Müller, Erwin W., also spelled Mueller (1911-1977), was a German-born American physicist who, in 1951, invented the ion microscope. He developed it from the field-emission microscope, which he had invented in 1936.
In a field-emission microscope, a high negative voltage is applied to a metal needle and electrons ejected from the needle are attracted to a positively charged screen. The images displayed on the screen are too fuzzy to reveal individual atoms. But they can give information about the ways electrons stream from different metals.
In an ion microscope, a needle repels positively charged gas atoms—that is, positive ions of gas. The ions fly to a negatively charged screen. In 1951, Müller used an ion microscope to take the first picture of the arrangement of atoms on a metal’s surface (see Ion microscope).
In 1954, Müller developed a modified version of the ion microscope, the atom-probe field-ion microscope. It can analyze a single atom on a specimen’s surface. It can also remove atoms from a metal surface and send them to an instrument called a mass spectrometer (see Mass spectrometry). This technique is called field ionization mass spectrometry.
Erwin Wilhelm Müller was born in Berlin on June 13, 1911. He became a United States citizen in 1962. He died in Washington, D.C., on May 17, 1977.
