24G13
Control of growth mode in diamond (111) homoepitaxy by
microwave plasma CVD
マイクロ波プラズマCVDによるダイヤモンド(111)ホモエピタキシーの成長モードの制御
Makoto Fukui1, Norio Tokuda1,2,3, Toshiharu Makino2,3, Satoshi Yamasaki2,3 and Takao Inokuma1
福井 真1, 徳田規夫1,2,3，牧野俊晴2,3，山崎 聡2,3，猪熊孝夫1
1

Grad. School of Natural Sci. & Technol., Kanazawa Univ., Kakuma-machi Kanazawa, 920-1192, Japan1
金沢大院自然 〒920-1192 金沢市角間町2
ETRI, AIST, 1-1-1 Umezono Tsukuba, 305-8568, Japan2
産総研エネ部門 〒305-8568 つくば市梅園1-1-1
3CREST/ JST, c/o ETRI, AIST, Japan
3CREST/JST, c/o 産総研エネ部門

Crystal growth process of diamond (111) homoepitaxy by microwave plasma-enhanced chemical vapor
deposition was investigated on characterizing areas by ex-situ atomic force microscopy. The evolution ofsurface morphology during the diamond homoepitaxy was visualized utilizing a mesa ofmesa-structure-patterned surface as a marker. Depending on the methane concentration in the gas phase wefound a variety of growth modes; lateral, two-dimensional island and three-dimensional growth. The lateral
growth formed 100 × 100 µm2 step-free surfaces of (111) diamond. This growth technique will be a key torealize high quality diamond devices.

1. Introduction
Diamond device is expected to be one of thenext-generation semiconductor devices, such as
high-powerelectronic,optoelectronic,biotechnological and quantum computing devices,because of superior physical, chemical andelectronic properties. For fabrication of diamonddevice, homoepitaxial diamond films are grown
mostly on (100) and (111) substrates by
microwave plasma-enhanced chemical vapor
deposition (MPCVD). However, its growthmechanism is not clearly understood. To
elucidate the growth mechanism, both vapor
phase reaction and surface reaction need to bestudied. Observation of the growth surface is
crucial for the elucidation of the growthmechanism, since the growth process influences
the morphology of growth surface. To clarify thegrowth mechanism, in-situ observations for Si,
Ge and GaAs have been carried out, but in-situ
observation of diamond growth during MPCVD
process is extremely difficult, because of hightemperature (800 ~ 1100°C), high pressure (25 ~150 Torr) and hydrogen plasma environment.
Therefore, other techniques for surface
observation are important for clarification of
diamond growth mechanism, instead of in-situ
observation. In this study, we use ex-situ atomic
force microscopy (AFM) to investigate thesurface morphology of homoepitaxial diamond(111) films grown by MPCVD, and examine
growth modes in the diamond homoepitaxy.
2. Experimental
Using MPCVD system with 0.05% CH4 dilutedin H2, diamond films were deposited on
single-crystalline diamond (111) substrates whose
surfaces were patterned with mesa structures. The
mesa structures were fabricated by electron beamlithography and inductive-coupled plasma etching.
The total pressure and microwave power weremaintained at 50 Torr and 1200 W, respectively.
The substrate temperature was around 900°C. The
morphology of diamond surfaces on mesas before
and after the MPCVD growth was observed with
ex-situ AFM in air. We judged the growth modes
from the surface morphology of diamond films onmesas.
3. Results
Figure 1 and 2 show AFM images of mesas ofdimension 1 × 1 μm2 before and after the MPCVDgrowth at 0.05% CH4/H2 ratio for 1 h, respectively.
The substrate surface before growth was rough,which was induced by surface mechanical polishing.
On the other hand, the mesa top surface after
growth was atomically flat, which was composed ofsingle bi-atomic layer steps and an atomically flat
equilateral triangular island [1]. The heights of thesteps were approximately 0.21 nm, which[nm]AA’0900 [nm]2.00.5[nm]

corresponds to the theoretical height of single
bi-atomic layer (111) step. Accordingly, this growthmodeisexperimentally
identified
astwo-dimensional island growth.
In this presentation, we will systematically
discuss the relationship between growth modes
including two-dimensional island growth as well aslateral and three-dimensional growth, and CH4
concentrations, and we will also demonstrate thelateral growth of 100 × 100 µm2 step-free surfaces,
which are perfectly flat surfaces without any atomic
steps and islands on (111) diamond [2,3]. We aresure that this growth technique will be a key torealize high quality electronic interfaces anddevices.

B’B0. 21 nm
0. 21 nm

0900 [nm]B

B’

400 [nm]Fig. 2. Three-dimensional and cross-sectional AFM
images of a mesa of dimension 1 × 1 μm2 after theMPCVD growth at 0.05% CH4/H2 ratio for 1 h.

AA’

400 [nm]Fig. 1. Three-dimensional and cross-sectional AFM
images of a mesa of dimension 1 × 1 μm2 before theMPCVD growth.

Acknowledgments
This work was partially supported by theAdaptable and Seamless Technology Transfer
Program through target-driven R&D (No.
AS2211074B) from the Japan Science andTechnology Agency.
References[1] N. Tokuda, H. Umezawa, S.-G. Ri, M. Ogura, K.
Yamabe, H. Okushi, S. Yamasaki, Diamond Relat.
Mater. 17 (2008) 1051.
[2] N. Tokuda, H. Umezawa, H. Kato, M. Ogura, S.
Gonda, K. Yamabe, H. Okushi, S. Yamasaki, Appl.
Phys. Express 2 (2009) 055001.
[3] N. Tokuda, H. Umezawa, K. Yamabe, H. Okushi, S.
Yamasaki, Diamond Relat. Mater. 19 (2010) 288.