We have used a simple process to fabricate small rectangular cantilevers out of silicon nitride. They have lengths of 9–50 μm, widths of 3–5 μm, and thicknesses of 86 and 102 nm. We have added metallic reflector pads to some of the cantilever ends to maximize reflectivity while minimizing sensitivity to temperature changes. We have characterized small cantilevers through their thermal spectra and show that they can measure smaller forces than larger cantilevers with the same spring constant because they have lower coefficients of viscous damping. Finally, we show that small cantilevers can be used for experiments requiring large measurement bandwidths, and have used them to unfold single titin molecules over an order of magnitude faster than previously reported with conventional cantilevers.
We have used a prototype small cantilever atomic force microscope to observe, in real time, the interactions between individual protein molecules. In particular, we have observed individual molecules of the chaperonin protein GroES binding to and then dissociating from individual GroEL proteins, which were immobilized on a mica support. This work suggests that the small cantilever atomic force microscope is a useful tool for studying protein dynamics at the single molecule level.
This paper presents the first known image reconstruction of complex probe tip shapes and the removal of those shapes from reentrant topologies that are encountered in critical dimension (CD) measurements. Algorithm improvements are described that enable reentrant image reconstruction. In addition, a solution is presented which eliminates image artifacts that result from noise when using Legendre transform or “slope-matching” reconstruction techniques. The new methods are compared to existing technology and demonstrated on reentrant features. Although demonstrated with two-dimensional profiles, the methods are readily extendable to three-dimensional morphologies. Tip wear effects on CD measurement are investigated and compared with the previous state-of-the-art method (“tip width subtraction”) and fully reconstructed images, clearly showing superior measurement stability for the image reconstruction method. Finally, CD measurements derived from reconstructed images are compared directly with Hitachi S4000 and S5000 cross-section SEM (X-SEM) data. The results show a close match between the SEM and CD AFM data.
The lateral resolution of scanning thermal microscopy (SThM) has hitherto never approached that of mainstream atomic force microscopy, mainly due to poor performance of the thermal sensor. Herein, we report a nanomechanical system-based thermal sensor (thermocouple) that enables high lateral resolution that is often required in nanoscale thermal characterization in a wide range of applications. This thermocouple-based probe technology delivers excellent lateral resolution (∼20 nm), extended high-temperature measurements >700 °C without cantilever bending, and thermal sensitivity (∼0.04 °C). The origin of significantly improved figures-of-merit lies in the probe design that consists of a hollow silicon tip integrated with a vertically oriented thermocouple sensor at the apex (low thermal mass) which interacts with the sample through a metallic nanowire (50 nm diameter), thereby achieving high lateral resolution. The efficacy of this approach to SThM is demonstrated by imaging embedded metallic nanostructures in silica core-shell, metal nanostructures coated with polymer films, and metal-polymer interconnect structures. The nanoscale pitch and extremely small thermal mass of the probe promise significant improvements over existing methods and wide range of applications in several fields including semiconductor industry, biomedical imaging, and data storage.
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