Low temperature deposition of α-Al2O3 thin films by sputtering using a Cr2O3 template
06 Nov 2002-Journal of Vacuum Science and Technology (American Vacuum Society)-Vol. 20, Iss: 6, pp 2134-2136
TL;DR: In this article, a description about low temperature deposition of a-Al2O3 thin films by sputtering was presented and a template was used as a template for nanoindentation.
Abstract: A description about low temperature deposition of a-Al2O3 thin films by sputtering was presented. Cr2O3 thin layer was used as a template. Nanoindentation was used to study the mechanical propertie ...
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TL;DR: P3e (TM) is a new approach in PVD technology for the deposition of metal oxides as mentioned in this paper, which is dedicated to the formation of alumina-based and other metallic oxide layers and comprises high current pulse technique for arc sources.
Abstract: Pulse enhanced electron emission (P3e (TM)) is a new approach in PVD technology for the deposition of metal oxides. The process is dedicated to the formation of alumina-based and other metallic oxide layers and comprises high current pulse technique for the arc sources. The method allows a deposition of hard alumina-based coatings at substrate temperatures below 600 degrees C. Different oxide layers and layer combinations were prepared with this new technique illustrating the enormous potential for the design of wear resistant coatings. The layers were characterized with respect to hardness, stress, composition, crystal structure, and thermal stability. Solid solutions of (Al1-xCrx)(2)O-3 could be synthesized for a composition range of 0.3 <= 5x
115 citations
TL;DR: In this paper, radio frequency sputtering has been used to deposit α-alumina (α-Al2O3) thin films at substrate temperatures of 280-560°C.
Abstract: Radio frequency sputtering has been used to deposit α-alumina (α-Al2O3) thin films at substrate temperatures of 280–560 °C. The films are shown to be single phased and hard. Nanoindentation gives values of 306±31 and 27±3 GPa for elastic modulus and hardness, respectively, for a substrate temperature of 280 °C. Growth of the α phase was achieved by in situ predeposition of a chromia template layer. Chromia crystallizes in the same hexagonal structure as α-alumina, with a lattice mismatch of 4.1% in the a- and 4.6% in the c-parameter, and is shown to nucleate readily on the amorphous substrates (silicon with a natural oxide layer). This results in local epitaxy of α-alumina on the chromia layer, as is shown by transmission electron microscopy. The alumina grains are columnar with grain widths increasing from 22±7 to 41±9 nm, as the temperature increases from 280 to 560 °C. This is consistent with a surface diffusion dominated growth mode and suggests that α-alumina deposition at low temperatures is possibl...
106 citations
TL;DR: In this paper, a commercial production scale PVD system using Si wafers and CrN-coated cemented carbides as substrates, an oxidization pre-treatment was done, and then deposition of Al 2 O 3 films was carried out by varying the process temperature and the substrate bias voltage.
Abstract: Crystalline α-Al 2 O 3 thin films have been deposited using reactive magnetron sputtering at the deposition rate of 0.5–0.7 μm/h above 700 °C in a commercial production scale PVD system. In the experiments, using Si wafers and CrN-coated cemented carbides as substrates, an oxidization pre-treatment was done, and then deposition of Al 2 O 3 films was carried out by varying the process temperature and the substrate bias voltage. An investigation of the correlation between characteristics of these films and deposition conditions was done. XRD study revealed that the under-layer of the Al 2 O 3 films and the substrate temperature for deposition remarkably influenced the film structure. Although only γ-Al 2 O 3 was observed in the films on the Si wafer, Al 2 O 3 film mostly consisting of α-phase was obtained on the CrN under-layer at 700 °C, and pure α-Al 2 O 3 film was deposited at 750 °C without applying bias voltage. TEM observation demonstrated that the α-Cr 2 O 3 interlayer formed by the oxidization pre-treatment of the CrN film played an important role in forming α-Al 2 O 3 . The hardness of the α-Al 2 O 3 film measured by nanoindentation was 23 GPa, and was enhanced to 27 GPa by applying bias.
104 citations
TL;DR: In this paper, the Hartree-Fock analysis of the surface energy of α-alumina and α-chromia has been used as a template for α-Al2O3 growth.
Abstract: There is considerable interest in the low-temperature growth of the stable α-phase of alumina, α-Al2O3, due to its superior chemical and mechanical properties compared to the other forms of alumina. Conventional methods for achieving this phase (such as chemical vapour deposition) utilise high temperatures which limits the range of substrate materials that can be beneficially coated. Recently, it has been reported that α-Al2O3 can be grown on α-Cr2O3 templates at a much lower substrate temperature (around 400 °C) by the RF magnetron sputtering deposition technique. Previous studies showed that both α-Al2O3 and α-Cr2O3 (0001) free surfaces relax considerably in comparison with the corresponding bulk structures. From the experimental point of view, a knowledge of the surface structure and stability of both materials will be of great help in determining the facet of α-Cr2O3 which best facilitates the growth of α-Al2O3. Here we present the results of first-principles Hartree–Fock calculations on the surface energy of the low-index planes of both α-alumina and α-chromia. The suitability of possible α-Cr2O3 facets as templates for the growth of α-Al2O3 is discusssed.
102 citations
TL;DR: In this paper, the bipolar pulsed dual magnetron sputtering (BP-DMS) technique has been used for the deposition of insulating layers such as Al 2 O 3 as well as of conductive compounds such as Ti x Al 1− x N.
Abstract: With the introduction of the bipolar pulsed dual magnetron sputtering (BP-DMS) technique, a wide range of opportunities has opened up for the deposition of insulating layers such as Al 2 O 3 as well as of conductive compound layers such as Ti x Al 1− x N. In BP-DMS, two magnetrons in a pair alternately act as a cathode and an anode; during the cathode phase, the target is sputter-cleaned, hence ensuring a metallic surface during the anode phase and a stable long-term operation. At high-enough frequencies (25–50 kHz), possible electron charging of insulating layers will be suppressed and the otherwise troublesome phenomenon of arcing will be limited. The BP-DMS method has made it possible to deposit hard (>2000 HV ) nanocrystalline γ-Al 2 O 3 textured in the [440] direction at substrate temperatures as low as 700 °C, which is a much lower temperature than the conventional chemical vapor deposition (CVD) temperatures (1000–1050 °C) for the deposition of the Al 2 O 3 polymorphs α and κ. In this paper, a study of the process, in terms of recording the process characteristic data and evaluating the influence of magnetic field, has been done. For a set of parameters, cemented carbide cutting inserts have been coated and tested. Inserts with a double layer of γ-Al 2 O 3 and TiAlN or TiN have been evaluated in cutting operations such as turning, threading, and end-milling, often with machining conditions (cutting data) more suitable for physical vapor deposition (PVD)- than CVD-coated tools. Some results are presented in this paper. It has been shown that the addition of a 2-μm-thick γ-Al 2 O 3 layer decreases the wear rate. The γ-Al 2 O 3 /TiAlN (TiN)-coated inserts exhibit tool lives longer than the single-coated inserts especially at higher cutting speeds.
93 citations
References
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TL;DR: In this article, the development of hard coatings from a titanium nitride film through superlattice coatings to nanocomposite coatings is reviewed, and significant attention is devoted to hard and superhard single layer nano-coating.
Abstract: This article reviews the development of hard coatings from a titanium nitride film through superlattice coatings to nanocomposite coatings. Significant attention is devoted to hard and superhard single layer nanocomposite coatings. A strong correlation between the hardness and structure of nanocomposite coatings is discussed in detail. Trends in development of hard nanocomposite coatings are also outlined.
955 citations
TL;DR: In this article, the structure and morphology of the layers were made via XRD and SEM techniques, respectively, and the hardness was determined by nanoindentation, and residual stresses were derived from the bending of the coated substrates.
Abstract: Alumina coatings were reactively deposited on steel substrates by pulsed magnetron sputtering at substrate temperatures (Ts) of 330–760 °C. Investigations into the structure and morphology of the layers were made via XRD and SEM techniques, respectively. As to the layer properties, the hardness was determined by nanoindentation, and the residual stresses were derived from the bending of the coated substrates. At substrate temperatures of less than 330 °C the Al2O3 layers are amorphous to X-rays, whereas γ-Al2O3 is detected at a substrate temperature Ts ≈ 480 °C. A further increase in substrate temperature to 560 °C results in the formation of a pronounced texture of γ-Al2O3. A phase mixture of textured γ- and α-Al2O3 is deposited at Ts ≈ 690 °C. At Ts ≈ 760 °C the layer consists completely of α-Al2O3 with crystallite sizes of about 1 μm. The occurrence of the crystalline γ phase at 480 °C is linked with a pronounced increase in hardness from 10 to 19 GPa. The layer hardness of pure α-Al2O3 amounts to 22 GPa and corresponds to the hardness of the bulk material.
131 citations
TL;DR: Chrome oxide coatings have been developed for protection of the tape bearing surface of digital compact cassettes (DCC) heads as mentioned in this paper, which are commonly used in magnetic heads and media for protection against corrosion.
95 citations
TL;DR: In this article, the authors describe the hydrogen uptake during the synthesis of alumina thin films from H2O present in the high vacuum gas background, and suggest that an aluminum oxide hydroxide compound is formed, both on the cathode surface as well as in the film.
Abstract: We describe the hydrogen uptake during the synthesis of alumina films from H2O present in the high vacuum gas background. The hydrogen concentration in the films was determined by the 1H(15N,αγ)12C nuclear resonance reaction. Furthermore, we show the presence of hydrogen ions in the plasma stream by time-of-flight mass spectrometry. The hydrogen content increased in both the film and the plasma stream, as the oxygen partial pressure was increased. On the basis of these measurements and thermodynamic considerations, we suggest that an aluminum oxide hydroxide compound is formed, both on the cathode surface as well as in the film. The large scatter in the data reported in the literature for refractive index and chemical stability of alumina thin films can be explained on the basis of the suggested aluminum oxide hydroxide formation.
72 citations
TL;DR: In this article, the authors investigated correlations between process parameters, structure and properties of these layers on steel at substrate temperatures (Ts) of 290-770°C and the sputtering power was varied in the range of 11-17 kW, and the substrate bias was 50 V.
Abstract: It has been shown already that pulsed reactive magnetron sputtering (PMS) allows to deposit crystalline, hard and transparent Al2O3 layers. In this paper, correlations between process parameters, structure and properties of these layers are investigated. The deposition of the layers took place on steel at substrate temperatures (Ts) of 290–770°C. The sputtering power was varied in the range of 11–17 kW, and the substrate bias was 50 V. With increasing substrate temperature and sputtering power, a phase transition takes place from amorphous Al2O3 via λ-Al2O3 into α-Al2O3. At the highest sputtering power, textured γ-Al2O3 occurs already at Ts≈350°C. The formation of α-Al2O3 starts at 670°C, and practically pure α-Al2O3 is present at the highest substrate temperature. The substrate bias has a substantial influence on the ratio of the phase fractions of γ-Al2O3 and α-Al2O3. Linked with the formation of crystalline phases is an increases in hardness from 10 up to 22 GPa. In addition, a pronounced increase in residual stresses of the layers can be observed. Pulsed magnetron sputtering permits to coat substrate materials with hard, crystalline aluminum oxide that could not be treated up to now because the substrate temperatures were too high.
71 citations