An ultra-stable setup for measuring electrical and thermoelectrical properties of nanojunctions

Abstract

We present a setup that is excellently suited to measure the electrical and thermoelectrical transport across single-molecule junctions at both room temperature and low temperatures. It employs a sandwich configuration of two silicon carbide chips each equipped with metallic electrodes. Upon compression with an external piezo/spring mechanism, fine-tuned displacement control is achieved such that ultrastable atomically thin nanojunctions can be established. As a consequence of its stability, the setup gives access to point-by-point comparisons of electrical and thermoelectrical transport across single-molecule contacts. As a first demonstration of the capabilities of our setup, we present experiments with gold-molecule-gold contacts. Investigating a large ensemble of nanojunctions, each fully characterized by current-voltage characteristics and thermovoltage, correlations between these quantities are uncovered which can be rationalized within the Landauer transport picture. When including characteristics with resonant features, the Seebeck coefficient adds the decisive parameter to fully describe datasets within a resonant tunneling model. The setup provides further potential of controlling additional parameters as it is optically fully transparent. It also allows for nearly arbitrary material combinations for electrode-nanoobject object-electrode nanojunctions.