Atomic Force Microscopy of electrical, mechanical and piezo properties of nanowires

Abstract

Careful methodology of Atomic Force Microscopy (AFM) regimes was developed for advanced examination of electrical transport, mechanical strength and electro-mechanical (piezoelectric) features of as-grown III-V semiconductor quasi-one-dimensional nanostructures. The thesis is based on the experimental work with the standard commercial measuring station. The general idea was to focus on the protocol of data acquisition and interpretation in order to obtain characteristics of elaborated structures and materials. We demonstrated the feasibility to implement various experiments on a regular station without visualization of a direct contact established between the microscope probe and the measured nanowires (NWs). The novelty of this work is in the utilization of solely AFM device for advanced studies of the NWs in direct contact achieved with the modern PeakForce-based QNM™, KPFM and TUNA™ regimes.

Semiconductor NWs receive an increasing attention of the research community because they are promised to become indispensable building blocks of many modern electronic and mechanical devices. Atomic force microscopy is a highly versatile technique, which was effectively used for studies of many classes of nanostructures developed during the last three decades. At the same time, no adequate summary of the capabilities and prospects of AFM instrument for investigation of NWs was made. An attempt to formulate such a summary is shown in the present thesis and in the list of related publications.

Peculiarities of electrical measurements of NWs with a small sized conductive probe were formulated in the study of passivated GaAs NWs, where different charge transport mechanism and surface-induced phenomena were considered. Focus on real conical (tapered) shape of wurtzite InP NWs was done permitting to find the Young’s modulus of wurtzite phase InP. Combining the advantageous material (GaAs), crystal composition (wurtzite), sized structure (NW) and method of study (conductive AFM) demonstrated the way to use GaAs NWs for combined piezo-phototronic electrical energy generators.