1
|
Zhuang X, Deng Y, Zhang Y, Wang K, Chen Y, Gao S, Xu J, Wang L, Cheng X. A strategy to fabricate nanostructures with sub-nanometer line edge roughness. NANOTECHNOLOGY 2024; 35:495301. [PMID: 39137800 DOI: 10.1088/1361-6528/ad6e88] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2024] [Accepted: 08/13/2024] [Indexed: 08/15/2024]
Abstract
Line edge roughness (LER) has been an important issue in the nanofabrication research, especially in integrated circuits. Despite numerous research studies has made efforts on achieving smaller LER value, a strategy to achieve sub-nanometer level LER still remains challenging due to inability to deposit energy with a profile of sub-nanometer LER. In this work, we introduce a strategy to fabricate structures with sub-nanometer LER, specifically, we use scanning helium ion beam to expose hydrogen silsesquioxane (HSQ) resist on thin SiNx membrane (∼20 nm) and present the 0.16 nm spatial imaging resolution based on this suspended membrane geometric construction, which is characterized by scanning transmission electron microscope (STEM). The suspended membrane serves as an energy filter of helium ion beam and due to the elimination of backscattering induced secondary electrons, we can systematically study the factors that influences the LER of the fabricated nanostructures. Furthermore, we explore the parameters including step size, designed exposure linewidth (DEL), delivered dosage and resist thickness and choosing the high contrast developer, the process window allows to fabricate lines with 0.2 nm LER is determined. AFM measurement and simulation work further reveal that at specific beam step size and DEL, the nanostructures with minimum LER can only be fabricated at specific resist thickness and dosage.
Collapse
Affiliation(s)
- Xin Zhuang
- Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
- Shenzhen Key Laboratory of Nanoimprint Technology, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong Special Administrative Region of China, People's Republic of China
| | - Yunsheng Deng
- Pico Center and SUSTech Core Research Facilities, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
| | - Yue Zhang
- Lyra Lab, Tencent Music Entertainment, Shenzhen 518000, People's Republic of China
| | - Kaimin Wang
- Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
- Shenzhen Key Laboratory of Nanoimprint Technology, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
| | - Yulong Chen
- Industrialization Center of Micro & Nano ICs and Devices, Sino-German College of Intelligent Manufacturing, Shenzhen Technology University, Shenzhen 518118, People's Republic of China
| | - Shiyang Gao
- Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
- Shenzhen Key Laboratory of Nanoimprint Technology, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
| | - Jingfu Xu
- Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
- Shenzhen Key Laboratory of Nanoimprint Technology, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
| | - Liqiu Wang
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong Special Administrative Region of China, People's Republic of China
- Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hong Kong Special Administrative Region of China, People's Republic of China
| | - Xing Cheng
- Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
- Shenzhen Key Laboratory of Nanoimprint Technology, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
| |
Collapse
|
2
|
Raja SN, Jain S, Kipen J, Jaldén J, Stemme G, Herland A, Niklaus F. Electromigrated Gold Nanogap Tunnel Junction Arrays: Fabrication and Electrical Behavior in Liquid and Gaseous Media. ACS APPLIED MATERIALS & INTERFACES 2024; 16:37131-37146. [PMID: 38954436 PMCID: PMC11261569 DOI: 10.1021/acsami.4c03282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2024] [Revised: 06/19/2024] [Accepted: 06/19/2024] [Indexed: 07/04/2024]
Abstract
Tunnel junctions have been suggested as high-throughput electronic single molecule sensors in liquids with several seminal experiments conducted using break junctions with reconfigurable gaps. For practical single molecule sensing applications, arrays of on-chip integrated fixed-gap tunnel junctions that can be built into compact systems are preferable. Fabricating nanogaps by electromigration is one of the most promising approaches to realize on-chip integrated tunnel junction sensors. However, the electrical behavior of fixed-gap tunnel junctions immersed in liquid media has not been systematically studied to date, and the formation of electromigrated nanogap tunnel junctions in liquid media has not yet been demonstrated. In this work, we perform a comparative study of the formation and electrical behavior of arrays of gold nanogap tunnel junctions made by feedback-controlled electromigration immersed in various liquid and gaseous media (deionized water, mesitylene, ethanol, nitrogen, and air). We demonstrate that tunnel junctions can be obtained from microfabricated gold nanoconstrictions inside liquid media. Electromigration of junctions in air produces the highest yield (61-67%), electromigration in deionized water and mesitylene results in a lower yield than in air (44-48%), whereas electromigration in ethanol fails to produce viable tunnel junctions due to interfering electrochemical processes. We map out the stability of the conductance characteristics of the resulting tunnel junctions and identify medium-specific operational conditions that have an impact on the yield of forming stable junctions. Furthermore, we highlight the unique challenges associated with working with arrays of large numbers of tunnel junctions in batches. Our findings will inform future efforts to build single molecule sensors using on-chip integrated tunnel junctions.
Collapse
Affiliation(s)
- Shyamprasad N. Raja
- Division
of Micro and Nanosystems (MST), School of Electrical Engineering and
Computer Science (EECS), KTH Royal Institute
of Technology, SE-10044 Stockholm, Sweden
| | - Saumey Jain
- Division
of Micro and Nanosystems (MST), School of Electrical Engineering and
Computer Science (EECS), KTH Royal Institute
of Technology, SE-10044 Stockholm, Sweden
- Division
of Nanobiotechnology, SciLifeLab, Department of Protein Science, School
of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden
| | - Javier Kipen
- Division
of Information Science and Engineering (ISE), School of Electrical
Engineering and Computer Science (EECS), KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden
| | - Joakim Jaldén
- Division
of Information Science and Engineering (ISE), School of Electrical
Engineering and Computer Science (EECS), KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden
| | - Göran Stemme
- Division
of Micro and Nanosystems (MST), School of Electrical Engineering and
Computer Science (EECS), KTH Royal Institute
of Technology, SE-10044 Stockholm, Sweden
| | - Anna Herland
- Division
of Nanobiotechnology, SciLifeLab, Department of Protein Science, School
of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden
- AIMES-Center
for the Advancement of Integrated Medical and Engineering Sciences,
Department of Neuroscience, Karolinska Institute, SE-17177 Solna, Sweden
| | - Frank Niklaus
- Division
of Micro and Nanosystems (MST), School of Electrical Engineering and
Computer Science (EECS), KTH Royal Institute
of Technology, SE-10044 Stockholm, Sweden
| |
Collapse
|
3
|
Raja SN, Jain S, Kipen J, Jaldén J, Stemme G, Herland A, Niklaus F. High-bandwidth low-current measurement system for automated and scalable probing of tunnel junctions in liquids. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2024; 95:074710. [PMID: 39037302 DOI: 10.1063/5.0204188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Accepted: 07/06/2024] [Indexed: 07/23/2024]
Abstract
Tunnel junctions have long been used to immobilize and study the electronic transport properties of single molecules. The sensitivity of tunneling currents to entities in the tunneling gap has generated interest in developing electronic biosensors with single molecule resolution. Tunnel junctions can, for example, be used for sensing bound or unbound DNA, RNA, amino acids, and proteins in liquids. However, manufacturing technologies for on-chip integrated arrays of tunnel junction sensors are still in their infancy, and scalable measurement strategies that allow the measurement of large numbers of tunneling junctions are required to facilitate progress. Here, we describe an experimental setup to perform scalable, high-bandwidth (>10 kHz) measurements of low currents (pA-nA) in arrays of on-chip integrated tunnel junctions immersed in various liquid media. Leveraging a commercially available compact 100 kHz bandwidth low-current measurement instrument, we developed a custom two-terminal probe on which the amplifier is directly mounted to decrease parasitic probe capacitances to sub-pF levels. We also integrated a motorized three-axis stage, which could be powered down using software control, inside the Faraday cage of the setup. This enabled automated data acquisition on arrays of tunnel junctions without worsening the noise floor despite being inside the Faraday cage. A deliberately positioned air gap in the fluidic path ensured liquid perfusion to the chip from outside the Faraday cage without coupling in additional noise. We demonstrate the performance of our setup using rapid current switching observed in electromigrated gold tunnel junctions immersed in deionized water.
Collapse
Affiliation(s)
- Shyamprasad N Raja
- Division of Micro and Nanosystems, KTH Royal Institute of Technology, Stockholm SE-100 44, Sweden
| | - Saumey Jain
- Division of Micro and Nanosystems, KTH Royal Institute of Technology, Stockholm SE-100 44, Sweden
- Division of Nanobiotechnology, SciLife Lab, KTH Royal Institute of Technology, Stockholm SE-100 44, Sweden
| | - Javier Kipen
- Division of Information Science and Engineering, KTH Royal Institute of Technology, Stockholm SE-100 44, Sweden
| | - Joakim Jaldén
- Division of Information Science and Engineering, KTH Royal Institute of Technology, Stockholm SE-100 44, Sweden
| | - Göran Stemme
- Division of Micro and Nanosystems, KTH Royal Institute of Technology, Stockholm SE-100 44, Sweden
| | - Anna Herland
- Division of Nanobiotechnology, SciLife Lab, KTH Royal Institute of Technology, Stockholm SE-100 44, Sweden
- AIMES-Center for the Advancement of Integrated Medical and Engineering Sciences, Department of Neuroscience, Karolinska Institute, SE-171 77 Solna, Sweden
| | - Frank Niklaus
- Division of Micro and Nanosystems, KTH Royal Institute of Technology, Stockholm SE-100 44, Sweden
| |
Collapse
|
4
|
Li T, Bandari VK, Schmidt OG. Molecular Electronics: Creating and Bridging Molecular Junctions and Promoting Its Commercialization. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2209088. [PMID: 36512432 DOI: 10.1002/adma.202209088] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2022] [Revised: 11/28/2022] [Indexed: 06/02/2023]
Abstract
Molecular electronics is driven by the dream of expanding Moore's law to the molecular level for next-generation electronics through incorporating individual or ensemble molecules into electronic circuits. For nearly 50 years, numerous efforts have been made to explore the intrinsic properties of molecules and develop diverse fascinating molecular electronic devices with the desired functionalities. The flourishing of molecular electronics is inseparable from the development of various elegant methodologies for creating nanogap electrodes and bridging the nanogap with molecules. This review first focuses on the techniques for making lateral and vertical nanogap electrodes by breaking, narrowing, and fixed modes, and highlights their capabilities, applications, merits, and shortcomings. After summarizing the approaches of growing single molecules or molecular layers on the electrodes, the methods of constructing a complete molecular circuit are comprehensively grouped into three categories: 1) directly bridging one-molecule-electrode component with another electrode, 2) physically bridging two-molecule-electrode components, and 3) chemically bridging two-molecule-electrode components. Finally, the current state of molecular circuit integration and commercialization is discussed and perspectives are provided, hoping to encourage the community to accelerate the realization of fully scalable molecular electronics for a new era of integrated microsystems and applications.
Collapse
Affiliation(s)
- Tianming Li
- Research Center for Materials, Architectures and Integration of Nanomembranes (MAIN), Chemnitz University of Technology, 09126, Chemnitz, Germany
- Material Systems for Nanoelectronics, Chemnitz University of Technology, 09111, Chemnitz, Germany
| | - Vineeth Kumar Bandari
- Research Center for Materials, Architectures and Integration of Nanomembranes (MAIN), Chemnitz University of Technology, 09126, Chemnitz, Germany
- Material Systems for Nanoelectronics, Chemnitz University of Technology, 09111, Chemnitz, Germany
| | - Oliver G Schmidt
- Research Center for Materials, Architectures and Integration of Nanomembranes (MAIN), Chemnitz University of Technology, 09126, Chemnitz, Germany
- Material Systems for Nanoelectronics, Chemnitz University of Technology, 09111, Chemnitz, Germany
- Nanophysics, Dresden University of Technology, 01069, Dresden, Germany
| |
Collapse
|
5
|
Wei Y, Chen F, Huang R, Zhao J, Zhao H, Wang J, Li M, Zhang J. Fast Response GaN Nanoscale Air Channel Diodes with Highly Stable 10 mA Output Current toward Wafer-Scale Fabrication. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023:e2206385. [PMID: 37078799 DOI: 10.1002/advs.202206385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 02/14/2023] [Indexed: 05/03/2023]
Abstract
Nanoscale air channel transistors (NACTs) have received significant attention due to their remarkable high-frequency performance and high switching speed, which is enabled by the ballistic transport of electrons in sub-100 nm air channels. Despite these advantages, NACTs are still limited by low currents and instability compared to solid-state devices. GaN, with its low electron affinity, strong thermal and chemical stability, and high breakdown electric field, presents an appealing candidate as a field emission material. Here, a vertical GaN nanoscale air channel diode (NACD) with a 50 nm air channel is reported, fabricated by low-cost IC-compatible manufacturing technologies on a 2-inch sapphire wafer. The device boasts a record field emission current of 11 mA at 10 V in the air and exhibits outstanding stability during cyclic, long-term, and pulsed voltage testing. Additionally, it displays fast switching characteristics and good repeatability with a response time of fewer than 10 ns. Moreover, the temperature-dependent performance of the device can guide the design of GaN NACTs for applications in extreme conditions. The research holds great promise for large current NACTs and will speed up their practical implementation.
Collapse
Affiliation(s)
- Yazhou Wei
- School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 611731, China
| | - Feiliang Chen
- School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 611731, China
- Yangtze Delta Region Institute, University of Electronic Science and Technology of China, Huzhou, 313000, China
| | - Ruihan Huang
- School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 611731, China
| | - Jianpeng Zhao
- School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 611731, China
| | - Haiquan Zhao
- School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 611731, China
| | - Jiachao Wang
- School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 611731, China
| | - Mo Li
- School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 611731, China
- Yangtze Delta Region Institute, University of Electronic Science and Technology of China, Huzhou, 313000, China
| | - Jian Zhang
- School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 611731, China
- Yangtze Delta Region Institute, University of Electronic Science and Technology of China, Huzhou, 313000, China
| |
Collapse
|
6
|
Cheng T, Zhu Z, Wang X, Zhu L, Li A, Jiang L, Cao Y. Atomic layer deposition assisted fabrication of large-scale metal nanogaps for surface enhanced Raman scattering. NANOTECHNOLOGY 2023; 34:265301. [PMID: 36996801 DOI: 10.1088/1361-6528/acc8d9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Accepted: 03/30/2023] [Indexed: 06/19/2023]
Abstract
Metal nanogaps can confine electromagnetic field into extremely small volumes, exhibiting strong surface plasmon resonance effect. Therefore, metal nanogaps show great prospects in enhancing light-matter interaction. However, it is still challenging to fabricate large-scale (centimeter scale) nanogaps with precise control of gap size at nanoscale, limiting the practical applications of metal nanogaps. In this work, we proposed a facile and economic strategy to fabricate large-scale sub-10 nm Ag nanogaps by the combination of atomic layer deposition (ALD) and mechanical rolling. The plasmonic nanogaps can be formed in the compacted Ag film by the sacrificial Al2O3deposited via ALD. The size of nanogaps are determined by the twice thickness of Al2O3with nanometric control. Raman results show that SERS activity depends closely on the nanogap size, and 4 nm Ag nanogaps exhibit the best SERS activity. By combining with other porous metal substrates, various sub-10 nm metal nanogaps can be fabricated over large scale. Therefore, this strategy will have significant implications for the preparation of nanogaps and enhanced spectroscopy.
Collapse
Affiliation(s)
- Tangjie Cheng
- Institute of Micro-nano Photonics and Quantum Manipulation, School of Science, Nanjing University of Science and Technology, Nanjing, 210094, People's Republic of China
| | - Zebin Zhu
- Institute of Micro-nano Photonics and Quantum Manipulation, School of Science, Nanjing University of Science and Technology, Nanjing, 210094, People's Republic of China
| | - Xinxin Wang
- Institute of Micro-nano Photonics and Quantum Manipulation, School of Science, Nanjing University of Science and Technology, Nanjing, 210094, People's Republic of China
| | - Lin Zhu
- National Laboratory of Solid State Microstructures, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, Nanjing University, Nanjing, 210093, People's Republic of China
| | - Aidong Li
- National Laboratory of Solid State Microstructures, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, Nanjing University, Nanjing, 210093, People's Republic of China
| | - Liyong Jiang
- Institute of Micro-nano Photonics and Quantum Manipulation, School of Science, Nanjing University of Science and Technology, Nanjing, 210094, People's Republic of China
| | - Yanqiang Cao
- Institute of Micro-nano Photonics and Quantum Manipulation, School of Science, Nanjing University of Science and Technology, Nanjing, 210094, People's Republic of China
| |
Collapse
|
7
|
He Q, Tang L. Sub-5 nm nanogap electrodes towards single-molecular biosensing. Biosens Bioelectron 2022; 213:114486. [PMID: 35749816 DOI: 10.1016/j.bios.2022.114486] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 06/10/2022] [Accepted: 06/14/2022] [Indexed: 11/02/2022]
Abstract
Nanogap electrodes (NGEs) with sub-5 nm gap has been widely used in single-molecule sensing and sequencing, with the characteristics of label-free, high sensitivity, rapid detection and low-cost. However, the fabrication of sub-5 nm gap electrodes with high controllability and reproducibility still remains a great challenge that impedes the experimental research and the commercialization of the nanogap device. Here, we review the common currently used fabrication methods of nanogap electrodes, such as gap narrowing deposition, mechanical controllable break junctions and the fabrication methods combined with nanopore or nanochannel. We then highlight the typical applications of nanogap electrodes in biological/chemical sensing fields, including single molecule recognition, single molecule sequencing and chemical kinetics analysis. Finally, the challenges of nanogap electrodes in single molecule sensing/sequencing are outlined and the future directions for sensing perspectives are suggested.
Collapse
Affiliation(s)
- Qiuxiang He
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, Zhejiang University, Hangzhou, 310027, China
| | - Longhua Tang
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, Zhejiang University, Hangzhou, 310027, China.
| |
Collapse
|
8
|
Guo J, Wang Y, Zhang H, Zhao Y. Conductive Materials with Elaborate Micro/Nanostructures for Bioelectronics. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2110024. [PMID: 35081264 DOI: 10.1002/adma.202110024] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 01/21/2022] [Indexed: 06/14/2023]
Abstract
Bioelectronics, an emerging field with the mutual penetration of biological systems and electronic sciences, allows the quantitative analysis of complicated biosignals together with the dynamic regulation of fateful biological functions. In this area, the development of conductive materials with elaborate micro/nanostructures has been of great significance to the improvement of high-performance bioelectronic devices. Thus, here, a comprehensive and up-to-date summary of relevant research studies on the fabrication and properties of conductive materials with micro/nanostructures and their promising applications and future opportunities in bioelectronic applications is presented. In addition, a critical analysis of the current opportunities and challenges regarding the future developments of conductive materials with elaborate micro/nanostructures for bioelectronic applications is also presented.
Collapse
Affiliation(s)
- Jiahui Guo
- Department of Rheumatology and Immunology, Institute of Translational Medicine, The Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, 210008, China
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing, 210096, China
| | - Yu Wang
- Department of Rheumatology and Immunology, Institute of Translational Medicine, The Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, 210008, China
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing, 210096, China
| | - Hui Zhang
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing, 210096, China
| | - Yuanjin Zhao
- Department of Rheumatology and Immunology, Institute of Translational Medicine, The Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, 210008, China
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing, 210096, China
- Oujiang Laboratory (Zhejiang Lab for Regenerative Medicine, Vision and Brain Health), Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou, Zhejiang, 325001, China
- Institute for Stem Cell and Regeneration, Chinese Academy of Science, Beijing, 100101, China
| |
Collapse
|
9
|
Luo S, Hoff BH, Maier SA, de Mello JC. Scalable Fabrication of Metallic Nanogaps at the Sub-10 nm Level. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2021; 8:e2102756. [PMID: 34719889 PMCID: PMC8693066 DOI: 10.1002/advs.202102756] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 08/09/2021] [Indexed: 06/01/2023]
Abstract
Metallic nanogaps with metal-metal separations of less than 10 nm have many applications in nanoscale photonics and electronics. However, their fabrication remains a considerable challenge, especially for applications that require patterning of nanoscale features over macroscopic length-scales. Here, some of the most promising techniques for nanogap fabrication are evaluated, covering established technologies such as photolithography, electron-beam lithography (EBL), and focused ion beam (FIB) milling, plus a number of newer methods that use novel electrochemical and mechanical means to effect the patterning. The physical principles behind each method are reviewed and their strengths and limitations for nanogap patterning in terms of resolution, fidelity, speed, ease of implementation, versatility, and scalability to large substrate sizes are discussed.
Collapse
Affiliation(s)
- Sihai Luo
- Department of ChemistryNorwegian University of Science and Technology (NTNU)TrondheimNO‐7491Norway
| | - Bård H. Hoff
- Department of ChemistryNorwegian University of Science and Technology (NTNU)TrondheimNO‐7491Norway
| | - Stefan A. Maier
- Nano‐Institute MunichFaculty of PhysicsLudwig‐Maximilians‐Universität MünchenMünchen80539Germany
- Blackett LaboratoryDepartment of PhysicsImperial College LondonLondonSW7 2AZUK
| | - John C. de Mello
- Department of ChemistryNorwegian University of Science and Technology (NTNU)TrondheimNO‐7491Norway
| |
Collapse
|
10
|
Zhou S, Chen K, Cole MT, Li Z, Li M, Chen J, Lienau C, Li C, Dai Q. Ultrafast Electron Tunneling Devices-From Electric-Field Driven to Optical-Field Driven. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2101449. [PMID: 34240495 DOI: 10.1002/adma.202101449] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2021] [Revised: 04/05/2021] [Indexed: 06/13/2023]
Abstract
The search for ever higher frequency information processing has become an area of intense research activity within the micro, nano, and optoelectronics communities. Compared to conventional semiconductor-based diffusive transport electron devices, electron tunneling devices provide significantly faster response times due to near-instantaneous tunneling that occurs at sub-femtosecond timescales. As a result, the enhanced performance of electron tunneling devices is demonstrated, time and again, to reimagine a wide variety of traditional electronic devices with a variety of new "lightwave electronics" emerging, each capable of reducing the electron transport channel transit time down to attosecond timescales. In response to unprecedented rapid progress within this field, here the current state-of-the-art in electron tunneling devices is reviewed, current challenges and opportunities are highlighted, and possible future research directions are identified.
Collapse
Affiliation(s)
- Shenghan Zhou
- CAS Key Laboratory of Nanophotonic Materials and Devices, CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, P. R. China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Ke Chen
- CAS Key Laboratory of Nanophotonic Materials and Devices, CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, P. R. China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Matthew Thomas Cole
- Department of Electronic and Electrical Engineering, University of Bath, Bath, BA2 7AY, UK
| | - Zhenjun Li
- CAS Key Laboratory of Nanophotonic Materials and Devices, CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, P. R. China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Mo Li
- School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 611731, P. R. China
| | - Jun Chen
- State Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Province Key Laboratory of Display Material and Technology, School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou, 510275, P. R. China
| | - Christoph Lienau
- Institut für Physik, Center of Interface Science, Carl von Ossietzky Universität, 26129, Oldenburg, Germany
| | - Chi Li
- CAS Key Laboratory of Nanophotonic Materials and Devices, CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, P. R. China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Qing Dai
- CAS Key Laboratory of Nanophotonic Materials and Devices, CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, P. R. China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| |
Collapse
|
11
|
Luo S, Mancini A, Berté R, Hoff BH, Maier SA, de Mello JC. Massively Parallel Arrays of Size-Controlled Metallic Nanogaps with Gap-Widths Down to the Sub-3-nm Level. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2100491. [PMID: 33939199 DOI: 10.1002/adma.202100491] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 02/25/2021] [Indexed: 06/12/2023]
Abstract
Metallic nanogaps (MNGs) are fundamental components of nanoscale photonic and electronic devices. However, the lack of reproducible, high-yield fabrication methods with nanometric control over the gap-size has hindered practical applications. A patterning technique based on molecular self-assembly and physical peeling is reported here that allows the gap-width to be tuned from more than 30 nm to less than 3 nm. The ability of the technique to define sub-3-nm gaps between dissimilar metals permits the easy fabrication of molecular rectifiers, in which conductive molecules bridge metals with differing work functions. A method is further described for fabricating massively parallel nanogap arrays containing hundreds of millions of ring-shaped nanogaps, in which nanometric size control is maintained over large patterning areas of up to a square centimeter. The arrays exhibit strong plasmonic resonances under visible light illumination and act as high-performance substrates for surface-enhanced Raman spectroscopy, with high enhancement factors of up to 3 × 108 relative to thin gold films. The methods described here extend the range of metallic nanostructures that can be fabricated over large areas, and are likely to find many applications in molecular electronics, plasmonics, and biosensing.
Collapse
Affiliation(s)
- Sihai Luo
- Department of Chemistry, Norwegian University of Science and Technology (NTNU), NO-7491, Trondheim, Norway
| | - Andrea Mancini
- Nano-Institute Munich, Faculty of Physics, Ludwig-Maximilians-Universität München, München, 80539, Germany
| | - Rodrigo Berté
- Nano-Institute Munich, Faculty of Physics, Ludwig-Maximilians-Universität München, München, 80539, Germany
| | - Bård H Hoff
- Department of Chemistry, Norwegian University of Science and Technology (NTNU), NO-7491, Trondheim, Norway
| | - Stefan A Maier
- Nano-Institute Munich, Faculty of Physics, Ludwig-Maximilians-Universität München, München, 80539, Germany
- Blackett Laboratory, Department of Physics, Imperial College London, London, SW7 2AZ, UK
| | - John C de Mello
- Department of Chemistry, Norwegian University of Science and Technology (NTNU), NO-7491, Trondheim, Norway
| |
Collapse
|
12
|
Li P, Chen S, Dai H, Yang Z, Chen Z, Wang Y, Chen Y, Peng W, Shan W, Duan H. Recent advances in focused ion beam nanofabrication for nanostructures and devices: fundamentals and applications. NANOSCALE 2021; 13:1529-1565. [PMID: 33432962 DOI: 10.1039/d0nr07539f] [Citation(s) in RCA: 53] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The past few decades have witnessed growing research interest in developing powerful nanofabrication technologies for three-dimensional (3D) structures and devices to achieve nano-scale and nano-precision manufacturing. Among the various fabrication techniques, focused ion beam (FIB) nanofabrication has been established as a well-suited and promising technique in nearly all fields of nanotechnology for the fabrication of 3D nanostructures and devices because of increasing demands from industry and research. In this article, a series of FIB nanofabrication factors related to the fabrication of 3D nanostructures and devices, including mechanisms, instruments, processes, and typical applications of FIB nanofabrication, are systematically summarized and analyzed in detail. Additionally, current challenges and future development trends of FIB nanofabrication in this field are also given. This work intends to provide guidance for practitioners, researchers, or engineers who wish to learn more about the FIB nanofabrication technology that is driving the revolution in 3D nanostructures and devices.
Collapse
Affiliation(s)
- Ping Li
- National Engineering Research Centre for High Efficiency Grinding, College of Mechanical and Vehicle Engineering, Hunan University, Changsha 410082, P. R. China.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
13
|
Arjmandi-Tash H, van Deursen PM, Bellunato A, de Sere C, Overchenko Z, Gupta KBS, Schneider GF. Supramolecular Multilayered Templates for Fabricating Nanometer-Precise Spacings: Implications for the Next-Generation of Devices Integrating Nanogap/Nanochannel Components. ACS APPLIED NANO MATERIALS 2020; 3:10586-10590. [PMID: 33283172 PMCID: PMC7706106 DOI: 10.1021/acsanm.0c01578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Accepted: 09/03/2020] [Indexed: 06/12/2023]
Abstract
Molecular transistors, electromagnetic waveguides, plasmonic devices, and novel generations of nanofluidic channels comprise precisely separated gaps of nanometric and subnanometric spacing. Nonetheless, fabricating a nanogap/nanochannel is a technological challenge, currently tackled by several approaches such as breakdown electromigration and lithography. The aforementioned techniques, though, are limited, respectively, in terms of gap stability and ultimate resolution. Here, nanogaps/nanochannels are templated via the microtomy of metallic thin films embedded in a polymer matrix and precisely separated by a nanometric, sacrificial layer of polyelectrolytes grown via the layer-by-layer (LbL) approach. The versatility of the LbL technique, both in terms of the number of layers and composition of polyelectrolytes, allows to finely tune the spacing across the gap; the LbL template can further be removed by plasma etching. Our findings pave the path toward the realization of molecularly defined functional spacings at the nanometer-scale for the modular implementation of devices integrating nanogap/nanochannel components.
Collapse
|
14
|
D'Angelo P, Marasso SL, Verna A, Ballesio A, Parmeggiani M, Sanginario A, Tarabella G, Demarchi D, Pirri CF, Cocuzza M, Iannotta S. Scaling Organic Electrochemical Transistors Down to Nanosized Channels. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2019; 15:e1902332. [PMID: 31441219 DOI: 10.1002/smll.201902332] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Revised: 07/25/2019] [Indexed: 06/10/2023]
Abstract
The perspective of downscaling organic electrochemical transistors (OECTs) in the nanorange is approached by depositing poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) on electrodes with a nanogap designed and fabricated by electromigration induced break junction (EIBJ) technique. The electrical response of the fabricated devices is obtained by acquiring transfer characteristics in order to clarify the specific main characteristics of OECTs with sub-micrometer-sized active channels (nanogap-OECTs). On the basis of their electrical response to different scan times, the nanogap-OECT shows a maximum transconductance unaffected upon changing scan times in the time window from 1 s to 100 µs, meaning that fast varying signals can be easily acquired with unchanged amplifying performance. Hence, the scaling down of the channel size to the nanometer scale leads to a geometrical paradigm that minimizes effects on device response due to the cationic diffusion into the polymeric channel. A comprehensive study of these features is carried out by an electrochemical impedance spectroscopy (EIS) study, complemented by a quantitative analysis made by equivalent circuits. The propagation of a redox front into the polymer bulk due to ionic diffusion also known as the "intercalation pseudocapacitance" is identified as a limiting factor for the transduction dynamics.
Collapse
Affiliation(s)
- Pasquale D'Angelo
- Consiglio Nazionale delle Ricerche-Istituto dei Materiali per l'Elettronica ed il Magnetismo (IMEM), P.co Area delle Scienze 37/A, Parma, 43124, Italy
| | - Simone L Marasso
- Consiglio Nazionale delle Ricerche-Istituto dei Materiali per l'Elettronica ed il Magnetismo (IMEM), P.co Area delle Scienze 37/A, Parma, 43124, Italy
- Chilab-Materials and Microsystems Laboratory, Department of Applied Science and Technology (DISAT), Politecnico di Torino, Chivasso (Turin), 10034, Italy
| | - Alessio Verna
- Chilab-Materials and Microsystems Laboratory, Department of Applied Science and Technology (DISAT), Politecnico di Torino, Chivasso (Turin), 10034, Italy
| | - Alberto Ballesio
- Chilab-Materials and Microsystems Laboratory, Department of Applied Science and Technology (DISAT), Politecnico di Torino, Chivasso (Turin), 10034, Italy
| | - Matteo Parmeggiani
- Chilab-Materials and Microsystems Laboratory, Department of Applied Science and Technology (DISAT), Politecnico di Torino, Chivasso (Turin), 10034, Italy
- Center for Sustainable Future Technologies, Italian Institute of Technology, Turin, 10129, Italy
| | - Alessandro Sanginario
- Electronic and Telecommunication Department, Politecnico di Torino, Turin, 10129, Italy
| | | | - Danilo Demarchi
- Electronic and Telecommunication Department, Politecnico di Torino, Turin, 10129, Italy
| | - Candido F Pirri
- Chilab-Materials and Microsystems Laboratory, Department of Applied Science and Technology (DISAT), Politecnico di Torino, Chivasso (Turin), 10034, Italy
- Center for Sustainable Future Technologies, Italian Institute of Technology, Turin, 10129, Italy
| | - Matteo Cocuzza
- Consiglio Nazionale delle Ricerche-Istituto dei Materiali per l'Elettronica ed il Magnetismo (IMEM), P.co Area delle Scienze 37/A, Parma, 43124, Italy
- Chilab-Materials and Microsystems Laboratory, Department of Applied Science and Technology (DISAT), Politecnico di Torino, Chivasso (Turin), 10034, Italy
| | - Salvatore Iannotta
- Consiglio Nazionale delle Ricerche-Istituto dei Materiali per l'Elettronica ed il Magnetismo (IMEM), P.co Area delle Scienze 37/A, Parma, 43124, Italy
| |
Collapse
|
15
|
Kano S, Kawazu T, Yamazaki A, Fujii M. Digital image analysis for measuring nanogap distance produced by adhesion lithography. NANOTECHNOLOGY 2019; 30:285303. [PMID: 30913554 DOI: 10.1088/1361-6528/ab134f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
A simple digital image analysis for measuring nanogap distance produced by adhesion lithography is proposed. Adhesion lithography produces metal electrodes with sub-15 nm undulated space and μm to mm scale width without using electron beam lithography. Although the process has been rapidly improved in recent years, there has been no generalized procedure to evaluate the nanogap distance. In this study, we propose a procedure to evaluate a nanogap electrode with large width/gap distance ratios (>1000). The procedure is to determine the average distance of nanogap space from the area and the perimeter of the space by the analysis of the grayscale image. This procedure excludes any arbitrariness of the estimation and gives quantitative comparison of nanogap electrodes produced by different processes.
Collapse
Affiliation(s)
- Shinya Kano
- Department of Electrical and Electronic Engineering, Kobe University, 1-1, Rokkodai, Nada, Kobe, Japan
| | | | | | | |
Collapse
|
16
|
Enrico A, Dubois V, Niklaus F, Stemme G. Scalable Manufacturing of Single Nanowire Devices Using Crack-Defined Shadow Mask Lithography. ACS APPLIED MATERIALS & INTERFACES 2019; 11:8217-8226. [PMID: 30698940 PMCID: PMC6426283 DOI: 10.1021/acsami.8b19410] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Accepted: 01/30/2019] [Indexed: 05/08/2023]
Abstract
Single nanowires (NWs) have a broad range of applications in nanoelectronics, nanomechanics, and nanophotonics, but, to date, no technique can produce single sub-20 nm wide NWs with electrical connections in a scalable fashion. In this work, we combine conventional optical and crack lithographies to generate single NW devices with controllable and predictable dimensions and placement and with individual electrical contacts to the NWs. We demonstrate NWs made of gold, platinum, palladium, tungsten, tin, and metal oxides. We have used conventional i-line stepper lithography with a nominal resolution of 365 nm to define crack lithography structures in a shadow mask for large-scale manufacturing of sub-20 nm wide NWs, which is a 20-fold improvement over the resolution that is possible with the utilized stepper lithography. Overall, the proposed method represents an effective approach to generate single NW devices with useful applications in electrochemistry, photonics, and gas- and biosensing.
Collapse
Affiliation(s)
- Alessandro Enrico
- Department of Micro and Nanosystems, School of Electrical
Engineering and Computer Science, KTH Royal
Institute of Technology, SE-10044 Stockholm, Sweden
| | | | - Frank Niklaus
- Department of Micro and Nanosystems, School of Electrical
Engineering and Computer Science, KTH Royal
Institute of Technology, SE-10044 Stockholm, Sweden
| | - Göran Stemme
- Department of Micro and Nanosystems, School of Electrical
Engineering and Computer Science, KTH Royal
Institute of Technology, SE-10044 Stockholm, Sweden
| |
Collapse
|
17
|
Yang Y, Gu C, Li J. Sub-5 nm Metal Nanogaps: Physical Properties, Fabrication Methods, and Device Applications. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2019; 15:e1804177. [PMID: 30589217 DOI: 10.1002/smll.201804177] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Revised: 11/29/2018] [Indexed: 05/26/2023]
Abstract
Sub-5 nm metal nanogaps have attracted widespread attention in physics, chemistry, material sciences, and biology due to their physical properties, including great plasmon-enhanced effects in light-matter interactions and charge tunneling, Coulomb blockade, and the Kondo effect under an electrical stimulus. These properties especially meet the needs of many cutting-edge devices, such as sensing, optical, molecular, and electronic devices. However, fabricating sub-5 nm nanogaps is still challenging at the present, and scaled and reliable fabrication, improved addressability, and multifunction integration are desired for further applications in commercial devices. The aim of this work is to provide a comprehensive overview of sub-5 nm nanogaps and to present recent advancements in metal nanogaps, including their physical properties, fabrication methods, and device applications, with the ultimate aim to further inspire scientists and engineers in their research.
Collapse
Affiliation(s)
- Yang Yang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
| | - Changzhi Gu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Junjie Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China
| |
Collapse
|
18
|
Dubois V, Raja SN, Gehring P, Caneva S, van der Zant HSJ, Niklaus F, Stemme G. Massively parallel fabrication of crack-defined gold break junctions featuring sub-3 nm gaps for molecular devices. Nat Commun 2018; 9:3433. [PMID: 30143636 PMCID: PMC6109151 DOI: 10.1038/s41467-018-05785-2] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Accepted: 07/25/2018] [Indexed: 11/08/2022] Open
Abstract
Break junctions provide tip-shaped contact electrodes that are fundamental components of nano and molecular electronics. However, the fabrication of break junctions remains notoriously time-consuming and difficult to parallelize. Here we demonstrate true parallel fabrication of gold break junctions featuring sub-3 nm gaps on the wafer-scale, by relying on a novel self-breaking mechanism based on controlled crack formation in notched bridge structures. We achieve fabrication densities as high as 7 million junctions per cm2, with fabrication yields of around 7% for obtaining crack-defined break junctions with sub-3 nm gaps of fixed gap width that exhibit electron tunneling. We also form molecular junctions using dithiol-terminated oligo(phenylene ethynylene) (OPE3) to demonstrate the feasibility of our approach for electrical probing of molecules down to liquid helium temperatures. Our technology opens a whole new range of experimental opportunities for nano and molecular electronics applications, by enabling very large-scale fabrication of solid-state break junctions.
Collapse
Affiliation(s)
- Valentin Dubois
- Department of Micro and Nanosystems (MST), School of Electrical Engineering and Computer Science (EECS), KTH Royal Institute of Technology, SE-10044, Stockholm, Sweden
| | - Shyamprasad N Raja
- Department of Micro and Nanosystems (MST), School of Electrical Engineering and Computer Science (EECS), KTH Royal Institute of Technology, SE-10044, Stockholm, Sweden
| | - Pascal Gehring
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ, Delft, The Netherlands
| | - Sabina Caneva
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ, Delft, The Netherlands
| | - Herre S J van der Zant
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ, Delft, The Netherlands
| | - Frank Niklaus
- Department of Micro and Nanosystems (MST), School of Electrical Engineering and Computer Science (EECS), KTH Royal Institute of Technology, SE-10044, Stockholm, Sweden.
| | - Göran Stemme
- Department of Micro and Nanosystems (MST), School of Electrical Engineering and Computer Science (EECS), KTH Royal Institute of Technology, SE-10044, Stockholm, Sweden.
| |
Collapse
|