Role of oxygen additive on hydrogen impurity incorporation in nanocrystalline diamond films fabricated by microwave plasma chemical vapor deposition

Abstract

In this work, we study the influence of oxygen additive in the gas phase on hydrogen impurity incorporation into thick nanocrystalline diamond (NCD) films. Various diamond samples were grown on large silicon wafers of 5.08 cm diameter by adjusting the amount of oxygen and nitrogen additives into a conventional CH4/H2 plasma while keeping the other parameters constant using a 5‐kW microwave plasma‐assisted chemical vapor deposition (MPCVD) reactor. The morphology, crystalline quality, and hydrogen impurity content of the produced diamond samples were characterized using scanning electron microscopy, micro‐Raman spectroscopy, and Fourier transform infrared (FTIR) spectroscopy, respectively. The Raman and the FTIR spectra of the diamond samples indicate that on increasing the amount of oxygen additive in the gas phase, the crystalline quality of the NCD films is significantly enhanced, while their bonded hydrogen content decreases drastically. We conclude that a small amount of oxygen addition has an enhancement effect on the overall quality of diamond films ranging from polycrystalline to nanocrystalline in two ways: improving the diamond crystalline quality and suppressing hydrogen impurity incorporation.

High rate growth of nanocrystalline diamond films using high microwave power and pure nitrogen/methane/hydrogen plasma

“…This result not only further confirms that it is nitrogen (not oxygen) in air that has decisive role on formation of NCD, but also excludes the critical impact of oxygen on formation of NCD under the conditions employed here. This also further consolidates our previous results that a small amount of oxygen addition can enhance the quality of CVD diamond films and suppress hydrogen impurity incorporation [32], including NCD films grown with both nitrogen and oxygen addition [33]. The current experimental work can serve as a guide for the extension of the growth parameter windows for NCD growth with nitrogen addition, and benefit a systematic understanding of nitrogen effect on CVD diamond growth in order to achieve a complete understanding of the growth mechanism of NCD films or CVD diamonds.…”

Fast, Efficient Tailoring Growth of Nanocrystalline Diamond Films by Fine-Tuning of Gas-Phase Composition Using Microwave Plasma Chemical Vapor Deposition

“…Under typical base conditions used for high-quality MCD growth, the key functions of a small amount of O 2 addition on suppressing H impurity incorporation and improving quality of NCD films were illustrated when the total amount of N 2 and O 2 was fixed at 1 sccm [ 41 ] and by stabilizing a certain orientation or texture such as <100> orientation when an equal amount of N 2 and O 2 addition was employed [ 29 ]…”

“…Under typical base conditions used for high-quality MCD growth, the key functions of a small amount of O 2 addition on suppressing H impurity incorporation and improving quality of NCD films were illustrated when the total amount of N 2 and O 2 was fixed at 1 sccm [41] and by stabilizing a certain orientation or texture such as <100> orientation when an equal amount of N 2 and O 2 addition was employed [29] The main mechanisms of diamond growth from only CH 4 and H 2 precursor gases using MPCVD method can be found in a recent work on the two-dimensional modeling of diamond growth by MPCVD [42]. In that work, two-dimensional modelling of microwave plasma of CH 4 /H 2 gas mixtures at power (1-3 kW) disclosed the radial and axial gradient distribution of absorbed power density in an MPCVD system [42].…”