Synthesis and Properties of Electrically Conductive/Nitrogen Grain Boundaries Incorporated Ultrananocrystalline Diamond (N-UNCD) Thin Films Grown by Microwave Plasma Chemical Vapor Deposition (MPCVD)

Michelle Salgado-Meza,Pablo Tirado-Cantú,Eliel Eduardo Montijo-Valenzuela,Rafael García-Gutiérrez,Guillermo Martínez-Rodríguez

doi:10.3390/app11188443

Abstract

Research and development have been performed to investigate the effect of total pressure and microwave power on the electrical conductivity of nitrogen (N) atoms’ grain boundaries incorporated ultrananocrystalline diamond (N-UNCD) films grown by microwave plasma chemical vapor deposition (MPCVD). Insertion of N atoms into the UNCD film’s grain boundaries induces N atoms chemical reaction with C-atoms dangling bonds, resulting in release of electrons, which induce electrical conductivity. Four-point probe electrical measurements show that the highest electrically conductive N-UNCD films, produced until now, exhibit electrical resistivity of ~1 Ohm.cm, which is orders of magnitude lower than the ≥106 Ohm.cm for undoped ultrananocrystalline diamond (UNCD) films. X-ray diffraction analysis and Raman spectroscopy revealed that the growth of the N-UNCD films by MPCVD do not produce graphite phase but only crystalline nanodiamond grains. X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of nitrogen (N) in the N-UNCD films and the high conductivity (no electrical charging is observed during XPS analysis) shown in electrical measurements.

Highlights

The physics and applications of ultra-nanocrystalline diamond (UNCD) films have been and are currently being investigated due to their unique combination of properties such as: high wear resistance [1], highest hardness relative to any other films [1], lowest friction coefficient [1] compared with metal and ceramic coatings chemical inertness to corrosion [1], negative electron affinity low work function for electron emission [1], high electrical conductivity via boron (B) atoms doping of UNCD producing B-UNCD films [2,3], N atom insertion into grain boundaries of UNCD films, producing the N-grain boundary incorporated ultrananocrystalline diamond (N-UNCD) films, as previously demonstrated by different groups worldwide experimentally [4,5,6,7,8], and theoretically [9]
The R&D described in this paper focused on exploring the effect of total pressure and microwave power on the electrical conductivity of N-UNCD films grown by microwave plasma chemical vapor deposition (MPCVD) in order to maximize the electrical conductivity of these films
The N-UNCD films were characterized by X-ray diffraction (XRD), using a Rigaku diffractometer (Ultima III, Cu Kα radiation, 1.524 A), scanning electron microscopy (SEM, Zeiss- SUPRA-40) -Thornwood-New York, X-ray photoelectron spectroscopy (XPS-PHI 5000 Versa Probe II-ULVAC), and, Raman spectroscopy (Thermo Scientific-DXR, 532 nm wavelength LASER Beam)

Summary

Introduction

The physics and applications of ultra-nanocrystalline diamond (UNCD) films have been and are currently being investigated due to their unique combination of properties such as: high wear resistance [1], highest hardness relative to any other films [1], lowest friction coefficient [1] compared with metal and ceramic coatings chemical inertness to corrosion [1], negative electron affinity low work function for electron emission [1], high electrical conductivity via boron (B) atoms doping of UNCD producing B-UNCD films [2,3], N atom insertion into grain boundaries of UNCD films, producing the N-grain boundary incorporated ultrananocrystalline diamond (N-UNCD) films, as previously demonstrated by different groups worldwide experimentally [4,5,6,7,8], and theoretically [9]. The R&D described in this paper focused on exploring the effect of total pressure and microwave power on the electrical conductivity of N-UNCD films grown by microwave plasma chemical vapor deposition (MPCVD) in order to maximize the electrical conductivity of these films.

Methods

Results

Discussion

Conclusion