Pyroelectric IR Detector Research Articles

Deposition of self-polarized PZT films by planar multi-target sputtering

A planar multi target sputtering approach was used to deposit self polarized PZT films on TiO2/Pt bottom electrodes for the use in thin film pyroelectric IR detector arrays. By using elevated substrate temperatures of about 450°C “in situ” growth of tetragonal PZT could be achieved. The films exhibited pyroelectric currents without poling. The pyroelectric coefficient was 2×10−4 C/m2K, the dielectric constant was 300 and dielectric loss tan δ was 0.01. The self polarization disappears after heating the sample to 600°C. Stresses were studied in the thin film processing for the bottom electrode and the PZT film. The TiO2/Pt electrode is under high tensile stress of 900 MPa after preparation. PZT has a small compressive stress of -60 MPa, the whole TiO2/Pt/PZT stack has a tensile stress of +80 MPa. This low stress level together with the self polarization and the good electrical properties makes the films suitable for the use in pyroelectric detector arrays.

Reactive ion beam etching of lithium tantalate and its application for pyroelectric infrared detectors

The properties of reactive ion beam etching (RIBE) of single crystalline lithium tantalate (LiTaO 3) and photoresist are reported, with particular attention given to the dependence on the gas flow, the ion beam current, the accelerating voltage as well as the angle of incidence. For the experiments a filamentless r.f. ion beam source and gas mixtures containing C 2F 6, CF 4, Ar and O 2 were applied. Compared with Ar ion beam etching (IBE) the LiTaO 3/photoresist etch rate selectivity was found to be three times higher. High selective RIBE of LiTaO 3 and photoresist is an efficient process for the production of one- and two-dimensional pyroelectric IR detectors: The thickness of a LiTaO 3 wafer patterned with photoresist must be reduced by etching by about 10–15 μm.

Plasma processing techniques used at Caswell

Abstract

Preparation of La- and Mg-Modified PbTiO<sub>3</sub> Ceramics and Their Pyroelectric Properties

The results of this study are summarized as follows:(1) Lanthanum- and magnesium-modified PbTiO3 (PLMT) ceramics were obtained by normal sintering using pure PbTiO3 as a packing powder for the crucible.(2) The tetragonality c/a of PLMT ceramics was nearly a constant value of 1.033 in the range of y=0-0.020. This result indicates that the added Mg2+ ions (0.066nm) partially substitute Ti4+ ions (0.068nm) at the B-site in PbTiO3.(3) The Curie point shifted to the lower-temperature side with increasing amount of Mg2+ ion addition.(4) The PLMT ceramics of y=0.005 exhibited the largest pyroelectric coefficient of 1.8×10-8C/cm2⋅K, which was nearly equal to that of PbTiO3-system ceramics. The PLMT ceramics are suitable as the element material of point-type pyroelectric IR detectors.

New structure gas sensor using a modulation-type pyroelectric ir detector

Abstract We developed a new structure gas sensor using a new type of pyroelectric IR detector which contains a pyroelectric element (LiTaO3) and a small chopper using a piezoelectric material in the same package. The accuracy of measurement is ±0.2% in the 0 ∼ 20% concentration range of CO2 gas. The change in the output signal is within ±0.5% in a temperature range of 0 ∼ 40°C. The accuracy and stability of the new gas sensor are superior to those of the conventional non-dispersive IR gas sensor due to the new structure and the new type of pyroelectric IR detector.

Dielectric behaviour of TGS crystals poled by doping on repeated temperature cycling

AbstractData characterizing the stability of basic dielectric properties against thermal treatement are presented for crystals of TGS and deuterated TGS doped with alanine or bivalent platinum. Complex permittivity and over‐all polarization have been measured during a heating‐cooling cycle. In alanine doped crystals the heating and cooling curves are perfectly reproducible. In Pt‐doped samples the reproducibility is worse, for pure TGS the properties on cooling are strongly influenced by domain effects. These data made it possible to estimate the change of the figures of merit for pyroelectric ir detectors due to transient heating.

A New-Structure IR Gas Sensor

We developed a new-structure IR gas sensor using a new type of pyroelectric IR detector with a solid-state chopper and an optical filter in the same package. This gas sensor enables high accuracy and high reliability due to the new structure (DEA Structure) and the new IR detector. The accuracy of the measurement is ±0.5% in the range of a 0∼20% concentration of CO2 gas. The change of the output signal is within ±0.8% for 1500 hours. The characteristics (especially long-term operation) are superior to those of the conventional NDIR-type gas sensor.

Modulation Type Pyroelectric IR Detector

We have developed a new type of pyroelectric IR detector which contains a sensing part and a solid state chopper with two bimorph vibrators and two slit plates in the same package. This new detector (M-type IR detector) features high reliability, small volume and low electric power consumption compared with conventional pyroelectric IR detectors using a rotating chopper. The output voltage and noise voltage of the M-type IR detector have been investigated theoretically and experimentally. It was confirmed that a good performance can be achieved in the M-type IR detector by optimizing the relative position of the two slit plates and the aperture diameter of the shield box.

Application of Pyroelectricity of LiTaO3 for Infrared Detectors

We developed a new structure (PEC structure) pyroelectric IR detector using LiTaO3 single crystal. The detector with this structure has good performance, high reliability and is suited to mass-production. In addition, we fabricated a new IR detector structure containing both the chopper and the pyroelectric element in the same package (M-type detector). The structure and the characteristics of these detectors are described.

Noise cancellation in pyroelectric self-scanning IR detector arrays

Noise cancellation in pyroelectric self-scanning IR detector arrays

Irreversible laser damage in ir detector materials

Irreversible laser damage phenomena are investigated in pyroelectric and semiconductor ir detector materials. Thermal damage phenomena in these materials are reviewed, and new results are presented. Theoretical models, which successfully describe thermal damage in detector materials, are reviewed, and criteria for the application of these models are discussed.