Local Vibration Modes of N-H Related Complexes in GaAsN Grown by Chemical Beam Epitaxy

We have studied the small clusters of silicon and carbon interstitials by ab initio supercell calculations in 4H-SiC. We found that silicon interstitials can form stable and electrically active complexes with each other or with a carbon interstitial. Local vibration modes and ionization energies were also calculated in order to help the identification of the defects. We propose that silicon interstitials can emit from these clusters at relatively high temperatures, which may play an important role in the formation of the DI center.

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Silicon-Hydrogen Bonds in Boron and Phosphorous Doped Polycrystalline Silicon Thin Films

MRS Proceedings ◽

10.1557/proc-808-a4.4 ◽

2004 ◽

Vol 808 ◽

Cited By ~ 1

Author(s):

R. Saleh ◽

N. H. Nickel

Keyword(s):

Binding Energy ◽

Polycrystalline Silicon ◽

Binding Energies ◽

Vibration Modes ◽

Laser Crystallization ◽

Hydrogen Binding ◽

Local Vibration ◽

Silicon Thin Films ◽

The One ◽

Hydrogen Effusion

ABSTRACTHydrogen bonding in laser crystallized boron and phosphorous doped polycrystalline silicon is investigated using Raman spectroscopy and hydrogen effusion measurements. During laser crystallization the intensity of the local vibration modes near 2000 and 2100 cm−1 decreases. The intensity of vibration mode at 2000 cm−1 decreases faster than the one at 2100 cm−1. From H effusion measurements, the hydrogen density-of-states (H DOS) distribution is derived. For undoped amorphous silicon the H DOS exhibits two prominent peaks at hydrogen binding energies of E– μH = –1.1 and –1.5 eV. In B doped a-Si:H the peak at –1.1 eV is less pronounced while in P doped a-Si:H the H binding energy increases by about 0.1 eV. In all samples laser crystallization causes an increase of the H binding energy by about 0.2 – 0.3 eV. However, the peaks in the H DOS observed in B-doped samples are preserved during laser crystallization.

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Toward identifying crack-length-related resonances in acoustic emission waveforms for structural health monitoring applications

Structural Health Monitoring ◽

10.1177/1475921717707356 ◽

2017 ◽

Vol 17 (3) ◽

pp. 577-585 ◽

Cited By ~ 22

Author(s):

Md Yeasin Bhuiyan ◽

Jingjing Bao ◽

Banibrata Poddar ◽

Victor Giurgiutiu

Keyword(s):

Finite Element ◽

Acoustic Emission ◽

Fatigue Crack ◽

Structural Health Monitoring ◽

Crack Growth ◽

Health Monitoring ◽

Resonance Phenomenon ◽

Vibration Modes ◽

Local Vibration ◽

Structural Health

In this study, we focus on analyzing the acoustic emission waveforms of the fatigue crack growth despite the conventional statistics-based analysis of acoustic emission. The acoustic emission monitoring technique is a well-known approach in the non-destructive evaluation/structural health monitoring research field. The growth of the fatigue crack causes the acoustic emission in the material that propagates in the structure. The acoustic emission happens not only from the crack growth but also from the interaction of the crack tips during the fatigue loading in the structure. The acoustic emission waveforms are generated from the acoustic emission events; they propagate and create local vibration modes along the crack faces (crack resonance). In-situ fatigue and acoustic emission experiments were conducted to monitor the acoustic emission waveforms from the fatigue cracks. Several test specimens were used in the fatigue experiments, and corresponding acoustic emission waveforms were captured. The acoustic emission waveforms were analyzed and distinguished into three types based on the similar nature in both time and frequency domains. Three-dimensional harmonic finite element analyses were performed to identify the local vibration modes. The local crack resonance phenomenon has been observed from the finite element simulation that could potentially give the geometric information of the crack. The laser Doppler vibrometry experiment was performed to identify the crack resonance phenomenon, and the experimental results were used to verify the simulated results.

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