Silicon nitride cantilevers with oxidation-sharpened silicon tips for atomic force microscopy
ABSTRACT High-resolution atomic force microscopy (AFM) of soft or fragile samples requires a cantilever with a low spring constant and a sharp tip. We have developed a novel process for making such cantilevers from silicon nitride with oxidation-sharpened silicon tips. First, we made and sharpened silicon tips on a silicon wafer. Next, we deposited a thin film of silicon nitride over the tips and etched it to define nitride cantilevers and to remove it from the tips so that they protruded through the cantilevers. Finally, we etched from the back side to release the cantilevers by removing the silicon substrate. We characterized the resulting cantilevers by imaging them with a scanning electron microscope, by measuring their thermal noise spectra, and by using them to image a test sample in contact mode. A representative cantilever had a spring constant of ∼0.06 N/m, and the tip had a radius of 9.2 nm and a cone angle of 36° over 3 μm of tip length. These cantilevers are capable of higher resolution imaging than commercially available nitride cantilevers with oxidation-sharpened nitride tips, and they are especially useful for imaging large vertical features.
- SourceAvailable from: Giovanni Boero[show abstract] [hide abstract]
ABSTRACT: We have developed a new hybrid AFM probe combining an SU-8 polymer body with a full tungsten cantilever having a nanometric tip. The fabrication is based on surface micromachining a silicon wafer, where tungsten is sputter deposited in oxidation sharpened moulds to yield sharp tips with radius below 20 nm. The material properties of tungsten were measured, yielding a hardness of 14 GPa, a specific resistivity of 14.8 μohm cm and Young’s modulus of 380 GPa. Analyses of the probes show a mechanical quality factor of 90 in air, and a low contact resistance of 25 ohm on a gold sample is measured. AFM imaging is demonstrated. As a step in the development of a robust electrically conducting AFM probe, the results are very promising.Nanotechnology 01/2006; · 3.84 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: This paper presents a pyramid shaped three-dimensional 8 × 8 multi-electrode array for artificial retina application. Each electrode features a pyramid shape composed of one (1 1 1) plane and two vertical planes. The cone angle between the (1 1 1) plane and the vertical plane is 19.5 • , which is the sharpest angle, as far as reported [1–7]. The sharp pyramid shaped electrode is capable of penetrating the inner limiting membrane with minimal invasiveness, which in turns can stimulate retina cells more effectively than a square shaped two-dimensional electrode. The characteristic measurement of impedance magnitude and the phase shift of a single electrode are 1.19 M and −80.8 • at 1 kHz, respectively. Although the single three-dimensional electrode covers only 145 m 2 of the base area, its magnitude of impedance is as low as a 900 m 2 area two-dimensional electrode indicating that the three-dimensional electrode has higher signal-to-noise ratio than the two-dimensional electrode.Sensors and Actuators A: Physical. 01/2006; s 130–131:130-131.