Jung-Joong Lee

Structural analysis of AlN and (Ti1−XAlX)N coatings made by plasma enhanced chemical vapor deposition

(Ti1−XAlX)N coatings were deposited by plasma enhanced chemical vapor deposition (PECVD) method using a gas mixture of TiCl4, AlCl3, NH3, H2 and Ar. X‐ray diffraction and transmission electron microscopy were used to investigate the structure of the deposited (Ti1−XAlX)N coatings. They showed single phase NaCl‐structure up to X=0.8, while a mixed phase of NaCl type (Ti0.2Al0.8)N and AlN with wurtzite‐structure was observed for 0.8<X<1.0. The lattice parameter changed linearly with the function X (d=4.241−0.197 X A) in the single phase region. Metastable AlN particles with an NaCl structure and a lattice parameter of 4.03 A were found on AlN coatings produced by PECVD using AlCl3, NH3 and H2. It was assumed that the formation of (Ti1−XAlX)N solid solution in a wide concentration range occurred due to the metastable AlN. When (Ti1−XAlX)N coatings were heat‐treated at 1000 °C, AlN with a stable wurtzite structure precipitated. However, the broadened x‐ray diffraction peak and the diffuse transmission electro...

(Ti1−xAlx)N coatings by plasma‐enhanced chemical vapor deposition

(Ti1−xAlx)N was deposited on high‐speed steel using a radio‐frequency (rf) plasma‐enhanced chemical vapor deposition (PECVD) process from the gas mixture of TiCl4, AlCl3, NH3, H2, and Ar. The composition of the coated layer could be controlled from TiN to (Ti0.17Al0.83)N by the ratio of source gases, TiCl4 and AlCl3. At the same ratio of AlCl3 and TiCl4, the Al content in the coated layer was changed by the rf power employed. According to x‐ray diffraction and transmission electron microscopy, the PECVD‐(Ti1−xAlx)N coating with x≤0.77 was found to have a NaCl‐type structure with Ti atoms substituted by Al atoms and a strong crystallographic texture of (200), but (Ti0.17Al0.83)N had a mixed phase of TiN+AlN. It was also found that the hardness, the adhesion, and the surface morphology of the coated layer were affected by the Al content as well as by the rf power employed.

Mechanical properties of titanium nitride coatings deposited by inductively coupled plasma assisted direct current magnetron sputtering

TiN coatings were deposited on M2 high speed steels by an inductively coupled plasma (ICP) assisted sputtering technique. The structure and mechanical properties such as hardness, Young’s modulus, and adhesion strength of the coatings were investigated. For ICP sputtering, rf power was applied using a rf coil installed in the deposition chamber. Prior to the deposition, the substrate was pretreated by ICP in the same deposition chamber in order to improve the adhesion strength of the coating. The ICP power was varied from 0 to 600 W, and the hardness of the coatings was found to increase with increasing ICP power. When the ICP power was larger than 300 W, the hardness of TiN was above 6000 HK0.01, which was one of the highest hardness values of TiN reported in the literature. The adhesion strength of the coating was also high enough for industrial applications. The results from structural investigations indicated that the high hardness is a property of the dense structure as well as the high compressive r...

High temperature oxidation of (Ti1-XAlX)N coatings made by plasma enhanced chemical vapor deposition

(Ti1-XAlX)N coatings were deposited by the plasma enhanced chemical vapor deposition method using a gas mixture of TiCl4, AlCl3, NH3, H2 and Ar, and the oxidation behavior at high temperatures as well as the oxidized structure of the coatings were examined. The oxidation rate of the coatings at temperatures below 1000 °C was found to fit well to a parabolic time dependence. It has also been found that up to 900 °C (Ti1-XAlX)N coatings at X⩾0.25 showed considerably improved oxidation resistance compared to TiN, due to the formation of a dense α-Al2O3 layer at the surface of the coatings. At X<0.25, however, this dense protective layer could not form, and the coatings were fully oxidized after a short period of time. When the temperature reached 900 °C, Fe in the substrate diffused out through the coating by pipe diffusion as well as through the cracks that were produced by thermal stresses, and oxidized rapidly at the surface of the coating.

The structure and mechanical properties of multilayer TiN/(Ti0.5Al0.5)N coatings deposited by plasma enhanced chemical vapor deposition

Abstract The structure and the properties of multilayer TiN/(Ti 0.5 Al 0.5 )N coatings with a layer thickness of 50 nm and a film thickness of 3 μm, which were deposited on high-speed steel and Si wafer substrates using plasma enhanced chemical vapor deposition, were investigated. Continuous columnar growth was observed in the multilayer coatings without any interruption at the layer boundaries. The identical crystal structure and similar lattice parameter between TiN and (Ti 0.5 Al 0.5 )N layers made the continuous columnar growth possible. The multilayer coating exhibited a higher hardness, adhesion strength and wear resistance compared to either of the monolayer TiN and (Ti 0.5 Al 0.5 )N coatings. It is believed that the stress evolution at the layer boundaries increased the hardness of the coating. However, the stress evolution was interrupted at the layer boundaries, which positively affected the adhesion property of the coating. The higher hardness and adhesion caused a higher wear resistance of the multilayer coating compared to either of the monolayer TiN and (Ti 0.5 Al 0.5 )N coatings.

Mechanical properties of TiN/TiB2 multilayers deposited by plasma enhanced chemical vapor deposition

Abstract Nanometer scale TiN/TiB 2 multilayer coatings with a thickness of approximately 2 μm could be deposited on steel substrates using PECVD. The coatings were prepared by alternate depositions of TiN and TiB 2 using a gas mixture of TiCl 4 , H 2 , Ar, N 2 and BCl 3 . The TiN grain size increased with increasing TiN layer thickness, while changes in the TiB 2 layer thickness had no significant influence on the microstructure of the TiB 2 layers. The plastic hardness of the coatings increased steadily with decreasing TiN layer thickness and with increasing TiB 2 layer thickness. No significant change in hardness was observed with changes in the layer period. The hardness values of the multilayer coatings had a linear relationship with the TiB 2 volume fraction. Therefore, the maximum hardness value of the multilayer coatings did not exceed that of the monolayer TiB 2 coating. The wear resistance, however, increased by incorporating TiN layers. It was found that multilayer coatings with periods

COMPOSITIONALLY GRADIENT (TI1-XALX)N COATINGS MADE BY PLASMA ENHANCED CHEMICAL VAPOR DEPOSITION

Compositionally gradient (Ti1−xAlx)N coatings were deposited by the plasma enhanced chemical vapor deposition technique using a gas mixture of TiCl4, AlCl3, NH3, H2, and Ar. The Al and the Ti concentrations in the coated layer changed linearly with the logarithms of the flow rate ratio of AlCl3 to TiCl4, log(QAlCl3/QTiCl4). Since the vapor pressures of AlCl3 and TiCl4 change exponentially with the temperature within the range where the vaporizers of the source materials were heated for the deposition, the concentrations of Al and Ti in the coatings could be controlled simply by changing the temperatures of the vaporizers. X‐ray diffraction (XRD) investigations showed that the compositionally gradient (Ti1−xAlx)N coating has the NaCl structure with a preferred orientation of (200), like TiN, up to the Al concentration of about X=0.8. The broadened XRD peak with its shifted position indicates that the lattice parameter of (Ti1−xAlx)N changed gradually with the concentration change in the coated layer. A sup...

Low temperature TiN deposition by ICP-assisted chemical vapor deposition

Abstract TiN films were deposited by inductively coupled plasma (ICP)-assisted CVD using a gas mixture of TiCl 4 , H 2 , Ar and N 2 with a substrate temperature of 400 °C and room temperature. For ICP generation, r.f. power was applied using a dielectric-encapsulated coil antenna installed inside the deposition chamber. The ICP power was varied from 100 to 400 W. The deposition rate was as high as >1 μm/h in most deposition conditions. As the r.f. power was increased, the deposition rate decreased irrespective of the deposition temperature. It is believed that the decrease in the deposition rate at higher ICP powers is due to resputtering of the coatings as a result of ion bombardment as well as film densification. The hardness increased with increasing r.f. power, indicating the formation of a denser film at higher power. The decrease in the resistivity at high powers is related to the low Cl content in the film. The TiN film deposited by ICP-assisted CVD showed also a good step coverage on the trenches with a high aspect ratio.

Effect of atomic hydrogen on the growth of Ge/Si(100)

Dynamically supplied atomic hydrogen was used for a surfactant growth of Ge on a Si(100) surface. The transition from three-dimensional to two-dimensional growth of Ge was observed as the hydrogen flux was increased to ∼1 ML/s in scanning tunneling microscope images. Layer-by-layer growth was successfully achieved up to 5 ML of Ge in the presence of atomic hydrogen. Observed missing dimer rows, irregular trench structures, and new “pin holes” are believed to be the product of strain relieving mechanism. The layer-by-layer growth can be understood both by energetics and kinetic pathway arguments.

Application of inductively coupled plasma to super-hard and decorative coatings

An inductively coupled plasma (ICP) assisted technique is expected to be the next generation deposition technique due to its many beneficial properties. In this paper, an internal type r.f. ICP process is presented. The core of this technology is the efficient production and control of self-depositing ions and reactive gas ions by an induced electric field. The properties of the immersed ICP can be tuned between the capacitively coupled and inductively coupled state by changing the antenna materials, the tuning network design, the driving frequency and the external magnetic field. Examples of applications of ICP to super-hard and decorative TiN and CrN coatings, which were produced by ICP magnetron sputtering and ICP evaporation, respectively, are presented.