state-of-the-art microscopy resources
The Bio-Imaging Unit is one of a number of facilities available for commercial use at Newcastle University. A full list of University Research Facilities can be found on the Services for Business web pages.
state-of-the-art microscopy resources
The Bio-Imaging Unit is one of a number of facilities available for commercial use at Newcastle University. A full list of University Research Facilities can be found on the Services for Business web pages.
…A new imaging tool was demonstrated for tracking structures in living cells and the bloodstream that will provide information for the use of nanotubes for biomedical and clinical applications.The conventional imaging method uses luminescence, which is limited because it detects the semiconducting nanotubes but not the metallic ones.
The new imaging technique, called transient absorption, uses a pulsing near-infrared laser to deposit energy into the nanotubes, which then are probed by a second near-infrared laser.
The researchers have overcome key obstacles in using the imaging technology, detecting and monitoring the nanotubes in live cells and laboratory mice, as it is done at high speed, it can be seen what’s happening in real time as the nanotubes are circulating in the bloodstream.
One challenge in using the transient absorption imaging system for living cells was to eliminate the interference caused by the background glow of red blood cells, which is brighter than the nanotubes.
The researchers solved this problem by separating the signals from red blood cells and nanotubes in two separate “channels.” Light from the red blood cells is slightly delayed compared to light emitted by the nanotubes. The two types of signals are “phase separated” by restricting them to different channels based on this delay.
Label-free imaging tool tracks nanotubes in cells, Materials Today, http://www.materialstoday.com/view/22516/
Purdue University, http://www.purdue.edu/newsroom/research/2011/
..One of the world’s smallest electronic circuits was engineered by McGill Univ. It is formed by two wires separated by only about 150 atoms or 15 nanometers (nm). This discovery, published in the journal Nature Nanotechnology, could have a significant effect on the speed and power of the ever smaller integrated circuits of the future in everything from smartphones to desktop computers, televisions and GPS systems.
It was found that the effect of one wire on the other can be either positive or negative. This means that a current in one wire can produce a current in the other one that is either in the same or the opposite direction. This discovery, based on the principles of quantum physics, suggests a need to revise our understanding of how even the simplest electronic circuits behave at the nanoscale
McGill Univ. http://www.mcgill.ca/newsroom/
A localization microscopy analysis method that is described
able to extract results in live cells using standard fluorescent
proteins and xenon arc lamp illumination. The Bayesian analysis
of the blinking and bleaching (3B analysis) method models the
entire dataset simultaneously as being generated by a number
of fluorophores that may or may not be emitting light at any
given time. The resulting technique allows many overlapping
fluorophores in each frame and unifies the analysis of the
localization from blinking and bleaching events. By modeling
the entire dataset, we were able to use each reappearance
of a fluorophore to improve the localization accuracy. The
high performance of this technique allowed us to reveal the
nanoscale dynamics of podosome formation and dissociation
throughout an entire cell with a resolution of 50 nm on a 4-s
Cox S et al, Nature Methods,
PUBLISHED ONLINE 4 DECEMBER 2011; DOI:10.1038/NMETH.1812
From investigation of fraud to detective work on more serious crimes such as burglary or murder, Bruker offers a wide range of analytical instruments to help forensic scientists. When you look for Forensic solutions on the Internet, you will find this information and more on the Bruker webpage, “Products and Solutions for Forensic Scientists” (http://www.bruker.com /forensics.html). If you dig a little deeper, you’ll learn that X-ray diffraction (XRD) is used for qualitative and quantitative crystalline phase analysis.
Download… http://www.icdd.com/resources/axa/ vol46/V46_01.pdf …..to learn Kugler’s secrets of sample preparation and to discover eye-opening, real-life examples. It’s as fascinating as CSI. Enjoy reading!
In this paper, differential phase imaging (DPC) with transmitted light is implemented by adding a suitable detection system to a standard commercially available scanning confocal microscope. DPC, a long-established method in scanning optical microscopy, depends on detecting the intensity difference between opposite halves or quadrants of a split photodiode detector placed in an aperture plane. Here, DPC is compared with scanned differential interference contrast (DIC) using a variety of biological specimens and objective lenses of high numerical aperture. While DPC and DIC images are generally similar, DPC seems to have a greater depth of field. DPC has several advantages over DIC. These include low cost (no polarizing or strain-free optics are required), absence of a double scanning spot, electronically variable direction of shading and the ability to image specimens in plastic dishes where birefringence prevents the use of DIC. DPC is also here found to need 20 times less laser power at the specimen than DIC.
Laufer et al, MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK. Amos, Brad: email@example.com
Microfluidics is an evolving scientific field with immense commercial potential: analytical applications, such as biochemical assay development, biochemical analysis and biosensors as well as chemical synthesis applications essentially require microfluidics for sample handling, treatment or readout. A number of techniques are available to create microfluidic structures today. On industrial scale replication techniques such as injection molding are the gold standard whereas academic research mostly focuses on replication by casting of soft elastomers such as polydimethylsiloxane (PDMS). Both of these techniques require the creation of a replication master thus creating the microfluidic structure only in the second process step—they can therefore be termed two-(or multi-)step manufacturing techniques. However, very often the number of pieces to be created of one specific microfluidic design is low, sometimes even as low as one. This raises the question if two-step manufacturing is an appropriate choice, particularly if short concept-to-chip times are required. In this case one-step manufacturing techniques that allow the direct creation of microfluidic structures from digital three-dimensional models are preferable. For these processes the number of parts per design is low (sometimes as low as one), but quick adaptation is possible by simply changing digital data. Suitable techniques include, among others, maskless or mask based stereolithography, fused deposition molding and 3D printing. This work intends to discuss the potential and application examples of such processes with a detailed view on applicable materials. It will also point out the advantages and the disadvantages of the respective technique. Furthermore this paper also includes a discussion about non-conventional manufacturing equipment and community projects that can be used in the production of microfluidic devices.
Rapp et al, Anal. Methods, 2011, 3, 2681-2716
In considering any thoughts you may have of a project topic, please give an outline of your proposal by Please also be aware that we will favour projects where students can engage in a distinct piece of work that leads to a conclusion on your requirements and of significance to the organisation.
On receipt of the proposal outline form, I will contact you to discuss further, and we can reach an agreement and understanding both on your requirements, as well as the School’s academic requirements.
AFM is a key nanoscale measurement insturment that is enabling Nanotechnology developments in all disciplines of science and engineering. As a result, there is a substantial demand by students as well as professionals for AFM Education. The AFMWorkshop and the TT-AFM have considerable advantages for all aspects of AFM education.
The AFMWorkshop offers a TT-AFM assembly workshop Attendees to this this five day workshop receive training on the theory, practice and assembly of an atomic force microscope. It is expected that students of the course have purchased the TT-AFM kit. The courses are held on an as-need basis. After constructing their own AFM Workshop attendees are better able to operate their microscopes. Further, because they know all of the details that went into the microscopes design, they are qualified to make modification and repair it.
On the “Technical” page of the AFMWorkshop web site is a book that is ideal as an introduction to AFM instrumentation, theory, operation and applications. This practical guide is free to the general public and must be downloaded and printed. In addition, “Atomic Force Microscopy” written by Dr.’s Peter Eaton and Paul West, is available from the AFM workshop. This book has all of the information in the free book but includes much more detailed discussions as well as a complete reference list. The book is published by the Oxford University Press.
Assessing Heat Treatment Carburization via the Combustion Method
The new analyzer introduced by Bruker in early 2011 utilizes the combustion method for rapidly and precisely measuring the carbon and sulfur content in metals, soils, and many other sample types. Like many combustion analyzers the G4 ICARUS converts the solid sample of interest into gaseous components which are measured by infrared detectros and processed into tangible carbon and sulfur concentrations. The ICARUS however, has beneficial features using high-frequency HF induction furnace to rapidly combust solid samples – for accurately quantifying the carbon content. In this method the carburized foil is analyzed and quantified with a high frequency induction furnace and infrared detector, respectively. This is a reference method and does not suffer from limitations of previous gravimetric method using weight gain, which is affected by the presence of contaminant species in the furnace atmosphere (eg. oxygen) that will react with the metal surface and artificially increase the foil mass.
Source: October 2011, Bruker Newsletter, Eric S Oxley, Product Manager, Bruker AXS Inc., Billerica, MA, USA
MOSFETs (metal-oxide semiconductor field-effect transistors), the building blocks of today’s digital technology, require supply voltage of around one volt to gradually turn on the transistor. The current transistor technology faces inherent limits to reducing the power demand in electronic circuits due to physical laws related to the MOSFET design. Meanwhile, power demand will increase as the size of next generation transistors decreases and more devices are packed onto a computer chip. In a paper to be delivered at the International Electron Devices Meeting in Washington DC on December 7th, Penn State doctoral candidate Dheeraj Mohata will discuss a new materials and device architecture that provides power savings and instant transistor on-off capability for future electronics. The paper, titled “Demonstration of MOSFET-Like On-Current Performance in Arsenide/Antimonide Tunnel FETs with Staggered Hetero-junctions for 300mV Logic Applications,” reports the fabrication of a heterojunction field effect tunnel transistor with a 650% increase in drive current.
CrystalMaker is an award-winning program for building, displaying, manipulating and animating all kinds of crystal & molecular structures.
CrystalMaker provides a streamlined workflow that majors on productivity: just drag-and-drop your data files into the program for instant display in spectacular photo-realistic colour. Manipulate structures in real time, with the mouse. Multiple View “bookmarks” and undo levels encourage exploration and discovery – ideal for teaching and research.
See the power of automated online sample preparation and multiplexing.
Figure 1 Figure 2
……….While the first commercial AFMs were produced in the late 1980s, the origins of optical microscopy are much less clear, but are thought to lay with simple magnifying glasses in the mid-9th century with further developments in the 16th century. However, it wasn’t until the 17th century that history records scientific observations made with simple and compound microscopes, most notably in the field of biology by Hooke and van Leeuwenhoek (Figure 1). Despite this long history, the most exciting time in optical microscopy has arguably been the past 100 years or so, as diffraction-limited optics, chemically-specific stains, and fluorescent markers and indicators have become widely available. In most modern applications, optical microscopy resolution is on the order of 200-300nm in X and Y, and 500nm in Z.
The AFM (Figure 1above left) uses a microfabricated cantilever made of silicon or silicon nitride with a sharp tip that physically touches the surface of interest. The cantilever raster-scans the sample while its deflection or oscillation amplitude is measured. These measurements are performed with an optical tracking system that uses a segmented photodetector to track the reflection of a laser or superluminescent diode (SLD) off the back of the cantilever (Figure 2, above right ).
Detected changes in cantilever deflection or oscillation are corrected to a setpoint value by actuating the cantilever in Z via a feedback-controlled piezo. These correction voltages sent to the Z piezo are recorded and correlated to a voltage-distance calibration factor in order to determine the height at a given XY coordinate. Because piezos suffer from nonlinearities due to hysteresis, creep, drift, and aging effects, most modern AFMs incorporate sensors that can linearize and correctly measure actual piezo actuation in XYZ. While a variety of sensors are available, the highest performance typically comes from linear variable differential transformers (LVDTs) because of their high linearity and low noise, which result in accurate tip and sample positioning to 0.06-0.6 nanometers. Additionally, the tip and the sample can be mounted on flexure stages that further linearize actuation.
One of the great benefits of AFM is its ability to measure at multiple spatial scales. AFM resolution in XY is limited by the size of the tip, and is typically on the order of a few nanometers, while the upper measurement limit is on the order of 100 microns. Resolution in Z, however, is limited by electronic and thermal noise and is on the order of an Angström, with an upper measurement range that can be several tens of microns. In addition to measuring the physical topography of samples, the AFM cantilever can be used to measure forces such as adhesion, deformation, and sample elasticity by measuring the deflection of the cantilever versus tip-sample separation and applying simple spring mechanical models. With this approach, forces in the picoNewton range can be readily discriminated.
A combined AFM/optical microscope is an excellent instrument for characterizing various samples. Optical microscopy’s chemical specificity and ability to image live processes within the depth of a sample is well complemented by the higher resolution capability of the AFM. For example, a popular technique for identifying internal components in cells utilizes multiple fluorescent markers that bind specifically to molecules of interest. Overlaying the AFM data directly onto the optical data can allow for correlation, while the higher resolution of the AFM can resolve structures that are not composed of the target molecules for fluorescence, or structures that are too small or weakly labeled. Integrating these two technologies is challenging, and different design criteria must be met to ensure success.
Technical Design: Challenges and Solutions
Various technical challenges exist when integrating optical and atomic force microscopes. Optically interfaced AFMs require a robust, custom-made stage to both support the instrument and minimize mechanical noise (Figure 1). Typically, these stages must also be designed so as not to limit the movement or selection of optical microscope objectives, as well as to curtail the risk of mechanical interference between the stage and the optical microscope. Further, the design of the AFM components and stage must accommodate the various piezos, flexures, and sensors discussed above while minimizing the mechanical loop between the tip and the sample, as the susceptibility of the AFM to noise and thermal drift increases with the size of this loop.
Because the AFM uses a laser or SLD to track the position of the cantilever, there must be several considerations in the design of the optical lever in order to minimize interference and crosstalk to the desired optical data. Some of the earliest commercial instruments utilized a red laser diode for optical lever tracking. These diodes were problematic for AFM in general, as they would readily couple optical interference fringes into AFM images and force curves taken on reflective samples. Additionally, the visible red diodes would be seen in images taken on the optical microscope, concomitantly preventing the detection of fluorophores that excite or emit within the wavelength range of the diode. Interference fringes coupled into AFM data were greatly attenuated by the introduction of low-coherence SLDs that emit infrared (IR) wavelengths. Though SLDs greatly reduce AFM data noise and reduce the amount of light emitted at visible wavelengths, the nature of SLDs does result in a faint emission in visible wavelengths that can interfere with highly sensitive optical measurements. Addition of a narrowband filter at the SLD source eliminates this interference, though many commercial AFMs omit such a filter due to the cost or the difficulty of incorporation into the optical lever design. And although many scientific-grade CCD cameras that are used to record images with the optical microscope are sensitive to wavelengths in the IR, addition of a well-designed filter under the microscope objective can block these signals from saturating the camera electronics.
A further design difficulty presents itself with the incorporation of top-down optical access into AFM designs. While several AFM designs do not limit optical access below the sample (resulting in the ability to place the AFM on inverted optical microscopes), certain samples may be opaque or may require mounting on opaque sample holders that prevent the use of the inverted microscope optics. These issues are becoming more prevalent since opaque samples such as polymers, ceramics, and silicon-fabricated devices are garnering more interest across the materials, engineering, and biological sciences. In order to achieve quantitative data collection, high linearity, and low noise performance, the various components of the AFM must be mounted directly above the optical lever, which limits top-down optical access. With this in mind, it would seem that AFM designs would be forced to trade off data quality with optical access.
One common solution to this challenge is to incorporate a large access hole in the AFM head, directly above the optical lever. While this design does allow for optical access directly through the top of the AFM head and the utilization of some of the transmitted light condensers from the optical microscope manufacturers, it also compromises the mechanical design of the AFM head and the accuracy of the optical lever, preventing the collection of truly quantitative force data. In some designs, either ancillary cameras and optics must be added next to the instrument or an entirely different base must be utilized for visualization and documentation of the top-down view for opaque samples. These measures complicate experimental design due to space restrictions in the necessary acoustic isolation equipment or in the difficulty in mechanical reproducibility when moving the AFM to different equipment. Other designs (Figure 1) maintain the various components of the AFM head directly above the tip in order to preserve high-quality quantitative data collection, and incorporate a series of mirrors and high-quality objective lenses to provide top-down optical access through a customized optical microscope condenser (Figure 1C). While more costly, the added advantage of this design is that the objective lens can be used as both a condenser for transmitted light techniques, such as brightfield and optical phase contrast, as well as a viewing element for optical lever alignment and region-of-interest identification on opaque samples without the use of extraneous equipment or separate bases.
Applications of Combined Imaging Modalities
Biological and bioengineered systems are particularly well suited for study with the combined imaging modalities. This comes as no surprise because optical microscopy is a standard technique in biological laboratories, and innovations in the development of labeling techniques and fluorescent markers and indicators have given researchers insights into the structure and function of various biological processes. Since the early 1980s, researchers have learned that the material properties of the physical interface between cells and their environment can play important roles in their structure, function, and development, and that these influences are not directly genomic. This knowledge has become increasingly important, as biologists, engineers, and materials scientists have begun to make breakthroughs in tissue engineering – a key aspect of the emerging field of regenerative medicine. Understanding the structure and patterning of various organelles in these designer cells and tissues is crucial in this field, and a combined AFM/optical instrument can readily show investigators both the 3D topographical structure as well as the composition of various components within that structure. For example, an epifluorescence,2 confocal, and AFM analysis3 of shape-engineered cardiac myocytes showed that the extracellular (outside) boundary conditions of the cell determine the self-assembly pattern of the intracellular cytoskeleton. Confocal data (Figure 4C) showed that cells segregate the nucleus and cytoskeleton in the vertical direction, and that ridges seen on the AFM topography correspond to the contractile machinery when overlaid onto fluorescence data. Further, additional studies by Discher and Engler that exploit the force-measuring ability of the AFM have shown that the development of these structures are also influenced by the mechanical properties of the cell-substrate interface.4
The ability of the AFM to correlate surface topography with internal structural information from fluorescence has also been used to understand mechanisms of membrane fusion in mast cells. Using a combination of topographical mapping and fluorescent staining, Liu and co-workers5 were able to identify optically invisible surface membrane ridges that formed concurrently with optically visible F-actin filaments, a previously uncharacterized mechanism. Additionally, it was discovered that the secretory process in these cells is not mediated by actin filaments, suggesting that the cytoskeleton is a poor target for therapeutic strategies. This is important because mast cell degranulation is a key event in allergic and immunoprotective responses.
Expanding on the ability to correlate topography and biochemical information, a combined AFM/optical system has the added benefit of allowing the investigator to interact with their sample and physically manipulate it. Researchers at UC Berkeley were able to use a carbon nanotube modified AFM tip to penetrate the cell membrane and physically inject molecules of interest without damaging or killing the cell. In this case, transmitted light optical microscopy was used to guide the nano-surgical tool to the area of interest within the cell, while fluorescence microscopy confirmed the internalization, localization, and lifetime of the molecules for several hours after injection into the cell.6 This work offers many new possibilities for direct genetic and proteomic manipulation of individual cells, which has been an important strategy in bioengineering, but has been hampered by the relative destructiveness of traditional micron-scale injection techniques.
Electrical and Optical Characterization of Materials
Advances in AFM beyond topographical imaging and force measurement include the characterization of various sample properties including bias, charge, and current flow. One of the most promising future growth areas for the application of these advanced characterization techniques is in the analysis of organic semiconductors and organic photovoltaic materials.7 Fabrication of both device classes results in nanoscale heterogeneities in composition, morphology, and interfaces, all of which can drastically affect functional efficiency. In these cases, electrically-based AFM techniques can provide nanoscale images while simultaneously measuring various electrical properties correlated to topography. This is important for understanding the effects that morphology has on electrical transport properties, which can then be translated to design and fabrication strategies for these devices.
Ginger and colleagues at the University of Washington have pioneered the application of scanning probe techniques to such organoelectric devices, and their work shows that the combination of these advanced AFM techniques with optical microscopy represents a promising experimental system for their characterization. In one recent study, the investigators measured the nanoscale distribution of light-induced current flow in organic polymer candidates in photovoltaic research.8 The technique, known as photoconductive-AFM (pcAFM), uses the AFM to record both the topography and current flow between the tip and the sample, while simultaneously illuminating the sample through the inverted optical microscope objectives. With this system, photocurrent can be correlated with nanoscale topography, and local current-voltage relationships can be measured at individual points across the surface. Further, because of the flexibility of this dual-microscopy approach, illumination intensities across ~8 orders of magnitude could be applied, and the linearity of the intensity-photocurrent relationship was characterized up to several tens of typical solar intensities.
Conclusion and Future Challenges
This is certainly an exciting time in both the development and application of AFM combined with optical imaging techniques. Though there are several studies that exploit the integration of these two imaging modalities beyond those detailed here, the research community has just begun to realize the many possible applications and problems to which these systems can be applied. The broad applicability of the AFM and advanced SPM characterization techniques to a variety of samples across many fields ensures that the field will continue to grow, especially as new challenges arise in multi-disciplinary environments. Coupled to the innovations in optical microscopy developed across centuries, the challenge of designing AFM instrumentation that can be seamlessly integrated with advanced optical techniques while preserving quantitative data collection is paramount to the future success of the technique. Advances and innovations that make current studies possible demonstrate that we are well on our way to a bright future.
From Wikipedia, the free encyclopedia
Deep Level Transient Spectroscopy (DLTS) is an experimental tool for studying electrically active defects (known as charge carrier traps) in semiconductors. DLTS establishes fundamental defect parameters and measures their concentration in the material. Some of the parameters are considered as defect “finger prints” used for their identifications and analysis.
DLTS investigates defects present in a space charge (depletion) region of a simple electronic device. The most commonly used are Schottky diodes or p-n junctions. In the measurement process the steady-state diode reverse polarization voltage is disturbed by a voltage pulse. This voltage pulse reduces the electric field in the space charge region and allows free carriers from the semiconductor bulk to penetrate this region and recharge the defects causing their non-equilibrium charge state. After the pulse, when the voltage returns to its steady-state value, the defects start to emit trapped carriers due to the thermal emission process. The technique observes the device space charge region capacitance where the defect charge state recovery causes the capacitance transient. The voltage pulse followed by the defect charge state recovery are cycled allowing an application of different signal processing methods for defect recharging process analysis.
The DLTS technique has a higher sensitivity than almost any other semiconductor diagnostic technique. For example, in silicon it can detect impurities and defects at a concentration of one part in 1012 of the material host atoms. This feature together with a technical simplicity of its design made it very popular in research labs and semiconductor material production factories.
In Contact Mode AFM, interatomic van der Waals forces become repulsive as the AFM tip comes in close contact with the sample surface. The force exerted between the tip and the sample in contact mode is on the order of about 0.1-1000nN. Under ambient conditions, two other forces besides van der Waals interactions are also generally present. These forces are the capillary force from a thin layer of water in the atmosphere, as well as the mechanical force from the cantilever itself.
gilent´s patented Magnetic AC Mode (MAC Mode) is a gentle, nondestructive technique for atomic force microscopy that has been designed for imaging extremely delicate samples. MAC Mode allows researchers to image submolecular structures that cannot be resolved with any other AFM technique. It offers the best control available for oscillating probe technology, thereby providing a tremendous benefit for imaging in fluids and imaging soft samples. MAC Mode is particularly useful in areas that require high resolution and force sensitivity especially in a liquid environment, such as biology, polymers, and surface science.
Phase Imaging is a powerful, dynamic force technique that can reveal many unique mechanical and chemical properties of a sample at the nanometer scale. As the vertically oscillating AFM tip encounters regions of different composition, a change in phase, relative to the phase of the drive signal, is measured and recorded. Phase imaging has been found to be particularly useful for mapping the various components of composite materials, studying variations in the composition and contamination in materials, and measuring adhesion, surface hardness, and elasticity. It has been applied to thin film studies, the materials sciences, and composite characterization.
Scanning Tunneling Microscopy (STM) uses a sharp conducting tip and applies a bias voltage between the tip and the sample. When the tip is brought close to the sample, electrons can “tunnel” through the narrow gap either from the sample to the tip or from the tip to the sample, depending on the sign of the bias voltage. This tunneling current changes with tip-to-sample distance, decaying exponentially as distance increases, thus affording remarkably high precision in positioning the tip (sub-angstrom vertically and atomic resolution laterally). For the electron tunneling to take place, both the sample and the tip must be conductive.
Lateral Force Microscopy (LFM) is useful for studying surfaces that have variations in friction. During contact mode AFM scanning, as the probe is dragged over the surface, changes in surface friction and topographic slope can cause the cantilever to twist and thus create forces on the cantilever that are parallel to the plane of the sample surface. Such lateral forces cause lateral deflection of the cantilever, which is sensed by the photodetector and used to form a lateral force image in a manner similar to a normal AFM deflection image.
Electric Force Microscopy (EFM) measures local electrostatic interaction between a conductive tip and a sample through Coulomb forces. Different areas of the surface may have different responses to the charged tip, depending on their local electrical properties. Variation in electrostatic forces can be detected in the change of oscillation amplitude and phase of the AFM probe. EFM can be utilized in many applications, such as characterizing surface electrical properties, detecting defects of an integrated circuit, and measuring the distribution of a particular material on a composite surface.
Magnetic Force Microscopy (MFM) measures magnetic structures/domains of a surface using a magnetic cantilever. As the magnetic tip scans, the interaction between the tip and the surface is greatly affected by the local magnetic properties. The variations in magnetic forces are measured in acoustic AC mode. MFM is a nondestructive technique that can be used to evaluate magnetic materials and devices or to locate and map magnetic defects on a variety of materials and surfaces.
Force Modulation AFM is a fast, very sensitive imaging method that is especially useful for measuring and detecting variations in a surface’s mechanical properties, including stiffness and elasticity. In this technique, a modulated driving signal at a constant frequency is applied to the AFM cantilever while the AFM tip is in contact with the sample. The amplitude variation and phase lag during the scan are measured. Force modulation has proven its utility in life science studies, polymer studies, experiments on semiconductor materials, and the material sciences.
Current Sensing AFM (CSAFM) uses standard AFM contact mode along with ultrasharp AFM cantilevers coated with a conducting film to simultaneously probe conductivity and topography of a sample. By applying a voltage bias between the substrate and a conducting cantilever, a current flow is generated. This current can be used to construct a spatially resolved conductivity image. CSAFM is useful in molecular recognition studies and can be used to spatially resolve electronic and ionic processes across cell membranes.
Kelvin Force Microscopy (KFM) is an atomic force microscopy (AFM) technique in which a conductive AFM tip interacts with the sample according to the sample’s electrostatic characteristics. KFM is an imaging technique that maps the variation of the contact potential between the tip and the sample at each in-plane position. (KFM is also known as surface potential imaging.) Agilent’s MAC Mode III control electronics allows truly-simultaneous recording of topography and KFM images in a single pass, that is, without the time-consuming process of having to scan twice (two-pass scanning), once for topography and once for the electrical image. MAC Mode III enables this by incorporating three independently-controlled lock-in amplifiers, one of which is dedicated to the electrical measurement at the same time that another one is used for topography imaging. This arrangement allows the user to choose the frequencies at which the two lock-in amplifiers operate independently from each other, increasing the operational freedom for electrical experiments. The simultaneous measurement scheme, obviating the need for two-pass scanning, also eliminates the adverse effects on the fidelity of the electrical image that come about due to the drift that the scanner may suffer during the second pass of a two-pass implementation.
Agilent’s unique scanning microwave microscopy (SMM) mode combines the comprehensive electrical measurement capabilities of a performance network analyzer (PNA) with the outstanding spatial resolution of an atomic force microscope. SMM Mode outperforms traditional AFM-based scanning capacitance microscopy techniques, offering far greater application versatility, the ability to acquire quantitative results, and the highest sensitivity and dynamic range in the industry.
The ability to provide calibrated, high-sensitivity, complex electrical and spatial measurements makes SMM Mode particularly useful for semiconductor test and characterization. As well as working on semiconductors, glasses, polymers, ceramics, and metals, SMM Mode lets Agilent 5400 and 5600LS users perform high-sensitivity investigations of ferroelectric, dielectric, and PZT materials. Studies of organic films, membranes, and biological samples can also benefit from SMM Mode. Its very high sensitivity (1.2aF) is ideal for looking at ion channels.
Features and Benefits
The Agilent 5500 AFM/SPM microscope offers numerous unique features, such as patented top-down scanning and unrivalled environmental and temperature control, while providing maximum flexibility and modularity. The universal microscope base permits easy integration with an environmental chamber or an inverted optical microscope. Sample preparation is made easy with our unique sample plates designed for your application including imaging in fluids.
A top-down optical axis through the scanner allows an unobstructed view of the cantilever and the sample without sacrificing sample handling. The scanner’s modular nose cone makes changing imaging modes quick and easy. The Agilent 5500 SPM/AFM is a high performance system that facilitates advanced applications solutions. It offers atomic resolution and is ideal for electrochemistry, polymers, and soft material applications.