Multiple-Probe Scanning Probe Microscope (original) (raw)

2018, Compendium of Surface and Interface Analysis

Multiple-probe scanning probe microscope (MP-SPM) was developed to overcome difficulties in characterizing physical properties of nanoscale structures and materials with conventional SPM families, such as a scanning tunneling microscope (STM), an atomic force microscope (AFM), and the related proximal probe microscopes [1-14]. Conventional SPMs use a single probe to observe surface structures and local properties at a high-spatial resolution down to atomic scale. In the case of STM, as shown in Fig. 64.1a, an electrical current flowing to/from a conductive and atomically sharpened probe from/to a conductive sample establishes a concentration of current at a surface of the sample and this is the reason why STM is very sensitive to local density of states (LDOS) of the surface. Here, since the STM probe and the surface are separated by a small (typically 1 nm) vacuum gap, current is obtained via tunneling of electrons across the spatial gap, providing very accurate control of probe-to-sample distance via a feedback control to maintain the tunneling current constant, for example. As readily understood from Fig. 64.1a, conventional STM is measuring electrical current flowing in the direction perpendicular to the surface plane as shown by the red arrow. Therefore, a single-probe STM is essentially not suitable to measure electrical properties in the direction parallel to sample surfaces, while, in many cases, we want to measure electrical properties of surfaces, nanomaterials placed on surfaces, and device structures fabricated on surfaces. Therefore, multiple-probe