HOMOEPITAXIAL DIAMOND GROWTH AT HIGH AND LOW TEMPERATURES: DESIGNER DIAMONDS TO LARGE CRYSTALS

Yogesh K. Vohra

Department of Physics

University of Alabama at Birmingham (UAB)

Birmingham, AL 35294-1170, USA

E-mail: ykvohra@uab.edu

ABSTRACT

This abstract will cover recent advances in the homoepitaxial diamond growth by microwave plasma chemical vapor deposition. We will explore two growth regimes, one at the temperatures in the range of 1200 to 1300 ^oC and another one at temperatures near 800 ^oC. In a collaborative project with Lawrence Livermore National Laboratory, high quality single crystalline diamond films have been grown on diamond anvils as substrates with encapsulated metal microcircuits to fabricate “Designer Diamond Anvils” for applications in high-pressure science and technology.

Designer Diamond in reflected light showing exposed microprobes on the surface

Designer diamond in transmitted light showing eight buried microprobes

3.6 mm x 3.8 mm x 2mm homoepitaxially grown diamond crystal in a 6kW microwave plasma CVD system on a type Ib yellow substrate

Single crystal diamond can be grown homoepitaxially at high temperatures of 1300 ^oC with growth rate approaching 30-40 microns/hour with methane/hydrogen/nitrogen chemistry on a type Ib substrates. Large diamond crystals up to 4 mm can be grown but the edge of crystals show multiple twinning and limit the ultimate size of these diamonds. Alternative, low temperature chemistry of methane/hydrogen/oxygen has been probed to grow large crystals starting with type IIa diamond substrates. The crystalline quality of the homoepitaxial diamond crystals was evaluated by the micro-Raman spectroscopy and single crystal x-ray diffraction using the rocking curve measurements of (400) diffraction peak from diamond. Future research directions in large area homoepitaxial diamond growth will be discussed.

We acknowledge support from the National Science Foundation (NSF) under Grant No. 9704428 and support by the B-Division at the Lawrence Livermore National Laboratory (LLNL) under the auspices of the U.S. Department of Energy, under contract No. W-7405-ENG-48. Author would also like to acknowledge contributions from his coworkers Dr. Shane A. Catledge and Dr. Chih-Shiue Yan from UAB and Dr. Jagan Akella and Dr. Sam Weir from the Lawrence Livermore National Laboratory.

Keywords: homoepitaxy, designer diamonds, defects, twinning