Thermal Oxidation of Porous Silicon:  Study on Reaction Kinetics

Abstract

Porous silicon (PS) samples obtained by dark etching of p + -type silicon wafers are oxidized in dry air, at various temperatures from 200 °C up to 800 °C for 1-20 h durations, to determine the kinetics of the reaction. The extent of oxidation calculated from mass gains is plotted as a function of oxidation time and temperature. By fitting the general reaction kinetic solutions of different-order reactions, one finds that the function valid for first-order kinetics gives the best matches. From the obtained reaction rates, the pre-exponential factors and activation energies of the oxidation process are determined using Arrhenius plots. It is found that, depending on the temperature range of the oxidation process, either one or two chemical reactions take place. At lower temperatures (200-400 °C), a reaction with an activation energy E a,1 ≈ 7 kJ‚mol -1 and a pre-exponential factor A 1 ≈ 0.2 h -1 dominates. When the temperature is increased (400-800 °C), a second reaction starts, showing E a,2 ≈ 50 kJ‚mol -1 and A 2 ≈ 100 h -1 .

Effects of thermal oxidation on the photoluminescence properties of porous silicon

“…4. Similar results are also observed by several authors [22,23]. The high reactivity of PSi for oxidation may arise from peculiar internal strain induced in nanostructured substances [26,27].…”

“…(1) for PSi (solid squares) and bulk Si samples (solid circles) as a function of the annealing temperature T. We can see the clear difference of the SiO 2 thickness between for the PSi and bulk Si samples. In the literature [22,23], it is reported that the oxidation of PSi gives two different activation energies. In our case, since the SiO 2 thickness on the PSi surface increases with two steps (Fig.…”

Silicon Porosification: State of the Art

“…110,[476][477][478] Many oxidation methods exist, such as aging in ambient, 479 exposure to water vapor, [480][481][482] anodic oxidation in a non-fluoride electrolyte, 142,179,[483][484][485] 479 and thermal oxidation in wet and dry O 2 fluxes, 189,381,[488][489][490][491] including rapid thermal oxidation. 477 A data review regarding a wide range of oxidation treatments (e.g., thermal treatments, electrochemical and chemical oxidation, pthotochemical oxidation, etc.)…”

“…110 Since porous Si has a very large surface-to-volume ratio, it is being oxidized already at 750 to 800 • C (see Figure 87). For example, Pap et al 490 have shown that already at T = 800 • C after 10 h oxidation the whole PSi structure with wall thickness ∼30 nm was oxidized.…”

Advances in Nanophotonic Sensing Technologies During Three International Label-Free Lab-On-Chip Projects

“…Several (110) PSi membranes of various thicknesses were fabricated and transferred to a glass substrate in which a 3-to 4-mm circular hole was made in order to characterize the birefringence as a function of optical path. Before measuring the birefringence of the fabricated samples, a thermal oxidation at 200°C for 12 h was carried out in order to stabilize pore surfaces during the measurements [46]. The optical anisotropy of fabricated samples was then determined by analyzing the state of polarization of the light transmitted through them [47].…”