4, pH = 4.0 and annealing in Ar atmosphere at 200 °C for 0.5 h. The as-prepared thin films on the ITO glass exhibit a dense microstructure. The band gap of the thin film has been found to be 3.6 eV.  相似文献   

15.
This paper introduces the homogeneously aligned liquid crystal (LC) display using ion beam (IB) bombardment of a new silicon oxynitride (SiON) alignment layer for the first time. The pretilt angle was shown to be a function of the IB incident energy, and possible mechanisms of LC alignment were investigated with physical and chemical methods. An X-ray photoelectron spectroscopy analysis showed that the LC alignment on the IB-bombarded SiON inorganic surface was due to the reformation of Si–O bonds as a major factor. The electro-optical characteristics were comparable to those of rubbed polyimide films.  相似文献   

16.
Polarized infrared attenuated total reflection (ATR) with Otto configuration was employed to access the surface phonon polariton (SPP) characteristics of wurtzite aluminium nitride (AlN) thin film grown on sapphire (Al2O3) substrate. The surface and guided wave polariton dispersion curves for the studied structure were derived by taking into account thin film and substrate anisotropy. From the p-polarized ATR spectrum, one prominent peak corresponds to the SPP mode of AlN thin film was clearly observed at 824 cm−1. In addition, four guided wave modes were also detected at 467, 593.5, 633.5 and 668 cm−1. For the s-polarized ATR spectrum, five pronounced dips associated to the guided wave modes were detected. The obtained results were in good agreement with the ATR spectra calculated based on the standard transfer matrix formulation. The origin of the observed ATR dips were verified from the dispersion curves simulated based on air/AlN epilayer/AlN buffer layer/Al2O3 model.  相似文献   

17.
The depth and spacing of cracks in a tensile residual stressed thin film bonded on a brittle substrate are analyzed thermodynamically using the minimum energy theorem on the basis that the film has the same mechanical properties as the substrate. The results show that the cracks penetrate into the substrate. Simple and approximate relationships between three dimensionless parameters, i.e., the normalized crack depth and spacing, and the cracking resistance number, are derived, which determine the fracture behavior of the film.  相似文献   

18.
The effect of hydrogen on the interface fracture toughness of two nano-film/substrate structures, Ni/Si and Cu/Si, were evaluated using four-point bend specimens with and without hydrogen charging. Hydrogen typically decreases the fracture toughness of materials. However, we found in this study that the interfacial toughness between the Ni film and the Si substrate increased due to the presence of hydrogen, while that of Cu/Si decreased. Nanoindentation experiments for the Ni and Cu films revealed that local plasticity in the Ni and Cu films is promoted by the charged hydrogen. The critical stress intensity at the Ni/Si interface crack considering the plasticity of Ni, namely the true fracture toughness, is scarcely influenced by the existence of hydrogen. The apparent increase in fracture toughness of the Ni/Si interface is due to the large stress relaxation near the crack tip caused by softening due to the presence of hydrogen. Although the promotion of plastic deformation of Cu relaxes the stress intensity at the Cu/Si interface crack, the apparent interfacial toughness still decreases because of the significant decrease in the true toughness due to the presence of hydrogen.  相似文献   

19.
In order to develop a colored mirror with hydrophilicity, TiO2 films are deposited on the Cr and amorphous-TiO2 substrate. In TiO2/Cr, a mixed phase comprising of anatase and rutile is formed. In TiO2/amorphous-TiO2/Cr, pure anatase phase is obtained. The amorphous-TiO2 film as interlayer tends to induce micro-columnar-shaped anatase phase. The formation of anatase phase leads to an abrupt decrease of the contact angle by UV-irradiation. Hydrophilic to hydrophobic reconversion by electron-hole recombination is retarded, which seems to be due to pure anatase phase without rutile phase.  相似文献   

20.
A detailed study on the mechanical, structural and surface characteristics of nanocrystalline TiB2 films deposited on Si-100 substrates by direct current (DC) magnetron sputtering was carried out. X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), nanoindentaion and X-ray diffraction (XRD) studies on these films were performed. Magnetron sputtered titanium diboride coatings had a maximum hardness of 36 GPa and elastic modulus of 360 GPa. From the XRD analyses, the films were found to grow in (00l) direction-oriented perpendicular to the substrate. The AFM analysis of the films showed the variation of grain size between 30 and 50 nm. The high-resolution AFM images revealed arrangements of atoms resembling lattice and the interplanar spacings measured on the image also showed the orientation of grains in the (001) direction. Nanoindentation studies at very shallow depths showed a continuous increase of hardness and modulus with indentation depth up to 40 nm due to tip blunting and presence of oxides on the film surface (confirmed from the XPS study). The elastic recovery was approximately 69% for 100 nm depth whereas it was 52% for 1000 nm depth.  相似文献   

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