Thin-Film Technology Of The Ancient World

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Artists and craftsmen more than 2,000 years ago developed thin-film coating technology unrivaled even by today’s standards for producing DVDs, solar cells, electronic devices and other products. Understanding these sophisticated metal-plating techniques from ancient times, described in the ACS journal Accounts of Chemical Research, could help preserve priceless artistic and other treasures from the past.

Gabriel Maria Ingo and colleagues point out that scientists have made good progress in understanding the chemistry of many ancient artistic and other artifacts — crucial to preserve them for future generations. Big gaps in knowledge remained, however, about how gilders in the Dark Ages and other periods applied such lustrous, impressively uniform films of gold or silver to intricate objects. Ingo’s team set out to apply the newest analytical techniques to uncover the ancients’ artistic secrets.

They discovered that gold- and silversmiths 2,000 years ago developed a variety of techniques, including using mercury like a glue to apply thin films of metals to statues and other objects. Sometimes, the technology was used to apply real gold and silver. It also was used fraudulently, to make cheap metal statues that look like solid gold or silver. The scientists say that their findings confirm “the high level of competence reached by the artists and craftsmen of these ancient periods who produced objects of an artistic quality that could not be bettered in ancient times and has not yet been reached in modern ones.” Read More

Sputtering Targets: Depositing Thin Films

Sputtering is a unique and repeatable process and has the ability to deposit thin films from a range of materials on to different shapes and sizes of substrates. The process can be upgraded from research and development projects to manufacturing of batches involving medium to large substrate areas.

In order to realize efficient momentum, transfer projectile mass must be able to match target mass. Therefore, for sputtering heavy elements xenon or krypton is used and for light elements neon is utilized. Generally, sputtering gas is an inert gas, such as argon.

Normally, reactive gases are utilized for sputtering compounds. The chemical reaction can take place on the substrate or on the target surface depending on the parameters of the process. These parameters make sputter deposition a challenging process, but nevertheless provide experts a greater level of control over the microstructure and growth of the film.

In order to obtain the required characteristics in a sputter deposited thin film, the production process utilized to build the sputtering target can be of significant importance. Regardless of the fact that the target material has an element, mixture of elements, compound, or alloys, the process undertaken to create that defined material, which is ideal for sputtering thin films of uniform quality, is equally important as the deposition run parameters perfected by scientists and engineers dealing in thin film processes.

Sputtering Targets and Sputtered Films

Sputtering is one of the most popular technologies for deposition of thin films. Although sputtering was first developed about 200 years ago, since World War II it has become increasingly important for the creation of innovative devices, becoming fundamental in sustaining the growing demand for semiconductor circuits and other electronic devices.

Sputtering targets have found increasing penetration not only in electronics, but also in sectors such as mechanical/chemical, energy, optical coating, and life science, among others.

Although for decades sputtering was primarily used in microelectronics for fabrication of semiconductor devices, in recent years, as the semiconductor industry transitions to new processes that allow for the fabrication of thin films below 20 nm, sputtering has found alternative sources of demand in other industry segments such as flat panel displays and solar cell manufacturing.

In fact, over time the availability of sputtering materials has expanded to meet the requirements of the most varied applications within the electronics, mechanical/chemical, energy, optical coatings, life science, and food packaging sectors. Read More

Novel Technologies to be Developed for Thin-Film Deposition

A three-year project awarded by the Defense Advanced Research Projects Agency to develop novel technologies for depositing thin films is underway.

The contract award is under DARPA’s Local Control of Materials Synthesis (LoCo) program, which is investigating non-thermal approaches for depositing thin-film coatings onto the surfaces of a variety of materials. The objective of the program is to overcome the reliance on high-thermal energy input by examining the process of thin-film deposition at the molecular component level in areas such as reactant flux, surface mobility and reaction energy, among others.

Many current high-temperature deposition processes cannot be used on military vehicles and other equipment because they exceed the temperature limit of the material. The LoCo program will attempt to create new, low-temperature deposition processes and a new range of coating-substrate pairings to improve the surface properties of materials used in a wide range of defense technologies including rotor blades, infrared missile domes and photovoltaics, among others. Read More

KAMIS manufactures sputtering targets for all sputtering systems in pure metals, alloys, and ceramic materials. 

The Vacuum Process of Thin Film Deposition

The vacuum process of thin film deposition involves the application of coatings of pure materials over the surface of varied and differing objects. The thickness of coatings or films typically possess a range of microns and angstroms and can be of single material or a layered structure of multiple materials. Using quartz crystal monitoring, there are basic principles used to control the thickness and rate of thin film deposition.

The key class of deposition methods is evaporation which involes heating a solid material within a high vacuum chamber in which vapor pressure is produced. A relatively low vapor pressure is adequate to raise a vapor cloud within the vacuum chamber, which is then condensed over surfaces as a coating or film.

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Thin Film Vacuum Coating on Flat Substrates

Vision Flat is an international technology and networking event that celebrates twenty years of research and development in the field of thin-film vacuum coating on flat substrates at the Fraunhofer FEP.

Representatives of leading companies, Corning Inc., Saint-Gobain Glass, Schott AG and experts in this field will highlight recent technological achievements and provide an outlook on future trends. New smart products and the global increasing demand for transparent architecture are posing new challenges to the fabrication and handling of flat materials such as glass, flexible glass and polymers.

The technology session will cover the aspects of large-area, homogeneous, dynamic layer deposition, up-scaling of coating processes, in-line process monitoring, deposition of layer systems via sputtering for architectural glazing, lighting, automotive applications and optics. Read More

Sputtering for Thin Film Deposits

Sputtering process is used in a variety of applications such as flat panel displays, optical discs, automotive and architectural glass, web coating, hard coatings, optical communications, solar cells, semiconductors, magnetic data storage devices, electron microscopy, and decorative applications.

Typical materials used in these applications are Copper, Chromium, Chromium-Molybdenum, Aluminium, Titanium, Aluminium-Titanium, Tungsten, Nickel, Silicon, Indium and Silver, amongst others.

Sputtering process can be used for depositing thin films from a wide range of materials on to different substrates. Although process parameters make sputtering a complex process, they allow a greater degree of control over the film’s growth and structure.

Gold Coating is a Thin Film of Gold Deposited Onto a Substrate

A gold coating is a very thin film of gold deposited onto a supporting substrate. This serves as a very useful substrate in the life science academia & industrial markets.

  • Typical characteristics of gold surfaces include:
  • Good resistance to oxidation
  • Inert surface for use with biological experimentation
  • Good conductor of electricity
  • Ultra smooth surfaces can be prepared
  • Easily forms thiol chemistry self-assembled monolayers (SAM)

Glossary of Terms

  • Nanometer (nm): 1×10-9 m
  • Ångström (Å): 0.1 nm
  • E-beam Evaporation: A physical vapor deposition technique used for thin film coatings.
  • Adhesion Layer: A thin layer deposited for improving the adhesion of gold on to the substrate (material to be coated).
  • Roughness: A measure of surface smoothness.
  • Grain Size: The size of gold grains present on the surface. Grain size has an effect on the roughness of the gold surface.
  • Self Assembled Monolayers(SAM): Surfaces consisting of a single layer of molecules on a substrate, prepared by adding a solution of the desired molecule onto the substrate surface and washing off the excess.

Physical vapor deposition (PVD) techniques are commonly used for depositing metal thin films onto a surface.

Analyzing Thin Metal Films

Sputtered Neutral Mass Spectrometry is perfect for analyzing thin metal films where composition, thickness and interface condition can be determined. The example presented here, shows a magnetic film stack comprising Cr, Ni, Cu and Fe. Of the different methods of data storage, magnetic hard discs still offer highly economic means for high density rapid access. The continual move towards more and more compact read/write heads and more closely spaced data tracks has lead to a considerable development of magnetic materials and structures for this demanding application. Analysis of the metallic layer structures used in magnetic data storage is vital for both development and quality management with secondary ion mass spectrometry (SIMS) and sputtered neutral mass spectrometry (SNMS) offering information on minor and major element composition respectively.


Both SIMS and SNMS use a concentrated, mono- energetic, chemically pure ion beam of typically 1-10 keV to sputter erode the surface under study. A small fraction of the sputtered material gets ionized due to the sputtering process itself and in SIMS, it is these ions that offer the sensitive information for which the technique is known. Being a mass spectrometry technique, all elements and isotopes may be detected, and in favorable conditions the detection limit can be in the low ppb region. However, because the ionization mechanism for SIMS takes place at the sample surface, it is very much dependent on the local chemistry and the ionized fraction can vary by several orders of magnitude. This makes SIMS ideal for trace analysis in materials of known matrix but quantification in materials of changing matrix can be complicated. SNMS overcomes the “matrix effect” by separating the sputtering and ionization events.

New Sputtering Target Innovations

Magnetron sputtering was initially developed using metal or alloy targets with materials having high electrical conductivity (e.g., Al, Ag, Au, Cu, Ti, Mo, etc.). In order to achieve acceptable deposition rates, the target material needed to be electrically and thermally conductive. Ceramic targets were developed for transparent conductive oxides (TCOs) and usually consisted of films made from compositions of ZnO:Al2O3 (2% wt) or In2O3:SnO2 (10% wt). However, as the name implies, the materials were fairly conductive and were suited for DC magnetron sputtering.

Pulsed-DC and RF magnetron sputtering allows for the deposition of materials with poor electrical conductivity. Semiconductor materials with better electrical conductivity can be sputtered with pulsed-DC power supplies, while insulating materials (mainly ceramics) require RF sputtering. The deposition rates for RF sputtering are generally much lower than with pulsed-DC. Also, pulsed-DC sputtering has a lower deposition rate than DC sputtering. New applications in photovoltaic, thermoelectric, storage, and semiconductor markets are spurring innovation in ceramic and semiconductor sputtering targets.

DC sputtering with metallic targets has fewer process problems since the metals are ductile and the materials feature high conductivity. Conversely, semiconductor and ceramic targets are more prone to process difficulties due to the brittle nature of the materials and the poor electrical and thermal conductivities. In order to achieve consistent sputtering over the life of the target, it is essential to have a well-sintered target material with high density. Voids and cracks in the material can propagate and lead to sputtering problems such as arcing, target cracking, and particle generation. Read More