Contents lists available at ScienceDirect Materials Research Bulletin journal homepage: www.elsevier.com/locate/matresbu A multi-prong approach towards the development of high performance Temperature sensor using MWCNTs/Al 2 O 3 composite film Poonam Sehrawat, Abid, S.S. Islam ⁎ , Prabhash Mishra, Manika Khanuja Centre for Nanoscience and Nanotechnology, Jamia Millia Islamia (A Central University), New Delhi–110025, India ARTICLE INFO Keywords: A. Ceramics A. Composites A. Nanostructures B. Sol-gel chemistry D. Electrical properties ABSTRACT We report fabrication of high-performance temperature sensor from free-standing MWCNTs/Al 2 O 3 composite film where a multi-prong approach was undertaken to enhance sensor performance. Film thickness was varied until a threshold value was reached by playing surface-area to volume-ratio factor leading to enormous im- provements in crucial sensor parameters–temperature coefficient of resistance (TCR) and thermal hysteresis. Increased TCR resulted in high sensitivity, ultrafast response and negligible hysteresis loss. Besides, effect of carrier-drift transport under strong electron-phonon scattering is investigated by permutation of channel-length and external DC bias. Observed TCR value is -0.96%/°C for 16.53 μm thick film, at 2 V applied-bias voltage for 1 mm channel-length. Moreover, the sensor exhibited negligible hysteresis loss along-with response and recovery times of ∼40 s and ∼185 s respectively. Non-contact mode temperature measurements also demonstrated ex- cellent performance. Fabricated sensors exhibited good stability and negligible drift for six-months. These stu- dies are significant towards fabricating simple, highly-sensitive, economic heat sensor with high reproducibility. 1. Introduction Thermal management is crucial to almost all the modern-day in- dustries, be it pharmaceuticals, automobiles, food processing and packaging, etc., and it is imperative to all the thermal management systems. This has impelled an unprecedented focus on the materials having excellent electrical and thermal properties [1,2]. Various novel materials have been designed and tested for their electrical and thermal properties [3–8]. These include platinum, ceramics, polymers, carbon nanomaterials, etc. Most of these materials either have a short working range or the TCR value is very low [9–16] where the last factor (TCR) plays the key role on the qualitative performance of the sensor. Since its discovery, CNTs (carbon nanotubes) have been intensively investigated for their extraordinary transport and physical properties which stem from their novel structure [17–21]. Of particular sig- nificance in temperature sensing applications are their astounding electronic and thermal properties. Moreover, CNTs exhibit temperature dependent electrical conductivity, making them an excellent material for a temperature sensor [22–26]. CNTs have been found to exhibit thermal conductivities as high as 6600 W/mK for single-walled (SWCNTs) and 3000 W/mK for multi-walled (MWCNTs) CNTs [27,28]. Although individual nanotube based devices exhibit excellent properties [29,30], such devices are randomly fabricated; and for batch fabrication it is imperative to grow identical CNTs having same characteristics. Major obstacles to CNTs based microelectronics include absence of technology for mass production, circuit density, positioning of individual electrical contacts, sample purity, controlling the nano- tube purity, length, chirality, and to achieve proper alignment. De- pending upon its chirality, an as-prepared CNT can either be semi- conducting or metallic. One way to fabricate CNT based devices is to use random networks of CNTs. In this way, the resulting device benefits from statistical averaging of all the electrical differences, thereby al- lowing the fabrication of large-scale devices at wafer level [31–40]. CNTs thin-films not only exhibit combined properties of individual nanotubes but also the additional properties evolved due to tube–tube interactions. Layer-by-layer self-assembly to prepare multilayered films has been found to be an effective technique to develop thin films with variable thickness. SWCNTs films with varying thickness have been prepared via vacuum filtration to obtain a maximum TCR of -0.136%/ °C [41]. In another work, Cagatay et al. [42] have demonstrated TCR variation with film thickness of spray deposited CNTs films and ob- served a maximum value of -0.002954 °C -1 . Both of these techniques are simple and reproducible. However, the TCR values are quite low. Besides, CNTs based composite thin films have been demonstrated to exhibit high sensitivity along with fast response [43–47]. The compo- sites of CNTs have been reported with polymers, metals, and ceramics. The polymer composites can be employed only at ambient and mild temperatures owing to their low melting temperatures [48]. http://dx.doi.org/10.1016/j.materresbull.2017.10.045 Received 6 February 2017; Received in revised form 30 September 2017; Accepted 30 October 2017 ⁎ Corresponding author. E-mail address: sislam@jmi.ac.in (S.S. Islam). Materials Research Bulletin 99 (2018) 1–9 0025-5408/ © 2017 Elsevier Ltd. All rights reserved. MARK