Effects of Temperature and Light Illumination on the Current−
Voltage Characteristics of Molecular Self-Assembled Monolayer
Junctions

We systematically studied the charge transport properties of a series of self-assembled monolayer crossbar junctions with different alkanethiol and conjugated molecules, respectively. The junction was fabricated using a soft stamp-printing method. Current–voltage characteristics were measured at varied temperatures between 300 down to 90 K under different light illumination conditions. Strong temperature dependence and optoelectronic switching phenomena were observed in the as-fabricated junctions in both dark and light situations. To understand the charge transport mechanism, the Simmons and Fowler–Nordheim tunneling were used to analyze the experimental data. The distinctly different adsorbing nature of the top printed Au/molecule interface in the crossbar junctions is shown to play a dominant role in causing the asymmetric transport behavior. The charge injection barrier is strongly dependent on both the substrate temperature and the molecular length/conjugation structures. The barrier decreases with the increase of the substrate temperature and/or the molecular length, while a conjugated molecular structure can obviously enhance the junction charge transport. Our work may offer some useful information for developing molecular electronic devices.