Crystal Wafer: May 2018

May 15, 2018

Resonance ultrasonic vibration diagnostics of elastic stress in full-size silicon wafers

A resonance vibration approach is developed to measure residual stress non-destructively in full-size multicrystalline silicon wafers used in solar cell manufacturing. This method is based on excitation of longitudinal resonance ultrasonic vibrations in the material using an external piezoelectric transducer combined with high-sensitive ultrasonic probe and data acquisition of the frequency response to make the method suitable for in-line diagnostics during wafer and cell manufacturing. Theoretical and experimental analysis of the vibration mode in single-crystal and multicrystalline silicon wafers is used to provide a benchmark reference analysis and validation of the approach.

Source:IOPscience

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May 8, 2018

Fabrication of microdomains at the +Z surface of near-stoichiometric lithium tantalate crystals

Scanning force microscopy is used to investigate microscale ferroelectric domains at the +Z surface of near-stoichiometric lithium tantalate (SLT) single crystals. Both line and lattice patterns of microdomains are fabricated at the +Z surface of SLT wafers, which are switched by scanning these wafers with the external field exceeding the coercive field. The +Z polar surface in these patterns is etched by a mixture of acid aqueous solution (HF : HNO3 = 1 : 1), which reveals the precise microdomain structure. The analysis of the experimental data indicates that the rearrangement of the ferroelectric domain structure occurs during the chemical etching process; the effect of both defect and crystal structure on the microdomain growth process is also discussed. The present results are helpful for us to realize the fabrication of the expected microdomain morphology.