Local impedance imaging of boron-doped polycrystalline diamond thin films

• Published in: Applied physics letters Vol. 105; no. 13
• Main Authors: Zieliński, A., Bogdanowicz, R., Ryl, J., Burczyk, L., Darowicki, K.
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 29-09-2014
• Subjects: Applied physics; ATOMS; Boron; BORON ADDITIONS; Bulk modulus; CHEMICAL VAPOR DEPOSITION; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CRYSTAL DEFECTS; Crystallites; Diamond films; DIAMONDS; DISTRIBUTION; DOPED MATERIALS; ELECTRODES; GRAIN BOUNDARIES; IMPEDANCE; Microwave plasmas; MICROWAVE RADIATION; PLASMA; Plasma enhanced chemical vapor deposition; Polycrystalline diamond; POLYCRYSTALS; Resistance; RESOLUTION; SILICON; Silicon substrates; SUBSTRATES; THIN FILMS
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.4897346

Local impedance imaging (LII) was used to visualise surficial deviations of AC impedances in polycrystalline boron-doped diamond (BDD). The BDD thin film electrodes were deposited onto the highly doped silicon substrates via microwave plasma-enhanced CVD. The studied boron dopant concentrations, controlled by the [B]/[C] ratio in plasma, ranged from 1 × 1016 to 2 × 1021 atoms cm−3. The BDD films displayed microcrystalline structure, while the average size of crystallites decreased from 1 to 0.7 μm with increasing [B]/[C] ratios. The application of LII enabled a direct and high-resolution investigation of local distribution of impedance characteristics within the individual grains of BDD. Such an approach resulted in greater understanding of the microstructural control of properties at the grain level. We propose that the obtained surficial variation of impedance is correlated to the areas of high conductance which have been observed at the grain boundaries by using LII. We also postulate that the origin of high conductivity is due to either preferential boron accumulation, the presence of defects, or sp2 regions in the intragrain regions. The impedance modulus recorded by LII was in full agreement with the bulk impedance measurements. Both variables showed a decreasing trend with increasing [B]/[C] ratios, which is consistent with higher boron incorporation into BDD film.