Modification of Fracture Energy of Niobium/sapphire Interface By Impurity Doping

1996 ◽  
Vol 458 ◽  
Author(s):  
Hong Ji ◽  
Gary S. Was ◽  
J. Wayne Jones ◽  
Neville R. Moody
Keyword(s):  
Fracture Toughness ◽  
Fracture Energy ◽  
Physical Vapor Deposition ◽  
Interfacial Fracture ◽  
Interface Composition ◽  
Sapphire Substrates ◽  
Silver Sample ◽  
Impurity Doping ◽  
Interfacial Fracture Energy ◽  
Microscratch Test

ABSTRACTThe effect of interface composition on the fracture energy and fracture toughness of the niobium/sapphire system was studied. Niobium films with thickness of 100 nm were deposited on (0001) sapphire substrates by physical vapor deposition (PVD). The interface was doped with silver to reduce the interfacial cohesion. The amount of silver ranged from less than 2.1 monolayers to 6.4 monolayers as measured by Rutherford backscattering spectrometer (RBS). The microscratch test was used in determining the interfacial fracture energy and the interfacial fracture toughness. Both interfacial fracture energy Gc and fracture toughness Kc decrease non-linearly with the amount of silver, and level off for samples with larger silver thickness ( > 4.2 monolayers). The values of interfacial fracture energy range from 3.43 J/m2 - 9.20 J/m2 for the sample doped with 2.1 monolayer silver (sample B) to 0.05 J/m2 - 0.5 J/m2 for samples with silver levels above 4.2 monolayers (samples D and E). The corresponding fracture toughnesses are 0.80 MPa-m½ - 1.29 MPa-m½ for sample B and 0.09 MPa-m½ - 0.30 MPa-m½ for samples D and E.

Modified Decohesion Test (MDT) for Interfacial Fracture Toughness Measurement in Microelectronic/MEMS Applications

2002 ◽  
Author(s):  
Mitul B. Modi ◽  
Suresh K. Sitaraman
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Fracture Toughness ◽  
Energy Release ◽  
Physical Vapor Deposition ◽  
Interfacial Fracture ◽  
Interfacial Fracture Toughness ◽  
Testing Methods ◽  
Structural Variations ◽  
Metal Thin Film

Delamination of intrinsically or residually stressed thin films is commonly encountered in microelectronics and MEMS systems. Thin films typically accrue stresses through micro structural variations caused by physical vapor deposition, thermally induced stresses imposed due to thermal mismatch, and/or extrinsically introduced forces. These stresses can reach upwards of 1 GPa and can easily exceed the strength of the metal thin film interface. Knowledge of the interfacial fracture toughness (Γ) is necessary to predict if delamination will occur. However, measuring Γ is a challenge for thin film interfaces. Typical testing methods such as bimaterial cantilever, microscratch, peel, bulge, or edge lift-off are limited to organic films, cause complex stress fields, can only measure a single mode mix, or cannot achieve the large energy release rates typical of metal thin film interfaces. A new approach based on the decohesion test, called the modified decohesion test (MDT), eliminates these shortcomings of current testing methods. In this approach, a highly stressed super layer is used to drive delamination and “tune-in” the mode mix at the crack tip. Since the deformations remain elastic, a mechanics-based solution can be used to correlate test parameters to the energy release rate. Common IC fabrication techniques are used to prepare the sample and execute the test, thereby making the test compatible with current microelectronic or MEMS facilities. Varying the crack surface area rather than the energy in the super layer allows the ability to bound Γ using a single test wafer providing a 90% savings in resources and 95% savings in time. Other modifications allow application of the method to highly chemically reactive metals and decrease the sample preparation time. Design, preparation, and execution of the MDT are presented. Results of finite element models are used to validate the approach. Results are shown for a Ti/Al2O3 interface.

Estimation of the Interfacial Fracture Energy of Metal/Polymer System in Microelectronic Packaging

2001 ◽  
Vol 682 ◽  
Author(s):  
J.Y. Song ◽  
Jin Yu
Keyword(s):  
Fracture Energy ◽  
Power Density ◽  
Polymer System ◽  
Peel Test ◽  
Interfacial Fracture ◽  
Peel Strength ◽  
Rf Plasma ◽  
Plasma Power ◽  
Interfacial Fracture Energy ◽  
Elastoplastic Beam

ABSTRACTThe interfacial fracture energies of flexible Cu/Cr/Polyimide system were deduced from the T peel test. The T peel strength and peel angle were strongly affected by the metal thickness and the biased rf plasma power density of the polyimide pretreatment. The plastic bending works of metal and polyimide dissipated during peel test were estimated from the direct measurement of maximum root curvatures using the elastoplastic beam analysis. The interfacial fracture energy between Cr and polyimide increased with the rf plasma power density and saturated, but was pretty much independent of the metal film thickness and the peel angle.

Analytical Studies on Mixed-Mode Debonding along the FRP–Concrete Interface in the Peeling Test

2011 ◽  
Vol 268-270 ◽  
pp. 247-251 ◽  
Author(s):  
Hong Chang Qu ◽  
Sheng Li Zhang ◽  
Ling Ling Chen
Keyword(s):  
Fracture Energy ◽  
Interfacial Fracture ◽  
Opening Displacement ◽  
Flexural Strengthening ◽  
Linear Elastic ◽  
Peeling Test ◽  
Interfacial Fracture Energy ◽  
Set Up ◽  
Concrete Interface ◽  
Frp Sheet

The bonding of fiber reinforced polymer (FRP) strips and plates to the concrete structures has been found to be an effective technique for flexural strengthening. The FRP is then under both pulling and peeling forces, resulting in a combination of shear sliding and opening displacement along the FRP/concrete interface. A novel experimental set-up is studied that a peeling load is applied on the FRP sheet by a circular rod placed into the central notch of the beam. Based on the linear-elastic fracture mechanics approach, a theoretical analysis is conducted on specimens representing the peeling behavior. From the numerical analysis, the load–displacement curves, load–stiffness of FRP sheet curves, and load–fracture energy curves affected by different variables are discussed. The peel load is related to the FRP sheet stiffness and to the interfacial fracture energy. Therefore, only two material parameters, the interfacial fracture energy of FRP–concrete interface and stiffness of FRP sheets, are necessary to represent the interfacial fracture behavior. The theoretical load–deflection curves of specimens agree well with the corresponding experimental results in the literatures.

scholarly journals Prediction of Load Capacity Variation in FRP Bonded Concrete Specimens Using Brownian Motion

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Tayyebeh Mohammadi ◽  
Baolin Wan ◽  
Jian-Guo Dai ◽  
Chao Zhu
Keyword(s):  
Brownian Motion ◽  
Fracture Energy ◽  
Load Capacity ◽  
Concrete Strength ◽  
Experimental Tests ◽  
Interfacial Fracture ◽  
Concrete Surface ◽  
Concrete Members ◽  
Interfacial Fracture Energy ◽  
Mode Ii Loading

In wet lay-up process, dry fiber sheets are saturated with a polymer and applied to the concrete surface by hand. This causes relatively large variation in properties of the cured FRP composite material. It is hard to know the exact mechanical properties of the FRP constructed by wet lay-up process. In addition, the stiffness of FRP changes during debonding process due to different amount of concrete attached to the debonded FRP at different locations. It is also inevitable to have considerable variations in the strength of concrete. Therefore, the behaviour of FRP bonded concrete members varies among specimens even when the same materials are used. The variation of localized FRP stiffness and concrete strength can be combined in a single parameter as variation of the localized interfacial fracture energy. In an effort to effectively model the effects of the variation of interfacial fracture energy on the load versus deflection responses of FRP bonded concrete specimens subjected to Mode I and Mode II loading, a random white noise using a one-dimensional standard Brownian motion is added to the governing equations, yielding stochastic differential equations. By solving these stochastic equations, the bounds of load carrying capacity variation with 95% probability are found for different experimental tests.

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