Scanned-cantilever atomic force microscope

We have developed a 3.6 µm scan range atomic force microscope that scans the cantilever instead of the sample, while the optical-lever detection apparatus remains stationary. The design permits simpler, more adaptable sample mounting, and generally improves ease of use. Software workarounds alleviate the minor effects of spurious signal variations that arise as a result of scanning the cantilever. The performance of the microscope matches that of scanned-sample instruments

Imaging spectroscopy with the atomic force microscope

Force curve imaging spectroscopy involves acquiring a force-distance curve at each pixel of an atomic force microscope image. Processing of the resulting data yields images of sample hardness and tip-sample adhesion. These images resemble Z modulation images and the sum of forward and reverse friction images, respectively, and like them exhibit a number of potentially misleading contrast mechanisms. In particular, XY tip motion has a pronounced effect on hardness images and the meniscus force on adhesion images

Hardware for digitally controlled scanned probe microscopes

The design and implementation of a flexible and modular digital control and data acquisition system for scanned probe microscopes (SPMs) is presented. The measured performance of the system shows it to be capable of 14-bit data acquisition at a 100-kHz rate and a full 18-bit output resolution resulting in less than 0.02-Å rms position noise while maintaining a scan range in excess of 1 µm in both the X and Y dimensions. This level of performance achieves the goal of making the noise of the microscope control system an insignificant factor for most experiments. The adaptation of the system to various types of SPM experiments is discussed. Advances in audio electronics and digital signal processors have made the construction of such high performance systems possible at low cost

Lateral forces during atomic force microscopy of graphite in air

Highly oriented pyrolytic graphite and boronated pyrolytic graphite were imaged in air by simultaneous normal and lateral force microscopy. A number of effects occurred when scanning over steps, including an increase in attractive forces from surface contamination which could be detrimental to the imaging of soft or weakly bonded samples. Contamination may also give rise to regions of high lateral force which do not seem to be associated with any topographic features. Finally, in atomic resolution images of graphite, atomic corrugation was clearer in the lateral cantilever deflection images than in the simultaneous topography and normal cantilever deflection images, demonstrating the high sensitivity of lateral force detection to topographic features

Float-polishing process and analysis of float-polished quartz

A fluid-mechanical model is developed for the float-polishing process. In this model laminar flow between the sample and the lap results in pressure gradients at the grooves that support the sample on a fluid layer. The laminar fluid motion also produces supersmooth, damage-free surfaces. Quartz substrates for applications in high-stress environments were float polished, and their surfaces were analyzed by optical scatterometry, photoacoustic spectroscopy, and atomic force microscopy. The removal of 100 µm of material by a lapping-polishing process, with final float polishing, left low levels of subsurface damage, with a surface roughness of approximately 0.2-nm rms

Giant magnetoimpedance: new electrochemical option to monitor surface effects?

Magnetoimpedance, MI, change due to surface modification of the sensitive element caused by biofluids was studied with the aim of creating a robust sensor capable of separating the chemical surface modification from the sensing process. A MI sensor prototype with an as-quenched FeCoSiB amorphous ribbon sensitive element was designed and calibrated for a frequency range of 0.5 to 10 MHz at an intensity of the current of 60 mA. Measurements as a function of the exposure time were made, first, in a regime where chemical surface modification and sensing were separated and then, in a regime where they were not separated (in a bath for fluids). The MI variation was explained by the change of the surface magnetic anisotropy. It was shown that the magnetoimpedance effect can be successfully employed as a new electrochemical option to probe the electric features of surface-modified magnetic electrodes when the biofluid, the material of the sensitive element, and the detection conditions are properly selected and synergetically adjusted.Comment: 22 pages, 6 figure