Vol.53 No.1

Material Science and Technology of Japan, 53㸦2016㸧33㹼3633

Regular Paper
Pulse Frequency Effects on Carbon Nitride Synthesized Using Pulsed
Microwave Plasma CVD
Ippei TANAKA1,* and Yukihiro SAKAMOTO2
1Graduate School, Chiba Institute of Technology 2-17-1 Tsudanuma,Narashino, Chiba 275-0016, JAPAN

2Chiba Institute of Technology 2-17-1 Tsudanuma,Narashino, Chiba 275-0016, JAPANReceived Nov. 6, 2015; Accepted Dec. 18, 2015
Abstract
Carbon nitride has fascinating properties that include high hardness and high current density of field emissions. In addition, ifc-C3N4 or ȕ-C3N4 structure can be synthesized, then it is possible to obtain high hardness exceeding that of diamond. Pulsed
plasma CVD can be used with low substrate temperature and can improve the film quality and growth rate. For this study, aninvestigation was conducted of pulse frequency effects on crystalline carbon nitride synthesized using pulsed microwave plasma
CVD. The pulse frequency was varied from 30 to 3000 Hz, maintaining a constant duty cycle of 20%.
Results of SEM observation show that crystalline deposits resembling hexagonal rods were obtained from 300 Hz of
microwave frequency. Deposits resembling spheres were observed for CW, 30 Hz, and 3000 Hz. From Raman spectra, only thesilicon peak was observed at 300 Hz of microwave frequency. However, a DLC peak was observed at CW, 30 Hz, and 3000 Hz.
From XPS measurement, SiC, C–C, C–N, C=N, and Si3N4 bonds were observed in all samples. Results show that the effect ofpulse frequency on crystalline carbon nitride synthesized using pulsed microwave plasma CVD, crystalline carbon nitride wasobtained using a 300 Hz pulse frequency.
Keywords: pulse plasma, carbon nitride, plasma CVD

1.

Introduction

carbon nitride. In addition, results indicate that the growth rate isCarbon nitride has fascinating properties that include highlow and that the substrate temperature is high, e.g., 1473 K.

hardness and high current density of field emissions.

Pulsed plasma CVD can be used with a low substrate

Furthermore, if c-C3N4 or ȕ-C3N4 structure can be synthesized,temperature, high film quality, and a high growth rate. Inthen it is possible to obtain high hardness exceeding that ofaddition, pulsed plasma can change the plasma state and control

diamond [1,2].

radicals in plasma. A wide range of pulse frequencies can be used

Therefore, many studies of carbon nitride synthesis fromfor the pulsed plasma. For example, diamond synthesis can bevapor phase have been attempted using various chemical vapor

conducted at 50–1000 Hz [7,8,9]. Pulse plasma is regarded asdeposition (CVD) and physical vapor deposition (PVD) methods.

useful for carbon nitride synthesis.

Films prepared using PVD are generally amorphous. A small

However, the effects of pulse frequency on carbon nitride

amount of nitrogen was included in the film [3]. Some reports

synthesized using pulse plasma remain unclear. Investigations

describe that crystalline deposits were obtained using plasma

were conducted of the effect of pulse frequency on crystalline

CVD [4].

carbon nitride synthesized using pulsed microwave plasma CVD.

The authors tried to obtain crystalline carbon nitride.

2.

Crystalline deposits were obtained from a mixture of CH4-N2 andExperimental methodC2H4-H2-N2 reaction gas systems using microwave plasma CVD

Fig. 1 presents a schematic diagram of microwave plasma[5,6]. Based on results obtained using the C2H4-H2-N2 reaction

CVD apparatus. Carbon nitride was synthesized using angas, control for optimal plasma is necessary to obtain crystalline

improved microwave plasma CVD apparatus equipped with a*Corresponding author: (s1379504zn@s.chibakoudai.jp)(33)