Atomic Force Microscopy

About

Background Scanning probe microscopy constitutes a family of advanced techniques for surface analysis. Although scanning tunneling microscopy (STM) was invented first, the current progress in scanning probe microscopy of polymers, metals, semi-conductive and insulating materials largely stems from the development of atomic force microscopy (AFM). The universal character of the repulsive forces between the tip and the sample, which is employed for surface analysis in AFM, enables the examination of a practically unlimited range of materials. Initially introduced as the analogue of STM for the high-resolution profiling of non-conducting surfaces, AFM has developed into a multifunctional technique suitable for characterization of topography, adhesion, mechanical, and other properties on scales from hundreds of microns to nanometers and even to the atomic scale. AFM has been recognized by the semiconductor industry and material science, in general, to be a powerful technique to obtain nanoscale information on material surfaces. It is used for measuring not only inorganic materials such as metals and semiconductors, but also organic materials and biomaterials. Also, by applying the technology of AFM to microscopy, new functions, such as a magnetic force microscope (MFM) and a scanning near-field optical microscope (SNOM) and Raman Enhanced Microscopy (REAFM) are put to practical use. Technology Description Traditional AFM also has been integrated with an external laser to probe photo physical processes, and inter- and intra-molecular forces. However, there are several drawbacks in combining confocal microscopy with AFM, mainly due to the difficulty of alignment of the external optical sources given the tight coupling between the tip and the sample surface, adding complexity to the measurements and also adding costs due to the expensive instrumentation. Recently, the measurement of optoelectronic properties in local area of materials and devices has become greatly demanded. Although many kinds of scanning probe microscopes have been developed for satisfying the requirement of nanotechnology, there is still a need for a microscope technique which combines integrated laser and topography information of the nano-local area. Researchers at the University of New Mexico have developed a method to fabricate a new generation of high resolution atomic force microscopy (AFM) tips based on both as-grown and etched GaN nanowires. The GaN AFM tips serve as high aspect ratio probing microscopy to define vertical walls with almost 90° resolution compared to the scanning angle.  In addition, these AFM tips have an aspect to ratio ranging from 10 to 100. Furthermore, these tips serve as quasi atomic lateral resolution probing microscopy, and as a self-aligned AFM tip capable to being optically and electrically pumped for confocal microscopy. GaN is a wide bandgap semiconductor which can be optically or electrically pumped to provide a self-aligned NSOM capability. Advantages Extend capabilities of AFM/ STM measurements       More suitable Si cantilevers with lasing tips High aspect ratio probing microscopy to define vertical walls with almost 90O resolution compared to the scanning angle AFM tip with an aspect to ratio ranging from 10 to 100 Capable to being optically and electrically pumped for confocal microscopy Applications in microscopy, optical imaging, atomic force microscopy, lithography