Colloidal, monodisperse, highly crystalline ITO nanoparticles with various particle sizes and tin contents were prepared by a one-pot thermal decomposition of tin and indium precursors in oleylamine. The PL emission maxima become blue-shifted as the particle size decreases and the tin content increases.

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An atomic layer deposition (ALD) process for SrTiO 3 (STO) thin film growth was developed using a newly designed and synthesized heteroleptic Sr-precursor, {Sr(demamp)(tmhd)} 2 (demampH = 1-{[2-(dimethylamino)ethyl](methyl)amino}-2-methylpropan-2-ol, tmhdH = 2,2,6,6-tetramethyl-3,5-heptanedione), which offered an intermediate reactivity toward oxygen between Sr(tmhd) 2 and Sr( i Pr 3 Cp) 2 . Because of the appropriate reactivity of {Sr(demamp)(tmhd)} 2 toward oxygen, the abnormal initial growth behavior (due to interaction between the Sr-precursor and active oxygen contained in the underlying oxidized Ru layer) became negligible during the growth of the SrO and STO films on the Ru electrode, which allowed the growth of the SrO and STO films to be highly controllable with a moderate growth rate. Using Ti(CpMe 5 )(OMe) 3 as the Ti-precursor and O 3 as the oxygen source in the TiO 2 ALD subcycle, the ALD process of the STO film revealed a growth rate of 0.05 nm/cycle and ∼85% of step coverage in terms of the thickness and cation composition on a capacitor hole structure with an aspect ratio of 10 (opening diameter of 100 nm and depth of 1 μm). The minimum achievable equivalent oxide thickness (t ox ) with a low leakage current (<10 −7 A/cm 2 at 0.8 V) was limited to 0.46 nm. The damage effect on the underlying Ru electrode by the prolonged ALD process time appears to affect the limited scalability of t ox . ■ INTRODUCTIONSrTiO 3 (STO) has been considered to be a promising candidate for a dielectric layer in the next-generation dynamic random access memory (DRAM) capacitors because of its high permittivity (∼300 in bulk material) compared with that of other dielectric materials, such as HfO 2 and ZrO 2 . Many studies have reported a high dielectric constant of >100 for metal− insulator−metal (MIM) capacitors that contain an STO insulator, in which the insulators are thinner than 20 nm. 1−6 Considering the extremely tiny three-dimensional (3D) structure of the DRAM capacitors, 7 atomic layer deposition (ALD) appears to be the only feasible thin film growth technique that can fulfill the stringent requirements of thickness and composition step coverage in the DRAM capacitors. Despite the acute requirement for a suitable ALD process of the STO films, the development has been hindered for two main reasons: first, the lack of a suitable Sr-precursor for feasible STO ALD, although that for Ti is abundant; second, because of the low temperature of the ALD, ensuring a suitable crystalline quality of the STO film is challenging in general. Because such problems and possible solutions have already been extensively reviewed in previous reports from the authors' group, 3,7,8 more recent reports that are directly related to the present work are described in this section.The first viable report in this field was published by the Helsinki group in the late 1990s. Vehkamaki et al. deposited STO films with Sr( i Pr 3 Cp) 2 (Pr and Cp are propyl and cyclopentadienyl group, respectively) and Ti(O i Pr) 4 [TTIP] as Sr-and Ti-precursors,...

Low-temperature growth of InO films was demonstrated at 70-250 °C by plasma-enhanced atomic layer deposition (PEALD) using a newly synthesized liquid indium precursor, dimethyl(N-ethoxy-2,2-dimethylcarboxylicpropanamide)indium (MeIn(EDPA)), and O plasma for application to high-mobility thin film transistors. Self-limiting InO PEALD growth was observed with a saturated growth rate of approximately 0.053 nm/cycle in an ALD temperature window of 90-180 °C. As-deposited InO films showed negligible residual impurity, film densities as high as 6.64-7.16 g/cm, smooth surface morphology with a root-mean-square (RMS) roughness of approximately 0.2 nm, and semiconducting level carrier concentrations of 10-10 cm. Ultrathin InO channel-based thin film transistors (TFTs) were fabricated in a coplanar bottom gate structure, and their electrical performances were evaluated. Because of the excellent quality of InO films, superior electronic switching performances were achieved with high field effect mobilities of 28-30 and 16-19 cm/V·s in the linear and saturation regimes, respectively. Furthermore, the fabricated TFTs showed excellent gate control characteristics in terms of subthreshold swing, hysteresis, and on/off current ratio. The low-temperature PEALD process for high-quality InO films using the developed novel In precursor can be widely used in a variety of applications such as microelectronics, displays, energy devices, and sensors, especially at temperatures compatible with organic substrates.

The reaction of Ir4(CO)8(PMe3)4 with excess C60 in refluxing 1,2-dichlorobenzene, followed by treatment by CNR (R = CH2C6H5) at 70 degrees C, affords a fullerene-metal sandwich complex Ir4(CO)3(mu4-CH)(PMe3)2(mu-PMe2)(CNR)(mu-eta2,eta2-C60)(mu4-eta1,eta1,eta2,eta2-C60) (1), which exhibits an interesting structural feature of two metal atoms bridging the two C60 centers as well as the first example of a mu4-eta1,eta1,eta2,eta2-C60 bonding mode. Compound 1 has been characterized by NMR spectroscopy, elemental analysis, and X-ray diffraction study. A cyclic voltammetry study reveals strong electronic communication between the two C60 centers in 1, which is due to the presence of a wide channel of two metal centers between the two C60 cages for efficient electronic interaction.

Ruthenium (Ru) and ruthenium oxide (RuO 2 ) thin films were grown by atomic layer deposition (ALD) using a novel zerovalent (1,5-hexadiene)(1-isopropyl-4-methylbenzene)Ru complex and O 2 as the Ru precursor and oxidant, respectively. The self-limiting growth mode for the Ru and RuO 2 ALD processes was achieved while varying the Ru precursor and O 2 feeding time. Metallic Ru films were deposited at growth temperatures of 230−350°C, while the temperature window for the growth of the RuO 2 film was limited to <230°C. At 270°C, the growth per cycle (GPC) of Ru ALD was 0.076 nm/cycle, and the incubation times of Ru on SiO 2 and TiN substrates were considerably short (3 cycles on SiO 2 , negligible on TiN) compared to that of Ru ALD from a high-valent Ru precursor and O 2 . The resistivity of the Ru film was as low as 29−36 μΩ·cm at growth temperatures of 270−350°C. On the other hand, the RuO 2 film was grown at a low temperature of 200°C and showed a GPC of 0.15 nm/cycle with a resistivity of ∼270 μΩ·cm. In situ quadruple mass spectrometry analysis of the CO 2 byproduct revealed that the amount of subsurface oxygen extracted during the Ru pulse half-cycle affected the resultant film phase, either Ru or RuO 2 , which was strongly influenced by the growth temperature. ■ INTRODUCTIONThe growth of nanoscale ruthenium (Ru) and ruthenium oxide (RuO 2 ) thin films has been spotlighted due to their promising characteristics such as low resistivity (Ru ∼7 μΩ·cm, RuO 2 ∼30 μΩ·cm), excellent chemical and thermal stabilities, high work functions (Ru ∼4.7 eV, RuO 2 ∼5.1 eV), and catalytic functionality. 1−15 These properties have enabled Ru-based thin films to be employed for energy device applications as a catalyst, in microelectronics as an electrode for dynamic random access memory (DRAM) capacitors, and as a seed layer for Cu electroplating. 2−7 Although a variety of deposition techniques for fabricating Ru and RuO 2 thin films have been used such as sputtering, pulse laser deposition, and chemical vapor deposition, atomic layer deposition (ALD) is the most appropriate method to grow uniform and conformal film over a 3-dimensional substrate with very precise composition/thickness controllability in nanotechnology applications. For Ru ALD, meanwhile, the choice of the Ru precursor is very important because not only the growth characteristics but also the film properties are highly affected by the Ru precursor used. For example, Ru(thd) 3 (thd = 2,2,6,6-tetramethyl-3,5-heptanedionate), Ru-(Cp) 2 (Cp = cyclopentadienyl), Ru(EtCp) 2 (EtCp = ethylcyclopentadienyl), and 2,4-(dimethylpentadienyl)-(ethylcyclopentadienyl)Ru are the most widely utilized Ru precursors in conjunction with O 2 as an oxidant. 8−12 Ru ALD using these precursors, however, showed extremely retarded nucleation and consequently resulted in long incubation cycles (e.g., >300 cycles on SiO 2 and 500 cycles on TiN when Ru(thd) 3 and O 2 were employed) at temperatures of 275−400°C . This poor nucleation behavior hinders the practical use of the Ru precursors listed ...

The quadruple-level cell technology is demonstrated in an Au/Al O /HfO /TiN resistance switching memory device using the industry-standard incremental step pulse programming (ISPP) and error checking/correction (ECC) methods. With the highly optimistic properties of the tested device, such as self-compliance and gradual set-switching behaviors, the device shows 6σ reliability up to 16 states with a state current gap value of 400 nA for the total allowable programmed current range from 2 to 11 µA. It is demonstrated that the conventional ISPP/ECC can be applied to such resistance switching memory, which may greatly contribute to the commercialization of the device, especially competitively with NAND flash. A relatively minor improvement in the material and circuitry may enable even a five-bits-per-cell technology, which can hardly be imagined in NAND flash, whose state-of-the-art multiple-cell technology is only at three-level (eight states) to this day.

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