The following are the core points and key steps for assembling nano scanning probe microscopes:
Basic framework construction
1. Installation of vibration isolation system: Use an air spring vibration isolation table or sponge rubber shock absorber as the base, calibrate with a level to ensure an error of ≤ 0.1 °, and ensure that the environmental vibration noise is below 1 μ m level; If equipped with an active vibration isolation system, connect the pneumatic/hydraulic pipelines according to the instructions.
2. Installation of shielding cover: Install a metal shielding cover on the vibration isolation platform, with the cover body insulated from the base and reserved ventilation openings to prevent temperature drift; Some models require synchronous installation of active vibration isolation components.
Sample stage and positioning system
1. Mechanical installation: The sample stage often uses a three-dimensional nano positioning stage, and during installation, it is necessary to ensure that the motion axis is strictly orthogonal to the scanning direction of the probe; Use a laser interferometer or optical microscope to check the flatness of the scanning table, and the tilt angle should be less than 0.05 °.
2. Sample fixation: Fix the sample using double-sided tape, vacuum adsorption, or a magnetic base to ensure that the surface is parallel to the scanning table; Conductive samples need to establish electrical contact with copper foil or silver paste to avoid charge accumulation.
Probe and cantilever system
1. Probe holder assembly: Combine the adjustable pitch angle base of the probe holder with the cantilever slot, and use vacuum suction or electrostatic clamping to fix the probe to prevent mechanical deformation; Adjust the long axis of the cantilever to be parallel to the X-axis of the sample stage, with a deviation controlled within ± 0.5 °.
2. Spacing setting: First, use an optical microscope to preliminarily adjust the gap between the cantilever and the sample to 10-50 μ m, then switch to interferometer mode, monitor the cantilever deflection using laser reflection signals, and gradually reduce the gap to the sub nanometer level.
Debugging of optical detection system
1. Laser alignment: A semiconductor laser is coupled to a beam splitter through an optical fiber and vertically irradiated onto the back of the cantilever, with a spot diameter of approximately 50 μ m; The four quadrant photodetector needs to be coaxial with the reflected light from the cantilever, and the focal length of the lens should be adjusted to focus the light spot on the center of the detector.
2. Sensitivity optimization: Adjust the gold coating on the cantilever reflection area to increase the reflectivity (>70%), and fine tune the detector gain to ensure that even small displacements (<1 nm) of the cantilever can generate distinguishable voltage signals.
Electronic control system
1. Signal connection: The QPD output signal is connected to a low-noise current amplifier (gain 10 ⁴ -10 ⁵ V/A), and the filtering cutoff frequency is set to 10 kHz to suppress high-frequency noise; The Z-axis piezoelectric ceramic drive signal is generated by a PID controller, and the feedback bandwidth needs to be adjusted according to the cantilever resonance frequency (10-500 kHz).
2. Data acquisition: The data acquisition card (≥ 16 bit resolution) needs to be synchronized with the scanning trigger signal, and the sampling rate should be at least 5 times the resonance frequency; Software calibration zero drift, set scanning area (such as 50 × 50 μ m ²) and pixel dwell time (1-100 ms/pixel).
Calibration verification
After assembly, noise testing, imaging mode validation (contact/tap mode), and nonlinear correction (such as graphene standards) are required to ensure that the instrument performance meets the standards.
In summary, the assembly of nanoscan probe microscopes requires a comprehensive combination of precision mechanical adjustment, optical alignment, electronic control, and environmental protection technologies. Each step must strictly follow the specifications to ensure the high-resolution performance of the instrument.