We report the deposition and characterization of 𝐴𝑙𝑥𝑁𝑦 thin films to use them as pyroelectric detector. 𝐴𝑙𝑥𝑁𝑦 thin films were deposited using a direct current (DC) magnetron sputtering from an Al target with varying concentrations of Ar:N2 at constant pressure and substrate temperature. The film thickness' were varied between 100-200 nm with varying atomic composition based on Ar:N2 during deposition. The nitrogen content in the films varied from 39.0% to 44.7% as found by energy dispersive spectroscopy (EDS). Each of the thin films was annealed at a different temperature between 400 to 800 °C with 100 °C increment in N2 environment and X-ray diffraction (XRD) was performed to analyze the annealed films crystallinity. From the XRD data and by using Scherrer equation, we found that for samples annealed at 600 °C for fifteen minutes has the grain size of 12.28 nm. Optical properties of the films were measured with varying wavelengths which include transmission, reflection, absorption, refraction coefficient, extinction coefficient and the optical bandgap. We also determined the electrical properties of thin films’ which include the pyroelectric coefficient, pyroelectric current, dielectric constant, and film permittivity between the temperature range 270 K to 310 K. As the temperature is increased, the pyroelectric coefficient also increased almost linearly. The pyroelectric coefficient of annealed 𝐴𝑙𝑥𝑁𝑦 films found to be varied between 4.86 × 10-5 C/m2K to 1.32 × 10-4 C/m2K. The optical transmittance through the as grown non-annealed thin films was found to be varied between 35 to 78%, while the reflectance was found to be below 25%. Because of low absorption in the thin films the extinction coefficient was found to be near zero. The refractive index was varied between 1.7 and 2.2 for the 𝐴𝑙𝑥𝑁𝑦 thin films. The optical bandgap was found to be 1.40 eV for non-annealed 𝐴𝑙𝑥𝑁𝑦 thin film which was deposited on cover glass. The dielectric constant was varied between 30-1200000 depending on the annealing temperature of the film, while the film permittivity ranges between 0-1.25×10-5 F/m.
Uncooled infrared detectors are utilized in various radiometric devices and cameras because of their low cost, light weight and performance. A pyroelectric detector is a class of uncooled infrared detector whose polarization changes with change in temperature. Infrared radiation from objects falls on top of the sensing layer of the pyroelectric detector and the absorbed radiation causes the temperature of the sensing layer to change. This work describes the deposition and characterization of AlxNy thin films for using them as pyroelectric detector’s sensing material. To test the sensitivity of infrared detection or pyroelectric effect of AlxNy thin films, capacitors of various sizes were fabricated. The diameter of the electrodes for capacitor used during testing of the device was 1100 μm while the distances between these two electrodes was 1100 μm. On a 3-inch diameter cleaned silicon wafer, 100 nm thick AlxNy thin films were deposited by radio frequency (RF) sputtering from an Al target in Ar: N2 environment. On top of this, a 100-nm thick Au layer was deposited and lifted off by using conventional photo lithography to form the electrodes of capacitors. All the layers were deposited by RF sputtering at room temperature. The thin film samples were annealed at 700 °C in N2 environment for 10 minutes. X-ray diffraction showed the films are poly-crystalline with peaks in (100), (002) and (101) directions. When the temperature varied between 303 K to 353 K, the pyroelectric coefficient was increased from 8.60 × 10-9 C/m2K to 3.76 × 10-8C/m2K with a room temperature pyroelectric coefficient value of 8.60×10-9C/m2K. The non-annealed films were found to be transparent between the wavelengths of 600 nm to 3000 nm. The refraction coefficient was found to be varied between 2.0 and 2.2 while the extinction coefficient was found to be zero. The optical bandgap determined using Tauc’s equation was 1.65 eV.
Pyroelectric detectors are the class of thermal detectors which change their spontaneous polarization when there is a change in temperature. The change in the spontaneous polarization occurs due to the absorption of infrared radiation which eventually produces a voltage. This work demonstrates the deposition and characterization of calcium modified lead titatante (Pb1-xCaxTiO3, PCT) thin films for using them as materials of pyroelectric thermal detectors. The PCT thin films were sputtered using an RF sputter system in Ar:O2 environment at room temperature. The thin films were grown on Au electrode. The capacitance was formed by using Au electrodes on top of PCT thin films which were fabricated by sputtering and liftoff. The PCT films were annealed at 450, 500, 550 and 600 °C in O2 environment for 15 minutes. Energy dispersive spectroscopy was done to determine the atomic composition of PCT films. Variations of capacitance, pyroelectric voltage, loss tangent and pyroelectric current between the temperature range 303 K to 353 K were determined. The PCT films were annealed at 550 °C showed the highest value of pyroelectric current and pyroelectric coefficient of 2.45 × 10-12 A and 1.99 μC/m2K respectively at room temperature. The loss tangent did not change much with temperature for all the PCT samples.
This work presents the deposition and characterization of AlxNy thin films for using them as pyroelectric detector material. To test the pyroelectric effect, capacitors with Au electrodes were fabricated. The diameter of the electrodes for capacitor used was 1100 μm while the distances between these two electrodes was 2200 μm. On a 3- inch diameter cleaned silicon wafer a 100-nm thick AlxNy films were deposited using an Al target and Ar:N2 = 1:1 flow and 5 mTorr chamber pressure. Finally, a 100-nm thick Au layer was deposited and lifted off by using conventional photo lithography to form the electrodes of capacitors. All the layers were deposited by radio frequency sputtering at room temperature. The AlxNy thin films were annealed at 700 0C in N2 environment for 10 minutes. X-ray diffraction showed that the films are poly-crystalline with peaks in (100), (002) and (101) directions. The pyroelectric current increased from 3.38 × 10-14 A at 303 K to 1.75 × 10-13 at 353 K. When the temperature varied between 303 K to 353 K the pyroelectric coefficient was increased from 8.60 × 10-9 C/m2K to 3.76 × 10-8 C/m2K while the loss tangent remains almost constant to ~1.5 × 10-5 when the temperature was varied in the same range.
In this paper, we discuss the development and operation of a scanning LADAR system. This system currently generates intensity and range images of a target with high spatial resolution located at a distance 5–10 m away from the sensor. The scanning LADAR system is designed with a purpose to generate polarization images of the target by integrating an in-line Stokes polarimeter in the receiver arm of the system. In this context, we have also discussed the basic design of the polarimeter using a liquid crystal retarder, and characterized the performance of the polarimeter for determining the polarization state of reflected light in the LADAR receiver.