Detectors, infrared mercury cadmium

An imager having an element packing density of 90% is disclosed in US-A-4104674. Infrared photovoltaic detectors of mercury cadmium telluride are mounted on a silicon substrate. Electrical contacts are made by thin-film metallizations. 

UHV is normally required when studying low-area flat surfaces (exceptionally this would not be a requirement if the adsorbate, such as a surfactant, is capable of displacing surface impurities) and this requires sophisticated equipment. Also, the high sensitivity needed for the measurement of spectra from single monolayers requires the use of FT-IR spectrometers with selective photoconductive infrared detectors the mercury/cadmium telluride detector which covers the major range of the spectrum down... 

There are two major detector materials in the near infrared, mercury cadmium telluride (Hg Cd Te), and indium antimony (In Sb), although some lower efficiency detector arrays have been made with platinum silicide (PtSi). This wavelength region was the first to utilize arrays and is the most developed to date. Part of this has been due to the development in the early 1990s of Hg Cd Te arrays for the NICMOS on the HST. The NICMOS arrays contained 256 X 256 elements. Currently, 2048 x 2048 arrays of both Hg Cd Te and ln Sb are under development. 

Chemical Gas Detection. Spectral identification of gases in industrial processing and atmospheric contamination is becoming an important tool for process control and monitoring of air quaUty. The present optical method uses the ftir (Fourier transform infrared) interference spectrometer having high resolution (<1 cm ) capabiUty and excellent sensitivity (few ppb) with the use of cooled MCT (mercury—cadmium—teUuride) (2) detectors. 

W.F.H. Micklethwaite, The Crystal Growth of Cadmium Mercury Telluride Paul E. Petersen, Auger Recombination in Mercury Cadmium Telluride R.M. Broudy and V.J. Mazurczyck, (HgCd)Te Photoconductive Detectors M.B. Reine, A.K. Sood, and T.J. Tredwell, Photovoltaic Infrared Detectors M.A. Kinch, Metal-Insulator-Semiconductor Infrared Detectors... 

Mercury-cadmium-telluride is the principal semiconductor now being used in advanced infrared systems, both for military and other surveillance applications. Its preparation and use in infrared detectors and arrays was the subject of Volume 18 of this treatise. New generations of detectors and arrays require sophisticated epitaxial growth, which in turn requires precise phase diagram data. 

A photoconductive detector is a semiconductor whose conductivity increases when infrared radiation excites electrons from the valence band to the conduction band. Photovoltaic detectors contain pn junctions, across which an electric field exists. Absorption of infrared radiation creates electrons and holes, which are attracted to opposite sides of the junction and which change the voltage across the junction. Mercury cadmium telluride (Hg,. Cd/Te, 0 < x < 1) is a detector material whose sensitivity to different wavelengths is affected by the stoichiome-try coefficient, x. Photoconductive and photovoltaic devices can be cooled to 77 K (liquid nitrogen temperature) to reduce thermal electric noise by more than an order of magnitude. 

The infrared spectra were recorded by an evacuable FT-IR spectrometer, Broker IFS-113v, equipped with a liquid nitrogen cooled MCT (mercury cadmium telluride) detector. All infrared spectra showed were obtained by substraction of the background (oxide) spectrum, recorded at the same temperature. 

Marcott, C., Reeder, R. C., Paschalis, E. P., Talakis, D. N., Boskey, A. L. and Mendelsohn, R. (1998) Infrared microspectroscopic imaging of biomineralized tissues using a mercury-cadmium-telluride focal-plane array detector. Cell. Mol. Biol. 44, 109-115. 

Marcott, Curtis and Reeder, C. Robert (1998) Industrial applications of FUR microspectro-scopic imaging using a mercury-cadmium-telluride focal-plane array detector. Proceedings of the SPIE - Infrared Technology and Applications XXIV, Vol. 3436, 285-9. 

All infrared spectra were recorded with an IR-PLAN microscope (IR-PLAN is a registered trade mark of Spectra Tech, Inc.) integrated to a Perkin-Elmer Model 1800 Fourier transform infrared (FT-IR) spectrophotometer. The spectrophotometer consisted of a proprietary heated wire source operated at 1050°C, a germanium overcoated potassium bromide beamsplitter, and a narrow-band mercury-cadmium-telluride (HgCdTe) detector. The detector was dedicated to the microscope and had an active area of 250 x 250 pm. The entire optical path of the system microscope was purged with dry nitrogen. 

Spectra were measured at 4 cm"1 resolution with a Nicolet 740 Fourier transform infrared (FT-IR) spectrometer equipped with a medium range mercury-cadmium-telluride detector. A series of 128 scan spectra (43 sec measurement time) was collected every 5 min for the first hour and then every 10 min for 3 hr. At the end of the 4 hr period, saline or Milli-Q water of the same pH was substituted for the polymer solution and the data acquistion program was restarted. 

All of the infrared experiments were performed on a Digilab FTS-40 Fourier transform infrared (FT-IR) spectrometer equipped with a narrow-band liquid-nitrogen-cooled mercury-cadmium-telluride (MCT) detector. The spectrometer was operated at a nominal resolution of 4 cm-1 using a mirror velocity of 1.28 cm/s. The data collected using the gas chromatography (GC) IR software were measured at 8 cm-1 resolution. Protein assays for all the experiments were measured on a Beckman DU-70 UV-visible spectrophotometer. 

The invention of US-A-3902924 is concerned with low temperature growth of mercury cadmium telluride layers on insulating substrates by liquid phase epitaxy. Infrared detectors are fabricated to assist with the evaluation of the grown layers. 

A problem with the monolithic arrays is that the techniques for building metal-oxide-semiconductor (MOS) devices in silicon cannot be transferred intact to narrow bandgap materials such as mercury cadmium telluride, mainly due to tunneling and avalanche breakdown occuring at very low voltages. A monolithic array, in which read-out electronics is integrated in the same mercury cadmium telluride chip as the infrared detectors, is therefore difficult to achieve. 

Fig. 10. Improvement of the infrared spectrophotometer. Infrared spectra of fully oxidized bovine heart cytochrome c oxidase cyanide derivatives measured with (A) a dispersive infrared spectrophotometer (Perkin-Elmer Model 180) and (B) a FTIR spectrometer equipped with a mercury/cadmium/tellurium detector (Perkin-Elmer Model 1800). Concentrations of the enzyme (O.VmM) and cyanide (19.4 M) were identical in both measurements.

Cyanide is also an effective infrared probe (Yoshikawa et al., 1985). A drawback of this reagent as an infrared probe is its infrared intensity, which is much weaker than that of CO. However, as given in Fig. 10, the recent development in the infrared technique has solved this problem with the introduction of a mercury/cadmium/tellurium (MCT) detector (Fig. 10) (Yoshikawa et al., 1995). The C-N stretch vibrational band is sensitive to many factors, such as the oxidation state and species of the coordinating metal, the structures of porphyrin ring substituents, and the ligand trans to the cyanide and protein structure (Yoshikawa et al., 1985). This technique can be quite effectively applied for determination of the protonation state of the cyanide bound at a metal site. Possible binding modes of cyanide to a ferric iron are shown by Structures (1), (11), and (HI). Infrared spectroscopy is the best method for identihcation of these... 

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