Vol.:(0123456789) 1 3 Applied Physics A (2018) 124:508 https://doi.org/10.1007/s00339-018-1924-7 Organic humidity sensing ilm optimization by embedding inorganic nano-anatase TiO 2 powder Mohamad Izzat Azmer 1  · Qayyum Zafar 2  · Karwan Wasman Qadir 3,4  · Khaulah Sulaiman 1  · Tahani M. Bawazeer 5  · Mohammad S. Alsoui 6 Received: 20 December 2017 / Accepted: 18 June 2018 © Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract In this work, surface-type humidity sensors with P3HT (organic) and P3HT–TiO 2 (organic–inorganic hybrid) active layers have been fabricated. The surface morphology of the humidity active ilms has been studied by atomic force microscopy, whereas their crystalline structure has been studied by X-ray difraction. We have aimed at improving the sensing parameters of P3HT-based humidity sensor, by embedding nano-anatase TiO 2 powder in pristine organic P3HT moiety. The capaci- tance versus relative humidity (%RH) response curves of the organic and hybrid humidity sensors have been examined in 30–98%RH range (dark ambient condition, room temperature). In general, an increase in capacitance has been observed in both sensors with the increment in RH level. The observed response of both humidity sensors is believed to be associated with polarization change due to the adsorption of water molecules and transfer of charge carriers due to the formation of charge transfer complexes. The hybrid-based humidity sensor has shown signiicantly improved humidity-sensing parameters, i.e., ivefold higher sensitivity, with hysteresis reduced to one-third as compared to that of pristine organic humidity sensor. A relatively faster response and recovery time has also been obtained by the hybrid sample. 1 Introduction Monitoring ambient humidity is a necessary activity in agri- culture, museums, weather forecast, food stocking, electronic and pharmaceutical industry [1, 2]. To determine humid- ity, various sensing transduction mechanisms have been exploited extensively which rely on impedance, resistance, current, capacitance, luorescence and frequency variation with change in humidity [3]. However, the capacitive-type sensing mechanism ofers potential advantages such as low power consumption, linearity in response and condensation tolerance [4]. In general, the change in capacitance of the humidity sensor follows a direct exponential association as a function of increment in humidity levels [5, 6]. Humidity sensitivity, response-recovery time and hysteresis are the key sensing parameters; here in this study, we aim at optimizing these aforementioned sensing parameters for the develop- ment of eicient capacitive type humidity sensor. Indeed, the sensing parameters of capacitive-type humid- ity sensors are primarily determined by the hygroscopic material used as humidity active thin ilm [7]. Traditional thick and thin ilm inorganic semiconductors based sensors have an unfavourable cost structure associated with their time-consuming and energy-intensive thin-ilm deposition techniques [2]. The continued high interest in the organic semiconductors based humidity sensors originates from the fact that they are solution processable and can thus can be processed via low thermal budget and facile fabrication techniques [8]. However, presently, to further improve the sensing parameters, organic–inorganic hybrid humidity sensing ilms are being utilized with the intent of synergistic * Qayyum Zafar qayyumzafar@gmail.com 1 Department of Physics, Low Dimensional Materials Research Centre, University of Malaya, 50603 Kuala Lumpur, Malaysia 2 Department of Physics, Government College University (GCU), Lahore 54000, Pakistan 3 Department of Physics, College of Education, Salahaddin University-Hawler, Erbil, Kurdistan Region 44001, Iraq 4 Physics Education Department, Faculty of Education, Ishik University, Erbil 44001, Iraq 5 Department of Chemistry, Faulty of Applied Science, Umm Al-Qura University, Makkah, Saudi Arabia 6 Mechanical Engineering Department, College of Engineering and Islamic Architecture, Umm Al-Qura University, Makkah, Saudi Arabia