Scanning Force Microscopy in 7 easy steps
February, 2019 : Atomic force microscopes take time and practice to understand and operate the machine correctly to obtain high quality AFM images. With this in mind, AFMWorkshop has developed a new, simplified step-by-step scanning software to assist new users with gaining the skills and techniques necessary for scanning and scanning great AFM images. The 7-Step Scanning Software from AFMWorkshop was developed with AFM education and training in mind, as it breaks down the scanning procedure into 7 easy to follow steps. This allows users with minimal training operating an atomic force microscope to scan high-quality images without a headache. In this newsletter, we will introduce the 7-Step Scanning Software, and take a tour through each of the 7 steps involved with scanning.
Fig 1. 7-Step Scanning Software Window
Introduction to the 7-Step Scanning Software
The 7-Step Scanning Software is designed for simplicity and routine scanning, and is compatible with all AFMWorkshop AFMs. It was created primarily for beginner users of atomic force microscopes, and for educational and training settings; however, the 7-Step Software is a quick and easy way for even the most experienced AFM users to obtain high-quality images. The software breaks the scanning procedure into 7 easy-to-follow steps:
- Choosing the Mode
- Aligning the Laser
- Optimizing the Photodetector
- Obtaining Resonance Frequency (Vibrating Mode Only)
- Performing Tip Approach
- Executing the Scan
- Performing Tip Retract
There is also an option to perform Force Distance curves, as well as an option to adjust more advanced settings.
Breaking the scanning procedure into small steps makes it much easier for beginners to understand the process of creating an AFM image, which in turn will make them better AFM users in the future. For each step, the software provides a small explanation of the step at the top of the software window, making it even easier to learn the basics of scanning samples with an atomic force microscope.
In this newsletter, we will break down the 7 steps for scanning to give you an idea of how useful the 7-Step Scanning Software can be, especially to beginner operators of AFM.
7-Step Scanning: Pre-Scan, Scan, and Post-Scan
Perhaps not surprisingly, the most important steps to consider when taking an AFM imaging scan are the pre-scan steps. Preparing your sample and instrument properly can make a world of difference when actually scanning an image; and without properly preparing, you may not even get an image at all.
This is the idea behind the 7-Step Scanning Software. In steps 1-5, the software outlines the steps before scanning, including Mode, Laser, Photodetector, Resonance, and Tip Approach. Following these steps carefully will allow the user to go on and perform imaging scans with little disruption. Step 6 represents the scan itself, while step 7 is simply the post-scan tip retract.
Mode: The first step is to choose which mode to scan in. The 7-Step Scanning Software provides two options: Vibrating (Tapping) and Non-Vibrating (Contact).
Laser: To align the laser to the cantilever, a camera application is utilized, while positioning the laser is as simple as using the XY translators. Once the laser is accurately aligned to the cantilever, the user can mark the spot in the software, making it easier and quicker to align the laser in future scans.
Detector: To optimize the amount of light collected by the photodetector, slowly move the photodetector back and forth using the translators, while monitoring the "Detector" section of the 7-Step Software. The green square represents the four quadrants of the photodetector, and the red spot represents the laser light. The red dot inside the green square tells the user that the laser light is shining directly on the center of the photodetector, yielding a maximum signal.
Resonance: For vibrating mode only, this is where the user will find and set the cantilevers resonant frequency. To set the range of a frequency sweep, simply use the green (start) and red (stop) range lines. Once the resonant frequency is found, it is best to perform another sweep of the peak (resonant frequency) to find the most accurate frequency (highest amplitude). Use the blue grid line to select the frequency for scanning.
Tip Approach: Once an area of interest for scanning is found using the camera and XY translators, users will perform a tip approach. First, it is best to bring the probe closer to the sample (within 1 mm) using the manual Z motor control (be sure not to select a speed that is too fast, to avoid tip crashing). This will reduce the time it takes for tip approach to be executed. Then, simply press "Start Tip Approach". The Z piezo will extent and retract while the Z motor takes small steps toward the sample. Wait until the probe and sample are in feedback with one another before scanning.
Scan: Scanning is actually one of the easier steps of AFM operation. Once the parameters are set (Scan Size, Response Rate, Interaction, Output), the scan takes care of itself. First the user will choose a scan size (up to 50 microns). Next, choose the desired response rate (higher for tall features, lower for large samples) and interaction value (higher for contamination, lower for soft samples). Lastly, choose the desired output signals (Voltage, Displacement, Phase, Amplitude, Error, etc). The scan will execute upon pressing "Start".
Tip Retract: After the scan has completed, it is important to first perform a Tip Retract before using the manual Z motor control, to avoid any damage to the probe or sample. Once Tip Retract is executed, the manual Z motor control can be used to move the probe further away from the sample.
Scanning an image with an AFM is a fairly straightforward process. Once the probe and sample are in feedback (Tip Approach), the user just needs to set the scan parameters and press start. With proper preparation and care taken in pre-scanning, users will be able to generate clear, usable AFM images.
This is the idea behind the 7-Step Scanning Software from AFMWorkshop. The software will help expand the use of AFMs by making it easier to learn the basics of scanning, and will help increase productivity in situations where routine scanning is needed. To learn more about the 7-Step Scanning Software, or any other AFMWorkshop products, please contact us with the link below.