Northwestern University

Ming-Show Wong

Scott A Barnett

William D Sproul

Xi Chu

Dong Li

Yip-Wah Chung

Anthony Lefkow

Yin-Wah Chung

Phillip Yashar

A method and apparatus for monitoring and controlling deposition of metal, insulating compounds or other compounds on a substrate by sputtering techniques includes maintaining pulsed, constant, direct current power to the target, sensing the voltage of the target material used in the process, simultaneously rapidly sensing the partial pressure of the reactive gas, and simultaneously biasing the substrate to activate the reactive gas or otherwise energizing the reactive gas in the vicinity of the substrate. Low temperature coating (eg., below 550.degree. C.) of compounds such as alumina is effected by introduction of an extra energy source such as a radio frequency coil to the sputtering system to enhance the ionization potential of the positive ions. The asymmetric direct current pulsed magnetron power source is coupled to the cathode, as well as the substrate to be coated. An apparatus for practicing the invention is also disclosed and examples of various oxide coatings using the method of the invention are disclosed. A multilayer coating of nanometer scale layers of yttrium oxide and zirconium oxide having increased hardness is disclosed.

Multilayer oxide coatings

The present invention provides a coated article comprising a substrate that can be non-crystalline or crystalline such as a polycrystalline engineering material, having advantageous mechanical properties and a superlattice-type protective composite coating on the substrate. The composite coating comprises a plurality of vapor deposited, ion bombarded, polycrystalline layers of different adjacent compositions formed one atop the other in lamellar manner. The polycrystalline layers have sufficiently thin individual layer thicknesses (e.g. not exceeding about 150 nanometers) and sufficiently distinct and different compositions proximate their interfaces despite being ion bombarded as to constitute superlattice layers that exhibit a collective hardness exceeding the hardness of any individual layer material in homogenous or bulk form. The composite coating is ion bombarded to an extent that the individual layers are substantially free of intragranular voids without adversely affecting the compositional modulation of the superlattice layers. Moreover, the composite coating can have planar or non-planar interlayer interfaces and still exhibit substantially improved hardness.

Polycrystalline supperlattice coated substrate and method/apparatus for

A composite material having high hardness comprises a carbon nitrogen compound, such as CN.sub.x where x is greater than 0.1 and up to 1.33, deposited on a metal or metal compound selected to promote deposition of substantially crystalline CN.sub.x. The carbon nitrogen compound is deposited on a crystal plane of the metal or metal compound sufficiently lattice-matched with a crystal plane of the carbon nitrogen compound that the carbon nitrogen compound is substantially crystalline. A plurality of layers of the compounds can be formed in alternating sequence to provide a multi-layered, superlattice coating having a coating hardness in the range of 45-55 GPa, which corresponds to the hardness of a BN coating and approaches that of a diamond coating.

Superhard composite materials including compounds of carbon and nitrogen

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Northbrook, IL, United States of America

Ming-Show Wong