Titanium dioxide thin-film growth on silicon (111) by chemical vapor deposition of titanium(IV) isopropoxide

Abstract

The initial stages of TiO2 growth on Si(111) under ultra-high vacuum conditions is studied using core level photoelectron spectroscopy, x-ray absorption spectroscopy, and scanning tunneling microscopy. The TiO2 film was formed by means of chemical vapor deposition of titanium(IV) isopropoxide at a sample temperature of 500 °C. The thickness and composition of the amorphous interface layer and its subsequent transition to crystalline anatase TiO2 are discussed. Three different stages are identified: In the initial stage (film thickness <10 Å), the oxygen atoms are coordinated mainly to Si atoms giving rise to Ti atoms with oxidation states lower than 4+. At this stage, a small amount of carbon (0.15 ML) is observed. The next stage (<25 Å) is best described as an amorphous TiSixOy compound in which the oxidation state of Ti is 4+ and the x and y values vary monotonically with the film thickness, from 2 to 0 and 4 to 2, respectively. Finally (>30 Å) a stoichiometric TiO2 layer starts to form. The TiO2 phase is anatase and the layer consists of particles ∼10 nm wide.

Initial stages of TiO2 thin films MOCVD growth studied by in situ surface analyses

“…1). The presence of an interfacial silicon oxide for TiO 2 or other metal oxide thin-film growth on bare silicon substrate by CVD techniques was still reported by other authors [3,14]. The presence of the oxidation states Si 2+ , Si 3+ in addition to Si 4+ reveals nonstoichiometric silicon oxide.…”

“…It should be noticed that the deposit global oxidation state increases with deposit thickness. Consequently, the formation of a growing and more and more oxidized interfacial TiSi x O y layer before stoichiometric TiO 2 growth may be inferred and could be compared to the literature results [3]. The presence of two components in the O 1 s line is evidenced in Fig.…”

“…Chemical surface analysis using electron spectroscopies is thus helpful to achieve this. Even though MOCVD could be performed from atmospheric pressure (APCVD) [1] to UHV pressure [2,3], to the best of our knowledge no studies were carried out coupling a MOCVD deposition reactor to surface spectroscopic analysis UHV chambers. As TiO 2 /Si, TiO 2 /SiO 2 or TiO 2 /SiO 2 /Si systems are widely used and still investigated in many high technological fields due to their outstanding properties [1,[4][5][6], in the present work we will describe preliminary results on the first stages of TiO 2 thin-film MOCVD growth on Si (1 0 0) performed in an original experimental set-up.…”

Interfacial reaction during MOCVD growth revealed by in situ ARXPS

“…The calculation model for a single layer presented above has been applied at each layer independently, making the assumption that the intensity ratio of the interfacial layer is not influenced by the layer above (model c in Table 1). From previous works, 3,7 it can be supposed that silicon oxide is present only at the interface between the silicon substrate and TiO 2 . As noted in Table 1, for this interlayer, we consider the system SiO x /Si by the analysis of the corresponding Si xC 2p/Si 0 2p ratio.…”

“…3,7 Hence, chemical species mixing should be also considered. This mixing can take place either in the interlayer or in the upper layer.…”