Charge transfer device (CTD) detectors consist of two closely related silicon integrated circuits: the charge-coupled device (CCD), invented in 1970, and the charge injection device (CID), invented in 1973. Initially, several applications were proposed for these integrated circuits, including use as shift registers, logic and memory devices, electronic delay lines, and imaging detectors. The last application has so dominated the design and use of CTDs that they are among the most common electronic imaging detectors manufactured today.Early CTD technology was advanced by two different groups with contrast-' ing needs. The first group, composed of electronics manufacturing companies such as AT&T, RCA, Fairchild, GE, Phillips, Texas Instruments, and Westinghouse, supported the early development of CTDs in an effort to design and manufacture solid-state television cameras.

This is the second article in a two-part series describing the operation, performance characteristics, and spectroscopic application of charge transfer devices (CTDs) in analytical chemistry. The first article in the series describes the new generation of integrating multichannel detectors, the charge injection device (CID), and the charge-coupled device (CCD). The first article also discusses the spectroscopically pertinent characteristics of these detectors and presents performance data for representative devices. This article covers three major topics related to the optimum use of integrating detectors in analytical spectroscopy. The advantages of employing integrating multichannel detectors in analytical spectroscopy, rather than a single detector in a wavelength scanning system or an interferometer, are discussed. Included are detector read noise considerations which have not been considered in previous performance comparisons. When one is employing an integrating detector in luminescence, absorption, and emission applications, achievable sensitivity is dependent on differing detector parameters. In the first case, quantum efficiency and read noise are of the greatest importance, whereas in the later two cases, dynamic range is most significant. The calculation of minimum detectable analyte signal for these three techniques illustrates the differences between integrating detectors and detectors which produce a photocurrent. This discussion also illustrates the great sensitivity that can be achieved with a modern CTD detector. Factors pertaining to the optical design of spectrometers which efficiently use CTDs are presented, along with examples of linear and two-dimensional dispersive polychromators employing CTDs. Low-light-level imaging and a nonconventional method of using a CCD for rapid scanning spectrophotometry are also discussed.

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This article is the first in a two-part series describing the operation, characteristics, and application of a new class of solid-state multichannel UV-visible detectors. In this paper, charge transfer devices (CTDs) are described. Detector characteristics pertinent to spectroscopic application—including quantum efficiency, read noise, dark count rate, and available formats—are emphasized. Unique capabilities, such as the ability to nondestructively read out the detector array and the ability to alter the effective detector element size by a process called binning, are described. CTDs with peak quantum efficiencies over 80% and significant responsivity over the wavelength range of 0.1 nm to 1100 nm are discussed. Exceptionally low dark count rates, which allow integration times of up to many hours and read noises more than two orders of magnitude lower than those read by commercially available PDA detectors, contribute to the outstanding performance offered by these detectors.

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