Journal of Surface Engineered Materials and Advanced Technology, 2013, 3, 235-241 http://dx.doi.org/10.4236/jsemat.2013.33031 Published Online July 2013 (http://www.scirp.org/journal/jsemat) 235 Thin Film Deposition by Langmuir Blodgett Technique for Gas Sensing Applications Sanit Malik * , Chandra Charu Tripathi Department of Electronics & Communication Engineering, University Institute of Engineering & Technology (UIET), Kurukshetra University, Thanesar, India. Email: * maliksanit7@gmail.com Received May 10 th , 2013; revised June 11 th , 2013; accepted July 1 st , 2013 Copyright © 2013 Sanit Malik, Chandra Charu Tripathi. This is an open access article distributed under the Creative Commons Attribu- tion License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ABSTRACT There are various technologies like CVD. Radio Frequency sputtering, spin coating etc. present for thin film deposition for various applications and for gas sensors. In this review, special attention is focused on the thin film deposition for gas sensing applications by using Langmuir Blodgett method. Langmuir Blodgett method also discussed briefly. Modi- fied technique of Langmuir-Blodgett like Langmuir Schaefer method is discussed and various examples of Langmuir Blodgett techniques for gas sensing for space applications are included. Future prospects of gas sensing thin film depo- sition by Langmuir Blodgett technique are explained. Keywords: Thin Films; LB Method; Gas Sensor; Molecular Electronics; Nanostructures 1. Introduction Molecular electronics emerges as an important technol- ogy for the 21st century. The electronics industries are consuming organic materials in LCD, xerography, acous- tic transducer & in various sensors etc. Various efforts have been made towards the formation of nanostructure materials like nanorods, nanotubes and various nanopar- ticles. So by using LB method, new materials with im- proved properties can be prepared. LB method is used to obtain high quality films. LB method allows changing various parameters of the thin film like molecules nature, deposition pressure, and composition of sub phase and counter ions [1]. LB method provides the control over the thickness of the film as in this method a single layer of molecules is formed on the liquid (water) surface and then this layer is transferred to the substrates. So by re- peating this many times thin layers can be deposited on the substrates with controlled molecular thickness. As various gas sensors also use thin films for the sensing purpose so as to improve their parameters like sensitivity and selectivity it is required to obtain thin films of gas sensing materials. So control of thickness of film is achieved by LB method. The defect free films can be obtained by some changes in LB method [1]. By using LB method a thin layer of nanometer scale can be depos- ited on almost any kind of solid substrate. 2. LB Technique To understand the Langmuir Blodgett technique one should know some basics about the LB thin film deposi- tion process like surface tension, surfactants, insoluble monolayer’s, surface pressure, the Langmuir balance, surface pressure area isotherm etc. [2]. There is an attrac- tive force present between the molecules of a liquid which is known as cohesion it depends on the properties of substance. Inside the liquid the molecules are attracted towards each other so that the balance is maintained in all directions but on air/water interface molecule have more attraction towards the liquid than the air [3,4]. The polar liquids have high surface tension. To lower the surface tension the force of attraction should be de- creased by any means like by using contaminants. The illustration of the molecules interaction is shown in Fig- ure 1. As for LB method the material to be deposited on the substrate should be insoluble in water. There are mainly two types of molecules i.e. hydro- phobic (water insoluble) and hydrophilic (water soluble). The hydrophobic part mainly contains hydrocarbon chains and the polar groups (OH − , etc.) are pre- 3 NH  sent in the hydrophobic part [5]. Figure 2 shows the components of an ampiphile and orientation of an am- phiphilic adopted at interface. So the surface tension of * Corresponding author. Copyright © 2013 SciRes. JSEMAT