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Material Science and Technology of Japan, 56（2019）22～27

Feb. 2019

Regular Paper
Effect of Boronizing Pretreatment on B-doped Diamond Growth on Ti
Substrates Using MWPCVD
Tomoya SAKUMA 1,2,*, Asuka SUZUKI2, Takuya MARUKO2, Yuta IZU3,and Yukihiro SAKAMOTO3
1

Department of Technical Development, Ogura Jewel Industry Co., Ltd., 5-7-12 Omori-kita, Ota-ku, Tokyo
143-0016, Japan
2

Chiba Institute of Technology graduate school, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan

3Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan

Received Sep. 27, 2018; accepted Nov. 30, 2018
Abstract
Since the bonding dissociation energy follows the order of TiB > TiB2 > TiC, introducing Ti-B into the intermediate
layer of B-doped diamond (BDD) on a Ti substrate can be expected to be improved the adhesion strength between theTi substrate and the BDD film. The boronizing of each Ti substrate with different reaction durations and thedeposition of BDD on each Ti substrate with different reaction durations were conducted using amode-conversion-type microwave plasma chemical vapor deposition apparatus, which is able to consistently processboronizing pretreatment and deposition of BDD, using a solution of trimethyl borate as the boron source. From theresults of chemical bonding analysis by X-ray photoelectron spectroscopy of the surface of each Ti substrate after theboronizing, it was observed that the amount of Ti-B increased with the increase in the boronizing time. Further, theadhesion strength of BDD/Ti increased with the increase in the boronizing duration up to 20 min. However, theadhesion strength after 30 min of boronizing became lower than that after 20 min. It is considered that the adhesion
strength was decreased as a result of progressing hydrogen embrittlement.
Keywords: Boron doped diamond, Ti, Boronizing, Adhesion, CVD

1.

Introduction

current is extremely low, and it is insoluble in any solution [5].

Ti and Ti alloys are employed in various fields such as

The Ti/BDD electrodes are promising for application inbioengineering, aerospace engineering, and chemical engineering,

wastewater treatment, because they exhibit the advantages of

because they have excellent characteristics such as a highboth materials [6]. However, the Ti/BDD is inferior tomechanical strength, high corrosion resistance, and low density

BDD-coated niobium, tantalum, tungsten, and silicon materials[1,2]. However, they also have disadvantages such as low

in terms of service life. Furthermore, the results of acceleration

resistance to wear and fretting fatigue [3,4]. Diamond coating islife test (ALT) conducted under severe conditions, i.e., 10

one of the solutions for these problems because of diamond’s

J/Acm-2 current density indicated that the delaminating of thecharacteristics such as extreme hardness, low friction coefficient,

BDD was one of the causes of electrode breakdown [7,8]. The

chemical inertness, and high thermal conductivity [1]. Althoughhigh thermal stress caused by coefficient thermal expansion

16

diamond is generally an insulator of about 10 Ω × cm, a p-type

mismatch between BDD and Ti at the substrate temperature

semiconductor can be formed by doping of B, and the electricalduring BDD synthesis has been reported as one of the adversely

conductivity of B-doped diamond (BDD) is controlled byaffecting these problems [9], and electrochemical corrosion ofcontrolling the B concentration. BDD is an ideal electrodethe TiC intermediate layer during the electrolysis [10]. Althoughmaterial because the potential window is wide, the backgroundnanocrystalline diamond synthesis at a low substrate temperature*Corresponding author: sakuma@ogura-indus.co.jp(22)