Uncooled bolometer response of a low noise La2∕3Sr1∕3MnO3 thin film

Abstract

We report measurements of the optical responses of a La2/3Sr1/3MnO3 (LSMO) sample at a wavelength of 533 nm in the 300 -400 K range. The 200 nm thick film was grown by pulsed laser deposition on (100) SrTiO3 substrate and showed remarkably low noise. At 335 K the temperature coefficient of the resistance of a 100 µm wide 300 µm long LSMO line was 0.017 K -1 and the normalized Hooge parameter was 9×10 -30 m 3 , which is among the lowest reported values. We then measured an optical sensitivity at I = 5 mA of 10.4 V.W -1 and corresponding noise equivalent power (NEP) values of 8.1×10 -10 W.Hz -1/2 and 3.3×10 -10 W.Hz -1/2 at 30 Hz and above 1 kHz, respectively. Simple considerations on bias current conditions and thermal conductance G are finally given for further sensitivity improvements using LSMO films.The performances were indeed demonstrated on bulk substrates with G of 10 -3 W.K -1 . One could expect a NEP reduction by three orders of magnitude if a membrane-type geometry was used, which makes this LSMO device competitive against commercially available uncooled bolometers.Submitted to Appl. Phys. Lett. 1The remarkable electronic and magnetic properties of rare-earth manganite oxides have raised lot of interests for applications [1]. In addition to the widely studied magnetoresistive sensors and spin electronics, uncooled bolometers using the large resistance change at the metal-to-insulator transition are among the most promising. Indeed uncooled technologies open new opportunities for infrared detection for both military and commercial applications [2]. Actual materials used for the fabrication of uncooled resistive bolometers are amorphous semiconductors, polycrystalline SiGe, semiconducting YBa2Cu3O7 (YBCO), VO2 and VOx. Around 300 K they present typical maximum temperature coefficient of the resistance (TCR), defined as the relative resistance derivative (1/R)×(dR/dT), of 0.02 to 0.06 K -1 [3, 4], -0.007 K -1 [5], -0.029 K -1 [6], -0.017 K -1 [7, 8] and -0.033 K -1 [9], respectively.Rajeswari et al. [10] showed that the optical response of La0.67Ca0.33MnO3 was of thermal nature, but the maximum of the resistance derivative (corresponding to TCR = 0.079 K -1 ) was obtained at 260 K. Goyal et al. [11] mentioned the high TCR values of several compositions of manganites. The highest values (0.2 K -1 ) were obtained in Nd0.7Sr0.3MnO3 well below room temperature (235 K). Only La0.7Sr0.3MnO3 and La0.7Ba0.3MnO3 that showed TCR of 0.02 K -1 and 0.04 K -1 , respectively, were suitable for uncooled operation. Other manganite compositions such as La2/3(Ca,Pb)1/3MnO3 [12] and (La0.6Pr0.4)0.67Ca0.33MnO3 [13] even showed TCR as high as 0.1 K -1 at 300 K. However no noise data are available for the first material and preliminary measurements showing a high low frequency noise level are reported for the second one. In comparison TCR of La0.5Ba0.5MnO3 and La0.5Sr0.5MnO3 were lower (about 0.015-0.02 K -1 ) but with a much lower noise level at 30 Hz, which makes them potentially more suitable for uncooled bolometer fabricati...

Structural 1/f Noise and MOKE Characterization of Vicinal La0.7Sr0.3MnO3Thin Films

“…It is defined as the ratio of the voltage spectral noise density times sample volume over the square of the sample voltage at 1 Hz. Values in the 4 × 10 −29 −4 × 10 −28 m 3 range were found, which are promising results since they are comparable to the values measured in LSMO of the same thickness deposited on standard STO(001) [8]. Therefore, in addition to the uniaxial magnetic anisotropy observed in the 40 nm thick films deposited on the 10…”

“…the coercive field is the largest when the external field is along the step direction and vanishes when external field is perpendicular to the step direction. In the easy direction, the coercitive field was 11.6 Oe, which, is much higher than the one obtained on STO(001), which is 2.7 Oe in the [110] or [1][2][3][4][5][6][7][8][9][10] directions. At last Fig.…”

Optical and Electrical Characterizations of Uncooled Bolometers Based on LSMO Thin Films

“…Higher optical sensitivities can be reached by lowering the sample temperature and increasing the bias current, so that the maximum of dR/dT can be reached thanks to Joule effects. At room temperature, measurements presented in Figure 2a show that the maximum of sensitivity about 1000 V·W −1 is reached at a bias current of 187 µA compatible with the LSMO absorption (= 0.8) [4].…”

“…La0.7Sr0.3MnO3 (LSMO) is a very interesting material for the fabrication of infrared bolometers because of the large variation of its electrical resistance R with temperature T close to room temperature [2][3][4][5]. It has a large temperature coefficient of resistance, named TCR = 1/R × dR/dT, of about 0.02 K −1 in the 300-340 K range and it also shows a low noise level compared with other resistive materials such as semiconductors and other oxide materials [6][7][8].…”

Ultrafast Photoelectric Effect in Oxide Single Crystals and Films

“…[33][34][35][36] Technological interest has centered on solar cells, light-emitting diodes, and photoelectric detectors. [37,38] Previous researches showed that these materials represent good properties, such as ultrafast response, high-sensitivity, broad-spectrum and position-sensitivity, as optoelectronic device materials.…”