| 초록 |
Single crystal diamond has excellent physical and chemical properties such as high hardness, high thermal conductivity, optical transmission from UV to IR and chemical inertness. In addition, diamond is well known as an electrical insulator with a resistivity of the order of 1016 Ω･cm. However, it was changed to the semiconductor by inclusion of dopant such as boron. Generally, diborane (B2H6) or trimethyl-boron {B(CH3)3} are used as dopant to synthesize boron-doped diamond. However, these dopants are toxic to humans. On the other hand, trimethyl-borate {B(OCH3)3} is safety, against to B2H6 or B(CH3)3. In this report, Homo-epitaxial growth of single crystal B-doped diamond on HPHT diamond substrates using mode-conversion type microwave plasma CVD was studied. The B-doped diamond layer was synthesized on single crystal diamond substrate using mode conversion type microwave plasma CVD apparatus. HPHT diamond substrate was made by high pressure high temperature method and had (1 0 0) facet of crystal orientation. Reaction gases were used CH4 (15 SCCM) and H2 (100 SCCM). Trimethyl-borate was used as a boron source. Vapor of trimethyl-borate was carried by H2 gas into the vacuum chamber with its flow rate of 3 SCCM. Pressure was 20.0 kPa and microwave power was 1.0 kW, respectively. Reaction time was 54 h. The surface and cross sectional morphologies of deposits were observed by SEM. Qualities of the deposits were estimated by Raman spectroscopy and Laue pattern. Electrical resistivities were measured by the four-point probe method. In the cross sectional SEM image after laser cutting, homo epitaxial layer of 0.1 mm thickness was observed. Raman spectra of the B-doped diamond growth layer, the broad peak at about 500, 1230 cm-1 and the weak peak at 1333 cm-1 were observed for each spectra. These peaks due to high concentration boron inclusions [1]. As a result of Laue pattern from deposits, Laue pattern wasn’t halo-pattern. As a result of the electrical resistivity measurements by the four-point probe method, the minimum electrical resistivitiy was 4.2×10-3 Ω･cm. As a conclusion, the single crystal B-doped diamond was fabricated on HTHP diamond substrate. In the Raman spectra of the film, the peaks caused high boron inclusion were observed. |
