STM-based Charge-Injection Spectroscopy

We have developed a new method for characterizing the electronic properties of organic thin films and interfaces for electronic device applications. In this scanning tunneling microscope (STM)-based technique, distance versus potential curves are collected at constant tunneling current. Here the STM feedback mechanism causes the tip to penetrate the organic material, allowing the injection barriers at interfaces and charge-transport properties of the organic materials to be determined with nanometer spatial resolution. Moreover, the technique is applicable to organic single and multilayer thin-film samples. Results obtained on thin films of tris(8- hydroxiquinolato)aluminum deposited on Au(111) and Ag(111), and polymorphic copper phthalocyanine deposited on Au(111) substrates will be presented.