Mn<sub>1.56</sub>Co<sub>0.96</sub>Ni<sub>0.48</sub>O<sub>4</sub> (MCN) thin films with 2 μm thickness were deposited on amorphous Al<sub>2</sub>O<sub>3</sub> substrates by Radio Frequency magnetron sputtering at 450℃, films were annealed at 450℃, 600℃ and 750℃ separately. XRD test showed that MCN thin films deposited at 450℃ possess preferential orientation (400). The variable temperature resistivity test revealed the resistivity of MCN films decreases with the annealed temperature increases. Aging testing showed that films grown at 450℃ and annealed at the same temperature had moderate aging coefficient, meanwhile, the films exhibited favorable noise performance. This paper reports a method to prepare MCN thin films with moderate resistivity, favorable aging and noise characteristics at low temperature(450℃), which is expected to be integrated with the silicon process and has great significance for developing MCN thin film linear or focal plane devices.
A thermal sensitive infrared and THz detector was fabricated by a double layered Mn-Co-Ni-O/Mn-Co-Ni-Cu-O films. The Mn-Co-Ni-O material, as one type of transition metal oxides, has long been used as a candidate for thermal sensors or infrared detectors. The resistivity of a most important Mn-Co-Ni-O thin film, Mn<sub>1</sub>. <sub>96</sub>Co<sub>0.96</sub>Ni<sub>0.48</sub>O<sub>4</sub>(MCN) , is about 200 Ω·cm at room temperature, which ranges about 2 orders larger than that of VOx detectors. Therefore, the thickness of a typical squared Mn-Co-Ni-O IR detector should be about 10 μm, which is too large for focal plane arrays applications. To reduce the resistivity of Mn-Co-Ni-O thin film, 1/6 of Co element was replaced by Cu. Meanwhile, a cover layer of MCN film was deposited onto the Mn-Co-Ni-Cu-O film to improve the long term stability. The detector fabricated by the double layered Mn-Co-Ni-O/Mn-Co-Ni-Cu-O films showed large response to blackbody and 170 GHz radiation. The NEP of the detector was estimated to be the order of 10<sup>-8</sup> W/Hz<sup>0. 5</sup>. By applying thermal isolation structure and additional absorption materials, the detection performance can be largely improved by 1-2 orders according to numerical estimation. The double layered Mn-Co-Ni-O film detector shows great potentials in applications in large scale IR detection arrays, and broad-band imaging.
Mn-Co-Ni-O (MCNO) flexible thermistors are fabricated on polyethylene terephthalate or polyimide sheets by RF magnetron sputtering method at room temperature. The whole fabricating processes is completed at room temperature. The temperature coefficient of resistance (TCR) is -3.1% and resistivity as low as 110Ωcm at 295K. The bendingstraightening cycle test indicates the flexible MCNO sheet is stable. The temperature sensing test shows the thermistors respond to temperature change rapidly and sensitively. Due to the heat-treat free process, high TCR and moderate resistivity features, the technique we provide here allows a convenient and low cost industrial manufacture of high performance flexible thermistors and wide band infrared detectors.
Mn<sub>1.56</sub>Co<sub>0.96</sub>Ni<sub>0.48</sub>O<sub>4</sub> (MCN) films with different layers have been prepared on Al<sub>2</sub>O<sub>3</sub> substrate by chemical solution deposition method. The microstructures, optical and electrical properties of the films are investigated. X-ray diffraction and microstructure analyses show good crystallization and both the crystalline quality and the grain size are improved with the increasing thickness of the films. Mid-infrared optical properties of MCN films have been investigated using transmission spectra. The results show the red shift of absorption with the increasing film thickness and the energy gap <i>E</i><sub>g</sub> decrease from 0.6422 eV to 0.6354 eV. All the MCN films show an exponential decrease in the resistivity with increasing temperature within the measured range. The temperature dependence resistivity can be described by the small polarons hopping model. Using this model, the characteristic temperature <i>T</i><sub>0</sub> and activation energy <i>E</i> of the MCN films were derived. With the film thickness increase, the <i>T</i><sub>0</sub> and <i>E</i> of the MCN films increase. The calculated room temperature coefficient of resistance (TCR) of MCN film with 100 layers is -3.5% K<sup>-1</sup>. The MCN films showed appropriate resistance and high value of TCR, these advantages make them very preponderant for thermal sensors.
Mn-Co-Ni-O spinel oxide materials, with the prototype of AB<sub>2</sub>O<sub>4</sub>, are excelled in uncooled thermal sensing and infrared detection due to its high absolute NTC value and moderate resistivity at room temperature. In this work, Mn<sub>1.56</sub>Co<sub>0.96</sub>Ni<sub>0.48</sub>O<sub>4</sub> film (MCN-CSD) and Mn<sub>1.40</sub>Co<sub>1.00</sub>Ni<sub>0.60</sub>O<sub>4</sub> (MCN-RF) film are fabricated on amorphous sapphire substrate with chemical solution method (CSD) and radio frequency deposition method (RF), respectively. Morphological characteristics are revealed by SEM graphs. And the result shows that MCN films acquire better crystalline properties and compactness than MCN bulk materials. To verify the excellent features for infrared detection, detectors sized 1mm<sup>2</sup> × 0.17 μm and 1 mm<sup>2</sup> × 0.33 μm are fabricated based on MCN-RF and MCN-CSD films, respectively. The excess noise at 11 Hz for each detector has been tested and the Hooge's parameters have been calculated. The MCN films obtained by RF deposition and CSD method both show γ/n value of about 2×10<sup>-21</sup> cm<sup>3</sup>, an order lower than bulk MCN and amorphous silicon, which indicates great potentials in integrated infrared detection.
Mn-Co-Ni-O bolometer with spinel structure has been extensively studied as a low resistivity and high sensitivity negative temperature coefficient material for decades. In this paper, the fabrication process and the performance of uncooled infrared bolometer based on Mn<sub>1.56</sub>Co<sub>0.96</sub>Ni<sub>0.48</sub>O<sub>4</sub> (MCNO) thin films grown on Al<sub>2</sub>O<sub>3</sub> substrate by chemical solution deposition were investigated. The MCNO bolometer sized 300×160 μm<sup>2</sup> were fabricated by photolithography process followed by wet etching, and the temperature coefficient of resistance reaches -3.81 %K<sup>-1</sup> @296 K. Relatively low excess noise was achieved due to the good quality of fabrication process, and the normalized noise power γ/n was found to be 1.8×10<sup>-21</sup> cm<sup>3</sup> at 296 K. Through black coating the performances for MCNO bolometer, operating at room temperature, are greatly improved and exhibit responsivity of over 354 V/W, detectivity of approximated 4.5×10<sup>7</sup> cmHz<sup>1/2</sup>/W@10Hz at ±16 V, and the thermal time constant of about 18 ms. These experiment results indicate that the infrared detection ability of MCNO thin film bolometer is significantly enhanced comparing with bulk devices.
Mn<sub>1.56</sub>Co<sub>0.96</sub>Ni<sub>0.48</sub>O<sub>4</sub> films with spinel structure for infrared detection are prepared on Al2O<sub>3</sub> substrate by chemical
solution deposition method. The resistance vs temperature (R-T) characteristics at 130~304 K temperature range and
infrared transmission spectrum (1-10 μm) are measured and temperature coefficients of resistance (TCR) are calculated.
The conduction process can be explained well by hopping conduction. At low temperature nearest neighbor hopping
(NNH) mechanism fits the data well, while at high temperature, variable range hopping (VRH) mechanism dominates
the system, and this transition temperature is at about 200 K. The value of TCR is about -3.73% K<sup>-1</sup> at 300 K.
Mn<sub>1.56</sub>Co<sub>0.96</sub>Ni<sub>0.48</sub>O<sub>4</sub> films exhibit a strong absorption around 2μm which is considered to be corresponding to the gap of
energy bands showed by infrared transmission spectrum. The band gap obtained from the transmission spectrum data
using the Tauc's law is ~0.567 eV.