Forces acting between an Atomic Force Microscope (AFM) tip and sample are three dimensional. Despite this, most AFM force measurements are confined to one or two dimensions. Extending AFM force measurements into three dimensions has previously required complex, difficult and time-consuming workflows. Here, we demonstrate an accurate, interferometric method for quantifying the full, three-dimensional response of an AFM tip to localized forces. We demonstrate this approach on a series of piezoelectric materials and show that this approach yields quantitative 3D measurement independent of the sample orientation beneath the tip. This approach simplifies existing, angle-resolved piezoresponse force microscopy (PFM) techniques. Our measurements benefit from the greatly reduced noise floor (5 fm per root Hz) and intrinsic accuracy of our interferometric measurements. One important result is that the vertical piezo sensitivity was systematically 2 to 3 times larger than the in-plane piezo sensitivities. A simple analysis of vertical and lateral contact stiffnesses, due to the difference in the Young (vertical) and Shear (lateral) sample yields a factor of 2.5, in good agreement with the measurements. While this work was confined to ferroelectric materials, it provides a general workflow and framework for other AFM based mechanical measurements.
The electrical generation and detection of elastic waves are the foundation for acousto-electronic and acousto-optic systems. For surface-acoustic-wave devices, micro-/nano-electromechanical systems, and phononic crystals, tailoring the spatial variation of material properties such as piezoelectric and elastic tensors may bring significant improvements to the system performance. Due to the much smaller speed of sound than speed of light in solids, it is desirable to study various electroacoustic behaviors at the mesoscopic length scale. In this work, we demonstrate the interferometric imaging …
We study nanoelectromechanical resonators fabricated from suspended flakes of NbSe$_2$ (thickness$\sim$30-50 nm) to probe charge density wave (CDW) physics at nanoscale. Variation of elastic and electronic properties accompanying the CDW phase transition (around 30 K) are investigated simultaneously using the devices as self-sensing heterodyne mixers. Elastic modulus is observed to change by 10 per cent, an amount significantly larger than what had been reported earlier in the case of bulk crystals. We also study the modulation of conductance by electric field effect, and examine its relation …
Ever increasing hardware capabilities and computation powers have made acquisition and analysis of big scientific data at the nanoscale routine, though much of the data acquired often turns out to be redundant, noisy, and/or irrelevant to the problems of interests, and it remains nontrivial to draw clear mechanistic insights from pure data analytics. In this work, we use scanning probe microscopy (SPM) as an example to demonstrate deep data methodology, transitioning from brute force analytics such as data mining, correlation analysis, and unsupervised classification to informed and/or targete…
Precise manipulation of electronic band structures of two-dimensional (2D) transition metal dichalcogenides and oxides (TMD&Os) via localised strain engineering is an exciting avenue for exploiting their unique characteristics for electronics, optoelectronics, and nanoelectromechanical systems (NEMS) applications. This work experimentally demonstrates that mechanically-induced electrical transitions can be engineered in quasi-2D molybdenum disulphide (MoS2) and molybdenum trioxide (MoO3) using an in situ electrical nanoindentation technique. It is shown that localised strains on such quasi-2D …
The ability to probe a materials electromechanical functionality on the nanoscale is critical to applications from energy storage and computing to biology and medicine. Voltage modulated atomic force microscopy (VM-AFM) has become a mainstay characterization tool for investigating these materials due to its unprecedented ability to locally probe electromechanically responsive materials with spatial resolution from microns to nanometers. However, with the wide popularity of VM-AFM techniques such as piezoresponse force microscopy (PFM) and electrochemical strain microscopy (ESM) there has been …
Nanowires have been considered for a number of applications in nanometrology. In such a context, we have explored the possibility of using ultrathin twisted nanowires as torsion nanobalances to probe forces and torques at molecular level with high precision, a nanoscale system analogous to the Coulomb's torsion balance electrometer. In order to achieve this goal, we performed a first principles investigation on the structural and electronic properties of twisted silicon nanowires, in their pristine and hydrogenated forms. The results indicated that wires with pentagonal and hexagonal cross sec…
Piezoelectric nanowires are promising materials for sensing, actuation and energy harvesting, due to their enhanced properties at the nanoscale. However, quantitative characterization of piezoelectricity in nanomaterials is challenging due to practical limitations and the onset of additional electromechanical phenomena, such as the triboelectric and piezotronic effects. Here, we present an open-circuit conductive atomic force microscopy (cAFM) methodology for quantitative extraction of the axial piezoelectric coefficients of nanowires. We show, both theoretically and experimentally, that the s…
Ferroelectric materials have remained one of the foci of condensed matter physics and materials science for over 50 years. In the last 20 years, the development of voltage-modulated scanning probe microscopy techniques, exemplified by Piezoresponse force microscopy (PFM) and associated time and voltage spectroscopies, opened a pathway to explore these materials on a single-digit nanometer level. Consequently, domain structures, walls and polarization dynamics can now be imaged in real space. More generally, PFM has allowed studying electromechanical coupling in a broad variety of materials ran…
A universal challenge facing the development of electrochemical materials is our lack of understanding of physical and chemical processes at local length scales in 10-100 nm regime, and acquiring this understanding requires a new generation of imaging techniques. In this article, we introduce the scanning thermo-ionic microscopy (STIM) for probing local electrochemistry at the nanoscale, using for imaging the Vegard strain induced via thermal stress excitations. Since ionic oscillation is driven by the stress instead of voltage, the responses are insensitive to the electromechanical, electrost…
We present a micro-electromechanical system (MEMS) based method for the resist free patterning of nano-structures. Using a focused ion beam (FIB) to customize larger MEMS machines, we fabricate apertures as small as 50 nm on plates that can be moved with nanometer precision over an area greater than 20x20 μm^2. Depositing thermally evaporated gold atoms though the apertures while moving the plate results in the deposition of nanoscale metal patterns. Adding a shutter only microns above the aperture, enables high speed control of not only where but also when atoms are deposited. Using a shutter…
Electric charge detection by atomic force microscopy (AFM) with single- electron resolution (e-EFM) is a promising way to investigate the electronic level structure of individual quantum dots (QD). The oscillating AFM tip modulates the energy of the QDs, causing single electrons to tunnel between QDs and an electrode. The resulting oscillating electrostatic force changes the resonant frequency and damping of the AFM cantilever, enabling electrometry with a single-electron sensitivity. Quantitative electronic level spectroscopy is possible by sweeping the bias voltage. Charge stability diagram …
We show that torsion resonators can experience massive dissipation dilution due to nanoscale strain, and draw a connection to a century-old theory from the torsion balance community which suggests that a simple torsion ribbon is naturally soft-clamped. By disrupting a commonly held belief in the nanomechanics community, our findings invite a rethinking of strategies towards quantum experiments and precision measurement with nanomechanical resonators. For example, we revisit the optical lever technique for monitoring displacement, and find that the rotation of a strained nanobeam can be resolve…
The presence of electrostatic forces and associated artifacts complicates the interpretation of piezoresponse force microscopy (PFM) and electrochemical strain microscopy (ESM). Eliminating these artifacts provides an opportunity for precisely mapping domain wall structures and dynamics, accurately quantifying local piezoelectric coupling coefficients, and reliably investigating hysteretic processes at the single nanometer scale to determine properties and mechanisms which underly important applications including computing, batteries and biology. Here we exploit the existence of an electrostat…
Direct imaging elucidates ionic memory in two-dimensional nanochannels
The University of Manchester（曼彻斯特大学）；National Graphene Institute, The University of Manchester（曼彻斯特大学国家石墨烯研究所）；EPFL（洛桑联邦理工学院）；Institute of Bioengineering, School of Engineering, EPFL（洛桑联邦理工学院工程学院生物工程系）；Institute of Science and Technology Austria (ISTA)（奥地利科学与技术研究院）；ENS de Lyon, Université de Lyon（里昂高等师范学院，里昂大学）；Laboratoire Photonique Numérique et Nanosciences, Univ. Bordeaux（波尔多大学光子数字与纳米科学实验室）
