Electro-thermal and optical characterization of an uncooled suspended bolometer based on an epitaxial La_0.7Sr_0.3MnO₃ film grown on CaTiO₃/Si

Abstract

The electro-thermal and optical properties of a bolometer based on an La 0.7 Sr 0.3 MnO 3 (LSMO) thin film with a detection area of 100 × 100µm 2 are presented. The LSMO thin film was epitaxially grown on CaTiO 3 /Si and patterned using a two-step etching process of ion-beam etching in argon and of reactive-ion etching in SF 6 , in order to etch LSMO/CaTiO 3 and Si, respectively. The voltage-current (V-I) characteristics of the bolometer were measured in vacuum from 240 to 415 K. From the V-I characteristics and a thermal model of the bolometer, the electrical responsivity was determined and compared to the optical responsivity measured with a laser diode at 635 nm. The noise equivalent power (NEP) as a function of frequency was measured by dividing the spectral noise power density by the optical responsivity. At 300 K and a bias current of 80 µA, the NEP was 2.3×10-11 W•Hz-1/2 in the 20-200 Hz modulation frequency range and the response time was 1.3 ms. The obtained NEP value without any absorbing layer or antennas, combined with the low value of the response time, are a very promising step towards the use of such LSMO-based bolometers for IR or THz detection.

Roadmap of Terahertz Imaging 2021

“…They were realized in silicon wafers, where the readout integrated circuits had been prefabricated to employ VOx film as a bolometer active layer, whose changes in the resistance can be detected and converted to the output voltage or current signals [194]. Other routes in microbolometers evolution are related to search of new materials, for instance, La 0.7 Sr 0.3 Mn O3 thin films as active device layers [195], silicon-on-insulator (SOI), CMOS technology employing different Si-based temperature sensors, such as metal-oxide-semiconductor field-effect transistor, pn-junction diode, and various resistors as possible antenna-coupled bolometers [196]. An interesting concept can be their confluence with metamaterials, e.g., metallic split-ring resonators, integrated into micro-bridge structures of THz microbolometer arrays to enhance the absorption of THz radiation in different materials, like thermal sensitive vanadium oxide film [197].…”

Integration of epitaxial La2/3Sr1/3MnO3 thin films on silicon-on-sapphire substrate for MEMS applications

“…Optimal 'Sr' doped manganite La 2/3 Sr 1/3 MnO 3 (LSMO) exhibiting a room-temperature ferromagnetic metal phase (Curie temperature, T c ~ 360 K) [1] is considered as a suitable candidate not only for spintronic devices but also bolometers and microelectromechanical systems (MEMS) [2][3][4][5]. LSMO thin films are also used as buffer layers for low field magnetic sensors, magnetic memory applications operating at room temperature [6][7][8].…”

Use of epitaxial PZT thin films for La2/3Sr1/3MnO3based MEMs devices on SrTiO3/Si

“…Micro-ElectroMechanical systems (MEMS) are micrometer devices with movable parts fabricated through microtechnology tools and are widely used in various sensors and actuators applications. La2/3Sr1/3MnO3 (LSMO) presents a ferromagnetic-to-paramagnetic transition at about 360 K that is accompanied by a metal-to-insulator transition above room temperature, which is very promising for uncooled sensors, such as anisotropic magnetoresistances [1] or infrared bolometers [2]. In addition, the high sensitivity of epitaxial oxides to strain, hence to mechanical effects, makes these materials promising and encourage us to investigate the potentialities of LSMO based MEMS resonators [3].…”