L.S. Wen

X-ray photoelectron spectroscopy and auger electron spectroscopy studies of Al-doped ZnO films

The chemical state of oxygen, aluminum and zinc in Al-doped ZnO (ZAO) films was investigated by X-ray photoelectron spectroscopy (XPS), as well as the transition zone of the film-to-substrate, by auger electron spectroscopy (AES). The results show that zinc remains mostly in the formal valence states of Zn2+. A distinct asymmetry in Al 2p(3/2) photoelectron peaks has been resolved into two components, one is metallic Al and the other is oxidized Al. The depth profile of the two components revealed that metallic Al mainly exists in the thin surface layer. The close inspection of Ols shows that Ols is composed of three components, centered at 530.15 +/- 0.15, 531.25 +/- 0.20 and 532.40 +/- 0.15 eV, respectively. AES reveals an abrupt transition zone between the ZAO and quartz substrate

Surface characterization of transparent conductive oxide Al-doped ZnO films

Abstract High preferred (0xa00xa02) orientation Al-doped ZnO (ZAO) films were prepared by DC magnetron reactive sputtering from a Zn target mixed with Al of 2.0xa0wt%. The dependence of spatial distributions of resistivity on substrate temperature indicates that the spatial distribution of resistivity across substrate placed parallel to the target was improved by increasing substrate temperature. XPS analysis indicates Al-enrichment on the film surface.

Optical and electrical properties of direct-current magnetron sputtered ZnO:Al films

In this study, high-quality ZnO:Al (ZAO) films were prepared by using dc reaction magnetron sputtering technology. The effect of Al doped in ZnO films on electrical and optical properties and its scattering mechanism were discussed in detail. The results showed that Al2O3 could be effectively removed by controlling oxygen flow and Al-doped concentration during deposition of ZnO:Al films. Zn, Al, and oxygen elements were well distributed through the films. For highly degenerated ZnO:Al semiconductor thin films, it was revealed that ionized impurity scattering dominated the Hall mobility of the films in the low-temperature range; while the lattice vibration became a major scattering mechanism in the high-temperature range. The grain-boundary scattering only played a major role in the ZAO films with small grain size (as compared to the electron mean-free path). The photoelectric properties of ZAO films showed that the lower resistivity (similar to 5x10(-4) Omega cm) was obtained, and transmittance in the visible range and reflectance in the IR region were above 80% and 60%, respectively

Oxidation behaviour of NiCrAlY coatings on Ni-based superalloy

NiCrAlY coatings were prepared on cast Ni-based IN100 superalloy using are ion plating, leading to a dense structure. The surface became smoother after vacuum heat treatment. The oxidation kinetic curves of the IN100 alloy and the coating were obtained. The results indicate that NiCrAlY coating gains more weight after cyclic than after isothermal oxidation and no oxide spallation was evident. The oxidation resistance of IN100 superalloy when exposed to either isothermal or cyclic oxidation was markedly improved by coating with NiCrAlY. The oxide scales mainly consisted of alpha-Al2O3 and Cr2O3, at 900degreesC. In the initial oxidation stage at 1000degreesC, three kinds of oxides, NiO, Cr2O3 and alpha-Al2O3, formed simultaneously. With further oxidation, not only is the thickness of the oxide scale increased, but complex reactions also occurred

Formation of Al-doped ZnO films by dc magnetron reactive sputtering

Highly preferred (002) orientation transparent conductive Al-doped ZnO (ZAO) films were successfully prepared by de magnetron reactive sputtering from a Zn target mixed with Al of 2.0 wt.%. The film has a resistivity of 4.80 X 10(-4) n cm and a visible transmittance of as high as 90%. XPS analysis indicates Al-enrichment on the film surface. The asymmetry of Al 2p(3/2) XPS peak is resolved into two components: one centering at 72.14 eV attributed to metallic Al and the other having a binding energy of 74.17 eV due to oxidized Al

The behavior of MCrAlY coatings on Ni3Al-base superalloy

This work is concerned with NiCrAlY and NiCoCrAlY coatings deposited on the superalloy IC-6 (Ni3Al-base superalloy) by arc ion plating (AIP). The results indicated that the presence of Al and Mo in alloy IC-6 impeded Cr atoms moving from coatings to substrates during the deposition process. As a consequence, the distribution of Cr is well proportioned in both NiCrAlY and NiCoCrAlY coatings. Vacuum heat treatment drastically increased diffusivities and the coating became more uniform. The interdiffusion also led to the phase transformation in the coatings. Although gamma-Ni3Al and gamma-Ni were still the major phases in the coating, their lattice constant a(0) decreased. The results of isothermal oxidation showed that the oxidation behavior of coatings obeyed the parabolic rate law. The oxidation resistance was not influenced very much by the presence of Co in the NiCrAlY coating at 900 degreesC static atmosphere. NiCoCrAlY coating had poorer oxidation resistance than NiCrAlY coating when they were exposed at 1000 degreesC

Influence of hot filaments arranging on substrate temperature during HFCVD of diamond films

The substrate temperature distribution during hot filaments chemical vapor deposition (HFCVD) of diamond films was stimulated. Results showed that the substrate temperature varied with the space position. A temperature distribution with the periodic fluctuation that is in accordance with the filaments arranging occurred. An optimum homogeneous temperature substrate position available for the growth of diamond films over a large area existed in the space with 6-8 nun away from the filaments arranging plane. The substrate temperature was influenced by filaments diameter and distance between filaments. The substrate temperature increased with the filaments diameter, but the temperature distribution was not changed. The parallel arranging of the filaments with a 10-min distance between filaments has a lower temperature fluctuation and larger uniform temperature areas for diamond film growth. A more effective way to enlarge the growth areas of the diamond films was to increase the quantity of the arranged filaments with a proper distance between them

Oxidation behavior of thermal barrier coatings obtained by detonation spraying

Thermal barrier coatings (TBCs) have been successfully obtained by detonation spraying, through optimizing the spray parameters (especially the ratio of C2H2 to O-2). The oxidation behaviors of detonation sprayed TBCs at 1000 and 1100 degreesC were studied. The results indicated that the detonation sprayed TBCs were uniforin and dense, with a few microcracks in the ceramic coats and a rough surface of bond coats. At the high temperature, the dense detonation sprayed ceramic coats with low porosity could obviously decrease the diffusive channels for oxygen and reduce the oxygen pressure (PO2) at the ceramic/bond coat interface. Under the lower oxygen pressure at the interface, it was advantageous to the formation of a continuous protective Al2O3 layer and the growth of a thermally grown oxide layer (TGO) obeyed the fourth power law

Interdiffusion Behavior of Ni–Cr–Al–Y Coatings Deposited by Arc-Ion Plating

Ni–Cr–Al–Y coatings were deposited on the Ni3Al–base superalloys IC-6 and K17 by arc-ion plating. The results indicated that a small amount of substrate atoms, such as Co, Ti, Mo, etc., existed in the Ni–Cr–Al–Y coatings near the substrates, probably due to “sputter” and “antisputter.” For the alloy K17, the impeding effect of Al was not obvious, because the temperatures of the substrate and the coating were high (420–480°C) during the deposition process and interdiffusion was accelerated. However, for alloy IC-6 which contains Al, as well as a high concentration of Mo, the diffusion of Cr was impeded. Vacuum heat treatment at 1050°C drastically increased diffusivities and the presence of Al and Mo was not enough to prevent some Cr diffusion. Thus, the coating became more uniform and close to the desired composition.

Properties of ZnO:Al films on polyester produced by dc magnetron reactive sputtering

High preferred (002) orientation Al-doped ZnO (ZAO) films have been prepared by de magnetron reactive sputtering of an alloy target (98.5 wt.% Zn-1.5 wt.% Al) onto polyester substrates. The structural, mechanical, electrical and optical properties were investigated. The ZAO film has a sheet resistance of as low as 47.5 Omega/square and an average visible transmittance of about 70%. An average IR reflectance of about 70% in the region of 2.5-25 mum also has been obtained