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␣-Fe 2 O 3 thin films have been deposited on Si͑100͒ substrates using n-butylferrocene and oxygen in a low-pressure metallorganic chemical vapor deposition reactor. The iron precursor is liquid at room temperature having a high enough vapor pressure; its thermogravimetric analysis shows that it undergoes clean evaporation without decomposition. The growth rates were studied in the temperature range of 400-600°C. The resulting thin films were characterized for structure and morphology using X-ray diffraction and scanning electron microscopy. Their composition was analyzed using energy-dispersive X-ray spectroscopy, and chemical bonding states were probed using X-ray photoelectron spectroscopy. Films deposited at 450°C were mostly noncrystalline and had carbon contamination. Films deposited at higher temperatures were crystalline ␣-Fe 2 O 3 .

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Isolated solid-state atomic defects with telecom optical transitions are ideal quantum photon emitters and spin qubits for applications in long-distance quantum communication networks. Prototypical telecom defects, such as erbium, suffer from poor photon emission rates, requiring photonic enhancement using resonant optical cavities. Moreover, many of the traditional hosts for erbium ions are not amenable to direct incorporation with existing integrated photonics platforms, limiting scalable fabrication of qubit-based devices. Here, we present a scalable approach toward CMOS-compatible telecom qubits by using erbium-doped titanium dioxide thin films grown atop silicon-oninsulator substrates. From this heterostructure, we have fabricated onedimensional photonic crystal cavities demonstrating quality factors in excess of 5 × 10 4 and corresponding Purcell-enhanced optical emission rates of the erbium ensembles in excess of 200. This easily fabricated materials platform represents an important step toward realizing telecom quantum memories in a scalable qubit architecture compatible with mature silicon technologies.

Tetrakis ͑diethylamino͒ hafnium ͑TDEAH͒, tetrakis ͑diethylamino͒ titanium ͑TDEAT͒, and H 2 O were used for the atomic layer deposition ͑ALD͒ of HfO 2 , TiO 2 , and Hf x Ti 1−x O 2 films on silicon substrates. The ALD temperature windows were found to be 175-250°C for HfO 2 ͑0.12 nm/cycle͒ and 150-250°C for TiO 2 ͑ ϳ0.06 nm/cycle͒. The 175-250°C overlap region is ideal for the ALD of the Hf x Ti 1−x O 2 films. Different compositions of Hf x Ti 1−x O 2 were obtained by varying the ͓TDEAH/H 2 O͔/͓TDEAT/H 2 O͔ cycle ratios, and excellent tunability of film composition was found using X-ray photoelectron spectroscopy ͑XPS͒. The Hf x Ti 1−x O 2 deposition rate was found to be the superposition of the two individual growth rates. Both as-deposited and postdeposition annealed films were studied with XPS, phase shift interferometry, and grazing incidence X-ray diffraction. As-deposited HfO 2 and TiO 2 films were found to be amorphous, and they began to crystallize after annealing at 600°C in the monoclinic phase ͑HfO 2 ͒ and in weak anatase phase ͑TiO 2 ͒. The Hf x Ti 1−x O 2 films remained amorphous after annealing up to about 1000°C in N 2 for 5 min.Structural and interfacial studies of ultrathin, high dielectric constant ͑͒ films during high temperature fabrication processes are critical to the continuous scaling of microelectronic devices. In particular, these materials are of great importance for the gate insulator of metal oxide semiconductor field effect transistors and the capacitor dielectric of dynamic random access memories. 1,2 So far, many candidate materials such as have been studied for the replacement of SiO 2 . 3 From all these materials, HfO 2 and TiO 2 seem to be promising candidates due to their favorable properties. HfO 2 is known to have relatively good thermal stability and compatibility with the Si substrate, and it has a dielectric constant of 15-30 with a large bandgap ͑5.7 eV͒. 4-6 TiO 2 is even more favorable in terms of its dielectric constant which is 80 or higher; 7 however, it has a rather small bandgap ͑3.1 eV͒, 8 which could result in more leakage current than that of HfO 2 . The reported crystallization temperature of each of these two materials has been reported to be as low as ϳ550°C. 9,10The earliest atomic layer deposition ͑ALD͒ of HfO 2 from tetrakis ͑diethylamino͒ hafnium ͑TDEAH͒ and H 2 O was published by Deshpande et al. with a growth rate of ϳ0.13 nm/cycle at 300°C. 11 Titanium tetrachloride ͑TiCl 4 ͒ and titanium isopropoxide ͑TTIP͒ have typically been used as metal precursors in the ALD of TiO 2 films, with water being the oxidant. 12-16 Growth rates of 0.03 nm/cycle or lower in these systems were reported. Our earlier ALD studies with other homoleptic metal precursors having the diethylamino ligand, such as TDEAH and tris ͑diethylamino͒ aluminum, have resulted in broad ALD temperature windows and rather high growth rates. 9,11,17,18 Such results have prompted interest in examining the suitability of tetrakis ͑diethylamino͒ titanium ͑TDEAT͒ as a precursor for the ALD of TiO 2 ...

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