Subject: Applied Physics 2

Topic: Nano science And Nanotechnology

Difficulty: Medium

Top down: - In this bulk material is reduced in size to nano scale pattern. Successive slicing of bulk material is done to get particles of nano-size. But this approach is most likely to introduce internal stress, surface defects and contamination. Such imperfections may affect physical properties and surface chemistry of nano materials. Despite these limitations, this method is widely used for its simplicity and relative easy. Bottom up :- The bottom up techniques builds or grow larger structures atom by atom or molecule by molecule. I,e it collects, unites and fashion individuals atoms and molecules to construct a nano materials. Colloidal dispersion, nano-lithography etc. are bottom up approach. By this approach, we can obtain structure with fewer defects and more homogeneous chemical composition.