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(a) Schematic of an EATEST device, with three main components highlighted in red, green and violet for the stator, the movable stage and specimen part, respectively. The detailed view in the inset shows a blue colored SiNW monolithically integrated between the specimen and stage part, where the latter constitutes a comb drive actuator together with the stator. The functional parts are separated from the handle layer by a 2 μm thick BOX. (b) SEM image of the EATEST device and the magnified view showing the integrated SiNW in the inset. The white arrows indicate the positions of the Si-beams stabilizing the structure during processing and VLS nanowire growth which are finally removed by FIB cutting.
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In this paper we demonstrate the fabrication and application of an electrostatic actuated tensile straining test (EATEST) device enabling strain engineering in individual suspended nanowires (NWs). Contrary to previously reported approaches, this special setup guarantees the application of pure uniaxial tensile strain with no shear component of the...
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In this paper we report thermal conductivity and piezoresistivity measurements of top-down fabricated highly boron doped (NA = 1.5 × 1019 cm−3) suspended Si nanowires. These measurements were performed in a cryogenic probe station respectively by using the 3 omega method and by in situ application of a longitudinal tensile stress to the nanowire un...
Silicon nanowires (SiNWs) have received attention in recent years due to their anomalous piezoresistive (PZR) effects. Although the PZR effects of SiNWs have been extensively researched, they are still not fully understood. Herein, we develop a new model of the PZR effects of SiNWs to characterize the PZR effects. First, the resistance of SiNW is m...
Citations
... As the bottom-up technology, the vapor-liquid-solid (VLS) method becomes a strong candidate to grow Si NWs in a dry atmosphere. 10,16 By changing the growth conditions, the morphology and crystallinity of Si NWs can be controlled because they grow epitaxially along crystal orientation. As the top-down technology, the combination of a maskless direct lithography technique using electron beam or atomic force microscope (AFM) and wet etching can be found. ...
This paper describes the influence of vacuum annealing on the mechanical characteristics of silicon (Si) nanowires (NWs) fabricated using focused ion beam (FIB) technologies. Two types of Si NWs having a cross-sectional one-side length or diameter ranging from 19 to 447 nm are prepared using the direct milling and Ga ion doping functions of FIB. The Si NWs prepared are annealed at 400–700 °C in high vacuum for 10 min, followed by quasi-static uniaxial tensile testing using a microelectromechanical system based tensile test system in a scanning electron microscope. All the Si NWs fracture in a brittle manner. Young's modulus of submicrometer-sized Si NWs shows both annealing and specimen size influences in the range from 120 to 170 GPa, whereas that of nano-sized Si NWs shows only annealing influence in the range from 60 to 110 GPa. Tensile strength scatters greatly, ranging from 1.0 to 7.2 GPa, which increases with increasing the NW size. A transmission electron microscope and an atomic force microscope suggest that, by annealing, recrystallization happens in the damaged layer introduced by FIB milling and the NW surface morphology changes due to its recrystallization and gallium (Ga) ion evaporation. Fracture origin is discussed through the comparison between surface roughness and crack length estimated by the Griffith theory of brittle fracture.
... The lever amplifies the specimen elongation by a factor of 91, and the deflection of the lever that indicates the amplified specimen elongation can be estimated by image processing using a CCD camera. By using the similar test device, the mechanical and [50][51][52] electrical properties of Si and its related nanowires produced by a CVD method were evaluated [48,49]. Fujii et al. [50][51][52] designed a Si MEMS device for nanomaterials as illustrated in Fig. 5 along with the photograph of the produced device. ...
By virtue of a great progress of semiconductor fabrication technologies, micro electro‐mechanical systems (MEMS) have been developed for a wide variety of industries. For reliability of MEMS, micromaterials in MEMS need to be examined experimentally, and the obtained results need to be reflected in the design of MEMS. In addition, with the benefit of such the MEMS technology, nowadays mechanical characteristics of nanomaterials have been evaluated precisely. Nanoscale mechanical testing provides an opportunity to find new unique physical phenomena, such as plastic deformation in Si at intermediate temperatures. In this review paper, mechanical testing technologies developed for investigating micro and nanoscale materials are reviewed. Then, mechanical characteristics of Si and other materials evaluated using the micro and nano mechanical testing technologies are introduced. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.
... In fields like photonics [1,2], mechanics [3], thermoelectrics [4] or lab on a chip systems [5], nanotechnology is driving new solutions to boost the detection limits in sensing applications [6]. Nanowires [7][8][9], nanotubes [10][11][12] and nanopillars [13] have become fundamental building blocks to develop biological sensors [14], micro and nanomechanical systems [6,[15][16][17][18] and photonic structures [2]. Various fabrication methods with high resolution potential have been developed to achieve nanoscale structures, based on electron beam lithography [19][20][21], focused ion beam [22] or scanning probe lithography [23][24][25]. ...
Large-area and dense arrays of nanometric scale structures are commonly fabricated for several applications. The characterisation of sub-micron structures (below 1 μm) at a large scale as well as the related data analysis are challenging tasks. Here, we present a method to address the image acquisition, the data extraction and the data analysis, applied to the evaluation of the uniformity of nanometric structures in a silicon master. Automated routines for both high and low magnification Scanning Electron Microscope (SEM) imaging have been successfully developed. SEM images have been automatically acquired by scripting routines, which collect large amounts of images of the nanometric structures covering multiple regions of the wafer in a few hours. Geometric parameters of the nanometric structures such as diameter, period and height have been extracted from the raw images using the developed image processing scripts. Finally, the data extracted from more than 4800 images acquired with three different characterisation scripts (1600 images for each study) have been analysed and plotted according to their position in the wafer.
... This type of fabrication resulted in samples that can be elongated by 3.3% strain at 6.17 GPa yielding fracture stress. 125 A similar nanowire with a diameter ranging between 100 and 200 nm was studied under bending deformation where a 12 GPa average strength 126 and the bending strain range between 1.3% and 12.8% 127 were reported. Besides, a high fatigue resistance and mechanical stability within several hundred loading cycles were observed even at high strain loadings (i.e., 3.5%). ...
Piezoelectric, piezoresistive, and optical fiber sensors have attracted considerable attention in structural health monitoring (SHM) applications for strain/temperature measurements in advanced material structures such as composites. Issues pertaining to the fabrication process and integration of these sensors, however, continue to limit their efficiency in detecting SHM parameters in sensitive applications such as aerospace and medical devices, where accuracy and reliability are prime concerns. This paper provides a critical review of recent developments on sensing materials and their integration methods into composites. For piezoelectric sensors, ferroelectric and piezoelectric characteristics of different material compositions are described and the evolution of ferroelectric properties over a range of temperatures and mechanical loadings is addressed. Fabrication processes and characterization of silicon- and carbon-based piezoresistive materials are presented to assess the electromechanical performance of such sensors. Furthermore, the methods developed for concurrent measurement of strain and temperature using optical fiber sensors are reviewed. The implantation of different sensing mechanisms for detecting physical parameters during and after composite manufacturing processes is described. Since composite delamination due to the embedded sensors is a reoccurring issue, mechanical compatibility of different reported sensors with the base material interface is highlighted. Finally, potential future directions of the reviewed sensing mechanisms are outlined.
... In this thesis we make the distance of the gap to be 50 μm (as shown in Fig. 3.5 (d)). Our simple actuator is thus capable of delivering strain values comparable to state-of-the-art microelectromechanical systems 111 . Moreover, Compared to the commonly used bending method 112,113 , the actuator can be easily operated at cryogenic temperatures [here ~8 K for all measurements in this thesis] in a cold-finger cryostat. ...
The discovery and application of the laws of quantum mechanics has led in the past century to the “first quantum revolution”, characterized by the development of electronic devices and systems of increasing complexity that have profoundly affected our society. There is consensus that we are now approaching the threshold of a second quantum revolution, in which still unexploited resources of quantum mechanics, such as quantum entanglement, will be used to build up quantum computers and secure quantum communication systems. Photons, the quanta of light, shall play a major role in this context, as they are the only realistic quantum information carriers for connecting separate quantum systems and for transmitting quantum information. In addition, degrees of freedom of photons can be used for quantum simulation and computation tasks. Among different systems, semiconductor quantum dots (also dubbed “artificial atoms”) have emerged as one of the most promising quantum-light sources because of their capability of emitting single and entangled photons “on demand” and at high rates. Several issues with these sources have been solved, while other challenges are still open. Arguably, the major one is that the electronic structure and optical spectra of different quantum dots are affected by fluctuations stemming from stochastic processes occurring during quantum dot growth. This limited control leads to a spread in emission wavelength (hindering the use of multiple quantum dots in quantum networks and quantum photonic circuits), the poor coupling to optical modes in predefined photonic circuits, the poor performance as sources of entangled photons, and to inefficiencies due to noise sources in the solid-state environment of a quantum dot. In this thesis, we focus on the use of strain fields induced in the quantum dot after fabrication, as a tool to control specific quantum dot properties, and, conversely, we use the high strain-sensitivity of the quantum dot optical properties to detect local strain fields in mechanical resonators. Firstly, we develop novel micro-machined piezoelectric actuators featuring geometrical strain amplification to continuously tune the emission wavelength of single quantum dots in an unprecedented tuning range of about ~100 meV, corresponding to ~50.000 times the natural emission linewidth, and to reshape the optical selection rules in the studied quantum dots. Together with calculation results, our findings show a promising route to obtain quantum-light sources with ideally oriented dipoles and enhanced oscillator strength for integrated quantum photonics. Then we use the developed actuators to drive mechanical oscillations in suspended membranes. Mechanical resonances are detected by monitoring the light emission from the embedded quantum dots and their frequency tuned by applying continuously variable tensile stress through the same platform. Lastly, the propagation of sound waves in the suspended beams is studied. With quantum dots acting as optical strain sensors, the propagation and attenuation properties of Lamb waves are studied.
... While the maximum strain achievable in PMN-PT is limited to about 0.2% at low temperatures 26 , strain in a layer suspended between the fingers (here a 250-nm-thick (Al)GaAs membrane containing GaAs QDs) is amplified by a factor 2l/d, where l is the length of each finger along the x-axis (here 1.5 mm) and d is the gap width (20-60 μm). Our simple actuator is thus capable of delivering strain values comparable to state-of-the-art microelectromechanical systems 31 and provides a compact alternative to the commonly used bending method [32][33][34] for operation at cryogenic temperatures (here~8 K for all measurements) in a coldfinger cryostat. ...
The optical selection rules in epitaxial quantum dots are strongly influenced by the orientation
of their natural quantization axis, which is usually parallel to the growth direction. This
configuration is well suited for vertically emitting devices, but not for planar photonic circuits
because of the poorly controlled orientation of the transition dipoles in the growth plane.
Here we show that the quantization axis of gallium arsenide dots can be flipped into the
growth plane via moderate in-plane uniaxial stress. By using piezoelectric strain-actuators
featuring strain amplification, we study the evolution of the selection rules and excitonic fine
structure in a regime, in which quantum confinement can be regarded as a perturbation
compared to strain in determining the symmetry-properties of the system. The experimental
and computational results suggest that uniaxial stress may be the right tool to obtain
quantum-light sources with ideally oriented transition dipoles and enhanced oscillator
strengths for integrated quantum photonics.
... These experiments revealed remarkable mechanical properties and modifications of the electronic properties of nanotubes 33,34 as well as of metallic 35,36 and semiconducting nanowires. 19,37,38 Those methods, however, suffer from a limited freedom of choice of the materials used to establish electrical contact with the nanostructure. As a consequence, the effect of strain on the electronic properties of the device is often dominated by Schottky contacts and by the influence that strain has on the barrier height through the piezo-electric effect. ...
We present an automatic measurement platform that enables the characterization of nanodevices by electrical transport and optical spectroscopy as a function of uniaxial stress. We provide insights into and detailed descriptions of the mechanical device, the substrate design and fabrication, and the instrument control software, which is provided under open-source license. The capability of the platform is demonstrated by characterizing the piezo-resistance of an InAs nanowire device using a combination of electrical transport and Raman spectroscopy. The advantages of this measurement platform are highlighted by comparison with state-of-the-art piezo-resistance measurements in InAs nanowires. We envision that the systematic application of this methodology will provide new insights into the physics of nanoscale devices and novel materials for electronics, and thus contribute to the assessment of the potential of strain as a technology booster for nanoscale electronics.
... [41][42][43] Si NWs can also be grown on MEMS through VLS by the selective deposition of seed particles prior to growth. 44,45 The only top-down approach that can address the shortcomings of the aforementioned techniques is based on the fabrication of the Si NW within the device layer of a thin SOI followed by the deposition of a thicker poly-Si layer for MEMS. 22,23 However, the ability of fabricating Si NW and MEMS from the same crystal as proposed in the current work will lead to a very good level of structural integrity in the absence of any mechanical interface. ...
Nanoscale building blocks impart added functionalities to microelectromechanical systems(MEMS). The integration of silicon nanowires with MEMS-based sensors leading to miniaturization with improved sensitivity and higher noise immunity is one example highlighting the advantages of this multiscale approach. The accelerated pace of research in this area gives rise to an urgent need for batch-compatible solutions for scaling to nano. To address this challenge, a monolithic fabrication approach of silicon nanowires with 10-μm-thick silicon-on-insulator (SOI) MEMS is developed in this work. A two-step Si etching approach is adopted, where the first step creates a shallow surface protrusion and the second step releases it in the form of a nanowire. It is during this second deep etching step that MEMS—with at least a 2-order-of-magnitude scale difference—is formed as well. The technique provides a pathway for preserving the lithographic resolution and transforming it into a very high mechanical precision in the assembly of micro- and nanoscales with an extreme topography. Validation of the success of integration is carried out via in situ actuation of MEMS inside an electron microscope loading the nanowire up to its fracture. The technique yields nanowires on the top surface of MEMS, thereby providing ease of access for the purposes of carrying out surface processes such as doping and contact formation as well as in situ observation. As the first study demonstrating such monolithic integration in thick SOI, the work presents a pathway for scaling down to nano for future MEMS combining multiple scales.
... Below we compare results of our calculations of the piezoresistance effect in nanowires oriented along the [111] crystallographic direction with experimental data. There are two unusual (in comparison with bulk crystal) piezoresistance effects in p-type Si nanostructures that are experimentally observed: the giant piezoresistance effect at uniaxial compression [16] and anomalous piezoresistance effect at uniaxial tension [31][32][33]. Origins of both effects we associate with stress induced grow of the hole concentration with strain that is directly linked to value of the dilatation deformation potential a. In work [18] we proposed a model that interpreted the actual experimental characteristics of the giant piezoresistance in silicon nanowires at uniaxial compression. ...
... At high strains sign of the resistivity change had sign opposite to that in bulk material. In this connection the piezoresistance effect at high strains was named as anomalous piezoresistance effect [31][32][33]. In work [33] origin of the anomalous piezoresistance effect was interpreted in terms of stress induced changes in mobility and surface charge modulation. ...
Analytic expressions for low field mobility and conductivity (resistance) in unstrained and high strained states for p-type silicon bulk crystals and nanostructures have been obtained on base of quantum kinetic equation and special form of the non-equilibrium distribution function. Ionized impurities, acoustic and optic phonons are adopted as scattering system. Calculated temperature dependences of mobility and strain dependences of resistance are compared with known experimental data. Numerical value of the dilatation deformation potential has been found. Proposed model of origin of the anomalous piezoresistance effect in p-type silicon nanostructures at high tensile strains provides not only qualitative but even sufficient quantitative agreement with experimental data.
... 74 Similarly, targeted growth of nanowires directly on MEMS tensile testing stages for in situ characterization has been demonstrated. 75 Analogous efforts for 2D materials could yield immense scientific insights, not only for mechanical properties but also in emerging phenomena, such as the piezoelectricity of MoS 2 and other chalcogenides. 76 In Situ Transmission Electron Microscopy under Liquid Environments. ...
Recent major improvements to the transmission electron microscope (TEM) including aberration-corrected electron optics, light-element-sensitive analytical instrumentation, sample environmental control, and high-speed and sensitive direct electron detectors are becoming more widely available. When these advances are combined with in situ TEM tools, such as multimodal testing based on microelectromechanical systems, key measurements and insights on nanoscale material phenomena become possible. In particular, these advances enable metrology that allows for unprecedented correlation to quantum mechanics and the predictions of atomistic models. In this Perspective, we provide a summary of recent in situ TEM research that has leveraged these new TEM capabilities as well as an outlook of the opportunities that exist in the different areas of in situ TEM experimentation. Although these advances have improved the spatial and temporal resolution of TEM, a critical analysis of the various in situ TEM fields reveals that further progress is needed to achieve the full potential of the technology.
