Effect of terbium doping on structural, optical and gas sensing properties of In 2 O 3 nanoparticles Kanica Anand, Jasmeet Kaur, Ravi Chand Singh, Rengasamy Thangaraj n Department of Physics, Guru Nanak Dev University, Amritsar 143005 India article info Keywords: Rare earth Doping In 2 O 3 Sensor Response abstract In this work, the effect of terbium (Tb 3 þ ) as dopant on the structural, optical, electrical and gas sensing properties of In 2 O 3 (indium oxide) nanoparticles has been discussed. In 2 O 3 and Tb 3 þ -doped In 2 O 3 nanoparticles were synthesized by a facile and cost effective co-precipitation method. XRD analysis revealed the formation of bixbyite-type cubic phase for In 2 O 3 and Tb 3 þ -doped In 2 O 3 nanoparticles which was further supported by Raman studies. It was observed that the crystallite size of In 2 O 3 nanoparticles decreased, while structural disorder increased with increase in Tb 3 þ concentration. SEM micrographs showed that particles were spherical in shape and EDS corroborated the presence of Tb 3 þ in doped In 2 O 3 nanoparticles. A broadening and shifting of Raman peaks with increase in Tb 3 þ content was also observed. For gas sensing characteristics, the nanoparticles were applied as thick film onto the alumina substrate and tested at different operating temperatures for various volatile organic compounds (such as methanol, ethanol, acetone) and ammonia. The results indicated that the sensor based on 5%Tb 3 þ -doped In 2 O 3 nanoparticles presented much higher sensor response to 50ppm ethanol at 300 1C temperature than the pure In 2 O 3 sensor. The enhancement of the response may be attributed to high surface basicity, small size and large lattice distortion of doped In 2 O 3 sensor. & 2015 Published by Elsevier Ltd. 1. Introduction In recent years, semiconductor metal oxide nanostructures (SMO) such as ZnO, SnO 2 , In 2 O 3 have been extensively studied due to their novel properties at nano-level as compared to their bulk counterpart that make them suitable for applica- tions in various fields such as gas sensors, solar cell, flat panel display, optoelectronic devices, memory storage devices and so forth [1–3]. Among these SMOs, indium oxide, an intrinsically n-type semiconductor in non-stoichiometric form, has been in the eye of storm due to its exotic physical and chemical properties such as wide band gap (3.5–3.7 eV), high electrical conductivity, good chemical stability, strong interaction between certain poisonous gas and its surface, that make In 2 O 3 a promising candidate for gas sensor [4–7]. The working principle of these gas sensors is based on the change in the electrical resistance on exposure to gas due to the reaction between the test gas molecule and adsorbed oxygen species on the surface of metal oxide in the form of O 2 ,O  or O 2  depending upon operating temperature. The adsorbed oxygen molecule depletes electrons from the surface of metal oxide sensor, leading to an increase in the electrical resistance. Thereafter, the surface reactions between pre- adsorbed surface oxygen species and reducing test gases take 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.2015.05.042 1369-8001/& 2015 Published by Elsevier Ltd. n Corresponding author. E-mail addresses: kanica.anand@yahoo.com (K. Anand), jasmeet.dayal@gmail.com (J. Kaur), ravichand.singh@gmail.com (R.C. Singh), rthangaraj@rediffmail.com (R. Thangaraj). Materials Science in Semiconductor Processing 39 (2015) 476–483