Synthesis and electrical properties of a single walled carbon nanotube–borosilicate glass composite A. Ghosh a , S. Ghosh a , S. Das a , P.K. Das b , D.D. Majumder c , R. Banerjee b, * a Department of Physics, Jadavpur University, Jadavpur, Kolkata 700 032, India b Central Glass and Ceramic Research Institute, Jadavpur, Kolkata 700 032, India c Electronics and Computer Science Unit, Indian Statistical Institute, Kolkata 700 036, India article info Article history: Received 13 May 2010 In final form 20 July 2010 Available online 23 July 2010 abstract Single walled carbon nanotube–borosilicate glass composite has been fabricated in a controlled atmo- sphere furnace by a melt-quench technique. Current–voltage characteristics were analyzed at room tem- perature and found to be non-ohmic in behavior. The temperature dependence of the current–voltage characteristics was ascertained and it was observed that the electrical conductivity of the composite increased substantially with temperature. Analysis by scanning and transmission electron microscopy clearly demonstrates that the carbon nanotubes are randomly distributed in the form of bundles through- out the glass. The charge conduction mechanism of the composite was found to be well explainable by the fluctuation induced tunneling (FIT) model. Ó 2010 Elsevier B.V. All rights reserved. 1. Introduction The carbon nanotube [1] has a structure like one or more graph- ene sheets being rolled up into a flawless cylindrical shape. The tube exhibits semi-conducting or metallic property based on its diameter and helicity [2–4]. Since its discovery, carbon nanotubes has emerged as a potential material with high tensile strength, very high thermal conductivity and extraordinary field emission properties. Its unique electrical, mechanical and optical properties [5–8] have led to potentially useful applications in electronics, and materials science. One of the applications was the development of new functionalized carbon nanotube incorporated composites exhibiting interesting properties [9–19]. de Heer et al. [20] was first to produce ordered structure material by depositing a film of carbon nanotube on a plastic surface aligned perpendicular or parallel to the surface. Their study was mainly focused on optical and electronic properties of carbon nanotube on this structure. Ajayan et al. was the first to report polymer composite [21] with carbon nanotubes. Subsequently they undertook extensive struc- ture property correlation to analyze the properties of the material. Nevertheless it could be interesting to introduce carbon nanotubes in glass materials by melt-quench technique. The primary interest on this novel fabrication was to translate a hardcore insulator into a conducting composite by incorporating single walled carbon nanotube inside the glass host in a well dispersed manner so as to study the possibility of its applications for a conductor-insulator interface device. Current (I)–voltage (V) characteristics of the com- posite was measured at room temperature and found to be non- ohmic in behavior. The field dependent conductivity was found to increase up to six orders than that of the glass even at minimum applied electric field. This may be due to the formation of conduc- tive paths inside the composite. Moreover, I–V characteristics were studied at different temperature to ascertain the effect of temper- ature on the electrical conductivity of the composite. The result shows that the conductivity of the composite increases with tem- perature similar to that of a semi-conducting material. It was fur- ther observed that the level of nonlinearity of I–V profile decreases with the increase in temperature. Thus the above phenomena can be attributed to be the charge transport mechanism within the composite. The mechanism was analyzed using fluctuation in- duced tunneling (FIT) model and found to be in agreement with the phenomena. 2. Experimental Single walled carbon nanotube having 60% purity was pur- chased from Arry, Germany having OD: 1–2 nm; length: 5– 20 lm; special surface area: >400 m 2 /g and thermal conductivity: 4000 W/m K. Approximately 0.3–0.6 g of single walled carbon nanotube is taken in a mixture of toluene and aniline [22]. The mixture was heated till the solution becomes dark brown. Borosil- icate glasses with the following chemical composition: SiO 2 -69.2%, B 2 O 3 -10.0%, BaO-3%, K 2 O-8.4%, Na 2 O-8.4%, CeO 2 -0.53% was fritted into very small pieces of different shapes and sizes. The glass tran- sition temperature (T g ) and the softening point was found to be 567 and 717 °C respectively. Some of the fritted glass of weight 2.675 g was taken in a crucible and well mixed with a definite 0009-2614/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.cplett.2010.07.069 * Corresponding author. Fax: +91 33 24730957. E-mail address: rajatbanerjee@hotmail.com (R. Banerjee). Chemical Physics Letters 496 (2010) 321–325 Contents lists available at ScienceDirect Chemical Physics Letters journal homepage: www.elsevier.com/locate/cplett