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United States Department of Agriculture

Agricultural Research Service

Title: Solid State Array Detectors for Analytical Spectrometry

Authors
item Harnly, James
item Fields, Robert

Submitted to: Journal of Applied Spectroscopy
Publication Type: Review Article
Publication Acceptance Date: September 1, 1997
Publication Date: N/A

Interpretive Summary: This is an invited review article on solid state array detectors; detectors which are revolutionizing the field of atomic and molecular spectroscopy. Solid state array detectors enable the analyst to acquire vast amounts of spectrally and/or spatially resolved data in short periods of time. These detectors offer high quantum efficiency, low read noise, wide dynamic range, low power requirements, and rugged, but compact packaging. In addition, as solid state technology improves at a rapid rate, the cost of these detectors is continuously decreasing while flexibility in design is increasing. As a result, a wide variety of arrays are currently commercially available, with even more on the horizon. This article provides the reader with an introduction to the variety and the nature of solid state array detectors and shows how the design of complimentary detectors and dispersion optics provides increased analytical capabilities. .Several instruments are chosen as examples to illustrate the impact of solid states array detectors on analytical spectrometry. Several of these detectors have been used at the Food Composition Laboratory at USDA for the development of new instrumentation for multielement atomic absorption spectrometry.

Technical Abstract: Solid state array detectors offer the ability to acquire spectrally and/or spatially resolved data. They can be categorized according to type of material, pixel structure, type of signal generated, method of charge transfer, and location of pre-amplifier. All solid state detectors are composed of pure or doped semiconductor materials, the most common of which hare n- and p-doped silicon. The type of semiconductor and its physical structure determine the useful wavelength range and quantum efficiency. Array detectors have been used for applications ranging from the x-ray region to the mid-infrared region. Individual pixels are constructed of pure semiconductor materials or joined as metal oxide semiconductor capacitors or photodiodes. Photons striking pixels generate electrons and holes which may be a) used to increase conductivity, b) collected by MOS capacitors, or c) generate a current or voltage. Pixels can be square or rectangular with small (1:1) or large (100:1) aspects, in linear or 2-dimensional arrays. The charge from each pixel can be shifted sequentially to the read amplifier (charge coupled devices) or each pixel can be connected randomly to the read amplifier (like charge injection devices). A pre-amplifier may service an entire array or a fraction of it, a row or column, or just one pixel (active pixel devices). In most cases, the pixel read noise is sufficiently low that the spectroscopic source noise is limiting. Application to Raman spectrometry are considered.

Last Modified: 7/25/2014
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