Nanoscale materials and device characterization via a scanning microwave microscope

The vector network analyzer (VNA) architecture as it exists today has the ability to measure impedances close to the analyzer´s own characteristic impedance (i.e., 50 ohms) with good precision up to 100GHz stimulus frequency. However, the measurement precision and resolution provided by a VNA drop by two orders of magnitude as impedance deviates from 50 ohms. We propose a solution that remedies the lack of measurement precision and resolution for large and small impedances when measured by a VNA. A new scanning microwave microscope (SMM) that utilizes a half-wavelength resonator in conjunction with a diplexer connected to a VNA to perform very sensitive capacitance measurements at the tip of a conductive atomic force microscope (AFM) is discussed. These measurements are achieved via transformation of the high impedance (i.e., the very small capacitance between the AFM tip/sample to the ground) to 50 ohms (i.e., the measurement system´s characteristic impedance) using a half-wavelength resonator and diplexer.