Academic journal article Journal of Asian Civilizations

Scanning Electron Microscopy in Archaeology: The Analysis of Unknown Specimen Recovered from District Shangla, Pakistan

Academic journal article Journal of Asian Civilizations

Scanning Electron Microscopy in Archaeology: The Analysis of Unknown Specimen Recovered from District Shangla, Pakistan

Article excerpt

The application of the physical and chemical sciences in archaeology has made it possible to solve some of the problems and questions of archaeology. In 1888 the first specialized laboratory was established in Berlin called the Chemisches Labor der Königlichen Museen zu Berlin (Doménech-Carbó et al. 2009:1). By 20th century, the application of scientific methods and principles in archaeology further characterized cultural materials (Artioli 2010:1).

During the late 1950s and early 1960s, the implementation of scientific philosophy in social sciences played an important role in the development of new directions, in which ""New Archaeology1'' is one of the best example. New Archaeology acquired many scientific techniques and resulted in a new branch of archaeology called "archaeometry" in which archaeological study was based on "the documentation of culture contact on the basis of hard evidence, rather than on supposed similarities of form' (Price and Burton 2012: 2).

Furthermore,

It is a specialized branch of archaeological science that involves the measurement of the physical or chemical properties of archaeological materials (Price and Burton 2012: 2).

These scientific developments in archaeology enforced archaeologists to get experienced with the scientific techniques and methods to analyze the Hard Evidence (Pollard et al. 2007: 5-10).

In archaeology, the application of analytical chemistry has made it possible to carry out an analytical research by using a specific analytical method, in order to get the required result from the archaeological Hard Evidence.

Scanning Electron Microscopy (SEM) is one of such analytical technique used for the study of archaeological material. Cambridge Scientific Instrument Company has the credit to develop first commercial Scanning Electron Microscope. It was applied for the first time in archaeology for the study of pollens by Jonathan Pilcher (1968). Later on, Don Brothwell (1969) became well known of the importance of Scanning Electron Microscope in archaeology and initiated the use of SEM for the study of different archaeological materials. By 1985, the use of SEM became very broad in the field of archaeology (Brothwell 1969: 564-66; Freestone 1987: 21-31).

Scanning Electron Microscope (SEM) is capable of scanning a specimen to give us a high magnification image of the specimen. Different components of a Scanning Electron Microscope work together, to produce a high magnification image. Electron Gun of SEM produces electron beams. The diameter of electron beams are adjusted with the help of condenser lens and objective lens, placed below the electron gun. The vacuum inside the specimen chamber is kept at a high vacuum of 10^sup -3^ to 10^sup -4^ Pa. Specimen is placed on a firmly supporting stage that can be moved in any direction. As the electron beams come into contact with the specimen, the specimen emits secondary electrons. These secondary electrons are detected by the secondary electron detector. The secondary electron detector transfers the output to the display unit. The image is produced in a digital format and can be observed on the LCD (www.jeol.co.jp).

The Scanning Electron Microscope is also equipped with EDS (Energy-Dispersive X-Ray Spectroscopy). EDS analysis is a technique which uses specific x-rays emitted from the atoms of a sample. Atoms of the sample emit these specific x-rays as the electrons jumps into the lower orbitals. When high energy electrons strike with electrons of the atoms in the sample, it force the electrons to jump from inner shells of the atoms so that this create vacancies. These vacancies are then filled by the electrons from higher orbits which cause emission of x-rays with different energies and each energy x-ray is unique for each element in a sample. This makes it possible for the EDS detector to measure and compare the energy with the standard values of various elements. Through this technique we become able to know the elemental composition of a specimen (Shindo and Oikawa 2002:83-85). …

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