Advances in RF Glow Discharge Optical Emission Spectrometry Characterization of Intrinsic and Boron-Doped Diamond Coatings

Abstract

Accurate determination of the effective doping range within diamond thin films is important for fine-tuning of electrical conductivity. Nevertheless, it is not easily attainable by the commonly adopted techniques. In this work, pulsed RF glow discharge optical emission spectrometry (GD-OES) combined with ultrafast sputtering (UFS) is applied for the first time to acquire elemental depth profiles of intrinsic diamond coatings and boron content bulk distribution in films. The GD-OES practical advances presented here enabled quick elemental profiling with noteworthy depth resolution and determination of the film interfaces. The erosion rates and layer thicknesses were measured using differential interferometric profiling (DIP), demonstrating a close correlation between the coating thickness and the carbon/hydrogen gas ratio. Moreover, DIP and the adopted semiquantification methodology revealed a nonhomogeneous bulk distribution of boron within the diamond crystalline structure, i.e., boron doping is both substitutional and interstitial within the diamond framework. DIP measurements also showed that effective boron doping is not linearly correlated to the increasing content introduced into the diamond coating. This is a finding well supported by X-ray diffraction (XRD) Rietveld refinement and X-ray photoelectron spectroscopy (XPS). This work demonstrates the advantage of applying advanced GD-OES operation modes due to its ease of use, affordability, accuracy, and high-speed depth profile analysis capability.

In-house vs. commercial boron-doped diamond electrodes for electrochemical degradation of water pollutants: A critical review

“…Nevertheless, effective doping is not linear since boron does not homogeneously incorporate diamond, being simultaneously substitutional and interstitially distributed within the crystalline framework. Thus, effective boron doping does not linearly increase with the boost of boron concentration in the CVD feed gas (Sharma et al, 2022). Boron preferentially incorporates the (111) diamond facets compared to (100) facets (Spitsyn et al, 1981;Larsson, 2020).…”

“…First, the design and working conditions of the adopted CVD technique can vary widely: the deposition method (hot-filament -HFCVD, or microwave plasma -MPCVD); the experimental deposition parameters (CH 4 /H 2 ratio, pressure, substrate temperature, boron doping source, [B]/[C] ratio); and the substrate material and its prior preparation (Gracio et al, 2010;May et al, 2011). Altogether, these parameters will influence the final physicochemical properties of the BDD electrode, such as sp 3 / sp 2 ratio, effective boron doping level, grain size, film thickness, electrical conductivity, electrochemical potential window, oxygen evolution potential (OEP), electron transfer rate, surface roughness, and surface termination (May et al, 2011;Salgueiredo et al, 2011;Huang et al, 2021;Sharma et al, 2022).…”

“…It includes secondary ion mass spectrometry (SIMS), X-ray photoelectron spectroscopy (XPS), electron energy-loss spectroscopy (EELS), and neutron depth profile (NDP). However, these methods are time-consuming, expensive, and difficult to apply, especially when a full depth analysis of boron distribution within the diamond lattice is desired (Sharma et al, 2022). Recently, pulsed RF glow discharge optical emission spectroscopy (GDOES) has been used to semi-quantify boron doping levels, and it was demonstrated that the technique provides high-speed depth profiles (Sharma et al, 2022).…”

“…However, these methods are time-consuming, expensive, and difficult to apply, especially when a full depth analysis of boron distribution within the diamond lattice is desired (Sharma et al, 2022). Recently, pulsed RF glow discharge optical emission spectroscopy (GDOES) has been used to semi-quantify boron doping levels, and it was demonstrated that the technique provides high-speed depth profiles (Sharma et al, 2022). In the case of heavily doped BDD films, many authors use a non-destructive and contactless measurement using Raman spectroscopy data to estimate the boron doping concentration.…”

Effect of Boron Doping Concentration on the Wettability and Surface Free Energy of Polycrystalline Boron-Doped Diamond Film

“…Most of these methods are empirical and semi-empirical and lack a physical basis; therefore, the applicability and accuracy of a single approach is insufficient. Owing to the excellent inherent properties of diamonds and high electrical conductivity, polycrystalline boron-doped diamond (PBDD) films have been widely used in many fields, including those related to coating materials [20], electrochemical application [21], sensing devices for medical applications [22,23], semiconductor devices [24], micro-electromechanical systems (MEMS) [25], photoelectrocatalysis [26], and supercapacitors [27]. To the best of our knowledge, studies on the wettability and SFE of PBDD films are lacking.…”