Synthetic diamonds or Lab created diamonds are those that are produced in an unnatural way emulating the conditions in which natural diamonds are created. Synthetic diamond, man-made diamond that is usually produced by subjecting graphite to very high temperatures and pressures. These diamonds are chemically identical to natural diamonds (carbon) consisting of actual carbon atoms making them diamonds and also possess characteristics similar to natural diamonds.
Synthetic diamonds are widely used in end-user industries such as mining and construction, electronics, and healthcare. They are also used as gem in jewelry. Naturally-formed diamonds and synthetic diamonds have astonishing properties that lead to their wide applications. Its molecular structure, with strong covalent bonds, results in greater hardness than all other materials, ideal for cutters used in oil and gas drilling, where it enables longer tool lifetime by minimizing wear, reduces downtime and drives down operating costs and carbon footprints.
When it comes to the semiconductor industry, silicon has reigned as king in the electronics field, but it is coming to the end of its physical limits. To more effectively power the electrical grid, locomotives and even electric cars, Lawrence Livermore National Laboratory (LLNL) scientists are turning to diamond as an ultra-wide bandgap semiconductor. Diamond has been shown to have superior carrier mobility, break down electric field and thermal conductivity, the most important properties to power electronic devices. It became especially desirable after the development of a chemical vapor deposition (CVD) process for growth of high-quality single crystals.
Synthetic diamond is also emerging as most versatile super material for defence that shall have significant effect in a variety of applications as diverse as high power radars, communications and electronic warfare systems, Directed Energy Weapons, MEMS applications, Aerospace applications and Quantum science among many others. Diamond has recently emerged as a unique material for quantum information processing. In particular, Nitrogen-Vacancy (NV) centers in diamond exhibit quantum behavior up to room temperature. The diamond has many properties that fairly isolates the qubit from the surrounding environment including rigid structure, excellent heat conduction, and conducting electricity not at all.
The synthetic diamonds exhibited by a subsidiary of the China North Industries Group Corporation (Norinco), one of the country’s principal arms manufacturers, at the 2019 China International Jewellery Fair in Beijing may also be intended for use in laser-based weapons, according to a 4 December report published by the Global Times newspaper, citing comments by Chinese military analysts. While Norinco is the principal supplier of tanks, armoured vehicles, and artillery to the People’s Liberation Army (PLA), it is also a key player in the development of Chinese directed-energy weapons, along with Poly Technologies, which encompass laser- as well as microwave-based devices.
Laser & Optics Industry
Associate Professor Rich Mildren and his team have developed a technique to make diamond lasers that, in theory, have extraordinary power range. Five years ago, their lasers were just a few watts in power. Now they’ve reached 400 watts, close to the limit for comparable conventional lasers. Professor Mildren overcame the power output limitations of current laser technology by using diamond, due to its exceptionally high thermal conductivity and heat dissipating qualities. The resulting high-energy beam enables the laser to be more tightly focused on the target, reducing interaction times and increasing range.
DST Group says high-powered lasers lend themselves to many defence applications, including protection against missile threats. They are also useful in remote sensing, bio imaging, medicine, quantum science and the management of space debris. Researchers at MQ Photonics Research Centre leveraged Element Six’s low-absorption single-crystal CVD diamond in the demonstration of a diamond laser 20 times more powerful than previous systems. The diamond’s extraordinary properties played a critical role in the laser’s ability to deliver up to 380 Watts of output power—enough power to cut through steel. Synthetic diamond are used in Raman lasers, where the extreme properties of synthetic diamond enable a power scaling improvement of over two orders of magnitude.
It has the widest spectral band of any known material — extending from ultraviolet to far infrared and the millimeter-wave microwave band. Coupled with its mechanical and thermal properties, synthetic diamond is becoming the most popular material for optical windows in high-power CO2 lasers, solid state lasers and gyrotrons to enable a stable and enduring high optical quality of the laser beam. Single crystal synthetic diamond and polycrystalline CVD diamond have become an established solution in various applications of molecular spectroscopy like synthetic diamond ATR (attenuated total reflectance) prisms in FTIR (Fourier transform infrared) spectroscopy.
Laser Diode Arrays
High-power laser-diode arrays are found in material processing (e.g., welding and surface treatments), medical applications (e.g., tattoo removal and laser surgery), and applications for pumping high-power solid-state lasers. These hundreds of Watts Array consist of multiple emitters closely spaced on a single chip and require significant thermal management to optimize performance.
Adding a diamond heat spreader between the diode array and the submount effectively transports the heat away from small emitter hotspots. This can lead to significantly increase beam intensity and beam quality, since it allows for closer spacing of the individual emitters in the arrays. In addition, or alternatively, diamond heat spreaders can extend the lifetime of the diode arrays.
Synthetic diamond is chemically and biologically inert and can survive in severe physical, chemical and radioactive environments that would destroy lesser materials. Synthetic diamond is ideal for space applications as it is able to survive the harsh radiation environment for long periods. Raytheon’s diamond has also found its way into other kinds of electronics, including instruments on the Mars rovers Spirit and Opportunity.
Synthetic diamond also has a number of exciting electrical properties such as a low dielectric constant and loss, a high electrical carrier mobility, and a wide electronic band gap (it allows very low current even under high voltages). Many electronic applications of synthetic diamond are being developed, including high-power switches at power stations, high-frequency field-effect transistors and light-emitting diodes.
Diamond has the highest thermal conductivity of any material and can be used in semiconductor devices as silicon reaches its limits due to heat issues. But the cost of diamonds for this application is high. “If production costs can be cut, there will be market opportunities in wireless systems and other sectors,” said Patrick Hindle, editor of Microwave Journal. “There are physical limitations on packing more transistors onto silicon wafers due to heat issues,” Janik said. DiAmante’s diamond semiconductors could be the answer: “I want to help bring about a diamond-based technology revolution.”
One of the major factors driving the market studied is the increasing demand from the electronics industry, as synthetic diamonds have become a critical heat-enabling technology, which prevents silicon and other semiconductor materials from overheating. The usage of synthetic diamond in the electronics industry has been increasing, due to its ability to act as a heat sink. Synthetic diamond prevents silicon and other semiconductor materials from overheating, and thus, has become a critical heat-enabling technology
High Temperature Semiconductor Devices
A surge in temperature requirements for new applications in industrial, oil drilling and aviation markets have compelled designers to develop a complete portfolio of semiconductor devices for high-temperature applications to handle high operating temperatures. With an increase in temperature, the characteristics of semiconductor devices degrade due to variances in threshold voltages and carrier mobility, augmented junction current leakage and intrinsic carrier density. The characterization and qualification of semiconductors operating at high temperatures are crucial to ensure that quality, reliability and functionality all meet the requirements of the intended application. The qualification of any high-temperature semiconductor device needs to consider the operating life of the overall device, its reliability and its packaging.
The market for semiconductor devices for high-temperature applications is growing rapidly. The major factor attributed to its growth is the benefits associated with the adoption of these devices, such as reduced costs and improved efficiency. The global market is also being propelled by several industries such as electronics, defense and aerospace, automotive, and optoelectronics in which there is demand for semiconductor devices that are capable of operating reliably in harsh environments, including extremely high temperatures. Further rapid technological advancements coupled with vast improvements in the ability of these devices to operate in diverse environments are also strongly boosting the global market growth. The remarkable growth in the market for semiconductor devices for high-temperature applications is expected through the end of 2023.
The various types of semiconductor devices for high-temperature applications include GaN, SiC, GaAs, and the diamond semiconductor substrate. Diamond is anticipated to be the fastest growing segment of the global market. Diamond is considered an ideal material for semiconductors. Though diamond is an integral jewelry material, its unique properties are anticipated to change the way electronic products are powered. Silicon carbide was the largest revenue-generating segment in 2017 and is expected to witness substantial growth throughout the forecast period.
Stretching diamond for next-generation microelectronics
A research team has demonstrated for the first time the large, uniform tensile elastic straining of microfabricated diamond arrays through the nanomechanical approach. Their findings have shown the potential of strained diamonds as prime candidates for advanced functional devices in microelectronics, photonics, and quantum information technologies.
But diamond is also considered as a high-performance electronic and photonic material due to its ultra-high thermal conductivity, exceptional electric charge carrier mobility, high breakdown strength and ultra-wide bandgap. Bandgap is a key property in semi-conductor, and wide bandgap allows operation of high-power or high-frequency devices. “That’s why diamond can be considered as ‘Mount Everest’ of electronic materials, possessing all these excellent properties,” Dr Lu said.
However, the large bandgap and tight crystal structure of diamond make it difficult to “dope,” a common way to modulate the semi-conductors’ electronic properties during production, hence hampering the diamond’s industrial application in electronic and optoelectronic devices. A potential alternative is by “strain engineering,” that is to apply very large lattice strain, to change the electronic band structure and associated functional properties. But it was considered as “impossible” for diamond due to its extremely high hardness.
Then in 2018, Dr Lu and his collaborators discovered that, surprisingly, nanoscale diamond can be elastically bent with unexpected large local strain. This discovery suggests the change of physical properties in diamond through elastic strain engineering can be possible. Based on this, the latest study showed how this phenomenon can be utilized for developing functional diamond devices.
The research was co-led by Dr Lu Yang, Associate Professor in the Department of Mechanical Engineering (MNE) at CityU and researchers from Massachusetts Institute of Technology (MIT) and Harbin Institute of Technology (HIT). The team firstly microfabricated single-crystalline diamond samples from a solid diamond single crystals. The samples were in bridge-like shape — about one micrometre long and 300 nanometres wide, with both ends wider for gripping. The diamond bridges were then uniaxially stretched in a well-controlled manner within an electron microscope. Under cycles of continuous and controllable loading-unloading of quantitative tensile tests, the diamond bridges demonstrated a highly uniform, large elastic deformation of about 7.5% strain across the whole gauge section of the specimen, rather than deforming at a localized area in bending. And they recovered their original shape after unloading.
By further optimizing the sample geometry using the American Society for Testing and Materials (ASTM) standard, they achieved a maximum uniform tensile strain of up to 9.7%, which even surpassed the maximum local value in the 2018 study, and was close to the theoretical elastic limit of diamond. More importantly, to demonstrate the strained diamond device concept, the team also realized elastic straining of microfabricated diamond arrays.
The team then performed density functional theory (DFT) calculations to estimate the impact of elastic straining from 0 to 12% on the diamond’s electronic properties. The simulation results indicated that the bandgap of diamond generally decreased as the tensile strain increased, with the largest bandgap reduction rate down from about 5 eV to 3 eV at around 9% strain along a specific crystalline orientation. The team performed an electron energy-loss spectroscopy analysis on a pre-strained diamond sample and verified this bandgap decreasing trend.
Their calculation results also showed that, interestingly, the bandgap could change from indirect to direct with the tensile strains larger than 9% along another crystalline orientation. Direct bandgap in semi-conductor means an electron can directly emit a photon, allowing many optoelectronic applications with higher efficiency. These findings are an early step in achieving deep elastic strain engineering of microfabricated diamonds. By nanomechanical approach, the team demonstrated that the diamond’s band structure can be changed, and more importantly, these changes can be continuous and reversible, allowing different applications, from micro/nanoelectromechanical systems (MEMS/NEMS), strain-engineered transistors, to novel optoelectronic and quantum technologies. “I believe a new era for diamond is ahead of us,” said Dr Lu. The research at CityU was funded by the Hong Kong Research Grants Council and the National Natural Science Foundation of China.
Diamond Field-effect Transistors as Microwave Power Amplifiers
The data transfer rate in communications is increasing very rapidly. Therefore, electronic devices that operate at higher frequencies and generate higher output power are urgently needed for the present and future communications systems. On the other hand, from the environmental and energy-saving viewpoints, higher power efficiency from semiconductor devices is required at the same time. Diamond semiconductor will satisfy all of these requirements.
Applications such as broadcasting stations, communications satellites, and radars require higher output powers and frequencies, for example, 120 W and 10 GHz, respectively, for communications satellites. Such performance is beyond the ability of conventional semiconductor devices, so these applications still rely on traveling-wave tubes, which are vacuum tubes. However, the power efficiency of vacuum tubes is low because a large proportion of their input power is consumed as heat. Therefore, from the environmental and energy-saving viewpoints, vacuum tubes should be replaced by semiconductor devices.
Diamond is called the ultimate semiconductor because it intrinsically has many superior physical properties over conventional semiconductors. Diamond’s band gap is five times as wide as Si’s, which means that diamond’s breakdown field is 30 times higher; consequently, the output bias voltage can be set to the same ratio. As power is the product of voltage and current, the available power can be increased. Furthermore, the electron mobility in diamond is three times as high as in Si, which means that the device’s on-site resistance, or power consumption, during operation can be reduced. As is widely known, diamond has the highest thermal conductivity among all known materials, so it has the highest heat-dissipation efficiency during high-power operation. Therefore, a diamond device’s temperature rises much less for a specific power consumption. Diamond’s drift velocity is similar to that of GaAs; therefore, diamond transistors will exhibit high radio-frequency (RF) power capability, like GaAs transistors
AKHAN, using Man-Made Diamonds to Make Flexible Wearables
AKHAN Semiconductor, founded in 2012 by Adam Khan, is developing wearable technology with flexible and transparent displays for a range of industries–industrial, defense, aerospace and consumer. electronics–by creating man-made diamonds from methane gas. Using diamonds as a semiconductor material, as opposed to traditional silicon, AKHAN says it can make flexible and transparent displays on smaller and more powerful devices, as diamonds allow electronics to be thinner and to operate at higher temperatures.
Think about how your cell phone gets hot after heavy use; AKHAN’s technology can keep devices from overheating, making them more powerful and capable of handling more data, COO Carl Shurboff said. “Diamonds will pull heat out of a device much more efficiently, and so the device runs cooler and runs more efficient,” Shurboff said. “The cooler the device, the more efficient it will be,” as reported by Jim Dallke “The wearable devices today are kind of a neat toy someone buys, but they don’t wear it a lot,” he said. “Right now any wearable goes through issues, like scratched glass … We have the ability to make the hardest material for wearable technology so you won’t worry about scratching the display.” In 2015, Adam Khan was granted a US patent by the US Patent and Trademark Office today for a groundbreaking process that adheres diamond, the only truly transparent semiconductor, to metals and alloys (including transparent metals) in a way that allows for reliable wire bonding and high conductivity.
Diamond-age’ of power generation as nuclear batteries developed
New battery technology has been developed that uses nuclear waste to generate electricity. This Nuclear powered battery developed by researchers from university of Bristol generates electric current when synthetic diamond is placed in a radioactive field. Tom Scott, Professor in Materials in the University’s Interface Analysis Centre and a member of the Cabot Institute, said: “There are no moving parts involved, no emissions generated and no maintenance required, just direct electricity generation. By encapsulating radioactive material inside diamonds, we turn a long-term problem of nuclear waste into a nuclear-powered battery and a long-term supply of clean energy.” Professor Scott added: “We envision these batteries to be used in situations where it is not feasible to charge or replace conventional batteries. Obvious applications would be in low-power electrical devices where long life of the energy source is needed, such as pacemakers, satellites, high-altitude drones or even spacecraft.
The team have demonstrated a prototype ‘diamond battery’ using Nickel-63 as the radiation source. However, they are now working to significantly improve efficiency by utilising carbon-14, a radioactive version of carbon, which is generated in graphite blocks used to moderate the reaction in nuclear power plants. Despite their low-power, relative to current battery technologies, the life-time of these diamond batteries could revolutionise the powering of devices over long timescales. Using carbon-14 the battery would take 5,730 years to reach 50 per cent power, which is about as long as human civilization has existed.
The UK currently holds almost 95,000 tonnes of graphite blocks and by extracting carbon-14 from them, their radioactivity decreases, reducing the cost and challenge of safely storing this nuclear waste. Dr Neil Fox from the School of Chemistry explained: “Carbon-14 was chosen as a source material because it emits a short-range radiation, which is quickly absorbed by any solid material. The diamond does not allow the harmful radiation to escape. In fact, diamond is the hardest substance known to man, there is literally nothing we could use that could offer more protection.”
High-Voltage Power Devices
High-voltage power devices, such as insulated-gate bipolar transistors (IGBTs), have the advantage of higher efficiency and higher switching frequencies, but generate significant heat that demands extreme thermal-management solutions. With the highest known thermal conductivity, the synthetic diamond’s room-temperature thermal conductivity runs as high as 2000 W/mK, five times that of copper and 10 times that of aluminum nitride, it can be ideal heat spreader. Further, because diamond transports heat equally well in all three dimensions, it is the ideal material for thermal management applications; it can enhance the reliability of dense analog ICs incorporating power elements (MOSFETs, IGBTs, etc.).
“High-voltage IGBT applications typically involve switching or converting power for electrical vehicles, train and aerospace power generators, and alternative-energy distribution. In one test case using a 1200-V IGBT, a metalized diamond heat spreader replaced a ceramic substrate. It more than halved the junction-to-case thermal resistance, which in turn more than doubled the IGBT’s power rating,” write Bruce Bollinger and Thomas Obeloer in Electronic Design. Considering 50% of electronic failures occur as a result of heat, the supermaterial is valuable in all types of electronic and electrical applications, including telecommunications and microelectronic devices, where the build-up of heat can destroy delicate circuitry or severely impair performance.
Lawrence Livermore National Laboratory (LLNL) scientists are turning to diamond as an ultra-wide bandgap semiconductor. In photoconductive devices, the best combination of conductivity and frequency response is achieved by introducing impurities, which control carrier recombination lifetimes. Researchers found that in diamond, a cheap and easy alternative to this approach is electron irradiation where recombination defects are created by knocking the lattice atoms out of place.
“We said to ourselves ‘let’s take this pure high quality CVD diamond and irradiate it to see if we can tailor the carrier lifetime,'” Grivackas said. “Eventually, we nailed down the understanding of which irradiation defect is responsible for carrier lifetimes and how does the defect behave under annealing at technologically relevant temperatures.”
Photoconductive diamond switches produced this way can be used, for example, in the power grid to control current and voltage surges, which can fry out the equipment. Current silicon switches are big and bulky, but the diamond-based ones can accomplish the same thing with a device that could fit on the tip of a finger, Grivickas said.
They would be useful as biomedical sensors, providing stable electrochemical properties that enable the highest levels of sensitivity, selectivity and responsiveness.
“To monitor individual proteins and the interior of living cells, nanometer sized markers such as fluorescent proteins and quantum dots are used. Due to the high biological compatibility of diamond, fluorescent defects in diamond nanostructures are stable biomarkers without optical bleaching. The bright emission from the GeV centres could be suitable for such biological applications,” say Iwasaki and co-workers.
Diamonds to trace early cancers
Physicists from the University of Sydney have utilized the non-toxic and non-reactive nature of diamonds to identify cancerous tumors before they become life threatening. By attaching hyperpolarized diamonds to molecules targeting cancers the technique can allow tracking of the molecules’ movement in the body,” says Ewa Rej, the paper’s lead author. Hyperpolarised diamonds are constructed by aligning atoms inside a diamond and due to diamond’s magnetic nature; they create a signal detectable by an MRI scanner.
Element Six Develops Synthetic Diamonds for Wastewater Treatment
Element Six’s boron doped diamond (BDD) is an electrode material that electrochemically converts toxic organic pollutants to inert gases so that clean water can be safely discharged into the environment. In a successful pilot project with a large wastewater treatment company, results were achieved in the use of BDD electrodes. In one of the customers’ many refinery wastewater treatment studies, sulfur compounds were reduced to non-detectable concentrations and the chemical oxygen demand of the wastewater was reduced by more than 95%.
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