HR AFM

Electronics in the HR AFM are constructed around industry-standard USB data acquisition electronics. The critical functions, such as XY scanning, are optimized with a 24-bit digital to analog converter. With the analog Z feedback loop, the highest fidelity scanning is possible. Vibrating mode scanning is possible with both phase and amplitude feedback using the high sensitivity phase detection electronics.

Software for acquiring images is designed with the industry standard LabVIEW™ programming visual interface instrument design environment. There are many standard functions, including setting scanning parameters, probe approach, frequency tuning, and displaying images in real time. LabVIEW™ facilitates rapid development for those users seeking to enhance the software with additional special features. LabVIEW also enables the HR AFM to be readily combined with any other instrument using LabVIEW.

Pre-Scan Tab

All of the functions required before making a scan are on the pre-scan tab. This includes selecting the scan mode, red dot alignment, frequency scan, and automatic tip approach.

Scanning Tab

Images are acquired using the scanning tab. Parameters selected on the scanning tab include the scan size, scan rate, GPID parameters, and the color scale used for displaying images. Included with the scanning tab is an image buffer capability that facilitates in-zooming and out-zooming.

Modes Tabs

Software control for optional modes such as MFM, EFM, and advanced F/D are found in the modes tabs. The example shown here is of the advanced F/D mode tab. This allows fine control of all the parameters controlling acquisition of force-distance curves, as well as acquisition of F-D curve maps. Mapping of curve sin this way allows the user to locate and visualize regions of the sample with differing properties, such as presence of specific molecules, or mechanical properties.

Image Analysis Software

Included with the HR AFM is the Gwyddion open source SPM image analysis software. This complete image analysis package has all the software functions necessary to process, analyze, and display SPM images.

• Visualization: false color representation with different types of mapping
• Shaded, logarithmic, gradient- and edge-detected, local contrast representation, and Canny lines
• OpenGL 3D data display: false color or material representation
• Easily editable color maps and OpenGL materials
• Basic operations: rotation, flipping, inversion, data arithmetic, crop, and resampling
• Leveling: plane leveling, profiles leveling, three-point leveling, facet leveling, polynomial background removal, leveling along user-defined lines
• Value reading, distance, and angle measurement
• Profiles: profile extraction, measuring distances in profile graph, and profile export
• Filtering: mean, median, conservative denoise, Kuwahara, minimum, maximum, and checker pattern removal
• General convolution filter with user-defined kernel
• Statistical functions: Ra, RMS, projected and surface area, inclination, histograms, 1D and 2D correlation functions, PSDF, 1D and 2D angular distributions, Minkowski functionals, and facet orientation analysis
• Statistical quantities calculated from area under arbitrary mask
• Row/column statistical quantities plots
• ISO roughness parameter evaluation
• Grains: threshold marking and un-marking, and watershed marking
• Grain statistics: overall and distributions of size, height, area, volume, boundary length, and bounding dimensions
• Integral transforms: 2D FFT, 2D continuous wavelet transform (CWT), 2D discrete wavelet transform (DWT), and wavelet anisotropy detection
• Fractal dimension analysis
• Data correction: spot remove, outlier marking, scar marking, and several line correction methods (median, modus)
• Removal of data under arbitrary mask using Laplace or fractal interpolation
• Automatic XY plane rotation correction
• Arbitrary polynomial deformation on XY plane
• 1D and 2D FFT filtering
• Fast scan axis drift correction
• Mask editing: adding, removing or intersecting with rectangles and ellipses, inversion, extraction, expansion, and shrinking
• Simple graph function fitting, critical dimension determination
• Force-distance curve fitting
• Axes scale calibration
• Merging and immersion of images
• Tip modeling, blind estimation, dilation and erosion

The HR AFM includes 2 video optical microscopes for viewing the sample and probe. The video microscopes are essential for locating features on a surface, making a safe and efficient probe approach, and aligning the light lever force sensor.

Top View Video Microscope

From the top, the HR AFM has a research grade video optical microscope with a 7:1 mechanical zoom, a 5 MP camera, and a coaxial light. The with a resolution of < 2 microns, this microscope is ideal for locating features on a surface for scanning.

Side View Video Microscope

A side view video microscope, has a 2 mp camera and an off axis LED light source. This camera is used for visualizing the distance between the probe and the sample. This microscope is especially helpful for assisting probe approach on clear samples as well as samples that don't reflect light.

The HR AFM utilizes a unique probe holder/exchange mechanism. Probes are held in place with a spring device that mates with a probe exchange tool. With the probe exchange tool, changing probes takes only a few minutes.

Quick and Easy AFM Probe Exchange

The probe holder insert is removed from the HR AFM.

R to L: Box of probes, probe exchange tool, and probe holder insert.

Activating the probe spring clip by applying light pressure.

The true measure of an AFM is the quality of images it measures. With a noise floor of less than 35 picometers, and 28 bit scanning resolution, the HR AFM is capable of measuring the highest resolution images on many types of samples including: polymers, 2-D samples, crystals, ceramics, bio molecules, biomaterials, and semiconductors.

2 X 2 microns

500 X 500 nm

250 X 250 nm

2 X 2 microns

500 X 500 nm

250 X 250 nm

Vibrating mode images of collagen fibrils; 3µm × 3µm × 19.8 nm	Single layer graphene sheets on silicon wafer	Graphene on crystalline nickel surface
12 × 12 micron scan of a polymer blend	8 × 8 µm image of polymeric nanocapsules	Indium Tin Oxide electrode surface; 1.3 µm × 1.3 × µm × 21 nm
Individual dsDNA molecule; 250 × 250 × 1.2 nm scan	Highly linear scan of silicon reference sample	Phase image of polymer blend showing discrimination of different phases
Network of DNA molecules, 1 µm × 1µm × 3.5 nm micron scan	Multilayer graphene on silicon wafer	Single layer graphene on silicon wafer; 1µm × 1µm × 12.7nm

Vibrating mode images of collagen fibrils; 3µm × 3µm × 19.8 nm

Single layer graphene sheets on silicon wafer

Graphene on crystalline nickel surface

12 × 12 micron scan of a polymer blend

8 × 8 µm image of polymeric nanocapsules

Indium Tin Oxide electrode surface; 1.3 µm × 1.3 × µm × 21 nm

Individual dsDNA molecule; 250 × 250 × 1.2 nm scan

Highly linear scan of silicon reference sample

Phase image of polymer blend showing discrimination of different phases

Network of DNA molecules, 1 µm × 1µm × 3.5 nm micron scan

Multilayer graphene on silicon wafer

Single layer graphene on silicon wafer; 1µm × 1µm × 12.7nm

Scanning Modes

The HR AFM includes the most commonly used AFM Modes. The are:

Vibrating Mode (tap)	Vibrating mode imaging is the most common mode for measuring topography images with an AFM. In vibrating mode the vibration amplitude of the probe is held constant during a scan. Adjustable parameters include the vibrating frequency, amplitude of vibration, and the amount of dampening of the vibrating probe.
Non-vibrating (contact)	In non-vibrating mode, commonly called contact mode, the deflection of a cantilever is held constant during scanning. This mode is often used for scanning in liquids and is also used for measuring force-distance curves.
Phase	Phase mode images are measured in vibrating mode and are useful for identifying different areas of hardness on a surface. The technique operates by measuring the phase change caused by differing materials on a surface while scanning.
Lateral Force	Lateral force mode measures the local friction a probe senses as it is scanned across a surface. The friction can be caused by surface texture or by differing chemical composition.
Force - Distance (F/D)	Force Distance Curves measure the deflection of a cantilever as it interacts with a surface. Force-Distance measurements monitor such surface parameters as: Adhesion, Stiffness, Compliance, Hardness, and Contaminate Thickness. This advanced AFM module is flexible and enables many types of experiments.

Optional modes that can be purchased with the HR AFM include:

Magnetic Force	Measures surface magnetic field by incorporating a magnetic probe into the AFM. MFM is used to generate images of magnetic fields on a surface, and is particularly useful in the development of magnetic recording technology. Magnetic fields associated with individual magnetic nanoparticles are also revealed through MFM.
Electric force	Electrostatic Force Microscopy (EFM) is a type of dynamic non-contact atomic force Microscope where the electrostatic force is probed. “Dynamic” here means that the cantilever is oscillating and does not make contact with the sample. This force arises due to the attraction or repulsion of separated charges.
Advanced F/D	Force Distance Curves measure the deflection of a cantilever as it interacts with a surface. Force-Distance measurements monitor such surface parameters as: Adhesion, Stiffness, Compliance, Hardness, and Contaminate Thickness. This advanced AFM module is flexible and enables many types of experiments.
Conductive AFM	The C-AFM measures topography and conductivity images simultaneously. This option allows measuring current-voltage (I/V) curves at specific locations on a surface.
Lithography	This NanoLithography software option enables the AFM probe to alter the physical or chemical properties of the surface. Created in LabVIEW and integrated with the AFMControl software. VI's are available to customers who want to modify the software and create new capabilities.
Scanning Tunneling	In the STM, the current flow between a metal probe and a sample are used to control the distance between the conductive probe and conductive surface. When the probe is scanned across the surface, if the current between the probe and surface are held constant with a feedback control loop driving a piezo ceramic, the topography of the sample's surface in measured.
Open Liquid Cell	This option includes a special probe holder and open liquid cell for scanning samples submerged in liquids. The Dunk and Scan can directly replace the HR AFM probe holder.

Direct Drive Option

In the HR AFM with direct drive option, three motors are used move the plate that supports the light lever force sensor. When the probe approaches the surface, it moves directly onto the features viewed in the tip view optical microscope. The forth motor, controls the focus of the top view optical microscope. If all four motors are activated at the same time, the top view video optical microscope will state focused on the probe.

There are several benefits to the the 4 motor option for the HR AFM. The include:

• Simulates direct drive tip approach.
• Motorized control of probe sample angle.
• Focusing on the probe during tip approach.
• Sample to Probe focus with software control.

Q-Box

The AFMWorkshop Q-Box filters both structural and acoustic vibrations and assures the highest resolution images. The Q-Box, constructed from medium density fiberboard has high density foam for filtering sound and a floating platform for filtering structural vibrations.

The HR AFM has a number of options to enhance its performance and expand its capabilities. These options may be purchased with a new AFM or at any time after the original purchase.

HR AFM Specifications