Deformation and removal characteristics in nanoscratching of 6H-SiC with Berkovich indenter

doi:10.1016/j.mssp.2014.11.034

Materials Science in Semiconductor Processing

Volume 31, March 2015, Pages 160-165

https://doi.org/10.1016/j.mssp.2014.11.034 Get rights and content

Abstract

In order to analyze the deformation characteristics and removal mechanism of the single crystal silicon carbide at the nanoscale, the nanoscratching test was conducted on 6H single bond SiC (0001) by using a Berkovich diamond indenter. The deformation and removal characteristics of 6H-SiC during a nanoscratching process by using a sharp indenter are significantly different from those through a single-point diamond turning (SPDT) method. The characteristics in different regimes of the scratching process like plastic flow and the form of fracture behavior were analyzed. The ductile/brittle transition (DBT) of this material was discussed in detail theoretically and experimentally. X-ray diffraction and a laser micro-Raman spectrometer were used for phase analysis after the scratching process. The results indicate that phase transformation has not occurred during the nanoscratching process of this material.

Introduction

Silicon carbide (SiC) is an ultra-hard structural ceramic material and an important wide-band-gap semi-conductor as well. It shows excellent resistance to thermal shock, oxidation, and corrosion under the conditions of high temperature and pressure [1], for which SiC boasts of its widespread applicable prospect in such fields as structural composites and electronic materials [2]. As a typical brittle material, however, in classical or Griffith sense with high stiffness (E/r) and extreme micro-hardness, it is really difficult to obtain high surface quality by mechanical methods, even by the diamond cutting tool [3], [4], [5].

In recent years, some researchers show great interest in the ductile machining of single crystal silicon carbide. Initially, ductile regime machining of single-crystal silicon carbide (6H) was achieved by using single-point diamond turning (SPDT) at penetration depth less than 500 nm, and the nose radius of cutting tools is about 2 mm [6]. This material is believed to have high pressure phase (HPP) like other types of semi-conductor and ceramic in ductile machining [7], [8], [9]. Jacob et al. performed a single pass cut experiment on 6H-SiC by using a round nose tool with nose radius about 1 mm. The critical depth of cut h_c for 6H-SiC measured by a Raman microscope is about 70 nm [10]. Another report shows that a surface finish of R_a=9.2 nm was obtained with an SPDT method [11]. They found that the diamond fly cutting tool with negative rake angle caused a significant increase in the thrust force [11], which can facilitate the realization of ductile-regime machining of hard and brittle materials [12].

The nanoscratch technique was used as a method to analyze the mechanical properties of materials [13]. This approach provides with an insight into the deformation and removal mechanism of grinding. The removal mechanism of ultra-precision grinding is different from that of fly-cutting method. Nose radius and rake angle of the grains are so much smaller than those of fly-cutting tools that will generate greater hydrostatic pressure and more micro-cracks. Hardly any report about this can be found until today. Obviously, it requires more work to explain the mechanism of deformation for single crystal silicon carbide during the process of grinding. This paper aims at performing an intensive analysis of ductile and brittle characteristics of 6H-SiC during a nanoscratching process with a Berkovich diamond indenter and providing with core information for further study of damage-free grinding of this material.

Section snippets

Experimental details

The experiment was conducted on the (0001) surface of N-type 6H-SiC substrate (Hefei Kejing Materials Technology Co., Ltd) precisely polished and the roughness parameter R_a is less than 1 nm. The sample size is 10×5×0.33 mm³. As shown in Fig. 1, the nanoscratching experiment was carried out with the Nano Indenter XP (MTS Systems Corp.) by using a diamond Berkovich indenter (triangular-based pyramid) under a progressive load at fixed loading rate. Nose radius of the indenter is about 940 nm, as

Characteristics of the 6H-SiC (0001) after nanoscratching test

The optical image of the scratch groove on the surface of 6H-SiC is shown in Fig. 3. The whole process was divided into five regimes: the elastic regime, the plastic regime, the subsurface cracking regime, the surface and subsurface cracking regimes and the mico-abrasive regime [14], [15]. In the last regime, some debris which is linked to a non-reproducible process appears on the surface.

As shown in Fig. 4, the penetration depth h increases smoothly in the previous section. Since the applied

Conclusion

The nanoscratching test with Berkovich indenter was conducted on 6H-SiC (0001) over the progressive load (0.1–100 mN) to analyze the deformation features on the nanoscale and removal mechanism for this material. Based on the test results and theoretical analysis, the following conclusions are reached:

1.
Detailed analysis for the typical characteristics of regimes from the micro-ductile regime to the micro-abrasive regime during nanoscratching was performed. The critical depth of cut measured in

Acknowledgment

This work was supported by the National Key Basic Research and Development Program of China (973 program, Grant no. 2011CB 013202) and the National Natural Science Foundation of China (Grant no. 51175126). We would like to express our gratitude to Professor Liangchi Zhang who has offered us valuable suggestions during our studies.

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Deformation and removal characteristics in nanoscratching of 6H-SiC with Berkovich indenter

Abstract

Introduction

Section snippets

Experimental details

Characteristics of the 6H-SiC (0001) after nanoscratching test

Conclusion

Acknowledgment

Ultramicroscopy

Int. J. Mach. Tool. Manuf.

CIRP Ann.-Manuf. Technol.

Int. J. Mach. Tool. Manuf.

J. Manuf. Process.

Int. J. Mach. Tool. Manuf.

Int. J. Mach. Tool. Manuf.

Tribol. Int.

J. Non-Cryst. Solids

Acta Mater.

CIRP Ann. Manuf. Technol.

Ann. CIRP