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Tunable Thermal Rectification and Negative Differential Thermal Resistance in Gas-Filled Nanostructure with Mechanically-Controllable nanopillars

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Journal of Thermal Science 2022年第4期31卷 1084-1093页

作者： LI Fan LI Haiyang WANG Jun XIA Guodong HWANG Gisuk MOE Key Laboratory of Enhanced Heat Transfer and Energy Conservation Beijing Key Laboratory of Heat Transfer and Energy ConversionBeijing University of TechnologyBeijing 100124China Department of Mechanical Engineering Wichita State University Wichita KS 67260USA

In this study,by using the nonequilibrium molecular dynamics and the kinetic theory,we examine the tailored nanoscale thermal transport via a gas-filled nanogap structure with mechanically-controllable nanopillars in one surface only,i.e.,changing nanopillar height.It is found that both the thermal rectification and negative differential thermal resistance(NDTR)effects can be substantially enhanced by controlling the nanopillar height.The maximum thermal rectification ratio can reach 340%and the△T range with NDTR can be significantly enlarged,which can be attributed to the tailored asymmetric thermal resistance via controlled adsorption in height-changing nanopillars,especially at a large temperature difference.These tunable thermal rectification and NDTR mechanisms provide insights for the design of thermal management systems.

关键词： thermal rectification negative differential thermal resistance kinetic theory nanopillars

Reduction of proximity effect in fabricating nanometer-spaced nanopillars by two-step exposure

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Journal of Semiconductors 2009年第11期30卷 127-130页

作者：张杨张仁平韩伟华刘剑杨香王颖李千秋杨富华 State Key Laboratory for Superlattices and Microstructures Institute of SemiconductorsChinese Academy of Sciences Engineering Research Center for Semiconductor Integrated Technology Institute of SemiconductorsChinese Academy of Sciences Department of Electronic Engineering The Chinese University of Hong Kong

A two-step exposure method to effectively reduce the proximity effect in fabricating nanometer-spaced nanopillars is presented. In this method, nanopillar patterns on poly-methylmethacrylate （PMMA） were partly crosslinked in the first-step exposure. After development, PMMA between nanopillar patterns was removed, and hence the proximity effect would not take place there in the subsequent exposure. In the second-step exposure, PMMA masks were completely cross-linked to achieve good resistance in inductively coupled plasma etching. Accurate pattern transfer of rows of nanopillars with spacing down to 40 nm was realized on a silicon-on-insulator substrate.

关键词： nanopillars electron-beam lithography negative PMMA proximitv effect

The dislocation structure of slip bands in deformed high entropy alloy nanopillars

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Journal of Materials Science & Technology 2021年第36期95卷 136-144页

作者： Qun Yang Yang Hu Jian-Min Zuo Department of Materials Science and Engineering University of Illinois at Urbana-ChampaignUrbanaIL 61801United States School of Physical Science and Technology Shanghai Tech UniversityShanghai 201210China Frederick Seitz Materials Research Laboratory University of Illinois at Urbana-ChampaignUrbanaIllinois 61801United States

Remarkable diversity is observed in dislocation interactions that are responsible for intermittent and sudden crystal slips.While large crystal slips can be easily observed on the surface of deformed crystals,unraveling the underlying dislocation interaction mechanisms,however,has been a longstanding challenge in the study of single-crystal plasticity.A recent study demonstrated that the sluggish dislocation dynamics in the high entropy alloy(HEA)of Al_(0.1)CoCrFeNi enables the observation of slip bands for a direct link to dislocation avalanches in a nanopillar.Here,we further examined the dislocation structure of slip bands in the HEA nanopillars oriented for single slip.Experimental evidence was provided on the dislocation organization in a slip band based on groups of primary dislocations,secondary dislocations,and dislocation pileups.The results were compared with the previously proposed slip band models.The unique aspects of the HEA that enable such observations were also investigated through an examination of the dislocation microstructure and its response to applied forces in the HEA nanopillars.

关键词： Crystal plasticity Dislocation structure nanopillars High entropy alloy Slip band Transmission electron microscopy

Strain Induced nanopillars and Variation of Magnetic Properties in La_(0.825)Sr_(0.175)MnO_3/LaAlO_3 Films

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Chinese Physics Letters 2019年第4期36卷 61-65页

作者：李鑫韩景智张雄祚张银峰田海东薛明珠李昆闻馨杨文云刘顺荃王常生杜红林张晓东王心安杨应昌杨金波 State Key Laboratory for Artificial Microstructure and Mesoscopic Physics School of PhysicsPeking University Ningxia Magvalley Novel Materials Technology Co. Ltd.New Energy Sub-ParkNingdong Energy & Chemical Industry Base Beijing Key Laboratory for Magnetoelectric Materials and Devices

To investigate the process of strain relaxation and resultant variation of microstructure and magnetic properties,low-doped La_(0.825)Sr_(0.175)MnO_3 epitaxial films with different thicknesses are deposited on LaAlO_3 substrates and strain induced nanopillars are discovered inside the La_(0.825) Sr_(0.175)MnO_3 film. Perpendicular oriented nanopillars mainly exist below 30 nm and tend to disappear above 30 nm. The distribution of nanopillars not only induce the variation of lattice parameters and local structural distortion but also lead to the deviation of easy magnetization axis from the perpendicular direction. Specifically, the out-of-plane lattice parameters of the film decrease quickly with the increase of the thickness but tend to be constant when the thickness is above 30 nm. Meanwhile, the variations of magnetic properties along in-plane and out-of-plane directions would also decline at first and they then remain nearly unchanged. Our work constructs the relationship between nanopillars and magnetic properties inside films. We are able to clearly reveal the effects of inhomogeneous strain relaxation.

关键词： nanopillars perpendicular magnetic

A non-lithographic plasma nanoassembly technology for polymeric nanodot and silicon nanopillar fabrication

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Frontiers of Chemical Science and Engineering 2019年第3期13卷 475-484页

作者： Athanasios Smyrnakis Angelos Zeniou Kamil Awsiuk Vassilios Constantoudis Evangelos Gogolides Institute of Nanoscience & Nanotechnology NCSR “Demokritos”Ag. Paraskevi15341 AtticaGreece Department of Physics University of Patras26504 PatrasGreece M. Smoluchowski Institute of Physics Jagiellonian University30-348 KrakowPoland

In this work, we present plasma etching alone as a directed assembly method to both create the nanodot pattern on an etched polymeric (PMMA) film and transfer it to a silicon substrate for the fabrication of silicon nanopillars or cone-like nanostructuring. By using a shield to control sputtering from inside the plasma reactor, the size and shape of the resulting nanodots can be better controlled by varying plasma parameters as the bias power. The effect of the shield on inhibitor deposition on the etched surfaces was investigated by time-of-flight secondary ion mass spectroscopy (ToF-SIMS) measurements. The fabrication of quasi-ordered PMMA nanodots of a diameter of 25 nm and period of 54 nm is demonstrated. Pattern transfer to the silicon substrate using the same plasma reactor was performed in two ways:(a) a mixed fluorine-fluorocarbon-oxygen nanoscale etch plasma process was employed to fabricate silicon nanopillars with a diameter of 25 nm and an aspect ratio of 5.6, which show the same periodicity as the nanodot pattern, and (b) high etch rate cryogenic plasma process was used for pattern transfer. The result is the nanostructuring of Si by high aspect ratio nanotip or nanocone-like features that show excellent antireflective properties.

关键词： plasma nanoassembly etching nanodots nanopillars nanofabrication