Crystal orientation-dependent fatigue characteristics in micrometer-sized single-crystal silicon

Abstract

Repetitive bending fatigue tests were performed using five types of single-crystal silicon specimens with different crystal orientations fabricated from {100} and {110} wafers. Fatigue lifetimes in a wide range between 10 0 and 10 10 were obtained using fan-shaped resonator test devices. Fracture surface observation via scanning electron microscope (SEM) revealed that the {111} plane was the primary fracture plane. The crack propagation exponent n was estimated to be 27, which was independent of the crystal orientation and dopant concentration; however, it was dependent on the surface conditions of the etched sidewall. The fatigue strengths relative to the deflection angle were orientation dependent, and the ratios of the factors obtained ranged from 0.86 to 1.25. The strength factors were compared with those obtained from finite element method stress analyses. The calculated stress distributions showed strong orientation dependence, which was well-explained by the elastic anisotropy. The comparison of the strength factors suggested that the first principal stress was a good criterion for fatigue fracture. We include comparisons with specimens tested in our previous report and address the tensile strength, initial crack length, volume effect, and effects of surface roughness such as scallops.

Direct Observation of SEI Formation and Lithiation in Thin-Film Silicon Electrodes via in Situ Electrochemical Atomic Force Microscopy

“…The different crystal orientations can also be depicted in the Young’s modulus map of the pristine Si surface in Figure a–c. The polycrystalline Si electrode contains Si ⟨100⟩, ⟨110⟩, and ⟨111⟩ crystal orientations, providing different Young’s modulus values for each orientation. , The different orientations of the polycrystalline Si surface result in stiffness variation, displayed in Figure a–c, where it is recorded that higher particles comprise lower Young’s modulus values, in comparison to the interparticle areas. After the initial lithiation and the nonuniform expansion of the preferred particles, the lithiation continues mainly homogeneously, which can be indicated from the RMS values in Figure after 5000 s lithiation time.…”

Predicting strength distributions of MEMS structures using flaw size and spatial density

“…A disadvantage is that the small dimensions of MEMS can lead to specimen handling issues in strength and other mechanical testing. Innovative designs have largely overcome this disadvantage and enabled experimental measurements of elastic modulus 3,4 , fracture toughness 5 , fatigue lifetime 6 , and, especially, strength 7–17 . In many experiments, large numbers of MEMS-scale components have been measured with great precision, and an extensive review of MEMS strengths, including assessments of modulus and toughness, highlights these advances 18 .…”

Optical Sensor, Based on an Accelerometer, for Low-Frequency Mechanical Vibrations

“…For the structures under analysis, the maximum stress was less than 240 MPa, which exceeds 1010 cycles of life according to [30]. The maximum stress values obtained are under the ultimate stress of silicon.…”

“…The maximum operating cycles for the microstructure were estimated using a simulation of the first principal stress and were compared with the experimental results reported for silicon [30].…”