Boron-doped ultrananocrystalline diamond synthesized with an H-rich/Ar-lean gas system

Abstract

This paper reports the recent development and applications of conductive borondoped ultrananocrystalline diamond (BD-UNCD). The authors have determined that BD-UNCD can be synthesized with an H-rich gaseous chemistry and a high CH 4 /H 2 ratio, which is opposite to previously reported methods with Ar-rich or H-rich gas compositions but utilizing very low CH 4 /H 2 ratio. The BD-UNCD has a resistivity as low as 0.01 ohm·cm, with low roughness (down to several nm) and a wide deposition temperature range (450-850¼C).The properties of this BD-UNCD were studied systematically using resistivity characterization, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and roughness measurements. Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy confirms that up to 97% of the UNCD is deposited as sp3 carbon.These series of measurements also reveal additional unique properties for this material, such as an ÒMÓ shape Raman signature, line-granular nano-cluster texture and high C-H bond surface content. A hypothesis is provided to explain why this new deposition strategy, with H-rich/Ar-free gas chemistry and CH 4 /H 2 ratio, is able to produce high sp3-content and/or 2 heavily doped UNCD. In addition, a few emerging applications for BD-UNCD in the field of atomic force microscopy, electrochemistry and biosensing are reviewed here.

The effect of electrode size and surface heterogeneity on electrochemical properties of ultrananocrystalline diamond microelectrode

“…The average roughness of the UNCD film was <10 nm rms based on AFM measurements (Digital Instruments, Santa Barbara, CA). For MCD films, the reactor setup and processes are similar to those reported previously by Hongjun et al [34] To keep the grain size larger in MCD films, the C/H gas ratio is maintained at or below 5%. [35] The MCD are grown at 800 C degree with average grain size 100 nm and film resistivity 0.04 ohm cm.…”

“…The two major peaks 1310-1355 and 1560 cm -1 represents a broad combination of D-band (disorganized graphite) and the diamond peak at 1332 cm -1 , and G-band (crystalline graphite), respectively. [34] AFM measurements showed a change in the surface morphology to a line-granular structure after the treatment (Figure 2b, d). This might be due to the selective chemical etching of GB, which reveals the line-granular grain structure.…”

“…Being corrosive, we expect BOE to alter the surface morphology/microstructure and introduce surface defects. Raman spectroscopy showed M-shaped Raman signature of UNCD [34] was preserved with no significant change in the intensity of the peaks after the BOE treatment ( Figure 2e). The Raman spectrum consists of peaks at 1150, 1310-1355, 1470 and 1560 cm -1 .…”

Diamond coated artificial cardiovascular devices

“…The reactor setup and seeding processes are similar to those reported previously [16]. High purity UNCD deposition uses an H-rich gas system with a CH4/H2 ratio as high as 10% employed, which was studied in a recent report [17]. The UNCD film thickness practiced for these parts is in the range of 1.5–2.5 µm.…”

Understanding the Atomic Scale Mechanisms that Control the Attainment of Ultralow Friction and Wear in Carbon-Based Materials

“…Boron-doping endows UNCD with electrical conductivity, which broadens its applications including for contact electrode applications, for example. Working with ADT, we developed and characterized a new version of boron-doped UNCD that could be grown at lower temperatures 27 . In collaboration with CCU, we have characterized the mechanical properties (modulus, hardness) of this new material (work still in process) and now plan to measure its wear behavior in comparison to conventional UNCD.…”