Effect of Environmental Humidity and Temperature on the Variations in Physiochemical Properties of Monolayer Graphene in Sliding Electrical Contact Interface

We study the physiochemical properties of supported single-layer graphene (SLG) rubbed with an electrically-biased conductive AFM (cAFM) probe under various environmental humidity and temperature. During the experiment, the relative humidity is changed from 0% to 80% while the temperature is controlled between 10°C and 80°C to regulate the capillary condensation of nanoscale water meniscus formed around the cAFM probe-SLG contact zone. The effective work function (WF), structural, and chemical properties of rubbed SLG are respectively investigated by Kelvin probe force microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. When a positive voltage is applied to the probe, tunneling triboelectric (TTE) effect occurs, which modulates the electrical properties, i.e., the effective work function (WF) of SLG. On the other hand, when a negative bias is applied, water molecules in the nanoscale water meniscus will be electrolyzed, leading to local oxidation of SLG. Together with TTE, chemical functionalization of SLG surface also results in variations in the effective WF and chemical properties of SLG that depends on the sliding velocity of cAFM probe, humidity, and temperature. Our findings offer valuable insights into the design of novel graphene-based nano-devices that involve sliding electrical contact interface, especially those designed for operation across a wide range of ambient humidity and temperature conditions.