Infrared absorbing electrodes

The principle of the Thomson polymer IR sensor is represented by Fig. 14 and Fig. 15. The P(VF2 TrFE) copolymer constitues the pyroelectric layer (5-10 pm), the insulation layer is a polyimide (10 pm). The upper electrode is also the infrared absorber and is made in aluminium or gold black. The lower level is the CCD level which constitues the second electrode. The polarisation of the polymer is realized by application of 100 V/pm between the two electrodes of the pyroelectric capacitor. 

FIGURE 2.76 Normalized infrared absorbance of the cation and anion of the IL in electrodes with RuOj contents of (a) 22, (b) 35, and (c) 48 wt.% during CV scans from —1.5 to +1.5 V at a scan rate of 5 mV s. Cross-sectional SEM images showing the structure of porous electrodes with RuOj contents of (d) 22, (e) 35, and (f) 48 wt.%. (Reproduced by permission of The Electrochemical Society from Richey, E. W., and Y. A. Elabd. 2013. Journal of the Electrochemical Society 160 A862-A868)... 

Infrared spectroelectrochemical methods, particularly those based on Fourier transform infrared (FTIR) spectroscopy can provide structural information that UV-visible absorbance techniques do not. FTIR spectroelectrochemistry has thus been fruitful in the characterization of reactions occurring on electrode surfaces. The technique requires very thin cells to overcome solvent absorption problems. 

Infrared (IR) spectroscopy with modulation of the electrode potential was used by Bewick and Kunimatsu to study the change of water structure at the Pt/H2S04 and Au/NaF interfaces. They observed several sharp bands within the OH region, superimposed on a broad absorbance background. The absorption increased at a higher field strength. The observed bands were similar to the bands recorded for small clusters of... 

There have been many investigations of photoinduced effects in -Si H films linked to material parameters. Changes have been observed in the carrier diffusion length, unpaired spin density, density of states in the gap, and infrared transmission. The transition from state A to B seems to be induced by any process that creates free carriers, including x-ray radiation and injection (double) from the electrodes. Because degradation in a solar cell is accentuated at the open-circuit voltage conditions, the A to B transition occurs upon recombination of excess free carriers in which the eneigy involved is less than the band gap. It has been pointed out that this transition is a relatively inefficient one and the increase in spin density takes place at a rate of 10-8 spins per absorbed photon. 

Semiconductor electrodes, which have much lower charge carrier densities (1013—1019 carriers/cm3), typically absorb in the infrared but exhibit much lower absorption by charge carriers than metals of comparable film thickness, and frequently show a transparency window in much of the visible spectrum due to a substantial band-gap energy, before absorbing again in the ultraviolet. For example, Sn02 and ZnO, like many common semiconductor electrode materi-... 

Infrared spectroscopy can provide a great deal of information on molecular identity and orientation at the electrode surface [51-53]. Molecular vibrational modes can also be sensitive to the presence of ionic species and variations in electrode potential [51,52]. In situ reflectance measurements in the infrared spectrum engender the same considerations of polarization and incident angles as in UV/visible reflectance. However, since water and other solvents employed in electrochemistry are strong IR absorbers, there is the additional problem of reduced throughput. This problem is alleviated with thin-layer spectroelectro-chemical cells [53]. 

The energy band diagram in the range of n-type region 15, p-type layer 12, p-type layer 11 and p-type layer 12 is shown above. Carriers excited by the infrared ray of 3-5 microns wavelength band absorbed below the electrode 19 are detected at between the electrode 19 and the common electrode 17. 

An HgCdTe layer is epitaxially grown on a first substrate. An adhesive is used to attach the HgCdTe layer to a sapphire substrate, which absorbes infrared radiation. The first substrate is removed and the epitaxially grown HgCdTe layer is shaped by etching to form detector regions 14, which are connected by electrodes 15. Photons which are not absorbed by the detector elements will be absorbed in the sapphire substrate. 

A vapor-phase diffused infrared light absorbing layer 5b of Hgi.yCd,Te is formed on a first side of a CdTe substrate 1. An Hgi.xCdxTe detector layer 6b is then formed on a second side of the substrate, opposite to the first side, by liquid-phase epitaxy. The detector layer is shaped to form detector elements which are connected by electrodes 7 and 8. The absorbing layer 5b will absorb photons which have not been absorbed by the detector elements. 

Pyroelectric materials are used mainly for the detection of infrared radiation. The elements for the detectors are typically thin slices of material (e.g. 1.0 x 1.0 x 0.1 mm) coated with conductive electrodes, one of which is a good absorber of the radiation. 

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