Formation of metal compound thin film and preparation of rubber composite material

Abstract

A thin film of a metal compound such as metal oxide, nitride and carbide is formed on a substrate by sputtering a target in vacuum in the presence of an inert gas and a reactive gas. From a curve of an input power supplied from a DC supply to the target versus an input voltage between the target and the substrate, a transition point of input power at which an abrupt change of the input voltage occurs is determined. The input power during sputtering is controlled using the transition point as a reference, thereby controlling the composition or physical properties of the thin film. When a cobalt oxide thin film is formed on a substrate in this way, rubber can be vulcanized thereto to form a firm bond.

1 . A method for forming a thin film of a metal compound on a substrate, comprising the step of sputtering a target of a corresponding metal or metal compound in the presence of an inert gas and a reactive gas capable of reacting with atoms sputtered from said target to form the metal compound, said method further comprising the steps of: 
 previously determining from the relationship of an input power supplied from a DC supply to said target to an input voltage between said target and said substrate during provisional sputtering at a predetermined vacuum and in a predetermined ratio of the reactive gas to the inert gas, a transition point of input power at which an abrupt change of the input voltage occurs, and    controlling the input power during sputtering so as to be below or at least the transition point, thereby controlling the composition or physical properties of the metal compound thin film.    
     
     
         2 . A method for forming a thin film of a metal oxide represented by MeO x  wherein Me is a metal atom on a substrate, comprising the step of sputtering a target of a corresponding metal or metal oxide in the presence of an inert gas and a gas having molecular oxygen, said method further comprising the steps of: 
 previously determining from the relationship of an input power supplied from a DC supply to said target to an input voltage between said target and said substrate during provisional sputtering at a predetermined vacuum and in a predetermined ratio of the oxygen-bearing gas to the inert gas, a transition point of input power at which an abrupt change of the input voltage occurs, and    controlling the input power during sputtering so as to be below or at least the transition point, thereby controlling the value of x in MeO x .    
     
     
         3 . The method of  claim 2  wherein Me is cobalt and the step of controlling the input power during sputtering is to control the input power so as to be at least the transition point.  
     
     
         4 . A method for forming a thin film of a metal nitride represented by MeN x  wherein Me is a metal atom on a substrate, comprising the step of sputtering a target of a corresponding metal or metal nitride in the presence of an inert gas and a gas having molecular nitrogen, said method further comprising the steps of: 
 previously determining from the relationship of an input power supplied from a DC supply to said target to an input voltage between said target and said substrate during provisional sputtering at a predetermined vacuum and in a predetermined ratio of the nitrogen-bearing gas to the inert gas, a transition point of input power at which an abrupt change of the input voltage occurs, and    controlling the input power during sputtering so as to be below or at least the transition point, thereby controlling the value of x in MeN x .    
     
     
         5 . A method for forming a thin film of a metal carbide represented by MeC x  wherein Me is a metal atom on a substrate, comprising the step of sputtering a target of a corresponding metal or metal carbide in the presence of an inert gas and a gas having molecular carbon, said method further comprising the steps of: 
 previously determining from the relationship of an input power supplied from a DC supply to said target to an input voltage between said target and said substrate during provisional sputtering at a predetermined vacuum and in a predetermined ratio of the nitrogen-bearing gas to the inert gas, a transition point of input power at which an abrupt change of the input voltage occurs, and    controlling the input power during sputtering so as to be below or at least the transition point, thereby controlling the value of x in MeC x .    
     
     
         6 . A method for preparing a rubber composite material comprising the steps of 
 forming a thin film of cobalt oxide on a substrate,    forming a rubber composition on the thin film, and    vulcanizing the rubber composition,    said step of forming a thin film of cobalt oxide comprising sputtering a target of cobalt in the presence of an inert gas and a gas having molecular oxygen with an input power which is at least the transition point at which an input voltage between the target and the substrate abruptly rises when an input power is supplied to the target from a DC supply.