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Low-Dimensional Materials and Devices 2021

作者： Sarollahi, Mirsaeid Allaparthi, Rohith Alhelais, Reem Aldawsari, Manal A. Refaei, Malak A. Maruf, Md Helal Uddin Ware, Morgan E. University of Arkansas Electrical Engineering Department 3217 Bell Engineering Center FayettevilleAR72701 United States University of Arkansas Microelectronics-Photonics Program 731 West Dickson Street FayettevilleAR72701 United States University of Arkansas Material Science and Engineering 731 West Dickson Street FayettevilleAR72701 United States Institute for Nanoscience and Engineering FayettevilleAR72701 United States

ISBN: (数字)9781510644397

ISBN: (纸本)9781510644380

The optical properties of periodic graded GaN/InGaN are studied. We have designed graded InGaN quantum well (QW) structures with the indium composition increasing then decreasing in a zigzag pattern. Through polarization doping, this naturally creates alternating p-type and n-type regions. Separate structures are designed by varying the number of repeating periods (1 to 3), while maintaining constant overall structure thicknesses. Calculation of the transition probabilities and the electron and hole wave-functions between the conduction band and the valence band reveals a complex energy structure which predicts the photoluminescence peaks for band to band transitions. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.

关键词： Optical properties

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Analysis of Nanoscale Deformation in GaAs(100): Towards Patterned Growth of Quantum Dots

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MRS Online Proceedings Library (OPL) 2011年第1期864卷 E5.7-E5.7页

作者： Curtis R. Taylor Eric A. Stach Ajay P. Malshe Gregory Salamo Department of Physics Microelectronics-photonics Program University of Arkansas Fayetteville AR 72703 U.S.A email: curtis.taylor@uark.edu National Center for Electron Microscopy Materials Science Division Lawrence Berkeley National Laboratory Berkeley CA 94720 U.S.A. Department of Mechanical Engineering Microelectronics-photonics Program University of Arkansas Fayetteville AR 72703 U.S.A. email: apm2@engr.uark.edu Department of Physics University of Arkansas Fayetteville AR 72703 U.S.A. Present address: School of Materials Engineering Purdue University West Lafayette IN 47907 U.S.A.

Nanoindentations were created in the GaAs(100) surface to act as strain centers for the controlled nucleation and patterning of InAs quantum dots. A systematic approach is taken to understand the indent deformation processes that may lead to precision patterning capabilities for a broad range of nanostructures. Indents were generated using loads below 450 μN with a sharp cube corner indenter. Site-specific cross-sectional thinning of nanoindents (down to 100 nm in size) has been achieved using the in-situ ‘lift-out’ technique. This allowed for observation of subsurface deformation by transmission electron microscopy (TEM). The crystal was observed to deform solely by dislocation activity with no evidence of amorphization, twinning, fracture, or phase transformation. It is shown that the single phase deformation of GaAs can be well characterized and controlled, which should allow for exploitation of the dislocation strain field to bias nucleation of self-assembled quantum dots.

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Optical and Atomic Force Microscopy Study of Non-covalently functionalized CVD Graphene

Optical and Atomic Force Microscopy Study of Non-covalently ...

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IEEE International Conference on Nano/Micro Engineered and Molecular Systems

作者： Abayomi Omolewu Guangyi Shi Tian Ryan Xiangbo Meng Uchechukwu Wejinya Microelectronics-Photonics Graduate Program University of Arkansas Fayetteville Arkansas USA Scics Peking University at Wuxi Wuxi China Chemistry and Biochemistry Department University of Arkansas Fayetteville Arkansas USA Department of Mechanical Engineering University of Arkansas Fayetteville Arkansas USA

Chemical functionalization is a method that is being explored to take advantage of the intriguing properties of graphene and its derivatives. Surfactant treatments have been successfully employed to non-covalently functionalize graphitic materials such as carbon nanotube and graphite. However, there is still need to investigate the surfactant treatment approach for commercially available chemical vapor deposited (CVD) graphene on silicon-silicon dioxide substrate. CVD graphene is one of the large-scale graphene available;hence, it is essential to understand how surfactants interact with it. This work presents the optical and atomic force microscopy study of non-covalently-functionalized graphene using Sodium Dodecyl Sulphate. CVD graphene on silicon/silicon dioxide (Si/SiO_2) substrates were treated with different surfactant concentrations for different times. Unlike other derivatives of graphene, like carbon nanotube and graphite where the delamination of graphene sheet from the substrate is not a major concern, results show that the stability of the CVD graphene on the substrate is highly dependent on the concentration of the surfactant used for modifying the surface of the graphene, and the duration of treatment. Higher concentration of surfactant treatment was achieved by dissolving the surfactant with water and isopropyl alcohol. The result also suggests that different concentrations of surfactant affect the surface roughness of the functionalized graphene.

关键词： Graphene Surfactants Substrates Delamination Nanoparticles Zinc oxide

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A Wafer-Level Packaging Approach for MEMS and Related Microsystems using Selective Laser-Assisted Bonding (LAB)

A Wafer-Level Packaging Approach for MEMS and Related Micros...

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Electronic Components and Technology Conference (ECTC)

作者： Ashwin Mohan Chad B. O'Neal Ajay P. Malshe Ron B. Foster Department of Mechanical Engineering University of Arkansas Fayetteville AR USA Department of Mechanical Engineering University of Arkansas Fayetteville AR Institute for Micromanufacturing Louisiana Tech University Ruston LA USA Microelectronics-Photonics Program University of Arkanasas Fayetteville AR USA

A wafer-level bonding technique for hermetic, near-hermetic & vacuum packaging of MEMS is proposed. Silicon wafers are metallized with an intermediate layer of gold on which a low temperature solder such as Pb37/Sn63 having a thickness of 50-100 mum is deposited. The bonding layer is deposited either by screen printing or eutectic preforms. Two identical wafers are aligned at the intermediate layer and a continuous wave CO 2 laser in combination with an X-Y translation stage is employed for selective heating of the silicon wafer to reflow the solder, bonding the wafers. The laser used had a wavelength of 10.6 mum with a spot size of 0.2-1.0 mm. The bonding temperature at the intermediate layer exceeded the reflow temperature of the eutectic Pb-Sn solder due to local laser heating effects, but the global average temperature was much lower (about 100degC). For a vacuum packaging approach the wafers were mounted on a custom-built wafer-mating fixture housed in a vacuum chamber maintained at a pressure of 10 -3 Torr. Optical, X-ray and acoustic microscopy were performed on the bonded wafer and pull tests on the diced packages to assess the quality of the solder bonds

关键词： Wafer scale integration Micromechanical devices Wafer bonding Temperature Packaging Silicon Heating Optical microscopy Vacuum technology Metallization

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Controlling the rotational behavior of bacterial flageller motors

Controlling the rotational behavior of bacterial flageller m...

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International Conference on Information and Automation (ICIA)

作者： Steve Tung Ryan Pooran Jin-Woo Kim Department of Mechanical Engineering University of Arkansas Little Rock Fayetteville AR USA Microelectronics-Photonics Program University of Arkansas Little Rock Fayetteville AR USA Department of Biological and Agricultural Engineering University of Arkansas Little Rock Fayetteville AR USA

Mutant strains of bacterial flagellar motors can be tethered to the sidewalls of microfluidic channels to perform mechanical functions. In most cases, the rotational behavior of the tethered motors must be properly controlled in order to achieve optimized performance. There are several approaches for carrying out this task but most of them involve techniques that affect the viability of the motors. The present paper describes the application of hydrodynamic loading to achieve cell rotation synchronization. This is a non-contact method that uses viscous drag force induced by a small fluid flow to either slow down or stop the motor rotation completely if necessary. No negative effect on the motors is observed when the loading time is kept short. By applying this method to a group of tethered motors, it is possible to stop and restart their rotation for the purpose of synchronization.

关键词： Loading Hydrodynamics Microfluidics Pumps Microorganisms Torque Synchronization

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Error Analysis of Breast Tumor Signature versus Skin Thickness at Microwave Frequencies

Error Analysis of Breast Tumor Signature versus Skin Thickne...

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2008 IEEE Antennas and Propagation Society International Symposium (APSURSI 2008), vol.6

作者： Douglas A. Woten Magda El-Shenawee Microelectronics-Photonics Program University of Arkansas Fayetteville AR USA Department of Electrical Engineering University of Arkansas Fayetteville AR USA

ISBN: (纸本)9781424420414

The effect of breast skin thickness on electromagnetic scattering is explored in this work using the Ansoft High Frequency Structure Simulator (HFSS) package. The signature of a spherical tumor of 1cm in diameter is compared to the skin effect. A more realistic inhomogeneous breast model is used based on a magnetic resonance imaging (MRI) scan. This model contains five regions;air, skin, fatty tissue, fibro-glandular tissue and the malignant tumor. The preliminary results of this work indicate that the tumor signature is larger than the effect of the skin in the backscatter for the case presented.

关键词： thickness of skin Microwave frequencies Error analysis signatures skin effect Breast Neoplasms Electromagnetic scattering backscattering skin epidermis (animal)

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Enhancement of material quality of (Si)GeSn films grown by SnCl4 precursor 228

Enhancement of material quality of (Si)GeSn films grown by S...

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Symposium on Semiconductors, Dielectrics, and Metals for Nanoelectronics 13 - 228th ECS Meeting

作者： Mosleh, A. Alher, M. Cousar, L. Abu-Safe, H. Dou, W. Grant, P.C. Al-Kabi, S. Ghetmiri, S.A. Alharthi, B. Tran, H. Du, W. Benamara, M. Li, B. Mortazavi, M. Yu, S.-Q. Naseem, H. Microelectronics-Photonics Program University of Arkansas FayettevilleAR72701 United States Electrical Engineering Department University of Arkansas FayettevilleAR72701 United States Mechanical Engineering Department University of Kerbala Kerbala Iraq Arktonics LLC FayettevilleAR72701 United States Department of Physics Wasit University Kut Iraq Institute for Nanoscience and Engineering University of Arkansas FayettevilleAR72701 United States Department of Chemistry and Physics University of Arkansas Pine Bluff Pine BluffAR71601 United States

ISBN: (纸本)9781607685395

The (Si)GeSn films have been grown with and without carrier gases on Si substrate using a cold-wall ultra-high vacuum chemical vapor deposition system. Material characterization of the films grown with Ar carrier gas using X-ray diffraction and transmission electron microscopy shows achievement of higher quality films. Optical characterization of the films with photoluminescence shows enhancement in material quality of the films at 350 and 400°C growth temperatures. Increase in the pressure results in higher Sn incorporation and higher photoluminescence intensity. Spectroscopic ellipsometry data confirms the change in the GeSn bandgap towards lower energies. © The Electrochemical Society.

关键词： High resolution transmission electron microscopy

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Generation and transmission of optical vortex beam in all-fiber optical system

Generation and transmission of optical vortex beam in all-fi...

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Specialty Optical Fibers, SOF 2022

作者： Nguyen, Hue Thi Stepniewski, Grzegorz Filipkowski, Adam Kasztelanic, Rafal Pysz, Dariusz Van Le, Hieu Stepien, Ryszard Klimczak, Mariusz Krolikowski, Wieslaw Buczynski, Ryszard Faculty of Physics University of Warsaw Pasteura 5 Warsaw02-093 Poland Department of Glass Lukasiewicz Research Network - Institute of Microelectronics and Photonics al. Lotnikow 32/46 Warsaw02-668 Poland Faculty of Natural Sciences Hong Duc University Quang Trung Thanhhoa565 Viet Nam Science Program Texas A&M University at Qatar Doha Qatar Laser Physics Centre Research School of Physics Australian National University CanberraACT0200 Australia

ISBN: (纸本)9781557528209

We present an experimental study on generation and transmission of optical vortex in an all-fiber system consisting of an antiresonant fiber butt-coupled with a dedicated fiber-based vortex generator. The influence of external perturbations like fiber bend, axial stress on structural stability of the transmitted vortex in the antiresonant fiber is also reported. © Optica Publishing Group 2022 © 2022 The Author(s)

关键词： Stability

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Fabrication of site specific amorphous/nanocrystalline silicon composite thin film for solar cells

Fabrication of site specific amorphous/nanocrystalline silic...

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2012 38th IEEE Photovoltaic Specialists Conference

作者： B. Newton H. Abu Safe M. Benemara S. Yu H. Naseem Microelectronics Photonics Program University of Arkansas Fayetteville Arkansas USA Department of Electrical Engineering University of Arkansas Fayetteville Fayetteville Arkansas USA Natural Science Division Lebanese American University Lebanon Institute of Nanoscale Material Science and Engineering University of Arkansas Fayetteville Arkansas USA

The absorption properties of amorphous silicon (α-Si) and the electron transport properties of nanocrystalline silicon are combined in a novel composite material for thin film silicon solar cells. In this work a composite film composed of α-Si with site specific areas of nanocrystalline material was created. Al was deposited through a SiO 2 template containing nanometer sized apertures with an approximate diameter of 250 nm onto an α-Si film supported by a ; crystalline silicon substrate. It was then annealed at 350°C. The annealing caused crystallization only at sites where the Al was in contact with the α-Si surface. The AIC created site specific three dimensional nanocrystalline structures embedded in a thin film of α-Si. After grain boundary passivation these nanocrystalline sites will provide pathways for charge carriers that are less defect dense than the α-Si film. TEM samples were fabricated from the composite film utilizing the focus ion beam. The growth characteristics of these 3D nanostructures and the α-Si thin film were characterized utilizing ESEM and the TEM.

关键词： Annealing USA Councils Substrates Platinum Measurement uncertainty Valves

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Direct growth of Ge_1-xSn_x films on Si using a cold-wall ultra-high vacuum chemical-vapor-deposition system

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FRONTIERS IN MATERIALS 2015年 2卷

作者： Mosleh, Aboozar Alher, Murtadha A. Cousar, Larry C. Du, Wei Ghetmiri, Seyed Amir Pham, Thach Grant, Joshua M. Sun, Greg Soref, Richard A. Li, Baohua Naseem, Hameed A. Yu, Shui-Qing Microelectronics-Photonics Graduate Program (μEP) University of Arkansas Fayetteville AR USA Department of Electrical Engineering University of Arkansas Fayetteville AR USA Mechanical Engineering Department University of Karbala Karbala Iraq Arktonics LLC Fayetteville AR USA Engineering-Physics Department Southern Arkansas University Magnolia AR USA Department of Engineering University of Massachusetts Boston Boston MA USA

Germanium tin alloys were grown directly on Si substrate at low temperatures using a cold wall ultra-high vacuum chemical-vapor-deposition system. Epitaxial growth was achieved by adopting commercial gas precursors of germane and stannic chloride without any carrier gases. The X-ray diffraction analysis showed the incorporation of Sn and that the Gei,Sn, films are fully epitaxial and strain relaxed. Tin incorporation in the Ge matrix was found to vary from 1 to 7%. The scanning electron microscopy images and energy-dispersive X-ray spectra maps show uniform Sn incorporation and continuous film growth. Investigation of deposition parameters shows that at high flow rates of stannic chloride the films were etched due to the production of HCI. The photoluminescence study shows the reduction of band-gap from 0.8 to 0.55 eV as a result of Sn incorporation.

关键词： chemical-vapor-deposition Si photonics Ge alloys photoluminescence Ge-Sn

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