Dislocations, twins, and grain boundaries in CVD diamond thin films: Atomic structure and properties
- PDF / 8,077,477 Bytes
- 11 Pages / 593 x 841 pts Page_size
- 56 Downloads / 308 Views
and grain boundaries in CVD diamond thin films: Atomic structure and properties J. Narayan Journal of Materials Research / Volume 5 / Issue 11 / 1990, pp 2414 2423 DOI: 10.1557/JMR.1990.2414
Link to this article: http://journals.cambridge.org/abstract_S0884291400037304 How to cite this article: J. Narayan (1990). Dislocations, twins, and grain boundaries in CVD diamond thin films: Atomic structure and properties. Journal of Materials Research,5, pp 24142423 doi:10.1557/JMR.1990.2414 Request Permissions : Click here
Downloaded from http://journals.cambridge.org/JMR, IP address: 132.206.27.25 on 20 Aug 2012
Dislocations, twins, and grain boundaries in CVD diamond thin films: Atomic structure and properties J. Narayan Materials Science and Engineering Department, North Carolina State University, Raleigh, North Carolina 27695-7916 (Received 11 April 1990; accepted 25 July 1990)
We have used transmission electron microscopy techniques to study the nature of dislocations, stacking faults, twins, and grain boundaries in CVD (chemicalvapor-deposition) diamond thin films. Perfect a/2(110) and partial a/6(112) and a/3(lll) type dislocations are observed; the partial dislocations are also associated with twins and stacking faults. The most common defect in diamond thin films, particularly in (110) textured films, is 2 = 3 grain boundary or the primary twin. These twins in (110) textured films can lead to formation of fivefold microcrystallites. We have also investigated the splitting of 2 = 9 grain boundary (second order twin) into two X = 3 boundaries or primary twins via reaction 29 = 223. A rapid thermal annealing treatment has been shown to result in annealing of 2 = 3 boundaries and produce "defect-free" regions in thin films. A mechanism of annealing (removal) of 2 = 3 boundaries is discussed. Atomic structure and energetics of dislocations, twins, and grain boundaries are calculated using Tersoff potentials. The calculated atomic structure for 2 = 3 boundary is compared with high-resolution TEM images and a good agreement is obtained. These boundaries consist of periodic units of 5-7 rings which are similar to the core structure of 90° a/2(110){001} dislocations. The energy of the 5-7 rings in the grain boundaries is considerably lower, due to overlapping and strain cancellation effects, than that associated with single dislocations. The 5-7 ring energy and consequently the boundary energy increases as the overlapping effects decrease. An interesting analogy between the diamond and silicon results is drawn.
I. INTRODUCTION
Diamond thin films have been successfully grown by a variety of chemical deposition methods, including filament-assisted CVD, plasma (microwaves, rf, or dc) CVD, plasma jets and torches, and very recently combustion flames.1"7 For a recent review, it is suggested that the reader consult Refs. 8-10. Thin film growth has been found to be epitaxial only on diamond substrates with all three axes of the film having a definite orientation relationship with the underlying substrate. In other substr
Data Loading...
