Wet oxidation of AlAsSb alloys catalyzed by methanol (original) (raw)
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Lateral oxidation kinetics of AlAsSb and related alloys lattice matched to InP
Journal of Applied Physics, 2001
The lateral oxidation kinetics of AlAs0.56Sb0.44 on InP substrates have been investigated to understand the antimony segregation process during oxidation. Oxidation layers were grown between GaAsSb buffer and cap layers on InP substrates by molecular beam epitaxy. Oxidation temperatures between 325 and 500 °C were investigated for AlAsSb layer thicknesses between 100 and 2000 Å. At low oxidation temperatures (Tox⩽400 °C), the process is reaction limited with a linear dependence of oxidation depth on time. At intermediate oxidation temperatures (400<Tox<450 °C), the oxidation process becomes diffusion limited. At high oxidation temperatures, the oxidation process is termed self-limiting since at 500 °C the process stops entirely after oxidation times on the order of 5 min and distances of 40 μm. It is shown that the antimony float layer lags the oxidation front by a temperature-dependent distance, which suggests that the antimony may change the structure of the oxide at the fro...
Surface Sci, 1997
The initial stages of oxidation of AlAs(001) (using H20 and 02 as the oxidants) have been investigated using Auger electron spectroscopy, temperature-programmed desorption and high-resolution electron energy-loss spectroscopy. We have found that 02 has a low probability of dissociative chemisorption on AlAs(001), rendering it ineffective as an oxidant of AlAs under ultrahigh vacuum conditions. In contrast, water, by virtue of overlapping desorption and dissociation temperatures, is able to dissociate readily on the AlAs(001) surface. Water dissociation within the subsurface is observed, indicative of A1 oxide/hydroxide formation. Arsenic is found to be depleted within the oxide film by arsine desorption, a process which is shown to enhance the oxide growth. By identifying the various reaction steps which occur (with annealing) after the low-temperature adsorption of water on AlAs(001), we are able to propose a mechanism for the initial stages of wet AlAs oxidation. Briefly, the initial H20 adsorption occurs molecularly at 100 K. Upon annealing to 160 K, both desorption and dissociation from the molecularly adsorbed state occurs. Both AI O and AI-OH, as well as As H, are produced by the dissociation of H20 (via partial and total dehydrogenation, respectively). The AI OH species disproportionate and/or rehydrogenate between 400 and 650 K resulting in H20 desorption. The remaining A1 OH dehydrogenate above 550 K to produce AI-O and desorbing hydrogen. The As H species desorb as AsH 3 in a broad peak at 500 550 K with an additional low-temperature desorption peak appearing below 200 K after higher H20 exposures.
Initial oxidation of ultrathin antimony films on Au(111) and of polycrystalline antimony
Physical review. B, Condensed matter, 1994
It has been shown previously that antimony evaporated onto a Au(111) surface grows in a layer-bylayer mode. The present work compares the initial, fast-oxidation stage of these films with that on bulk polycrystalline antimony. Measurements were carried out in an ultrahigh-vacuum environment using Auger electron spectroscopy, low-energy electron diffraction, electron-energy-loss spectroscopy, and work-function change measurements. At 300 K and for oxygen pressures between 1X10 ' and 2X10 ' Torr, oxidation follows first-order Langmuir kinetics, with an initial sticking probability of about 10 Oxidation essentially saturates by 10' L (1 L=10 Torr s). A layer of oxide about 8.5 A thick is formed in this initial stage, both for Sb films and for bulk antimony. An initial antimony film on Au(111) of about 1.7 monolayers, or 1.6X10"atoms/cm, is required to complete this oxide layer, for saturation oxidation. The chemical composition of the oxidized films and the oxidized surface of bulk antimony is Sb203. These results are compared with earlier work on Pb, Bi, and Sn. lowed the same cleaning procedure as described elsewhere. The oxide film was removed by argon bombardment at 830 K. The polycrystalline Sb (99.9999% pure, Johnson-Matthey) was mechanically cut and polished, and then cleaned by argon bombardment while heated at 600 K. The surfaces were monitored by AES before every experiment and no contamination was found. Sb
Comparative study of Al() oxidation with O3 and O2
Surface Science, 2002
The interaction of O 3 and O 2 with the Al(1 1 1) surface was investigated over the surface temperature range of 90-600 K using X-ray photoelectron spectroscopy. The oxidation of aluminum at 300 K with ozone gas was found to proceed with an 8.5 times higher initial sticking coefficient compared to oxygen, reaching a 2-2.3 times higher saturation oxide layer thickness of approximately 20 A A. The enhanced oxidation rate observed at lower temperatures indicates that trapping of the molecular ozone species into a shallow precursor well occurs in the course of Al(1 1 1) oxidation. The difference in activation energy for O 3 adsorption and desorption to and from this state is ðE d À E a Þ ¼ 7 AE 2 meV. Subsequent dissociation of the ozone molecules on the surface occurs possibly through the production of chemically active atomic oxygen. O 3 -induced oxidation occurs by means of a mechanism involving preferential direct formation of Al 2 O 3 clusters. In contrast, for oxidation with molecular oxygen, the formation of a chemisorbed O phase, followed by its slow transformation into oxide clusters, is observed. The higher electron affinity of the ozone molecule compared to oxygen is proposed to also enhance the kinetics of Al oxidation at the later stages of the oxide layer growth (film thickness d P 2-3 ML), by causing enhanced tunneling of electrons from Al metal to the adsorbed O 3 . Tunneling electrons create an electrostatic potential across the growing film, stimulating ion-diffusion and, thus, oxide film growth.
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2013
In-situ monochromatic x-ray photoelectron spectroscopy, low energy electron diffraction, ion scattering spectroscopy, and transmission electron microscopy are used to examine the GaSb(100) surfaces grown by molecular beam epitaxy after thermal desorption of a protective As or Sb layer and subsequent atomic layer deposition (ALD) of Al 2 O 3. An antimony protective layer is found to be more favorable compared to an arsenic capping layer as it prevents As alloys from forming with the GaSb substrate. The evolution of oxide free GaSb/Al 2 O 3 interface is investigated by "half-cycle" ALD reactions of trimethyl aluminum and deionized water. V
MRS Proceedings, 1999
ABSTRACTWet oxidation of high-Al-content AIGaAs semiconductor layers in vertical cavity surface emitting lasers (VCSELs) has produced devices with record low threshold currents and voltages and with wall-plug efficiencies greater than 50%. Wet oxidation of buried AlGaAs layers has been employed to reduce the problems associated with substrate current leakage in GaAs-on-insulator (GOL) MESFETs. Wet oxidation has also been considered as a route to the long-sought goal of a III-V MIS technology. To continue improving device designs for even higher performance and to establish a truly manufacturable technology based on wet oxidation, the effect of oxidation of a given layer on the properties of the entire device structure must be understood. The oxidation of a given layer can strongly affect the electrical and chemical properties of adjacent layers. Many of these effects are derived from the production of large amounts of elemental As during the oxidation reaction, the resultant generat...
X-ray photoemission spectroscopy study of surface oxidation of Nb/Al overlayer structures
Applied Physics Letters, 1982
We identify and characterize the chemical nature of the oxide formed by the air oxidation of thin Al overlayers on Nb. Take-off angle experiments were performed to determine the sequential layer configuration. The thickness of the oxide did not exceed 20 A, regardless of the thickness of the metallic Al originally deposited. Grain-boundary diffusion is suggested as a mechanism for the removal of most of the excess metallic AI. The observation of a small amount of residual metallic Al near the interface is in accord with Miedema's theory of surface segregation which indicates that Al will segregate to the surface of a Nb-AI alloy. An Al overlayer as thin as 9.5 A is sufficient to protect the underlying Nb film from oxidation and to form an effective tunneljunction barrier.
Surface Science, 1989
Ultraviolet irradiation of vitreous As2S 3 surfaces in the presence of oxygen results in photoinduced changes in chemical composition; these are known to be accompanied by very large changes in sticking probability for Group liB metal deposition. It is shown that this effect is associated with selective surface oxidation of the arsenic component and does not involve surface depletion of either arsenic or sulphur. A mechanism for this process is proposed.
Oxidation of Metals, 2004
The internal oxidation of a two-phase at.% Se alloy in pure oxygen was studied at 750, 800 and 830 • C. The alloy is composed of a dilute solid solution of selenium in silver) and Ag 2 Se intermetallic particles. The internal oxidation of this alloy proceeds through gradual in-situ oxidation of the Ag 2 Se particles as well as through diffusive internal oxidation of selenium from solid solution. Gradual in-situ internal oxidation of Ag 2 Se particles reflects itself in the appearance of two internal-oxidation fronts, inner and outer, marking the beginning and end of the in-situ oxidation of Ag 2 Se particles. The oxide phase formed during in-situ oxidation is the molten double oxide, Ag 2 SeO 3 . A theoretical treatment of the phase relationships in a hypothetical Ag-Ag 2 Se-Ag 2 SeO 3 ternary phase diagram is presented to assist the explanation of the mechanism of in-situ oxidation. The kinetics of oxidation are presented in Part II.
Wet oxidation of thin AlAs in cylindrical composite of GaAs/AlAs/GaAs
2011
Lateral wet oxidation in a cylindrical composite, GaAs/AlAs/GaAs, with varying thickness of the AlAs layer has been investigated. The oxidation depth in AlAs was measured in the temperature range of 400-480 • C. At given temperature and time, the depth increases with the increase in thickness. The thickness effect was successfully interpreted based on the kinetic model of boundary layer diffusion. The results are consistent with the findings from early studies on samples of square and rectangular cross-sections with the same activation energy of the thermal process.