A thin film (thickness: 1.5 nm) of tetracyanoquinodimethane (TCNQ), a well-known electron acceptor, was fabricated on p-Si and n-Si using a spin casting method. The junction properties of these systems were investigated using scanning tunneling spectroscopy (STS). IN curves of the two systems showed rectifying properties with different polarity. It can provide a new technology to fabricate molecular-level rectifier if nanolithography is accomplished on these systems.