Effect of Nitrogen on the Growth of (100)-, (110)-, and (111)-Oriented Diamond Films

Jen-Chuan Tung,Po-Liang Liu,Tsung-Che Li,Yen-Jui Teseng

doi:10.3390/app11010126

Jen-Chuan Tung, Po-Liang Liu + Show 2 more

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https://doi.org/10.3390/app11010126

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Abstract

The aim of this research is the study of hydrogen abstraction reactions and methyl adsorption reactions on the surfaces of (100), (110), and (111) oriented nitrogen-doped diamond through first-principles density-functional calculations. The three steps of the growth mechanism for diamond thin films are hydrogen abstraction from the diamond surface, methyl adsorption on the diamond surface, and hydrogen abstraction from the methylated diamond surface. The activation energies for hydrogen abstraction from the surface of nitrogen-undoped and nitrogen-doped diamond (111) films were −0.64 and −2.95 eV, respectively. The results revealed that nitrogen substitution was beneficial for hydrogen abstraction and the subsequent adsorption of methyl molecules on the diamond (111) surface. The adsorption energy for methyl molecules on the diamond surface was generated during the growth of (100)-, (110)-, and (111)-oriented diamond films. Compared with nitrogen-doped diamond (100) films, adsorption energies for methyl molecule adsorption were by 0.14 and 0.69 eV higher for diamond (111) and (110) films, respectively. Moreover, compared with methylated diamond (100), the activation energies for hydrogen abstraction were by 0.36 and 1.25 eV higher from the surfaces of diamond (111) and (110), respectively. Growth mechanism simulations confirmed that nitrogen-doped diamond (100) films were preferred, which was in agreement with the experimental and theoretical observations of diamond film growth.

Highlights

Diamond consists of carbon atoms and has physical properties such as a low coefficient of friction [1], a high mechanical hardness of 100 GPa (75.5–111.5 GPa for diamond films), a high bulk modulus of 1.2 × 1012 N/m2, a high thermal conductivity of 20 W/cm·K (10 W/cm·K for diamond films), a thermal expansion coefficient of 0.8 × 10−6 /K, high electrical resistivity of 1016 Ω·cm, and a high energy bandgap of 5.47 eV [2]
Hot filament (HF) chemical vapor deposition (CVD), microwave plasma (MP) CVD, and MP-enhanced CVD have since been used for the growth of diamond films [6,7,8]
In 1993, Singh and Vellaikal proposed the following process for the nucleation of diamonds: carbon atoms first aggregate into carbon clusters, and the sp2 bonds between carbon atoms are transformed into sp3 bonds at high pressure, which results in the carbon clusters forming a diamond structure [9]

Summary

Introduction

Diamond consists of carbon atoms and has physical properties such as a low coefficient of friction [1], a high mechanical hardness of 100 GPa (75.5–111.5 GPa for diamond films), a high bulk modulus of 1.2 × 1012 N/m2 , a high thermal conductivity of 20 W/cm·K (10 W/cm·K for diamond films), a thermal expansion coefficient of 0.8 × 10−6 /K, high electrical resistivity of 1016 Ω·cm, and a high energy bandgap of 5.47 eV [2]. Diamonds are employed in technical fields to accomplish tasks such as cutting, wear resistance coatings [3], and fabricating semiconductor components [4]. Sussmann et al used chemical vapor deposition (CVD) with methane, oxygen, and hydrogen [5] mixed in a specified ratio. The diffusion of carbon atoms on the

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