Invited Paper TF+AS+EM+NS+SS-ThM3
Tracing the History of Inorganic Thin Films from ~2500 BC to the Early 1900s AD

Thursday, October 31, 2013, 8:40 am, Room 104 A

Gold was likely the first metal discovered by man, more than 11,000 years ago. However, unlike copper (~9000 BC), bronze (~3500 BC), and wrought iron (~2500-3000 BC), it was too soft for use as tools and weapons. Instead, gold was used for decoration, religious artifacts, and commerce. The earliest documented inorganic thin films were gold layers, < 3000 Å thick, produced chemi-mechanically by Egyptians more than 5000 years ago. Examples, gilded on statues and artifacts (requiring interfacial adhesion layers), were found in early stone pyramids dating to ~2650 BC in Saqqara, Egypt. Spectacular samples of embossed Au sheets date to at least 2600 BC. Fatty-acid-based monolayers were deposited in King Hammurabi's time (~1800 BC, Mesopotamia); modern experiments were carried out much later by Ben Franklin, Lord Rayleigh, and Irving Langmuir. Although there is forensic archeological evidence for electroplating as early as the first few centuries BC, no written evidence survived. The earliest published electroplating experiments were ~1800 AD following the invention of the dc electrochemical battery by Volta. Chemical vapor deposition (CVD) of metal films was reported in 1649. Sols were produced in the mid-1850s (Faraday) and sol-gel films synthesized in 1885.

Vapor phase film growth including sputter deposition (Grove, 1852), arc deposition ("deflagration," Faraday, 1857), atmospheric plasmas (Siemens, 1857), plasma-enhanced CVD (1869, Berthelot), and evaporation (Stefan, Hertz, and Knudsen, 1873-1915) all had to wait for the invention of vacuum pumps whose history ranges from ~1650 for mechanical pumps through ~1865 for mercury pumps that could produce ballistic pressures in small systems. The development of the science of crystallography, leading to Miller indices (1839) for describing orientation and epitaxial relationships in modern thin film technology, was already well advanced by the 1780s. The starting point for the development of heterogeneous thin film nucleation theory was provided by Thomas Young (contact angle equation) in 1805.

While an historical road map tracing the progress of thin film technology is interesting in itself, the stories behind these developments are even more fascinating and provide insight into the evolution of scientific reasoning.