**2.4. Pulsed laser deposition (PLD)**

This technique is well known for its flexibility to grow variety of materials. Nanotree-like structures can be grown via this synthesis route without using any surfactant and prior treatment. Pressure treatment and laser ablation are used for preparation of hierarchical structures by this technique.

It is a top-down approach in which pulsed laser is used to decompose the precursor material and then these materials are deposited on substrates. By controlling the parameters like laser power, temperature, chamber geometry and pressure, one can grow structures of different morphologies from columnar structures to dense forest-like [39] structures. The porosity of structures is increased when grown at high pressure because of fast process. Also the surface area can be controlled by controlling inter columnar spacing and thickness. **Table 5** shows features of structures prepared via dot pattering technique.
