Researchers in Japan have developed an innovative, scalable method to adjust thermal conductivity in thin films through the application of femtosecond lasers.
Study: Scalable Thermal Engineering via Femtosecond Laser-Direct-Written Phononic Nanostructures. Image Credit: VVVproduct/Shutterstock.com
The study was recently published in Advanced Functional Materials. It illustrates how their method could be pivotal in achieving both laboratory-scale precision and industrial-scale throughput simultaneously.
The researchers reported how femtosecond laser-induced periodic surface structures effectively manage thermal conductivity in thin film solids.
Their technique uses high-speed laser ablation to generate parallel nanoscale grooves with a throughput that is 1,000 times greater than traditional methods, thereby strategically modifying phonon scattering within the material.
This approach, which is both scalable and suitable for semiconductors, has the potential to enable the mass production of thermal engineering structures while preserving the precision typically found in laboratory settings.
Using Lasers to Make Nanostructures That Control Heat Transport
Controlling heat transport is one of the most significant challenges at the cutting edge of electronics and quantum information technologies.
As devices decrease in size while their power density increases, it becomes essential to manage the substantial heat they produce for optimal performance and longevity. One promising approach to achieve this is through phonon engineering, which involves the use of meticulously designed phononic nanostructures to manipulate and scatter phonons – the quasiparticles responsible for conducting heat in various solids.
Despite the potential applications of phononic nanostructures in areas such as nanoscale thermal insulation and energy conversion, their industrial-scale manufacturing remains quite difficult. Current high-resolution fabrication techniques, including electron-beam lithography (EBL), are inherently slow, complex, and costly, making them impractical for mass production.
The new technique utilizes powerful, high-speed lasers to create small, parallel grooves on silicon/silica thin films through a process known as laser ablation. The parallel grooves are designed with periodicities and groove-bottom thicknesses that are comparable to the average distance traveled by phonons.
These highly uniform nanostructures, referred to as femtosecond laser-induced periodic surface structures (fs-LIPSS), when combined with the traditional dry etching technique for tuning silicon thickness, significantly reduce the material’s thermal conductivity, as demonstrated through thermoreflectance measurements.
The researchers performed a series of numerical simulations, which validated that the changes in thermal conductivity observed are primarily due to the periodic nanostructures restricting the average travel distance of phonons, and so gained a deeper insight into the fundamental physics.
This fabrication method achieves an unprecedented throughput in the field. The fs-LIPSS process was determined to be over 1,000 times faster than the traditional single-beam EBL, all while preserving the necessary nanoscale resolution.
The present results represent an important milestone toward translating fundamental research findings into real-world applications. We expect the proposed method to accelerate the development of advanced technologies in fields where thermal management is crucial, including high-performance computing, on-chip energy conversion, and quantum devices.
Byunggi Kim, Assistant Professor, Department of Mechanical Engineering, Institute of Science Tokyo
The study indicates a transition towards the practical implementation of nanoscale thermal regulation. Given that the fs-LIPSS method is a maskless and resist-free approach, it is naturally compatible with CMOS technology and can be easily scaled to wafer-level sizes.
Our study establishes fs-LIPSS as a versatile platform for large-area thermal management and phonon engineering, and their functionality could be combined with optical and electronic properties, thereby aiding to establish a multifunctional platform.
Byunggi Kim, Assistant Professor, Department of Mechanical Engineering, Institute of Science Tokyo
Journal Reference:
Hamma, H., et al. (2025) Scalable Thermal Engineering via Femtosecond Laser-Direct-Written Phononic Nanostructures. Advanced Functional Materials. DOI:10.1002/adfm.202525269.