It would be hard to imagine today's world without nanotechnology. Nanotechnology is an essential part of modern everyday life. Anything we use — from smartphones and solar panels to kitchen pans and drills — employs nanotechnology. Even bag of chips contains anticoagulant nanopowder to prevent sticking. We have surrounded ourselves with nanocoatings, nanopowders and nanostructures, but their production methods are largely outdated.
Probably the most used type of nanotechnology are nanocoatings. Every touchscreen we encounter has multiple nanocoatings — transparent conductive oxide that reacts to our touch, hard coating that protects it from scratches and adhesive coating that holds them together. Almost every part in a car has some kind of nanocoating: tribological coatings for moving parts to reduce wear and friction, anticorrosion coatings — you've guessed it — to prevent corrosion, thermal insulation coatings, thin-film sensors and many more. Even most common glasses have anti-reflection nanocoating. Nanocoatings are everywhere. But production technology we use is more than 40 years old. It's time for a new chapter in nanotechnology.
Physical vapor deposition (PVD) is first thing that comes to mind when you think about high quality coatings. PVD allows to design coatings layer-by-layer with the precision of several atomic layers. Future technologies will demand nanocoatings with complex and precise structure and the sole production method capable of achieving necessary quality on mass production level is PVD. There are various PVD methods — arc sputtering, electron beam deposition, pulsed laser deposition, evaporation — all with their advantages and limitations, but one method stands out as versatile and promising — magnetron sputtering.
Magnetron sputtering
Magnetron sputtering (MS) is a deposition technology that uses plasma which is generated and confined to a space above the material to be deposited. Ionized atoms of plasma bombard the surface of the material — so called "target" — which is eroded and ejected atoms of the material travel through the vacuum environment onto a substrate to form a thin film.
Magnetron sputter deposition does not require melting of the source material, leading to many advantages over other PVD technologies: first, nearly all solid materials can be deposited by magnetron sputtering regardless of their melting temperature; second, films of different alloys, compounds and multicomponent composites can be deposited as various materials can be used simultaneously, as well as reactive gasses can be added to the atmosphere; finally, magnetron sputtering is scalable and can be tailored to specific coating and substrate combination.
Recent advancements in high-power impulse magnetron sputtering (HIPIMS) improved sputtering process and coating properties even further, making it highly desirable for many applications. However, most common disadvantage of the magnetron sputtering — low coating deposition rate — in many areas inhibits technology transition to mass-production due to low cost efficiency. Main cause of slow coating deposition is low discharge power density — conventional magnetron sputtering operates at power density in the range 1 — 50 W/sq.cm, and, while HIPIMS peak power density can reach several kW/sq.cm, average power rarely exceeds 50 W/sq.cm resulting in low deposition rate of 1 — 2 microns per hour.
To overcome this disadvantage Naco Technologies developed High-speed ion plasma magnetron sputtering (HsIPMS) that can withstand average power densities much more than HIPIMS in continuous mode due to special design and effective cooling system. This leads to significant deposition rate increase up to 10 µm/h for composite and complex composition coatings, making magnetron sputtering technology feasible for mass-production in almost any area.
HsIPMS — future of PVD
High-speed ion plasma magnetron sputtering is the next generation PVD technology, that combines advantages of all other PVD technologies: it is as fast as arc sputtering, as precise as e-beam deposition, is more versatile than conventional magnetron sputtering and achieves higher film density than HIPIMS.
In addition, HsIPMS achieves unique effect — equalization of sputtering rates of different materials. Typically, under similar conditions, titanium coating would grow 4 times faster than carbon coating. But, by using mosaic targets (titanium target with carbon inserts) and high-speed magnetron sputtering it is possible to achieve same deposition rate of carbon and titanium under same conditions. As it was discovered by Prof. Valery Mitin, this effect of equalization of sputtering rates happens due to reimplantation of titanium ions into carbon inserts, therefore increasing carbon deposition rate. Similar effect was achieved in various other metals. This unique phenomenon allows for production of coatings with highly controlled chemical composition at increased deposition rates.
HsIPMS can be used on laboratory scale and can be easily scaled to mass production. It has already showed remarkable results — both in properties of produced coatings and manufacturing cost — in such areas as electrical insulation, corrosion and wear protection, friction reduction, and catalytic coatings for chemical reactors and fuel cells. Future technologies, especially in area of alternative energy, demand precise and superiors coatings and HsIPMS is the way to do it.