Identification of surface adsorbates by scanning tunneling microscope light emission spectra

摘要

In order to demonstrate that surface adsorbates can be identified by STM light emission spectra, we have measured the STM light emission spectra of various combinations of adsorbates and substrates. We presented the spectra of Cu(110)-0 and Ni(110)-H. The adsorbate specific spectra have been found for both systems. When the tip is located over the O atom adsorbed on the Cu(110) surface, the three additional components due to the electronic transitions localized at the O site is superposed on the STM light emission spectra. Thus we can identify the O atom from the spectra. In the case of Ni(110)-H system, the vibrational energy of the H atom is determined from the spectra. Consequently, we can identify the H atom from the spectra. As mentioned in the introduction, surface vibrational energies are specific to each adsorbate. Hence classical surface vibrational spectroscopic methods such as EELS and infrared absorption spectroscopy are conveniently used for identification of surface adsorbates under macroscopic spatial resolution. The result for Ni(110)-H demonstrates that the vibrational energies of surface adsorbates can be determined by measuring the STM light emission spectra with the benefit of atomic spatial resolution. In this manner the STM light emission spectroscopy is a very unique and valuable tool for identification of surface adsorbates with atomic spatial resolution.