High-cycle fatigue of single-crystal silicon thin films
TL;DR: In this paper, 12 thin-film single crystal silicon specimens were tested to failure in a controlled air environment (30/spl +mn/0.1/spl deg/C, 50/spl plusmn/2% relative humidity). Damage accumulation and failure of the notched cantilever beams were monitored electrically during the fatigue life test.
Abstract: When subjected to alternating stresses, most materials degrade, e.g., suffer premature failure, due to a phenomenon known as fatigue. It is generally accepted that in brittle materials, such as ceramics, fatigue can only take place in toughened solids, i.e., premature fatigue failure would not be expected in materials such as single crystal silicon. The results of this study, however, appear to be at odds with the current understanding of brittle material fatigue. Twelve thin-film (/spl sim/20 /spl mu/m thick) single crystal silicon specimens were tested to failure in a controlled air environment (30/spl plusmn/0.1/spl deg/C, 50/spl plusmn/2% relative humidity). Damage accumulation and failure of the notched cantilever beams were monitored electrically during the "fatigue life" test. Specimen lives ranged from about 10 s to 48 days, or 1/spl times/106 to 1/spl times/1011 cycles before failure over stress amplitudes ranging from approximately 4 to 10 GPa. A variety of mechanisms are discussed in light of the fatigue life data and fracture surface evaluation.
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TL;DR: In this article, a study of high-cycle fatigue in 2um thick structural films of n+-type, polycrystalline silicon for MEMS applications was made and the results showed that high cycle fatigue was present in 2.
237 citations
TL;DR: It is demonstrated how electrolyte additives can heal electrode cracks and provide strategies to enhance the fracture resistance in future lithium-ion batteries from surface chemical, electrochemical and material science perspectives.
Abstract: Long-term durability is a major obstacle limiting the widespread use of lithium-ion batteries in heavy-duty applications and others demanding extended lifetime. As one of the root causes of the degradation of battery performance, the electrode failure mechanisms are still unknown. In this paper, we reveal the fundamental fracture mechanisms of single-crystal silicon electrodes over extended lithiation/delithiation cycles, using electrochemical testing, microstructure characterization, fracture mechanics and finite element analysis. Anisotropic lithium invasion causes crack initiation perpendicular to the electrode surface, followed by growth through the electrode thickness. The low fracture energy of the lithiated/unlithiated silicon interface provides a weak microstructural path for crack deflection, accounting for the crack patterns and delamination observed after repeated cycling. On the basis of this physical understanding, we demonstrate how electrolyte additives can heal electrode cracks and provide strategies to enhance the fracture resistance in future lithium-ion batteries from surface chemical, electrochemical and material science perspectives.
202 citations
TL;DR: In this article, the development of tensile and bending testing techniques using microelectromechanical systems (MEMS) along with the experimental results on nanoscale aluminum specimens are discussed.
Abstract: Thin films at the micrometer and submicrometer scales exhibit mechanical properties that are different than those of bulk polycrystals. Industrial application of these materials requires accurate mechanical characterization. Also, a fundamental understanding of the deformation processes at smaller length scales is required to exploit the size and interface effects to develop new and technologically attractive materials. Specimen fabrication, small-scale force and displacement generation, and high resolution in the measurements are generic challenges in microscale and nanoscale mechanical testing. In this paper, we review small-scale materials testing techniques with special focus on the application of microelectromechanical systems (MEMS). Small size and high force and displacement resolution make MEMS suitable for small-scale mechanical testing. We discuss the development of tensile and bending testing techniques using MEMS, along with the experimental results on nanoscale aluminum specimens.
191 citations
TL;DR: In this article, a 2-μm-thick polycrystalline silicon cantilever beams exhibited a time-delayed failure that was accompanied by a continuous increase in the compliance of the specimen.
Abstract: To evaluate the long-term durability properties of materials for microelectromechanical systems (MEMS), the stress-life ( S / N ) cyclic fatigue behavior of a 2-μm thick polycrystalline silicon film was evaluated in laboratory air using an electrostatically actuated notched cantilever beam resonator. A total of 28 specimens were tested for failure under high frequency (∼40 kHz) cyclic loads with lives ranging from about 10 s to 34 days (3×10 5 to 1.2×10 11 cycles) over fully reversed, sinusoidal stress amplitudes varying from ∼2.0 to 4.0 GPa. The thin-film polycrystalline silicon cantilever beams exhibited a time-delayed failure that was accompanied by a continuous increase in the compliance of the specimen. This apparent cyclic fatigue effect resulted in an endurance strength, at greater than 10 9 cycles, of ∼2 GPa, i.e. roughly one-half of the (single cycle) fracture strength. Based on experimental and numerical results, the fatigue process is attributed to a novel mechanism involving the environmentally-assisted cracking of the surface oxide film (termed reaction-layer fatigue). These results provide the most comprehensive, high-cycle, endurance data for designers of polysilicon micromechanical components available to date.
170 citations
TL;DR: A fixed-grip fracture mechanics microspecimen was developed but could find no evidence of static stress corrosion cracking in polysilicon, and the environmental sensitivity of the fatigue resistance was investigated under cyclic loading.
Abstract: In the absence of a corrosive environment, brittle materials such as silicon should be immune to cyclic fatigue However, fatigue effects are well known in micrometer-sized polycrystalline silicon (polysilicon) samples tested in air To investigate the origins of this phenomenon in polysilicon, we developed a fixed-grip fracture mechanics microspecimen but could find no evidence of static stress corrosion cracking The environmental sensitivity of the fatigue resistance was also investigated under cyclic loading For low-cycle fatigue, the behavior is independent of the ambient conditions, whether air or vacuum, but is strongly influenced by the ratio of compressive to tensile stresses experienced during each cycle The fatigue damage most likely originates from contact stresses at processing-related surface asperities; subcritical crack growth then ensues during further cyclic loading The lower far-field stresses involved in high-cycle fatigue induce reduced levels of fatigue damage Under these conditions, a corrosive ambient such as laboratory air exacerbates the fatigue process Without cyclic loading, polysilicon does not undergo stress corrosion cracking
155 citations
References
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Book•
01 Jan 1985
TL;DR: In this paper, the physical properties of crystals systematically in tensor notation are presented, presenting tensor properties in terms of their common mathematical basis and the thermodynamic relations between them.
Abstract: First published in 1957, this classic study has been reissued in a paperback version that includes an additional chapter bringing the material up to date. The author formulates the physical properties of crystals systematically in tensor notation, presenting tensor properties in terms of their common mathematical basis and the thermodynamic relations between them. The mathematical groundwork is laid in a discussion of tensors of the first and second ranks. Tensors of higher ranks and matrix methods are then introduced as natural developments of the theory. A similar pattern is followed in discussing thermodynamic and optical aspects.
8,520 citations
"High-cycle fatigue of single-crysta..." refers background in this paper
...Typical fracture surfaces of specimens with short lives ( 10 cycles) and longer lives ( 10 cycles) re shown in Fig....
[...]
Book•
24 Sep 1993TL;DR: In this article, the authors present a unified continuum, microstructural and atomistic treatment of modern day fracture mechanics from a materials perspective, focusing on the basic elements of bonding and microstructure that govern the intrinsic toughness of ceramics.
Abstract: This is an advanced text for higher degree materials science students and researchers concerned with the strength of highly brittle covalent–ionic solids, principally ceramics. It is a reconstructed and greatly expanded edition of a book first published in 1975. The book presents a unified continuum, microstructural and atomistic treatment of modern day fracture mechanics from a materials perspective. Particular attention is directed to the basic elements of bonding and microstructure that govern the intrinsic toughness of ceramics. These elements hold the key to the future of ceramics as high-technology materials - to make brittle solids strong, we must first understand what makes them weak. The underlying theme of the book is the fundamental Griffith energy-balance concept of crack propagation. The early chapters develop fracture mechanics from the traditional continuum perspective, with attention to linear and nonlinear crack-tip fields, equilibrium and non-equilibrium crack states. It then describes the atomic structure of sharp cracks, the topical subject of crack-microstructure interactions in ceramics, with special focus on the concepts of crack-tip shielding and crack-resistance curves, and finally deals with indentation fracture, flaws, and structural reliability.
3,550 citations
TL;DR: In this paper, a generalized expression for ν has been derived for arbitrary orientations of cubic semiconductor crystals, and the variation of E, ν, and E/(1−ν) for directions within the important {111, {100, and {110} planes is examined.
Abstract: Theoretical estimates or experimental determinations of stress fields associated with semiconductor devices are generally simplified with the aid of two elastic constants, Young's modulus E and Poisson's ratio ν. In this paper, a generalized expression for ν has been derived for arbitrary orientations of cubic semiconductor crystals, and the variation of E, ν, and E/(1‐ν) for directions within the important {111}, {100}, and {110} planes is examined. The results show that isotropic elasticity theory is exact for all directions within {111} planes and that the composite elastic constant E/(1‐ν) which frequently occurs in problems of practical interest is also invariant for all directions within {100} planes. Numerical values for the various elastic constants are tabulated for GaAs, GaP, Si, and Ge.
1,106 citations
"High-cycle fatigue of single-crysta..." refers background in this paper
...Typical fracture surfaces of specimens with short lives ( 10 cycles) and longer lives ( 10 cycles) re shown in Fig....
[...]
TL;DR: In this article, the authors used fracture mechanics techniques to measure the crack velocities in water as a function of applied stress intensity factor and temperature, and apparent activation energies for crack motion were obtained.
Abstract: Stress corrosion cracking of six glasses was studied using fracture mechanics techniques. Crack velocities in water were measured as a function of applied stress intensity factor and temperature, and apparent activation energies for crack motion were obtained. Data were consistent with the universal fatigue curve for static fatigue of glass, which depended on glass composition. Of the glasses tested, silica glass was most resistant to static fatigue, followed by the low-alkali aluminosilicate and borosilicate glasses. Sodium was detrimental to stress corrosion resistance. The crack velocity data could be explained by the Charles and Hillig theory of stress corrosion. It is probable that stress corrosion of glass is normally caused and controlled by a chemical reaction between the glass and water.
920 citations
TL;DR: In this article, the authors examined the mechanisms of fatigue-crack propagation with particular emphasis on the similarities and differences between cyclic crack growth in ductile materials such as metals, and corresponding behavior in brittle materials, such as intermetallics and ceramics.
Abstract: The mechanisms of fatigue-crack propagation are examined with particular emphasis on the similarities and differences between cyclic crack growth in ductile materials, such as metals, and corresponding behavior in brittle materials, such as intermetallics and ceramics. This is achieved by considering the process of fatigue-crack growth as a mutual competition between intrinsic mechanisms of crack advance ahead of the crack tip (e.g., alternating crack-tip blunting and resharpening), which promote crack growth, and extrinsic mechanisms of crack-tip shielding behind the tip (e.g., crack closure and bridging), which impede it. The widely differing nature of these mechanisms in ductile and brittle materials and their specific dependence upon the alternating and maximum driving forces (e.g., ΔK andK
max) provide a useful distinction of the process of fatigue-crack propagation in different classes of materials; moreover, it provides a rationalization for the effect of such factors as load ratio and crack size. Finally, the differing susceptibility of ductile and brittle materials to cyclic degradation has broad implications for their potential structural application; this is briefly discussed with reference to lifetime prediction.
803 citations
"High-cycle fatigue of single-crysta..." refers methods in this paper
...RESULTS AND DISCUSSION Twelve thin-film (20 m thick) single crystal silicon specimens were tested to failure in a controlled air environment [30 0.1 C, 50 2% relative humidity (RH)] using the sample geometry and testing procedure described above....
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