Advancements in Power Design Enabled by Carbon in Material Science

Carbon, denoted as C in the periodic table, stands as an indispensable constituent. We, as entities of life fashioned from carbon, find our essence intertwined with this element. Collaborating with oxygen, the gaseous CO2 concentration serves as the litmus test for our impact on the phenomenon of global warming. In its solid manifestation, pure carbon assumes divergent forms, ranging from the pliable consistency of graphite to the unyielding solidity of diamond. The integration of carbon fibers enhances a myriad of commodities spanning from aircraft to angling implements. In archaeological endeavors, radiocarbon 14C dating assumes a pivotal role, emerging as an indispensable tool. It proves challenging to envisage an element more influential than carbon.

Additionally, casting our gaze towards the horizon of electronics, carbon emerges as a protagonist poised to orchestrate transformative narratives. This concise discourse endeavors to elucidate several breakthroughs in material science wherein carbon is poised to herald a revolution in the domain of electronics over the forthcoming years.

UWBG (Ultra-Wide Bandgap)

The advent of Wide Bandgap (WBG) transistors, hinged upon Silicon Carbide (SiC) and Gallium Nitride (GaN), has precipitated rapid strides in power switching efficacy. Materials boasting wider bandgaps exhibit a markedly elevated intrinsic thermal conductivity and a superior dielectric breakdown voltage vis-à-vis conventional Silicon (Si)-based MOSFET power transistors. This enhancement facilitates the fabrication of substrates for transistors that are smaller and more slender while preserving performance benchmarks. The diminutive proportions correspondingly mitigate gate and terminal capacitances and resistances, engendering expeditious and energy-efficient switching mechanisms with diminished power dissipation. SiC transistors boast a heightened capacity to manage elevated voltages and switch with augmented celerity and efficiency in comparison to Si-MOSFETs. Furthermore, High Electron Mobility Transistors (HEMT) predicated on GaN substrates outpace SiC-MOSFETs in terms of swiftness, rendering them invaluable for applications necessitating high-frequency electronics. The rapid switching prowess reduces the requisite dimensions of ancillary inductive and capacitive components, enabling the fabrication of compact, efficacious, and high-density power products.

The aforementioned advantages attendant to WBG transistors engender their extensive deployment in eco-friendly technologies encompassing electric vehicles, photovoltaic converters, IoT networks, and eco-design power supply solutions.

Carbon heralds the dawn of a new era in this trajectory with the advent of Ultra-Wide Bandgap (UWBG) transistors. Eschewing SiC or GaN substrates, these transistors pivot on the utilization of pristine diamond, characterized by an even loftier thermal conductivity – four times superior to SiC – a greater breakdown voltage – six times surpassing that of GaN – and a markedly broader bandgap than both SiC and GaN.

The efficacy of diverse transistor technologies finds quantification in the Baliga Figure of Merit (BFOM) – wherein a higher BFOM value denotes superior performance. This scale assumes a non-linear trajectory owing to critical performance indices such as breakdown voltage and conductivity being contingent upon the critical electric field value, which, in turn, escalates as a sixth power of the semiconductor bandgap electron voltage. Consequently, predicated on BFOM, WBG transistors outstrip Si-MOSFETs by approximately 730-fold, while a carbon-based UWBG transistor eclipses the latter by a staggering 15,625-fold – a monumental leap in efficacy that assumes paramount significance in the endeavor to transition our global energy consumption from the deleterious throes of fossil fuels to the realm of efficient green electrical energy.

The crystalline structure of graphene

Graphene, a two-dimensional carbon allotrope, materializes from nanolayers merely one atom thick, arranged in a honeycomb-shaped planar lattice. Exhibiting semi-metallic behavior, it facilitates the seamless flow of heat and electricity along its plane while impeding transverse transmission. Despite its bulk material form, it exerts robust light absorption across all visible wavelengths, yet maintains near-transparency in single sheets. At the microscopic level, its unparalleled strength arises from each atom’s double-bonding to its three neighbors, endowing it with exceptional rigidity and boasting an electron mobility of 15,000 cm²/Vs—surpassing conventional metrics outlined in table – and outstripping silicon in electrical conductivity.

Moreover, graphene unveils several extraordinary electrical attributes: its susceptibility to external magnetic fields enables the construction of sensitive hall-effect sensors operational across a wide temperature spectrum, from room temperature to cryogenic temperatures nearing absolute zero. Furthermore, graphene-based Field-Effect Transistors (gFETs) emerge as viable biosensors. Employing a liquid gate, gFETs detect alterations in channel current induced by charged biomolecules, facilitating ion-based measurements and enabling real-time analysis of proteins, biomolecules, and nucleic acids. This breakthrough underpins advancements in CRISPR gene editing, RNA drug exploration, infectious disease detection in humans, flora, and fauna, as well as cancer research endeavors.

Ongoing research delves into graphene’s distinctive electrical properties, promising novel electronic device paradigms. Spintronics, an area of particular interest, explores the potential for storing information in electron angular momentum (spin-up or spin-down). The orderly and inflexible array structure of graphene posits it as an optimal substrate for room temperature, atomic-level, spintronic non-volatile memory (NVM), envisioned to surpass conventional RAM in speed while retaining data integrity when powered off.

Carbon Nanotubes, the offspring of a rolled graphene sheet, exhibit exceptional tensile strength and thermal conductivity when configured into cylindrical nanostructures. Thermal interface materials comprising vertically aligned Carbon Nanotubes (CNTs) boast directional thermal conductivity, efficaciously dissipating heat from power electronic devices to designated heatsinks without compromising adjacent components. In trials, thermal conductivities nearing 15W/°K have been achieved – approximately threefold superior to thermal grease.

Furthermore, carbon nanotubes exhibit semiconductive or semi-metallic behavior contingent upon physical dimensions and/or chemical doping. Theoretically, a carbon nanotube possesses the potential to carry 1000 times more current than a copper conductor of comparable size, with its cylindrical structure facilitating controlled axial current flow, ushering in a new era of electronic device innovation.

Beyond thermal management, carbon nanotubes find utility in photovoltaics, sensors, displays, smart textiles, and energy harvesters. However, their most promising application lies in the realm of Li-Ion batteries featuring CNT cathodes. Conventional Li-Ion batteries grapple with thermal expansion issues during rapid charging or high discharge, compromising internal structure integrity. Carbon nanotubes, endowed with superior mechanical strength, withstand these thermal stresses without degradation. These advanced batteries boast rapid charging capabilities—from 10% to 90% within 15 minutes – while delivering enhanced energy density, double that of conventional counterparts. Moreover, they retain 90% of their original capacity after 800 charge/discharge cycles, heralding a revolution in electric vehicle propulsion, where a 1000 km range becomes the norm.