Editing Ultraviolet–visible spectroscopy (section)

== Microspectrophotometry ==
UV–visible spectroscopy of microscopic samples is done by integrating an optical microscope with UV–visible optics, white light sources, a [[monochromator]], and a sensitive detector such as a [[charge-coupled device]] (CCD) or [[photomultiplier]] tube (PMT). As only a single optical path is available, these are single beam instruments. Modern instruments are capable of measuring UV–visible spectra in both reflectance and transmission of micron-scale sampling areas. The advantages of using such instruments is that they are able to measure microscopic samples but are also able to measure the spectra of larger samples with high spatial resolution. As such, they are used in the forensic laboratory to analyze the dyes and pigments in individual textile fibers,<ref>Forensic Fiber Examination Guidelines, Scientific Working Group-Materials, 1999, http://www.swgmat.org/fiber.htm</ref> microscopic paint chips<ref>Standard Guide for Microspectrophotometry and Color Measurement in Forensic Paint Analysis, Scientific Working Group-Materials, 1999, http://www.swgmat.org/paint.htm</ref> and the color of glass fragments. They are also used in materials science and biological research and for determining the energy content of coal and petroleum source rock by measuring the [[vitrinite]] reflectance. Microspectrophotometers are used in the semiconductor and micro-optics industries for monitoring the thickness of thin films after they have been deposited. In the semiconductor industry, they are used because the critical dimensions of circuitry is microscopic. A typical test of a semiconductor wafer would entail the acquisition of spectra from many points on a patterned or unpatterned wafer. The thickness of the deposited films may be calculated from the [[Thin-film interference|interference pattern]] of the spectra. In addition, ultraviolet–visible spectrophotometry can be used to determine the thickness, along with the refractive index and extinction coefficient of thin films.<ref name = "Löper2015"/> A map of the film thickness across the entire wafer can then be generated and used for quality control purposes.<ref>{{cite book |doi=10.1109/IMTC.1994.352008 |chapter=Spectroscopic thin film thickness measurement system for semiconductor industries |title=Conference Proceedings. 10th Anniversary. IMTC/94. Advanced Technologies in I & M. 1994 IEEE Instrumentation and Measurement Technology Conference (Cat. No.94CH3424-9) |year=1994 |last1=Horie |first1=M. |last2=Fujiwara |first2=N. |last3=Kokubo |first3=M. |last4=Kondo |first4=N. |pages=677–682 |isbn=0-7803-1880-3 |s2cid=110637259 }}</ref>