Floating zone growth of high-purity MgO substrate single crystals.

Area of Science:

• Materials Science
• Crystal Growth
• Solid State Chemistry

Background:

• Magnesium oxide (MgO) is a crucial material for various electronic and optical applications.
• Growing high-quality MgO single crystals presents significant challenges due to its high melting point and evaporation rate.
• Existing commercial MgO substrates often lack the required purity for advanced epitaxial growth.

Purpose of the Study:

• To investigate the feasibility of the optical floating zone (OFZ) technique for growing high-purity MgO single crystals.
• To overcome the inherent material challenges associated with MgO crystal growth.
• To produce MgO substrate crystals suitable for developing novel epitaxial thin-film devices.

Main Methods:

• Single crystals of MgO were grown using the optical floating zone (OFZ) technique.
• Crystal dimensions ranged from 3.5–5 mm in diameter and up to 40 mm in length.
• High growth rates (>40 mm/h) and thermal gradients were employed despite MgO's challenging properties.

Main Results:

• Crack-free MgO single crystals were successfully grown, demonstrating the viability of the OFZ method.
• The OFZ technique yielded MgO crystals with a purity level of 5N (99.999%).
• The achieved purity is over an order of magnitude higher than that of commercial high-purity MgO substrates.

Conclusions:

• The optical floating zone (OFZ) technique is highly effective for producing high-purity MgO single crystals.
• The grown MgO crystals are suitable for use as substrates for epitaxially grown thin films.
• This advancement facilitates the development of next-generation devices utilizing high-quality MgO substrates.