Much of the efficiency loss currently found in power devices is due to poor thermal management at the micro and nanoscales, which reduce performance and the longevity of components. New technologies based on nickel tin zirconium (ZrNiSn), gallium nitride (GaN) and silicon carbide (SiC) are being developed to increase energy efficiency. Thermal management in these new technologies is closely related to the design of the substrates on which the devices are manufactured. However, the conduction of heat in nanostructured systems cannot be described by the classical physics of macroscopic systems. The EU-funded Horizon 2020 ALMA project addressed this challenge by developing new design methods for heat management materials and structures that allow engineers to predict and understand the spread of thermal energy in a quantitative way at the scales appropriate to these new devices. New software predicts phonon transport Researchers created first-class open-source software in the form of almaBTE – the first software to deal with multiscale thermal modelling predictively. This supports fundamental and industrial applications, has attracted hundreds of users, and can even be interfaced with computer-aided design technology. The program can predictively tackle phonon transport in bulk crystals and alloys, thin films, superlattices, and multiscale structures with size features in the nanometre to micrometre range. In more technical terms, almaBTE is a software package that solves the space- and time-dependent Boltzmann transport equation for phonons, using only ab initio calculated quantities as inputs. In semiconductors and insulators, heat transport is mainly mediated by phonons - a quantum of vibrational energy that arises from oscillating atoms within a crystal lattice. Phonons are the quantum particles corresponding to vibrational lattice waves in the same way that photons are the quantum particles corresponding to electromagnetic waves. Novel materials can now be studied The almaBTE software allowed researchers to do things they couldn’t even dream of previously, such as the ab initio modelling of thermal transport in fin field effect transistors. “One of the achievements I am most proud of, however, is the ability to predict thermal conductivity in systems with points defects,” claims project coordinator Dr Natalio Mingo. “We studied ZrNiSn, cubic SiC, and GaN with defects and in all cases, we obtained an excellent agreement with experiments and unveiled new interesting physics.” ALMA demonstrated that scientists can now quantitatively predict and understand the spread of heat at the scales appropriate to the new devices. According to Dr Mingo: “ALMA helped us to study novel materials for electronics, such as SiC and GaN, or black phosphorus, and to discover previously unknown aspects, which we have published in high-impact journals.” Furthermore, the free almaBTE software developed by ALMA enables researchers to investigate other systems fundamentally related to the present energy problem. “Examples include new nanostructured thermoelectric materials, turbine thermal coatings, thermal design for phase-change memories, and nanoelectronic interconnects, all of which suffer from energy efficiency problems related to thermal management at the micro and nanoscales,” concludes Dr Mingo.
ALMA, thermal, energy, heat, phonon, almaBTE, gallium nitride (GaN), silicon carbide (SiC), electric power