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Full-Text Articles in Engineering

Fiber-Optic Temperature And Flow Sensory System And Methods, Ming Han, Guigen Liu, Weilin Hou, Qiwen Shen Dec 2019

Fiber-Optic Temperature And Flow Sensory System And Methods, Ming Han, Guigen Liu, Weilin Hou, Qiwen Shen

Faculty Publications from the Department of Electrical and Computer Engineering

A fiber optic sensor, a process for utilizing a fiber optic sensor, and a process for fabricating a fiber optic sensor are described, where a double-side-polished silicon pillar is attacked to an optical fiber tip and forms, a Fabry-Perot cavity. In an implementation, a fiber optic sensor in accordance with an examplary embodiment includes an optical fiber configured to be coupled to a light source and a spectrometer; and a single silicon layer or multiple silicon layers disposed on an end face of the optical fiber, where each of the silicon layer(s) defines a Fabry-Perot interferometer, and where the ...


Aluminum/Carbon Composites Materials Fabricated By The Powder Metallurgy Process, Amélie Veillère, Hiroki Kurita, Akira Kawasaki, Yongfeng Lu, Jean-Marc Heintz, Jean-François Silvain Dec 2019

Aluminum/Carbon Composites Materials Fabricated By The Powder Metallurgy Process, Amélie Veillère, Hiroki Kurita, Akira Kawasaki, Yongfeng Lu, Jean-Marc Heintz, Jean-François Silvain

Faculty Publications from the Department of Electrical and Computer Engineering

Aluminum matrix composites reinforced with carbon fibers or diamond particles have been fabricated by a powder metallurgy process and characterized for thermal management applications. Al/C composite is a nonreactive system (absence of chemical reaction between the metallic matrix and the ceramic reinforcement) due to the presence of an alumina layer on the surface of the aluminum powder particles. In order to achieve fully dense materials and to enhance the thermo-mechanical properties of the Al/C composite materials, a semi-liquid method has been carried out with the addition of a small amount of Al-Si alloys in the Al matrix. Thermal ...


Water Pipeline Leakage Detection Based On Machine Learning And Wireless Sensor Networks, Yang Liu, Xuehui Ma, Yong Tie, Yinghui Zhang, Jing Gao Nov 2019

Water Pipeline Leakage Detection Based On Machine Learning And Wireless Sensor Networks, Yang Liu, Xuehui Ma, Yong Tie, Yinghui Zhang, Jing Gao

Faculty Publications from the Department of Electrical and Computer Engineering

The detection of water pipeline leakage is important to ensure that water supply networks can operate safely and conserve water resources. To address the lack of intelligent and the low efficiency of conventional leakage detection methods, this paper designs a leakage detection method based on machine learning and wireless sensor networks (WSNs). The system employs wireless sensors installed on pipelines to collect data and utilizes the 4G network to perform remote data transmission. A leakage triggered networking method is proposed to reduce the wireless sensor network’s energy consumption and prolong the system life cycle effectively. To enhance the precision ...


Hybrid Superhydrophilic–Superhydrophobic Micro/ Nanostructures Fabricated By Femtosecond Laserinduced Forward Transfer For Sub-Femtomolar Raman Detection, Xiaodan Ma, Lan Jiang, Xiaowei Li, Bohong Li, Ji Huang, Jiaxing Sun, Zhi Wang, Zhijie Xu, Liangti Qu, Yongfeng Lu, Tianhong Cui Sep 2019

Hybrid Superhydrophilic–Superhydrophobic Micro/ Nanostructures Fabricated By Femtosecond Laserinduced Forward Transfer For Sub-Femtomolar Raman Detection, Xiaodan Ma, Lan Jiang, Xiaowei Li, Bohong Li, Ji Huang, Jiaxing Sun, Zhi Wang, Zhijie Xu, Liangti Qu, Yongfeng Lu, Tianhong Cui

Faculty Publications from the Department of Electrical and Computer Engineering

Raman spectroscopy plays a crucial role in biochemical analysis. Recently, superhydrophobic surface-enhanced Raman scattering (SERS) substrates have enhanced detection limits by concentrating target molecules into small areas. However, due to the wet transition phenomenon, further reduction of the droplet contact area is prevented, and the detection limit is restricted. This paper proposes a simple method involving femtosecond laser-induced forward transfer for preparing a hybrid superhydrophilic–superhydrophobic SERS (HS-SERS) substrate by introducing a superhydrophilic pattern to promote the target molecules to concentrate on it for ultratrace detection. Furthermore, the HS-SERS substrate is heated to promote a smaller concentrated area. The water ...


Advanced Mathematical And Numerical Methods In Control And Optimization For Smart Grids, Zhan Shu, Michael Z.Q. Chen, Qing Hui Sep 2019

Advanced Mathematical And Numerical Methods In Control And Optimization For Smart Grids, Zhan Shu, Michael Z.Q. Chen, Qing Hui

Faculty Publications from the Department of Electrical and Computer Engineering

While renewable energy, as a part of smart-grid technologies, brings clean energy, it also brings a series of power quality problems. An increasing number of power electronic devices and new smart-grid technologies are used to ensure a safe, reliable, and high-quality operation of the power grid. However, the effectiveness of these control devices and technologies largely depends on the accuracy of the model, the advancement of control methods, and the numerical optimization of the parameters.

This special issue focuses on recent advances in modeling, numerical analysis, control, and optimization of smart grids with some special emphasis on the mathematical problems ...


Online Eeg Seizure Detection And Localization, Amirsalar Mansouri, Sanjay P. Singh, Khalid Sayood Aug 2019

Online Eeg Seizure Detection And Localization, Amirsalar Mansouri, Sanjay P. Singh, Khalid Sayood

Faculty Publications from the Department of Electrical and Computer Engineering

Epilepsy is one of the three most prevalent neurological disorders. A significant proportion of patients suffering from epilepsy can be effectively treated if their seizures are detected in a timely manner. However, detection of most seizures requires the attention of trained neurologists-- a scarce resource. Therefore, there is a need for an automatic seizure detection capability. A tunable non-patient-specific, non-seizure-specific method is proposed to detect the presence and locality of a seizure using electroencephalography (EEG) signals. This multifaceted computational approach is based on a network model of the brain and a distance metric based on the spectral profiles of EEG ...


Fqstat: A Parallel Architecture For Very High-Speed Assessment Of Sequencing Quality Metrics, Sree K. Chanumolu, Mustafa Albahrani, Hasan H. Otu Aug 2019

Fqstat: A Parallel Architecture For Very High-Speed Assessment Of Sequencing Quality Metrics, Sree K. Chanumolu, Mustafa Albahrani, Hasan H. Otu

Faculty Publications from the Department of Electrical and Computer Engineering

Background: High throughput DNA/RNA sequencing has revolutionized biological and clinical research. Sequencing is widely used, and generates very large amounts of data, mainly due to reduced cost and advanced technologies. Quickly assessing the quality of giga-to-tera base levels of sequencing data has become a routine but important task. Identification and elimination of low-quality sequence data is crucial for reliability of downstream analysis results. There is a need for a high-speed tool that uses optimized parallel programming for batch processing and simply gauges the quality of sequencing data from multiple datasets independent of any other processing steps.

Results: FQStat is ...


Fiber Optic Bolometer, Ming Han, Matthew L. Reinke Jul 2019

Fiber Optic Bolometer, Ming Han, Matthew L. Reinke

Faculty Publications from the Department of Electrical and Computer Engineering

The present disclosure is directed to a fiber optic bolometer device . In an implementation , a fiber optic bolometer device includes an optical fiber and a silicon layer that comprises a Fabry - Perot interferometer . The silicon layer includes a first surface and a second surface . The fiber optic bolometer device includes a reflective dielectric film disposed over the first surface of the silicon layer where the reflective dielec tric film is adjacent to an end face of the optical fiber . The fiber optic bolometer device also includes an absorptive coating disposed over the second surface of the silicon layer ( e . g ...


Fabrication Of Highly Homogeneous And Controllable Nanogratings On Silicon Via Chemical Etching-Assisted Femtosecond Laser Modification, Ji Huang, Lan Jiang, Xiaowei Li, Andong Wang, Zhi Wang, Qingsong Wang, Jie Hu, Liangti Qu, Tianhong Cui, Yongfeng Lu Jan 2019

Fabrication Of Highly Homogeneous And Controllable Nanogratings On Silicon Via Chemical Etching-Assisted Femtosecond Laser Modification, Ji Huang, Lan Jiang, Xiaowei Li, Andong Wang, Zhi Wang, Qingsong Wang, Jie Hu, Liangti Qu, Tianhong Cui, Yongfeng Lu

Faculty Publications from the Department of Electrical and Computer Engineering

Femtosecond laser direct writing is widely exploited in surface periodic structures processing. However, this technique still faces challenges in obtaining high surface homogeneity and flexible morphology controllability. In this study, a flexible and efficient approach has been proposed to fabricate highly homogeneous and controllable nanogratings on silicon via chemical etching-assisted femtosecond laser modification. By precisely manipulating the laser-material interaction process, alternating amorphous-crystalline nanofringes are generated when employing femtosecond laser scanning over a Si sample, with almost no material removal. Following auxiliary chemical etching, highly homogeneous nanograting structures are obtained, and the morphology of the nanogratings can be flexibly managed through ...


Direct Observation Of Structure-Assisted Filament Splitting During Ultrafast Multiplepulse Laser Ablation, Feifei Wang, Changji Pan, Jingya Sun, Qingsong Wang, Yongfeng Lu, Lan Jiang Jan 2019

Direct Observation Of Structure-Assisted Filament Splitting During Ultrafast Multiplepulse Laser Ablation, Feifei Wang, Changji Pan, Jingya Sun, Qingsong Wang, Yongfeng Lu, Lan Jiang

Faculty Publications from the Department of Electrical and Computer Engineering

Laser-induced plasma evolution in fused silica through multipulse laser ablation was studied using pump-probe technology. Filament splitting was observed in the early stage of plasma evolution (before ~300 fs). This phenomenon can be attributed to competition between laser divergent propagation induced by a pre-pulse-induced crater and the nonlinear self-focusing effect. This effect was validated through simulation results. With the increasing pulse number, the appearance of filament peak electron density was postponed. Furthermore, a second peak in the filament and peak position separation were observed because of an optical path difference between the lasers propagating from the crater center and edge ...


Beam Manipulation Mechanisms Of Dielectric Metasurfaces, Baoshan Guo, Lan Jiang, Yanhong Hua, Ningwei Zhan, Jingang Jia, Kunpeng Chu, Yongfeng Lu Jan 2019

Beam Manipulation Mechanisms Of Dielectric Metasurfaces, Baoshan Guo, Lan Jiang, Yanhong Hua, Ningwei Zhan, Jingang Jia, Kunpeng Chu, Yongfeng Lu

Faculty Publications from the Department of Electrical and Computer Engineering

Dielectric metasurfaces can achieve flexible beam manipulations. Herein, we study dielectric metasurfaces with different refractive indices, periods, incident angles, and cross-sectional shapes to determine the metasurface working mechanisms. Perfect transmission mainly depends on multipolar interference that can be used to control the transmission modes through the hybrid periods, hybrid cross sections, and multilayers. Perfect reflection is strongly influenced by the period of the metasurface and occurs only when the period is shorter than incident wavelength, which can be attributed to the lattice coupling. Furthermore, lattice coupling can be classified into two types with distinct properties: vertical mode and horizontal mode ...


Zebrafish Macroh2a Variants Have Distinct Embryo Localization And Function, E. Gonzalez-Munoz, Y. Arboleda-Estudillo, S. K. Chanumolu, H. H. Otu, J. B. Cibelli Jan 2019

Zebrafish Macroh2a Variants Have Distinct Embryo Localization And Function, E. Gonzalez-Munoz, Y. Arboleda-Estudillo, S. K. Chanumolu, H. H. Otu, J. B. Cibelli

Faculty Publications from the Department of Electrical and Computer Engineering

Mouse and cell-based studies have shown that macroH2A histone variants predominantly associate with heterochromatin. Functional studies found that macroH2As are involved in gene repression, inhibiting the acquisition of pluripotency and preserving cell differentiation. However, only a few studies have analysed the role of macroH2A during early embryo development. We report the development of transgenic zebrafish lines expressing macroH2A isoforms (mH2A1 and mH2A2) fusion proteins (with GFP) under identified endogenous promoters. We found that mH2A1 and mH2A2 have different spatial and temporal expression patterns during embryonic development. mH2A1 is expressed mostly in the extraembryonic Yolk Syncytial Layer (YSL) starting before shield ...


Effect Of Titanium And Zirconium Carbide Interphases On The Thermal Conductivity And Interfacial Heat Transfers In Copper/ Diamond Composite Materials, Clio Azina, Inaki Cornu, Jean-Francois Silvain, Yongfeng Lu, Jean-Luc Battaglia Jan 2019

Effect Of Titanium And Zirconium Carbide Interphases On The Thermal Conductivity And Interfacial Heat Transfers In Copper/ Diamond Composite Materials, Clio Azina, Inaki Cornu, Jean-Francois Silvain, Yongfeng Lu, Jean-Luc Battaglia

Faculty Publications from the Department of Electrical and Computer Engineering

Thermal properties of metal matrix composite materials are becoming ever more relevant with the increasing demand for thermally efficient materials. In this work, the thermal conductivity and heat transfers at the interfaces of copper matrix composite materials reinforced with diamond particles (Cu/D) are discussed. The composite materials contain either ZrC or TiC interphases and exhibit, respectively, higher and lower thermal conductivities with respect to their pure Cu/D counterparts. These thermal conductivities are accounted to the presence of strong covalent bonds and increased relative densities. The role of these interphases is also discussed regarding the phonon transmission at the ...


Manipulation Of Lipss Orientation On Silicon Surfaces Using Orthogonally Polarized Femtosecond Laser Double-Pulse Trains, Wei Liu, Lan Jiang, Weina Han, Jie Hu, Xiaowei Li, Ji Huang, Shenghua Zhan, Yongfeng Lu Jan 2019

Manipulation Of Lipss Orientation On Silicon Surfaces Using Orthogonally Polarized Femtosecond Laser Double-Pulse Trains, Wei Liu, Lan Jiang, Weina Han, Jie Hu, Xiaowei Li, Ji Huang, Shenghua Zhan, Yongfeng Lu

Faculty Publications from the Department of Electrical and Computer Engineering

Laser-induced periodic surface structures (LIPSS) provide an easy and costeffective means of fabricating gratings and have been widely studied in recent decades. To overcome the challenge of orientation controllability, we developed a feasible and efficient method for manipulating the orientation of LIPSS in real time. Specifically, we used orthogonally polarized and equal-energy femtosecond laser (50 fs, 800 nm) double-pulse trains with time delay about 1ps, total peak laser fluence about 1.0 J/cm2, laser repetition frequency at 100 Hz and scanning speed at 150 μm/s to manipulate the LIPSS orientation on silicon surfaces perpendicular to the scanning ...


Overview Of Extreme Manufacturing, Dongming Guo, Yongfeng Lu Jan 2019

Overview Of Extreme Manufacturing, Dongming Guo, Yongfeng Lu

Faculty Publications from the Department of Electrical and Computer Engineering

Today we live in a new era of economic globalization and rapid technological growth. The advancement of both our society and standard of living require us to delve into this new world and unleash the possibilities our future. We need to broaden the horizons of our universe to discover a new realm where the future of humanity can flourish. We need to be unafraid to unveil the mysteries hidden within the depths of our oceans to unearth treasures that will benefit not only us, but the generations to come.


The Next-Generation Retail Electricity Market In The Context Of Distributed Energy Resources: Vision And Integrating Framework, Josue Campos Do Prado, Wei Qiao, Liyan Qu, Julio Romero Aguero Jan 2019

The Next-Generation Retail Electricity Market In The Context Of Distributed Energy Resources: Vision And Integrating Framework, Josue Campos Do Prado, Wei Qiao, Liyan Qu, Julio Romero Aguero

Faculty Publications from the Department of Electrical and Computer Engineering

The increasing adoption of distributed energy resources (DERs) and smart grid technologies (SGTs) by end-user retail customers is changing significantly both technical and economic operations in the distribution grid. The next-generation retail electricity market will promote decentralization, efficiency, and competitiveness by accommodating existing and new agents through new business models and transactive approaches in an advanced metering infrastructure (AMI). However, these changes will bring several technical challenges to be addressed in transmission and distribution systems. Considerable activities have been carried out worldwide to study the impacts of integrating DERs into the grid and in the wholesale electricity market. However, the ...


The Temporal-Spatial Evolution Of Electron Dynamics Induced By Femtosecond Double Pulses, Changji Pan, Lan Jiang, Jingya Sun, Qingsong Wang, Feifei Wang, Yongfeng Lu Jan 2019

The Temporal-Spatial Evolution Of Electron Dynamics Induced By Femtosecond Double Pulses, Changji Pan, Lan Jiang, Jingya Sun, Qingsong Wang, Feifei Wang, Yongfeng Lu

Faculty Publications from the Department of Electrical and Computer Engineering

The temporal and spatial electron dynamics were investigated under irradiation of temporally shaped femtosecond double pulses. Filament split was observed upon arrival of the second pulse, which was attributed to the emergence of transient high-reflective surface induced by the first pulse. The electron density analysis showed that the total deposition energy of double pulses case was generally higher than that of single pulse case. Particularly, the maximum deposition energy was obtained at 350 fs separation time of double pulses. The results of our experiment demonstrated optimization of energy deposition efficiency by temporally shaping laser pulses, which will benefit the fabrication ...


Neutrophil Activation In Systemic Capillary Leak Syndrome (Clarkson Disease), Zhihui Xie, Douglas B. Kuhns, Xuesong Gu, Hasan H. Otu, Towia A. Libermann, John I. Gallin, Samir M. Parikh, Kirk M. Druey Jan 2019

Neutrophil Activation In Systemic Capillary Leak Syndrome (Clarkson Disease), Zhihui Xie, Douglas B. Kuhns, Xuesong Gu, Hasan H. Otu, Towia A. Libermann, John I. Gallin, Samir M. Parikh, Kirk M. Druey

Faculty Publications from the Department of Electrical and Computer Engineering

Systemic capillary leak syndrome (SCLS; Clarkson disease) is a rare orphan disorder characterized by transient yet recurrent episodes of hypotension and peripheral oedema due to diffuse vascular leakage of fluids and proteins into soft tissues. Humoral mediators, cellular responses and genetic features accounting for the clinical phenotype of SCLS are virtually unknown. Here, we searched for factors altered in acute SCLS plasma relative to matched convalescent samples using multiplexed aptamer‐based proteomic screening. Relative amounts of 612 proteins were changed greater than twofold and 81 proteins were changed at least threefold. Among the most enriched proteins in acute SCLS plasma ...


Monitoring Aging Of Power Semiconductor Devices Based On Case Temperature, Wei Qiao, Ze Wang, Liyan Qu Jan 2019

Monitoring Aging Of Power Semiconductor Devices Based On Case Temperature, Wei Qiao, Ze Wang, Liyan Qu

Faculty Publications from the Department of Electrical and Computer Engineering

The aging of an electronic component in an electronic power converter can be monitored based on two or more case temperature measurements. A power electronic device is enclosed in a package having a baseplate, in which the power electronic device generates heat during operation and the baseplate transfers heat to a heat dissipating device or a cooling device. Sensors measure temperatures at first and second locations on a surface of the baseplate. A data processor calculates a value for a first parameter based on the temperatures at the first and second locations, in which the first parameter is indicative of ...


Multi-Pig Part Detection And Association With A Fully-Convolutional Network, Eric T. Psota, Mateusz Mittek, Lance C. Pérez, Ty Schmidt, Benny Mote Jan 2019

Multi-Pig Part Detection And Association With A Fully-Convolutional Network, Eric T. Psota, Mateusz Mittek, Lance C. Pérez, Ty Schmidt, Benny Mote

Faculty Publications from the Department of Electrical and Computer Engineering

Computer vision systems have the potential to provide automated, non-invasive monitoring of livestock animals, however, the lack of public datasets with well-defined targets and evaluation metrics presents a significant challenge for researchers. Consequently, existing solutions often focus on achieving task-specific objectives using relatively small, private datasets. This work introduces a new dataset and method for instance-level detection of multiple pigs in group-housed environments. The method uses a single fully-convolutional neural network to detect the location and orientation of each animal, where both body part locations and pairwise associations are represented in the image space. Accompanying this method is a new ...


Growth Of Nitride Films, Yongfeng Lu, Hossein Rabiee Golgir, Yunshen Zhou Jan 2019

Growth Of Nitride Films, Yongfeng Lu, Hossein Rabiee Golgir, Yunshen Zhou

Faculty Publications from the Department of Electrical and Computer Engineering

A gallium nitride thin film can be formed on a substrate at a low temperature (e.g., not higher than 600°C .) by applying a laser to resonantly excite molecules of a first precursor that contains nitrogen, in which the laser has a wavelength that is selected to match a vibration mode and/or a vibrational rotational mode of the molecules of the first precursor. A second precursor is provided in which the excited first precursor and the second precursor react to form a nitride that is deposited on the substrate. For example, the second precursor may include gallium, and ...


Foreword For The Inaugural Issue, Dongming Guo, Yongfeng Lu Jan 2019

Foreword For The Inaugural Issue, Dongming Guo, Yongfeng Lu

Faculty Publications from the Department of Electrical and Computer Engineering

The International Journal of Extreme Manufacturing is a leading, worldwide scientific journal focused on the fields of extreme manufacturing. Published within it are the latest scientific and engineering achievements in related fields, as well as pioneering scientific, technological, and engineering innovations and developments.


A Novel Method Of Near-Miss Event Detection With Software Defined Radar In Improving Railyard Safety, Subharthi Banerjee, Jose Santos, Michael Hempel, Pejman Ghasemzadeh, Hamid Sharif Jan 2019

A Novel Method Of Near-Miss Event Detection With Software Defined Radar In Improving Railyard Safety, Subharthi Banerjee, Jose Santos, Michael Hempel, Pejman Ghasemzadeh, Hamid Sharif

Faculty Publications from the Department of Electrical and Computer Engineering

Railyards are one of the most challenging and complex workplace environments in any industry. Railyard workers are constantly surrounded by dangerous moving objects, in a noisy environment where distractions can easily result in accidents or casualties. Throughout the years, yards have been contributing 20–30% of the total accidents that happen in railroads. Monitoring the railyard workspace to keep personnel safe from falls, slips, being struck by large object, etc. and preventing fatal accidents can be particularly challenging due to the sheer number of factors involved, such as the need to protect a large geographical space, the inherent dynamicity of ...


Rechargeable Multi - Cell Battery, Wei Qiao, Taesic Kim, Liyan Qu Jan 2019

Rechargeable Multi - Cell Battery, Wei Qiao, Taesic Kim, Liyan Qu

Faculty Publications from the Department of Electrical and Computer Engineering

A method for power management of a multi-cell battery includes identifying a desired power value and voltage value, determining a battery voltage value and a battery current value for a battery, determining a number of battery banks from a plurality of battery banks to use for the battery, where each battery bank includes one or more battery cells (or battery modules), checking availability of each of the one or more battery cells (or battery modules), selecting one or more battery banks from the plurality of battery banks, where the selection of a battery bank is based on the availability of ...


Femtosecond Photon-Mediated Plasma Enhances Photosynthesis Of Plasmonic Nanostructures And Their Sers Applications, Peng Ran, Lan Jiang, Xin Li, Bo Li, Pei Zuo, Yongfeng Lu Jan 2019

Femtosecond Photon-Mediated Plasma Enhances Photosynthesis Of Plasmonic Nanostructures And Their Sers Applications, Peng Ran, Lan Jiang, Xin Li, Bo Li, Pei Zuo, Yongfeng Lu

Faculty Publications from the Department of Electrical and Computer Engineering

Laser ablation in liquid has proven to be a universal and green method to synthesize nanocrystals and fabricate functional nanostructures. This study demonstrates the superiority of femtosecond laser-mediated plasma in enhancing photoredox of metal cations for controllable fabrication of plasmonic nanostructures in liquid. Through employing upstream high energetic plasma during laser-induced microexplosions, single/three-electron photoreduction of metallic cations can readily occur without chemical reductants or capping agents. Experimental evidences demonstrate that this process exhibits higher photon utilization efficiency in yield of colloidal metal nanoparticles than direct irradiation of metallic precursors. Photogenerated hydrated electrons derived from strong ionization of silicon and ...


Self-Organized Twist-Heterostructures Via Aligned Van Der Waals Epitaxy And Solid-State Transformations, Peter Sutter, Rina Ibragimova, Hannu-Pekka Kosma, Bruce A. Parkinson, Eli A. Sutter Jan 2019

Self-Organized Twist-Heterostructures Via Aligned Van Der Waals Epitaxy And Solid-State Transformations, Peter Sutter, Rina Ibragimova, Hannu-Pekka Kosma, Bruce A. Parkinson, Eli A. Sutter

Faculty Publications from the Department of Electrical and Computer Engineering

Vertical van der Waals (vdW) heterostructures of 2D crystals with defined interlayer twist are of interest for band-structure engineering via twist moiré superlattice potentials. To date, twist-heterostructures have been realized by micromechanical stacking. Direct synthesis is hindered by the tendency toward equilibrium stacking without interlayer twist. Here, we demonstrate that growing a 2D crystal with fixed azimuthal alignment to the substrate followed by transformation of this intermediate enables a potentially scalable synthesis of twisted heterostructures. Microscopy during growth of ultrathin orthorhombic SnS on trigonal SnS2 shows that vdW epitaxy yields azimuthal order even for non-isotypic 2D crystals. Excess sulfur drives ...