Ming-Hua Shiao

A formation mechanism for the macroparticles in arc ion-plated TiN films

Abstract Characterization of macroparticles in TiN films prepared by an arc ion-plating method on AISI 304 stainless steel was carried out by energy filtering transmission electron microscopy. The results show that most of the macroparticles have the shape of a bud, which has the equiaxial polycrystalline Ti metal located at the bottom center. The outerlayer consists of TiN 0.26 , α-TiN 0.3 and Ti 2 N, in addition to TiN, identified by selected area diffraction. On the basis of the analysis, a model describing the formation of macroparticles in the arc ion-plated TiN is proposed. Once emitted from the cathode, the liquid Ti droplets react with nitrogen during their migration to the substrate and form a thin layer of titanium nitrides on the surface of the droplets, resulting in a core-shell structure. As a result of the high-melting outshell, flattened torus voids are produced, upon impact on the substrate, beneath each particle which causes shadowing of the ion flux during deposition. Subsequent growth of TiN follows the orientation of the titanium nitride nuclei in the outshell to form a radial type structure, until coalescence with the regular TiN columns grown perpendicular to the substrate surface occurs.

Influence of sputtering parameter on the optical and electrical properties of zinc-doped indium oxide thin films

The zinc doped indium oxide (IZO) films deposited with various sputter parameters such as, film thickness ranging from 200to500nm, O2∕Ar ratio ranging from 0% to 12%, and sputter power ranging from 100to250W was studied in this work. For a 200nm thick IZO film grown at room temperature in pure argon atmosphere, the resistivity was 2.4×10−4Ωcm and the average transmittance in the visible region was 80%. The root mean square roughness of IZO film was around 0.4nm regardless of the film thickness due to the IZO films exhibiting an amorphous structure. With increasing film thickness, the IZO films showed an increase in the resistivity and energy band gap. X-ray photoelectron spectroscopy analysis suggests that the IZO films with reduction of O2∕Ar ratio possess two splitting O1s binding energy levels, suggesting the IZO films were oxygen deficient and resulted in a lower resistivity.

Effects of Ti interlayer on the microstructure of ion-plated TiN coatings on AISI 304 stainless steel

Abstract The microstructure and chemistry of TiN coatings on AISI 304 stainless steel was analyzed by an energy filtering transmission electron microscope (TEM) equipped with an electron energy loss spectroscopy (EELS) detector. Two types of TiN-coated specimens, with and without a Ti interlayer, were prepared by a hollow cathode discharge ion plating coater. For the TiN directly coated on steel, it is found that the grain size, texture, and chemistry of the coating is thickness dependent. The large residual stresses in TiN caused the formation of dislocation networks and cell walls in the steel, and often resulted in early failure of the coating upon subsequent handling. Compared to the TiN–steel system, the introduction of a Ti interlayer between TiN and steel gives rise to the different results. The microstructure of TiN coatings with a Ti interlayer is mainly composed of columnar grains whose size is found to be relatively independent of coating thickness. Near the TiN–Ti interface, it is observed that many of the TiN grains grew out of the underlying Ti crystallites. Consequently, a very good epitaxial relation is established between TiN and Ti. The texture of the TiN coatings with a Ti interlayer, therefore, showed enhanced preferred orientation when approaching the TiN–Ti interface. From the calculation of the unrelaxed thermal stress based on a bilayer model, it is demonstrated that the presence of a Ti interlayer between TiN and steel can dramatically reduced the thermal stress in the TiN coating.

Measurement of the interfacial mechanical properties of a thin ceramic coating on ductile substrates

Abstract The interfacial mechanical properties of two systems, SiOx/Au and SiOx/Cu, were measured by a modified periodic cracking method. The state of stress in the SiOx-coated metal wires with cylindrical symmetry were analyzed using a classic model of continuum elasticity. Experimentally, the measurement was carried out by a uniaxial tensile test. Specimens for the tensile test were prepared by depositing a thin layer of SiOx on the metal wires by a plasma enhanced chemical vapor deposition (PECVD) technique. After tensile loading, it was found that the fracture morphology of the SiOx coating depended upon the bonding strength of the interfaces. For a weak interface such as SiOx/Au with a measured bonding strength of 0.230 MPa, debonding at the interface prevailed and most of the cracks in the SiOx coating were inclined to the tensile axis by 45°. In contrast, cracks in the coating of a strong interface such as SiOx/Cu showed periodicity and were perpendicular to the tensile axis. The bonding strength of the interface was estimated to be, at least, 0.885 MPa, while the ultimate shear strength was measured to be 49.5 MPa.

Effects of processing parameters on the microstructure and hardness of the arc ion-plated TIN on a type 304 stainless steel

Abstract Substrate bias and specimen-to-target distance are two important parameters that can be manipulated during preparation of TiN films using a cathodic arc ion plating system. Experiments were carried out to deposit TiN on a type 304 stainless steel for different cathode biases ranging from 100 to 300 V and specimen-to-target distances from 150 to 175 mm. Characterization of the microstructure of the TiN-coated steel was done both by transmission and scanning electron microscopy. The results show that the thickness of the TiN coatings increases with decreasing specimen-to-target distance. The TiN coatings exhibit a tapered columnar microstructure and the cone shape of the grains is influenced by the substrate bias. The resistance to deformation of the TiN coatings was evaluated by a Vickers microhardness indenter. It is found that the hardness of the coatings, ranging from 2200±40 to 1880±10, decreases with specimen-to-target distance for different substrate biases ranging from 100 to 300 V.

Characterization of AlN Thin Films Prepared by Unbalanced Magnetron Sputtering

Aluminum nitride (AlN) thin films were deposited on silicon wafers and glass substrates by an unbalanced magnetron (UBM) sputtering system equipped with a pulse dc power supply. Microstructure and chemistry of the AlN-coated specimens were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The optical transmission properties of the AlN-coated glass were investigated using an ultraviolet/visible (UV/VIS) spectrophotometer. It was found that the thin films are polycrystalline and have a hexagonal wurtzite structure with (002) preferred orientation, as revealed by XRD and TEM. AFM analysis indicates that the surface of the thin films is smooth, with an average roughness R a = 6.464 nm, which is suitable for application in surface acoustic wave devices. XPS analysis gives the chemical composition of the coatings as well as the bonding states of the elements. In addition, the AlN thin films are transparent in the visible region with an average transmittance of 60%.

Effects of temperature on columnar microstructure and recrystallization of TiO2 film produced by ion-assisted deposition.

Titanium oxide thin films were deposited by electron-beam evaporation with ion-beam-assisted deposition. The effect of the substrate temperature and annealing temperature on the columnar microstructure and recrystallization of titanium oxide was studied. The values of the refractive index varied from 2.26 to 2.4, indicating that the different substrate temperatures affected the film density. X-ray diffraction revealed that all films were amorphous as deposited. At annealing temperatures from 100 degrees C to 300 degrees C, only the anatase phase was formed. As the substrate temperature increased from 150 degrees C to 200 degrees C to 250 degrees C, the recrystallization temperature fell from 300 degrees C through 250 degrees C to 200 degrees C. Changing the substrate temperature resulted in the formation of various types of columnar microstructure, as determined by scanning-electron microscopy. Different columnar structures resulted in different surface morphologies, as measured by atomic-force microscopy.

Microstructural evolution of AlN coatings synthesized by unbalanced magnetron sputtering

Polycrystalline aluminum nitride (AlN) thin films with wurtzite structure were deposited on silicon substrate by an unbalanced magnetron sputtering system equipped with a pulse dc power supply. Microstructure and chemistry of the AlN-coated substrates under different deposition time were characterized by x-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), energy-dispersive spectroscopy (EDS), and electron energy loss spectroscopy (EELS). XRD results show that the thin films exhibit enhanced (002) preferred orientation. It was obtained from FE-SEM and TEM results that the AlN films have a columnar structure, and that the size of the columns increases with the distance from the substrate and the deposition time. Furthermore, AFM analysis indicates that the surface roughness of the coatings increases with the deposition time. In addition, EDS and EELS analyses give the chemical composition of the coating and the...

Interfacial mechanical properties and fracture morphology of a TiN-coated steel wire upon tensile loading

Abstract The state of stress in a TiN-coated stainless steel wire upon tensile loading was analyzed theoretically using a classical model of continuum elasticity, from which the interfacial mechanical properties of the coating system were deduced. Specimens for the tensile test were prepared by deposition of TiN films on stainless steel wires using a hollow cathode discharge ion plating (HCD-IP) coater. Cross-section SEM shows that the TiN produced by the ion plating technique has good coverage on the steel wires and that the thickness ratio between the thickest and the thinnest coatings is 3.57. The failure mechanism of the TiN films upon tensile loading is found to depend on the coating thickness. Opening mode prevails in the thick coatings where periodic cracks perpendicular to the tensile axis developed; on the other hand, shearing mode takes place in the thin coatings where cracks inclined to the tensile axis by 45° occurred. On the basis of the experimental observations and the theoretical calculation, the shear strength of the TiN, the ultimate shear strength and the bonding strength of the TiN/steel interfaces were estimated to be 15.36, 9.87 and 1.06 GPa, respectively.

Characterization and Formation Mechanism of Macroparticles in Arc Ion-Plated CrN Thin Films

The microstructure and chemistry of macroparticles in CrN films prepared by an arc ion-plating method on AISI 304 stainless steel was characterized by an energy filtering transmission electron microscope (TEM) equipped with an electron energy loss spectroscopy (EELS) detector. The surface morphology of the CrN coatings with macroparticles was examined by a high-resolution field emission scanning electron microscope (SEM). SEM observation shows that the macroparticles lie on craters and protrude out of the coating surface. Cross-sectional and plan-view TEM results reveal that the macroparticles are bud shape, which has the Cr metal located at the bottom center and surrounded by a chromium nitride layer. Quantitative EELS analysis of a macroparticle from the core region to the outer shell shows that the nitrogen and oxygen concentrations in the macroparticle increase from 17.7 to 38 atom % and 7.7 to 9.5 atom %, respectively, On the basis of the analysis, a model describing the formation of macroparticles in the arc ion-plated CrN coatings is proposed.