How Silicon Carbide, Ultrananocrystalline Diamond, and Tetrahedral Amorphous Carbon are pushing the boundaries of MEMS technology
Imagine a world where your car's airbag deploys with perfect timing based on microscopic sensors that withstand extreme temperatures, where your smartphone's navigation guides you effortlessly using tiny mechanical systems smaller than a dust mite, and where medical implants can last a lifetime inside the human body without corroding or failing. This isn't science fiction—it's the reality enabled by Microelectromechanical Systems (MEMS), the invisible technological marvels woven throughout our daily lives.
Sensors that operate reliably in extreme engine temperatures
Gyroscopes and accelerometers for precise motion detection
Devices that can last decades inside the human body
For decades, silicon has been the undisputed champion of the microelectronics world, but as we push technology to operate in increasingly extreme environments—from scorching car engines to the harsh conditions inside our bodies—silicon is revealing its limitations. Enter three extraordinary materials poised to power the next technological revolution: silicon carbide (SiC), ultrananocrystalline diamond (UNCD), and hydrogen-free tetrahedral amorphous carbon (ta-C). These advanced materials are pushing the boundaries of what's possible in microtechnology, creating devices that are stronger, more durable, and capable of operating where conventional materials would fail.
To appreciate why these new materials matter, we first need to understand the invisible world of MEMS. These miniature devices combine electrical and mechanical components on a microscopic scale, typically ranging from 20 micrometers to a millimeter in size. They're everywhere around us—in your car's stability control systems, your smartphone's gyroscopes that detect orientation, the projectors that create sharp images using tiny mirrors, and medical devices that monitor blood pressure or deliver drugs with precision.
For decades, silicon has been the go-to material for MEMS, benefiting from the enormous knowledge base developed for computer chips. But silicon has its limitations—it becomes brittle at high temperatures, wears out quickly when components rub against each other, and can degrade in harsh chemical environments. These limitations become critical problems when designing sensors for hot environments like car engines or gas turbines, creating microscopic moving parts that need to survive millions of cycles, or developing medical implants that last decades inside the human body.
The search for alternatives has led researchers to three extraordinary materials that offer unique advantages while building on existing silicon fabrication knowledge. Let's meet our contenders in this materials revolution.
Silicon carbide represents a natural evolution from silicon, combining silicon and carbon in a crystalline structure that delivers exceptional properties.
What makes SiC particularly valuable is its ability to operate at temperatures well above 300°C, making it ideal for applications in automotive combustion processes and aerospace gas turbine controls 1 .
When you hear "diamond," you might picture glittering gems, but the diamond used in MEMS is something quite different—ultrananocrystalline diamond (UNCD) features incredibly tiny diamond crystals.
UNCD boasts some staggering mechanical properties—it has a Young's modulus of 930-970 GPa (nearly three times stiffer than silicon) and a fracture strength reaching 5 GPa 2 .
The most mysterious of our three materials, hydrogen-free tetrahedral amorphous carbon (ta-C), lacks the regular crystalline structure but makes up for it with an exceptionally high percentage of diamond-like bonds.
Ta-C delivers an impressive elastic modulus of 800 GPa and an extraordinary theoretical strength of 25.4 GPa—the highest of our three materials 3 .
How do materials scientists actually compare these advanced materials? At Northwestern University, researchers designed a comprehensive study to evaluate SiC, UNCD, and ta-C using identical testing conditions to ensure a fair comparison 3 .
The research team employed an elegant testing method called the Membrane Deflection Experiment (MDE), which works by creating thin films of each material and measuring how they respond to pressure.
This approach allowed the researchers to extract multiple mechanical properties from the same set of samples: the elastic modulus (stiffness) from how much the membranes deflected at low pressure, and the fracture strength from the pressure that caused failure.
The Northwestern University study revealed each material's unique strengths and limitations, providing valuable insights for future MEMS design 3 .
| Property | Silicon Carbide (SiC) | Ultrananocrystalline Diamond (UNCD) | Tetrahedral Amorphous Carbon (ta-C) |
|---|---|---|---|
| Young's Modulus (GPa) | 430 | 960 | 800 |
| Fracture Toughness (MPa·m¹/²) | 3.2 | 4.5 | 6.2 |
| Theoretical Strength (GPa) | 10.6 | 18.6 | 25.4 |
| Characteristic Length (nm) | 58 | 37 | 38 |
| Material | Key Advantages | Ideal Applications |
|---|---|---|
| SiC | High temperature stability, chemical inertness | High-temperature sensors, harsh environment applications |
| UNCD | Extreme hardness, low friction, high stiffness | Moving parts, tribological applications, RF MEMS |
| ta-C | Highest theoretical strength, good toughness | Protective coatings, flexible electronics |
The data revealed a clear hierarchy in mechanical performance. UNCD emerged as the stiffest material with an elastic modulus of 960 GPa, followed closely by ta-C at 800 GPa, with SiC measuring 430 GPa. When it came to theoretical strength—the maximum stress a perfect material can withstand—ta-C led at 25.4 GPa, followed by UNCD at 18.6 GPa, and SiC at 10.6 GPa.
Perhaps most surprisingly, ta-C demonstrated the highest fracture toughness at 6.2 MPa·m¹/², suggesting it best resists crack propagation, with UNCD at 4.5 MPa·m¹/² and SiC at 3.2 MPa·m¹/² 3 . This combination of properties suggests that while UNCD offers the highest stiffness, ta-C may provide better resistance to fracture in applications where impact or stress concentrations are concerns.
Creating and testing these advanced materials requires specialized equipment and methodologies. Here's a look at the essential toolkit that enables this cutting-edge research:
Deposits high-quality crystalline films used for growing single-crystal SiC layers on silicon substrates 1 .
Measures elastic and fracture properties; key methodology for comparing mechanical properties of SiC, UNCD, and ta-C 3 .
Provides high-resolution imaging of microstructures essential for examining MEMS device features and failure analysis.
Measures surface topography and mechanical properties at nanoscale; used to characterize surface roughness and detect phase transformations 9 .
As research progresses, these three materials are finding their way into increasingly sophisticated applications. The IEEE MEMS Conference in 2025 will highlight advances in these materials for applications ranging from RF components and environmental sensors to biomedical devices and aerospace systems 4 .
SiC is demonstrating exceptional biocompatibility and stability in implantable devices.
UNCD's low friction and wear resistance make it ideal for moving assemblies that must operate for millions of cycles without failure 6 .
Ta-C's unique combination of high strength and flexibility positions it well for emerging flexible electronics and wearable sensors.
Perhaps most exciting is the growing trend toward hybrid systems that combine the strengths of multiple materials. Researchers are developing MEMS that use SiC for high-temperature sensing elements, UNCD for moving interfaces, and ta-C for protective coatings—creating devices capable of operating in conditions that would have been unthinkable just a decade ago.
The quiet revolution in MEMS materials represents a fundamental shift in how we approach technological constraints. By moving beyond silicon to specialized materials like SiC, UNCD, and ta-C, engineers are creating microscopic devices that can sense, actuate, and compute in environments where conventional electronics would fail. Each material brings unique strengths to the table—SiC for high-temperature stability, UNCD for tribological applications, and ta-C for high-strength flexible systems.
As research continues, these materials will enable astonishing technological advances—from medical implants that last a lifetime inside the human body to sensors that can monitor industrial processes under extreme conditions.
The next time your car automatically adjusts to road conditions or your smartphone accurately tracks your movement, remember that there may be incredible microscopic materials working behind the scenes—materials tough enough to handle extreme heat, slippery enough to survive millions of movements, and strong enough to withstand forces that would shatter conventional silicon.
The future of technology isn't just about making things smaller—it's about making them smarter, tougher, and more capable using extraordinary materials that push the boundaries of what's possible at the microscale.