Atomic Layer Chemical Vapor Deposition of TiO[sub 2] Low Temperature Epitaxy of Rutile and Anatase

Abstract

This study demonstrates that atomic layer chemical vapor deposition is an excellent technique for growing epitaxial TiO 2 thin films at low temperatures. Using TiI 4 and H 2 O 2 as precursors, both the rutile and anatase phases could be deposited. Anatase is invariably obtained at lower deposition temperatures, but the temperature of the anatase/rutile phase boundary is affected by the substrate material chosen. Phase-pure rutile was obtained down to 275ЊC on a-Al 2 O 3 (0 1 2), while phase-pure anatase was obtained up to 375ЊC on MgO (0 0 1). The rutile phase was found to grow epitaxially on both ␣-Al 2 O 3 (0 1 2) and ␣-Al 2 O 3 (0 0 1) substrates with the in-plane orientational relationships, and [0 1 0] rutile //[1 0 0] ␣-Al 2 O3 , respectively. The anatase phase was found to grow epitaxially on MgO (0 0 1) with the in-plane orientational relationships [0 1 0] anatase //[0 1 0] MgO and [0 0 1] anatase //[1 0 0] MgO . The scan X-ray diffraction measurements verified that epitaxy was still obtained at a deposition temperature of 375ЊC. This deposition temperature is considerable lower than those commonly applied to realize heteroepitaxy of titanium oxide films.

Atomic Layer Deposition of Epitaxial and Polycrystalline SnO2 Films from the SnI4/O2 Precursor Combination

“…The interplanar angles between these planes and the (101) plane are all different, and only one peak will be observed in the j-scan. The appearance of a peak in both j-scans at the same j angle suggests that the b axis of the SnO 2 film [54] This is to be expected since both phases crystallize in the rutile-type structure with similar lattice dimensions. A much less intense peak can also be seen in the j-scan for the 301 reflection of the SnO 2 film, (Fig.…”

“…A possible explanation might be that, for this orientation, the oxygen atoms inside the unit cells of the Al 2 O 3 substrate and the SnO 2 film are not superimposed at the interface. [54] To further analyze the SnO 2 film quality and thickness, X-ray reflectivity curves were measured at low angles for the films grown on a-Al 2 O 3 (012). As can be seen in Figure 5, a typical declining pattern of thickness fringes could be observed throughout the investigated temperature region, indicating the good quality of the SnO 2 films in respect of a well-defined thickness over the whole substrate area, the sharpness of the interface, and a low surface roughness.…”

Atomic Layer Deposition of BaTiO3 Thin Films—Effect of Barium Hydroxide Formation

“…[12] Titanium iodide TiI 4 has also been used in ALD of TiO 2 . [13] Theoretically, removing iodine from the film should be easier than removing chlorine and the use of TiI 4 may thus warrant future experiments. Titanium alkoxides Ti(O i Pr) 4 , [14] Ti(OEt) 4 , [15] and Ti(OMe) 4 [16] have been used in the ALD of TiO 2 with H 2 O as the oxygen source.…”

Radical Enhanced Atomic Layer Deposition of Titanium Dioxide

“…[16,17] The metal precursors have been either halides or alkoxides; TiCl 4 , [2,[18][19][20][21][22][23][24][25][26][27][28][29] TiI 4 , [30][31][32][33][34] Ti(OCH(CH 3 ) 2 ) 4 , [35][36][37][38][39] Ti(OC 2 H 5 ) 4 , [40][41][42][43] and Ti(OCH 3 ) 4 . [12] The oxygen precursor has most commonly been water, but hydrogen peroxide, [31,32,37] molecular oxygen, [33,34] ozone, [38] and nitrogen/ oxygen plasma [39] have also been used. Both titanium precursor groups have their limitations; halides are considered corrosive and alkoxides start to self-decompose at around 300°C, losing the self-controlling deposition characteristic of ALD.…”