CN102003998B - High-sensitivity uncooled infrared detector - Google Patents

Abstract

The invention discloses a high-sensitivity uncooled infrared detector. In the detector, a copolymer of polyvinylidene fluoride and trifluoroethylene is used as a pyroelectric material and grown on a polyester material substrate, on which a metal bottom electrode is prepared, by a Langmuir-Blodgett method; then a top metal electrode is grown on the surface of the material to form a capacitor structure; and a poly-3,4-ethylenedioxythiophene/polystyrene sulfonate conductive polymer is grown on the top electrode to serve as an infrared absorbing layer.

Description

A kind of highly sensitive non-refrigerated infrared detector

Technical field

The present invention relates to the infrared eye technology, specifically refer to a kind of highly sensitive non-refrigerated infrared detector.

Background technology

The uncooled ir Detection Techniques are to need not the technology of refrigeration system to infrared radiation perception output, can be widely used in various fields such as national defence, space flight, medical science, production monitoring.Pyroelectric effect is that pyroelectricity material produces owing to spontaneous polarization varies with temperature.Pyroelectric detector just is being based on a kind of thermistor detector that pyroelectric effect grows up.Pyroelectric detector is that pyroelectricity material is thermal cross over an electric signal by absorbing infrared ray, thereby judges whether infrared radiation exists.Pyroelectric detector is a kind of non-refrigerated infrared detector of function admirable, is used for various sensing technologies because of it is light, simple in structure.Lead zirconate titanate (being called for short PZT) pottery is a kind of good pyroelectricity material, is widely used at present in the various infrared sensors.Yet the PZT pottery is in preparation, technology is comparatively complicated in the process, and for example the potsherd thickness requirement is thinned to below 20 microns, cost height not only, and homogeneity and yield rate also are greatly affected.In addition, not strong based on the anti-impact force of the infrared eye of PZT potsherd, so applied environment is subjected to certain limitation.Therefore, development function admirable, easily processing, pyroelectricity material that intensity is big are very important.Except the needs of above-mentioned technology, PZT pottery is because contain lead element, in the preparation of the production of its raw material, pottery and process environment polluted.European Union and Japan and other countries have been made laws and have been forbidden processing, growing leaded electrical equipment and electronic product, and China issues that also the related legal provision uses or bans use of the electronic product restriction that contains six kinds of poisonous and harmful substances, and one of them is exactly leaded electronic product.Electronics and IT products in the state key supervision catalogue of putting on market at present, will can not contain six class objectionable impuritiess such as lead, mercury, cadmium.Strengthen the electronics and IT products prevention and cure of pollution, the protection environment has become new century countries in the world inevitable problem.This shows that the alternative electronic material of development PZT pottery becomes inevitable.The multipolymer of polyvinylidene fluoride and trifluoro-ethylene [being called for short P (VDF-TrFE)] is a kind of ferroelectric polymer material of function admirable, and process is simple, and pollution-free, can be used for developing non-refrigerated infrared detector.Though report [the Sensors and Actuators A:Physical that utilizes P (VDF-TrFE) development infrared eye is arranged in the world, 22, (1989) 503], but because the heat of detector is isolated and the infrared absorption layer structural design is unreasonable, be difficult to obtain high-sensitive detector, and complex process has increased cost.This paper describes a kind of non-refrigerated infrared detector simple in structure and high-sensitive based on P (VDF-TrFE) material.

The invention reside in that to use P (VDF-TrFE) film pyroelectricity material, such material to have a preparation temperature low, technology is simple relatively.Overcome the silicon substrate material of the big thermal capacitance of traditional use in addition, but the utilization mylar is as backing material, its thermal capacitance is less relatively, and polyester substrate film and P (VDF-TrFE) are all flexible material, become difform pyroelectric detector thereby can prepare, widen the application of detector.This device is easy to the detector of its all band integratedly in addition, can prepare broadband detector.

Summary of the invention

Purpose of the present invention mainly is a kind of non-refrigerated infrared detector based on P (VDF-TrFE) ferroelectric polymer material of preparation.Technology is simple, and cost is low, need not refrigeration, and device prototype profile is various, and sensitivity is higher, but integration is strong and be easy to other band detectors integrated.

The present invention is achieved in that

The structure of detector is respectively from bottom to up, substrate 1, hearth electrode 2, photosensitive unit 3, top electrode 4, infrared absorption layer 5.

Substrate 1 is selected the polyester film of 2-5 micron thickness for use.Hearth electrode 2 is a width 0.2-1 millimeter, and thickness is the metal electrode of 50-100 nanometer.Photosensitive unit 3 is P (VDF _x-TrFE _y) (mol ratio x+y=100,50≤x≤100,0≤y≤50), the molecular formula of this material is [(CH2-CF2) _x-(CHF-CF ₂) _y-] _n, thickness 100-200 nanometer.Top electrode 4 is the 0.2-1 millimeter for width, and thickness is the metal electrode of 20-50 nanometer.Infrared absorption layer 5 is the poly-3 of thickness 100-200 nanometer, 4-ethene dioxythiophene/polystyrolsulfon acid.

Concrete device preparation process is:

(1) hearth electrode preparation

The evaporation layer of metal film is as hearth electrode on the polyester film substrate of thickness 2-5 micron, and electrode is bar shaped, and width is the 0.2-0.5 millimeter, and thickness is between the 50-100 nanometer, and electrode can use and comprise aluminium, gold, silver, platinum, metals such as nickel.

(2) photosensitive unit preparation

Photosensitive first P (VDF-TrFE) membraneous material uses bright wrong that-woman's dress spy (Langmuir-Blodgett is called for short LB) technical method, and it is grown on the polyester film substrate that hearth electrode is arranged.Particularly, take by weighing a certain amount of P (VDF-TrFE) (0.01-0.02 gram), transfer in 250 ml flasks, add 100-200 milliliter dimethyl sulfoxide (DMSO) (DMSO), stirred 3-5 hour down, be cooled to room temperature at 50-80 ℃.Adopt LB film preparing system P (VDF-TrFE) thin polymer film of growing, method is horizontal czochralski method.Monofilm lifts under surface pressure 2-5 milli Newton/meter, and monofilm thickness obtains film thickness 100-200 nanometer between the 1-2 nanometer, and last film was 120-140 ℃ of annealing 2-5 hour.

(3) top electrode preparation

Utilize the evaporation coating method to prepare metal film as top electrode, the very bar shaped that powers on, width is the 0.2-0.5 millimeter, and top electrode need be prepared into semi-permeable diaphragm, and thickness is in the 20-40 nanometer.Upper/lower electrode intersects, and the part that overlaps is the responsive unit of detector, forms capacitor arrangement.

(4) infrared absorption layer preparation

Utilize poly-3,4-ethene dioxythiophene/polystyrolsulfon acid (being called for short PEDOT-PSS) conducting polymer is spin-coated on PEDOT-PSS solution on the top electrode thickness 100-200 nanometer as infrared absorption layer, toasted 30 minutes down at 80 ℃, form the infrared absorption layer structure.

The voltage responsive of film can be explained by formula (1):

$R_v=\frac{\mathrm{p\&eta;\&omega;}{\mathrm{<figure-callout\; id="1"\; label="AR\; p\; G"\; filenames="HSA00000275687200011.png"\; state="\{\{state\}\}">AR</figure-callout>}}_p}{G}---\left(1\right)$

Wherein p is a pyroelectric coefficient, and η is an absorptivity, and ω is a frequency, and A is for surveying elemental area, R _pFor surveying the equivalent resistance of unit, G is a thermal conductance, τ _TBe calorifics time constant, τ _eBe the electricity time constant.

Noise voltage is tried to achieve by formula (2),

$\mathrm{\&Delta;}{V}_N=\sqrt{\underset{i}{\mathrm{\&Sigma;}}\frac{{(n_i-n_{\mathrm{is}})}^2}{N}}---\left(2\right)$

Wherein, n _iFor measuring the magnitude of voltage of noise curve, n _IsBe the magnitude of voltage on the response curve after passing through smoothly, Δ V _NBe the noise voltage of being asked, consider that the bandwidth of test macro is

Then detectivity is

$D*=\frac{\sqrt{A}}{\mathrm{NEP}}=\sqrt{A}\frac{R_v}{\mathrm{\&Delta;}{V}_N/\sqrt{\mathrm{\&Delta;f}}}=\sqrt{A}\sqrt{\mathrm{\&Delta;f}}\frac{V_R}{W_0\mathrm{\&Delta;}{V}_N}---\left(3\right)$

Use the infrared eye of the present invention's preparation, will have following advantage:

1, detector preparation technology is simple, cost is low, and process and detector itself do not cause any pollution to environment.

2, detector has good stable and reliability, and the course of work need not refrigeration.

3, this material of P (VDF-TrFE) can be prepared as array element, can realize the radiographic measurement to the infrared target source.

Description of drawings

Fig. 1 is a detector cross section structure synoptic diagram, among the figure, and 1 substrate, 2 hearth electrodes, 3 photosensitive yuan, 4 top electrodes, 5 infrared absorption layers.

Embodiment

To be in conjunction with the accompanying drawings 1 below, explain specific implementation method of the present invention:

(1) polyester film of selecting 2.5 microns of thickness for use is as substrate (see among Fig. 1 1).

(2) hearth electrode preparation, evaporativity layer of metal aluminium film is as hearth electrode on substrate film, and electrode is bar shaped, and width is 0.5 millimeter, thickness 70 nanometers, (see among Fig. 1 2).

(3) P (VDF-TrFE) film preparation is used Langmuir-Blodgett (LB) technical method with P (VDF-TrFE) membraneous material, is grown in to prepare on the polyester film substrate that hearth electrode is arranged.Particularly, take by weighing P (VDF-TrFE, 70: 30mol%) 0.02 restrain, transfer in one 250 ml flasks, add 100 milliliters of dimethyl sulfoxide (DMSO)s (DMSO), stirred 3 hours down, be cooled to room temperature at 80 ℃.Adopt LB film growth system P (VDF-TrFE) thin polymer film of growing, monofilm lifts film under surface pressure 5 milli Newton/meter, monofilm thickness 1.8 nanometers repeatedly lift the film that obtains thickness 100 nanometers (see among Fig. 1 3), and last film was 140 ℃ of annealing 5 hours.

(4) top electrode preparation utilizes evaporation coating to prepare the aluminium film as top electrode, forms capacitor arrangement, the very bar shaped that powers on, width is 0.4 millimeter, top electrode need be prepared into semi-permeable diaphragm, thickness 20 nanometers (see among Fig. 1 4), top electrode intersects with hearth electrode, and the part that overlaps be that detector is responsive first.

(5) infrared absorption layer preparation utilizes poly-ly 3, and 4-ethene dioxythiophene/polystyrolsulfon acid (PEDOT-PSS) conducting polymer is as infrared absorption layer (see among Fig. 1 5).PEDOT-PSS solution is spin-coated on top electrode aluminium surface, and thickness 200 nanometers were toasted 30 minutes down at 80 ℃, formed the infrared absorption layer structure.

Claims (1)

1. non-refrigerated infrared detector, its structure upwards is followed successively by hearth electrode (2), photosensitive unit (3), top electrode (4) and infrared absorption layer (5) from substrate (1), it is characterized in that: it is the polyvinylidene fluoride of 100-200 nanometer and the copolymer p (VDF of trifluoro-ethylene that described photosensitive unit (3) adopts thickness _x-TrFE _y) the pyroelectricity material film, the mol ratio x+y=100 of material, 50≤x≤100,0≤y≤50; It is the poly-3 of 100-200 nanometer that described infrared absorption layer (5) adopts thickness, 4-ethene dioxythiophene/polystyrolsulfon acid film.

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