Metrology & Instrumentation : AFM / SPM

When measuring at these small scales, ground vibration and/or acoustic noise can be significant and can affect measurements substantially. To combat this, Veeco offers two products, the VT-103-3K Acoustic/Vibration Isolation System and the VT-102 Vibration Isolation Table.

The Atmospheric Hood can be used with the MultiMode SPM to conduct experiments under controlled atmospheres. Common applications include imaging under controlled humidity and under inert gases. The hood comes in several configurations to support the E, J, EV, and JV MultiMode scanners with or without the low-temperature MultiMode heating accessory. The hood also support either the standard MultiMode head or the applications-module ready MultiMode head. Multiple ports are provided through which wires and tubing can be routed. This makes the MultiMode with the Atmospheric Hood a very versatile instrument for experiments requiring precise environmental control.

Electrochemistry STM/AFM/SECPM combines SPM with electrochemical control to study surface structure, properties, and reactivity of the electrode surface at the electrochemical interface. Studies may be conducted in situ, imaging surfaces in an electrochemical solution with or without potential control of an integrated potentiostat/galvanostat, or ex situ, imaging surfaces before and after the electrode is exposed to the electrolyte solution.

Click here for datasheet [pdf]

Electrochemistry STM/AFM/SECPM combines SPM with electrochemical control to study surface structure, properties, and reactivity of the electrode surface at the electrochemical interface. Studies may be conducted in situ, imaging surfaces in an electrochemical solution with or without potential control of an integrated potentiostat/galvanostat, or ex situ, imaging surfaces before and after the electrode is exposed to the electrolyte solution.

Click here for datasheet [pdf] 

There are many applications modules for the Dimension line: TUNA, CAFM, SCM and SSRM. These modules can map nanoscale resolution on a wide variety of materials including low-and mid-strength electrical currents, resistance and capacitance.

Fluid Imaging Cells provide contact mode and TappingMode AFM imaging in fluid environments. Fluid cells consist of a glass cantilever holder and silicon o-ring to form an enclosed fluid environment with the ability to exchange liquids. TappingMode can be conducted by oscillating the cantilever acoustically (traditional) or by Magnetic Actuated Drive. For electrochemical experiments, fluid cells allow contact mode and TappingMode imaging in electrochemical solutions with the addition of the electrochemical STM/AFM converters.

Click here for datasheet [pdf]

The Magnetic Actuated Drive for the Multimode AFM is specifically designed for TappingMode in fluids. The option offers easy set-up and operation including automatic cantilever tuning. Option includes the magnetic drive electronics, fluid cell, and interface cable as well as a starter set of probes.

Click here for datasheet [pdf] 

The MultiMode Closed-Loop Scanner brings the accuracy and precision of closed-loop control to the MultiMode V. You no longer need to choose between a SPM offering ultra-high resolution imaging and one offering the accuracy and convenience of closed-loop.

Using the MultiMode Closed-Loop Scanner's large 100 micron XY range and 15 micron Z range it is easy to find and image the exact regions of interest on your samples with excellent accuracy. It can also precisely target locations on the sample for "point-and-shoot" force measurements. With optional NanoMan software it is possible to perform precise nanolithography and nanomanipulation. In addition to these features, you will enjoy the same ease of use, reliability, and support that has made Veeco the performance leader in SPM technology.

Click here for datasheet [pdf]

New liquid resistant MultiMode scanners are now available, based on the previous "EV" and "JV" designs. They still have the same great performance and low-noise vertical engage design, but now also include a four year warranty against damage caused by fluid during normal use. Though intended for fluid imaging work, they perform equally well for imaging in air. They are compatible with all MultiMode and NanoScope controller versions

NanoScope® Software offers unprecedented data control while delivering the greatest possible ease of use. Version 6 and higher software packages contain application routines designed specifically for force spectroscopy. Other features include

• Automatic cantilever spring constant calibration
• User-defined "scripting" for flexible design of experiments
• Powerful off-line export and processing tools, including batch processing

Veeco's new MultiMode heater/cooler line brings innovation and increased thermal control convenience to life sciences and polymers research. A single controller now controls sample temperatures from -35°C to 250°C. Four models are available that allow researchers to purchase a thermal solution tailored to their needs. Three temperature ranges are available for air and inert gasses; -35° to 100°C, ambient to 250°C, and -35° to 250°C. A fourth model operates in fluids or air from ambient to 60°C using standard MultiMode scanners. Other features include an improved high-volume pump for better stabilization of scanner temperature during heating and cooling, and a new and improved liquid-cooled scanner that operates with two different heating/cooling elements and includes temperature sensing to protect the scanner from damage.

Optical Microscope provides vertical optical view of tip and sample surface with optical microscope, color CCD camera, and color monitor -  magnification is about 450X on a 15 inch monitor.

Phaseimaging is a powerful extension of TappingMode. It is a key element in the use of a number of scanning probe techniques, including Phase Imaging, MFM, EFM, Surface Potential, SCM, SSRM, TUNA, and C-AFM, as well as other techniques. The Quadrex offers a method of detection that provides an improved noise floor and more sensitive measurement than other detection methods, such as amplitude detection. It also provides lock-in detection with advanced signal routing and access to signals for enhanced imaging measurement.

The Signal Access Modules SAM™ are in-line hardware accessories that allow access or interruption of signals between Dimension™, EnviroScope™, BioScope™, or MultiMode™ scanning probe microscopes (SPMs) and their NanoScope® controllers. Signals can be injected, tapped, and modified as they  flow between the SPM and the controller. Signal access is very useful for advanced  experimentation and diagnostic evaluation because it gives researchers the open architecture they need to conduct innovative experiments.

• SAM III: Works with the MultiMode, PicoForce, and EnviroScope and all SPMs using NanoScope Controllers prior to the NanoScope V. Since the signals between the controller and the SPM are already ground referenced, this
  is a passive device.
• SAM V: Works with the Dimension and Bioscope SPMs using NanoScope V controllers. The SAM V contains active electronics to convert the differential signals between these SPMs and the NanoScope V to ground referenced signals.

Click here for datasheet [pdf]

STM & Low-Current STM Converters provides STM capability for the MultiMode SPM with a TipView STM head. This mechanical design achieves very high quality atomic resolution STM scans with the appropriate scanner. The Low-Current STM Converter allows the scanning of poorly conductive samples with pA-scale tunneling currents.

Tip Evaluation helps users quickly identify tip problems which can degrade images and measurements which could lead to faulty interpretation of data. The Tip Evaluation feature compares user-selected thresholds with calculated tip characteristics obtained directly from the AFM image. This capability provides better and more consistent results, better comparison of data collected with different tips.

VITA (Veeco Instruments Thermal Analysis) technology adds high resolution thermal characterization capabilities to existing Veeco Scanning Probe Microscopes (SPM).

Now SPM users not only benefit from unmatched core performance, but can add a
traditional bulk characterization technique. The VITA option builds on Veeco’s extensive expertise with thermal measurements — providing extended thermal measurement
performance through:

• Improved lateral resolution capabilities (to <100 nm)
• Full digital control of heating cycles
• Productive VITA control integration enabled by Veeco systems open architecture

VITA technology provides superior material characterization in two ways:

• Nanoscale Thermal Analysis
• Scanning Thermal Microscopy

Veeco Instruments Thermal Analysis Webinar

Presenter: Thomas Mueller

Duration approx. 52 minutes

File size 48 MB

View it Now!

Install the GotoMeeting Codec to play the webinar video

VITA - Veeco Instruments Thermal Analysis Application Note

• High Res [1.1 MB pdf ]

• VITA Scanning Thermal Analysis
  
  Low Res [262 KB pdf ]

Conductive Atomic Force Microscopy (CAFM) is a secondary imaging mode derived from contact AFM that characterizes conductivity variations across medium- to low-conducting and semiconducting materials. CAFM performs general-purpose measurements, and has a current range of 2 pA to 1 µA. CAFM employs a conductive probe tip. Typically, a DC bias is applied to the tip, and the sample is held at ground potential. While the z feedback signal is used to generate a normal contact AFM topography image, the current passing between the tip and sample is measured to generate the conductive AFM image.



Current flow in conductive AFM (CAFM).

In contact AFM, the tip is in perpetual contact with the sample. The tip is attached to the end of a cantilever with a low spring constant, lower than the effective spring constant holding the atoms of most solid samples together. As the scanner gently traces the tip across the sample (or the sample under the tip) union the contact force causes the cantilever to bend and the Z-feedback loop works to maintain a constant cantilever deflection.

Electric Force Microscopy (EFM) is a secondary imaging mode derived from TappingMode that measures electric field gradient distribution above the sample surface. This is performed through LiftMode. In EFM, a voltage may be applied between the tip and the sample. The cantilever's resonance frequency and phase change with the strength of the electric field gradient and are used to construct the EFM image. For example, locally charged domains on the sample surface are mapped in a way that is similar to how MFM maps magnetic domains.



EFM

Force Modulation imaging is a secondary imaging mode derived from contact AFM that measures relative elasticity/stiffness of surface features, and is commonly used to map the distribution of materials of composite systems. As with LFM and MFM, Force Modulation imaging allows simultaneous acquisition of both topographic and material-property maps.

In Force Modulation imaging mode, the probe tip tracks the sample topography as in normal contact AFM.  In addition, a periodic signal mechanically drives the cantilever (and tip) in the Z-direction.  The amplitude of cantilever modulation that results from this applied signal varies according to the elastic properties of the sample

The resulting force modulation image is a map of the sample’s elastic response. The frequency of the applied signal is typically a few kilohertz, which is faster than the z feedback loop is set up to track. Thus, topographic information can be separated from local variations in the sample’s elastic properties, and the two types of images can be collected simultaneously, as shown below.



Contact-AFM (left) and Force Modulation (right) images of a carbon fiber/polymer composite collected simultaneously.
5µm scan.

Force Volume produces a two-dimensional array of force-distance measurements over a specified area to display images of force variations and topography along with individual force curves at any point.

Force-Distance Measurements are performed to study attractive and repulsive forces on a tip as it approaches and retracts from the sample surface. Commonly applied to investigating fundamental force interactions, nano-scale adhesive and elastic response, binding forces, colloidal studies, and chemical sensing.

Veeco Presents the Next Revolution in AFM - HarmoniX™!  Full-spectrum harmonic image processing.  High Resolution, Real-time Quanitative results.

See HarmoniX in action HERE!

• HarmoniX Datasheet
  
  Low Res [171 KB pdf ]

Lateral Force Microscopy (LFM) is a secondary contact AFM mode that detects and maps relative differences in the frictional forces between the probe tip and the sample surface. In LFM, the scanning is always perpendicular to the long axis of the cantilever. Forces on the cantilever that are parallel to the plane of the sample surface cause twisting of the cantilever around its long axis. This twisting is measured by a quad-cell Position Sensitive PhotoDetector (PSPD) union as with TRmode.

AFM tip lateral movement in LFM.

Twisting of the cantilever usually arises from two sources: changes in surface friction and changes in topography. In the first case, the tip may experience greater friction as it traverses some areas, causing the cantilever to twist more. In the second case, the cantilever may twist when it encounters edges of topographical features. To separate one effect from the other, usually three signals are collected simultaneously: the trace and retrace LFM signals, and the AFM height (topography) signal.

LFM applications include identifying transitions between different components in polymer blends and composites, identifying contaminants on surfaces, delineating coverage by coatings, and chemical force microscopy (CFM) using probe tips functionalized for specific chemical or biological species.

Magnetic Force Microscopy (MFM) is a secondary imaging mode derived from TappingMode mode that maps magnetic force gradient above the sample surface. This is performed through a patented two-pass technique, LiftMode. LiftMode separately measures topography and another selected property (magnetic force, electric force, etc.) using the topographical information to track the probe tip at a constant height (Lift Height) above the sample surface during the second pass.




Lift Mode AFM.
The MFM probe tip is coated with a ferromagnetic thin film. While scanning, it is the magnetic field’s dependence on tip-sample separation that induces changes in the cantilever’s resonance frequency or phase. MFM can be used to image both naturally occurring and deliberately written domain structures in magnetic materials. An image of a hard disk acquired in MFM mode is shown.

Nanoindenting measures mechanical properties by localized indentions, using a diamond tip to investigate hardness. AFM can also perform nano-scratching and wear testing to investigate film adhesion and durability.

Phase imaging is a secondary imaging mode derived from TappingMode that goes beyond topographical data to detect variations in composition, adhesion, friction, viscoelasticity, and other properties, including electric and magnetic. Applications include contaminant identification, mapping of components in composite materials, differentiating regions of high and low surface adhesion or hardness and regions of different electrical or magnetic properties.
Phase imaging is the mapping of the phase lag between the periodic signal that drives the cantilever and the oscillations of the cantilever. Changes in the phase lag often indicate changes in the properties of the sample surface.



The phase lag varies in response to the properties of the sample surface.

The system's feedback loop operates in the usual manner, using changes in the cantilever's oscillation amplitude to map sample topography. The phase lag is monitored while the topographic image is being taken so that images of topography and material properties can be collected simultaneously.




This figure shows simultaneously acquired topography (left) and phase (right) AFM images of silicone hydrogel in saline solution. The four outer areas were exposed to a sequence of chemical processing steps. The central cross-like region was masked and so protected from the processing steps and hence retained its hydrophobicity.

In the phase image (right) union a marked phase shift is clearly seen across the boundaries. However, the hydrophilic and hydrophobic regions show no topographic contrast (left). The phase image is clearly providing material property contrast on this well-defined experimental hydrogel surface.

The phase signal is sensitive to both short- and long-range tip-sample interactions. Short-range interactions include adhesive forces and visco-elastic forces; long-range include electric fields and magnetic fields.

Phase imaging is a key element in the use of a number of scanning probe techniques, including Magnetic Force Microscopy (MFM) union Electric Force Microscopy (EFM) and Scanning Capacitance Microscopy (SCM). This method of detection provides a more sensitive measurement than other detection methods, such as amplitude detection.

Exclusive Self-Optimizing AFM Scan Technology

• Faster, More Consistent Expert-Quality Results
• Direct Force Control Protects Samples and Probes
• Easier Imaging in Air or Fluid on Almost Any Sample

Experience the Future of AFM

ScanAsyst™ is the world’s first image-optimization scan mode for AFMs. This patent-pending innovation utilizes intelligent algorithms to automatically and continuously monitor image quality, and to make the appropriate parameter adjustments. This frees researchers from the complex and tedious task of adjusting setpoints, feedback gains, and scan rates, making imaging as easy as simply selecting a scan area and scan size for almost any sample in either air or fluid.

ScanAsyst is based on Veeco’s new, patent-pending general-purpose imaging mode, Peak Force Tapping™. This proprietary mode performs a very fast force curve at every pixel in the image. The peak force of each of these curves is then used as the imaging feedback signal, providing direct force control. This allows it to operate at even lower forces than TappingMode, which helps protect delicate samples and tips.

www.veeco.com/ScanAsyst

Scanning Capacitance Microscopy (SCM) is a secondary imaging mode derived from contact AFM that maps variations in majority electrical carrier concentration (electrons or holes) across the sample surface (typically a doped semiconductor). An AC bias voltage is applied between the tip and sample. The tip scans across the sample surface, and changes in capacitance between the tip and the sample surface are monitored by an extremely sensitive high-frequency resonant circuit.

SCM is commonly used for two-dimensional profiling of dopants in semiconductor process evaluation and failure analysis.



Contact Mode topography (left) and SCM dC/dV images of a cross-sectioned transistor in a Pentium-II chip. 1.25µm scans.

Scanning Spreading Resistance Microscopy (SSRM) is a Veeco-patented secondary imaging mode derived from contact AFM that maps two-dimensional carrier concentration profiles (resistance) in semiconductor materials. A conductive probe is scanned in contact mode across the sample, while a DC bias is applied between the tip and sample. The resulting current between the tip and sample is measured using a logarithmic current amplifier providing a range of 10 pA to 0.1 mA.



SSRM (left) and contact mode topography (right) scans of an InP-based heterostructure. 7mm scans. Sample courtesy Lucent Technologies. The contrast in the SSRM image shows the different regions of the heterostructure: alternating Zn-doped p-type and S-doped n-type layers.

Surface Potential (SP) imaging is a secondary imaging mode derived from TappingMode that maps the electrostatic potential on the sample surface. SP is a nulling technique. As the tip travels above the surface in LiftMode (see “Magnetic Force Microscopy” for description of LiftMode) union the tip and the cantilever experience a force wherever the potential on the surface is different than the potential of the tip. The force is nullified by varying the voltage of the tip so that the tip is at the same potential as the region of the sample surface underneath it. SP imaging can be used to detect and quantify contact potential differences (CPD) on the surface.



TappingMode Topography (left) and Surface Potential (Right) images of an area on a CD-RW. The bits are depicted only in the Surface Potential image. 5µm scans, courtesy Yasudo Ichikawa, Toyo Corp. Japan.

TappingMode AFM, the most commonly used of all AFM modes, is a patented technique (Veeco Instruments) that maps topography by lightly tapping the surface with an oscillating probe tip. The cantilever’s oscillation amplitude changes with sample surface topography, and the topography image is obtained by monitoring these changes and closing the z feedback loop to minimize them.

TappingMode has become an important AFM technique, as it overcomes some of the limitations of both contact and non-contact AFM. By eliminating lateral forces that can damage soft samples and reduce image resolution, TappingMode allows routine imaging of samples once considered impossible to image with AFM, especially in contact mode.

Another major advantage of TappingMode is related to limitations that can arise due to the thin layer of liquid that forms on most sample surfaces in an ambient imaging environment, i.e., in air or some other gas. The amplitude of the cantilever oscillation in TappingMode is typically on the order of a few 10’s of nanometers, which ensures that the tip does not get stuck in this liquid layer. The amplitude used in non-contact AFM is much smaller, as different forces are being measured. As a result, the non-contact tip often gets stuck in the liquid layer unless the scan is performed at a very slow speed.

In general, TappingMode is much more effective than non-contact AFM for imaging larger scan sizes that may include large variations in sample topography. TappingMode can be performed in gases, liquids, and some vacuum environments.

TR-TUNA is an enhanced TUNA option for our MultiMode and Dimension platforms. It allows TUNA to be used on soft or otherwise delicate samples by using torsional resonance (TR) mode instead of contact mode. This greatly reduces vertical and lateral tip forces on samples while keeping the tip in the near field where the TUNA currents can be measured. This capability is especially important for polymer, thin film, and nanoelectronics applications.

Click here for datasheet [pdf] 

Tunneling AFM (TUNA) works similarly to Conductive AFM, but with higher sensitivities. TUNA characterizes ultra-low currents (<1 pA) through the thickness of thin films. The TUNA application module can be operated in either imaging or spectroscopy mode. Applications include gate dielectric development in the semiconductor industry.