Oriented Amorphous Carbon Film Conductivity
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Solution Overview
Problem
Amorphous carbon films exhibit limited improvement in electric conductivity due to the mixed presence of amorphous and crystal phases, which restricts their wider industrial applications.
Innovation Solution
An oriented amorphous carbon film with a high content of carbon having sp2 hybrid orbital (Csp2) and controlled nitrogen and hydrogen content, where (002) planes of graphite are oriented along the film thickness direction, is formed using the DC plasma CVD method with specific reaction gases and high voltage, maintaining an amorphous structure without long-distance order.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal is added to amorphous carbon to improve electric conductivity, then electric conductivity increases, but corrosion resistance and chemical stability deteriorate
Solution Approach 1:
The invention extracts and eliminates metal elements from the amorphous carbon film composition. Instead of adding metal to improve conductivity, the patent uses pure carbon with controlled sp2 bonding configuration (30-70 at%) to achieve conductivity while maintaining the inherent corrosion resistance and chemical stability of carbon materials.
Solution Approach 2:
The invention changes the bonding parameter of carbon atoms by controlling the sp2 bonding content to 30-70 at%. This parameter change enables the amorphous carbon film to achieve high electric conductivity through delocalized π electrons in sp2 bonds without requiring metal additives, thereby resolving the contradiction between conductivity and corrosion resistance.
2Reliability
If sp2-bonded crystals are increased to improve electric conductivity, then electric conductivity increases, but hardness and wear resistance decrease
Solution Approach 1:
The invention applies local quality by creating a heterogeneous structure where sp2-bonded regions (30-70 at%) provide conductivity pathways while sp3-bonded regions provide hardness and mechanical strength. This local differentiation of bonding types within the amorphous matrix allows simultaneous optimization of electrical and mechanical properties.
Solution Approach 2:
The invention creates a composite bonding structure combining sp2 and sp3 hybridized carbon in specific proportions. The sp2-rich domains provide electrical conductivity through π electron delocalization, while sp3-rich domains contribute to mechanical hardness, forming a composite material system at the atomic bonding level.
3Reliability
If continuous sp2-bonded crystals extend from substrate to surface to improve conductivity, then electric conductivity increases, but the amorphous structure is compromised
Solution Approach 1:
The invention applies partial action by introducing sp2-bonded crystal regions (30-70 at%) into the amorphous carbon matrix without achieving full crystallization. This partial crystalline phase provides sufficient conductivity pathways while the dominant amorphous matrix (30-70 at% sp3 bonding) maintains the desired structural characteristics, avoiding excessive crystallinity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The oriented amorphous carbon film achieves high electric conductivity, high film density, and enhanced mechanical properties, including corrosion resistance and hardness, making it suitable for conductive members in harsh environments.
Implementation Method 1
a method for forming the oriented amorphous carbon film on a surface of a substrate by direct current plasma CVD method
Implementation Method 2
direct current plasma CVD method, comprising: placing the substrate in a reaction vessel, introducing reaction gas comprising at least one kind of compound gas selected from the group consisting of gas of a carbocyclic compound containing carbon having an sp2 hybrid orbital and gas of an N-containing heterocyclic compound containing carbon having an sp2 hybrid orbital, and nitrogen and/or silicon, and nitrogen gas into the reaction vessel, and generating an electric discharge by applying a voltage of not less than 1500 V
Implementation Method 3
generating an electric discharge by applying a voltage of not less than 1500 V
Data Source
AI summary
The oriented amorphous carbon film contains C as a main component, 3 to 20 at. % of N, and more than 0 at. % and not more than 20 at. % of H, and when the total amount of the C is taken as 100 at. %, the amount of C having an sp2 hybrid orbital (Csp2) being not less than 70 at. % and less than 100 at. %, and (002) planes of graphite being oriented along a thickness direction. This film has a novel structure and exhibits a high electric conductivity. This film can be formed by DC plasma CVD method in which an electric discharge is generated by applying a voltage of not less than 1500 V to reaction gas including at least one kind of compound gas selected from gas of a carbocyclic compound containing Csp2 and gas of an N-containing heterocyclic compound containing Csp2, and nitrogen and/or silicon, and nitrogen gas.