Rainer Köning1, Otto Jusko1, Ludger Koenders1, A. Schlachetzki2
1Laboratorium für Mikrostrukturmesssysteme, Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig, Germany
2Institut für Halbleitertechnik, Technische Universität Braunschweig, Hans-Sommer-Strasse 66, D-38106 Braunschweig, Germany
Tóm tắt
Scanning tunneling microscopes allow the formation of structures, by the application of voltage pulses between tip and sample whose dimensions are in the range of some nanometers. Systematic investigations have been carried out on the Si(111)-7×7 using W and Au tips in order to better understand the physics of the underlying deposition process. Therefore the voltage pulse, current, and z-piezo voltage were measured as a function of time. Above a threshold voltage, which depends on the pulse duration and the tunneling current, too, hills were created in the range between 5 and 25 nm. The surface structure was preserved up to the hills. Further, there is a linear dependence of the diameter on the pulse amplitude and pulse duration. A fit of the data gives a slope of (0.1±0.02) nm/s for tungsten tips and (0.45±0.14 nm/s) for gold tips, respectively. In addition, there is also a logarithmically dependence of the diameter upon the tunneling current for both tip materials. The results obtained are discussed with reference to the formation mechanisms published to date. None provide a satisfying explanation of our results.
