Active-probe AFM across applications
Mass detection by resonance frequency shift
Mass detection with nano analytik active cantilevers is based on changes in resonance frequency caused by mass loading or removal during electron- or ion-beam processing inside an SEM/FIB, enabling in-situ, real-time monitoring of nanoscale mass changes.
The system architecture is based on a low-mass, high-Q active cantilever that is vacuum-compatible for SEM use, with piezoresistive readout integrated directly on the cantilever. Actuation is achieved through patented electrothermal means to sustain near-resonant oscillation. SEM integration requires stable, vacuum-compatible mounting with minimal damping and robust electrical connections, together with shielding to reduce beam-induced noise.
Indicative performance: Picogram-scale mass sensitivity, depending on the active cantilever geometry and Q-factor, with real-time millisecond-scale response governed by the drive and readout bandwidth and operating conditions within the SEM environment.
Resonance tracking
The active cantilever is driven near its resonance frequency while a feedback loop maintains stable oscillation.
Mass change
Material deposition, removal or adsorption changes the effective mass of the oscillating active cantilever.
Frequency shift
The resulting shift in resonance frequency is tracked in real time to determine nanoscale mass changes.
By continuously tracking the resonance frequency, accumulated or removed mass on the tip or cantilever can be inferred during beam-induced deposition, etching, sputtering, adsorption, or related processes. In simple terms, adding mass lowers the resonant frequency.
The oscillating path helps minimize non-mass-related drift, while the control electronics — often a phase-locked loop or frequency-tracking system — monitor f0, Δf, amplitude and phase to provide a clean mass-sensitive signal.
The measurement begins with baseline characterization of resonance frequency and quality factor under SEM conditions. Real-time operation maintains a fixed oscillation amplitude while recording the resonance frequency shift as material is deposited or removed during beam exposure. Optional phase and amplitude monitoring can help distinguish mass-loading effects from other perturbations.
Calibration should be performed with known mass changes under SEM/FIB conditions. Corrections for beam-induced heating, charging, sputtering and environmental drift are necessary. The oscillating approach helps minimize topography-related effects and improve mass accuracy.
- Real-time monitoring of thin-film and beam-induced deposition
- Monitoring of material removal during etching and sputtering
- Beam-assisted and mass-targeted material modification
- Adsorption and desorption studies
- Investigation of contamination and oxide growth
- In-situ studies of nanoscale mass changes during processing