Direct imaging of boron segregation at dislocations in B:diamond heteroepitaxial films.

S. Turner,S. Korneychuck,A. F. Sartori,H. Idrissi,G. Van Tendeloo,Y.-G. Lu,J. Verbeeck,M. Schreck

doi:10.1039/c5nr07535a

Abstract

A thin film of heavily B-doped diamond has been grown epitaxially by microwave plasma chemical vapor deposition on an undoped diamond layer, on top of a Ir/YSZ/Si(001) substrate stack, to study the boron segregation and boron environment at the dislocations present in the film. The density and nature of the dislocations were investigated by conventional and weak-beam dark-field transmission electron microscopy techniques, revealing the presence of two types of dislocations: edge and mixed-type 45° dislocations. The presence and distribution of B in the sample was studied using annular dark-field scanning transmission electron microscopy and spatially resolved electron energy-loss spectroscopy. Using these techniques, a segregation of B at the dislocations in the film is evidenced, which is shown to be intermittent along the dislocation. A single edge-type dislocation was selected to study the distribution of the boron surrounding the dislocation core. By imaging this defect at atomic resolution, the boron is revealed to segregate towards the tensile strain field surrounding the edge-type dislocations. An investigation of the fine structure of the B-K edge at the dislocation core shows that the boron is partially substitutionally incorporated into the diamond lattice and partially present in a lower coordination (sp(2)-like hybridization).

Highlights

Single crystal diamond is a material with extreme electrical and thermal properties which make it very desirable for highend applications, such as radiation detection,[1,2] electrochemical analysis,[3] high power high frequency switching and rectifying,[4] deep UV light emission,[5] etc. Many of these applications require controlled semiconducting properties, which nowadays are achievable in situ during microwave plasma chemical vapor deposition (MWPCVD) by adding boron or phosphorus precursors to the gas phase to promote, respectively, p-type or n-type conductivity by the substitutional incorporation of dopants into the diamond lattice
After characterization of the dislocations in the film, the presence and distribution of B in the sample was studied using a combination of annular dark-field scanning transmission electron microscopy ((HR)ADF-STEM) and spatially resolved electron energy-loss spectroscopy (STEM-EELS), performed on a state-of-the-art aberration corrected TEM instrument
A thin film of heavily B-doped diamond has been grown by MPCVD on an un-doped diamond layer, on top of an Ir/yttria-stabilized zirconia (YSZ)/Si(001) substrate stack

Summary

Introduction

Single crystal diamond is a material with extreme electrical and thermal properties which make it very desirable for highend applications, such as radiation detection,[1,2] electrochemical analysis,[3] high power high frequency switching and rectifying,[4] deep UV light emission,[5] etc. After characterization of the dislocations in the film, the presence and distribution of B in the sample was studied using a combination of annular dark-field (high resolution) scanning transmission electron microscopy ((HR)ADF-STEM) and spatially resolved electron energy-loss spectroscopy (STEM-EELS), performed on a state-of-the-art aberration corrected TEM instrument.

Results

Conclusion