Utilization of a Two-Beam Cantilever Array for Enhanced Atomic Force Microscopy Sensitivity

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Samuel Jackson ◽  
Stefanie Gutschmidt
Keyword(s):  
Atomic Force Microscopy ◽  
Degrees Of Freedom ◽  
Sample Surface ◽  
Feedback Signal ◽  
Single Beam ◽  
Force Microscopy ◽  
Beam Array ◽  
Atomic Force ◽  
Alternative Approach ◽  
Cantilever Array

An array of cantilevers offers an alternative approach to standard single beam measurement in the context of atomic force microscopy (AFM). In comparison to a single beam, a multi-degrees-of-freedom system offers a greater level of flexibility with regard to parameter selection and tuning. By utilizing changes in the system eigenmodes as a feedback signal, it is possible to enhance the sensitivity of AFM to changes in sample topography above what is achievable with standard single beam techniques. In this paper, we analyze a two-beam array operated in FM-AFM mode. The array consists of a single active cantilever that is excited with a 90 deg phase-shifted signal and interacts with the sample surface. The active beam is mechanically coupled to a passive beam, which acts to vary the response between synchronized and unsynchronized behavior. We use a recently developed mathematical model of the coupled cantilever array subjected to nonlinear tip forces to simulate the response of the described system with different levels of coupling. We show that the sensitivity of the frequency feedback signal can be increased significantly in comparison to the frequency feedback from a single beam. This is a novel application for an AFM array that is not present in the literature.

Nonlinear Dynamics and Control of the Scan Process in Atomic Force Microscopy

2007 ◽  
Author(s):  
S. Hornstein ◽  
O. Gottlieb
Keyword(s):  
Atomic Force Microscopy ◽  
Degrees Of Freedom ◽  
Smooth Transition ◽  
Digital Controller ◽  
Force Microscopy ◽  
Imaging Tool ◽  
Atomic Force ◽  
Scan Speed ◽  
Dynamics And Control ◽  
Spatio Temporal

Atomic Force Microscopy (AFM) is a major imaging tool used to map surfaces down to atomic resolution. However, scanning rates in AFM are still low, and attempts to increase the speed usually end up with low-resolution pictures. In order to address this deficiency we propose a novel model that treats the scanning element as a moving continuous microcantilever, which undergoes a combined spatial motion in both the horizontal and the vertical directions. This research investigates the effect of increasing the scan speed on the dynamics and stability of a vibrating microcantilever that is governed by a specified control law. We reduce the spatio-temporal model to a rigid body two-degrees-of-freedom system, which is connected to a linear digital controller. Results demonstrate that the digital controller stabilizes the nonlinear system and enables a smooth transition from one side to the other side of the sample, needed for the scanning process.

Sufficient condition for reliability measurement of sample geometry by atomic force microscopy

2020 ◽  
pp. 11-15
Author(s):  
Alexander S. Kravchuk ◽  
Anzhelika I. Kravchuk
Keyword(s):  
Atomic Force Microscopy ◽  
Preliminary Investigation ◽  
Sample Surface ◽  
Sufficient Condition ◽  
Surface Geometry ◽  
Force Microscopy ◽  
Atomic Force ◽  
Geometric Deviations ◽  
Reliability Measurement ◽  
Microscope Stage

A sufficient condition for determining the reliability of geometry measurements using atomic force microscopy for relatively small cantilever tilt angles is proposed. A relationship between the basic geometric parameters of surface roughness, geometric deviations of the probe, the angles of the cantilever and the inclination of the side faces of the probe, as well as the dimensions of the nonlocal point of the probable contact of its side faces with protrusions of roughness has been established. As a sufficient condition for the reliability of geometry measurements using atomic force microscopy, an obvious requirement is accepted. It determines the smallness of the ratio of the sizes of a nonlocal point to the distance between neighboring nonlocal points. Publications in which the measurement of surface nano-geometry of the samples does not indicate the roughness of the sample surface and the probe, the angles at the tip of the probe and the tilt of the cantilever, as well as the best resolution (smallest step) at which the study is carried out, cannot be accepted as reliable, because the results obtained in them are probabilistic in nature. The surface images obtained using atomic force microscopy without proper justification for the resolution (value of the measurement step) represent only a qualitative picture, on the basis of which it makes no sense to carry out any computational manipulations. In order to increase the reliability of measurements of surface geometry using atomic force microscopy, it is necessary to radically increase the accuracy of the manufacture of probes, as well as use probes with the smallest possible angle at the apex. In addition, it is necessary to make changes in the design of the atomic force microscopy. In particular, the automatic rotation of the microscope stage should be designed. It should provide closeness the probe axis direction to the normal to the average plane of the sample. This “integral” angle of rotation of the microscope stage is easily iteratively determined at the stage of preliminary investigation of the geometry of the surface of the sample. In this case, it will be necessary to geometrically increase the length of the cantilever so that the base extends beyond the limits of the sample.

Features of the Manufacturing Process of Silicon Tips for Cantilevers

2021 ◽  
Vol 26 (3-4) ◽  
pp. 234-245
Author(s):  
A.V. Novak ◽  
◽  
V.R. Novak ◽  
A.V. Rumyantsev ◽  
◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Silicon Film ◽  
Statistical Parameter ◽  
Sample Surface ◽  
Test Sample ◽  
Oxygen Atmosphere ◽  
Maximum Height ◽  
Force Microscopy ◽  
Atomic Force ◽  
Crystallographic Planes

Sample surface examination in atomic force microscopy is carried out using cantilevers having the form of elastic consoles with sharp needle (tip) at the free end. Quality of images obtained from atomic force microscope (AFM) heavily depends on tip sharpness degree. Silicon cantilevers made based on wet anisotropic etching are widely used in atomic force microscopy. This paper studies the dependence of the shape and size of the resulting tip on the concentration of KOH in the solution, as well as the effect of pyrogenic oxidation and oxidation in a dry oxygen atmosphere on the sharpness of the tip during the sharpening process. It was shown that when 70 % concentration is used, tips with the highest aspect ratio and maximum height are obtained. In this case, the shape of the needle is an octagonal pyramid, the lateral faces of which are formed by eight crystallographic planes from {311} and {131}. It was found that in a two-stage sharpening process, consisting of pyrogenic oxidation and oxidation in a dry oxygen atmosphere, it is possible to form sufficiently sharp probes with a tip radius of 2–5 nm and an apex angle of 14–24°. It has been established that a one-stage sharpening process based on pyrogenic oxidation provides only the production of probes with a radius of about 14 nm. Comparative tests of the manufactured probes in obtaining AFM images of a test sample of a polycrystalline silicon film with hemispherical grains (HSG-Si) were presented. Research study has revealed that such a statistical parameter as the relative increment of the surface area Sdr is the most sensitive to probe sharpness for surfaces of the HSG-Si film type.

Investigation of Epitaxial GaN Films by Conductive Atomic Force Microscopy

2003 ◽  
Vol 764 ◽  
Author(s):  
S. Dogan ◽  
J. Spradlin ◽  
J. Xie ◽  
A. A. Pomarico ◽  
R. Cingolani ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Sample Surface ◽  
Conductive Atomic Force Microscopy ◽  
Force Microscopy ◽  
Topological Features ◽  
Atomic Force ◽  
Local Current ◽  
Semiconductor Junction ◽  
Surrounding Areas ◽  
Conduction Properties

AbstractThe current conduction in GaN is very topical and is the topic of a vast amount of research. By simultaneously mapping the topography and the current distribution, conductive atomic force microscopy (C-AFM) has the potential to establish a correlation between topological features and localized current paths. In this study, this technique was applied to image the conduction properties of as-grown and post-growth chemically etched samples GaN epitaxial layers on a microscopic scale. Our results show that prismatic planes have a significantly higher conductivity than the surrounding areas of the sample surface. A large and stable local current was mainly observed from the walls of the etched pits, under forward and reverse bias of the metallized AFM tip/semiconductor junction.

scholarly journals A Non-Destructive, Tuneable Method to Isolate Live Cells for High-Speed AFM Analysis

2021 ◽  
Vol 9 (4) ◽  
pp. 680
Author(s):  
Christopher T. Evans ◽  
Sara J. Baldock ◽  
John G. Hardy ◽  
Oliver Payton ◽  
Loren Picco ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
High Resolution ◽  
High Speed ◽  
Single Cells ◽  
Sample Surface ◽  
Live Cells ◽  
Contact Mode ◽  
Force Microscopy ◽  
Atomic Force ◽  
Afm Analysis

Suitable immobilisation of microorganisms and single cells is key for high-resolution topographical imaging and study of mechanical properties with atomic force microscopy (AFM) under physiologically relevant conditions. Sample preparation techniques must be able to withstand the forces exerted by the Z range-limited cantilever tip, and not negatively affect the sample surface for data acquisition. Here, we describe an inherently flexible methodology, utilising the high-resolution three-dimensional based printing technique of multiphoton polymerisation to rapidly generate bespoke arrays for cellular AFM analysis. As an example, we present data collected from live Emiliania huxleyi cells, unicellular microalgae, imaged by contact mode High-Speed Atomic Force Microscopy (HS-AFM), including one cell that was imaged continuously for over 90 min.

Identification and Analysis of Artifacts in Amplitude Modulated Atomic Force Microscopy Array Operation

2017 ◽  
Vol 12 (5) ◽  
Author(s):  
Samuel Jackson ◽  
Stefanie Gutschmidt
Keyword(s):  
Atomic Force Microscopy ◽  
Separation Distance ◽  
Constant Frequency ◽  
Single Beam ◽  
Force Microscopy ◽  
Atomic Force ◽  
Close Proximity ◽  
Output Amplitude ◽  
Sample Separation ◽  
The Relationship

To increase measurement throughput of atomic force microscopy (AFM), multiple cantilevers can be placed in close proximity to form an array for parallel throughput. In this paper, we have measured the relationship between amplitude and tip-sample separation distance for an array of AFM cantilevers on a shared base actuated at a constant frequency and amplitude. The data show that discontinuous jumps in output amplitude occur within the response of individual beams. This is a phenomenon that does not occur for a standard, single beam system. To gain a better understanding of the coupled array response, a macroscale experiment and mathematical model are used to determine how parameter space alters the measured amplitude. The results demonstrate that a cusp catastrophe bifurcation occurs due to changes in individual beam resonant frequency, as well as significant zero-frequency coupling at the point of jump-to-contact. Both of these phenomena are shown to account for the amplitude jumps observed in the AFM array.

scholarly journals Effect of Eigenmode Frequency on Loss Tangent Atomic Force Microscopy Measurements

2021 ◽  
Vol 11 (15) ◽  
pp. 6813
Author(s):  
Babak Eslami ◽  
Dylan Caputo
Keyword(s):  
Atomic Force Microscopy ◽  
Loss Tangent ◽  
Oscillation Amplitude ◽  
Excitation Frequency ◽  
Chemical Properties ◽  
Sample Surface ◽  
Force Microscopy ◽  
Atomic Force ◽  
Afm Cantilever ◽  
Tip Radius

Atomic Force Microscopy (AFM) is no longer used as a nanotechnology tool responsible for topography imaging. However, it is widely used in different fields to measure various types of material properties, such as mechanical, electrical, magnetic, or chemical properties. One of the recently developed characterization techniques is known as loss tangent. In loss tangent AFM, the AFM cantilever is excited, similar to amplitude modulation AFM (also known as tapping mode); however, the observable aspects are used to extract dissipative and conservative energies per cycle of oscillation. The ratio of dissipation to stored energy is defined as tanδ. This value can provide useful information about the sample under study, such as how viscoelastic or elastic the material is. One of the main advantages of the technique is the fact that it can be carried out by any AFM equipped with basic dynamic AFM characterization. However, this technique lacks some important experimental guidelines. Although there have been many studies in the past years on the effect of oscillation amplitude, tip radius, or environmental factors during the loss tangent measurements, there is still a need to investigate the effect of excitation frequency during measurements. In this paper, we studied four different sets of samples, performing loss tangent measurements with both first and second eigenmode frequencies. It is found that performing these measurements with higher eigenmode is advantageous, minimizing the tip penetration through the surface and therefore minimizing the error in loss tangent measurements due to humidity or artificial dissipations that are not dependent on the actual sample surface.

scholarly journals ATOMIC FORCE MICROSCOPY AS A TOOL FOR TESTING BIOMEDICAL SAMPLES AND ELIMINATION PROBE ARTIFACTS

2019 ◽  
Vol 10 (2) ◽  
Author(s):  
Ljubiša Petrov ◽  
Lidija Matija
Keyword(s):  
Atomic Force Microscopy ◽  
Numerical Data ◽  
Sample Surface ◽  
Pharmaceutical Products ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
The Real ◽  
Force Microscopy ◽  
Atomic Force ◽  
Reconstructed Surface

One of the most perspective available techniques for investigation of the composition, structure and properties of materials, is scanning probe microscopy (SPM), respectively its components scanning tunneling microscopy (STM) and atomic force microscopy (AFM). This technique is used in multidisciplinary research in the field of medicine, pharmacy, dentistry, material science, etc., for study of biological samples, chemical compounds, pharmaceutical products, artificial tissues, implantology materials, and all other materials that have nanotechnological impact on application in these scientific fields. This is because the probes have not perfect size and geometry, which leads to the appearance of artifacts. They are defined as characteristics that appear on the image and are not present on the sample. These effects caused by convolutions between the probe and sample can be corrected to a certain extent by mathematical manipulation of topographic data. The methodology used in this paper is based on algebra of sets, and basic tools of mathematical morphology. Mathematical algorithms for the „blind reconstruction“ of the tip were used, and then in order to detect the parts of the sample surface which is not available in real-time scanning deconvolution was applied. The limit of the real probe tip is calculated from the image, using the morphological limitations inherent in the recording process. The result acuired as an image of the reconstructed surface out of the used images, with the reconstruction of the real tip. The presented results are clear proof of the usability of atomic force microscopy as a technique for imaging of biological materials on nano-level, and the applied algorithms increase the usability of the images in terms of a better conclusion based on precise numerical data taken from the processed images.

scholarly journals High-bandwidth multimode self-sensing in bimodal atomic force microscopy

2016 ◽  
Vol 7 ◽  
pp. 284-295 ◽  
Author(s):  
Michael G Ruppert ◽  
S O Reza Moheimani
Keyword(s):  
Atomic Force Microscopy ◽  
Piezoelectric Layer ◽  
Signal To Noise Ratio ◽  
Beam Deflection ◽  
Feedback Signal ◽  
Phase Imaging ◽  
Cantilever Deflection ◽  
Force Microscopy ◽  
Atomic Force ◽  
A Charge

Using standard microelectromechanical system (MEMS) processes to coat a microcantilever with a piezoelectric layer results in a versatile transducer with inherent self-sensing capabilities. For applications in multifrequency atomic force microscopy (MF-AFM), we illustrate that a single piezoelectric layer can be simultaneously used for multimode excitation and detection of the cantilever deflection. This is achieved by a charge sensor with a bandwidth of 10 MHz and dual feedthrough cancellation to recover the resonant modes that are heavily buried in feedthrough originating from the piezoelectric capacitance. The setup enables the omission of the commonly used piezoelectric stack actuator and optical beam deflection sensor, alleviating limitations due to distorted frequency responses and instrumentation cost, respectively. The proposed method benefits from a more than two orders of magnitude increase in deflection to strain sensitivity on the fifth eigenmode leading to a remarkable signal-to-noise ratio. Experimental results using bimodal AFM imaging on a two component polymer sample validate that the self-sensing scheme can therefore be used to provide both the feedback signal, for topography imaging on the fundamental mode, and phase imaging on the higher eigenmode.

Atomic force microscopy cantilever simulation by finite element methods for quantitative atomic force acoustic microscopy measurements

2006 ◽  
Vol 21 (12) ◽  
pp. 3072-3079 ◽  
Author(s):  
F.J. Espinoza Beltrán ◽  
J. Muñoz-Saldaña ◽  
D. Torres-Torres ◽  
R. Torres-Martínez ◽  
G.A. Schneider
Keyword(s):  
Atomic Force Microscopy ◽  
Finite Element ◽  
Elastic Modulus ◽  
Finite Element Methods ◽  
Sample Surface ◽  
Acoustic Microscopy ◽  
Force Microscopy ◽  
Atomic Force ◽  
Resonance Frequencies ◽  
Wide Range

Measurements of vibrational spectra of atomic force microscopy (AFM) microprobes in contact with a sample allow a good correlation between resonance frequencies shifts and the effective elastic modulus of the tip-sample system. In this work we use finite element methods for modeling the AFM microprobe vibration considering actual features of the cantilever geometry. This allowed us to predict the behavior of the cantilevers in contact with any sample for a wide range of effective tip-sample stiffness. Experimental spectra for glass and chromium were well reproduced for the numerical model, and stiffness values were obtained. We present a method to correlate the experimental resonance spectrum to the effective stiffness using realistic geometry of the cantilever to numerically model the vibration of the cantilever in contact with a sample surface. Thus, supported in a reliable finite element method (FEM) model, atomic force acoustic microscopy can be a quantitative technique for elastic-modulus measurements. Considering the possibility of tip-apex wear during atomic force acoustic microscopy measurements, it is necessary to perform a calibration procedure to obtain the tip-sample contact areas before and after each measurement.

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