Bubble-Free SrTiO3 Crystals 30 mm In Diameter By Flame-Fusion Growth Method

Different thin film applications require the availability of high-quality single crystal substrates. A popular oxide for such purposes is SrTiO3 (STO). STO is also studied as an active material for device fabrication taking advantage of new ideas, namely, that the oxygen-deficient regions will act as metallic conductors for nano-inclusions in an insulating matrix. Applications where STO is expected to make an impact are microelectronics, power, and energy, and the list is open for further developments and concepts.

STO has a high melting temperature (2350 K) and, owing to this, fabrication of single crystals is not trivial. The flame-fusion (Verneuil) method is the only approach employed industrially to grow STO single crystals. The other methods are not suitable for commercial production due to small growth rates, sizes, or low yield. In the flame-fusion method, mixtures of powders of Sr and Ti oxides added with SrCO3 and are melted in a flame produced by burning a mixture of oxygen and hydrogen. The melt is solidified on a seed of an STO single crystal.


Difficulties are related to evaporation of Sr, control of thermal gradients, and dynamic changes of the growth parameters during processing. The last feature is due to the influence of the growing crystal on the furnace environment. In addition, the process control is also limited because some of the key growth parameters are more or less dependent on each other. Under presented circumstances and for larger crystals, growth stability changes, and during one production shift, one may easily end up with micron size or larger bubbles in the crystal. Especially critical in this regard is the end of the growth.

The larger the crystal is, the higher the probability is of obtaining crystals with unwanted defects. Another problem is that after growth, larger crystals are increasingly difficult to be uniformly oxygenated. Considering these addressed problems, it is easy to understand that, usually, the diameter of the STO crystals on the market does not exceed 20 mm.

In the work performed by researchers from Furuuchi Chemical Co, Japan, Kanazawa Institute of Technology, Japan, National Institute for Materials Science, Japan, INOE 2000, Romania, and National Institute of Materials Physics, Romania, bubble-free single crystals of STO with a diameter of 30 mm were grown under industrial conditions and within one production shift (~5h of growth). The composition of the source powder mixture, in particular, the amount of SrCO3 additive, and other growth parameters were optimized. After oxygenation, single crystals were characterized from the structural, microstructural, optical and THz spectroscopy viewpoints.

These crystals show similar properties with commercial ones of smaller sizes. This enables their use as substrates for thin film growth. It also suggests the possibility of growing single crystals of larger sizes and for commercialization of large area substrates.

These findings are described in the article entitled Growth of SrTiO3 single crystals with a diameter of about 30 mm by the Verneuil method (10.1021/acs.cgd.8b01004) published in the journal Crystal Growth and Design. Work was conducted by Yasushi Tateno from Furuuchi Chemical Co, Kazuhiro Endo from the Kanazawa Institute of Technology, Shunichi Arisawa from the National Institute for Materials Science, Raluca Iordanaescu from INOE 2000, and Aurel-Mihai Vlaicu, Liviu Nedelcu, Nicoleta Preda, Mihail Secu, Andrei C. Kuncser, and Petre Badica from the National Institute of Materials Physics (NIMP).



By 2020 Starbucks Hopes To Eliminate Plastic Straws From Their Stores

Following legislation in Seattle, Starbucks has announced that they will work to eliminate plastic straws from their stores by 2020. […]

Can VR Be Used To Fix Social Media’s Problems?

It’s no secret that too much time spent on social media can be bad for you. Even with the benefits […]

Electronegativity Trend

The electronegativity trend refers to a trend that can be seen across the periodic table. This trend is seen as […]

Insects Suffer Mass Decline With Disturbing Implications For The Ecosystem

Most people aren’t fans of insects, so to many people if insects suddenly disappeared it would seem like a good […]

Newborn Turtles Carry The Pollution History Of Their Mothers

Scientists detected a large number of chemical pollutants in freshly-laid eggs of hawksbill turtles along the Yucatán coast of Mexico. […]

H7N9 Influenza Could Be The Next Big Flu Pandemic

As the weather gets colder, we start preparing for winter and what it has in store for us. Part of […]

Semi-Artificial Photosynthesis Devices Could Create Renewable Hydrogen Fuel

Energy researchers have long been looking to the natural world for ideas about how to more efficiently harness energy and […]

Science Trends is a popular source of science news and education around the world. We cover everything from solar power cell technology to climate change to cancer research. We help hundreds of thousands of people every month learn about the world we live in and the latest scientific breakthroughs. Want to know more?