Voltage-induced chemical contrast in scanning tunneling microscopy using tips chemically modified with hydrogen bond donors

► Scanning tunneling microscopy (STM) tips were modified with 4-mercaptobenzoic acid. ► In-situ voltage treatment induces chemical contrast in STM images. ► Chemical contrast is due to hydrogen bond between STM tip and the sample. ► Chemical contrast enhancement allows recognition of functional groups of sample. ► The effectiveness of inducing chemical contrast is discussed.