We observed scanning tunneling microscope light emission (STM-LE) induced by a tunneling current at the gap between an Ag tip and a VO2 thin film, in parallel to scanning tunneling spectroscopy (STS) profiles. The 34 nm thick VO2 film grown on a rutile TiO2 (0 0 1) substrate consisted of both rutile (R)- and monoclinic (M)-structure phases of a few 10 nm-sized domains at room temperature. We found that STM-LE with a certain photon energy of 2.0 eV occurs selectively from R-phase domains of VO2, while no STM-LE was observed from M-phase. The mechanism of STM-LE from R-phase VO2 was determined to be an interband transition process rather than inverse photoemission or inelastic tunneling processes.
We
have investigated the fabrication of a single silver nanoparticle
(AgNP) on Si(111) at room temperature using scanning tunneling microscopy
(STM), and the luminescence of individual AgNP has been studied by
means of STM light emission (STM-LE) spectroscopy. Using the field
evaporation method, we succeeded in creating two types of nanostructures,
i.e., AgNP and the nanohole formed by the elimination of Si atoms,
on the Si substrate. It was found that two different nanostructures
can be created selectively by using the appropriate electric field.
STM-LE spectra of AgNP and the Si substrate exhibit the broad peak
appearing in the visible light region. The peak intensity increases
as increasing the AgNP size, accompanying a slight shift of the peak
position. Furthermore, the theoretical calculation based on the finite-difference
time-domain (FDTD) method has been used to get an insight into the
STM-LE from a single AgNP on the Si substrate.
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