Vol.:(0123456789) 1 3 Journal of Materials Science: Materials in Electronics https://doi.org/10.1007/s10854-020-03223-y Efect of growth and electrical properties of TiO x flms on microbolometer design Isha Yadav 1,2  · Surbhi Jain 3  · S. S. Lamba 1  · Monika Tomar 3  · Sudha Gupta 1  · Vinay Gupta 3  · K. K. Jain 1  · Shankar Dutta 1  · Ratnamala Chatterjee 2 Received: 7 December 2019 / Accepted: 7 March 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020 Abstract This paper presents the feasibility of non-stoichiometric TiO x thin flms as an active material for bolometer application. The TiO x flms have been deposited on glass substrate by DC sputtering with oxygen fow rate of 0.1–0.7 sccm at room temperature and their electrical properties have been studied. The TiO x flms were found to be amorphous with dense and smooth surface morphology. The thickness of the flms was found to decrease from 150 to 30 nm with an increase in oxygen fow rate. The TiO x flm corresponding to 0.7 sccm showed maximum temperature coefcient of resistivity of 0.72%/°C. Performance of TiO x -based bolometer pixel (pitch: 56 μm) is simulated using the electrical characteristics of the deposited flms. The TiO x flm corresponding to the 0.7 sccm O 2 fow rate displayed thermal conductance of 2.95 × 10 –7  W/K along with a maximum Figure of Merit of 2.45 × 10 6 and a time constant of 8.2 ms. The Noise equivalent temperature diference of the bolometer structure is estimated (~ 107 mK). 1 Introduction Infrared (IR) imaging using uncooled microbolometer detec- tors has drawn a lot of attention recently due to low cost coupled with high performance. These are being employed in several civilian and military applications, namely, auto- mobile and aircraft safety; consumer electronics; medical diagnosis; surveillance and manufacturing quality control etc. [1, 2]. Uncooled microbolometers operate at room tem- perature and do not require cryogenic cooling as compared to the photon detectors [3] based on HgCdTe and InSb mate- rials. Even though cryogenic cooled photon detector exhibit high detectivity, quantum efciency, and fast response [4], the microbolometer detectors ofer advantages in terms of compactness, ruggedness, size, weight, and cost [5]. With the advent of MEMS technology, large focal plane array of microbolometer pixels for IR imaging are possible to be realized [6]. A MEMS bolometer sensor pixel comprises of a stack of an IR-absorbing layer (which absorbs the incoming heat fux and raises its temperature) and a thermometer layer (to sense the minute increase in temperature due to the absorption of incoming IR) having high temperature coef- fcient of resistivity (TCR). The sensor pixels are fabricated monolithically on top of the pre-fabricated ROIC (Readout integrated circuit) substrate. The ROIC convert the change in pixel resistance into an electrical signal. Sensitivity of IR microbolometer pixels can be augmented by choosing appropriate IR-absorbing layer and thermometer layer [3, 4]. Researchers are using diferent metals, semiconductors, as well as their oxides having high TCR as thermometer layer e.g., Ti (0.3–0.35%/K) [6–9]; Pt (0.12–0.14%/K) [10]; a-Si (3–4%/K) [11]; Si–Ge (1%/K) [12]; vanadium oxide (2%/K) [13–17]; Mn–Co–Ni–O [18]; Nd 0.5 La 0.2 Sr 0.3 MnO 3 : Ag 2 O manganites [19] etc. Among these, vanadium oxide (VO x ) and a-Si are being widely utilized. However, the non- compatibility with CMOS fabrication technology and spa- tial noise in VO x [14, 15] and high 1/f noise in a-Si make the design of bolometer quite complicated [20, 21]. As an alternative to these two materials, diferent materials have been tried as thermometer material of bolometer structure, like, boron-doped mixed-phase silicon [22]; NiO [ 23]; * Shankar Dutta shankardutta77@gmail.com 1 Solid State Physics Laboratory, DRDO, Lucknow Road, Timarpur, Delhi 110054, India 2 Department of Physics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India 3 Department of Physics and Astrophysics, University of Delhi, Delhi 110007, India