Ultra-Short Silicon Cantilevers
In order to cover a wide range of possible applications using High Speed AFM (HS-AFM), demonstrator probes of Ultra-Short Silicon Cantilevers (USC-Si) with different mechanical properties have been successfully realized.
Individual demonstrator probes have been selected and characterized in detail (see table below):
| Technical Data | 1 | 2 | 3 | 4 | 5 | 6 |
|---|---|---|---|---|---|---|
| Resonance Frequency1) [MHz] | 25 | 5 | 2 | 4 | 0.5 | 1 |
| Force Constant1) [N/m] | 43* | 6* | 1.5 | 12* | 0.25 | 4 |
| Q-factor1) (in air) | - | 570 | 380 | 450 | 280 | 320 |
| Cantilever length [µm] | 2.5 | 7 | 12 | 12 | 25 | 30 |
| Cantilever width [µm] | 2 | 3 | 4 | 4 | 6 | 7 |
| Cantilever thickness [nm] | 200 | 250 | 250 | 500 | 250 | 700 |
| Coating [nm] | none | 70 (Au) | 70 (Au) | 70 (Au) | 30 (Al) | 70 (Au) |
| 1) Force constant, resonance frequency and Q-factor measured by thermal tune with a laser vibrometer system (* force constant of stiffer cantilevers calculated based on geometric data and material properties) | ||||||
The Electron Beam Deposited (EBD) tip implemented on these cantilevers is made of High Dense Carbon / Diamond Like Carbon (HDC / DLC). This material offers excellent robustness and very high wear resistance which are essential properties in High Speed Scanning. Indeed as in High Speed AFM the tip can travel at a speed of a few mm/s in contact with the sample, tip wear is very critical.
The tip height is adjusted to 2.5 µm and the aspect ratio is approximately 1:5 in order to obtain the best compromise between maximum cantilever-sample separation and minimum tip mass.
The tip radius of curvature is well below 10 nm which allows a lateral resolution capability in the lower nanometer regime.
The corners of the support chip are lowered in order to avoid any accidental contact between the support chip and the sample.
The reflex coating (thin gold or aluminum layer) on the detector side of the cantilevers enhances the reflectance of the laser beam and prevents light from interfering within the cantilever.
Status: First demonstrators realized
