Karl Wilhelm Sali Baedeker (3 February 1877 – 6 August 1914) was a German

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate caus ...

, and a professor at the

University of Jena The University of Jena, officially the Friedrich Schiller University Jena (german: Friedrich-Schiller-Universität Jena, abbreviated FSU, shortened form ''Uni Jena''), is a public research university located in Jena, Thuringia, Germany. The u ...

. He was the grandson of

Karl Baedeker Karl Ludwig Johannes Baedeker ( , ; 3 November 1801 – 4 October 1859) was a German publisher whose company, Baedeker, set the standard for authoritative guidebooks for tourists. Karl Baedeker was descended from a long line of printers, bo ...

, the founder of the

eponymous An eponym is a person, a place, or a thing after whom or which someone or something is, or is believed to be, named. The adjectives which are derived from the word eponym include ''eponymous'' and ''eponymic''. Usage of the word The term ''epon ...

travel guide publishing house, and the son of Fritz Baedeker (1844 - 1925), who ran the same company from 1869 until his death in 1925. One of his scientific discoveries was that the

resistivity Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current. A low resistivity indicates a material that readily allows ...

of cuprous iodide (CuI) depended on its

stoichiometry Stoichiometry refers to the relationship between the quantities of reactants and products before, during, and following chemical reactions. Stoichiometry is founded on the law of conservation of mass where the total mass of the reactants equal ...

. Thin films of the material became much more conductive when exposed to iodine vapor; the effect was reversible. This was the first example of doping a semiconductor to change its properties and also the discovery of transparent conductive materials. He also observed a

Hall effect The Hall effect is the production of a voltage difference (the Hall voltage) across an electrical conductor that is transverse to an electric current in the conductor and to an applied magnetic field perpendicular to the current. It was discove ...

in transparent copper iodide thin films that had the reverse sign to that in copper, an observation of what was later to be known as conduction by

electron hole In physics, chemistry, and electronic engineering, an electron hole (often simply called a hole) is a quasiparticle which is the lack of an electron at a position where one could exist in an atom or atomic lattice. Since in a normal atom or c ...

s in

semiconductor A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. ...

s. This observation was critical in developing the theory of electron conduction in solids. Along with his graduate student Karl Steinberg, Baedeker studied the effect of varying concentration of iodine on the electrical properties of copper iodide. He also is credited with making the first transparent conducting oxide (TCO) thin film,

cadmium oxide Cadmium oxide is an inorganic compound with the formula CdO. It is one of the main precursors to other cadmium compounds. It crystallizes in a cubic rocksalt lattice like sodium chloride, with octahedral cation and anion centers. It occurs natur ...

(CdO), in 1907. TCOs are now ubiquitous in optoelectronics and a multibillion-dollar industry. Baedeker was killed in action in August 1914 during World War I at the

Battle of Liège A battle is an occurrence of combat in warfare between opposing military units of any number or size. A war usually consists of multiple battles. In general, a battle is a military engagement that is well defined in duration, area, and force ...

. His son, Karl Friedrich Baedeker revived the

Baedeker Verlag Karl Baedeker, founded by Karl Baedeker on July 1, 1827, is a German publisher and pioneer in the business of worldwide travel guides. The guides, often referred to simply as " Baedekers" (a term sometimes used to refer to similar works f ...

publishing house after the

Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...

. In 2014, a conference on transparent conducting oxides was held in Leipzig to commemorate the centenary of Baedeker's death. A paper on the life and work of Baedeker was published in the proceedings of the meeting.Marius Grundman, "Karl Baedeker (1877-1914) and the discovery of transparent conductive materials", Physica Status Solidi A 212(7), 1409-1426 (2015), doi: 10.1002/pssa.201431921.

References

{{DEFAULTSORT:Baedeker, Karl 1877 births 1914 deaths 20th-century German physicists German military personnel killed in World War I People educated at the St. Thomas School, Leipzig