Hi,

I am Shirshendu Dey a third year PhD student, in Department of Physics, of University of Pune, working in the Scanning Probe Microscopy group with  Prof. C. V. Dharmadhikari. in the field of NANOTECHNOLOGY.

My research topic involves the study of optical properties of  nanostructures like quantum dots, nanotubes etc. Recently I am  involved in studying the electrical properties of nanostructures using in-house developed Conducting AFM.

Scanning tunneling microscopy  STM) is a powerful technique for viewing surfaces at the atomic level. Its development in 1981 earned its inventors, Gerd Binnig and Heinrich Rohrer (at IBM Zürich), the Nobel Prize in Physics in 1986. STM probes the density of states of a material using tunneling current. For STM, good resolution is considered to be 0.1 nm lateral resolution and 0.01 nm depth resolution. The STM can be mage of surface reconstruction on a clean Gold (Au(100)) surface, as visualized using scanning tunneling microscopy. The individual atoms composing the material are visible. Surface reconstruction causes the surface atoms to deviate from the bulk crystal structure, and arrange in columns several atoms wide with regularly-spaced pits between them.used not only in ultra high vacuum but also in air and various other liquid or gas ambients, and at temperatures ranging from near zero kelvin to a few hundred degrees Celsius.

The STM is based on the concept of quantum tunnelling. When a conducting tip is brought very near to a metallic or semiconducting surface, a bias between the two can allow electrons to tunnel through the vacuum between them. For low voltages, this tunneling current is a function of the local density of states (LDOS) at the Fermi level, E_f, of the sample. Variations in current as the probe passes over the surface are translated into an image. STM can be a challenging technique, as it requires extremely clean surfaces and sharp tips.