Laser machining fundamentals:micro,nano,atomic and close-to-atomic scales

With the rapid development in advanced industries,such as microelectronics and optics sectors,the functional feature size of devises/components has been decreasing from micro to nanometric,and even ACS for higher performance,smaller volume and lower energy consumption.By this time,a great many quantum structures are proposed,with not only an extreme scale of several or even single atom,but also a nearly ideal lattice structure with no material defect.It is almost no doubt that such structures play critical role in the next generation products,which shows an urgent demand for the ACSM.Laser machining is one of the most important approaches widely used in engineering and scientific research.It is high-efficient and applicable for most kinds of materials.Moreover,the processing scale covers a huge range from millimeters to nanometers,and has already touched the atomic level.Laser–material interaction mechanism,as the foundation of laser machining,determines the machining accuracy and surface quality.It becomes much more sophisticated and dominant with a decrease in processing scale,which is systematically reviewed in this article.In general,the mechanisms of laser-induced material removal are classified into ablation,CE and atomic desorption,with a decrease in the scale from above microns to angstroms.The effects of processing parameters on both fundamental material response and machined surface quality are discussed,as well as theoretical methods to simulate and understand the underlying mechanisms.Examples at nanometric to atomic scale are provided,which demonstrate the capability of laser machining in achieving the ultimate precision and becoming a promising approach to ACSM.

A combined multiscale modeling and experimental study on surface modification of high-volume micro-nanoparticles with atomic accuracy

Surface modification for micro-nanoparticles at the atomic and close-to-atomic scales is of great importance to enhance their performance in various applications,including high-volume battery,persistent luminescence,etc.Fluidized bed atomic layer deposition(FB-ALD)is a promising atomic-scale manufacturing technology that offers ultrathin films on large amounts of particulate materials.Nevertheless,nanoparticles tend to agglomerate due to the strong cohesive forces,which is much unfavorable to the film conformality and also hinders their real applications.In this paper,the particle fluidization process in an ultrasonic vibration-assisted FB-ALD reactor is numerically investigated from micro-scale to macro-scale through the multiscale computational fluid dynamics and discrete element method(CFD-DEM)modeling with experimental verification.Various vibration amplitudes and frequencies are investigated in terms of their effects on the fluid dynamics,distribution of particle velocity and solid volume fraction,as well as the size of agglomerates.Results show that the fluid turbulent kinetic energy,which is the key power source for the particles to obtain the kinetic energy for overcoming the interparticle agglomeration forces,can be strengthened obviously by the ultrasonic vibration.Besides,the application of ultrasonic vibration is found to reduce the mean agglomerate size in the FB.This is bound to facilitate the heat transfer and precursor diffusion in the entire FB-ALD reactor and the agglomerates,which can largely shorten the coating time and improve the film conformality as well as precursor utilization.The simulation results also agree well with our battery experimental results,verifying the validity of the multiscale CFD-DEM model.This work has provided momentous guidance to the mass manufacturing of atomic-scale particle coating from lab-scale to industrial applications.

Proposition of atomic and close-to-atomic scale manufacturing

Atomic and close-to-atomic scale manufacturing(ACSM)is the core competence of Manufacturing III.Unlike other conceptions or terminologies that only focus on the atomic level precision,ACSM defnes a new realm of manufacturing where quantum mechanics plays the dominant role in the atom/molecule addition,migration and removal,considering the uncertainty principle and the discrete nature of particles.As ACSM is still in its infant stage,only little has been systematically elaborated at the core proposition of ACSM by now,hence there is a need to understand its concept and vision.This article elucidates the development of ACSM and clarifes its proposition,which aims to achieve a clearer understanding on ACSM and direct more efective eforts toward this promising area.

Large scale manufacture of magnetic polymer particles using membranes and microfluidic devices

Magnetic polymer particles have found applications in diverse areas such as biomedical treatments, diagnosis and separation technology. These applications require the particles to have controlled sizes and narrow size distributions to gain better control and reproducibility in use. This paper reviews recent developments in the preparation of magnetic polymer particles at nano- and micro-scales by encapsulating magnetic components with dissolved or in situ formed polymers. Particle manufacture using emulsification and embedment methods produces magnetic polymer particles at micro-scale dimensions. However, the production of particles in this range using conventional emulsification methods affords very limited control over particle sizes and polydispersity. We report on alternative routes using membrane and microfluidics emulsification techniques, which have a capability to produce monodisperse emulsions and polymer microspheres （with coefficients of variation of less than 10%） in the range from submicrometer to a few 100 μm. The performance of these manufacturing methods is assessed with a view to future applications.

Study on Mechanisms of Photon-Induced Material Removal on Silicon at Atomic and Close-to-Atomic Scale

This paper presents a new approach for material removal on silicon at atomic and close-to-atomic scale assisted by photons.The corresponding mechanisms are also investigated.The proposed approach consists of two sequential steps:surface modification and photon irradiation.The back bonds of silicon atoms are first weakened by the chemisorption of chlorine and then broken by photon energy,leading to the desorption of chlorinated silicon.The mechanisms of photon-induced desorption of chlorinated silicon,i.e.,SiCl_(2) and SiCl,are explained by two models:the Menzel-Gomer-Redhead(MGR)and Antoniewicz models.The desorption probability associated with the two models is numerically calculated by solving the Liouville-von Neumann equations for open quantum systems.The calculation accuracy is verified by comparison with the results in literatures in the case of the NO/Pt(111)system.The calculation method is then applied to the cases of SiCl_(2)/Si and SiCl/Si systems.The results show that the value of desorption probability first increases dramatically and then saturates to a stable value within hundreds of femtoseconds after excitation.The desorption probability shows a super-linear dependence on the lifetime of excited states.

Material removal at atomic and close-to-atomic scale by highenergy photon:a case study using atomistic-continuum method

Extreme ultraviolet(EUV)light plays an important role in various fields such as material characterization and semiconductor manufacturing.It is also a potential approach in material fabrication at atomic and close-to-atomic scales.However,the material removal mechanism has not yet been fully understood.This paper studies the interaction of a femtosecond EUV pulse with monocrystalline silicon using molecular dynamics(MD)coupled with a two-temperature model(TTM).The photoionization mechanism,an important process occurring at a short wavelength,is introduced to the simulation and the results are compared with those of the traditional model.Dynamical processes including photoionization,atom desorption,and laser-induced shockwave are discussed under various fluencies,and the possibility of single atomic layer removal is explored.Results show that photoionization and the corresponding bond breakage are the main reasons of atom desorption.The method developed can be further employed to investigate the interaction between high-energy photons and the material at moderate fluence.

Challenges,interface engineering,and processing strategies toward practical sulfide-based all-solid-state lithium batteries

All-solid-state lithium batteries have emerged as a priority candidate for the next generation of safe and energy-dense energy storage devices surpassing state-of-art lithium-ion batteries.Among multitudinous solid-state batteries based on solid electrolytes(SEs),sulfide SEs have attracted burgeoning scrutiny due to their superior ionic conductivity and outstanding formability.However,from the perspective of their practical applications concerning cell integration and production,it is still extremely challenging to constructing compatible electrolyte/electrode interfaces and developing available scale processing technologies.This review presents a critical overview of the current underlying understanding of interfacial issues and analyzes the main processing challenges faced by sulfide-based all-solid-state batteries from the aspects of cost-effective and energy-dense design.Besides,the corresponding approaches involving interface engineering and processing protocols for addressing these issues and challenges are summarized.Fundamental and engineering perspectives on future development avenues toward practical application of high energy,safety,and long-life sulfide-based all-solid-state batteries are ultimately provided.

Toward Single-Atomic-Layer Lithography on Highly Oriented Pyrolytic Graphite Surfaces Using AFM-Based Electrochemical Etching

Atomic force microscopy(AFM)-based electrochemical etching of a highly oriented pyrolytic graphite(HOPG)surface is studied toward the single-atomic-layer lithography of intricate patterns.Electrochemical etching is performed in the water meniscus formed between the AFM tip apex and HOPG surface due to a capillary effect under controlled high relative humid-ity(~75%)at otherwise ambient conditions.The conditions to etch nano-holes,nano-lines,and other intricate patterns are investigated.The clectrochemical reactions of HOPG etching should not generatc debris duc to the conversion of graphite to gaseous CO and CO_(2)based on etching reactions.However,debris is observed on the etched HOPG surface,and incom-plete gasification of carbon occurs during the etching process,resulting in the generation of solid intermediates.Moreover,the applied potential is of critical importance for precise etching,and the precision is also significantly influenced by the AFM tip wear.This study shows that the AFM-based electrochemical etching has the potential to remove the material in a single-atomic-layer precision.This result is likely because the etching process is based on anodic dissolution,resulting in the material removal atom by atom.