Atomic‐Level Insight into the Formation of Subsurface Dislocation Layer and Its Effect on Mechanical Properties During Ultrafast Laser Micro/Nano Fabrication

Abstract

Micro/nano processing technologies have been extensively studied since micro/nano structures are used in different area such as microelectronics and microdevices. As a high-precision processing technology, ultrafast laser has been applied in the fabrication of different types of metallic micro/nano structures. However, the knowledge about the materials response of metals at atomic scale during laser processing is still necessary to explore. Herein, the femtosecond laser processing of metals from the atomic structure perspective is revealed. Three different layers named recast layer, high density dislocation layer, and unaffected layer are found after femtosecond laser irradiation. The recast layer is on the surface, which is generated from the resolidification of melting materials. The high density dislocation layer, consisting of dislocations and stacking faults, is observed beneath the irradiated surface. The dislocation layer is produced by the laser-induced stress wave, and the mechanical properties of irradiated surface are affected by the laser-induced subsurface dislocation layer. The unaffected layer is not affected by laser irradiation, and maintains the initial atomic structure. The research gives new information about the ultrafast laser processing of metals at atomic-level, which is helpful to the fabrication of functional micro/nano devices for wide applications.

Boosted Spontaneous Formation of High‐Aspect Ratio Nanopeaks on Ultrafast Laser‐Irradiated Ni Surface

“…The layering of crystals with initial orientation and laser‐induced disorientions at the top of the peaks as presented in Figure 2g–j may result from very high cooling rates of up to 10 12 K s −1 , bringing the molten structure to a state of strong undercooling below the equilibrium melting temperature. [ 33 ] The structural transformations could be created either by crystal twinning, [ 34 ] stress‐induced dislocations, [ 35 ] or by inhomogeneous epitaxial regrowth. [ 33 ] Electron energy loss spectroscopy (EELS) entails the probing of core and valence level excitations caused by the laser absorption, where electrons are collected based on their energy after interacting with the specimen.…”

Laser Induced Coffee‐Ring Structure through Solid‐Liquid Transition for Color Printing

“…Ultrafast laser processing, a micro/nano manufacture method, has the advantages of mask-free, high precision, and controllability, [11][12][13][14][15] and is widely used to fabricate various micro/nano structures including periodic surface structure, irregular nanospikes, and nanovoids. [16][17][18][19][20][21] Depending on laser fluence and materials properties, rapid phase change and hydrodynamics motion of melting materials occurs during laser processing, as well generation of unusual surface structure. [22] When a laser pulse irradiated on metal target, a thin surface layer undergoes rapid melting process and thermal stress wave is generated in irradiated region.…”

A Machine Learning-Combined Flexible Sensor for Tactile Detection and Voice Recognition

“…27,28 Infilling active materials into the flexible substrate is a simple and efficient method for sensor fabrication, while the lithography and printing method is usually used to fabricate patterned sensors. 29,30 Laser processing has been recognized as a powerful method in various fields, such as micro/nanoprocessing, 31 patterning, 32,33 and sensors. 3 Laser processing has been demonstrated to be a high-throughput method, which realizes active materials synthesis and sensor patterning in one step.…”

“…Due to the excellent elasticity and flexibility, polymers have been used as the substrate of a wearable sensor, such as polydimethylsiloxane (PDMS). , The active materials are the key components that convert the mechanical stimuli to an electrical signal. ,, A wide range of materials, including graphene, carbon nanotubes, SiC, MXene, metal nanoparticles, , and nanowires, have been used as the active materials. A series of processing methods have been developed to manufacture a flexible sensor, such as lithography, inject printing, , screen printing, infilling, and laser processing method. , Infilling active materials into the flexible substrate is a simple and efficient method for sensor fabrication, while the lithography and printing method is usually used to fabricate patterned sensors. , Laser processing has been recognized as a powerful method in various fields, such as micro/nanoprocessing, patterning, , and sensors . Laser processing has been demonstrated to be a high-throughput method, which realizes active materials synthesis and sensor patterning in one step. , In recent years, there has been growing interest in the flexible sensor fabrication through laser processing.…”