Current status of R&D in Frontier carbon Technology (FCT) project – Electrically functional materials

K. Kobashi

FCT Project/ JFCC

Center for Advanced Research Projects, 6F, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan

Abstract

The R&D subjects in the Electrically Functional Group of the FCT Project at the Central Research Laboratory (CRL) in Osaka University are focused on diamond. They consist of (1) morphology control of diamond films grown by a 60 kW, 915 MHz microwave plasma CVD reactor, (2) characteristics control of field emission from diamond, and (3) fabrication of sharp emitter tips. Both Sumitomo Electric (SEI) and Kobe Steel (KSL) have Satellite Research Labs in the companies and are associated with the CRL: (4) SEI develops a new CVD reactor to grow large single crystal diamond with a low density of defects, while (5) KSL undertakes heteroepitaxial growth technology development of diamond films on Pt.

Since the start of the Project, there are remarkable achievements in each subject, and this paper will present the latest results in the Group, which will be very beneficial for the conference attendees to determine their R&D directions.

(1) A 60-kW, 915-MHz microwave plasma CVD reactor was installed by ASTeX/Seki Technotron. Usually, the reactor was operated using CH₄/H₂ under the conditions of {60 kW, 100 Torr, 800 - 900 °C}. The substrate is a Si plate with a thickness of 12 mm. The plasma generation is very smooth and stable, and so far there was no serious troubles in the reactor. To control the film morphology, we have mainly changed the CH₄ concentration c and the substrate temperature T_s that is a function of gas pressure and microwave power. It was found that the domains of <100> and <111> growth in the c – T_s plane are located in the reversed positions of those obtained by a 1.5 kW reactor. The mechanism is currently under study.

(2) Field emission from diamond particles that have been sprayed on a Mo substrate followed by diamond CVD for 10 – 15 min were studied by Scanning Tunneling Microscopy (STM) and Field Emission Electron Microscopy (FEEM) using an Omicron system. The emission points were identified, and more detailed emission mechanism is under study.

(3) By using a combination of CVD and plasma etching, sharp tips were fabricated on single crystal diamond surfaces. There were two major results: the first is a sharp tip made by an edge of merged crystal faces, and the second is a needle-like tip made by an anisotropic etching through a circular mask. It is remarkable that the base surface in the latter case is very smooth.

(4) SEI designed a 915 MHz CVD reactor that has a uniform distribution of the electric field at the substrate position. It was successful to make a fully coalesced plate from 16 pieces of 3 mm x 3 mm single crystal diamond.

(5) KSL was successful in depositing coalesced diamond film on Pt(111) of 11 mmf, where the local areas on the film are fully coalesced, showing large bunched steps.

It is expected that this presentation will give useful information on CVD diamond research toward practial applications.

This work was supported by FCT Project, which was consigned to JFCC by NEDO.

Keywords: large-area deposition, field emission, emitter fabrication

Koji Kobashi

FCT/JFCC

Center for Advanced Research Projects (6F), Osaka University

2-1 Yamada-oka, Suita, Osaka 565-0871, Japan

k-kobashi@rd.kcrl.kobelco.co.jp

Fax: +81-6-6879-4147, Phone: +81-6-6879-4146