Damage silicon nitrides

For imaging applications, minimisation of the damage to DNA molecules by the AFM tip is essential. One method of less-invasive imaging is based on phase (rather than height) imaging, which employs for instance 100 mm long silicon nitride cantilevers with narrow arms inserted into a fluid cell [65]. Alternatively, or better complementary, the operation in liquids [66], and... 

So far, two types of metallic tips have been typically reported. One is a metal-coated cantilever and the other is etched metallic wire, each of which is used in a suitable combination with the feedback scheme of tip-sample distance control (see Sect. 4.3). The metal-coated cantilever is fabricated conveniently from a commercially available silicon (Si) or silicon nitride (SisN4) cantilever of AFM by depositing thin metallic film onto the probe surface (Fig. 16.5a) [31-33]. Metal with >99.999% purity is thermally evaporated under vacuum condition and deposited onto the probe surface slowly with a rate of less than 1 A/s in order not to damage the tip apex. The deposition thickness is typically several tens of nanometers. A small diameter of several tens of nanometers at the tip is easily obtained. 

Figure 8.42 Fracture surface of silicon nitride failure was initiated from a contact-damage surface crack.

G. Subhash, M. A. Marszalek and S. Maiti, Sensitivity of Scratch Resistance to Grinding Induced Damage Anisotropy in Silicon Nitride"./ Am. Ceram. Soc., 89 (8), 2528-2536 (2006). 

Akimune, Y, Katano, Y, and Matoba, K, 1989, Spherical-Impact Damage and Strength Degradation in Silicon Nitrides for Automobile Turbocharger Rotors, J. Am. Ceram. Soc., 72[8],pp. 1422-1428. 

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