Featured Research

from universities, journals, and other organizations

New Process Promises Bigger, Better Diamond Crystals

Date:
October 28, 2008
Source:
Carnegie Institution
Summary:
Researchers have developed a new technique for improving the properties of diamonds -- not only adding sparkle to gemstones, but also simplifying the process of making high-quality diamond for scalpel blades, electronic components, even quantum computers.

Diamonds such as these grown in the laboratory using a chemical vapor deposition process can be treated by a new high temperature, low pressure method to improve their color and optical clarity.
Credit: Carnegie Institution for Science

Researchers at the Carnegie Institution have developed a new technique for improving the properties of diamonds—not only adding sparkle to gemstones, but also simplifying the process of making high-quality diamond for scalpel blades, electronic components, even quantum computers.

A diamond may be forever, but the very qualities that make it a superior material for many purposes—its hardness, optical clarity, and resistance to chemicals, radiation, and electrical fields― can also make it a difficult substance with which to work. Defects can be purged by a heating process called annealing, but this can turn diamond to graphite, the soft, grey form of carbon used in pencil leads. To prevent graphitization, diamond treatments have previously required high pressures (up to 60,000 times atmospheric pressure) during annealing, but high pressure/high temperature annealing is expensive and there are limits on the size and quantities of diamonds that can be treated.

The results are published in the October 27-31 online edition of the Proceedings of the National Academies of Science. Yu-fei Meng, Chih-shiue Yan, Joseph Lai, Szczesny Krasnicki, Haiyun Shu, Thomas Yu, Qi Liang, Ho-kwang Mao, and Russell Hemley of the Carnegie Institution's Geophysical Laboratory used a method called chemical vapor deposition (CVD) to grow synthetic diamonds for their experiments. Unlike other methods, which mimic the high pressures deep within the earth where natural diamonds are formed, the CVD method produces single-crystal diamonds at low pressure. The resulting diamonds, which can be grown very rapidly, have precisely controlled compositions and comparatively few defects.

The Carnegie team then annealed the diamonds at temperatures up to 2000 C using a microwave plasma at pressures below atmospheric pressure. The crystals, which are originally yellow-brown if produced at very high growth rates, turned colorless or light pink. Despite the absence of stabilizing pressure there was minimal graphitization. Using analytical methods such as photoluminescence and absorption spectroscopy, the researchers were also able to identify the specific crystal defects that caused the color changes. In particular, the rosy pink color is produced by structures called nitrogen-vacancy (NV) centers, where a nitrogen atom takes the place of a carbon atom at a position in the crystal lattice next to a vacant site..

"This low-pressure/high-temperature annealing enhances the optical properties of this rapid-grown CVD single crystal diamond." says Meng. "We see a significant decrease in the amount of light absorbed across the spectrum from ultraviolet to visible and infrared. We were also able to determine that the decrease arises from the changes in defect structure associated with hydrogen atoms incorporated in the crystal lattice during CVD growth."

"It is striking to see brown CVD diamonds transformed by this cost-efficient method into clear, pink-tinted crystals," says Yan. And because the researchers pinpointed the cause of the color changes in their diamonds, "Our work may also help the gem industry to distinguish natural from synthetic diamond."

"The most exciting aspect of this new annealing process is the unlimited size of the crystals that can be treated. The breakthrough will allow us to push to kilocarat diamonds of high optical quality" says coauthor Ho-kwang Mao. Because the method does not require a high pressure press, it promises faster processing of diamonds and more types of diamonds to be de-colored than current high-pressure annealing methods. There is also no restriction on the size of crystals or the number of crystals, because the method is not limited by the chamber size of a high pressure press. The microwave unit is also significantly less expensive than a large high-pressure apparatus.

"The optimized process will produce better diamond for new-generation high pressure devices and window materials with improved optical properties in the ultraviolet to infrared range." concludes laboratory director Russell Hemley. "It has the advantage of being applicable in CVD reactors as a subsequent treatment after growth."

The high-quality, single crystal diamond made possible by the new process has a wide variety of applications in science and technology, such as the use of diamond crystals as anvils in high-pressure research and in optical applications that take advantage of diamond's exceptional transparency. Among the more exotic future applications of the pink diamonds made in this way is quantum computing, which could use the diamonds' NV centers for storing quantum information.


Story Source:

The above story is based on materials provided by Carnegie Institution. Note: Materials may be edited for content and length.


Cite This Page:

Carnegie Institution. "New Process Promises Bigger, Better Diamond Crystals." ScienceDaily. ScienceDaily, 28 October 2008. <www.sciencedaily.com/releases/2008/10/081027174541.htm>.
Carnegie Institution. (2008, October 28). New Process Promises Bigger, Better Diamond Crystals. ScienceDaily. Retrieved July 31, 2014 from www.sciencedaily.com/releases/2008/10/081027174541.htm
Carnegie Institution. "New Process Promises Bigger, Better Diamond Crystals." ScienceDaily. www.sciencedaily.com/releases/2008/10/081027174541.htm (accessed July 31, 2014).

Share This




More Matter & Energy News

Thursday, July 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Britain Testing Driverless Cars on Roadways

Britain Testing Driverless Cars on Roadways

AP (July 30, 2014) British officials said on Wednesday that driverless cars will be tested on roads in as many as three cities in a trial program set to begin in January. Officials said the tests will last up to three years. (July 30) Video provided by AP
Powered by NewsLook.com
7 Ways to Use Toothpaste: Howdini Hacks

7 Ways to Use Toothpaste: Howdini Hacks

Howdini (July 30, 2014) Fresh breath and clean teeth are great, but have you ever thought, "my toothpaste could be doing more". Well, it can! Lots of things! Howdini has 7 new uses for this household staple. Video provided by Howdini
Powered by NewsLook.com
Amid Drought, UCLA Sees Only Water

Amid Drought, UCLA Sees Only Water

AP (July 30, 2014) A ruptured 93-year-old water main left the UCLA campus awash in 8 million gallons of water in the middle of California's worst drought in decades. (July 30) Video provided by AP
Powered by NewsLook.com
Smartphone Powered Paper Plane Debuts at Airshow

Smartphone Powered Paper Plane Debuts at Airshow

AP (July 30, 2014) Smartphone powered paper airplane that was popular on crowdfunding website KickStarter makes its debut at Wisconsin airshow (July 30) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins