ADVERTISEMENT

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.

ADVERTISEMENT

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.

ADVERTISEMENT
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).

Comments

READ THIS NEXT

Memo To White Nationalists From A Geneticist: Why White Purity Is A Terrible Idea

On August 14th, UCLA researchers Aaron Panofsky and Joan Donovan presented findings of their study,  “When Genetics Challenges a Racist’s […]

How The Brain Learns To Control Itself

Behavioral adaptation to environmental changes and unexpected events is crucial for survival, and it requires efficient decision-making and learning capabilities. […]

The DNA Of  Education — According To Studies In Twins

Children with low social status or behavioral problems often do worse at school. British researchers have now shown in two […]

Tropical Savanna: Animals Plants & Climate

A tropical savanna is an environment characterized by rolling hills, tall grasslands, and sparse trees. Large parts of Africa and […]

Glucose Transporters Protect Cancer Cells From Nutrient Deprivation

Glucose, glutamine, and fatty acids, the major fuel for mammalian cells, are taken up not only to produce the necessary […]

White Giraffe Found in Kenyan Reserve Is The Result of A Rare Genetic Disorder

Giraffes are one of the most well-known animals across the world. They are ubiquitous with zoos and the African savannah. […]

Injuries And Concussions Of Young Athletes Playing In Recreational Leagues

Do young children athletes playing sports in recreational leagues get injured or have concussions? Many people may think that young […]

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?