Qualitative and quantitative bubbles defects analysis in undoped and Ti-doped sapphire crystals grown by Czochralski technique

• Undoped and Ti-doped sapphire crystals were grown from the by Czochralski technique.
• The bubbles sizes and their distribution are strongly connected to the pulling rate and rotation rate.
• The titanium segregation in Ti-doped sapphire affect the bubbles distribution and their sizes in the grown crystals.
• The bubbles absorb the light and decrease the optical performance.

Small bubbles can be observed in both sapphire and Ti-sapphire bulk crystals grown by Czochralski technique (Cz). Various thickness of wafers cut from the grown ingots were studied by optical microscopy. Bubbles distribution has different regulation in sapphire and Ti-sapphire crystals. All bubbles are spherical and have a diameter range from 2 μm to 5 μm in sapphire crystals while 10–45 μm in Ti-doped sapphire crystals. Some adjacent bubbles congregated into defects present various sizes and shape. The bubbles density increases as a function of pulling rate and rotation rate. The effect of bubbles on optical characterizations of Ti-sapphire crystals has been studied.