Ozone jet generator as an oxidizing reagent source for preparation of superconducting oxide thin film

Abstract

An ozone jet generator to supply precisely controlled ozone flux to a specimen was constructed with the particular aim of its application for the preparation of superconducting oxide thin films by an MBE (molecular beam epitaxy) method. The ozone jet is supplied to the thin film growth chamber by evaporating the liquid (or solid) ozone accumulated in the ozone vessel of the generator. The necessary condensed ozone is produced from the ozone-oxygen mixture gas generated by a commercial ozonizer. The ozone flux can be changed by adjusting the temperature of the ozone vessel (i.e., the temperature of liquid ozone). Precise pressure and temperature control of the ozone vessel in liquefying ozone makes it possible to minimize dissolution of diatomic oxygen in the liquid ozone. As a result, the ozone jet generated from the liquid ozone possesses high purity. The precise temperature control also enables a very stable supply of the ozone jet, with a stability of less than 2.5% over 1.5 h. For the experimental condition of liquefying ozone at 95 K and 800 Pa, and evaporating at 85 K, an ozone jet with an ozone flux of 1×1016 molecules/s and an ozone concentration of higher than 70% was obtained in the test vacuum chamber installed with this ozone jet generator. It was also confirmed by XPS spectra of Cu after oxide film formation that the ozone jet possesses a very high reactivity.

Initial Oxidation of Si(100)2×1 by Ozone: Transition of Growth Kinetics from Adsorption to Ultrathin Film Growth

“…In this Letter, we report a higher reactivity of ozone with its concentration >80% 4) as an alternative oxidant than molecular oxygen to synthesize an ultrathin silicon oxide film by investigating its growth kinetics by Si 2p X-ray photoelectron spectroscopy (XPS) and by comparing it with that of oxygen. A significant feature is presented for growth kinetics modes of oxide films by ozone on Si(100)2×1 with their thickness above and below 0.6 nm and on a substrate heated above 550 • C or below 500 • C. Here, we show a clear transition of the initial oxide growth kinetics due to ozone from the adsorption mode to the ultrathin oxide growth mode.…”

“…Next, we exposed this clean Si(100)2×1 at a fixed temperature to highly concentrated ozone gas at reduced pressure in the UHV chamber. This ozone gas was supplied using an ozone jet generator system described in detail elsewhere: 4) The system consists of a conventional ozonizer by electric discharge which produces about 5 at% ozone/oxygen mixture gas and a cold vessel which isolates ozone from oxygen in the mixture gas by liquefying only ozone at 90 K and evacuating oxygen. Finally, saturated ozone vapor in this cold vessel XPS peaks due to an ultrathin oxide film growth in the presence of ozone.…”

XPS analysis of ultrathin SiO2 film growth on Si by ozone

“…The measurement of electric properties of the film may reveal the existence of such layers; this is left for further study. Because the XPS spectra were stable for all samples, we investigated the oxide film growth by ozone using Eqn (2). Figure 3 shows the dependence of the oxide film thickness, estimated using Eqn (2), on the time of exposure to the ozone gas at a sample temperature of ¾200°C ( ž ).…”

“…Using a high-purity (>80%) ozone jet supplied by an ozone generator, 2,3 we examined the formation of an ultrathin SiO 2 film on Si(111) and Si(100) substrates. This examination revealed several superior features of ozone in the oxidation of Si.…”

Evaluation of Outermost Surface Temperature of Silicon Substrates during UV-Excited Ozone Oxidation at Low Temperature

“…The ~100% ozone used in these experiments was supplied by a pure ozone generator (Type: MPOGSM1C1; Meidensha Corp., Japan). [2][3][4][5] The use of pure ozone reduces the activation energy for Si oxidation from 0.81 eV for O2 to 0.34 eV, resulting in a reaction temperature as low as 410 C. 6 Below 410 C, the Si oxidation rate decreases abruptly owing to the lack of atomic oxygen in the ground state, O( 3 P), which is produced by the thermal decomposition of ozone. The reactivity of ozone can be further enhanced by photoexcitation using ultraviolet (UV) light, which illuminates the Hartley bands (200 to 300 nm) to produce atomic oxygen in an excited state, O( 1 D).…”