Absorbing Hydrogen Fluoride Gas to Enhance Crystal Growth

Dec 10, 2009
Vyacheslav Solovyov (left) and Harold "Bud" Wiesmann

(PhysOrg.com) -- Two scientists at the U.S. Department of Energy's Brookhaven National Laboratory have developed a method to control the buildup of hydrogen fluoride gas during the growth of precision crystals needed for applications such as superconductors, optical devices, and microelectronics. The invention -- by Vyacheslav Solovyov and Harold Wiesmann and recently awarded U.S. Patent number 7,622,426 -- could lead to more efficient production and improved performance of these materials.

Materials with highly ordered crystalline atomic structures have enormous potential for energy-saving devices such as , which carry current with no energy loss, and high-speed electronics. Such crystals are typically grown from precursors deposited on substrates — for example: tapes, wires, or wafers, such as those used in the production of computer chips.

Adding fluorine to the precursors enhances the transfer of crystalline order from the substrate to the growing material. But fluorine also presents a problem because it leads to the buildup of hydrogen fluoride gas. Hydrogen fluoride slows down the reaction that converts the to the desired material, sometimes even stopping in its tracks.

"You might think you could just vent the accumulating gas, but such methods have proven impractical," said Wiesmann. For one thing, you'd have to remove the gas uniformly, to avoid variations in pressure that might affect crystal growth, which becomes more difficult over larger areas. Also, other gases necessary to crystal growth, such as oxygen and water vapor, get extracted along with the hydrogen fluoride, and re-injecting these gases introduces more pressure problems.

"We've developed an improved method for removing hydrogen fluoride, based on absorption, that enhances the production of high-quality crystalline products." Wiesmann said.

The new method incorporates a solid material capable of absorbing hydrogen fluoride (HF) gas inside the reaction chamber. The solid material can be attached to the inner surface of the reaction chamber or free standing, as long as it is made to conform to the shape of the precursor at a uniform distance. This allows uniform extraction of HF across large areas, thereby yielding crystalline end products that are uniform and homogeneous regardless of the shape of the precursor material or the area it occupies inside the reaction chamber.

A wide range of materials from alkaline earth oxides to materials containing calcium, sodium, or even activated carbon can be used as HF absorbers. The HF absorber material could be sprayed, painted, or otherwise deposited onto an inert support such as quartz or various oxides to attach it to the reaction chamber. Or it could be made from a powder and pressed into a form that conforms to the shape of the growing crystals.

"Because these materials selectively absorb HF gas, water vapor, oxygen, and other gases that may be present and necessary for the conversion of the precursor material to finished crystals remain in the reaction vessel, undisturbed," Solovyov said.

Solovyov and Wiesmann demonstrated the effectiveness of this approach when growing crystals of a common yttrium-barium-copper-oxide (YBCO) superconductor. In these experiments, YBCO crystals grew at a faster rate in the presence of a barium-oxide HF absorber when compared to conventional methods of crystal growth. The method also preserves the uniformity of the crystal growth environment so that superconducting properties do not vary along the length of the film.

This specific reaction serves as only one example, and the patent applies to the many possible modifications and variations in the materials used and produced.

Source: Brookhaven National Laboratory (news : web)

Explore further: Technique simplifies the creation of high-tech crystals

add to favorites email to friend print save as pdf

Related Stories

Paving the Way for Crystal Growth

Mar 07, 2007

In order to study the properties of LBCO superconductors, scientists need to produce large, single crystals of the material - a difficult task that wasn't possible until recently. At the state-of-the-art crystal ...

Rounding up gases, nano-style

Feb 01, 2008

A new process for catching gas from the environment and holding it indefinitely in molecular-sized containers has been developed by a team of University of Calgary researchers, who say it represents a novel method of gas ...

Single Crystals as Reaction Vessels

Sep 02, 2008

Japanese researchers from the University of Tokyo have made a complex that crystallizes as a porous solid. Common reagents, even bulky ones, can easily diffuse into these pores and are sufficiently mobile to react with embedded ...

The Role of Titanium in Hydrogen Storage

Sep 02, 2005

As part of ongoing research to make hydrogen a mainstream source of clean, renewable energy, scientists from the U.S. Department of Energy's Brookhaven National Laboratory have determined how titanium atoms help hydrogen ...

Recommended for you

'Comb on a chip' powers new atomic clock design

16 hours ago

Researchers from the National Institute of Standards and Technology (NIST) and California Institute of Technology (Caltech) have demonstrated a new design for an atomic clock that is based on a chip-scale ...

Quantum leap in lasers brightens future for quantum computing

16 hours ago

Dartmouth scientists and their colleagues have devised a breakthrough laser that uses a single artificial atom to generate and emit particles of light. The laser may play a crucial role in the development of quantum computers, ...

Technique simplifies the creation of high-tech crystals

16 hours ago

Highly purified crystals that split light with uncanny precision are key parts of high-powered lenses, specialized optics and, potentially, computers that manipulate light instead of electricity. But producing ...

A new multi-bit 'spin' for MRAM storage

19 hours ago

Interest in magnetic random access memory (MRAM) is escalating, thanks to demand for fast, low-cost, nonvolatile, low-consumption, secure memory devices. MRAM, which relies on manipulating the magnetization ...

User comments : 0