Apparatus for forming diamond film

An apparatus for forming a diamond film, comprising:

• a vacuum vessel the inside of which is maintained at a given degree of vacuum;
• a positive electrode and a negative electrode which are disposed opposite to each other inside the vacuum vessel;
• an arc discharge power supply which is electrically connected with the positive and negative electrodes to supply a given electric power into the space between the positive and negative electrodes to produce an arc discharge in the space;
• a gas supply means which supplies raw material gases including hydrogen and carbon containing gas into the arc discharge to produce a gas plasma and which blows this gas plasma against a substrate located downstream of the gas plasma;
• a third electrode disposed between the substrate and the region in which the gas plasma is produced;
• a plasma current power supply for passing an electrical current from the third electrode to the positive or negative electrode via the gas plasma;
• and
• a substrate potential-setting means which sets the potential of the substrate in such a way that the third electrode is placed at the same potential as the substrate or at a higher potential than the substrate, to inhibit flow of positive electrical current from the substrate to the third electrode.

An apparatus for forming a diamond film, comprising:

• a vacuum vessel the inside of which is maintained at a given degree of vacuum;
• a positive electrode and a negative electrode which are disposed opposite to each other inside the vacuum vessel;
• an arc discharge power supply which is electrically connected with the positive and negative electrodes to supply a given electric power into the space between the positive and negative electrodes to produce an arc discharge in the space;
• a gas supply means which supplies raw material gases including hydrogen and carbon containing gas into the arc discharge to produce a gas plasma;
• a gas plasma ejection means which narrows down the flow of the gas plasma and blows the gas plasma as a plasma jet against a substrate located downstream of the gas plasma;
• an annular positive electrode through which the plasma jet passes and which is disposed at or near the position where the plasma jet assumes its maximum diameter between the substrate and the region in which the gas plasma is produced, the inside diameter A of the annular positive electrode being so set that the relation A.ltoreq.5B holds, where B is the diameter of the restrictor of the gas plasma ejection means;
• a plasma current power supply for passing an electrical current from the annular positive electrode into the plasma jet to promote decomposition of the raw material gases;
• and
• a substrate potential-setting means which sets the potential of the substrate in such a way that the annular positive electrode is placed at the same potential as the substrate or at a higher potential than the substrate, to inhibit flow of positive electrical current from the substrate to the annular positive electrode.

An apparatus for forming a diamond film, comprising:

• a vacuum vessel the inside of which is maintained at a given degree of vacuum;
• a positive and a negative electrodes which are disposed opposite to each other inside the vacuum vessel;
• an arc discharge power supply which is electrically connected with the positive and negative electrodes to supply a given electric power into the space between the positive and negative electrodes to produce an arc discharge in the space;
• a gas supply means which supplies raw material gases including hydrogen and carbon containing gas into the arc discharge to produce a gas plasma and which blows this gas plasma against a substrate located downstream of the gas plasma;
• at least one, pair of opposite electrodes disposed on opposite sides of the flow of the gas plasma directed toward the substrate between the substrate and the region in which the gas plasma is produced;
• and
• a plasma current power supply which applies an electric field between the opposite electrodes to pass an electrical current through the gas plasma in a direction intersecting the flow of the gas plasma.