Short Communication Influence of spin coating rate on the thickness, surface modification and optical properties of water dispersed PPy composite thin films P. Jayamurugan a , V. Ponnuswamy b,n , Y.V. Subba Rao c , S. Ashokan b , S. Meenakshisundar d a Department of Physics, Adhiyamaan College of Engineering, Hosur 635109, Tamil Nadu, India b Department of Physics, Sri Ramakrishna Mission Vidyalaya College of Arts and Science, Coimbatore 641020, Tamil nadu, India c Department of Physics, Birla Institute of Technology and Science (BITS) - Pilani, Hyderabad, Campus, Jawahar Nagar, Shameerpet Mandal, Hyderabad 500078, Telangana, India d Post Graduate and Research Department of Physics, Sri Paramakalyani College, Alwarkurichi, 627412 Tirunelveli, Tamil Nadu, India article info Available online 26 May 2015 Keywords: Effect of spin rates Atomic force microscopy Photoilluminiscence Thickness Transmittance abstract Water dispersed polypyrrole was chemically synthesized with Dodecylbenzene sulfonic acid (DBSA) as dopant and Poly (4-styrenesulfonic acid (PSS) as co-dopant. The 10 wt% of PSS doped polypyrrole composite shows higher processability. The prepared composites aqueous solution was deposited to get thin films by spin coating technique at various spin rates of 1000 rpm, 2000 rpm and 3000 rpm. The paper reports on effect of spin coating rate, thickness, surface roughness, and photoluminescence of water dispersed DBSA / PSS /PPY composite thin films. The transmittance is found to be decreased with increasing spin rates. Surface roughness of the films were analyzed by atomic force microscopy. The Root Mean Square (RMS) and Roughness (R a ) values were found as (22.5 nm, 89 nm), (135 nm and 18 nm), and (70 nm and 113 nm) values. The super hydrophilic nature of the composite films was studied by water contact angle measurements. The contact angle values were found to be 8.61, 9.41 and 101 for different spin rates. Photoluminescence (PL) of DBSA/PSS/PPY composite films reveals the emission with high intensity at high spin rates. Thickness of the composite films was found as 378 nm, 333 nm and 304 nm at 1000 rpm, 2000 rpm and 3000 rpm. & 2015 Elsevier Ltd. All rights reserved. 1. Introduction Polypyrrole(PPY) has high conductivity and good environ- mental stability, which are favorable for various applications such as metallization of dielectrics [1], batteries [2], antistatic coatings [3], shielding for electromagnetic interferences [4], sensors [5], actuators [6], and micro actuators [7]. However, a major limitation in practical application of PPY stems from the lack of solubility in common solvents. PPY becomes soluble when it is dissolved in organic solvents in the presence of surfactants, such as dodecylbenzenesulfonic acid, camphor- sulfonic acid and sodium dodecyl sulfate [8,9]. However, PPY shows poor solubility in protic organic solvents. Compared to PPY soluble in organic solvents, water-soluble or dispersed PPY is more favorable in many respects, for example, an environmentally benign route for processing and a control- led doping with various water-soluble polymer or molecular dopants. One of the most successful approaches is to add polyelec- trolytes as supporting substrates during the polymerization technique. To date, poly (sodium 4-styrene sulfonate) (PSS) is Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/mssp Materials Science in Semiconductor Processing http://dx.doi.org/10.1016/j.mssp.2015.05.014 1369-8001/& 2015 Elsevier Ltd. All rights reserved. n Corresponding author. Tel.: þ91 4222 692 461; fax: þ91 4222 693 812. E-mail address: muruganjaya85@gmail.com (V. Ponnuswamy). Materials Science in Semiconductor Processing 39 (2015) 205–210