CONTROL OF APEX SHAPE OF THE FIBER PROBE EMPLOYED IN PHOTON SCANNING TUNNELING MICROSCOPE BY A MULTISTEP ETCHING METHOD

In this paper, we discuss about the control of the shape of the very a pex of a sharpened fiber probe used in photon scanning tunneling micro scope (PSTM) by means of a method based on selective chemical etching, Under ambient conditions, through a multistep etching method proposed here, fiber probes with a flattened apex having a diameter of around 15-20 nm could be produced with high reproducibility. It has also been discovered that, during the etching process, the shape of the apex of the probe takes a rounded or a flattened shape with respect to the et ching time in an almost cyclic fashion and such a phenomenon could hel p in understanding the mechanism of the etching process. These kind of probes with hat apex after metal coating are suitable for the fabrica tion of apertured probes used in PSTM and also for super tips which ha ve a promising future as nanosensors in the fields of biology and bioc hemistry.