Week 7 : Nanomaterials Fabrication Techniques & Clean Room Facility

Chapter#2 Nanostructures fabrication Techniques: Introduction

There are generally two approaches of fabricating nanomaterials.

  1. Top down approach
  2. Bottom up approach

Top-down approach: It uses larger materials to make nano structures through lithography, ball milling and laser ablation etc. Examples of Lithography or pattern transfer techniques are Optical, e-beam & nanoimprint lithography etc.

Bottom up approach: It uses self assembled properties, create larger units (nanoparticles) from individual molecules. Examples of bottom up approaches are  wet chemical methods e.g, Chemical reduction method, Co-precipitation method, Hydrothermal method etc.

Clean room facilities

The small geometrical nanoscale features on a microchip necessitates the use of clean room facilities during the critical fabrication steps. Each cubic meter of air in ordinary laboratories may contain more than 10 million particles with diameters larger than 500 nm. To avoid a huge flux of these ”large” particles down on the chips containing micro and nanostructures, micro and nanofabrication laboratories are placed in so-called clean rooms equipped with high-efficiency particulate air (HEPA) filtering system. Such systems can retain nearly all particles with diameters down to 300 nm. Clean rooms are classified according to the maximum number of particles per cubic foot larger than 500 nm. Moreover, all personnel in the clean room must be wearing a special suit covering the whole body to minimize the surprisingly huge emission of small particles from each person.     

 Bottom Up Approach

In this approach, different physical, chemical and and green methods are used to synthesize nano materials. Wet chemicals methods include chemical reduction, hydrothermal method etc.

Chemical reduction method for synthesis of nanoparticles

Main salt + Reducing agent     =   Nanoparticles + By products

                                                                                                                      

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