Material manufacturing from atomic layer

Atomic scale engineering of materials and interfaces has become increasingly important in material manufacturing.Atomic layer deposition(ALD)is a technology that can offer many unique properties to achieve atomic-scale material manufacturing controllability.Herein,we discuss this ALD technology for its applications,attributes,technology status and challenges.We envision that the ALD technology will continue making significant contributions to various industries and technologies in the coming years.

Atomic precision manufacturing of carbon nanotube-a perspective

Carbon nanotube(CNT),particularly single-walled CNT,possesses exceptional properties,and can be utilized in many high-end applications including high-performance electronics.However,the atomic arrangement of a CNT determines its band structure,making the atomic-precision fabrication one of most important topics for the development of this material.In this perspective,the author gives a personal summary on the history,current status of the atomic-precision fabrication of CNT and outlines the remaining challenges as well as the possible paths that may lead the production of atomically precise CNTs from‘fabrication’to‘manufacturing’.

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.

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.

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.

Controlled Vertical Transfer of Individual Au Atoms Using a Surface Supported Carbon Radical for Atomically Precise Manufacturing

To explore a proof-of-concept for atomically precise manufacturing(APM)using scanning probe microscopy(SPM),first principle theoretical calculations of atom-by-atom transfer from the apex of an SPM tip to an individual radical on a surfacebound organic molecule have been performed.Atom transfer is achieved by spatially controlled motion of a gold terminated tip to the radical.Two molecular tools for SPM-based APM have been designed and investigated,each comprising an adamantane core,a radical end group,and trithiol linkers to enable strong chemisorption on the Au(111)surface:ethynyl-adamantanetrithiol and adamantyl-trithiol.We demonstrate the details of controlled Au atom abstraction during tip approach toward and retraction from the radical species.Upon approach of the tip,the apical Au atom undergoes a transfer toward the carbon radical at a clearly defined threshold separation.This atomic displacement is accompanied by a net energy gain of the system in the range−0.5 to−1.5 eV,depending on the radical structure.In the case of a triangular pyramidal apex model,two tip configurations are possible after the tip atom displacement:(1)an Au atom is abstracted from the tip and bound to the C radical,not bound to the tip base anymore,and(2)apical tip atoms rearrange to form a continuous neck between the tip and radical.In the second case,subsequent tip retraction leads to the same final configuration as the first,with the abstracted Au atom bound to radical carbon atom of the molecular tool.For the less reactive adamantyl-trithiol radical molecular tool,Au atom transfer is less energetically favored,but this has the advantage of avoiding other apex gold atoms from rearrangement.

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.

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.

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.

通过原子制造制备高强高韧双相纳米结构Ta基金属玻璃

通过原子制造技术构建独特的纳米尺度结构可能是改善金属玻璃(MG)薄膜机械性能的有效途径.在此,我们使用脉冲激光沉积作为原子制造策略,制备了一种Ta基金属玻璃.TaNi MG具有小尺寸纳米晶体(1-4纳米)弥散在非晶基体上的双相纳米结构,因此在压缩过程中表现出7.99 GPa的超高屈服强度和15.87 GPa的高硬度,并伴有80%的大塑性.纳米晶体和MG基体之间的相互作用,导致了多个剪切带的形成,从而贡献了高塑性和强度.研究发现,原子制造方法有利于直接调控薄膜材料的微观结构和微观构型,并进一步优化其性能.这项工作为通过原子尺度的结构设计来打破金属材料的强度-塑性权衡提供了一个实用的方法.