Innovations in laser-material interactions

Innovative laser techniques developed at Purdue University can be used to produce high-tech materials such as semiconductor oxide thin films and metals with high performance under extreme conditions and conduct ultrafine-scale manipulation of physical properties in nanomaterials. Gary Cheng, professor in Purdue University’s School of Industrial Engineering, has created innovations improving on traditional techniques of laser shock peening, nanowire shaping, and transparent film processing.

Nanoshaping platform

Cheng and his colleagues created a laser-based nanomanufacturing platform to achieve ultrafine-scale (down to sub-5nm), 3D manipulation of metals, and nanomaterials. The platform enables precise patterning, integration, and strain-engineering.

“Using a laser to manipulate the force and temperature on nanomaterials at an ultrafine scale creates opportunities for 3D micro/nano-component manufacturing, including patterning and integration of 0D-2D heterostructured nanomaterials,” Cheng says. “This generates opportunities for developing new generations of miniature devices in semiconductors, nanoelectronics, and quantum technology.”

Laser-assisted processing of thin films, nano-inks

Cheng’s laser-based processing of thin films and nanomaterial inks addresses challenges in microstructure, defects, residual stress control, and performance stability for thin film. It offers scalable manufacturing for high-performance and reliable optoelectronics and photovoltaics.

“The traditional material to create transparent conducting oxide (TCO) films has been indium tin oxide,” Cheng says. “Currently, semiconductor oxides such as gallium-doped zinc oxides and gallium-doped tin oxides are under research and development to replace it. Physical vapor deposition manufactures these thin films with high electron conductivity, however, their performance cannot meet the commercial criteria in performance and high-rate production.”

Researchers manufactured semiconductor oxide thin films by combining pulsed laser deposition with laser annealing to achieve better structural and optoelectronic properties than traditionally manufactured films. To realize large-scale thin-film device manufacturing, the team combined roll-to-roll printing of nano-inks with laser annealing for high-quality crystalline low-defect thin film, to deposit nanolayers from nanoparticles, nanowires, and 2D materials such as graphene and molybdenum disulfide.

“This method achieved superior performance compared with traditional deposition techniques, especially when various materials need to be deposited sequentially, making it attractive for large-scale manufacturing,” Cheng says.

Nanostructure-integrated laser shock peening

Traditional laser shock peening (LSP) works on the metal’s surface to improve its material properties such as resistance to fatigue and corrosion. The surface is confined by a glass or liquid barrier and then exposed to short laser pulses. The pulses create a shockwave traveling into the metal to deform the surface at an ultrahigh strain rate, generating beneficial microstructure and residual stress. However, traditional LSP has drawbacks.

“The microstructure and residual stresses aren’t stable after long fatigue cycles, especially under extreme conditions,” Cheng explains.

Cheng’s innovation, nanostructure-integrated laser shock peening (nLSP), controls the temperature during the process to introduce ultrafine and high-density nanoscale phases and dislocations. These nanostructures stabilize the beneficial microstructure and residual stress. His research has applications in aerospace to address the reliability of materials under extreme conditions. “Using the method, we have shown the efficiency of nLSP on aluminum and titanium alloys with much faster processing speed and stronger shock pressure, while nanostructures can also be introduced to enhance the metals’ mechanical properties and stability,” he adds.