Development of femtosecond time-resolved scanning tunneling microscopy for nanoscale science and technology

'Smaller' and 'faster' are the key words in the progress of current nanoscience and technology. Thus, a method of exploring the ultrafast transient dynamics of the local quantum functions in organized small structures is eagerly desired. Ultrashort optical pulse technology has allowed us to observe transient phenomena in the femtosecond range, which, however, has the drawback of a relatively low spatial resolution due to the electromagnetic wavelength used. In contrast, scanning tunneling microscopy and its related techniques, although having a time resolution limited by the circuit bandwidth (similar to 100 kHz), enable us to observe spatial dynamics at the atomic level in real space. Our purpose is to combine these two techniques to achieve a new technology which will advance the pursuit of future nanoscale scientific research in terms of the ultimate temporal and spatial resolutions. We proposed a promising new design for achieving ultimate spatial and temporal resolution, by combining a short-pulse laser and STM. Using this method, time-resolved tunneling current measurement in the subpicosecond range was successfully demonstrated, this is shaken-pulse-pair-excited STM (SPPX-STM) satisfies the requirements for exploring the ultrafast dynamics of the local quantum functions occurring in organized small structures. We hope this new technology will promote the development of future research on the nanoscale. (c) 2005 Elsevier Ltd. All rights reserved.