1 ADC 2003 Nano Ni dot Effect on the structure of tetrahedral amorphous carbon films Churl Seung Lee, Tae Young Kim, Kwang-Ryeol Lee, Ki Hyun Yoon* Future Technology Research Division, Korea Institute of Science and Technology, P.O.Box 131, Cheongryang, Seoul, , KOREA * Department of Ceramic Engineering, Yonsei University, Seoul, , KOREA

2 –High ratio of sp 3 hybridized carbon bonds –High hardness, smooth surface, thermal stability, chemical inertness…. –Filtered Vacuum Arc ta-C (Tetrahedral Amorphous Carbon) AFM image of ta-C (Rms=3Å)

3 Disadvantage of ta-C films –High Residual Stress –Poor Adhesion on Ferrous Substrate –Poor Reliability of the Coating Solutions to Overcome the Disadvantages –Nano-composite using 3 rd element addition –Nano-scale Multilayer Present Work : New Nano-structured Coating –Nanoscale Graphitic Columns in ta-C Matrix using Nano Ni dot. Introduction

4 Idea of the Present Work Nano Ni dot pretreatment –Deposition and Annealing Ni thin film on Si substrate. –Ni dot size can be controlled by Ni deposition time. Deposition of ta-C films on nano Ni dots

5 Nano Ni Dot 15 sec30 sec60 sec 3.4 nm6.8 nm13.1 nm Ni deposition time Thickness of Ni film

6Synthesis Cleaning & Bufferlayer - Ar 8 sccm, HF -840 V - 5 min V b =0 (25 eV) Deposited on Pure Si wafer Nano Ni dot / Si wafer In situ pretreatment can be possible !

7 ta-C on Nano Ni Dot 15 sec30 sec60 sec 3.4 nm6.8 nm13.1 nm Ni deposition time Thickness of Ni film

8AFM ta-CNi 3.4Ni 6.8Ni 13.1 Surface roughness was mainly due to nano Ni dots. What happened in the microstructure? rms=0.3 nmrms=2.07 nmrms=12.8 nmrms=25.1 nm

9TEM 100nm Ni 3.4 Ni 13.1 ta-C Ni 6.8

10TEM 20nm100nm Successful Nanoscale Manipulation of ta-C film by Nano Ni dots Nanoscale pillar type 2 nd phases around Ni dots in pure ta-C matrix Vertical and local (2-D) modulation of structure The content of 2 nd phase was proportional to Ni dots size What is this 2 nd phase?

11Resistivity Conducting path in insulating ta-C matrix  2 nd phase

12 Mechanical Properties 2 nd phase was very soft region.

13Raman Graphitic component increased with increasing the size of Ni dots.

14 TEM EELS 20nm A B  * peak  sp 2 ratio Nanoscale pillar type 2 nd phases is sp 2 rich region

15 Catalyst Effect of Ni Did Ni dot cause the phase transformation? Comparison with the case of using Cu nano dot In contrast to the case of Ni dots, there are no structural evolution in the case of Cu dots.

16Discussion Filtered Vacuum Arc –Can provide sufficient energy to heat locally amorphous carbon on the Ni surface. –By high energy ion bombardment or high flux of electrons. Ni catalyst effect –Amorphous carbon transformed to graphite already at relatively low temperature (e.g. above 730  K) when amorphous carbon was in contact with Ni. R. Lamber et al, Surf. Sci., 197, 402 (1988). Second phase only around Ni dot –sp 2 rich region –Experimental result can be readily addressed in the view point of local increase of sp 2 in the hard ta-C matrix.

17Conclusions Successful Structure Control of ta-C film by Nano Ni dots –Nanoscale Manipulation of ta-C films were possible. Local selective graphitization by Ni dots. Dispersed pillar type sp 2 rich region embedded in sp 3 rich matrix. Changing of Structure with nano Ni dot size –It was closely related with 2 nd phase by nano Ni dot. 2 nd phase was sp 2 rich region. Chemical effect - Ni induced the graphitization. FVA could provide high energy for thermal activation. –In the view point of application, this technique would have a potential for a variety of application.

18 Idea of the Present Work Nano Ni dot pretreatment –Nano Ni dot. Catalyst of Carbon Nanotube. Ni mediated transformation of amorphous carbon to graphite –FVA can provide the thermal activation energy –Nanoscale Manipulation of ta-C Films by Nano Ni Dot T.Y.Kim et al, Chem. Phys. Lett. 372, 603 (2003)