Structural characterization of B-doped diamond nanoindentation tips
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Mark N. Lockrey and Matthew R. Phillips Microstructural Analysis Unit, University of Technology, Sydney, Broadway, New South Wales 2007, Australia
Ryan C. Major and Oden L. Warren Hysitron, Inc., Minneapolis, Minnesota 55344 (Received 19 July 2011; accepted 19 October 2011)
We report on the electrical and structural properties of boron-doped diamond tips commonly used for in-situ electromechanical testing during nanoindentation. The boron dopant environment, as evidenced by cathodoluminescence (CL) microscopy, revealed significantly different boron states within each tip. Characteristic emission bands of both electrically activated and nonelectrically activated boron centers were identified in all boron-doped tips. Surface CL mapping also revealed vastly different surface properties, confirming a high amount of nonelectrically activated boron clusters at the tip surface. Raman microspectroscopy analysis showed that structural characteristics at the atomic scale for boron-doped tips also differ significantly when compared to an undoped diamond tip. Furthermore, the active boron concentration, as inferred via the Raman analysis, varied greatly from tip-to-tip. It was found that tips (or tip areas) with low overall boron concentration have a higher number of electrically inactive boron, and thus non-Ohmic contacts were made when these tips contacted metallic substrates. Conversely, tips that have higher boron concentrations and a higher number of electrically active boron centers display Ohmic-like contacts. Our results demonstrate the necessity to understand and fully characterize the boron environments, boron concentrations, and atomic structure of the tips prior to performing in situ electromechanical experiments, particularly if quantitative electrical data are required.
I. INTRODUCTION
Knowledge of the physical properties of semiconductors, particularly the electrical response to an applied mechanical stimulus, is the foundation to present-day semiconductor technology. Furthermore, successful implementation of semiconductors into electronic, mechanical, magnetic, and optical devices necessitates a thorough understanding of both the electrical and mechanical properties. Recently, significant interest has grown in in-situ characterization of the electromechanical response of various semiconductor materials that undergo structural phase transformations (crystalline–crystalline or crystalline–amorphous) under extreme conditions such as pressure and/or temperature.1,2 Such investigations are a novel means to characterize the subtle differences in electrical conductivity, from an initialto-final phase, and to give valuable information on the transformation pathway of such materials. Nanoindentation is one such technique that can be easily used to both quantify and link the mechanical and electrical behavior of semiconductor materials and give significant insight into the a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2011.377 J. Mater. Res., Vol. 26, No. 24, Dec 28, 2011
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